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Old Dec 22, 2012, 05:04 PM
Transplant in 1996
United States, NE, Scribner
Joined Aug 2011
195 Posts
Help!
wingspan vs engine size.

I was wondering : do we have any posts (on RC Groups) that describe what engines can handle what size wingspans? I have way too many .60+ size engines
and somewhat understand those are for 5 an 6ft WS's. Am going to start selling if thats the sizes I have for.
PLEASE someone show me the way!!!!
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Old Dec 22, 2012, 05:57 PM
team sleprock
whiskykid's Avatar
United States, WA, Port Angeles
Joined Dec 2009
3,406 Posts
there is no cut and dry scale for engine size!

but if you pay attention to most adds, the max size engine, seems to be running about 1cc an inch! I.E. a 55" ws. plane is recomending a 46 to 55 size engine! a 60" ws recomends a about the same!

ok heres where it gets wierd, so what kind of 60 size engines do you have? and how old are they?

I am jusy getting back into RC myself, and it is becoming apperant, that say the os55ax now puts out as much power as my 61fx! which was top o the line not too long ago!

if you are talking about modern 3d airplanes? then over powering an airframe, is a comon practice! so stuffing an older sixty in a 46 ta 55 airframe, should be just fine! a lil heavier, but if you have it use it!

this is just what I have learned from hours of reading! so take it for what its worth!
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Old Dec 22, 2012, 07:23 PM
Transplant in 1996
United States, NE, Scribner
Joined Aug 2011
195 Posts
A definate THANK YOU Kid!
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Old Dec 22, 2012, 08:43 PM
Tampa,Fl
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United States, FL, Tampa
Joined Jan 2007
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On a 60 size trainer would have a wing span around 74" Now I had a Profile Plane with a 60 in it but its a 3D fully aerobatic airplane that had a 48" span. All depens on weight really. The longer the wing span, the smaller the motor can be to get the Plane in the air.
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Old Dec 23, 2012, 05:57 AM
Registered User
United States, TX, Leander
Joined Sep 2003
2,660 Posts
This way grass hopper!
Seriously, its mostly judgement. I agree with the other responses. But wingspan is part of it, you have to consider wing area and weight. And on top of that, the kit specs are generally not very accurate so it comes back to judgement based on wingspan, area, and perceived weight. I usually use a 1.20 4-stroke on a 1/4 scale cub (about 108" ws). I know personally some guys that run that same plane with a .91 4-stroke and fly on the wing with no problems. My Rascal 110 (110" ws) would easily fly with a .91 4-stroke, but only on the wing.
Edwin
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Old Dec 23, 2012, 10:23 AM
team sleprock
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United States, WA, Port Angeles
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or like my 78" extra 260 that has a 50cc gasser in it!
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Old Dec 26, 2012, 03:14 PM
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Kotzebue, Alaska
Joined May 2006
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I check with factory made planes using same size engines.
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Old Jan 02, 2013, 12:57 PM
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Orlando FL
Joined Apr 2009
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Quote:
Originally Posted by edwin1 View Post
This way grass hopper!
Seriously, its mostly judgement. I agree with the other responses. But wingspan is part of it, you have to consider wing area and weight. And on top of that, the kit specs are generally not very accurate so it comes back to judgement based on wingspan, area, and perceived weight. I usually use a 1.20 4-stroke on a 1/4 scale cub (about 108" ws). I know personally some guys that run that same plane with a .91 4-stroke and fly on the wing with no problems. My Rascal 110 (110" ws) would easily fly with a .91 4-stroke, but only on the wing.
Edwin
I think that's the way to think about it. Wing loading and flight style.

Knowing the weight, and the wing airfoil and loading expectations, you get how much thrust you will need to get the plane on the air. With flight style (slow, scale, 3d) you get the weight to thrust ratio. If 3D, you will need a bit more than 1:1. If scale, 75:1/60:1, or even 50:1 might work fine, depending on the airfoil (flat bottom has more lift, being more efficient to fly on the wing)

That's why a Trainer or a Piper CU, can fly with much smaller engines without a problem. You fly on the wing all the time, and have very efficient (but with very little flexibility) airfoil. A Sport plane with a symmetric wing will need much more power to keep it flying, but will be very flexible in the air. And a 3D plane, well, you do more than a 1:1 to be able to prop hang AND vertical out-of it, so you are basically flying on the prop with airfoils for control (LOL).
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Old Jan 09, 2013, 05:09 PM
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Georgia
Joined Jun 2007
663 Posts
If I had a choice between two engines with adequate power, I'd usually select the one that requires the least ballast to get the CG right!
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