Question for you engine gurus...

I am scratch building a 10 ft Lavochkin LA-7 and the spinner is 7.25" in diameter. With a spinner that large, I figure less prop is cutting through the air, thus less load on the engine...? Am I right? If so, can I go a little larger in prop size to compensate for the spinner??

This is very important because the cowl is 15" in diameter and I want to maximize thrust for a plane predicted to be ~80 lbs in weight...

Any input is greatly appreciated...!

We race 48 lb planes with 7 inch spinners...26 inch diamerer props..230 mph...No problem...Check back tomorrow evening....The
aquila drones the engines came from weighed 300 lbs, launched with a cataputl.../the drones had no spinners...

I dont race anything as big as Antique for the cost and no air field for it, but I have found most engines turn about the same rpm. I think the reason is because the spinner is moving that air to the prop and loading it a bit more not sure.

Do you plan on running the 400cc moki in it? that would sound great and it swings a 40" prop

an even better sounding engine is the 20cc 3 cylinder by Kolm engines not sure on prop size though.

The herby 280 redone by Starr turn a 32x10 at 8,500 but with extreme noise.

Airraptor,

The Moki 400 would be the ideal engine for this plane, but sadly I haven't won the lottery recently...

I have a 3W 200 B2TS that I picked up for a good price, but I'd like more power... I have considered the 280 Deluxe from Starr Aircraft, looks like a fantastic engine, but it may not fit width-wise.

In theory the 200 should be plenty of power. We'll see I guess

Danny

Antique,

What engines are you using???

Thanks
Danny

Herbrandson 289s, Aerrow 200s, and DA 150 and 170s.. We hve some new ZDZs, 189 and 180. About 4 lbs lighter and about 40 HP..
Anybody else have a problem with their computer ? Tried this twice on mine, two differrent browsers, no luck...Used my IPad, it worked...????
I set up a 289 in a halfsize 80 lb GeeBee, worked fine...
The drone it was used in weighed about 300 lbs, the prop was a 26 or 28 inch military wood one, square tips and very wide blades.. rubber covered to deflect rain from the wood in case of bad weather...

RC,

Not your computer, just the way RCU has been working lately. I hope they resolve their problems soon.

Yup, must have fixed it between the time I tried 3 times on the computer, then workd fine with the I pad, then the computer worked again...I have noticed some random problems with the site for a few weeks now....It's working OK now..

I bet if you put a 26" spinner on a 26 inch prop it would remove nearly all of the prop load.