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-   -   Plane weight to engine size (https://www.rcuniverse.com/forum/questions-answers-154/631201-plane-weight-engine-size.html)

jdwiflyrc 03-18-2003 12:10 AM

Plane weight to engine size

Is there a rule of thumb formula to figure engine size to plane weight and does this work for all gas, four stroke and 2 stroke engines.

All help will be appreciated.

Thanks, John

Geistware 03-18-2003 02:52 AM

Plane weight to engine size
You need to first determing what weight you need to balance your plane (range) then you need to select an engine that can produce as much thrust as your plane weights.

Remember, for low wing loadings (gliders and sport aircraft) you can go with less thrust and for performance (aerobatics and pylon racers) you may want to go with a little more thrust

jdwiflyrc 03-19-2003 02:31 AM

Engine to plane weight
Hello and thanks for that answer.

Now how do you determine engine thrust.

Thanks, John

CafeenMan 03-19-2003 05:53 AM

Plane weight to engine size
There are rules of thumbs for types of aircraft - not for aircraft overall.

For example a good .40 trainer has about 700 inches of wing. That's way too much wing for a .40 sport plane.

So to answer your question, no there isn't a generic rule of thumb. You have to include the kind of plane you're talking about as part of the question. :)

MAJSteve 03-19-2003 06:13 AM

Plane weight to engine size
I usually use .1 cubic inch for every pound of finished weight. Therefore a 4 lb plane would have a .40, a 6 lb a .60, and an 18 lb plane a 1.8. If its a weak engine or propped wrong, it might be marginal.

Depending on the engine, this may be adequate to good performance, it will not give unlimited vertical. A rule of thumb for this is that the engine should produce AT LEAST as much thrust as the plane weighs full of fuel. There's no lift so the prop has to carry the whole weight PLUS the extra needed for climb or hover.

Whirley Bird 03-21-2003 05:24 AM

Re: Engine to plane weight

Originally posted by jdwiflyrc
Hello and thanks for that answer.

Now how do you determine engine thrust.

Thanks, John

I'm beat and it's late.
Look for a PM tomorrow and i'll let you know how we measured thrust on both full size gyros,hang gliders and RC aircraft
Do you have a plane and engine now?

jdwiflyrc 03-21-2003 10:39 AM


more of each than I need. I acquired a large shoestring recently and trying to come up with an engine for it.

Thanks, John

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