JEFF STROUT

When you ding your plastic kayak, epoxy can patch it

Posted July 29, 2011, at 7:38 p.m.
These are the materials you’ll need to fill a gap in a polythelyne kayak hull. The bottle cap was used as a measure and the plastic cup as a mixing bowl.
These are the materials you’ll need to fill a gap in a polythelyne kayak hull. The bottle cap was used as a measure and the plastic cup as a mixing bowl.

If you paddle a kayak in Maine, chances are pretty good you’re going to scratch up the bottom of your boat. Occasionally you’re going to do more than put a scratch in you hull.

And when that deep ding happens in a polyethylene (aka plastic) hull, how do you keep it from getting worse?

I recently purchased a used tandem kayak. Everything about it seemed to be in pretty good shape. What looked loose could be tightened. A part or two here and there was replaceable. Even the bulkheads could be resealed in the few places they looked separated from the hull — Lexel sealer to the rescue.

It wasn’t until after I’d cleaned things up, sealed here and there and replaced the small parts that I took a hard look at what turned out to be a deep ding in the bottom of the hull. When initially I’d looked over the boat, I didn’t realize that the ding was more like a gash that was much of the way through the hull material.

It didn’t leak, and if I didn’t do anything about it, it probably would never get any worse. But I didn’t want to take that risk — not on the ocean.

The gash would be filled — but how?

There are folks out there who “weld” polyethylene. It involves a torch to heat the hull material and melt a plastic filler, much like the process of welding metal. But heat deforms plastic if the process is not done right, and with my luck, trying to do the job myself would end in a big porthole right in the middle of the bottom of the boat.

No, that wasn’t going to happen.

After some searching on the Internet, some email exchanges with customer service folks at Wilderness Systems, NRS and West Systems, I decided on using G/flex 650 epoxy from West Systems.

It’s a two-part epoxy — like most are — that consists of a resin and a hardener that are mixed in equal parts. The beauty of this product is that it sticks to polyethylene (many brands won’t). Once mixed it has about 45 minutes of working time, and up to 75 minutes to assemble and clamp (if you are joining two surfaces).

Surface preparation is straightforward: Rough up the area with some 80-grit sandpaper, clean the area with alcohol and a paper towel and then pass a torch over the surface at the rate of 12-16 inches per second (you’re not melting anything, just oxidizing the surface for better adhesion).

These steps completed, I mixed a soda bottle capful each of the resin and hardener in a small plastic cup, stirred it up and set to dribbling the mixture into the gash.

Not having done this before, I learned that while the mixture may look and feel sticky, it still will flow. Hence I had to level the hull to keep the goo from running out while it set up. Nothing major, but I should have done that before I began dabbing the mixture into the gap.

In a few hours the epoxy solidifies, and it reaches a workable cure in 7-10 hours. The company suggests you wait 24 hours before subjecting the repair to “high loads.”

It’s done and although you can clearly see the small area I filled, it’s looking and feeling as strong, if not stronger, then the rest of the hull. I’ll bet that if I had thought the process through, I’d have found some yellow plastic dust to mix into the epoxy and then you’d hardly notice the repair.

Then again, it’s on the bottom, and I don’t intend to have my head under the boat that much. I think I can live with the minor blemish. Heck, after a half-dozen more landings on any Maine beach, it’ll be hard to find the repair among all the other scratches.

My confidence in this repair was bolstered by a video by West Systems that I watched. The guy in the video used a chain saw to cut a recreational kayak (a Wilderness Systems product) in two, right through the cockpit. Then he used the G/flex epoxy to fasten the two halves back together and later put the boat back on the water and paddled it.

When I was making inquiries to a West Systems technical representative I happened to mention this trick, and wouldn’t you know, he was the guy in the video, and no, it wasn’t a trick, and the boat was still in use.

Not only is it recommended for plastic (ABS, PVC, HDPE, LDPE and polycarbonate-Lexan) it works on fiberglass laminate, aluminum, steel, copper, bronze, lead, teak, white oak, walnut, purpleheart and greenheart. The company sells an adhesive filler that can be mixed with the epoxy to fill uneven mating surfaces.

West Systems sells the G/flex epoxy in the following product numbers:

• 650-8: Two 4-ounce bottles of liquid epoxy (one 4-ounce resin and one 4-ounce hardener) in a plastic bag. Retail price $17.97.

• 650-K: Clamshell kit containing two 4-ounce bottles of liquid epoxy (one 4-ounce resin and one 4-ounce hardener), 2 mixing sticks, 2 syringes, 4 mixing cups, 406 Colloidal Silica, 1 pair gloves and 4 alcohol pads. Retail price $23.68.

• 655-K: Clamshell kit containing two 4.5-ounce aluminum tubes of thickened epoxy adhesive (one 4.5-ounce resin and one 4.5-ounce hardener), 2 mixing sticks, 10 mixing palettes, 1 pair gloves and 4 alcohol pads. Retail price $27.35.

For a more technical look at the characteristics of this Gougeon Brothers Inc. product see: http://www.epoxyworks.com/25/pdf/Understanding_Flexible.pdf

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