Guys, I am experimenting with a different procedure for skinning foam. This isn't for everyone of course, but this thread that Mike Hester started, has brought all the craftsmen out of the ARFie pile, so here goes:

Balsa-less skinning with a vacuum bag:
1- start with a well cut foam core and foam backing (the husk), (that preferably has the leading edge cut all the way at the correct radius) and complete all of the internal structure as you would for a balsa skinning.
2- Cut and face the ailerons with appropriate balsa at this early stage, but leave square
3- cut a set of 0.1mm mylar skins to fit the foam core exactly
4- wax the mylar inside surfaces 2 coats with a mold releasing wax, and polish with a soft cotton cloth.
5- use a good quality automotive paint such as PPG OMNI, and spray the desired pattern onto the mylar inside surfaces, and let it cure completely overnight
6- prepare 2 layers of 1.7oz Kevlar cloth, to fit the core exactly; also cut a layer of glass veil to exactly fit the wing. The leading edge and trailing edge are reinforced with a narrow strip of 5.7oz carbon cloth about 2 mm wide
7- lay the glass veil onto the painted mylar and wet it out with a slow curing epoxy. Must use extra care here to remove all bubbles. My favorite epoxy is Pro Set 125 /229.
8-Then alternately thetwo layers of kevlar, and the carbon LE and TE strips. Remove all of the excess epoxy with paper towels..
9-Paper towels will help with any trapped air.
10-Roll the sandwich with a sponge roller, to remove any bubbles. Having a flat smooth surface, like glass, to work on is a must.
11- carefully fit and lay the composite "skins" onto the foam cores. The epoxy will stick enough to make this fairly straight forward
12-insert in the vacuum bag
13- place paper towels all around the mylar, top and bottom, laying it flat, and covering every sq mm
14- seal the edges of the bag with plumbers putty or modeling clay
15- install the vacuum suction tube, and use about 3-4 in mercury vacuum. Don't really want much more than that, but see what your wing needs and adjust from there. The composite skin needs little to conform
16- place the assembly back in the husk
17- place a 1 kg weight on the foam to keep it flat and let it cure.
18- after 24 hours cure, separate the components, remove the mylar and voila! A panel that has a built in finish just like the so called "pros". The mylar is usually a mirror shine so that's what you will get.
19- after four days, the wing maybe post cured in a 125 degree oven (a insulated box with a 100 W light bulb in it connected through a thermostat)

One of these days I will take some photos and start a new thread. Technique is a little different but with practice, no reason this method couldn't produce lighter wings than present methods, and with much less work. The great thing about these skins, they will be completely dent resistant. Having seen how you folks are really interested in construction technique, and love building from scratch, you shouldn't have much problem with this.

In addition, there's no reason at all not to modify the technique a little and build wings with composite balsa skins that are totally finished, out of the mold. Not as dent resistant, but a step forward in lightness and finish

Regards,

MattK