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Does a large diameter spinner affect prop selection??? - 2/6/2012 5:41 AM   
cmreefer


 

Posts: 81
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From: costa mesa, CA, USA
Status: offline 		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...!

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RE: Does a large diameter spinner affect prop selection??? - 2/6/2012 6:05 AM   
Antique



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Status: offline 		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...

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RE: Does a large diameter spinner affect prop selection??? - 2/6/2012 6:44 PM   
airraptor


 

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From: fairfield, CA, USA
Status: offline 		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.

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RE: Does a large diameter spinner affect prop selection??? - 2/7/2012 3:29 AM   
cmreefer


 

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From: costa mesa, CA, USA
Status: offline 		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

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RE: Does a large diameter spinner affect prop selection??? - 2/7/2012 3:31 AM   
cmreefer


 

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Status: offline 		Antique,

What engines are you using???

Thanks
Danny

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RE: Does a large diameter spinner affect prop selection??? - 2/7/2012 6:57 AM   
Antique



Posts: 9825
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From: Somewhere, DC, USA
Status: offline 		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...

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RE: Does a large diameter spinner affect prop selection??? - 2/7/2012 3:08 PM   
Truckracer


 

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

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RE: Does a large diameter spinner affect prop selection??? - 2/7/2012 3:25 PM   
Antique



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Status: offline 		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..

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RE: Does a large diameter spinner affect prop selection??? - 2/7/2012 5:56 PM   
Killer_Matt



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

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