What is the best technique to apply the fibreglass to the dihedral and poly breaks so the finish is smooth, strong and light weight?

I'm ready to begin construction on my Spectre HLG, and I'm not 100% sure on the best techniques for joining the wing panels.

From : Joe Hahn

Hi Dave.

I use a method that has worked extremely well for me through the years. Three major considerations are:

Surface prep--- 1. The surface your applying the glass/carbon to is clean, and slightly "scuffed" with fine abrasive just enough to remove the glossy appearance. The thin skin in some area requires that you use great care to not sand too far and go through the skin.

Direct, smooth contact between the surface and material you're applying--- 2. Air bubbles or any separation between the surface you're glassing and the glass(carbon) can result in a failure of the joint. For that reason, I cut the carbon/glass to the final size, then apply a VERY LIGHT spray of #M 77 contact cement. Use just one light "dusting" coat over the "backside" of the material, allow it to dry slightly, and then apply. This technique ensures that the material will be down tight against the surface, and the resulting smoothness you get with this technique is unmatched.

Properly "wet-out" the material-- 3. Apply a heavy coat of thin (low viscosity) laminating resin with a brush to the material, ensuring that it is totally saturated. With fiberglass, the "white" color will pretty much disappear, leaving a nearly transparent look. With carbon, this gets tricky because there is no color change--it just stays black. It is VERY important to be sure to get PLENTY of resin on carbon during application to ensure that it is saturated. If you can see resin "standing" over most of the surface, you have applied enough resin. Let it soak for a few minutes, then, using a folded paper towel, place the towel directly on the area, allowing the paper towel to absorb the excess resin. Use a very slight pressure against the towel (with a GLOVED hand!!!). You'll see quite a bit of resin in the towel in a short time. Turn the towel over, or get a new one, and repeat. I typically repeat this about 3 times. This leaves a very nice amount of resin behind in the material while absorbing the excess into the towel. Lightly wipe around the edges of the area to remove the excess resin, and let it cure. I typically don't bother sanding the area because this leaves a very nice appearance but also it is possible to sand through the thin skins adjacent to the area, which would NOT be good!

Dave, if you have any other questions, let us know.

Joe Hahn
DJ Aerotech