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Advice please.

Don Patrick

Well Known Member
I purchased a used engine and prop combo off of a lancair legacy....

The prop is a HC-F2YR-1F with F7496 blades. The prop is an extended hub. The hub protrudes 3.93 inches past where the compact hub does....so essentially, the gap between the front of the cowl and the backplate of the spinner is almost 4 inches.

I have the standard horizontal cowl for the IO-360 parallel valve. I'm fitting it like I have a C2YR hub and once the cowl is finished, im thinking of extending the front of the cowl to the spinner with glass.

I just dont know how it's going to look....

I have the prop listed at Lancair and if it sells, i'll pick up a new prop from vans...if not.....it may or not be used.

Anyone down this path before?

Not interested in a showplanes or SJ cowl either.

Any comments / advice appreciated.

Thanks.
 
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G limit?

Don, I think the extended hub has a lower G limit than the standard. You might want to check with Hartzell. I extended my 7 cowl due to blade clearance. It turned out nice, but it was bit of a pain with all the contours and blending.

An extension might also affect the cooling in climb, as the blade proximity has an effect there. Just be aware of the other unintended consequences.

The easy button is to sell and get a new prop matched to the 8.
 
Don
The G and weight and balance situations are a consideration but if you can resolve that, the modification will depend on your comfort with glass work.
I think it has the potential to look really good as long as you can taper the cowling up to keep a nice profile.
If your engine is mounted, set the cowling top in place and put a foam donut on the front to simulate the new end of the cowling. Lay some long strips of tape back to the cowlings and stand back and admire...
 
Here's what Tom means by lofting with tape. Works for fairings, cowls, wing fabric, all kinds of stuff.



Think about what you want to accomplish, or can accomplish, if you use a prop extension. Personally I'd see it as an invitation to optimize a high Vi/Vo inlet. That's a low Vi/Vo in the above photo. See CR3405.
 
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