Another data point for the historic 4oz vs 6oz debate; did some acrylic paint testing for some board artwork and also experimented with the lam sched. I took a piece of EPS foam and cut it into two 12”L x 6”W x 3”Th “blanks” and sealed both with RR epoxy/Q-cell mix. Starting weight for both was 3.6 oz. Weight gains (measured on a digital food scale) were as follows:
After glassing the bottom: 1x6 +0.7oz, 2x4 +0.9oz
After glassing the top (did all layers in a single lam): 2x6 +1.5oz, 3x4 +1.6oz
Fill coat the top: 6oz +0.6oz, 4oz +0.5oz
Total gain (note - did not fill coat the bottom): 6oz +2.8oz, 4oz +3.0 oz
End weight: 6oz 6.4 oz, 4oz 6.6 oz
Note that the weight of a pencil is about 0.1 oz.
Based on the data above, a very rough projected final weight estimate for a 6 ft board is about 6.5lbs for both glassing schedules, probably within ¼- ½ lb of each other, not including laps, fin boxes, gloss coat.
On the artwork; my trusty assistant painted flowers with acrylic craft paint on rice paper which after being allowed to thoroughly dry (2 days) was then roughly cut out around the artwork and inserted during the lam process under the top layer of glass after wetting out the bottom layer(s). No bleeding of color and the paint thickness from the brush work did not interfere with lamination. The advantage to this over just painting on the board is the ability to paint on paper; mistakes are more easily fixed (just re-do), and the artwork can be done ahead of time prior to the board lamination tango.
Hope that helps, I’m totally in the 4oz camp now btw.
Okay, dumb question. You say you used RR epoxy to seal each ‘blank’; so I’m assuming you did all the other glassing with epoxy as well?
I’ve used acrylic paint on rice paper twice; glassed over with epoxy. One worked fine, the other did not: clear indication that the epoxy was not having it.
The difference between the two? The wait time for the paint to dry. The one that worked I waited a good 24-48 hours before glassing. The one that didn’t work I only waited maybe 10 hours.
I’m glad somebody else has found good results, I’ll be doint the acrylic/rice paper lam again.
That’s quite the experiment. But while it might suffice to use one layer of six in some applications, one layer of 4 oz wouldn’t do the same job. So you would be talking about schedules of combined 4&6 or double layers of 4.
Good to see this. My conversations with glass suppliers leads me to believe multiple layers of lighter glass equaling the same weight as a single layer will be bioth stronger and tougher. I believe in the archieves of the " Hot Seat" Chris from GraphiteMaster touched in this. A good data point is G10 glass panels made of compressed 1 oz (I think).
Yes all glassing was done with RR epoxy resin, and agree on the acrylic paint dry time; it’s gotta be totally and thoroughly dry. And yes this was a 1x6B & 2x6T vs 2x4B & 3x4T comparision. Thanks for the feedback! It’s amazing how thin those layers are. BTW the dimple in the eps foam on the bottom right was a quick squirt of acrylic clear spray paint, not gonna do that again!
Acrylic is a bit of a misnomer, it does not mean water-based in all cases. Rattlecans that have toluene and acetone are hazaradous to EPS. Good for you learning this on a test panel. It’s a joke among painters to send the ‘kid’ out of the booth for some acetone in a styrofoam cup. Mine knew better…
Much of the weight differences in epoxy glassing is due to the type of EPS and sealing. If you seal EPS with a very runny epoxy slurry, how much it drinks up depends on the bead sizes and how the slab/blank was molded. This has to do with the air spaces between the beads. The air spaces are dependent on how the EPS is squeezed (which determines density) which is way different between slabs and molded blanks. Some of the lamination coat will always drain into the blank and increase weight. It is safe to say that any further laminations after the first one will drain much less, but multiple layers done once would drain the same (or more) as one.
So for a very strong light board, good epoxy sealing and multiple laminations done separately (light sanding between) works. Molded EPS tends to be denser on the outside like a skin, so sealing is better. Whether 4 or 6 oz cloth is used, the strength of the glassing doesn’t matter if the bond to the EPS is lost. So, some draining into the blank is needed to anchor the laminations and that’s why vacuum-bagging makes such strong boards. Obviously using epoxy + filler as a sealer forms a chemical bond to the lamination. This ain’t going to happen with any water-based sealer, the best you can hope for is some mechanical bond or a degree of epoxy permeation through the filler (after a lot of drying first). Same thing applies to acrylic paints. Once all the water is gone epoxy will permeate (somewhat) through it and you’ll get a bond.
