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Old Nov 01, 2012, 10:14 AM
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What happens if you put a .90 2-stroke in a 60 size plane?

I've always wondered when looking at the .60 2-stroke or .91 4-stroke engine requirements on various planes if you could just say "whatever!" and put a .91 2-stroke in it and grunt like Tim Allen. Does anyone do that?
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Old Nov 01, 2012, 10:30 AM
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Ontario, Canada
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Quote:
Originally Posted by Darkenor View Post
I've always wondered when looking at the .60 2-stroke or .91 4-stroke engine requirements on various planes if you could just say "whatever!" and put a .91 2-stroke in it and grunt like Tim Allen. Does anyone do that?
More Power!!
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Old Nov 01, 2012, 11:15 AM
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Everyone does it. Sometimes I have seen pilots waiting for the tank to run dry because the idle isn't low enough, and more than one wing fold up because of the extra speed/weight.
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Old Nov 01, 2012, 11:19 AM
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My son ended up swapping out the .40 engine in his Rite Flyer 40 trainer for a 1.08 but had to set it back about 3" to keep the balance correct. It flew beautifully . I might add that airspeed didn't change because he used a prop pitch (6") that didn't allow high airspeed so there was no problem with overstressing the airframe.
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Old Nov 01, 2012, 11:21 AM
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Originally Posted by aspeed View Post
Everyone does it. Sometimes I have seen pilots waiting for the tank to run dry because the idle isn't low enough, and more than one wing fold up because of the extra speed/weight.
Neat!

That shouldn't make me laugh, or smile, but it kind of does. Thanks for the info.
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Old Nov 01, 2012, 11:44 AM
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Besides the higher idle airspeed, a nose heavy aircraft is harder to flair on landing.
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Old Nov 01, 2012, 11:56 AM
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Well you get more power that is for sure.
But you may have to make changes to get the CG to come out OK.
Also propeller clearance can be a issue if the engine needs to turn a large diameter prop, as some planes don't have enough ground clearance.
Some planes could be affected by the additional power and larger prop causing more torque roll to the left too.
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Old Nov 01, 2012, 12:01 PM
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I always try to select an engine that is heavy enough to balance the CG W/O adding ballst in the nose.

That usually means MORE POWER!
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Old Nov 01, 2012, 12:44 PM
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I can say this! "the 61fx is within a couple oz's of the 91fx" they are physicaly the same size!
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Old Nov 01, 2012, 02:07 PM
I HATE GLOW PLUGS!
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Originally Posted by whiskykid View Post
I can say this! "the 61fx is within a couple oz's of the 91fx" they are physicaly the same size!
Then a 180 Saito 4-stoke seems in order!
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Old Nov 01, 2012, 03:36 PM
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I should mention that there are practical limits to how large of a engine one can use. The wing loading can go up considerably turning a plane into something more like trying to fly a brick or the Space Shuttle. Having to take off and land with air speeds over 100 mph for a RC model airplane might be more than a flyer might want to do.

But for modern .60 (10cc) engine size planes, usually one can go up to a 1.20 or 20cc engine OK as people have been putting up to 1.20 size four stroke engines in their planes for a long time without much hassle. Thus a .91 size or 15cc size engine is not a problem. But if the .60 size plane is a old design from many years ago before Schnuerle engines became popular, it can be a problem as the early .60 size planes weren't all that big but more like .45 size planes are today.
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Old Nov 01, 2012, 04:13 PM
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I sent you a PM.
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Old Nov 01, 2012, 04:47 PM
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Quote:
Originally Posted by Darkenor View Post
I've always wondered when looking at the .60 2-stroke or .91 4-stroke engine requirements on various planes if you could just say "whatever!" and put a .91 2-stroke in it and grunt like Tim Allen. Does anyone do that?
YES!!!
OS 91FX in the space reserved for a 65AX = Superb fun
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Old Nov 01, 2012, 08:39 PM
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No probs . Infact this should be regarded as normal practice . Cheers the pope
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Old Nov 01, 2012, 10:07 PM
I HATE GLOW PLUGS!
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United States, NY, St Lawrence
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Quote:
Originally Posted by earlwb View Post
I should mention that there are practical limits to how large of a engine one can use. The wing loading can go up considerably turning a plane into something more like trying to fly a brick or the Space Shuttle. Having to take off and land with air speeds over 100 mph for a RC model airplane might be more than a flyer might want to do.

My take is that if ballast is eliminated by a larger engine, the net weight of the aircraft is still the same as W/the smaller engine Wballast.

As long as the structural factor of the airframe is not exceeded there is no negative affect.
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