STi propellor: CS or ground adjustable? Duc windspoon?

[dothedr3w]

Hey everyone,

I'm brand new to this forum and my kitfox journey. This place is such an awesome resource that I'm really looking forward to leveraging more once my build actually begins...years from now unfortunately.

I've been seeing a bit of conflicting info over the benefits of a constant speed over a ground adjustable prop with an STi wing. As I understand things, the STi hits a bit of a drag wall around 100, and can't truly take advance of a CS.

The plan thus far is is run an Airmaster powered by an Edge EP912STI. The hydraulic MT doesn't appeal to me because of cost/weight, and I'm not even sure the edge engine supports it.

What the general consensus on this forum? Is there a reasonable argument for better overall performance using a ground adjustable given the weight savings and better prop choices? Does anyone have any experience or opinion of the DUC Windspoon?

http://www.duc-propellers-usa.com/rubrique.php?id_rubrique=46

Cheers!

[Shadowrider]

Hey! Welcome! I have not heard of anyone running the Duc windspoon prop on a STI with a turbo engine? Curious what info you have or what DUC is saying about the prop? Yes the STI does hit a drag wall around 100mph so the advantages of going faster at cruise having a CS is not being seen as much as with the 7SS. Part of the problem is those with the STI wing, usually have the 29" tires, shock monster gear so already very draggy. You start throwing more power and you just increase fuel burn and not much speed improvement. I have different opinions on a CS depending on what engine and what your trying to do? The 915is is a better engine suited for a constant speed because it has a beefier gearbox and crank. The EP912STI I prefer a ground adjustable prop. Running a fix pitch prop you can't load the engine up in cruise and put a lot of stress on the gearbox but mostly the crank because you will hit rpms long before. In cruise at 5200-5400 rpms I am usually less than 30" of manifold. Here is my plug for the NR prop. The NR prop has been awesome performance and cruise. Takeoff under 100' cruise at 105-110. Climb 1800'. (I am at 5000msl also). And the NR prop and spinner is under $1500.