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Is A 15 enough - 8/15/2006 3:38:34 PM   
suzonka


 

Posts: 652
Joined: 11/22/2004
From: calverton Long Island, NY, USA
Status: offline 		I have a built up warbird ,it was electric and I converted it to a 15 engine,any way I know a lot of combat pilots use a 15 engine for there planes, so maybe someone can help me.with an OS blue LA 15 engine just broke in, I tried a 8x4 nylon grish prop,the plane flys but rather sluggish on take offs and snaps in the air, so I just put a 7x6 Zinger wood prop will this work better, because I dont believe the nylon grish 8x4 was letting the engine reach its 18,000rpm power band,what do you think? I remember when I flew .049 Cox engines with 6x3 props you could see the r4edish white gow of the glow plug through the exhaust holes at full rpm and they could pull those little airplanes .

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RE: Is A 15 enough - 8/15/2006 8:01:22 PM   
pe reivers



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From: Arcen, , NETHERLANDS
Status: online 		for combat and plane of over 900 grams, the 8x4 is the prop to use, because you need the extra pull. rpm will be between 15000 and 16000. I hardly believe a plain bearing engine delivers best around 18000. None of us rev that high, unless using ball bearing engines like the MVVS. The OS plain bearing .15 is rather aenemic above 900 grams. MVVS .15 fly very well up to 1050 grams. (my mvvs .15 uses an 8x3 prop, plane 1100 grams)
What are your plane's data?
Span, weight?
Typical combat engines for 1/12 scale rules:
smal warbirds like mustang, Spit etc having original span less than 12 meters: .15 engines weight >700 grams
larger birds span =>12 meters .21 engines, weight >1000 grams
if they also have a wing of =>25 square meters or more, .25 engines. weight >1000 grams

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RE: Is A 15 enough - 8/16/2006 7:41:09 PM   
Montague



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From: Laurel, MD,
Status: offline 		An 8x4 is a bit large for the engine, but not out of the question. Try an 8x3 master airscrew prop. We also used 7x4's for combat, so maybe a 7x4 or 7x5. I think 7x6 might also be a hair on the big side.

The Grish props, if I recall, are very fleixble, right? You might also try an 8x4 master airscrew or another brand if the Grish doesn't work well. Different brands of props in the same size can be radically different, espeically in this size range.

How much does the plane weigh, and what is the wing area?


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RE: Is A 15 enough - 8/16/2006 10:06:31 PM   
suzonka


 

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From: calverton Long Island, NY, USA
Status: offline 		the weight is approx 2.5 lbs the wing spand is 40 inches

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RE: Is A 15 enough - 8/16/2006 10:18:33 PM   
Montague



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From: Laurel, MD,
Status: offline 		2.5lbs on that amount of wing area is going to be a bit sluggish. SSC planes typically have more wing area and weigh about the same, giving a lighter wing loading.

You're going to need to experiment. I think the props I mentioned above might be good starting points, though it will take some testing.

If the engine wasn't the .15LA, but instead was a Magnum, OS CV-A, or Norvel, I'd say start with a 7x4 or 7x5 as those engines like to rev more than the LA does. The LA seems happier with larger props, so the 8x3 would be good to start with. All those props being Master Airscrews. Though I've been using the older MAS GF/2 line, I don't know if the GF/3 is going to be better or worse in that size. At least with the 8x3, the GF/2 is still easily available, since Master Airscrew keeps making them for us combat guys flying SSC. (The vast majority of Master Airscrew prop sales in that size are to combat pilots, and we buy a TON of props)


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RE: Is A 15 enough - 8/16/2006 10:21:58 PM   
rrh


 

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From: Colorado Springs, CO, USA
Status: offline 		You could help it out by offing that draggy LG and hand launching. Have you drilled out the baffle in the muffler? That will gain you a few rs.

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RE: Is A 15 enough - 8/17/2006 2:27:50 AM   
suzonka


 

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quote:

ORIGINAL: rrh

You could help it out by offing that draggy LG and hand launching. Have you drilled out the baffle in the muffler? That will gain you a few rs.

rand , Ive never drilled out a baffle, I took them completely out, how many holes do you drill and what size??Thanks

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RE: Is A 15 enough - 8/17/2006 2:30:45 AM   
suzonka


 

Posts: 652
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From: calverton Long Island, NY, USA
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quote:

ORIGINAL: Montague

2.5lbs on that amount of wing area is going to be a bit sluggish. SSC planes typically have more wing area and weigh about the same, giving a lighter wing loading.

You're going to need to experiment. I think the props I mentioned above might be good starting points, though it will take some testing.

If the engine wasn't the .15LA, but instead was a Magnum, OS CV-A, or Norvel, I'd say start with a 7x4 or 7x5 as those engines like to rev more than the LA does. The LA seems happier with larger props, so the 8x3 would be good to start with. All those props being Master Airscrews. Though I've been using the older MAS GF/2 line, I don't know if the GF/3 is going to be better or worse in that size. At least with the 8x3, the GF/2 is still easily available, since Master Airscrew keeps making them for us combat guys flying SSC. (The vast majority of Master Airscrew prop sales in that size are to combat pilots, and we buy a TON of props)
thanks, Ilhve to get an 8x3 MS

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RE: Is A 15 enough - 8/17/2006 5:51:49 AM   
Alex Treneff



Posts: 144
Joined: 2/25/2006
From: Jackson, TN, USA
Status: offline 		When we originally began trying 2.5# coroplast flying wings for SSC we were using Master Airscrew 7x6s on Magnum .15s.

That was a step up in power, but a lot more weight than our 32" 1.5# balsa flying wings we had been using with .10FPs. To compete nationally meant flying SSC, not open A.

The 7x6s will work on a .15, depending on what you want to do.

The Master Airscrew 8x3 should rev 17,500-18,000 on an OS .15LA



< Message edited by Alex Treneff -- 8/17/2006 5:54:32 AM >

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RE: Is A 15 enough - 8/17/2006 9:06:06 AM   
suzonka


 

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From: calverton Long Island, NY, USA
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quote:

ORIGINAL: Alex Treneff

When we originally began trying 2.5# coroplast flying wings for SSC we were using Master Airscrew 7x6s on Magnum .15s.

That was a step up in power, but a lot more weight than our 32" 1.5# balsa flying wings we had been using with .10FPs. To compete nationally meant flying SSC, not open A.

The 7x6s will work on a .15, depending on what you want to do.=================================================================
Hi Thanks, I just want my spitfre to fly with better takeoff an in air action,




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RE: Is A 15 enough - 8/17/2006 3:21:59 PM   
rrh


 

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quote:

Ive never drilled out a baffle, I took them completely out, how many holes do you drill and what size??


The LA baffle is not a separate piece you can take out, it is cast inside. A 1/2" bit takes most of it out and a stone on a Dremel will get it all.

r

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RE: Is A 15 enough - 8/17/2006 5:43:03 PM   
whiskey29


 

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Status: offline 		15 will be enough

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RE: Is A 15 enough - 8/17/2006 8:13:04 PM   
suzonka


 

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From: calverton Long Island, NY, USA
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quote:

ORIGINAL: rrh

quote:

Ive never drilled out a baffle, I took them completely out, how many holes do you drill and what size??


The LA baffle is not a separate piece you can take out, it is cast inside. A 1/2" bit takes most of it out and a stone on a Dremel will get it all.

r
, OK Im use to those 40 engines that the baffle pops out idf you want it out, but on the 15s will you loose on the muffler pressure feed line?

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RE: Is A 15 enough - 8/17/2006 8:16:37 PM   
suzonka


 

Posts: 652
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From: calverton Long Island, NY, USA
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quote:

ORIGINAL: whiskey29

15 will be enough


your right Whiskey29 the 15 is enough , I just tried a 7x6 zinger wood prop , no pull at all .did a cart wheel , so I changed to a red robbie wide blade 7x4 and what a puller it turned out to be.

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RE: Is A 15 enough - 8/17/2006 8:57:02 PM   
rrh


 

Posts: 327
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From: Colorado Springs, CO, USA
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quote:

but on the 15s will you loose on the muffler pressure feed line?


I knew this would be asked sooner or later, as it always is I have 2 LA .15s with the baffles hogged out, they have enough fuel run through them that they are a nice crusty brown color and all delivered from standard clunk/muffler pressure tanks. Has never been an issue with mine.

r

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