Rotax Propeller
Posted: Sat Jul 15, 2017 12:45 pm
by Paul Johnson
Good news that Sonex is now going to supply Rotax engine mounts for their legacy aircraft. The Sonex web site now list a Sensenich propeller for Rotax engines It’s model number is WC64QR-81G, from this I take it to be 64" diameter, will longer gear legs be needed for this propeller and if so who will be supplying them as this would effect the B model as well?
Re: Rotax Propeller
Posted: Sat Jul 15, 2017 3:09 pm
by Concorde
I spoke with Mark the other day and he said the 64" prop is fine with both tri gear and tail wheel ,but I forgot to ask if we need 3 blades or 2.
Re: Rotax Propeller
Posted: Mon Jul 17, 2017 10:25 am
by markschaible
Hello SonexBuilders.net,
The Sensenich prop for Sonex/Rotax is a two blade, composite coated propeller. Longer gear legs are not needed.
Regards,
-Mark
Re: Rotax Propeller
Posted: Mon Jul 17, 2017 3:52 pm
by Concorde
Mark,
I spoke with the Rockwood aviation tech today before seeing your post and he suggested to go with 3 blades. Can you please tell us the benefit of 2 vs 3 blades or it doesn’t really matter which to get.
P.s. The person that I spoke to is thinking about ordering a Waiex.
Thanks
Ben
Re: Rotax Propeller
Posted: Mon Jul 17, 2017 9:42 pm
by rk2436
Most 2 blade Rotax props are 70". Probably no ground clearance at that length on the Sonex. Go with the 3 blade and don’t leave torque on the ramp. You will like the 912uls it’s far superior to all the other choices and no worries about Chinese parts holding your butt up in the air. Bob K
Re: Rotax Propeller
Posted: Tue Jul 18, 2017 11:07 am
by jeff0196
I have a 912 UL in my AVID MK4. It is a great little engine from my very limited experience of 50 hrs since October last year, with 320 total time on the engine. I just wanted to point out that the moment of inertia/rotational inertia is limited by Rotax for the 912’s. Rotax installation manual limits the moment of inertia to 6000 kg cm2 (14.238 lb ft2) for the propeller. You can buy propellers that fit the Rotax and exceed this limit. Large diameter propellers can have high moment of inertia even if designed light. Small diameter 3 blades that are designed light are great compromise. I would personally make sure any propeller I put on my Rotax was within the moment of inertia limit. As long as I’m posting, Rotax also limits prop extensions to 120mm (4.72inches) or less.
Re: Rotax Propeller
Posted: Tue Jul 18, 2017 5:23 pm
by markschaible
Hi Folks,
We always prefer to use 2-blade props to play to the strengths of our clean & fast airframes. 2 blade props minimize cost, maximize reliability, minimize balancing issues, and optimize the performance envelope at both ends of the spectrum with the superior flexibility performance characteristics of wood or wood-core props. You’ll have plenty of torque for takeoff and climb performance with the Rotax and the recommended Sensenich prop, which will also help you to maximize the speedster characteristics of our airframe at the top end as-well. Sensenich has a ton of experience engineering propellers and they have a huge database of both Sonex Airframe and Rotax engine performance characteristics – we put our trust in Sensenich fully to come-up with the best prop for the job that is best-suited to this engine and airframe combination.
Regards,
-Mark
Re: Rotax Propeller
Posted: Tue Jul 18, 2017 7:40 pm
by Concorde
Thank you.
Re: Rotax Propeller
Posted: Tue Dec 17, 2019 1:21 pm
by Paul Johnson
Paul Johnson wrote:Good news that Sonex is now going to supply Rotax engine mounts for their legacy aircraft. The Sonex web site now list a Sensenich propeller for Rotax engines It’s model number is WC64QR-81G, from this I take it to be 64" diameter, will longer gear legs be needed for this propeller and if so who will be supplying them as this would effect the B model as well?
The Sonex web site has been updated, the Sensenich propeller recommended for Rotax engines is now model number WC60QR-82G, from this I take it to be 60" diameter.
Re: Rotax Propeller
Posted: Sun May 09, 2021 1:59 am
by Kai
For those of you that use a fixed pitch or ground adjustable prop on the Sonex A with a R912ULS.
What is your wot ground static rpm?
And at what ambient pressure and temperature did you perform the test?
And how much does the wot cruise rpm increase at say some 3000’ agl?
Thanks
Kai
Re: Rotax Propeller
Posted: Sat Sep 18, 2021 2:36 am
by Skippydiesel
Your thoughts on :
Airmaster, CS, Whirlwind 3 blade, motivated by Rotax 912 ULS
Further details can be found: https://www.propellor.com/airmaster-factory
Look under Rotax 912 ULS recommendations for propeller details
Re: Rotax Propeller
Posted: Sun Sep 19, 2021 2:22 am
by Kai
Question:
I have tried to figure out how far ahead of the cowling front, the trailing edge of the (Sensenich) prop needs to be. So far it seems I might be a little short of the ideal.
Is a distance of 1/4” enough to maintain prop efficiency? Or should it be more?
Mark?
Thanks
Kai
Re: Rotax Propeller
Posted: Thu Aug 11, 2022 5:04 am
by xeriotti
Any information on Static RPM, WOT straight and level, climb and cruise with the reccomended 60x82 Sensenich propeller?
Re: Rotax Propeller
Posted: Sat Aug 13, 2022 7:33 pm
by Skippydiesel
xeriotti wrote:Any information on Static RPM, WOT straight and level, climb and cruise with the reccomended 60x82 Sensenich propeller?
Static RPM, as advised/recommended by Rotax, should be 5200 RPM. This recommendation does not vary with propeller manufacturer or model.
If you apply the above recommendation, most propellers will overspeed at WOT, when straight & level, unless infight/CS capable.
Those that use WOT, to set their prop pitch, will be compromising climb out performance, may be overstressing the engine and ultimately reducing their safety margins during climb out from a marginal field.
Re: Rotax Propeller
Posted: Sun Aug 14, 2022 12:22 pm
by Kai
Yes,
A fixed pitch prop on a Sonex/Rotax combo can certainly make you wonder.
I have a fp Sensenich 62x82 on my own rig. Wot static ground 38 ft asl reads 5050 rpm/29.92 inHg (efi engine- no venturi/carby). Wot 3000 ft asl reads 5550 rpm/25 inHg. This would indicate that the rpm span is close to 500. So if I hang on something that indeed makes 5200 rpm wot static ground, I would end up with 5700 rpm wot 3000 ft asl. Still 100 rpm to go before Rotax says no more- right?
Since I can`t use one of the (heavy) CS props available for the engine, I am presently looking for a GA 2 blade thing.
Suggestions?
Re: Rotax Propeller
Posted: Sun Aug 14, 2022 7:02 pm
by Skippydiesel
Kai wrote:Yes,
A fixed pitch prop on a Sonex/Rotax combo can certainly make you wonder.
My observation/understanding is that most Sonex/Rotax9’s run a fixed/ground adjust prop
I have a fp Sensenich 62x82 on my own rig. Wot static ground 38 ft asl reads 5050 rpm/29.92 inHg (efi engine- no venturi/carby). Wot 3000 ft asl reads 5550 rpm/25 inHg. This would indicate that the rpm span is close to 500. So if I hang on something that indeed makes 5200 rpm wot static ground, I would end up with 5700 rpm wot 3000 ft asl. Still 100 rpm to go before Rotax says no more- right?
If you say so - my personal experience (not Sonex) is what I said previously.
Since I can`t use one of the (heavy) CS props available for the engine, I am presently looking for a GA 2 blade thing.
If you want a CS/In Flight Adjust prop, there are quite a few offerings out there - mostly European and also New Zealand weight varies from about 7-11 kg both 2 & 3 blade
Suggestions?
Re: Rotax Propeller
Posted: Sun Aug 14, 2022 9:36 pm
by xeriotti
Kai wrote:Yes,
A fixed pitch prop on a Sonex/Rotax combo can certainly make you wonder.
I have a fp Sensenich 62x82 on my own rig. Wot static ground 38 ft asl reads 5050 rpm/29.92 inHg (efi engine- no venturi/carby). Wot 3000 ft asl reads 5550 rpm/25 inHg. This would indicate that the rpm span is close to 500. So if I hang on something that indeed makes 5200 rpm wot static ground, I would end up with 5700 rpm wot 3000 ft asl. Still 100 rpm to go before Rotax says no more- right?
Since I can`t use one of the (heavy) CS props available for the engine, I am presently looking for a GA 2 blade thing.
Suggestions?
Whats your numbers in… climb, cruise (and rpm please) and max (and rpm too)
Whats the best performing Rotax 100hp Sonex/Waiex you know about? What numbers should i be aiming for?
Id really love to climb 2000fpm solo With fuel… and i would also like to see 150mph cruise at sea level. You think its possible?
Re: Rotax Propeller
Posted: Mon Aug 15, 2022 3:28 am
by Kai
The two Sonex Legacy/Rotax912ULS combos I have flown, both had modified engines, so I can´t really comment.
The first one was the prototype Edge Performance engine and had a 914 with efi, turbo, CS prop, and intercooler. It cranked out something around 135HP. Best climb was well in excess of 2000 ft/min, and easily did 155 kts level on the ASI flat out at 3000´msl. If you have the weight reserve, a CS prop is a terrific boost on the Sonex!
My own engine is a bigbore Edge Performance 915ECI. It did 123 HP/5800 rpm on the dyno. Sadly my fp Sensenich 62x82 prop will not let the engine turn faster than 5550 rpm level wot at 3000´ft, when TAS is 152 kts (the ASI showet something like 148 kts). Best climb flat out is some 1500 ft/min at 5200 rpm.
There is no question about it: my present prop is not ideal for my combo. I would love a CS unit, but EW CG is at 20% chord- the forward limit. A heavy prop up front would mean more weight in the tail, which is a no-no.
Re: Rotax Propeller
Posted: Mon Aug 15, 2022 12:49 pm
by xeriotti
Thanks for sharing! Im really tempted to try a longer propeller once its ready, longer legs and 500x5 tyres may be needed but that longer propeller gives more static thrust and climbing performance… The sweet spot i think its a matter of trying a couple blades.
CS propr are really expensive but undoubtably the way to go
Re: Rotax Propeller
Posted: Mon Aug 15, 2022 5:29 pm
by garyb
Hi
My Rotax powered Sonex has a 68 inch wooden GT propeller off a Tecnam P2008 .Static rpm is around 5100, Solo it climbs sea level at 1800 fpm at 70 kts, cruise 2500’ 120 kts 5200 rpm and 5500 135 kts WOT it pulls to the red line 5800 rpm. The prop could probably do with a little more pitch.
Cheers
Re: Rotax Propeller
Posted: Mon Aug 15, 2022 11:22 pm
by Skippydiesel
garyb wrote:Hi
My Rotax powered Sonex has a 68 inch wooden GT propeller off a Tecnam P2008 .Static rpm is around 5100, Solo it climbs sea level at 1800 fpm at 70 kts, cruise 2500’ 120 kts 5200 rpm and 5500 135 kts WOT it pulls to the red line 5800 rpm. The prop could probably do with a little more pitch.
Cheers
Sounds as close to perfect as you can expect, with a fixed pitch prop.
There is a French propeller maker E-Prop (https://www.e-props.fr/) that seems to have an enthusiastic following here in Australia. Claims of a new approach & great efficiency improvements.
Re: Rotax Propeller
Posted: Tue Aug 16, 2022 2:21 am
by xeriotti
garyb wrote:Hi
My Rotax powered Sonex has a 68 inch wooden GT propeller off a Tecnam P2008 .Static rpm is around 5100, Solo it climbs sea level at 1800 fpm at 70 kts, cruise 2500’ 120 kts 5200 rpm and 5500 135 kts WOT it pulls to the red line 5800 rpm. The prop could probably do with a little more pitch.
Cheers
Gary!! Thats great info!!! Are you aware of the pitch of that propeller? If its not explicit in the model… Maybe we can decode it from your serial number. The other way is to measure the angle at 75% of the radius. But its a tricky task (much more tricky if installed on the plane!)
How fast is your level flight at 5800 WOT? And what fuel consumption are you seeign at your 120kt 5200rpm cruise?
PS: Those numbers are amazing… I think i went the right way with the 912…
Re: Rotax Propeller
Posted: Tue Aug 16, 2022 2:34 am
by xeriotti
Skippydiesel wrote:
garyb wrote:Hi
My Rotax powered Sonex has a 68 inch wooden GT propeller off a Tecnam P2008 .Static rpm is around 5100, Solo it climbs sea level at 1800 fpm at 70 kts, cruise 2500’ 120 kts 5200 rpm and 5500 135 kts WOT it pulls to the red line 5800 rpm. The prop could probably do with a little more pitch.
CheersSounds as close to perfect as you can expect, with a fixed pitch prop.
There is a French propeller maker E-Prop (https://www.e-props.fr/) that seems to have an enthusiastic following here in Australia. Claims of a new approach & great efficiency improvements.
Skippy… I live in Argentina, importing anything nowadays is almost impossible… Super restrictive laws and my country is ranked 3rd in the world for inflation… Im the representative in Argentina for AERO Propellers from Ukraine 
But theres no way to get anything from there because of the war. Im also a collaborative and im kinda sponsored by a local Custom propeller manufacturer thats been making great propellers im currently running in all my airplanes… (Outperforming in every case Every known brand of ground adjustable carbon fibre props)
A ground adjustable propeller has ONE sweet spot… where all the blade has the optimum angle of attack. When a custom propeller is made, the entire blade has the optimal angle of attack for a given airspeed and prop rpm… So when you aim for static thrust (stol applications) climb (maybe the allround everyone is using) or cruise (for cross country or high altitude performance applications) The whole blade is tuned for that specific mission.
It takes decision… Where you want your performance, calculations… and sometimes a couple trial and errors… But once youre done. Its cheap, light and a great performer.
Having a good solid starting point saves calculations, and lots of wood chips flying in vain… So thanks a lot for giving me that information, for me its literally precious.
PS: Once the “purrrrfect” propeller is done, I could even ship wolrdwide 
Re: Rotax Propeller
Posted: Tue Aug 16, 2022 6:10 am
by Skippydiesel
Xeriotti - sound like you are onto a winner. Have you looked at the E-Prop - also carbon fibre sculpture (there is even a CS version that weights a comparative nothing)
Re: Rotax Propeller
Posted: Tue Aug 16, 2022 8:39 am
by xeriotti
Im going for a wooden fixed pitch now… If i really like the plane, i may end up with a constant speed in the future. But as i told you before those are not cheap or easy to get over here
Re: Rotax Propeller
Posted: Tue Aug 16, 2022 9:53 am
by 13brv3
I was looking at the Sensenich prop that Sonex sells for the 912ULS, and I can’t find anything like it on the Sensenich site. Sensenich sells a 2 and 3 blade for the 912 series, but they’re both ground adjustable. The 2 blade shows a diameter of 66-75 which is much larger than the 60" (presumed from the model number) prop on the Sonex page. Is this something Sonex has custom made? It’s really hard to believe a 2-blade 60" prop is enough.
Rusty
Re: Rotax Propeller
Posted: Tue Aug 16, 2022 1:45 pm
by xeriotti
13brv3 wrote:I was looking at the Sensenich prop that Sonex sells for the 912ULS, and I can’t find anything like it on the Sensenich site. Sensenich sells a 2 and 3 blade for the 912 series, but they’re both ground adjustable. The 2 blade shows a diameter of 66-75 which is much larger than the 60" (presumed from the model number) prop on the Sonex page. Is this something Sonex has custom made? It’s really hard to believe a 2-blade 60" prop is enough.
Rusty
Not any written information… But Ive been investigating and watching lots of videos. Sonex Aircraft it self in some interviews talked about a 64X78 then more recent videos Ive heard 62X80 and the latest mention on propellers for a Rotax 100hp powered Sonex/Waiex came from the One Week Wonder build in Oshkosh22… Where someone mentions it spins a 60x82 propeller.
That may be the way the factory took to keep propeller clearance safe and to dont change the aesthetics of the plane too radically (I personally love how a long leeged sonex looks) ,
According to experience almost every Rotax powered Sonex/Waiex ive seen sports 2 and 3 bladed propeller between 64 and 69 inches with apparently good results.
In my experience, long propellers are always better. I dont mind lenghtening the landing gear legs, and switching to bigger tyres, i can create prop clearance. I would be aiming for best performance possible.
Re: Rotax Propeller
Posted: Tue Aug 16, 2022 2:20 pm
by 13brv3
On my 912UL Onex, I’m running a 3 blade 60", because that still only gives me about 4" of prop clearance even with the larger tires. At only 80 HP, I’m still running a fairly high pitch. I’ve tried the square, and taper tip Warp Drive, and also a medium Ivo. So far, the tapered Warp Drive has been the best. I’m pretty happy with the performance for now, but I can certainly see a higher HP Rotax and better prop in my future.
Rusty
Re: Rotax Propeller
Posted: Tue Aug 16, 2022 2:29 pm
by xeriotti
Here it is… at 6minutes 58 seconds…
Re: Rotax Propeller
Posted: Tue Aug 16, 2022 3:13 pm
by 13brv3
Thanks for the link. I don’t see how that prop isn’t stalled at lower speeds.
Rusty
