Engine Size Recomendation?
 

I have a 40% sport scale homebuilt kit here. It is a low wing aircraft with side-by-side 2-place seating. It is the Piel Emeraude airplane.

http://www.fly-imaa.org/imaa/hfartic.../v9-3-19a.html

126" wingspan 35-40 pounds RTF. Recommended engine size is 3.1 - 5.2 cubic inches. (50cc - 85cc) I don't build heavy, so let's assume it weighs a maximum of 40 pounds RTF.

I want more than scale performance. I want knife edge performance. Not slow high-alpha knife edge. It's not a 3D plane. I would really like medium to high throttle knife edge performance.

Consider that I fly at 6000 feet and there is about 10% - 15% drop in engine performance here.

What engine would you put in it?

Thanks

RE: Engine Size Recomendation?
 

BME 116 or BME 150LT

RE: Engine Size Recomendation?
 

I'd go with a 140 to 160. 40 pounds is 40 pounds. I know the guy that did the review in High Flight. He's not one to under or over power a plane but he flies at lower elevations.

RE: Engine Size Recomendation?
 

Wow. Thanks guys. I was thinking of going with a 100cc twin or even a 90cc single. But your recommendations of 140-150-160cc have me tossing my initial idea right out the window.

You think 150cc will give good sport power and not unlimited, right? I don't need unlimited.

RE: Engine Size Recomendation?
 

I'm guessing too but here's why I'm guessing this way. A KE pass is the same as a slip. You use a slip to slow a plane for landing. A plane that can barely hover looses speed in a long KE pass. At 40lbs a 150size motor would be needed to maintain a KE pass. At 35lbs a 100 cc class engine should do the trick.
It would be interesting to know if a fullsize top of the line aerobatic airplane can hold a KE pass indefinately. I am pretty sure they couldn't just a few years ago. Not untill they were allowed to hop up the IO 540 over about 330 HP.

RE: Engine Size Recomendation?
 

Nope
Full sized Extra 300 series ("L" configuration) fitted with original IO540 - definitely not
Same plane - retrofitted with Thunderbolt Engine upgrade (330 Hp version of the I0540) and MTV 9-B-C/C200-15 Prop - not indefinitley but certainly for a lot longer.

But then again - it doesn't prop hang, torque roll or have unlimited vertical indefinitley either. Fast rolls around any of the Axes and spins are good fun though :D

Pilot weight - a little over 125kg. - Aerobatic fuel plus about another 20 gallons on top.

RE: Engine Size Recomendation?
 

Me thinks photos 2&3 are of Cap 10's

RE: Engine Size Recomendation?
 

Me thinks you are correct.
But the Piel Emeraude was a predecessor to the 10 (with most similarities stopping at the cosmetic points).

RE: Engine Size Recomendation?
 

Everything is going to depend greatly on the wing loading. If it's in the 36-38 range you might get away with a 120. For true scale the 120 might just do it. For anything beyond scale it will need more engine. Don't forget the density altitude, right? Even with a 120 you're going to need some runway.

RE: Engine Size Recomendation?
 

One of the best "vintage" aerobatic trainers by the way. I used to love the lines of the Cap 10 (full scale) back in the day. Cool airplane!

RE: Engine Size Recomendation?
 

The Emeraude led to the development of the Cap airplanes. Amazing huh? The Mexican Air Force still uses them for training. I am planning to bash mine into a Cap 10B. That explains the desire for more power.

I was thinking a 120 would be pretty snappy, but I really have no idea. 40 pound airplanes aren't something I have ever flown. After asking a couple local friends, seams all the Caps, Yaks, Extra in the 40% size are using 150cc - 170cc engines, some of them are on pipes too. Those do have unlimited power at this altitude.

I'll start looking at 120cc - 170cc engines. Thanks guys. [8D]

RE: Engine Size Recomendation?
 

Happy to help, as always.