Aeroovee to Rotax mount conversion?

ArchiveBot · August 10, 2022, 5:00am

Aeroovee to Rotax mount conversion???

Posted: Wed Aug 10, 2022 10:27 pm

by xeriotti

Hi everyone, I have an almost complete Waiex, just needs an engine to be mounted, instrument panel assembly and finish interior.
My plane has the aerovee engine mount from the factory kit but i recently purchased a Rotax 912ULS 100hp engine and i think it will be a better choice for my missions. And a better choice commercially (I live in Argentina, Its Rotax or nothing over here)
I will attempt to fabricate an adapter to couple the Aerovee mount to the Rotax 912. I know it can be done… It would be really helpful for me to see photos, hear comments and ideas, or any information that you guys may consider important.

Thanks a lot, i will post pics of my conversion as soon as i start working on it.. But im still on the research phase

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Aug 11, 2022 7:29 am

by GordonTurner

Nice looking plane. Here’s what appears to be the easy way…convert the mount you have with this kit from Sonex:

https://www.sonexaircraft.com/eshop/car … ory_id=452

They also sell completely new engine mounts for the Rotax if you want a more elegant solution.

Good luck, looks like you’ll be flying soon!!!

Best, Gordon

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Aug 11, 2022 11:29 am

by 13brv3

The adapter concept is certainly appealing, but I’m sure no one would consider it ideal. This thread shows one adapter, but I never saw any followup about how it worked, or if it was ever even flown. In the final version, it didn’t looks too bad though.
http://www.sonexbuilders.net/viewtopic.php?f=60&t=579

I was in the same situation with a Onex that already had a mount attached. My first thought was an adapter, but I ended up scratch building a new mount using the Rotax ring mount rather than the bed mount. Of course in my case, the engine mount has no landing gear, so it made the mount MUCH simpler.

Getting one from Sonex won’t be cheap, but it will likely be the easiest solution. They’ve had some teething pains with those mounts, but now that they actually have their own Rotax installation, I’d expect any remaining issue to be sorted out fairly quickly.

One other option might be something in-between. Modify the existing mount by cutting off the tubes that go to the Aerovee, and replacing them with tubes that go to the Rotax ring mount locations.

In my opinion, you absolutely made a great decision to use the 912ULS. I wish mine was a 100 HP rather than 80, but I had the engine already, and it’s actually doing quite well.

Cheers,
Rusty

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Aug 12, 2022 6:15 am

by Skippydiesel

My yet to fly Sonex Legacy (hope to get her of the ground within the month) is fitted with a Rotax 912 ULS and mounted using the Sonex : Rotax adapter.
The adapter looks great but was I disappointed in the fit.
Considerable “mucking about” was required, using home turned interference fit plugs, that were then drilled to suit the factory supplied engine frame - where is the QA?

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Aug 12, 2022 11:09 pm

by xeriotti

Thanks guys for the information… I already read everything about Sonex+Rotax easily available… Buying something from abroad is completely out of the table… I live in Argentina. We are having a hard time with politics and economy sucks (The last 70 years XD) So if its going to fly…Ill have to do it with my own hands

My engine arrives next week. If theres any way to make an aerovee/homemade ringmount coupling possible ill go that way… The bed mount is also tempting, but I think the ring is stronger.

The other option could be leaving the landing gear part of the mount on… cutting the non-landing-gear part…and starting from there. Ive done similar stuff before. Im a bit anxious, want to find the solucion and fly that baby asap!!!

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Aug 13, 2022 3:56 am

by Skippydiesel

I don’t think it would be very hard to fabricate your own copy of the Sonex : Rotax bed mount - its not much more than 4 pieces of angle aluminium. Finding the right gauge/thickness might be a problem.

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Aug 13, 2022 11:59 am

by Kai

The exercise of combining the Rotax 912 ULS to an already existing Sonex mount, has been successfully carried out several times. This one is manufactured by someone really in the know Down Under, and combines the 912 without the Rotax ring mount to an Aerovee engine truss. Alas, no drawings available, it was a trial and error project.

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Aug 13, 2022 12:01 pm

by Kai

The installed engine in the airframe described above looked like this during a stage in the project.

Bearing in mind that the Rotax prop torque is massive compared to that of a VW-1 aeroderivative, I would be hesitatant to use this truss as such without some reinforcenent between the upper longeron attachment brackets in the fuselage, as indicated in the construction drawings for the Sonex A + Jab33A truss: a continuous square steel stiffener tube.

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Aug 13, 2022 12:14 pm

by Kai

A different solution was selected for a Rotax 912 ULS with the standard Rotax ringmount installed, mating it up to a Sonex engine truss for the Jab 33A. Incidentally, the installed weight of the 912 is fairly close to that of the 33A. Hence final CG location should not be too far off.

On a side note, the Sonex mount for the 33A positions the stop flange for the isolators apprx 455,3 mm forward of the front fuselage bottom/firewall intersection (Sonex reference point). The Aerovee mount moves this plane 58,8 mm forward. The mount for the light Jab 22A moves it a total of 135 mm forward. Hence I speculate that using the 22A mount for this exercise could pose CG issues (with the R912 hanging out there, far up front), while the Aerovee mount would probably work, provided very careful design of the ring mount.

Anyhow, for this excercise 12mm thick steel (it could very well be aluminium provided you can find someone that actually manufactures 12mm 6061T6 or 7075T6) adapter plates were manufactured, which also provided for the use of the harder Sonex rubber isolators for the Jab.

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Aug 14, 2022 7:52 pm

by xeriotti

I think i preffer mounting the engine from behind rather than the bed mount (i confess the bed may be easier and im still not putting out ofthe table)

Picking up my engine next week I will keep you guys posted on that trip.

A set of 2" rubber isolators is on its way (Jeep Cabin isolators XD… I used them in other conversions, work great and costs 40X less than Rotax rubber mounts) . I will lathe turn the housings to mount them, that way i dont have to tighten them too much. they remain soft and absorb vibration efficiently and are also stronger and less prone to ovalizing because they are radially contained.

And it will be rigged something like this… (sorry bout that paint XD…will make a 3D when i have the actual measures if you guys are insterested)

Re: Aeroovee to Rotax mount conversion???

Posted: Wed Aug 17, 2022 1:34 pm

by xeriotti

Jeep Cabin dampers arrived

They aborb vibrations between the cabin and the chasis of this Argentinan made marbles… IKA Jeep , IKA Gladiator, Ika Baquueano, IKA estanciera… No too often, but you can still see people drive this things on the streets over here…

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Aug 18, 2022 3:21 am

by xeriotti

Now its lathe timeeeee

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Aug 18, 2022 9:02 am

by 13brv3

It will be interesting to see how those work out. I used Lycoming size Conical mounts for mine, and it’s a bit stiff. It would have been nice to use the ones Rotax sells for the ring, but their insanely expensive like most Rotax parts.

Rusty

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Aug 18, 2022 2:19 pm

by xeriotti

I have 4 of these…un-contained (i mean they seat pretty loose over flat washers)…on top a Rotax 503 with bed mount… And… Its stiff, but propper movement is allowed. I suppose that this same rubber components with the container and under some preload will do OK for the 912. Trial and error. 40X cheaper than a set of Rotax rubber mounts. (and i can find them in almost any car spare shop in Argentina)

I bought this set online… PRICE? 9 US Dollars…including shipping XD

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Aug 21, 2022 12:30 am

by xeriotti

Well… Today was a happy day! My dad wants to see that waiex airborne so bad!! he came with me to pick up the 912… We vesited some friends along the way…

It might sound dumb, but im really happy to have this chunk of metal here… It took a lot of effort, but its here!

Already turn the rubbermount supports… I have some work to do in other aircraft, before i start to work full time on my Waiex, it will be post and picture heavy if you guys dont bother

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Aug 25, 2022 5:00 am

by xeriotti

Moved the waiex from my warehouse to my workshop… Almost have to take down the tail XD

Leveled it out to start measuring here and there

Rigged a high tech engine temporary mount to figure things out

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Aug 26, 2022 6:22 am

by xeriotti

I have my “kindaringmount” figured out… Made it out of cardboard, then cleaned those traces to make it aestethically harmonic… And transcribed it to DXF format so i can lasercutit…

Ive seen someone making an adapter from a solid piece os 12mm steel… But i dont know…i calculated it to be around 3 kilograms for the plate only… Ill try to make something lighter without compromising strenght… (sounds easy XD)

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Aug 26, 2022 9:37 am

by 13brv3

Looks pretty interesting so far. I wonder if you could that from multiple layers. Maybe something like 1/8" steel on the front and back, with 1/2" aluminum sandwiched in the middle.

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Aug 26, 2022 2:45 pm

by xeriotti

13brv3 wrote:Looks pretty interesting so far. I wonder if you could that from multiple layers. Maybe something like 1/8" steel on the front and back, with 1/2" aluminum sandwiched in the middle.

I already have a steel lasercuted version to see if everything fits…

My idea es to use 2 plates “flat” and welding them together on the perimeter to form a “box” In this image the rubbermount housings arent displaye but they would also take part on that structure, everything tigwelded together.

Material and thickness of the plates to be calculated yet… But it looks really good and its easier for my with my tools than bending and notching steel tube…

Anyone knows how thick is a Rotax Ring Mount? or have data on the weight? Rotax 912 is light so i have no worries about adding a bit of extra weight on this, but i dont like railroad track like parts on airplanes XD

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Aug 26, 2022 6:21 pm

by 13brv3

I don’t have any notes about the dimensions or weight of the ring mount. I can measure the diameter Monday if you still need it by then. I remember that it seemed heavy, but I couldn’t make an accurate guess of the weight. The installation manual for the Rotax does have some useful dimensions for the attachment points.
Rusty

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Aug 26, 2022 7:43 pm

by xeriotti

13brv3 wrote:I don’t have any notes about the dimensions or weight of the ring mount. I can measure the diameter Monday if you still need it by then. I remember that it seemed heavy, but I couldn’t make an accurate guess of the weight. The installation manual for the Rotax does have some useful dimensions for the attachment points.
Rusty

Knowing the weight would be important… To make an estimation of the thickness…its obviously 4130 steel. So depending on the available materials to make my own mount…ill have to trade some weight to have correct safety margins.

Making my ringmount out of 2mm thick 304L stainless would result in a weight of 2.3kg (ring only without the tubes that go to the motor)

It seems light to me and making it out of 3mm thick wouldnt be soooo heavy… its would end up around 3.5kgs ring only. Then there are 8 sections of tube that go to the engines anchor bolts less than 20cms each…buts lets say they are 20cms each just for the calc… … i have 1.8mm 4130 tube for that… it may weight around 1.45kg according to my calculation.

A total of 5kg for my homemade ring mount. beign really safe with 3mm 304L main tube and 1.8 thick 4130 legs.

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Aug 27, 2022 2:06 am

by Kai

Ive seen someone making an adapter from a solid piece os 12mm steel… But i dont know…i calculated it to be around 3 kilograms for the plate only… Ill try to make something lighter without compromising strenght… (sounds easy XD)[/quote]

Yep- that was me!
Just to make it abundantly clear- the 12 mm thickness of the adapter plates was selected because of the aim to utilize (the already in stock) harder Sonex rubber isolators for the Jab33, as well as its mount. If someone could find 12mm Al 6061T6 or 7075T6, strength would not be compromised- at a lower weight. However, in this country, no such luck! The one big advantage of using the mount for the 33A, is that it pulls the Rotax as far back as possible (from heel to toe, with its standard ring mount, the 912 is even longer than the 33).

Everything said and done, the plane has been airborne for close to 50 hrs by now. So far, no nasty surprises- in fact no surprises at all. EW t/o mass with oil and coolant, but no fuel, came out at 309 kgs. The corresponding CG lies smack bang at 20% aerodynamic cord- the forward limit. The plane has been spun with 2 persons and half fuel: standard recovery works like a charm.

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Aug 27, 2022 1:42 pm

by xeriotti

Kai wrote:I
Yep- that was me!
Just to make it abundantly clear- the 12 mm thickness of the adapter plates was selected because of the aim to utilize (the already in stock) harder Sonex rubber isolators for the Jab33, as well as its mount. If someone could find 12mm Al 6061T6 or 7075T6, strength would not be compromised- at a lower weight. However, in this country, no such luck! The one big advantage of using the mount for the 33A, is that it pulls the Rotax as far back as possible (from heel to toe, with its standard ring mount, the 912 is even longer than the 33).

Everything said and done, the plane has been airborne for close to 50 hrs by now. So far, no nasty surprises- in fact no surprises at all. EW t/o mass with oil and coolant, but no fuel, came out at 309 kgs. The corresponding CG lies smack bang at 20% aerodynamic cord- the forward limit. The plane has been spun with 2 persons and half fuel: standard recovery works like a charm.

Kai! Ive seen your work! It would be my option to do it just like you, but my engine didnt come with any mount at all… So…I have to couple the Aerovee mount to a plain Rotax.

What im trying to achieve is my own Ring Mount, with my own rubber damper sistem and Aerovee mount spacing. Im around 40mm forward of where the Aerovee prop hub would be…

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Aug 27, 2022 2:35 pm

by Kai

There is always more way than one to skin a cat!
This one (Pay particular attention the the square tube stiffener bar between the two upper aluminium attachment angles in the airframe) is done by a guy in Sweden- scratch built from the ground up. The amount of work must have been overwhelming!

Re: Aeroovee to Rotax mount conversion???

Posted: Wed Aug 31, 2022 11:57 am

by xeriotti

My lasercuts are ready, my rubbermount housings too… no more excuses! start welding!

Laser is so exact! Love it!.. a few taps with a hammer are enough to maque everything fit perfectly. I assembled it with a few tacks and tried it on the plane to see if everything was OK

Like a charm

Heres the part that you can really screw things up… It isnt weld porn at all, but not bad for a mig running CO2

Penetration on the other side (keep in mind the rubbermount bushing walls are 3mm and the core is 5mm thick)

Welding it on the inside would be sufficient… But i welded the outside and will flatten it out later with an abrasive flapdisc

Im planning to add some ribs on the inside to reinforce it a little bit more…It might be overkill but i preffer those 300 extra grams of steel in there for my peace of mind

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 01, 2022 10:45 pm

by xeriotti

This will bolt to the engine rear anchor points… Those are 10mm 8.8grade bolts.

The center reinforcing rib is ready. its so stiff i decided to go down on the thickness of the inside and outside perimeter.

Looks legit XD

Ready to start welding the perimeter and around the damper housings to close the “box”

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Sep 02, 2022 2:02 am

by Kai

Keep up the good work. This is getting interesting!

I am very curious to see what engine anchor points you will use, and how you will attach them to your ´ring mount´.

Your 40mm forward movement of the Rotax prop flange compared to the Aerovee is not something to worry about CG wise: my own 35mm did not turn out to be an issue. Another matter altogether is the standard engine cowling, which will be in for some drastic modifications. If like me you hate composite work- the best of luck!

It is obvious you have thought of something Rotax did not- accessebility to the water pump inlet albow: their own ring as good as blocks all attempts for a good hookup.

KEEP THE PHOTOS COMING!

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Sep 04, 2022 2:30 am

by xeriotti

This takes more measurements and calculations than expected… But its on its way!!!

Im going to use the four rear anchor points… And 2 tubes connectiong each to the “ring”…

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Sep 13, 2022 1:43 am

by xeriotti

Inner and outer TIG welded perimeter ready… It forms a box, looks really strong… Lighter than making it from aluminum, feels firm…

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Sep 13, 2022 7:53 am

by 13brv3

That’s a lot lighter than I would have guessed. Now for the fun part of adding the engine attachments.
Rusty

ArchiveBot · August 10, 2022, 5:00am

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Sep 17, 2022 11:26 am

by xeriotti

13brv3 wrote:That’s a lot lighter than I would have guessed. Now for the fun part of adding the engine attachments.
Rusty

Im with other projects on the go… But i have the attachments almost ready… 4 anchor points in the engine and 8 tubes connecting to the adapter plate… I already have 3 tubes done, when the 4th is ready i might rtack weld it together to resolve the other 4…

Its not fun at all… Takes lots of guessing measures and lucky strikes to make those notches and leghts right!!

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Sep 17, 2022 11:28 am

by Bryan Cotton

Nice work! I’m enjoying the fabrication pictures.

It’s type 2 fun - where it seems more fun later.

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Sep 17, 2022 12:24 pm

by xeriotti

Its not a modern art sculpture… Its working alone XD

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Sep 18, 2022 12:20 am

by xeriotti

Saturday night special… Took a little more measuring and trial and error than expected at first but with a blend of a little metalworing skill and a ton of luck with tha handmade notched tubes it ended up pretty much perfect…

Its only tacked in placee, next step is to fully tig weld everything, heat treat, bead blast and powder coat it white (aerovee mount is black… i worked so hard to get it right i want it to stand out when cowling is off XD)

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 22, 2022 12:01 am

by xeriotti

Its looking good… almost stained my fingers white to put it there jajajaja

When its totally dry im bolting it to the engine, meanwhile i have to sort other things out…liek the alminum washers for the rubber mounts…

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 22, 2022 9:13 am

by 13brv3

That certainly looks like it will work. Thanks for all the pictures.
Rusty

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 22, 2022 3:09 pm

by Kai

Ï can only agree with all the others- an impressive piece of work indeed! The low weight is frankly astounding! My best wishes for all possible final success.

Yet I cannot refrain from pointing out, that there might possibly have been introduced some avoidable structural issues in both this ring mount, and the complete design as a whole.

The first one I already pointed out in an earlier posting in this thread: the missing upper square tube on the Aerovee engine mount as seen on original J33A engine mounts. It must be realized that the R912 is close to identical in weight to the J33A, and that with its reduction gear it produces torque (it torques to the left: RIGHT pedal!!) of a magnitude previously not seen by the upper fuselage angle attach brackets. The decision to omit this square tube stiffener should be made after careful consideration.

The second one is best illustrated by posting a photo of an original R912 ring mount- if one looks closely and compares the two designs, it is easy to see: one upper engine support tube is missing. In addition several of the engine support tubes are just not only butt welded to the front of the ring, but in fact go through it and are also welded at the back.

My two bits.
Thx

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 22, 2022 3:44 pm

by Kai

Further to my previous posting directly above, I enclose a photo of yet another amateur built Sonex Legacy/R912 engine mount, based on the original Rotax ring. Very clearly the upper square tube cross stiffener is illustrated. Also note that this tube supports a lot of the engine loads.

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 22, 2022 8:28 pm

by xeriotti

Kai!! we are tuned in the same frecuency!!!

Im definitely going to add that crossbar reinforcement… Im toing to sandwich sing the already existing mounting points on the waiex where the engine mount meets the aluminum fuselage. Rotax produces lots of thrust and torque… I think its a must.

About the missing tube… My tubes are anchored more widely, forming triangles that will avoid that paralelogramic effect the guys at rotax tried con counter with that angled tube up there.

The thru-tubes is a solution when you dont have enough wall thickness for an optimal weld… In my case, the tubes that connect to the engine are .083in thick 4130, welded to a 1/8" thick plate… The rest of the engine mount isnt as tough…And i dont know of any engine ripped off a sonex to date XD

I painted it white, i will regularly check it but I think it will work fine…

I really appreciate all the knoledge, help and ideas you guys give me… Every small idea or comment is added safety, fun and is what makes experimental aviation so marevelous… Really valuable for me and for every person that reads our lines

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Sep 24, 2022 12:20 pm

by xeriotti

It fits, and looks neat…

Aluminum washers to contain the rubber dampers… Made the bad way with a 60mm cup saw that gives me 56mm washers…

Drilled the 10mm center to fit the engine mount thats on the plane, bolt it together with an M10 bolt and lathe turned to 50mm OD

Shiny faces flattened and polished by hand.

In no more than 10 minutes with a little help from my dad it was on the airframe… Surprisingly easy!

Rather Important… My center hub distance to the ground with the airplane leveled (window at 0 degrees) is 40.35" (102,5cms) Applying the 9" clearance rule, i would be able to fit a 62.7 inch propeller…
Im going to fit 500x5 tyres, and I may have a little less clearance… But performance is king. A 68" custom made wooden propeller is on its way

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Sep 24, 2022 12:25 pm

by Bryan Cotton

xeriotti wrote:Aluminum washers to contain the rubber dampers… Made the bad way with a 60mm cup saw that gives me 56mm washers…

The bad way! No way! I’ve made a lot of washers with a cup saw, or holesaw as we call them over here.

Looks great!

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Sep 24, 2022 3:19 pm

by Kai

Yup!

It is just a question of measuring the inner diameter of the coleslaw- sorry: hole saw, and add perhaps a mm or two. That is the washer diameter you will need. You need to make sure that the washer covers ALL of the rubber damper surface. If not you may be sure that the washer will start to dig into the rubber.

Don´t ask how I found out.

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Sep 24, 2022 9:27 pm

by xeriotti

Kai wrote:Yup!

It is just a question of measuring the inner diameter of the coleslaw- sorry: hole saw, and add perhaps a mm or two. That is the washer diameter you will need. You need to make sure that the washer covers ALL of the rubber damper surface. If not you may be sure that the washer will start to dig into the rubber.

Don´t ask how I found out.

jajajajaja Ive learned lots of stuff that people shouldnt ask how i did!!! XD

Listen… Anyone know how is the engine oriented in Rotax equipped Sonex/Waiex? How much compensation for p-factor and attitude This one ended straight ahead (0 de grees laterally) …and 1.8 de degrees pointed down..

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Sep 25, 2022 1:59 am

by Kai

Well,

My guess is purely speculative: nothing at all- straight as a ramrod.

Certainly no angular deviation from the 3 main axis centerlines- especially nothing ´nose down´. The reason is the overly effective barn door flap which tends to stand the plane on its nose on final: there is not enough trim authority to compensate, and you need additional help from the elevator. With a little down angle on the prop and the engine on anything more than low idle, this would certainly aggrevate the situation.

The ones we do up here are all oriented with the prop flange in the same planes as the Jab 33A. Longitudinally this is easier said than done- a lot depends on what dimensions the original engine mount has.

Should the installation check reveal any deviations, this is adjusted with washers.

Thx

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Sep 25, 2022 2:24 pm

by xeriotti

And what angle are Aerovees and Jabs pointed???

Im thinking about test flying it…before fitting the cowling… That way if theres any correction to be made i can modify the cowling to perfectly line to the prop cone.

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Sep 25, 2022 2:32 pm

by 13brv3

I wouldn’t angle the engine up or down, but I’d certainly allow for some right offset to compensate for the left turning thrust. I left mine straight, and there’s a pretty big change in yaw when you add or reduce power. At some point, I’ll shim the engine to the right, though I have no clue how much would be needed.

Rusty

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Sep 25, 2022 7:53 pm

by xeriotti

13brv3 wrote:I wouldn’t angle the engine up or down, but I’d certainly allow for some right offset to compensate for the left turning thrust. I left mine straight, and there’s a pretty big change in yaw when you add or reduce power. At some point, I’ll shim the engine to the right, though I have no clue how much would be needed.

Rusty

What the manual says about engine angle? In other aircraft its usually 2 degrees pointing down and maybe 1 or two compensating p-factor…

What are you guys using and what are your results?

Re: Aeroovee to Rotax mount conversion???

Posted: Mon Sep 26, 2022 7:42 am

by Skippydiesel

I am sure that I have seen this debate elsewhere - the result “fence sitting” ie about equal numbers for/against, with neither side bringing a scientific/researched/tested argument to sway the reader in either direction.

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Sep 27, 2022 2:18 am

by xeriotti

Skippydiesel wrote:I am sure that I have seen this debate elsewhere - the result “fence sitting” ie about equal numbers for/against, with neither side bringing a scientific/researched/tested argument to sway the reader in either direction.

Im flying it without cowling…If it flies striaight and has no weird tendencies when applying or substracting throttle im leaving it as it is and proceed with the cowling… Unless someone changes my mind along the way XD

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Sep 27, 2022 2:28 am

by xeriotti

And some updates… Im rtying to solve my firewall forward. So im starting with what i think are the easier items…

Im fitting a 22ah Gel-AGM Battery… It will be held in place with this box and backplate (firewall is so thin.. the backplate will have welded nuts on it and will be ribeted in place from the inside) The box will be held in place via 5 M6 screws. Aint going nowhere.

And this is my 30 degree oil reservoir mount for the firewall… Also has a reinforcement backplate for the firewall

No aluminum available fast, esasy and cheap… So im going for stainless if available, otherwise…mild steel and then powdercoating.

Up next I will try to solve the exhaust system… Id love to make a 4 to 1 happen… Sounds beautifuly disturbing and im sure there is some performance gain in there..

Re: Aeroovee to Rotax mount conversion???

Posted: Wed Sep 28, 2022 1:41 pm

by xeriotti

Lasercuts are here… I may drive to the hangar in a while i have a sheet metal bender there…

Started mocking up the 4 to 1 exhaust.. Equal lenght headers is the goal… Stainless steel tubing is on the way for the fabrication

Re: Aeroovee to Rotax mount conversion???

Posted: Wed Sep 28, 2022 3:22 pm

by Kai

Exhaust headers:

Maybe you could pick up some ideas from the exhaust system Rotax has developed for the R914.

Don´t let the turbine housing on this NA engine confuse you- it´s just there to provide a temporary anchor point for the R914 turbo muffler, which later on in the prosess was substituted with a specially manufactured elbow. This elbow is the only item in the system which is not standard Rotax, and which should be no problem at all for a welding virituoso like you to manufacture.

The resulting exhaust noise is very pleasing: a sort of dark, angry growl. The whining, clattering 912-sound is gone.

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 29, 2022 2:19 am

by xeriotti

With a little bending my 3d file turned into a pretty decent oil reservoir mount… I will give it some magic and then to powdercoating.

This beauties arrived and after diner i started fabricating the exhaust headers… I made 3 out of 4 before midnight (thats my deadline for using powertools like a maniac… Theres no problem, but i respect my neighbors after that specific hour jajaja)

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 29, 2022 9:59 am

by 13brv3

That some seriously impressive fabrication skill. At the rate you’re going, you’ll be flying in a couple weeks
Rusty

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 29, 2022 2:30 pm

by xeriotti

13brv3 wrote:That some seriously impressive fabrication skill. At the rate you’re going, you’ll be flying in a couple weeks
Rusty

Thanks for your words! Its easy to stay motivated when you literally see the pile of random pieces turn into a plane!
I really enjoy flying. But the sensation of building something that flies… Thats really strong. A mix of sensations, when you go off plans and start finding solutions, when things click, when you receive a compliment about your craftmanship, creativity or ingenuity… That my friend is what got me hooked into building planes… Im always building, repairing, upgrading or messing something up since i tried this drug called experimental aviation.

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 29, 2022 4:04 pm

by Kai

Yup!

I´m with you as far as the messing up things goes- high five!

From my days as an engine application engineer some exhaust system guidelines emerge:

Engines hate bends and elbows in the exhaust system-especially a tiny unit like the 912. They create back pressure which is highly undesireable. The rule of thumb is that one 90 degree 3D (the bending radius is three times the pipe diameter) creates back pressure 16 times the equivalent length of straight pipe (I am speculating you have 4D bends). Try to keep total pipe lengths and the total deviation in degrees as identical as possible for the four pipes; if the difference is too big, you are building a variation in egt´s into the system.

A roller coaster unit like a running 912 in its mounts is really jumping about all over the place. Somewhere very close to the exhaust ports you need something that can take up this movement. You also need something that can take up thermal expansion/contraction. If not you will face cracked piping.

And:
I have been leafing through my construction drawings (issues 2003!). They include building instructions for the Aerovee-, Jab 22A-, and Jab 33A engine mounts, and are intended for use if the builder wants to weld up his own truss. They are all dead straight in all axis- no deviation whatsoever.

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 29, 2022 7:24 pm

by Zack

Here is my custom Rotax exhaust. The factory bed mount drove much of my design choices, I really like how you integrated the ring mount! I think that’s how it should have been done from the start. I had to take a 4-2-1 approach. From Sonex’s webinar, they chose a similar setup but used a Toucan exhaust without a final merge, so it’s really two 2-1 exhausts with a center line exit.

Regarding my design, I used PipePRO software application to try and determine ideal collector length, but between the assumptions I needed to make for the application and the compromises I needed to make working around the mount, I’m not sure what advantages I will see. I tried to keep the collectors all equal lengths, I used stainless steel also, and I used inline motorcycle style mufflers. In fact, I hired the job to a motorcycle shop used to working with the smaller diameter pipes and fabricating custom exhausts.

What diameter collectors are you using? Will you step up diameter after the collector? Will you use an in-line muffler? I’m enjoying following your progress. Thanks Kai for contributing also.

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Sep 29, 2022 7:26 pm

by Zack

Here is the bottom view.

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Sep 30, 2022 2:00 am

by xeriotti

Kai wrote:Yup!

I´m with you as far as the messing up things goes- high five!

From my days as an engine application engineer some exhaust system guidelines emerge:

Engines hate bends and elbows in the exhaust system-especially a tiny unit like the 912. They create back pressure which is highly undesireable. The rule of thumb is that one 90 degree 3D (the bending radius is three times the pipe diameter) creates back pressure 16 times the equivalent length of straight pipe (I am speculating you have 4D bends). Try to keep total pipe lengths and the total deviation in degrees as identical as possible for the four pipes; if the difference is too big, you are building a variation in egt´s into the system.

A roller coaster unit like a running 912 in its mounts is really jumping about all over the place. Somewhere very close to the exhaust ports you need something that can take up this movement. You also need something that can take up thermal expansion/contraction. If not you will face cracked piping.

And:
I have been leafing through my construction drawings (issues 2003!). They include building instructions for the Aerovee, Jab 22A, and Jab 33A, and are intended for use if the builder wants to weld up his own truss. They are all dead straight in all axis- no deviation whatsoever.

I tried to keep the lenghts/volumes as similar as possible… I will measure the CCs of each header maybe tomorrow to know how much its off one from each other. But im pretty confident on how it came out. its pretty close measuring the lenght, maybe ±1cm
If we consider that almost 95% of cars use unequal lenght exhaust systems and almost all of them are just logs… This will be a great upgrade.

Zack wrote:Here is my custom Rotax exhaust. The factory bed mount drove much of my design choices, I really like how you integrated the ring mount! I think that’s how it should have been done from the start. I had to take a 4-2-1 approach. From Sonex’s webinar, they chose a similar setup but used a Toucan exhaust without a final merge, so it’s really two 2-1 exhausts with a center line exit.

Regarding my design, I used PipePRO software application to try and determine ideal collector length, but between the assumptions I needed to make for the application and the compromises I needed to make working around the mount, I’m not sure what advantages I will see. I tried to keep the collectors all equal lengths, I used stainless steel also, and I used inline motorcycle style mufflers. In fact, I hired the job to a motorcycle shop used to working with the smaller diameter pipes and fabricating custom exhausts.

What diameter collectors are you using? Will you step up diameter after the collector? Will you use an in-line muffler? I’m enjoying following your progress. Thanks Kai for contributing also.

That Zack looks great!!!.. Im using 29.8mm internal diameter headers, and as a rule of thumb i should be stepping up 1.9 times that for the collector. and 0.5 times the diameter.

I will make it slip on with springs…if it sounds horrible i will set up some kind of silencer. But i have real good expectations for sound and power levels.

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Sep 30, 2022 2:12 am

by xeriotti

Its almost done!.. Tomorrow ill take care of that 4 to 1 collector, it will be fixated with springs (already bought them )
And I think im going for a 1.5 times diameter and 0.5 times lenght tube after the collector. I will try to make it slip on with 3 springs so i can try fun stuff later. The plane has aerobatic capabilities so a smoke system will e installed as soon as we become friends.

My exhaust building frenzy ended at 2AM… My neighbors wife was trying to sleep and the angle grinder had other plans for her XD

ArchiveBot · August 10, 2022, 5:01am

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Oct 02, 2022 8:52 pm

by Zack

Zack wrote:From Sonex’s webinar, they chose a similar setup but used a Toucan exhaust without a final merge, so it’s really two 2-1 exhausts with a center line exit.

Here’s the video I was referring to: https://www.youtube.com/watch?v=OzNc-DfczJw&t=1s

However, I noticed when the one week wonder flew they chose a more direct approach out of the cowling. I wonder why they made the change.

Re: Aeroovee to Rotax mount conversion???

Posted: Mon Oct 03, 2022 1:10 pm

by xeriotti

Zack wrote:

Zack wrote:From Sonex’s webinar, they chose a similar setup but used a Toucan exhaust without a final merge, so it’s really two 2-1 exhausts with a center line exit.

Here’s the video I was referring to: https://www.youtube.com/watch?v=OzNc-DfczJw&t=1s

However, I noticed when the one week wonder flew they chose a more direct approach out of the cowling. I wonder why they made the change.

Easier and much faster to do… Gets the work done. All other exhaust configurations are oriented either to quietness, interior comfort and respect for other peoples hearing…or… Just performance at expense of extra cabin noise and guaranteed neighbors complaints XD

My aproach on the cowling will be a little bit off plans… Im going for a more streamlined version, using the original cowling is out of the table… has nothing to do with the 912 shape and lenght from firewall to the prop hub…

Re: Aeroovee to Rotax mount conversion???

Posted: Mon Oct 03, 2022 6:38 pm

by Skippydiesel

Hi Xeriotti - On cowling matters;

You may be surprised & frustrated by how much time you may spend on getting your cowling to perform correctly - its not just about looks & speed its also about temperature/ventilation performance

Pretty much had my Sonex finished by about Match this year - still hasn’t taken to the air .
Why?
Cowling issues. Have designed and installed my own cowling. Looks great BUT I am not happy with the engine temperatures.
Have been cutting extra holes in my cowling & have fitted an electrically operated cowl flap. All this has taken months months of (unexpected addition) work.
May now have the temperatures sufficiently under control to contemplate test flying - we will see

Re: Aeroovee to Rotax mount conversion???

Posted: Mon Oct 03, 2022 9:17 pm

by xeriotti

Yes I know!!! Ive been working lowering temperatures in other types of aircraft and i know the problems i may be facing… My idea is to streamline the fron as much as possible… And adding a big naca vent on the left side of the plane, ducted directly into the water radiator… positive pressure on the front and vacuum from the cowling flap on the back…cant go wrong with that recipe… My oil cooler is already installed its bigger in area than reccommended. I will monitor the oil temperature… If i need to lower it i will cover partially with aluminum sheet…if i need to lower i can duct direct airflow from the side of the cowling intake.

There are guidelines to follow, but in the end to get it perfectly dialed…its trial and error.

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Oct 04, 2022 1:31 pm

by Zack

I wish Sonex would be more public about their efforts to develop the Rotax firewall forward package. I think they made the decision to work within the current cowling early on and are constrained further by the tri gear option with the nose wheel firewall forward. Drawing air through a pair of stacked oil and coolant coolers using the two side vents doesn’t seem adequate based on my poor analysis of other flying Rotax powered aircraft. Maybe Sonex thinks this will work due to the higher airspeeds this airframe has versus many other Rotax powered aircraft? This split design does avoid the space constraints of placing oil, coolant and nose wheel on the centerline, plus developing cowling “blisters” to accommodate the cooling. Perhaps running the exhaust to a single central exit by the firewall raises temps in the cowling too much? Easier and faster is also another good reason for the change!

Skippy, I worry if my cooling solution will work as well. I have a separate radiator duct that should be adequate. If it isn’t, wow that’s a major change to enlarge. I have two Sonex side vents to depressurize the cowling that had to be further opened to match the curvature of my cowling. The air moving through these vents will cool the oil cooler, air cooled parts of the engine, and remove exhaust waste heat. If Sonex is successful, then I will have more cooling drag than necessary.

Xeriotti, another reason the original cowling is out of the picture appears to be your spinner size! Are you doing a constant speed or ground adjustable propeller that needs the extra size? Regarding your exhaust exit, will you do a streamlined exhaust tunnel with the bottom of your cowling, or will the cowling be flush with the belly and the exhaust angled into the airflow?

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Oct 09, 2022 12:08 pm

by Kai

xeriotti wrote:My aproach on the cowling will be a little bit off plans… Im going for a more streamlined version, using the original cowling is out of the table… has nothing to do with the 912 shape and lenght from firewall to the prop hub…
[/quote][/quote]

Yup!

The Sonex cowling for the 912 is a puzzle. What shot me down was making room for the fairly bulky R912 muffler in combination with equal length exhaust piping from the cylinders. With my aversion for composite work I elected to go the aluminium way. Some less diplomatic soul labeled the end product´function over form´: I can´t say I totally disagree!

I started out with just the side outlets as suggested by Sonex- this did not work for me. I then rebuilt the cowling with bottom outlets as well- with these outlets flush with the cockpiten floor: success!!

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Oct 09, 2022 3:52 pm

by 13brv3

Until there’s a factory tested FWF solution, there will never be any two alike. You guys should be glad you have all that extra width to work with. For the Onex, I used the brute force single scoop on the bottom method that directly feeds the radiator and oil cooler behind it. No cooling issues yet, but more HP is coming soon…

Rusty

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Oct 14, 2022 3:33 pm

by xeriotti

Zack wrote:I wish Sonex would be more public about their efforts to develop the Rotax firewall forward package. I think they made the decision to work within the current cowling early on and are constrained further by the tri gear option with the nose wheel firewall forward. Drawing air through a pair of stacked oil and coolant coolers using the two side vents doesn’t seem adequate based on my poor analysis of other flying Rotax powered aircraft. Maybe Sonex thinks this will work due to the higher airspeeds this airframe has versus many other Rotax powered aircraft? This split design does avoid the space constraints of placing oil, coolant and nose wheel on the centerline, plus developing cowling “blisters” to accommodate the cooling. Perhaps running the exhaust to a single central exit by the firewall raises temps in the cowling too much? Easier and faster is also another good reason for the change!

Skippy, I worry if my cooling solution will work as well. I have a separate radiator duct that should be adequate. If it isn’t, wow that’s a major change to enlarge. I have two Sonex side vents to depressurize the cowling that had to be further opened to match the curvature of my cowling. The air moving through these vents will cool the oil cooler, air cooled parts of the engine, and remove exhaust waste heat. If Sonex is successful, then I will have more cooling drag than necessary.

Xeriotti, another reason the original cowling is out of the picture appears to be your spinner size! Are you doing a constant speed or ground adjustable propeller that needs the extra size? Regarding your exhaust exit, will you do a streamlined exhaust tunnel with the bottom of your cowling, or will the cowling be flush with the belly and the exhaust angled into the airflow?

I love everything about the Sonex/Waiex…but always fantasized about putting a big prop cone to make it more… pointy XD Its for pure looks, and thats something people may like or not. I think i will like it. Im going for a fixed pitch propeller right now.

My idea is to protrude the exhaust tube a couple inches, cut is slanted to match the airflow.

Stacking radiator is not a good idea… I will try to mount them so one of the side faces towards a low pressure area and i will either direct airflow into it…or for more efficiency duct directly into the radiators.

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Nov 10, 2022 4:44 am

by xeriotti

Been off the forum for a couple weeks!!! Sorry… The Rotax install is almost done!!!

Im using a radiator from a Volkswagen Gol… Its a supplementary radiator that i changed the inlets to fits rotax size and orientatio nof my setup… I custom made a radiator mount…here it is

I already got all my wiring done… And my instrument panel is complete and ready to ribet in place once i check theres no anything wrong uner normal operation.

An this is how the install looks now… Im happy bout the outcome of this project

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Nov 10, 2022 11:01 am

by Bryan Cotton

That looks awesome!

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Nov 11, 2022 7:15 pm

by Brett

Is that some sort if muffler or just a large collector? Will be interested to see how loud it is. I manged to fit my muffler in but am glad to be honest.

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Nov 12, 2022 2:21 pm

by xeriotti

Brett wrote:Is that some sort if muffler or just a large collector? Will be interested to see how loud it is. I manged to fit my muffler in but am glad to be honest.

Its a BFC… Big Fat Collector XD

Collector diameter, has to do with headers diameter and lenght… There are calculations to make it perform best. When putting together an exhaust system for an aircraft sometimes theres no room or the optimal solution just cant be fitted… This gets pretty close to that. I have great expectations for this setup

It sounds amazing.!! Pretty much like a sportbike (My neighbour complained about that last night)… like a 929 i used to have… Its loud but sounds fat… Havnt heard it outside yet, but i bet a 180mph flyby with that engine screaming almost 6k rpm will be nice to hear… its raining now, but im taking it to the airfield to fit the wings as soon as it dries

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Nov 15, 2022 2:06 am

by xeriotti

A 5kms ride to the hangar… I may fit the wings tomorrow

Anyone flown their plane with no cowling? i want to make sure it flies straight before i make my cowling…

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Nov 15, 2022 2:11 am

by Bryan Cotton

xeriotti wrote:Anyone flown their plane with no cowling? i want to make sure it flies straight before i make my cowling…

That seems like a bad idea. For those of us with aircooled engines it’s not an option at all, as the cowling forces the air through the heads rather than letting it go around. It would be very draggy though.

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Nov 15, 2022 4:27 am

by Kai

Bryan,

Yes- agreed.

If my experience is anything to go by, I would not be too concerned about cooling. Initially my engine was doing just fine without the cowling on the ground at full tilt, but overheated badly with the thing installed.

Aerodynamics is as you say another matter altogether. When I did my builders course in Osh back in 2004, I recall John telling us that the cowling was an essential part of the flying qualities- and no one had ever test flown without one. We were also told that the front of the plane below the straight line from the back of the prop to the point where the canopy started to curvature was a mini lifting body: don´t impose too many deviations.

If his engine is straight in all axis, he won´t have any great surprises- apart from the fact that on the ground it pulls to the left like there is no tomorrow: right pedal! There must be enough free space under his cowling and the engine to put in a few aluminium spacers for alignment should they be needed.

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Nov 19, 2022 12:05 am

by xeriotti

Kai wrote:Bryan,

Yes- agreed.

If my experience is anything to go by, I would not be too concerned about cooling. Initially my engine was doing just fine without the cowling on the ground at full tilt, but overheated badly with the thing installed.

Aerodynamics is as you say another matter altogether. When I did my builders course in Osh back in 2004, I recall John telling us that the cowling was an essential part of the flying qualities- and no one had ever test flown without one. We were also told that the front of the plane below the straight line from the back of the prop to the point where the canopy started to curvature was a mini lifting body: don´t impose too many deviations.

If his engine is straight in all axis, he won´t have any great surprises- apart from the fact that on the ground it pulls to the left like there is no tomorrow: right pedal! There must be enough free space under his cowling and the engine to put in a few aluminium spacers for alignment should they be needed.

No one ever flown one with no cowling? :S

The engines alignement is mentioned anywhere on the plans? My engine is flat with the aerovee mount… so its like factory supplied it. But really would want to test fly it before making a cowling from scartch

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Nov 19, 2022 12:07 am

by xeriotti

Looks like it would fly without a cowling to me…

Re: Aeroovee to Rotax mount conversion???

Posted: Sat Nov 19, 2022 10:54 am

by builderflyer

xeriotti wrote:

Looks like it would fly without a cowling to me…

Similar to what Kai recalls, I remember John Monnett explaining to us that the fuselage (which would obviously include the cowling) of the Sonex was designed in the shape of an airfoil and that it supplied a percentage (maybe 15 %) of the total lift of the aircraft. So, given that, one would have to assume that flying without a cowling would have a noticeable effect on the performance. You may want to pass this question by John Monnett before attempting a flight.

Art,Sonex taildragger #95,Jabiru 3300 #261

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Nov 20, 2022 5:32 pm

by rizzz

It would be good if someone like Joe could chime on this topic.

My opinion about attempting to fly without a cowling? Really, really, really bad idea! Seriously!
I urge you to rethink this or at least have a chat with the people at Sonex before you go ahead with this.

As many have stated, the shape of the fuselage of a Sonex/Waiex provides a significant amount of additional lift.
You say, “Looks like it would fly without a cowling to me…” !
Well! It looks like it would fly without a canopy as well but there are a few people who have actually inadvertently done so and as they will tell you, it really doesn’t!
Here’s one example: /viewtopic.php?f=25&t=6646&hilit=canopy

If not having smooth air flow over the top of the plane makes that much difference, what to you think not having smooth airflow over the nose of your plane will do?

And in the end, what are you trying to gain by attempting this? Get some idea of how straight it flies before designing your cowling?
I doubt that if it flies at all, it will be flying well enough for you to make any sort of judgement about how straight & level it’s flying.

What about just making your cowling such that you can still make small adjustments to the position of the engine later on if necessary? That’s what we all did.
And finally, what about putting a trim tab on your rudder if it does not fly straight? We all have one, for exactly that reason, the Jabiru people have if on the opposite side of the VW people since the prop turns the other way.
BTW, like most planes a Sonex flies straight at one speed/engine setting only, we set the trim tab to get the aircraft to fly straight at cruise speed/power, but climbing out significant rudder is required one way and on descent significant power is required the other way. It’s quite a significant amount of rudder that’s required compared to most aircraft I’ve flown and I only have a normal aspirated VW engine.

Sorry to have to be so direct but I fear this has a high probability of ending in disaster.
On a brighter note, I really admire your Rotax engine project so far and I’ve been following it very closely as I dream of one day replacing my VW with a Rotax.

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Nov 20, 2022 11:25 pm

by Kai

So we all agree that a cardiac arrest up there during the first test flight is something that should be avoided.

Having established this and in addition decided not to mess up the front end of the fuselage and stick to the contours suggested in the plans- do you recall that for a while there was something called a Todd´s canopy? I am not absolutely sure why some people went for them, but I speculate that one of the reasons was less prone to cracking during installation and much better resistance of the windshield to mogas. Whatever the reason: it made the front end of the Legacy look like a dolphin- and totally deviated from the plans.

What´s more- I´ve flown one. It also had the smaller flaps. Upstairs there was not much difference. And it was not particularily difficuilt to land either. But you had to keep very strict control of the airspeed during the flare- a tad too slow and the famous Legacy float was gone: whammo! and you were careening down the strip much faster than originally intended.

Better stick to the plans. Aerodynamic prototype development work is only for those paricularily interested.

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Nov 22, 2022 10:08 pm

by xeriotti

Dont worry!!! I changed my mind about flying without a cowling XD… (Thanks BTW)

No pics of the process yet… but ive been shaping the cowling today… im going to use the lower portion of the original cowling provided by Sonex Aircraft… And will shape te front and upper parts to make room for the 912… Im also going to add some naca vents and ducts to accomplish propper cooling of the water and oil radiators…

Re: Aeroovee to Rotax mount conversion???

Posted: Wed Nov 23, 2022 11:38 am

by 13brv3

I’m glad to hear that. When making the cowl, try to leave yourself an easy way to rework it later to add some right thrust angle to the engine. I will be shimming my engine to the right eventually to reduce some of the throttle induced yaw. It’s not a high priority now though.
Rusty

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Dec 01, 2022 4:32 am

by xeriotti

Its really hot over here… And im not a morning persona jaajajaj So im working just a while per day to make this happn…

Recycled the most part from the original Sonex Aircraft cowling… 75% of the sides and almost all the front and belly… And yes… My propeller cone is enormous and sexy XD

Some paper tape adde to imagine how the new hood will look like

The exhaust sounds amazing… Cutaway is ready so it doesnt rubs againsssst anything. Will add a little cowl lip for rigidity and improved cooling purposes

Re: Aeroovee to Rotax mount conversion???

Posted: Wed Dec 07, 2022 9:51 pm

by xeriotti

Ive been playing with packing tape, cardboard and foam…

Im good at molding and ended up beign pretty close to my idea of mean and pointy… But im deffinitely not messing with fiberglass, my friend Diego did his magic…he is a seasoned RC model maker, and he takes part in almost every aircraft project i made that involves composite materials…

A few layers of fiberglass and epoxy resin later… (4 layers of 160 gram bidirectional and epoxy resin)

Looks fast XD

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Dec 29, 2022 11:01 pm

by xeriotti

Working a bit more on the cowling

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Dec 30, 2022 10:18 am

by SonexN76ET

I will endeavor to post more photos soon

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Dec 30, 2022 10:20 am

by SonexN76ET

Your cowling is shaping up nicely.

Here is a photo of my cowling as I prepare it for final finish. Perhaps this will give you some further ideas.

Jake

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Dec 30, 2022 4:44 pm

by xeriotti

SonexN76ET wrote:

Your cowling is shaping up nicely.

Here is a photo of my cowling as I prepare it for final finish. Perhaps this will give you some further ideas.

Jake

Looks great!!!

How you compare your plane…from the Aerovee to the Rotax 912? Cruise Speed, Max Speed, Climb Performance, Fuel comsumption?

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Jan 15, 2023 11:45 pm

by bishoff7

Hi all . I am the guy from Downunder that built that engine mount adaptor that fitted straight onto the Aerovee mount which is still on there and still going fine. As would be expected the rubber mounts have had to be replaced several times over the years but that is the only maintenance that has been required . The mount is far from elegant but practical and fairly easy to fabricate and the drawings for it were done from the dimensions provided from the plans from Sonex and the detailed drawings given on the Rotax web site which could be directly imported into a cad program .Regards Bish

(PS) for what its worth my lessons learned with the Rotax is that it is a far more complex engine than the Aerovee and the fine tuning of your cooling systems are a fairly complex to the point of being a real PITA , having some experience in fluid dynamics is definetly an advantage. The Aerovee is much simpler on install and on maintenance and a sweet motor to boot Regards Bish

Re: Aeroovee to Rotax mount conversion???

Posted: Mon Jan 16, 2023 3:43 am

by Kai

Í´m speculating several of the previous Sonex engine mounts are suitable for adaption to a 912. The first custom built mount I know of positioned the prop flange of the Rotax in the exact same position as the Aerovee- with the welding jig and all it was a tremendous lot of work: never again! Not to mention the purchased Rotax rubber dampers with associated parts wich cost a small fortune.

My own 912 installation was indeed inspired by the beautiful simplicity of the square tube ring mount designed and built by Bishoff77- however the basis for my conversion was the standard Jab33A mount supplied by Sonex, and the Sonex rubbers for that engine. I theorized that the J33A and the R912 are of roughly the same installed weight, so it was only a question of fabricating adapter plates that would mate the 33A mount to the Rotax standard ring mount. These bars came out looking a little scary- someone on these pages that shall remain unnamed unceremoneously labeled them looking like railway tracks: I can´t say I disagree.

Rubber isolators set #1 are still sitting there, but it is early days yet as there are only 55 hours on the engine-sooner or later they will have to be replaced.

Photos of this installation have previously been posted on these pages, so I won´t bother you with that, but it is safe to say that the cowling provided most of the head scratching, both externally and the cooling bit. I ended up with a slightly redesigned cowling bottom and cooling air outlets over its entire width, as well as the side outlets for the B-series. I must have done something right because I am nowhere near overheating, no matter what I do. Two BMW full flow thermostats peg the coolant temp at 72 centigrades.

ArchiveBot · August 10, 2022, 5:02am

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Jan 17, 2023 3:42 am

by bishoff7

Really nice work Jake

Re: Aeroovee to Rotax mount conversion???

Posted: Tue May 23, 2023 2:33 am

by xeriotti

Sorry guys… been lost a couple months Everythings happening OK with the Waiex… Finished the hood and after a couple rides along the runway to feel how it handles on the ground applied full power and basically flew like a dream
First flight was awesome! Full power…That exhaust sounds amazing! Held it down until airspeed was alive… 40-50-60mph and wheels stopped touching the ground by themselves…No aileron roll tendency, adjusted the trim a couple turns and was climbing really steep to maintain 80mph with first notch of flaps on… removed them and airspeed increased inmediately… gained 1000ft and started a shallow turn to the left… on my downwind leg i played a bit with the controls and fell in love with the handling of the plane, does everything right apparently XD… landed full flaps 60-65mph on final… Really predictable energy management and handling at slow speeds. I really liked it.

After that first flight it flew 4.5hours… Hood suffered some changes going after thermodinamic perfection… Once I was happy with the temperatured took it apart to make it look pretty, its all sanded, primed and ready for painting…

I will keep you guys updated on that Rotax 912ULS performance once i try it with wheelpants and leg fairings on

Re: Aeroovee to Rotax mount conversion???

Posted: Tue May 23, 2023 7:55 am

by 13brv3

Congrats! Looks great.

Re: Aeroovee to Rotax mount conversion???

Posted: Tue May 23, 2023 10:14 am

by Bryan Cotton

Awesome! Congratulations!

Re: Aeroovee to Rotax mount conversion???

Posted: Tue May 23, 2023 4:53 pm

by Murray Parr

Congratulations, Beautiful looking plane

Wondering if all your cooling systems work well?

Re: Aeroovee to Rotax mount conversion???

Posted: Wed May 24, 2023 5:07 am

by xeriotti

Murray Parr wrote:Congratulations, Beautiful looking plane

Wondering if all your cooling systems work well?

Murray!!! It took me a while to get it dialed… I swapped my water radiator for a bigger, thicker and fancier one… But the big improvments were achieved when i started playing with the intakes and outlet sizes… When i started i couldnt even run for 10 minutes on the ground without going over water temperature parameters… It took me almos 4 hours of changing things and flying to achieve perfection. now im running with OK temperatures indefinitely no matter my power setting and flying attitude… NACA inlets directly and hermetically ducted into water and oil radiators… rear of the radiators are next to low pressure area from the cowl flaps. frontal intakes hit directly into front cylinders, top intakes deflect and hit rear cylinders and sweep hot air from air filters (ideally XD) Works great…

Re: Aeroovee to Rotax mount conversion???

Posted: Thu May 25, 2023 10:42 pm

by Skippydiesel

xeriotti wrote:

Murray Parr wrote:Congratulations, Beautiful looking plane

Wondering if all your cooling systems work well?

Murray!!! It took me a while to get it dialed… I swapped my water radiator for a bigger, thicker and fancier one… But the big improvments were achieved when i started playing with the intakes and outlet sizes… When i started i couldnt even run for 10 minutes on the ground without going over water temperature parameters… It took me almos 4 hours of changing things and flying to achieve perfection. now im running with OK temperatures indefinitely no matter my power setting and flying attitude… NACA inlets directly and hermetically ducted into water and oil radiators… rear of the radiators are next to low pressure area from the cowl flaps. frontal intakes hit directly into front cylinders, top intakes deflect and hit rear cylinders and sweep hot air from air filters (ideally XD) Works great…

Hi Xeriotti,

My Rotax HD radiator (coolant) temperatures are spot on 95C in the air - still have issues on the ground with temperatures always over 105C, as high as 120C on occasion.

My cooling problem is the oil temperature - best I can do in the air is 104C, when OAT is below 11C and I focus on keeping a very strict straight & level and MAP/RPM exactly by the book. I have the Large Oil Cooler but it just doeskin seem to do the job, when I put my CS prop in Cruise mode.

I am interested in the Extra Large Oil Cooler, now offered by Rotax - it may just be what I need to get my cruise temperatures between 90-100C

I am about to return my Sonex to my home workshop to do do several modifications - the main one being the cooling system lay out at this stage Radiator is moving from low on firewall, to front of engine and Oil cooler, from front of engine, to just in front of where the Radiator is now.

Re: Aeroovee to Rotax mount conversion???

Posted: Sat May 27, 2023 9:34 pm

by xeriotti

Skippydiesel wrote:

xeriotti wrote:

Murray Parr wrote:Congratulations, Beautiful looking plane

Wondering if all your cooling systems work well?

Murray!!! It took me a while to get it dialed… I swapped my water radiator for a bigger, thicker and fancier one… But the big improvments were achieved when i started playing with the intakes and outlet sizes… When i started i couldnt even run for 10 minutes on the ground without going over water temperature parameters… It took me almos 4 hours of changing things and flying to achieve perfection. now im running with OK temperatures indefinitely no matter my power setting and flying attitude… NACA inlets directly and hermetically ducted into water and oil radiators… rear of the radiators are next to low pressure area from the cowl flaps. frontal intakes hit directly into front cylinders, top intakes deflect and hit rear cylinders and sweep hot air from air filters (ideally XD) Works great…

Hi Xeriotti,

My Rotax HD radiator (coolant) temperatures are spot on 95C in the air - still have issues on the ground with temperatures always over 105C, as high as 120C on occasion.

My cooling problem is the oil temperature - best I can do in the air is 104C, when OAT is below 11C and I focus on keeping a very strict straight & level and MAP/RPM exactly by the book. I have the Large Oil Cooler but it just doeskin seem to do the job, when I put my CS prop in Cruise mode.

I am interested in the Extra Large Oil Cooler, now offered by Rotax - it may just be what I need to get my cruise temperatures between 90-100C

I am about to return my Sonex to my home workshop to do do several modifications - the main one being the cooling system lay out at this stage Radiator is moving from low on firewall, to front of engine and Oil cooler, from front of engine, to just in front of where the Radiator is now.

Skippy!!! a CS prop on a Rotax 912 powered Sonex sounds yo me like the way to go!!! What numbers are you seeing? Takeoff Roll, Best Climb? Cruise at what RPM and fuel consumptions???

Re: Aeroovee to Rotax mount conversion???

Posted: Sat May 27, 2023 9:37 pm

by xeriotti

It was really dark when i finished…but i had to take some pictures to show you guys

Re: Aeroovee to Rotax mount conversion???

Posted: Tue May 30, 2023 1:45 am

by xeriotti

Not sure about graphics or not yet, i like it plain red… But I will save my time with some stickers to avoid people asking what engines under the hood XD

Re: Aeroovee to Rotax mount conversion???

Posted: Tue May 30, 2023 4:29 am

by Prince

Looks very sharp. Nice job.

Re: Aeroovee to Rotax mount conversion???

Posted: Tue May 30, 2023 10:24 pm

by xeriotti

Thanks!!! Its getting lots of attention lately XD
Graphics aint here yet… But today it was looking amazing

Re: Aeroovee to Rotax mount conversion???

Posted: Wed May 31, 2023 12:44 am

by 13brv3

No one is going to be able to read the graphics, because the plane is going 100 MPH just sitting still

Re: Aeroovee to Rotax mount conversion???

Posted: Wed May 31, 2023 8:26 pm

by Skippydiesel

Veeeery sexy BUT would like to see some photos of your cowling the exit air system.

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Jun 04, 2023 12:44 pm

by xeriotti

Skippydiesel wrote:Veeeery sexy BUT would like to see some photos of your cowling the exit air system.

Sorry about the noisy quality… Just noticed!!! Not pretty photops but i think the depict how air gets in and out pretty well If theres any questions, please let me know

Re: Aeroovee to Rotax mount conversion???

Posted: Sun Jun 04, 2023 6:44 pm

by Skippydiesel

Thanks Xeriotto. Your photos are a great help to me/my Sonex.

Have you ever had overheating issues with your coolant? cylinder heads ? oil ?

Are you using Rotax Radiator & Oil Cooler?

What size is your Radiator? Oil Cooler?

Re: Aeroovee to Rotax mount conversion???

Posted: Mon Jun 05, 2023 9:49 am

by xeriotti

Skippydiesel wrote:Thanks Xeriotto. Your photos are a great help to me/my Sonex.

Have you ever had overheating issues with your coolant? cylinder heads ? oil ?

Are you using Rotax Radiator & Oil Cooler?

What size is your Radiator? Oil Cooler?

Ive been flying the plane…it has 5 houts on it already, pattern work mostly… Right now im figuring out how to make it work. My normal WATER temperature in straight level flight is around 70C…80C in climb… if you descent, for example in base to final cools down quickly to 65, maybe even 60 if you dive long enough backing off all the throttle… When i land and taxi to the hangar ( no more than 500 meters taxi, my temperature is 90C…

Ive been playing with the size of the inlets… My water radiator was custom made by Pehuen Radiators in Argentina, they make competition radiators its all aluminum 63mm core… Total size is 450x190. Its hermetically ducted at the front and air comes in from the huge vent on the pilots side…

My oil radiator is around 150 by 250mm in front area, receives hermetically ducted air from the outside vent thats placed o nthe copilots side…

I have 2 naca vents on top of the cowling to blow some cool air in thats redirected down right after it enters. and 2 front openings that blow air to the cylinders they look big but i had to reduce their size i norder to “deflate” the cowling and balance my inlet-outlet ratio to make air go thru the water radiator on the side…

Sometimes less is more.

Ill let you know when i have it completely dialed (its winter over here, works perfect but when you look outside and its 42C its a different story..)

I have room to install an electric fan… but will leave that as a last resort.

Re: Aeroovee to Rotax mount conversion???

Posted: Mon Jun 05, 2023 6:58 pm

by Skippydiesel

It sounds like you have too much cooling - I wish that I had the same problem.

Overcooling can usually be helped by reducing either inlet/outlet air flow or using smaller coolers (test by taping of part of the cooler).

Some pilots prefer to use coolant/oil thermostats but for me this would be the last resort, as there is significant additional weight and considerable additional complexity (many more joins to fail)

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Jun 06, 2023 8:25 am

by roberto51it

Skippydiesel wrote:It sounds like you have too much cooling - I wish that I had the same problem.

Overcooling can usually be helped by reducing either inlet/outlet air flow or using smaller coolers (test by taping of part of the cooler).

Some pilots prefer to use coolant/oil thermostats but for me this would be the last resort, as there is significant additional weight and considerable additional complexity (many more joins to fail)

In my Rotax powered RANS S7 I have installed an oil and a water thermostat that are made in Germany, and are installed directly over the oil pump and the water pump (in the oil pump it replaces the pump cover, and the same happens in the water pump) you only need to put one extra oil hose and one extra water hose…simple, effective and almost no weight (machined in aluminum from solid)
Roberto Grassi -Italy
Building kit #1433

Re: Aeroovee to Rotax mount conversion???

Posted: Tue Jun 06, 2023 6:54 pm

by Skippydiesel

Roberto51lit - Thermostat conversions sound very interesting - please give supplier/manufacturer details

Re: Aeroovee to Rotax mount conversion???

Posted: Wed Jun 07, 2023 7:59 pm

by xeriotti

Thermostat conversions only work when you have a setup that can OVERCOOL itself… Im still making adjustments on my inlets to optimize airflow for maximum colling capacity… my goal is to fly 70C straight and level, climb unsustainably at max performance in no more than 90C and be able to let the engine running on the ground with no more than 90C… Im almost there. No electric fans No thermostat… Ill let you guys know when im completely sure about how its doing (6hs flight is too soon to give advice and share specific details)

Skippy, if you want PM me we can get in touch and i can give a look to your configuration… I made acouple conversions and ive learned some tricks the hard expensive ways jajajaja i use whatsapp, facebook messenger, telegram if you or any from the forum want to talk about airplanes…If i can be helpful it would be great.

Im also developing a 68" propeller with the correct pitch and shape to make the 912 glow in the Waiex. Ill let you guys know when its ready

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Jun 08, 2023 2:10 am

by Skippydiesel

xeriotti wrote:Thermostat conversions only work when you have a setup that can OVERCOOL itself… Im still making adjustments on my inlets to optimize airflow for maximum colling capacity… my goal is to fly 70C straight and level, climb unsustainably at max performance in no more than 90C and be able to let the engine running on the ground with no more than 90C… Im almost there. No electric fans No thermostat… Ill let you guys know when im completely sure about how its doing (6hs flight is too soon to give advice and share specific details)

Skippy, if you want PM me we can get in touch and i can give a look to your configuration… I made acouple conversions and ive learned some tricks the hard expensive ways jajajaja i use whatsapp, facebook messenger, telegram if you or any from the forum want to talk about airplanes…If i can be helpful it would be great.

Im also developing a 68" propeller with the correct pitch and shape to make the 912 glow in the Waiex. Ill let you guys know when its ready

Way way too cold Xeriotti - Rotax commendation is for sustained (5-20M ins?) 100C + at least once per flight/day - this is to drive off (boil) any light fractions/contaminants from the crankcase oil (eg water/fuel/by products of combustion).

Minimum 50C for engine Run Up & TO/Climb Out

Cruise - Rotax allow up to 104C continuous however I am not comfortable with my engine oil being above 95C

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Jun 08, 2023 8:53 pm

by xeriotti

I know i know!!! Im loking for the best efficiency to cool it down… Then im going for an inline thermostat to make it stable

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Jun 08, 2023 9:54 pm

by Skippydiesel

Where did you find the in line coolant thermostat??

Make sure the thermostat back plate has a small pressure relief hole

Re: Aeroovee to Rotax mount conversion???

Posted: Thu Jun 08, 2023 10:42 pm

by xeriotti

Skippydiesel wrote:Where did you find the in line coolant thermostat??

Make sure the thermostat back plate has a small pressure relief hole

Those pictures came from the internet… I will buy a random automotive thermostat, and will machine a housing to fit my needs from scratch… Im from Argentina, theres no anything over here… and if it exists…it costs 2 years of salary jajajajaj Thats why everything is scratch built in my projects…im no hero or craftmanship fan… I have no other choice than designing machining trial and error solutions XD

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Jun 09, 2023 3:06 am

by Kai

I was looking to the Vans/Subaru people when choosing my cooling system layout. Like the Eggenfellner layout, it consists of a split radiator setup, the sum og their cooling grid area corresponding to the Rotax recommended radiator size for the R914. Cooling air intake size and position in the cowling is as supplied by Sonex for the Jabiru cowling, with the radiators directly behind these intakes. Cooling air outlet is a full width chute in the bottom of the cowling, as well as the now common side outlet channels.

Each radiator has its own thermostat. I have seen too many cracked cylinder heads in my time, so the one thing I would shy as the plague is a thermostat system that shuts off or restricts coolant flow. The thermostats direct full flow coolant out of the left/right heads either back to the circulation pump, or through the radiators and then back to the pump. To facilitate this I welded up a coolant outlet tower for each bank, taking care to maintain cross sections. I also have a swirl pot and a catch tank in the system.

The thermostats of choice would have been the beauties from the company Silent Hektik in Germany, however, they have a policy not to sell to individuals outside the EU, so I instead selected two BMW V12 thermostats- they are stamped 80C. During climbout I can see the coolant temp temporarily climb to a shade under 90C (intake airflow breakdown?), after which i stabilizes at 70C in cruise. It will remain there whatever I do to it until I am back to the ground.

My propulsion plant is a Sensenich fixed pitch two blade 64x82 prop and the EP915ECI engine- it pumps out 123HP at 5800 rpm. Normally I cruise the thing at 4800-5000 rpm, when I see 120-130 kts on the ASI with a fuel burn of som 16-17 l/hr. The engine has piston cooling, which would mean more heated lubricant than normal for a R912ULS. Therefore the largest 914 oil cooler was selected- it is positioned directly under the lube oil pump. However, contrary to expectations, the setup overcools the oil considerably. There is no room for an oil thermostat anywhere, so I am forced to work with some aluminium sheet air intake restrictions (I can just click them in place). I try to maintain at 85-90C.

What else? I live in a temperate climate. Winter ambient temps are a few degrees below 0, spring/autumn apprx 5-15 C, and summer around 20-25C. We very seldom see 30C.

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Jun 09, 2023 5:38 am

by Skippydiesel

“There is no room for an oil thermostat anywhere, so I am forced to work with some aluminium sheet air intake restrictions (I can just click them in place). I try to maintain at 85-90C.”

Why not reduce the exit air flow instead?

In theory, reducing exit air dimensions, will reduce the air flow to your cooling devices, while accelerating the exit air so reducing drag. The simplest way of doing this is to use a cowl flap flap, fixed, adjustable or pilot controlled.

Where did you get the Rotax Extra Large Oil Cooler (886107) ? How much did it cost? I have been trying to find one for about 6 weeks - so far no joy

Re: Aeroovee to Rotax mount conversion???

Posted: Fri Jun 09, 2023 4:10 pm

by Kai

Naw- what problem would I try to solve?

Besides, the considerable suction present in the cowling IMHO is an insurance: should the worst happen I think it is better with an overcooled engine than an overheated one. The oiltemp is of course an issue, but the real clue lies on the underside of the oil tank filler cap: as long as the hot oil residue on it is not milky white, and the temp stays below 120C, I consider myself in the green.

The dealer network for Rotax in Europe is fairly good: most distributors have a considerable stock of spares and auxiliary equipment. Personally I get my spares from Edge Perormance in Norway and Franz Aero in Germany- perhaps not the first choice for someone living Down Under. And you´re right about the pricing: enough to make you weep!

Re: Aeroovee to Rotax mount conversion???

Posted: Mon Jun 19, 2023 1:59 am

by xeriotti

Coarser prop arriving soon… Dont want to lose my short field and climb capabilities… But that 68x70 is really fine for this airframe