Epoxy fill coat

�I've applied 3 coats of epoxy and I'm wondering if it's enough. I can still see the outline of the weave in some spots although it looks covered. Other parts are glossy. Also, can use a roller instead of a brush? Thanks

7 replies:

« Previous Post       List of Posts       Next Post »

RE: Epoxy fill coat



Seriously, check out this shop tip about filling the weave:


and I really prefer rollers to brushes, they let me apply thinner coats.



RE: Epoxy fill coat

If you've applied epoxy with a brush, chances are you have more than enough to fill the weave.  See this:


Applying epoxy over glass builds up layers that follow the contours of the underlying glass fabric.The layers pile up and the early ones are still bumpy. But they keep getting higher and higher. The critical question is "Are the valleys in the applied epoxy higher than the tops of the underlying glass?" If the answer is yes, you're golden. You will reach this point before the surface of the epoxy becomes uniformly smooth.

Unfortunately there's actually no way to tell if you have enough epoxy on there to reach the critical level. So start sanding to prep the boat for paint or varnish. If you get down to the glass in spots - well, your epoxy wasn't thick enough. Stop sanding and put on more epoxy. Let it cure and resume sandng. No biggie.

Brushes apply resin lots thicker than rollers (yes, you can use rollers). So if you've been brushing it on and your surface is mostly smooth, it's likely you have too much epoxy on already. Too much epoxy = extra weight unless you sand it off. If it were mine, I'd start sanding.

RE: Epoxy fill coat

���..."Are the valleys in the applied epoxy higher than the tops of the underlying glass?" ... That sums it up well for me. Thanks gents

RE: Epoxy fill coat

Agree on the rollers vs. brushes for subsequent coats; thin is the goal but as uniform as possible.

For laying down epoxy in fiberglass cloth I'm a fan of using those inexpensive plastic squeegee blade things. You don't want to press so hard that the 'glass cloth moves, but with slow even strokes you can make the epoxy move around so the cloth gets saturated quickly before it tends to puddle.

Subsequent resin applications for weave-filling benefit from the speed with which epoxy can be spread. Too, a squeegee's straight edge helps it end up more in the hollows in between 'cloth yarns rather than on top where you'll be wanting to sand it off later.

Brushes to my mind are fine for structural applications like wetting surfaces that are to receive thickened epoxy before being joined, or for wetting out surfaces that will get fillets next. For large areas there are more appropriate tools available.  

RE: Epoxy fill coat

 My 2 cents,

I've taken to brushing then squeegeeing the first fill coat. It goes on really fast, does a really good job of filling the weave, and leaves a surface that does not need much sanding. And, it doesn't leave air bubbles that need to be tipped out or the mess of removing the roller cover.


RE: Epoxy fill coat

   If you are seeing the weave this may be because your first coat either didn't fully wet through or because the wood pulled the epoxy away from the cloth as it cured.  If you can see the weave and have a glass smooth surface finish this is what's happened.  A fill coat on bare wood is recommended before applying fibreglass to prevent this and outgassing during cure, wish I'd known earlier...

RE: Epoxy fill coat

Glad you posted that Simpsonboater yet I've been advised pre-coating isn't always a good idea.

60% along on my Waterlust build (with 70% to go it seems) I'm approaching getting the deck pieces assembled then 'glassed on the bottom-side before bonding it to the completed hull. I'm going to try the pre-coat for the first time when I 'glass the deck's bottom, see whether it's worth doing on the upper surface once I get to that stage.

I 'glassed both the inner & outer hull surfaces with the bare 'glass cloth stretched smoothly in place before pouring on the epoxy. It all went down OK w/ no 'float' or dry spots but I did note significant minute bubbling despite careful attention to temperatures. Sanding outer hull less nettlesome than on the inside with all the corners & tightish areas to get into.

« Previous Post     List of Posts     Next Post »

Please login or register to post a reply.