Does a large diameter spinner affect prop selection???
 

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...!

RE: Does a large diameter spinner affect prop selection???
 

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...

RE: Does a large diameter spinner affect prop selection???
 

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.

RE: Does a large diameter spinner affect prop selection???
 

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

RE: Does a large diameter spinner affect prop selection???
 

Antique,

What engines are you using???

Thanks
Danny

RE: Does a large diameter spinner affect prop selection???
 

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...

RE: Does a large diameter spinner affect prop selection???
 

RC,

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

RE: Does a large diameter spinner affect prop selection???
 

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..:)

RE: Does a large diameter spinner affect prop selection???
 

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