Well…here’s why I don’t use fibers mixed in with resin to fill voids/dings.
It’s harder to sand, and the dust is itchy.
The fibers can leave voids, a less than perfect seal, which means air trapped in there with all the problems that go with that. I find that a cabosil mix, especially a slow-catalysed wet cabosil-resin mix, will settle in there nicely and any bubbles work their way out before it goes off.
And the fiber/resin mix is being stuck to foam…
Without being a wiseass, what good is it doing? The foam will give around the filler when whacked in any event, so the strength of the filler is really of no importance unless it was somehow weaker than the surrounding foam. It’s the glass you put over it that gives it the strength. The filler is just along for the ride.
Using resin plus fibers over the cloth that you cover the filler with- well, that is just gonna give you a hell of a lumpy hotcoat. Better to add another layer of cloth, no?
Anyone can fix dings. Few fix them properly. I’ve run a ding shop in so cal for the last 12 years. I am surrounded by 13 glasshops, so you could imagine that the majority of the dings I fix are brand new boards that get dropped or dinged while being built(yes, it happens).
The trick is technique. I noticed everyone saying that you can’t completely get the “bump” out, but you can somewhat blend it. Not true. It’s all in the preparation. You can’t just smooth out the area and start piling glass on top. When you go to feather it, the sander will just strip it back off. If a ding is on the rail(hopefully) you have 3 layers of glass to work with. Using a sander with fresh rough grit paper like 80 grit, remove not some, but all hotcoat in the area you wish to place the glass patch. You must not only remove all hotcoat, but go into the layers of glass a bit. If a ding is dime sized, you need to prep an area the size of a baseball. The patch(s) you cut should be exactly the size of the area you prepared. You’ll notice that your prepared area is now a low spot. This will be bridged back in with your patch or patches. It must be done cleanly, and you gotta use your eyes. Prep the right size, and cut your glass the right size. Don’t forget to use a squeegee to remove all excess resin from your patch, and press it down as flat as possible. I use 2 layers when fixing rail dings. If I get it on cleanly, both layers will remain after sanding, and there will be no bump. If it’s not so clean(happens) one layer will get stripped off while you re-shape your area, leaving 1 intact. Better if 1 is completely intact, and the top layer is feathered a bit. Dings on the flats are much more difficult(especially on the bottom) where you have only 1 layer to work with. Preparation is a bit trickier, and must be done with a medium or hard pad, and a fresh piece of 80 or 60 grit. The fresh paper sands cold. The last thing you want to do is heat up the resin and glass while you are prepping. This will actually remove material faster as it is soft now, and you just fry it off. The fresh paper shaves the hotcoat off cold with one quick pass, leaving the surrounding lamination intact and more importantly not overheated and melted. Deck dings are easier because you have 2 layers to work with.
For filler I use 2 types. “Sil-cell” and “cabosil”. Cabosil is clear, and used for vintage boards, or areas where there is color underneath you want to preserve. Sil-cell comes out off white or almost gray. I used to add white pigment, but with the new blue resin (with gray tones) the sil-cell blends into clear boards pretty nicely un-pigmented. Lastly, don’t use a soft pad to feather your dings. The soft pad will conform to the bump you’ve created with your glass patches, and just smooth it out. Use a medium or hard pad with fresh paper, and the sander will just automatically shave it flat, unless you got to far. Don’t put the sander on edge. Use it flat. IMHO all dings must be glossed(re-hotcoated). This just fairs in any leftover imperfections, and helps you get everything really flat. Hope that helps! Good luck!
Howzit Lokbox, Totally agree with you about blending the patch to the shape. I hate those bumps and in my mind it’s not a quality repair if there is a bump. One trick I use is before I Q-sel a ding is to use a bamboo skewer to make an indent under the edge of the glass so the Q-sel gets under the thin sanded glass edge. This puts some support under the thin sanded glass edge so when you sand the Q-sel you don’t go throught the frayed glass edge and into the foam, you can also use your finger nail instead of skewer. Aloha,Kokua
somewhat related question: what sort of protection is necessary? when you’re done, do you immediately hit the shower and wash the clothes you’ve been wearing?
Long pants and long sleeved shirt when possible. If not coat forearms with a little vaseline before sanding. I have a powerful dust collector fan, so I don’t get much on me!