I'm in the process of making a foam wing, with a carbon tube down the centre, skinned in CF.  It's a dual-plane wing so there is effectively two aerofoils stacked on top of one another.  The plan is to use 2 or 3 separators which will stop the slot between the wings coming together and affecting the downforce.  The concern is that there is likely to be 100kg of downward pressure on the wing.

Normally for we make the pattern a perfect fit between the elements and then cut the pattern in half

lay 3 plies 200g carbon onto 3 faces of both patterns

the face touching the top skin of the lower element and the face that forms the centre spar and the face touching the bottom skin of the top element

bring together and cook and you will have a slot gap separator 1.5mm thick on its centre an .75mm thick in the area supporting the skins

hope this makes some sense ? I'm back in the UK on Fri an will try to post some pictures,should make it a lot clearer

i think a picture will tell a 1000 words in this case

but to know if 2mm skin is thick enough ? how long is a piece of string ?

whats the chord length and the thickness of the profile ?

you need to install a shear web which will take all the forces and spread the load down the wing onto the mounts

but 2mm skin is complete overkill imo on a foam core wing with a shearweb  ... you shouldnt need more than .7 - 1 mm