Look in a woodworking place.  There is a device with a bunch of rods that you push against an object.  I can't remember the name, but it will duplicate curves.  Should be able to find it in many hardware stores.  Someone will tell us what it is called, I'm sure. I just looked and there is also a thing called a "flexible curve" that might work for you. 

Or, a scissor and a lot of cardboard...start cutting and fitting, marking the "high" spots and cutting some more, until you have it exact (and cardboard scraps up to your knees but cardboard's cheap...)  Just do one surface and mirror it for the other.

I'm a low-tech kinda guy...

Wrap a piece of saulder around the wing, and then trace the INSIDE of that wrap.  Never tried it, but Windy suggested it to Bill Hummel one night.

I have in my stuff a thing I used to use for drafting odd curves.  It's a plastic rectangular strip that has something inside that allows it to flex to different shapes.  Works sort of like the piece of solder idea.  I did find that it really wouldn't hold shape when moved, something that I think the solder would tend to do.

Like noted, you pays your money and you takes your choice!  Use whatever gets the desired result.

Very handy gadget, yes...we used it to replicate ogee chair molding in old house renovations.  Problem with it is, it's only 6" long--won't reach all the way across most wings. maybe someone makes a 12" one,which would be much more useful.