I did a little experiment last night. I took four pieces of 3/8" x 6" x 12" balsa and laminated 3/4 oz glass to each piece. I used four different techniques.

1. applied peel ply over glass, then mylar
2. applied peel ply plus 2 pieces of paper towel, then mylar
3. applied mylar over glass
4. applied one coat of sanding sealer to wood, then mylar over glass.

I weighed the test pieces after I cut them. For piece #4, I let it dry one hour and weighed before and after. For all test pieces, I applied a measured 1/2 oz of West 2hr. epoxy directly to the wood, laid the glass on top and then matted the excess epoxy with a paper towel. I applied 20" of vacuum and left the parts in the bag for 12 hours.

Before weighing them after curing, I trimmed all excess glass to the edge of the balsa. Here is the additonal weight (above the bare balsa) for each part:

1. 1.7g
2. 1.7g
3. 2.1g
4. 2.1g (0.3g added by sealer)

Conclusion

1) Paper towel in addition to peel ply had no effect on weight in this test. I'm going to weigh the peel ply and paper towel+peel ply to see if more epoxy was actually removed. It could be that absorbing some excess epoxy prior to the application of peel ply negated any additional weight savings expected by the addition of the paper towel.

2) Sealing the balsa did not result in any weight savings due to the additional weight of the sealer. This test needs to be repeated with different sealing materials and different application methods.

QUESTION:

- What sealing material should I test and how should it be applied?

-Ben