Here’s a cool video on the subject. Composites are a huge rabbit hole
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It’s my understanding that you want to sand up to a relatively high grit during surface prep (400~800). This gives the epoxy a flat surface to adhere too, but not so flat that it’s slick.
(Really important to remove all the dust with a lint free cloth and a solvent)
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Thanks guys
There’s a bunch of variables and degrees of perfection
bonding fiberglass to cured fiberglass, I like sharp 120 grit, X pattern, sharp new sandpaper on each pass.
Fiberglass to wood, i Usually scrape wood with a razor blade to make wood shine, and not push sanding dust into wood pores, and perhaps block ability of epoxybto penetrate deeply.
Polishing epoxy to a perfect gloss, can be a lesson in frustration. as unless final layer of epoxy was uniform thickness, and fisheye free, one would see imperfections far too easily.
On surfboards I didnt like adding clear coat or poly u finishes as they would make inevitable repairs difficult.
My finishes Id wetsand to 2000 grit, tthen smear a tiny amount, less than 10 ml more epoxy over the whole deck or hull with a clean sterile sponge. This unconventional ‘smear coat’ would dry glossy, but not as perfect as a polyester finish that was polished with compound.
Epoxy has such incredible bond strength one can get away with a lot of less than ideal surface prep, but its best to take steps to insure amine blush or super glossy cured finishes dont impair secondary bonding.
Well after final kayer of epoxy fully cured on my surfboards I might buff it out, but once I had to completely refinish a wood board as it turned cloudy a month after buffing.
Ive made lots of foam and hollow cedar surfboards and wood fins, but only the one esk8 enclosure so far, and my skills rusty
I worked in a boatyard for a bit too, mostly polyestervresin, but everything is so toxic, once I learned how they did things, I moved on.
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Appreciate the inputs!
I’m using West Systems 105 with a slow hardener. The first skin I did with CF turned out pretty well but it did have some micro bubbles which I would attribute to the above. I basically pushed all the excess resin out on that skin and left the surface with the texture of the CF.
Some small blems
I’ll try what you’re suggesting to see if that can result in a more uniform finish. It’ll just soak in on its own? No need to push it into the weave? TBH I was considering using a peel ply (or just a sheet of plastic) to force the excess epoxy out and leave a consistent finish.
Board is prepped
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Good luck!
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With CF, it is difficult to tell when it is truly fully saturated, and not oversaturated.
The correct amount of squeegee pressure to apply depends on a lot of variables such as the cloth itself and the viscosity if the resin, and the firmness of the squeegee/bondo spreader.
I think one should aim to fully saturate the cloth and then use just enough pressure to flatten cloth to substrate, removing excess resin, but not desaturating the cloth with too much pressure.
Just enough squeegee pressure from middles to edge to stretch cloth tight and removee excess resin with out desaturating, or working the excess epoxy into cloudy froth.
If edge of squeegee has white frothy epoxy attached, scrape it on a dedicated container for frothy whitened epoxy.
Repurpose it on something where cosmetics is not an concern, just sealing or gluing.
With Fiberglass, it is easy to see when one uses too much squeegee pressure and desaturates the cloth, but with CF it is not.
I’ve only experience with hand layups, not vaccuum bagging so…
I do sometimes lay freezer bag style plastic over epoxy and will work a squeegee on the plastic to stretch cloth tight and push excess resin to the edges, I call it the poor mans vaccuum bagging technique, but results can vary widely.
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Fiberglass was folded of course. And the mesh is totally screwed up with holes and creases.
Anyone link where to buy low volume rolls of fiberglass?
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At least hot glue method seems promising.
Really bummed about that Fiberglass. Was hoping it would be sold on a roll like CF is, seems to be a universal complaint when buying low volumes. I can get the folded stuff locally at AutoZone
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If you can lay the cloth in a flat surface, and pull the same strands on opposite sides, it is possible to return it to a much nicer state.
A clothes iron can flatten the memory of the folds. no steam.
I used to be able to drive to their oceanside stick and brick store to buy Epoxy, and various styles of Cloth from and onto a roll.
Last Year I had to order and have delivered 1.5 gallons of their Apex epoxy to Florida.
I could likely have sourced locally, but I am used to working with this specific epoxy
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Its pretty wrecked in some areas 
not even cut straight and the edges are super frayed. It’s gonna go back lol too many holes to fix.
Carbon Fiber is packed so much nicer.
I found these guys but shipping is a killer:
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Try this outfit.
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Not sure if this helps, but my go-to source for composites is US composites
I’ve heard totalboat sells good stuff too
I emailed Thayercraft but didn’t get any response. Ultimately I purchased a 4oz cloth 50in x 10yd roll from High Quality Fiberglass Cloth| Fiberglass Fabric Online - Fiberglass Warehouse
can still see where the small bubbles are
hot glue came out, was tedious but not too bad
kinda glad I used 4oz cloth, I think any thicker and I wouldn’t be able to see the insert holes.
one coat filler primer
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