West Systems Plastic Boat Repair Kit

I have a small crack about 5 inches in length through the first layer of Royalex in the bottom middle of my canoe. The crack is not all the way through just the first layer. Im going to use West Systems Plastic Repair. Should I put down some Kevlar cloth then put some of the West Systems epoxy on top or can I just spread the epoxy straight onto the canoe. thanks

The West Systems G Flex 655K kit has thickened epoxy. Thickened epoxy is really not very good for trying to wet out structural fabrics like Kevlar or fiberglass cloth. Un-thickened G Flex can already be pretty viscous in cooler ambient temperatures and the silica thickening agent just makes it worse.

The un-thickened epoxy that comes in the 650K kit is much better for wetting out fabrics. Unfortunately, West Systems has chosen to call the 650K kit the “Aluminum Boat Repair Kit”. It can obviously be used to repair aluminum boats, but also plastic boats and a lot of other things. If you have not already purchased the 655K kit, get the 650K kit instead. This includes the same West Systems 406 colloidal silica powder that is used to thicken the resin in the 655K kit. You just stir some into your mixed epoxy to thicken it to your needs before applying the thickened epoxy glue to the boat.

The thickened epoxy is very good, however, for filling in cracks in ABS. The instructions that come with either the 655K or 650K kit are pretty detailed on how to go about this. I would strongly suggest beveling out the crack to its depth along its entire length so that it resembles a trough with a V-shaped contour. This is done to make sure the crack gets filled to its depth with epoxy and to increase the bonding surface. West Systems recommends pre-treating ABS with flame oxidation by passing the flame of a hand-held propane torch over the surface to be bonded. Again, this is described in the instructions. The epoxy will bond to ABS pretty strongly without pre-treatment with flame oxidation, but the oxidation process enhances the bonding strength. If however, the foam core of the Royalex is exposed anywhere, be very careful with a propane torch or omit this step, as the foam core will melt and deform very quickly.

Repair the crack as described. You can smooth it off fair and flush after the epoxy has cured. Obviously, the repair would be stronger if you covered the crack with fabric. Fiberglass is actually a much better repair fabric to use on the exterior of a canoe than an aramid like Kevlar is for several reasons. If you do not have un-thickened G Flex, or do not want to cover the repair with fabric at this time. wait until the epoxy is well cured, wash the area, and when dry cover it with paint,

Huge help! Thanks. The crack isnt in a spot that takes alot of abuse so i think i can skip the fiberglass cloth for now and just use the thickened epoxy in the 655k.

I repaired several cracks in an OT Disco I was given. I used Gflex without thickener and didn’t bevel the cracks which I probably should have done.
Many of the cracks were very fine though and the Gflex went right in. Many took several applications.

Being rather viscous, the G Flex epoxy settles rather slowly. If the foam core of a Royalex or three-layer, roto-molded polyethylene boat is exposed by a crack, the resin has to settle into the interstices of the core, and it almost always takes multiple applications to fill a crack. The settling process can be sped up by warming the epoxy by wafting a hair drier or heat gun over the area of repair, but be careful not to overheat. I find that it is usually best to slightly overfill cracks, then sand off the excess to get a completely fair and flush result.

Un-thickened G Flex will work to fill cracks, but the manufacturer recommends thickening the epoxy with colloidal silica powder or some other filler, to create an “epoxy glue” when bridging any gaps or when using epoxy for fairing holes or depressions. There are lots of different fillers. A moderate high density filler like the 406 colloidal silica powder is a very good thickening agent for structural repairs like bonding and filleting. A low density filler like the 410 Microlight works a bit better if one is trying to fair a surface to a high degree of smoothness. Here is a webpage that might be helpful in that regard: