I’m glassing the interior of my Mill Creek 13. I plan on one more fill coat. Then a coat of Epoxy and Microballons. I would like to wait 24 hours before applying the Microballons if possible. Mo I’m using MAS epoxy and the temp is 70-76 with 66% humidity. What would be the maximum time that I could wait before having to sand?
Ideally, MAS should provide that information. But, if it’s not readily available, my rule of thumb is that if I can dent it with my thumbnail it’s not fully cured so I can skip the sanding. That automatically takes care of the temperature variable, too, but it’s not so good at predicting. With your conditions I’d say you’re good for at least 3 days or so.
Also, note that if you’re using microballoons, you don’t need separate fill coats. My usual procedure with microballons is to apply a thick coat right after the first layup while the weave is still showing and when it’s cured, move directly to the final fairing step before painting. This can save days.
Have fun,
Laszlo
Thanks Laszlo your response was just what I was needing. Most of the time I just add 3 coats/day with 3-4 hours between coats. Glassing the interior was a lot of work since I applied one straight epoxy fill coat which now I’m wondering if I just made more work for myself. I was afraid that I would sand through the Microballons into the glass but now I’ve got an extra layer of epoxy to deal with.
I’m thinking about sanding some of that layer down to get a smother surface to apply the balloons. I have a lot of errant strands of glass that will need to be sanded first. I do what maybe looked at as an unconventional way to glass the interior.
Balloons don’t need a smooth substrate. They become the smooth surface. Don’t worry about the fill coat you already did. Just be aware there’s no need for another one.
You’re absolutely right, I woke up this morning and looked at the boat realizing the first lay up was better than the second fill coat. Hope I remember this on my next build, thanks!
Why do you want a smooth interior? Just adds weight
I’m building a Mill Creek 13 which is an “open” cockpit kayak. The interior is very visible. The additional weight is marginal. I’ve weighed the glass for it and it came in at 21.8 oz/1.3lbs. I like sandwich construction which adds considerable strength and abrasion resistance over glass on just one side so it is for much more than aesthetics. Since I would coat all of the wood with 3 coats of epoxy anyway I probably added the equivalent of one extra coat of epoxy overall. I’ve included a photo of my MC 16.5 interior before adding the deck.
Got it. That makes total sense. But the amount of resin to wet out the cloth and fill the weave (even if microballons are used) is probably 2-3X the amount required to roll three thin coats over bare plywood. But I agree an open boat like this needs to have a smooth interior.
I wanted to weigh the boat before and after I glassed the interior but I literally got too busy and forgot. I would imagine that the added weight would be 3-5 lbs. max. I used a roller to apply the resin that allows a very lean resin to glass ratio if one presses the roller very heavily into the glass. In fact I used a roller extension in order to use two hands.