Hey Guys,

I know there are some general rules about engine sizes as far as the size of plane. But lets take for example you added a lot of weight to a rebuild (40 size crashed plane) . Is there a rule of thumb as far the amount of weight added to the increase of engine. I realize this depends on the plane design, but I do not want to rebuild a plane and it turns out to be a brick?

General theory's will be appreciated.

I'm a higher altitude flier and you will see many of the planes flying with the largest recommended engine and bigger. You will even see 60's on 40 size planes around here. In my case 90's on 40 size planes and 40's on 25 sized planes.

I would think that a crashed and repaired trainer would fly with the highest recommended engine. If not you are starting to get a bit heavy and the plane will be a little harder to handle. If you do put on a bigger engine you will want to make sure the balance of the plane will also be correct. This might involve moving the flight equipment rearward, or adding ballast to the tail.

I was going to say how I pick my engines, but I'm sure what I would say would get me in trouble.

I had a big answer too but in the end I decided to keep it. It basically said that if it's that heavy then perhaps it's time to retire it. Sure you'll get it airborne with enough power but it wouldn't be any fun to fly if it actually needs that much extra.

I know that's not what you wanted to hear but that's what I think.

I fly elec and even in elec bigger motor is better so they say
everyone trys to move a brick at 500mph. CU

Yes

Some of the funnest to fly are.

What happens when the engine quits?

Now you have an overweight airframe with a humongous engine on the nose. Chances of making the field in a deadstick are slim

Granted the glide path will not change with weight, but the airplane will have to fly a lot faster to maintain a specific angle of attack. Otherwise, at a constant speed, the angle of attack will be higher and closer to stall. I suppose the answer to the question really depends on flying style, but I have found that every ounce of additional weight on my airplanes detracts from the flying qualities.

The .60 on a .40-size plane may be just the thing to save it one day when you over-rotate on takeoff, or have to do a quick waveoff on final...My SST .40 has a K&B .61 on it. Thats why we have a throttle.

There are two aspects to this. Firstly, too much power, like too much airspace below you, is virtually impossible to achieve. As has been said - that's why we have throttles.
Second point is weight. A model which is overweight is bad news - and a much repaired model may well fall into that category. The problem, most aspects of which have already been mentioned - is the wing loading. A typical 40 size trainer with a wing loading of around 16-18 ounces per square foot (provided the basic design and the trim are sound, of course) is a *****cat to fly. A model that size with a loading of, say, 30 ounces per square foot is quite a handful.
The bigger the model is, the higher the wing loading can be and still give comfortable flying characteristics.

Mike

What a strange outlook you Americans have. a "pus sy cat" in this context , is something which is simple straightforward, non-taxing. Why not leave English to those who invented it?

Mike

If it's over powered and overweight, it's not a trainer anymore, is it?

Regarding the term "*****cat"...maybe I've been misunderstanding the meaning of the term all along, lol!

I thot the French invented English--

We have an overactive obscenity filter that sometimes butts in where it's not needed. But the *'s add color, don't you think

The glue and used in building a we bit stronger probly last
8-10 hard crashes. But I have achived getting my elec doun in weight new outrunner brushless and lipoly batterys always trying
not as much as free flight like you say. CU

I thot the French invented English<<

Nope

The French invented running out on their friends

Mike

I believe the French invented the words for "surrender" and "Weasle", lol

Sorry, couldn't resist!

The french lost with little effort in 1955
in Ni VooFu vietnam real bad turned yellow i knew people were there after
them. There whole history is cowards.
I am X retired mil. CU

Back to the original question, to properly answer it you need to say what the airplane is, what it weighed before and after the repairs, etc.

See if the weights fit the range of the original kit manufacturers estimates/suggestions. Are there other airplanes flying with the same wing loading.

What is heavy to you might be normal weight to me and probably is, I like epoxy and plywood.

But mainly to get a good answer to a question you need to put in a lot of information. Otherwise you get a lot of good information but the answers are just as generic as the question.

But at least it didn't take them 2 years to decide.

How about building the plane, then put all the stuff in where you'd like it to be, and last...select a motor that makes the whole thing balance nicely. Awwww,... maybe not.
As for inventing english...US and UK are two countries separated by a common language. 8<)
Hey Mike....explain "Bobs your uncle" to us over here. 8<)

I fly elec and build scratch lately
have to chane the rules again much liter batterys. I had one bird that had a glass
rod about 18 out front of the fus where wt and bal was But even on gas birds
with no lead. I have pulled weight and balance on C118 size airplans and only used about 200 lbs total lead. CU

Robert's brother is your father --
and Fannie is his sister
That is all there is to it .

But at least it didn't take them 2 years to decide

Don't be unkind to our American cousins

Mike

Captain Jim

'Bob's your uncle' means that something has been completed fairly, ot even very, easily.

Now one for you - what does 'The whole nine yards' mean? Or to be more precise - why nine? Why not ten? Or eight?

Mike