Audrey and I repair and restore a lot of boats, both wood and fiberglass, and in 2016 we restored an 1880s Mississippi River rowboat. The old boat was made of cypress and we needed a thickened adhesive/sealant product to bond on new pieces, fill some holes, and seal up areas where we had cleaned out rot. It had to be flexible to move with the wood’s movement through moisture changes, and it also had to have structural strength and to hold fastenings. It had to be easily faired, sanded, or shaped, and take to stains and oil-based or polyurethane paints. And just for grins, it needed to be rated for use below the waterline.

Flexpoxy can be dispensed through a static mixer tip and emerge from the tip ready to use. The cartridge fits a standard caulking gun and takes XX pressure. The tip can't be allowed to sit idle for long—mixed epoxy with begin to cure and become too thick to flow. At the end of the job, the tip has to be discarded and a bit of epoxy goes with it.photographs by the author

The Flexpoxy cartridge fits a standard caulking gun and can be dispensed through a static mixer tip, emerging ready-to-use. The tip can't sit idle for long: Mixed epoxy will begin to cure, becoming too thick to flow. At the end of the job, the tip has to be discarded and along with a bit of waste epoxy is lost with it.

With these requirements in mind we found our way to Flexpoxy, a thickened epoxy that comes in a 250mL, two-part cartridge that fits a standard caulk gun. Flexpoxy comes out clear on one side of the nozzle and a light purple color on the other, then turns a translucent white when it is thoroughly mixed. It is very convenient to have the cartridge dispense the proper amounts without having to measure the two components to get the right ratio. The resin and hardener can be dispensed through a static mixing tip and applied directly to the work surface, but what we like to do is dispense larger amounts onto a palette without the tip, stir it up, and apply it to large surfaces that needed to be bonded. To fill small checks in planks, we'll trowel mixed Flexpoxy into a small syringe. Flexpoxy is highly viscous and doesn’t run, so there is no need to mix in fillers to keep it from sagging. We’ve used it without any additives for filets. The resin/hardener mix has a pot life of 20-25 minutes, sets in 3 hours, cures in 16 hours, and dries clear.

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