Repairing Royalex damaged spots

Hello everyone,

I recently purchased my first canoe, a used Old Town Penobscot 16. There are some things I’d like to fix and update, but these spots are my first priority as they need to be patched up. I’ve read several similar Royalex repair posts but I want to make sure mine is the same before doing anything as I am new to repairing this and don’t want to mess it up further. Are the areas shown the inner ABS layer or is that the foam layer? If it’s the ABS, can I just fill with G-Flex epoxy, sand and then paint over or will I need to add a fiberglass patch as well? Any help is greatly appreciated!

It is hard to be certain from your photos but I think what you are seeing is the outer solid layer of ABS where the green outer vinyl layer has been abraded away. But the farthest outboard area of where looks a bit worse. I don’t see anything that is obviously exposed foam core but you should be able to tell by looking at the boat in the flesh. The foam core will have a very trabecular or “spongy” appearance.

However, even it there is no exposed foam core at this point the outer solid layer may have been thinned out by abrasion. I would push in firmly with your thumb over all of the tan areas. If any feel spongy then the outer solid ABS layer has been thinned. If that is the case I would probably apply an abrasion (skid) plate. Otherwise you can just clean it up and paint the areas of exposed ABS to prevent UV degradation. Any paint that closely matches the color of the vinyl would be OK.

The Kevlar felt skid plates are very popular. Personally, I hate them for a number of reasons. If you do need to apply an abrasion plate you might find this thread on another message board to be helpful: Skid plate suggestions - Forums.

Search for some good info.
Kevlar felt is heavy, ugly, slow and decreases your rocker.

Thanks for all of the info! Definitely a big help. So it does seem that the ABS layer is in decent shape. I gave it some hard presses around each spot and all felt fairly solid. So all I really need to do is paint at this time? Cool, thats why I asked as I was ready to epoxy everything! I’ll keep an eye on the area after I fix it and if I start banging the area up more, I will have to do consider a skid plate.

If the areas of Royalex that are denuded of exterior vinyl look intact and feel solid to a firm press I would just cover those areas with paint.

Would it be worth it to clean it up and apply some bondo before painting just to give it that smooth finish again?

I’m no expert but I would say Duraglass maybe Bondo not.

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I’ll have to check out duraglass. I’m not too familiar with bondo in the canoe world but couldn’t think of an alternative.

I would not use Bondo or any other polyester resin on ABS. My understanding is it bonds to ABS very poorly and tends to break off. West System G Flex epoxy is by far the best thing to use on ABS.


I suppose I could research and figure it out myself.

Does G Flex have a recommended thickener or is there a G Flex product that comes thickened like a duraglass poly product?

Yeah, my understanding is that the outer Royalex layer is ABS, and I know that ABS is notoriously difficult to adhere to. For model building people solvent bond it with MEK, but you’d need an ABS sheet to patch it with. Another product designed specifically for ABS is JB Weld PlasticWeld which I’ve not used.

You can thicken G Flex epoxy with colloidal silica powder which is sometimes reffered to as cab-o-sil. West Systems makes a wide variety of additives, thickening agents, fairing fillers, microfibers, etc. But silica powder is probably the best thing to use.

West Systems also sells a “Plastic Boat Repair Kit” with a 655-K designation. It has resin pre-thickened with silica powder. In your case that would probably be the most cost-effective option. You could shop around and see if you can come up with a better price:

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You can bond fabrics such as fiberglass and Dynel to the ABS of Royalex canoes with G Flex just fine. You don’t need to use ABS sheet. I have tried the ABS slurry method of repair in which shavings of ABS are dissolved in either acetone or MEK to produce a paste-like consistency to repair dings and defects in Royalex canoes and I have been thoroughly dissatisfied with the results, although I know some who swear by it.

The skid plates and keel strip on this old Mad River ME Royalex canoe are 5 ounce/square yard Dynel fabric that was bonded on with G Flex epoxy and they are holding up just fine years later:


Now if it came tinted to OT green I could patch a gouge and no one would ever know. :canoe: