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I built a Tern last winter, and had a number of problems with this method as well. If I understand you correctly, bubble isn't between the wood and fiberglass tape, it's between the tape an mylar. You have a smooth surface over most of the joint, but the top surface of the tape weave is showing through. If this is the case, just brush on a bit more epoxy on top, hopefully within the 72-hour window where the epoxy will still bond to itself. To avoid this problem in the future, apply more epoxy to the joint before putting on the mylar. This will cause more to ooze out the side, but at least you will have enough to fill the tape.
I would recommend brushing epoxy on the joint, lay the tape down, brush some epoxy on top, let it soak a few minutes, then squeegee it to get bubbles out. Then add more epoxy on top and add the mylar and weights. Now that you have some practice, you should be able to do a bunch of joints at once. You have more time to work with the epoxy than you might think. I did all 4 of my Tern's hull (or deck) panels at once -- 8 joints.
If your bubbles are under the tape, this can also be fixed. Carefully drill a small hole through the cloth only, not down to the wood. Use one of the syringes that Pygmy supplied with the kit and inject some epoxy into the bubble. I used a 3/64" drill bit in a Dremel, but a 1/16" bit in a drill should work as well. The hole must be as big as the tip of the syringe because it takes a good deal of oomph on the plunger to force the air out of the bubble. You need a good seal, otherwise the epoxy will just come up to the surface rather than fill the bubble.
As a last resort, I've heard of someone pulling off the tape on the outside once the hull was stitched together. Use a razor blade or knife to get under the edge and rip the whole strip of tape off. It doesn't add much to the strength of the boat, it's mostly for providing enough strength until the panels come together.
One more note: Be extra careful anywhere there is more than one layer of cloth. I have some areas on my Tern where I think the epoxy may have been a bit foamy. Parts of the deck cloth where it overlaps onto the hull sides, the double-wrapped hull ends, and the keel strip look a bit yellowish. A few of the hull butt-joints look like this as well.
Happy building!
Dean
> I am just beginning my Coho. Following the Pygmy directions, the butt
> joints were first wetted out with resin, then the tape was applied and
> wetted out. A mylar strip was laid over the top and weighted down. I
> allowed this to set for about 12 hours at 75+/- degrees. After removing
> the mylar I found that several bubbles had formed under the mylar strip.
> While the tape is fully wetted out, I have several low spots where the
> resin is not level. I would appreciate feedback on the following points.
> 1) Is this normal - i.e. did I do something wrong? If so, how can I avoid
> this problem in the future? I have 2 joints completed, and 22 to go.
> 2) Should I fill the bubbles with a layer of resin, or just assume that
> when I put on the second layer of glass that the bubbles will fill in?
> Your assistance would be appreciated - there has got to be a better way to
> do this.
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Guillemot Kayak - High
Performance Wooden Sea Kayak Designs
