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
Posted: Sun Feb 12, 2023 9:43 am