Crack in cowling, best way to repair

I have a Perception Tribute (Rotomolded) that has two cracks in the cowling, right behind the seat, about a foot apart. I was recently at Canoecopia and talked to the Rep at the Perception booth. He said the cracks probably happened because I had the seat all the way back and was leaning against it too much. Anyway, he recommended G-Flex to repair it so it doesn’t get worse. I’ve been watching some repair videos and one of the steps is to use a torch to prep the surface. I’m really nervous about using any open flame near my kayak. Could I use a heat gun at a low-med setting instead? I’m really just interested in making sure the cracks don’t get bigger, not as much with aesthetics.

I used G- Flex to repair cracks in a canoe hull. The directions say to have the components at room temperature. Also, heat the surface to be repaired to moderate temp.
A hair dryer s/b fine.

No matter how you repair it drill 1/4" hole at end of crack. Even 5/16" or 3/8".

Edge of cockpit is called combing. I think you mean than? Hole stops crack from continuing. Works in fiber glass, plastic & metal. Works on plastic garbage cans.

Leaning should have never caused cracks. Sitting on the deck might.

I think I would try some jb weld, my old perception mirage has a small crack in the cockpit rim, someday I’ll get around to fixing it

You’d have to keep the flame of a propane torch on there for a LONG time before it caught on fire. From what I’ve read, quickly passing the torch over the surface changes it and allows the adhesive to bond better. It’s just a quick pass from what I’ve seen. If you’re charring the plastic you’re too close and/or sitting in one spot too long.

Caveat: I’ve never done this myself, but I’ve seen it on YouTube. :wink:

There you go; If you can’t find it on YouTube, it probably can’t be done.

You can use a heat gun. Definitely stop drill the crack. If you don’t do anything else. It can also be welded, but you are reluctant to do that.

Sparky is correct. The flame makes a chemical change in the plastic surface to facilitate bonding and yes, it requires just a pass with the flame. There is a video by West Systems that illustrates G Flex repair of poly. I’ve done it several times. It’s not a big deal. I love G Flex. It bonds tenaciously.

@Seadddict said:
Sparky is correct. The flame makes a chemical change in the plastic surface to facilitate bonding and yes, it requires just a pass with the flame. There is a video by West Systems that illustrates G Flex repair of poly. I’ve done it several times. It’s not a big deal. I love G Flex. It bonds tenaciously.

Me too.

A heat gun will not work. Polyethylene is chemically inert and epoxy won’t bond to it unless some of the hydrogen molecules forming its exterior structure have their electrons stripped away by some sort of oxidation process leaving electron-hungry protons which will bind with the resin molecules. Oxidation can be done chemically or through flame. Chemical oxidation is often used in industrial applications but for home repair, flame oxidation is much more practical.

Before applying the epoxy, bevel the edges of the cracks on both sides if possible. The instructions with the G Flex epoxy explain how to do this. This greatly increases the bonding surface for the epoxy.

You need an inexpensive propane torch. Do the flame oxidation after abrading the surface you want to bond to and cleaning it well with denatured alcohol, allowing the alcohol to fully evaporate first. Have your disposable gloves, masking tape, epoxy mixing cup, epoxy applicator, etc. ready to go.

Do this in light where you can clearly see the inner blue cone of the flame of the propane torch. You want the tip of this inner blue cone to pass relatively quickly over all surfaces to which you want to bond to. The goal is not to heat the surface, but to oxidize it. Most rotomolded kayaks nowadays are made out of some variety of linear polyethylene which will melt if too much heat is applied. Cross-linked polyethylene will start to spark if too much heat is applied. The flame oxidation is temporary. If you wait too long, the protons will find electrons elsewhere, so you want to apply your epoxy as quickly as possible after flaming the surface, and within 30 minutes at the outside.

Back up the cracks on one side with clear plastic packing tape as you apply epoxy from the other. For filling and gluing cracks I would thicken the epoxy moderately with silica powder. You can buy a kit with a small amount of G Flex resin, hardener, silica powder, mixing cups, applicator sticks and dental syringes that goes by the name “Aluminum boat repair kit” 650K for just over $30 which will have most of what you need. You may need to make several small application of epoxy on both sides to completely fill the cracks flush with the surrounding surface. You can sand any overfill down after the epoxy is cured.

Personally, after filling the cracks, I would back up the repair on the inner side of the coaming with a strip of fiberglass. Use unthickened G Flex epoxy to wet out the fiberglass cloth and fill in the weave. Paint the exposed areas of epoxy after the repair to protect it from UV degradation.

kudos for giving us an explanation that went to the molecular level. seriously good reading