Prop model and length options?

[Area 51%]

You were probably using the equation for a 4-bladed propeller. I did my math based on a two paddle thruster.

[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.

[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.

[Murray Parr]

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?

[GraemeSmith]

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.

[Murray Parr]

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

[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.

[Murray Parr]

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?

[13brv3]

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

[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.