Prop model and length options?
Posted: Thu Jun 22, 2017 11:17 am
by mcjon77
Hi guys,
For the Rotax builders and flyers, what propeller length (and model) are you using/planning to use? Also, is anyone planning on lengthening the landing gear an inch or so? I have been considering a 3 blade 64" Warp drive. Truth be told, I am about 2 years away from having to make the decision, though.
Re: Prop model and length options?
Posted: Fri Jun 23, 2017 8:20 am
by SonexN76ET
Anyone who is considering using a Rotax in a legacy Sonex please contact Sonex and request they develop and sell an engine mount for the Rotax. I plan on someday swapping my Aerovee for a Rotax (when I can afford it). I think that if enough of us request a Rotax mount the factory may produce one.
Re: Prop model and length options?
Posted: Fri Jun 23, 2017 9:12 am
by Brett
I’d buy one tommorow if they did…
Re: Prop model and length options?
Posted: Fri Jun 23, 2017 4:34 pm
by garyb
I am still building my Sonex Rotax its at the 90% stage now. I have increased the ground clearance by about 3.5" more than standard and I am using a 68" prop 64" would be okay with standard clearance.
Regards Gary.
Re: Prop model and length options?
Posted: Fri Jun 23, 2017 7:40 pm
by Brett
Hi Gary, will really look forward to seeing your performance figures with that prop and engine combo.
Re: Prop model and length options?
Posted: Fri Jun 23, 2017 11:17 pm
by gammaxy
Sonex told me a about a year ago that 60" diameter is their limit. Measuring from the plans, that looks to give about 9" of clearance without any deflection of the gear. Does anyone currently sell 60" propellers for the Rotax on a Sonex?
I played around with JavaProp to design optimal propellers for the ~2300rpm Rotax and estimated you get ~8% more thrust at Vy when you step up from 60" to 68". The differences in cruise is much smaller, so I imagine you could be happy with the smaller diameter.
Gary’s longer landing gear seems like a good idea to me, something I’d strongly consider for larger propellers.
14 cfr 23.925 says:
(a) Ground clearance. There must be a clearance of at least seven inches (for each airplane with nose wheel landing gear) or nine inches (for each airplane with tail wheel landing gear) between each propeller and the ground with the landing gear statically deflected and in the level, normal takeoff, or taxing attitude, whichever is most critical. In addition, for each airplane with conventional landing gear struts using fluid or mechanical means for absorbing landing shocks, there must be positive clearance between the propeller and the ground in the level takeoff attitude with the critical tire completely deflated and the corresponding landing gear strut bottomed. Positive clearance for airplanes using leaf spring struts is shown with a deflection correspondingto 1.5g.
Re: Prop model and length options?
Posted: Sat Jun 24, 2017 12:52 am
by WaiexN143NM
Hi all,
Who was posting a year ago about using a custom ring mount to convert from an aerovee mount to a rotax mount? Is that you gary?
Thanks chris for always good info posts.
WaiexN143NM
Michael
Re: Prop model and length options?
Posted: Sat Jun 24, 2017 2:25 am
by mcjon77
SonexN76ET wrote:Anyone who is considering using a Rotax in a legacy Sonex please contact Sonex and request they develop and sell an engine mount for the Rotax. I plan on someday swapping my Aerovee for a Rotax (when I can afford it). I think that if enough of us request a Rotax mount the factory may produce one.
The engine mount issue was one of my biggest concerns. When they came out with the B model conversion kit and I looked at the features (including a rotax engine mount option) I have decided to go that route. I will probably order the b conversion kit next year.
Re: Prop model and length options?
Posted: Sat Jun 24, 2017 7:57 am
by Concorde
SonexN76ET wrote:Anyone who is considering using a Rotax in a legacy Sonex please contact Sonex and request they develop and sell an engine mount for the Rotax. I plan on someday swapping my Aerovee for a Rotax (when I can afford it). I think that if enough of us request a Rotax mount the factory may produce one.
We have tried that for many years with no luck …
Re: Prop model and length options?
Posted: Sat Jun 24, 2017 3:56 pm
by garyb
WaiexN143NM wrote:Hi all,
Who was posting a year ago about using a custom ring mount to convert from an aerovee mount to a rotax mount? Is that you gary?
Thanks chris for always good info posts.
WaiexN143NM
Michael
Check this post out
viewtopic.php?f=60&t=579
bishoff7 was making an adaptor from Aerovee mount to Rotax
Cheers
Re: Prop model and length options?
Posted: Wed May 02, 2018 5:06 pm
by pschwenn
I’ve ordered a propeller for the 912iS Sport I’m installing. Its an Helice E-Prop Durandel 100 (it would be a 155cm or 160cm Durandal 100 Model S on Sonex or Waiex (faster planes than my Xenos which will be a Model M 165cm [given slicker wheel pants a 2 inch taller tire will give you another 10cm prop diam without slowing you down]).
It’s three blade solid composite ground-adjustable. The attraction of the Durandal propellers is that the shape, thickness and very short chord-length are such that is not (simplifying) near stall over a wider regime (climb, cruise, speed, altitude) than a conventional solid propeller. And since it is ground adjustable one starts out at your chosen regimes center point. For an Aerovee 80hp it would be a Durandal 80. The supporting documentation, test results and testimonials are more convincing and simpler than other wonder props and the concept is very simple.
Price is about $1600 against $4000 - $10000 for an in flight adjustable or constant-speed, and its weight is very low because it IS a solid composite prop (with inconel(?) )protection on the leading edge.
Matching carbon extensions and spinners are available.
I will report when I finish installation.
Re: Prop model and length options?
Posted: Sat Dec 01, 2018 3:33 am
by Brett
Has anyone flown behind the Sonex recommend prop for the Rotax 912 ?
From the website they recommend the WC64QR-81G
Thanks…
Re: Prop model and length options?
Posted: Sun Jan 06, 2019 5:56 am
by Brett
Perhaps a better question would be is anyone considering using the recommended Rotax prop for the 912 in the future?
Or knows of anyone flying behind it?
Re: Prop model and length options?
Posted: Sun Jan 06, 2019 7:59 am
by Concorde
Brett wrote:Perhaps a better question would be is anyone considering using the recommended Rotax prop for the 912 in the future?
Or knows of anyone flying behind it?
I bought the 64” prince p tip but haven’t install it yet . My 912 uls arrived before Christmas so I am trying to figure everything out . I have a tri gear Sonex and according to Sonex with standard tires I should have 6”of ground clearance. I am thinking about larger tires but I will wait and see.
Re: Prop model and length options?
Posted: Thu Sep 24, 2020 9:34 am
by Zack
Any updates?
Re: Prop model and length options?
Posted: Thu Jan 05, 2023 5:33 pm
by Murray Parr
Does anyone have performance numbers (static rpm etc) for the early sensenich props sold by Sonex for the Rotax 912 100hp engines? The number was WC64QR-81G I believe. It would also be interesting to compare figures with the smaller diameter WC60QR-82G they sell now.
Re: Prop model and length options?
Posted: Sun Feb 12, 2023 7:42 am
by Murray Parr
I’ll go first. Static runup for the early version Sensenich prop WC64QR-81G is 4900 RPM for my Rotax 912 ULS. Anyone else have any comparisons?
Re: Prop model and length options?
Posted: Sun Feb 12, 2023 8:08 am
by GraemeSmith
Murray Parr wrote:I’ll go first. Static runup for the early version Sensenich prop WC64QR-81G is 4900 RPM for my Rotax 912 ULS. Anyone else have any comparisons?
Check my math.
4900rpm - Reduction gearbox 2.43:1 = 2,016.46090 rpm
x 60 = 120,987.654 rp HOUR
64" diameter propeller. Circumference = Pi * D = 201.0619 inches
Circumference x rpHour = 24,326,011 inches per hour
Which equals a blade tip speed of 774mph
Must have been INCREDIBLY noisy - as well as inefficient.
–
With the 60 inch diameter prop we are in the realms of 726 mph
Still seems excessive.
–
What did I miss?
Re: Prop model and length options?
Posted: Sun Feb 12, 2023 8:26 am
by Area 51%
I’m getting 384 mph tip speed with my math.
64" diameter X Pi = 201in. X 2016rpm = 405,216 inches per minute X 60 minutes = 24,312,960 inches per hour divided by 12 = 2,026,080 feet per hour divided by 5280 = 383.73mph.
Re: Prop model and length options?
Posted: Sun Feb 12, 2023 8:53 am
by GraemeSmith
Area 51% wrote:I’m getting 384 mph tip speed with my math.
64" diameter X Pi = 201in. X 2016rpm = 405,216 inches per minute X 60 minutes = 24,312,960 inches per hour divided by 12 = 2,026,080 feet per hour divided by 5280 = 383.73mph.
And I agree!
For the life of me I can’t see where I was out by a factor of 2. It’s not like 2 is even a number in the calculation to be screwed up. And I did it twice coming at it from either end. We need emoticons on this site so I can post a 
one…
Re: Prop model and length options?
Posted: Sun Feb 12, 2023 9:43 am
by Area 51%
You were probably using the equation for a 4-bladed propeller. I did my math based on a two paddle thruster.
Re: Prop model and length options?
Posted: Sun Feb 12, 2023 3:38 pm
by Murray Parr
Rotax recommends to aim for 5200 rpm static, I’m still 300 shy of that. Not sure if the engine is weak or if it is over propped or a combination of both. Everything checks out with the engine compression wise, most components like plug wires etc have been replaced, the engine has been out of service sinse 2016 and appears it was running without issues when it was removed.
I was hoping for a comparison with someone else that has this prop/engine combo but Sonex/Sensenich didn’t sell this prop for very long.
Re: Prop model and length options?
Posted: Mon Feb 13, 2023 6:23 pm
by Skippydiesel
Hi Murray,
Cant help with the prop question you posed however advise - if not already done, double check the engine/prop RPM read out before going any further. Its not unusual for instrument error to be the real issue.
Re: Prop model and length options?
Posted: Mon Feb 13, 2023 6:43 pm
by Murray Parr
Skippydiesel wrote:Hi Murray,
Cant help with the prop question you posed however advise - if not already done, double check the engine/prop RPM read out before going any further. Its not unusual for instrument error to be the real issue.
That thought has crossed my mind but I don’t have any means to check it against. Having said that, are there any errors possible with the simple Hall effect sensor (that Rotax uses for tach readings) counting pulses?
Re: Prop model and length options?
Posted: Mon Feb 13, 2023 7:52 pm
by GraemeSmith
Murray Parr wrote:That thought has crossed my mind but I don’t have any means to check it against.
Digital Laser tach. Point it at the prop blades. It counts them.
https://www.amazon.com/AGPtek%C2%AE-Pro … 221&sr=8-3
Hall Effect / Tach. Should be reliable but poor/intermittent grounding or borderline sensitivity in the EFIS can give false readings.
Re: Prop model and length options?
Posted: Tue Feb 14, 2023 12:21 am
by Murray Parr
GraemeSmith wrote:
Murray Parr wrote:That thought has crossed my mind but I don’t have any means to check it against.
Digital Laser tach. Point it at the prop blades. It counts them.
https://www.amazon.com/AGPtek%C2%AE-Pro … 221&sr=8-3
Hall Effect / Tach. Should be reliable but poor/intermittent grounding or borderline sensitivity in the EFIS can give false readings.
Thanks Graeme, I ordered one. It will be interesting to see if my tach is accurate
Re: Prop model and length options?
Posted: Tue Feb 14, 2023 1:02 am
by Brett
WC64QR-81G is the prop I’m running atm. Definitely over propped. I sent all the data to Sensenich early in the piece along with flight data of the aerovee turbo prob for comparison. I never heard back from Sensenich but few weeks later saw the recommendation for the Rotax props changed on their website.
I get fantastic cruise speeds but climb is not so great.
Re: Prop model and length options?
Posted: Tue Feb 14, 2023 1:38 am
by Murray Parr
Brett wrote:WC64QR-81G is the prop I’m running atm. Definitely over propped. I sent all the data to Sensenich early in the piece along with flight data of the aerovee turbo prob for comparison. I never heard back from Sensenich but few weeks later saw the recommendation for the Rotax props changed on their website.
I get fantastic cruise speeds but climb is not so great.
Thanks for the info Brett,
What static RPM and WOT level cruise RPM is typical for your setup?
Re: Prop model and length options?
Posted: Tue Feb 14, 2023 9:52 am
by 13brv3
Murray Parr wrote:Rotax recommends to aim for 5200 rpm static, I’m still 300 shy of that. Not sure if the engine is weak or if it is over propped or a combination of both.
I’ve seen the 5200 rpm recommendation, but that would overspeed at cruise on a relatively fast plane. My Warp Drive prop is pitched such that it gives me around 4900-5000 static. That unloads to 5100 in a normal climb, and will still exceed the max continuous 5500 in level flight below about 5000 ft.
It sounds like you’ve ruled out any significant issues with the engine, so likely this is just normal for that prop, and maybe why they quit selling it. If you really want a comparison, maybe find someone with a 912ULS who would test the prop.
Once you verify the tach, which I’m sure will be accurate, I think I’d press on with completion and see what sort of rpms you get once you’re flying. You might also want to contact Senenich, since they worked with Sonex and probably had contact with any of their customers who actually ran the prop on a 9112ULS. I’d bet they keep records of reported performance. They will also be the ones who can give you the best advice now, and after it’s flying. If you really want 5200 static, they can probably trim the prop a couple inches.
While I love ground adjustable props, I’d also love to test the 60 inch Sensenich that Sonex is selling now. I think it would likely outperform the Warp Drive.
Rusty
Re: Prop model and length options?
Posted: Tue Feb 14, 2023 5:47 pm
by Brett
I’ve not tied it down for WOT with this engine.
Climb out regularly 95-100kts IAS 4700-4800rpm solo 1000fpm average. Dual full fuel never less than 600+ .
5250 rpm - 5300 max rpm level flight.
Most days I cruise anywhere between 4600- 5100rpm depending on where I’m going and how much fuel I want to use. 4800-4900 rpm usually indicates 120kts on an average day. Better in winter. I flight plan 125kts Tas for conservative figures in regard to fuel.
Re: Prop model and length options?
Posted: Wed Feb 15, 2023 2:47 am
by Murray Parr
Thanks for all the responses.
I received a bit of guidance from Sensenich too, here is the response I got from them with me telling them the static of 4900rpm.
I would do a high speed run down the runway.
Propeller should unload to about 5200 rpm during takeoff roll.
If it does that, I would expect the propeller to unload to 5600 – 5700 FLTF (full throttle level flight.
Can’t really change the pitch on a fixed pitch wood propeller.
It could be trimmed in diameter.
Each 2 inches of diameter reduction will get you another 75 rpm in static and about 125 rpm FTLF
It looks like I might be in the ball park of what Brett is seeing so I am about to rule out anything wrong with the engine, will do another leakdown test soon.
Another thing I might do in the future is put a big bore kit in the engine to get the power up to 114hp, yes I know, I am a tinkerer… and who ever said more power sucks!!!
Re: Prop model and length options?
Posted: Wed Feb 15, 2023 5:42 pm
by Skippydiesel
Just a word on the “Digital Laser tach” -
Mine , which looks very much like the one Graeme recommended, does not work well in strong light. Pick a dull day, early/late or undercover, to do your testing.
It takes two people to do the readings - one in cockpit “driving” (must aim for nice steady engine RPM) and one operating the Laser.
I used masking tape on the cowling to mark the best location, so as to place the “machine” in close proximity to the prop.
I also had to mask my nice shiny spinner & any shiny “bits” on the prop root, as reflections seemed to interfere with the readings.