I searched the archives but couldn’t find an answer to this. When installing a leash cup on my last board I got tons of bubbles. It looked almost like it was boiling, and it would not stop. When it set there were a few small bubbles, and one big/deep bubble that I had to fill. On my current board I purchased all new materials, and got the same result. I’m guessing there’s something wrong with my recipe. I’m mixing resin, surfacing agent, white pigment, cabosil and catalyst. How should I change this mix to eliminate the bubbles?
NEVER NEVER use Surfacing agent for aplications like leash cups, fin boxes, glass on fins etc. Always straight lam resin with whatever you choose to thicken it with. Cabolsil, microballons, chopped fiberglass, all are fine to thicken the resin as is pigment, but SA should not be added.
SA adds wax, and that is very bad fro installation apps.
Easy busy! First, check the mix texture: it has to be like honey. Second, don’t mix too much. Third, put a short strip of tape on the cup (check the alignment). Fourth, pour the resin mix into up to half the hole. Finally, insert the cup in the hole and press the tape against the deck (take care of the position). Let the excess of resin gets out. This will avoid the bubbles and you’ll have a clean cup finish after sanding.
Pay attention to the hole depth and the internal wall. Small caves can create bubbles, too.
Bubbles usually indicate two things: the catalyst ratio is off, resulting in a mix that’s WAY too hot, or you’re mixing the resin too much and entraining air that can’t rise out of the mix cuz it’s too viscous. One other possiblility: if your hole is dug out with a tool that leaves a rough bottom, you have to fill those rough spots, or there will be bubbles.
I dunno what resin/catalyst ratio you’re using, but check it.
My process for the few leash cups I install (I prefer the glass fiber loop) is to router a snug fit hole, pour in some resin, stuff in the plug, and wipe off the excess.
NOTES:
Cabosil will act as a thickener, but it won’t add strength to the installation. The weak link in plug installation is the bond between the resin and the sidewalls and bottom of the hole you cut for the plug. Cabosil doesn’t bond to anything, so it doesn’t strengthen the installation. Thicker resin is a little less messy to work with sometimes. Other guys suggest short glass fibers, same comment. The ONLY way to make a stronger installation is to provide more surface area for the resin to bond to foam. This means a bigger, unsightly hole.
Ways to strengthen the installation: 1, if you overlay the edges of the plug with a couple layers of glass that will help a little bit. 2. don’t sand down the plug too much so that there isn’t enough plastic remaining over the little metal bar. I’ve had a plug fail by ripping the bar right out of the plastic. Very disappointing, but fortunately only a short furious swim.
With the lease plug hole to get a better bond between the plug and hole would it be a good idea to key the side walls of the hole with say a pencil end or some other blunt object and then to push resin into these areas with a paint brush just prior to filling the hole with resin? If you’re careful you should be able to avoid bubbles and have a neat small hole with plenty of resin to foam contact area underneath. I’ve done a couple of kiteboards like this and had no problems but am i risking any other problems? I also wet the plug with resin before i insert it into the hole.