Dealing with Balsa
Balsa coring needs careful attention. Why? “That stuff soaks up water like a sponge,” Mark Vahle says. If you want to keep any future water intrusion at bay, it’s essential to first “bed the core” by removing as much wood as possible and replacing it with a paste of epoxy resin thickened with a suitable filler, like colloidal silica. Start by removing the balsa from the hole’s perimeter. Use a Dremel or ice pick, working between the fiberglass skins to a depth of at least a half-inch. Work down to the fiberglass to ensure the best bond. Mix the resin and hardener, and then add the silica, thickening it to a paste. Next, use a tongue depressor to work the goop into the void, moving in one continuous direction to eliminate trapped air bubbles. A single session should do it. For depths deeper than a half-inch, allow one layer to cure to avoid building up excessive heat that cracks the resin. Once cured, sand the edges and add the next layer.Last, sand the edge back to the shape of the original hole.
If you’re drilling a hole for routing electrical wires or control cables, it’s essential to cover the edges for chafe protection. “For a customer, it could be as easy as taking electrical tape and wrapping it around wiring where it passes through a hole,” Vahle says. Wire looms offer more permanent protection. Regal will also fill some smaller holes with silicone; when it hardens, it eliminates any movement within the hole. Larger holes can be trimmed with PVC conduit, which can also be secured with silicone. Beware of bare fiberglass edges; they can be extremely sharp and cut through insulation with movement and time.