Rotax Propeller

[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

[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

[xeriotti]

Any information on Static RPM, WOT straight and level, climb and cruise with the reccomended 60x82 Sensenich propeller?

[Skippydiesel]

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.

[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?

[Skippydiesel]

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?

[xeriotti]

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?

[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.

[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

[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