WARP DRIVE: Square or Taper Tip

[SkySteve]

OK, boys and girls, I need your input. I'm currently running a 3 blade square tip WD in front of my 912 80 hp Rotax, but I'm thinking very seriously about sending the blades to WD to have them cut the blades into Taper Tips and add Nickel leading edges. I'm thinking I'll get higher RPMs for stronger/shorter take off and an increase in cruise as well. Am I thinking smart or foolish? Let the opinions roll ...

[Av8r3400]

From everything that I have read, a 68", three blade, square tip, Warp Drive prop exceeds the MMOI* rating on a Rotax gearbox. Tapering the tips, including the nickel edge, brings it back to the acceptable, yet still at the max, rating.


*MMOI - Mass Moment of Inertia.

http://www.aviasport.com/Rotax/Docum...les/11ul91.pdf

http://www.eaavideo.org/video.aspx?v=2010764613001

[Dave S]

Steve,

FWIW - I have used a tapered tip nickle edge warp from the beginning on our plane - and, the nickle edge has done quite well for durability.

The Nickle edge was primarily designed for float planes to reduce the erosive effects of water spray on the prop - I ended up with the nickle edges simply because it came with the prop I got - but I do like it - so far no nicking or dents other than inconsequential/minor.

Sincerely,
Dave S
KF 7 Trigear

[WWhunter]

What are your thoughts on a 2-blade verses 3-blade?
Reason for the inquiry is I had a 2 blade Warp Drive taper tip on my 912 but it seemed to have a high frequncy 'buzz/vibration' at higher RPM. I got very good performance from the prop but changed out to a 3-blade.
Now that I have a Kitfox that needs a prop I was thinking of using it due to everyone's suggestion to sh!tcan the GSC.

[SkySteve]

When I was looking for a new prop several years ago my A&P told me I would get better performance (for my application) from a three blade. It has done a great job. I fly with a guy who flies a Bearhawk with a 2 blade. He has just changed over to a 3 blade MT prop. Most of our landings/take offs are off airport.

[WWhunter]

Steve, I have heard both sides of the 2-blade/3-blade arguement. Generally floatplane guys say that a 2 blade has more 'pull' and the 3-blade guys states smoother running and more speed due to less disk area. Heck, I am a lowly GA guy that is just in search of more info.
I know I did lose a little in T/O performance when I went to a 3 blade but, oh....my engine is so much smoother now. The difference wasn't huge but definitely noticable.
The other reason I swapped out was the fact that I will be installing the floats (eventually) and need a prop for seaplane use. The Warp, although a taper tip, was without the leading edge protection. I bought a Whirlwind with nickle leading edge and am happy with it on my RANS.
The WD is like new with very few hours on it so I may as well find a use for it. I'd lose too much trying to resell it.

[SkySteve]

WWhunter,
I have heard both sides of the same argument, too. I am NOT a prop guy nor an engineer so I have no idea what the truth is. My best guess is...it depends. That's why I just went with what my A&P said. I'm happy. Still rather ignorant, but happy.

[jrevens]

Theoretically, the fewer the number of blades the greater the efficiency. I think it has to do mainly with how much "disturbed" air each blade encounters from the blade that precedes it. It was well known by model builders that the most efficient set-up was a single blade prop with a relatively small counterweight on the other side of the hub. There are many other considerations of course. Propeller ground and/or structure clearance while still being able to utilize existing horsepower is one issue. I believe that under ideal conditions and everything else being equal, the best 2-bladed prop for a particular situation will outperform the best 3-bladed one based strictly on available thrust. I'm going to use a 3-blader for esthetics, ground clearance, and perhaps some other minor benefits.

[SkySteve]

John,
Your point about ground clearance is probably one my A&P was considering as I am flying a tri gear off airport.

So, any additional opinions regarding the Square tip vrs the Taper tip? Going, going, almost gone.

[JimS]

I'll jump in with my 2 cents.
Updated my Model 4 to a 80 HP UL with the wide tip Warp (replaced my 582). Had a vibration I didn't like from about 4000rpm on up and then I read an artical by Paul Lipps (?) where he detailed the lost performance of wide tips on props. (Reno racers run a lot of his props). Anyway, I sent mine back to Warp, had the tips tapered, got rid of 80 % of that nasty vibration, and got a bit better performance to boot.
JimS