I am thinking about some aircraft designs, and what concerns me is how one can determine if a wing (as designed and built per plan) can handle a 4G load.

What I really want is 3.5G, but 4G will give a margin of error.

Suppose that one decides to take a design and modify it to be a twin. In this case the weight of the plane will increase by about 700lbs (after removing the engine from the front, building engine nacelles, extra battery, etc.).

So if the original aircraft was based on a 2,500 MTOW (Max T/O Weight), and now it will weigh about 3,200, how can one determine if the wings can handle 12,800 lbs (w/o destructive testing)?

I realize that the landing gear and associated mounts will have to be beefed up. I'm just trying to figure out a few things not being a BSME (Bach. Sci. Mech. Engineer).

Thanx in advance
Wylber -- a Wrong Brother