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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Gas Engines >> Finding the right prop
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Finding the right prop - 8/31/2011 5:33 PM   
paulflys4fun


 

Posts: 141
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Joined: 12/22/2006
Last Login: 3/7/2013
From: Flintshire, UNITED KINGDOM
Status: offline 		Hi, has anyone any advice or help?


I have a 3w 120cc on cans. Its an old motor, but runs like a watch. I believe the best power range on this motor is between 5,800 and 6,100 rpm. I am running at 6,000 on a 30 x 10 prop. The plane the engine is pulling around is a big old 42% iad Cap 232. Its weight is 19.5kg. The engine will just pull the model vertical, but only just. I cannot afford to lose any power at all. My problem then:-

I was flying the plane at my local field, and one member of the committee was unhappy with the noise from the prop. The plane unloads on straight and level flight and the prop rips! I like the noise very pleasing and scale like but the committee does not agree. If i now over prop the model ie putting a bigger prop or more pitch on the model i believe i will drop out of the power band of the motor. As i said earlier i cannot afford to lose power. As big props are so expensive to buy just to try and find the right match what advice would you give to solve this problem.

Paul




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RE: Finding the right prop - 8/31/2011 6:51 PM   
av8tor1977



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From: Lukeville, AZ, USA
Status: offline 		A three blade prop will usually run a little quieter, but they are not as efficient as a two blade so you will probably lose some thrust. Some brands of props run quieter than others, but 30" props are pretty expensive to experiment with.....

I am so fortunate to live here in Mexico. I LIKE noise and here I can make all the noise I want. I even test run engines frequently right at my home with no complaints.

AV8TOR

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If it is not SCARY, it is NO WHERE NEAR powerful enough!!

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RE: Finding the right prop - 8/31/2011 6:56 PM   
Tired Old Man


 

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From: Valley Springs, CA, USA
Status: offline 		It's still a 42.99 pound plane being flown with a 120. It's not a problem of finding a porp that won't cost any power. It doesn't have the power it needs now so the true solution is a larger engine that does not have to be wound up tight all the time to fly it.

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RE: Finding the right prop - 8/31/2011 7:44 PM   
paulflys4fun


 

Posts: 141
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From: Flintshire, UNITED KINGDOM
Status: offline 		Hi, i agree the engine is working hard, but it will pull the cap up vertical just about. It flys very scale like to be fair. An old bigger engine will be heavier and will take the hole package over the 20 kg limit here in the UK, and a new lite weight engine is well out my price range, even a da copy!!!

I had thought of three blade prop, but you are very right i will lose power with one, so not practical either. I would like to try a few, but the cheapest 27 x 10 three blade is £89 so a big gamble.

Starting to think i either fly when noones at the field, or strip the engine and gear out and scrap the airframe.



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RE: Finding the right prop - 8/31/2011 8:58 PM   
DadsToysBG



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From: Bowling Green, KY, USA
Status: offline 		If I remember right the 3-w 120 weighted the same as a 150 at 8.5lbs. So moving up will not increase the weight of the plane. the 150 will fly the plane at a lot less throttle with a bigger prop 32x10 therefore less noise. Dennis

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RE: Finding the right prop - 8/31/2011 9:04 PM   
paulflys4fun


 

Posts: 141
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From: Flintshire, UNITED KINGDOM
Status: offline 		As i have posted before getting a da 150 is not an option money wise at the moment. I posted here as i hoped i had mist something. It would seem not.

I will strip the gear out tomorrow and wait for a second hand airframe to come along.

It was worth a quick post all the same.

Thanks Guys

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RE: Finding the right prop - 8/31/2011 9:32 PM   
Tired Old Man


 

Posts: 18600
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From: Valley Springs, CA, USA
Status: offline 		Making the plane lighter will provide the greatest benefit.

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Never lie, and never minimize or gloss. Tell it like it is and let the pieces fall where they may. The truth always wins.

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RE: Finding the right prop - 8/31/2011 9:58 PM   
DadsToysBG



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From: Bowling Green, KY, USA
Status: offline 		What I was thinking was getting a used engine and offsetting the price by selling the 120. Dennis

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