Glad to be of help. The first foam core wing one builds is always a thrill. Provided your building surface is flat, which I'm sure it is, you will be impressed with how straight and solid the wing turns out.

Further to Richards comments, a ply brace between halves is not needed, especially if the wing has a full airfoil joint at the root. When a brace or two is worth considering or is needed is when the wing center is sanded into a tunnel for use with tuned pipes in certain models with pipes slung under the wing on the fuse centerline (e.g., Prettner's Calypso). In this case, because the wing has half of it removed for 70% of the chord, there are two braces, one in front and one behind the tunnel. The tunnel is clearly also glassed as is the wing center joint overall but the braces insure that the wing is held together at a good 12" span or more. Otherwise, glass cloth and resin (whatever kind) takes care of the center joint.

There are different ways of going about the center joint glass work. My preference is to "glass up" in decremental layers of lighter cloth and wider spans. In other words, I start with 5-6 oz cloth about 2" wide. Then, when that is cured, I sand it smooth making sure not to cut into the cloth itself and lay up a wider band about 4" wide of 2 oz cloth. Sand again and finish off with a 6-8" wide band of 3/4 oz cloth. This last cloth fairs into the wing nicely allowing one to use plastic covering if desired without unsightly weave or otherwise provides a good surface to fill for paint. Of course, if the entire wing is to be painted, the final layer can cover the entire wing as it is "glassed".

As far as the glue used to do this, that is exactly what finishing (laminating) resin is for. It is thin so it will flow into the weave of the cloth and form a hard joint between the wood and the cloth. What you might know as "fiberglass resin" (from places such as Home Depot) is probably polyester resin which needs to be catalyzed. It is easier to sand than epoxy but it also smells awful - familiar with boat yards? That's the smell. I don't use it because it gives me headaches. If you are sensitive to solvents, stick with epoxy. Epoxy is of course also a catalyzed resin which is more commonly mixed 50/50 rather than 10/90 or similar like some epoxies or polyesters.

If you are planning to use water based paint, you might also like to try using water based varnishes to bed in the cloth (e.g., Minwax Polycrylic) although it can also be used if finishing with other types of paint. Granted, I'd use this for the 3/4 oz cloth for the entire wing but not for the real center joint glass (I'd stick to epoxy there). Polycrylic is not as hard as epoxy and requires more layers but it is lighter. I'd stay way from using regular "tough joint" 15 or 30 min epoxy with glass cloth. It is too quick to set and it is too viscous and will build up too much. The only way I'd consider using it is if I didn't have finishing resin and then I'd cut it down 50/50 with denatured (90% or higher) alcohol so that it flows. The epoxy is mixed first and then the alcohol is added until you have a semi liquid consistency. Finishing resin is much better and when it has begun to set, it can also be brushed with alcohol to reduce the amount of sanding required.

Regarding making cuts in foam core wings, with small openings like those needed for servo wells or HW landing gear blocks, I prefer to use a sharp blade in an X-Acto knife. A #11 is not long enough or of the right shape but a straight blade which is 1.5 to 2" long produces very sharp and clean cuts into the foam. Where the soldering gun/foam cutter is needed and comes into play is when one needs to cut horizontally in the plane of the wing. With servo wells it's not really needed. With LG blocks it is needed but it is also easy to remove the foam with pliers leaving a rough base and then sanding that base smooth with paper wrapped around the block itself.

I usually line the servo wells with balsa so that the HW servo rails have a tight and strong joint to hold the servo in place. Gluing in HW servo rails into foam is not great in my experience even if the cut is clean. Of course, with the LG blocks it's different as the joint between the block and the foam is sheeted and often glassed over top. Unless your wing is very thick, you can often open up the well to the top sheeting leaving a foam free cavity for your balsa lining work. When it comes to the tunnels in the wing for servo leads, soldering guns with loop tools are nice but one can also sand a groove into the top of the wing and then cap it with balsa before sheeting.

'nough said!

David.