Best Approach for this repair

This is a Old Town Discovery 119. What approach would you recommend for repairing this damage? The hole is punched through to the inside, but not too bad.

Flatten it out as much as possible and sand it off some. Brush epoxy on both sides and place a small piece of epoxy over each side. Brush another coat of epoxy over the glass cloth. Let dry. The next day brush another coat of epoxy over the cloth. Let dry again.

If it still looks lumpy put some Bondo on it and smooth it out. Let dry yet again, sand off and paint. Epoxy is not UV resistant.

Conventional epoxy and Bondo (polyester resin) will not bond to polyethylene, which is what this boat is made of.

West Systems G Flex epoxy will bond to linear polyethylene, but an adequate bond will only be achieved if you pretreat the surface with flame oxidation. This can be done with an inexpensive, hand-held propane torch and their are detailed instructions on how to do this in the instructions for use that comes with G Flex.

If you do not pretreat the surface of PE in this fashion, the cured epoxy can be easily flicked off the surface with a thumbnail.

What pblanc says, but I also have had good luck on plastic using the G-flex, and sanding (scratching) the plastic surface with a course sandpaper
Along with the fiberglass, I would add a filler to the G-flex.
Take your time and use as many coats of G-flex necessary to match the original surface. Then sand it smooth and paint it to match the original color with krylon plastic spray paint

This is bond strength data from West Systems for G Flex epoxy adhesion to various materials following different surface preps from their actual testing::

The data for high density linear polyethylene is for 655 G Flex which is moderately thickened with colloidal silica powder (cab-o-sil) and the bond strength number is tensile strength in psi:

HDPE, surface prep: sanding with 80 grit paper - bond strength 400 psi
HDPE, surface prep: sanding with 80 grit paper, flame treat - bond strength 1890 psi
HDPE, surface prep: alcohol wipe, flame treat - bond strength 2312 psi

Wiping the surface of the HDPE with alcohol and flame treating yielded a bond with almost six times the tensile strength that was achieved by sanding without flame pre-treatment.

Again, this data is for high density PE. G Flex will bond to other types of plastic (PVC, ABS, polycarbonate) much more strongly without flame treatment.

HPDE welding rod and a heat gun.

Thermal welding works best for single layer (solid) linear polyethylene hulls. In order to get a good weld, you need to heat the hull surface enough for the melted rod to mix with the material of the hull itself (around 300 degrees F for HDPE). You also need to be sure that your welding rod is not of much higher density than the PE material of the hull.

This is a three-layer, rotomolded PE hull. I strongly suspect that if you apply sufficient heat to the hull to weld the cracks in the external solid layers of PE, you will risk crimpling and deforming the inner foam core layer, which is much more delicate.

I’m not saying it is impossible to repair three layer rotomolded PE boats with thermal welding. I have heard of a couple of accounts of such repairs with acceptable results. I would not recommend it to someone who has no prior experience with thermal welding.

Thanks all, I ordered some G-Flex. Will post some before and after photos.

After you spread it on use a stiff piece of clear plastic film such as a note book page protector, or over head projector film and tape it on tight over it. The next day peel it off and you will have a nice finish that won’t require any sanding, except for the painting prep

What about duct tape?

@tnave863 said:
Thanks all, I ordered some G-Flex. Will post some before and after photos.

@magooch said:
What about duct tape?

Raisns did that after the shark attack. We carry “Flex Seal” tape. Fortunately never needed. It probably heat damaged. …and can’t be unrolled.