So, rookie mistake here. I did some fiberglassing when it was a little too cold. The weave looked fully wetted, but now that it is cured, there are a some areas where if I get very close, I can see tiny air bubbles trapped in the weave. From farther away they are not visible, even the color is constant, it does not look milky or foggy. I tried getting a photo but it isn’t really visible.
I’ve tried Sanding down in a couple test areas and it is clear it is tiny air bubbles (size of a piece of sand maybe, but sometimes concentrated). But my question is: should I sand out and rework all these areas? It is not a cosmetic issue as the area is not visible on the boat, so it’s a pure risk assessment for structure.
if you have no discloration (not milky or foggy) and your glass is fully wetted out you should be fine. if the tiny bubbles are trapped in the weave, to sand them out you would go into the weave and then need to do a glass repair. based on your description, my insitnct is to leave it as is. from a structural perspective, if you are following standard build instructions, there is plenty of strength margin for us ‘amateur’ builders…so something like this is not likely to make a difference. to the extent you want to provide additional details as requested by laszlo, please do…and we can reply with more specific thoughts.
You should be fine. The main stress the inside has to take is compression which the tiny bubbles won’t affect. As Howard said, no discoloration, no problem.
I see that the boat uses 6 oz cloth. For cloth that thick I like to put it on a table covered with polyethylene sheet, wet it out completely and only when I’m happy with it move it over to the boat. By separating the lay-up into 2 tasks - wet out and lamination - instead of trying to do it as one, I find that I can pay attention to each phase better than trying to worry about everything at once. Consider that for next time.
another technique that i use when building during cooler months, is to seperately warm the epoxy. i am currently building in a ~ 65 degree work room but i keep my epoxy in a convenient-to-move box in the main house which is a bit over 70 degrees. before major glass work, i pre-heat my epoxy with a little space heater to the high 70s…where it becomes quite liquid and easy to work with. the downside, of course, is it can go off quicker…but in terms of wet out and not having bubbles, hotter/thinner is better.
If you are starting cold and it warms up as the epoxy cures, air will come out of the wood and create bubbles. If that is your case, try working when temperatures are steady or dropping. Or try warming up the wood before applying the epoxy.
So I’ve made some changes, and we’re getting better. The very small air bubbles are mostly gone. But, we have a new type of bubble now. Here is a very zoomed closeup. The size is something between a poppy seed and sesame seed. What I had before was more like poppy seed or smaller.
Any ideas on what I might be doing that leads to this? For now I just sand it out and cover the area with another layer of epoxy but this is a pain.
Typical routine:
arrive to cold room, heat up room for a couple hours
afterwards heat up boards and epoxy
Apply fiberglass and first layer of epoxy
Let sit a couple hours
Apply second layer
Turn heat to minimum and let temperature slowly drop.
Im pretty certain at this point that it’s outgassing. I’m running some tests with different heating cycles to prove it, but optimizing the heat seems to be slowly improving things. Let’s see.
