You could use the above mentioned products to repair the bearing edge but it will still affect the sound of the drum. The dissimilar materials have different characteristics, and they will also crack and fall off over a couple of years. Especially if you use bondo.
The best thing to do is to completely file and sand the damaged area away until you are left with the natural shape of the shell - minus the damaged area. Do not use fine grain sand paper or fine toothed file at this point. Go with a rasp or really coarse paper so it will make a good bonding surface. When this is done make sure all the dust is removed from the surface and it is clean.
You will need to get some fibreglass strand and fibreglass cloth and some two part epoxy. I recommend "West System" it's expensive but good. But don't go for anything that's too fancy (like marine epoxy for example) because you will be trying to match as close as possible the material that was used to make the shell. Follow the mixing directions for the hardener/catalyst and resin very carefully because if you put too much hardener the batch will cook off and will be all kinds of trouble. Not enough and the resin won't cure. Don't mix more that you can use in one session and if it does start to harden stop using it and mix another batch after the current layer has cured. If you use MEKP as the catalyst make sure you read the safety sheets very carefully because that stuff is NASTY!
You apply a thick layer of resin on the surface and then blend in the strand completely so there are no gaps or bubbles. Then you apply another layer of resin and apply more strand. Do this until it looks like the gap is almost filled in then apply one last layer of resin and then put the fibreglass cloth over it and at this point you REALLY have to make sure there are no gaps or pockets. Then put some more resin on the surface to finish it. Some people like to lay a sheet of thin plastic over the wet surface and work it over the surface to give it a very smooth finish once it has set, or you can just use a gel coat that is color matched to your shell. Either way, you will still need to do some sanding and filing to produce the bearing edge of the shell.
If you have never done fibreglass repair before, practice on something that is similar first to make sure you get the technique down. It's not that difficult. It would be good to do some more research first as well because this is just a quick description of a basic repair, but there isn't really much more to it than that.
Make sure you use rubber gloves when handling the materials and use a dust mask when sanding and filing the finished surface. And ferchrissakes keep your fingers outta yer nose and eyes when you are handling this stuff!
The tools you will need will be a small fibreglass roller ( it has ridges on the roller, not flat) to apply the layers, a spreader and/or disposable paint brush (1 or 1 1/2 inch), some mixing sticks, coarse sand paper (80 grit) or a rasp, fine sandpaper (180 or 220) for finishing, maybe some thin plastic sheet if you want. And don't forget your safety equipment! It's best to do this in a very well ventilated area because the fumes are strong and the sanding produces fine dust.
Once I learned how to do this I wanted to go around and "fix" everything I could with fibreglass until I ran out of materials and was left with the resin coated tools. They clean off well with acetone while the resin is still uncured.
Posted: Sun Mar 27, 2011 10:04 pm
