Increasing scale size ?

[G.Aums]

I would like to make a copy of an existing airplane,but about 50% larger. Any advice on how to do this?
thanks

Perhaps I should ask if proporsions should remain the same or change to keep flying characistics simular?

[vintage1]

keep everything the same, and scale up wood and other material dimensions +50%.

Or replace liteply with ply etc.

[BMatthews]

The outlines will scale up directly and it'll fly much the same. Where you'll need to make changes is in the structure where a lot of things do not scale up well. Fuselage formers and wing ribs are now further apart than they should be and you'll need to respace the ribs and formers and produce the plans needed to design those formers. Wood sizes will often be what the new sizes are but just as often you'll be better off changing them. Some may be able to go smaller or thinner and others should be taken up to the next size. This is where having a good sense of judgement brought on by building other projects comes in handy.

If you do a 1.5 time enlargement the wing area goes up by the square of that for a factor of 2.25 times. So the weight can technically double and your wing loading will still be lighter than the original by a little bit. But try to not go up much more than that if you can help it.

[JetPlaneFlyer]

I think you would be doing very well indeed to build a 150% model to twice the weight of the original.
If you look simplistically at any individual component it will get 1.5x longer, 1.5x wider, and 1.5x thicker, this is 1.5^3 = 3.375. So if you did as suggested and simply scaled up everything in the structure by 1.5 in all directions, using the same materials, your new structure would be 3.375 times the weight of the original, this is a simple mathematical fact. If you add more ribs and formers the potential increase is even more. In real life things are not quite so simple because you can optimise the structure a little more on the larger model, wood thicknesses probably won’t go up by a factor of 1.5 in all cases, plus things like covering, R/C gear, engines etc don’t necessarily scale up by the same factor. Even so the weight is still going to be well over twice the original unless you make big changes to the structure to lighten it.
The fact that weight increases faster than wing area as your model gets bigger is easy to see in the real world... this is why large models generally have a higher stall speed than small ones and full size aircraft have a higher stall speed than large models.

Steve