How much G-Flex do I need for this?

Hi all, I want to repair this fine old Penobscot for a trip in several weeks. Both the bow and stern have a good bit of damage. I’d like to fair it out, then put Kevlar skid plates over it. How much G-Flex do I need for this? It’s expensive and I’d rather not buy more than I need.

Also, I have read that to fair out something like this, I need to add silica powder to thicken the epoxy. How much silica powder will I need, and where can I get it? Thanks very much.

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I just went through this for my OT Tripper. My recommendation is to call Sweet Composites and have them help you get everything together. I ordered 2 yards of Dynel fabric to make skid plates with (my recommendation to you as well, given the condition of your keel line), 2 yards of peel ply, 2 8oz g-flex kits (one the 650-K kit, which is what I’d recommend to you since it comes with silica thickening agent, syringes for spot filling, and gloves). I also ordered some graphite and gray epoxy pigment to add to the final coat of g-flex for additional abrasion and uv protection. I’m planning to do ~4’ x7" Dynel skid plates for two different canoes. You won’t need as much g-flex as me, but depending on how long you want/need your skid plates to be you may be best off ordering two yards of fabric so you have room to cut it on the bias. I’ll try to post links to the stuff I ordered here after a bit as well as several other internet threads that cover the process pretty well if you’d like.

I think @anon64780766 on here has done this a couple of times so you may reach out to him. But I do seriously recommend reaching out to the folks at Sweet composites in Maryland as the lady I spoke to there was very helpful in figuring it out just how much g flex and other materials I needed for my skid plates.


You have extensive wear completely through the outer solid lamina of ABS and completely through or deeply into the foam core over a large area. In one spot, you even have wear through the inner solid lamina of ABS with a through-and-through hole if I am interpreting the photos correctly. Obviously, the hull has lost a great deal of structural integrity over a large and rather critical area.

Can it be repaired? Sure, but whether it is worth doing so depends on how much you want the boat. The Penobscot is a desirable boat so it is probably worth doing if you have the time but it won’t be quick, easy, or cheap.

As for G Flex I would buy the 650-32 kit with 16 ounces of unthickened resin and 16 ounces of hardener. You need unthickened resin for bonding fabric but thickened resin is best for filling in the large defect in the foam core. But buying the 650-8 kit with 4 ounces of unthickened resin and the 655-8 kit with 4.5 ounces of thickened resin and 4.5 ounces of hardener will cost you nearly as much while giving you only half as much mixed epoxy. It is easy to mix silica powder into your epoxy to thicken it as much or as little as you want and it is not that expensive. If you buy fabric from Sweet Composites they also sell silica powder.

Filling in that deep defect with epoxy alone will not yield nearly as much strength as multiple layers of fabric in an epoxy matrix would. My personal preference for a repair of that type would be to first clean up the exposed core as best possible, then fill in all the exposed open cells with G Flex thickened with silica powder until you have a smooth surface to lay fabric on. I would then fill in the void with multiple layers of cloth making each subsequent layer concentrically smaller than the previous one until you have nearly restored the normal contour of the hull. You can then use a little more thickened epoxy to fair the hull surface back to normal.

I would also apply a patch to the hull interior where it has worn completely through. As for the fabric for the exterior and interior patching I would use fiberglass. S fiberglass is preferred but E fiberglass is considerably cheaper and will do the job. A Kevlar interior patch would be even better but I don’t think it is worth buying an additional type of material for a relatively small patch.

As for a skid plate I agree completely with DeepBarney that a Dynel plate would be vastly preferable to a Kevlar felt skid plate. Sweet Composites sells plain weave, 5 ounce/square yard Dynel that would work nicely for this purpose.


OK, more work than I thought. Thanks for the info, all. I greatly appreciate it!

I’m just curious what kind of canoeing the boat has seen to cause this wear? The rest of the hull doesn’t look that scared up for the amount of damage to the stems.

I have some stem wear that’s more than the hull as it takes the brunt of the hits, but there is a fair amount all over.

This almost looks like it was dragged over concrete holding the other end up.

Just my vote on fixing it. I would patch it up and use it, and if it is worth doing it is worth doing right.

I don’t know if there is such a thing as a metal skid plate. I would think such a thing could be made though.

Looks like it has been done. Not pretty, but the poster claims it did the job on rough usage.

Its cheaper than buying even a poor condition replacement and while a bit time consuming its not difficult. Sweet Composites is a good choice as they can provide solid advice as opposed to someplace like West Marine, where its all on the shelf, but the clerk probably has no idea what it is.

A friend custom fabricated a piece of stainless steel for the bow of his Coleman canoe. He put silicone or some kind sealant and pop riveted it in place. Probably worth more thsn the canoe!


Good question! The boat was given to a friend of mine as-is. Now that I see how much work it will be to fix it, I’m not surprised.

Looks like a lot of boat ramp beaching. Could be rocks on beach too. Or perhaps they just drug it from water to car across parking lot.

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I suspect you are right. Probably repeatedly dragged up a concrete boat ramp by the bow.

I used to volunteer for a nature conservatory that had an outdoor canoeing program and livery of Royalex canoes. We often had paddling events at local lakes with concrete boat ramps. The volunteers guiding these events did their best to prevent participants from dragging the boats up the ramps but it was impossible to completely prevent. I was surprised how rapidly this type of abuse resulted in abrasive wear through the outer vinyl layer and the outer solid ABS layer into the foam core.

I repaired many such boats that were only a few years old.