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 Post subject: Repairing royalex canoe
PostPosted: May 11th, 2022, 6:00 pm 

Joined: June 13th, 2020, 9:25 am
Posts: 5
I got an old Royalex canoe that has a lot of white showing and one soft spot in particular. I was wondering what’s the best practice for fixing this? I’ve seen a lot of YouTube videos for patching of Kevlar and fibreglass canoes but nothing for royalex anymore.

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PostPosted: May 11th, 2022, 6:50 pm 
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Joined: June 20th, 2001, 7:00 pm
Posts: 3789
Location: Toronto, Ontario Canada
I might not do anything!

The green vinyl layer is only there for UV protection, it is in no way structural.

I don't even see any cracks which would be something to repair. Perhaps there are microcracks I can't see in the pic.

Want to see a Royalex boat with a lot less vinyl remaining.........


I do have a number of cracks (mostly short), I will be filling them with West System gflex and then cover with either s-glass or preferably dynel (dynel is just about impossible to obtain in Canada).

If looks matter to you any kind of vinyl paint (somebody else can recommend a particular brand) will protect the hull from UV but that's really only of importance if you store outside.

As far as "soft" in that location it could just be normal flex, if there are actual cracks in the plastic there could be some deterioration of the foam core so in that case patching would be a good idea but isn't something to be overly concerned about.

Maybe post a close up pic of the area.

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"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915

PostPosted: May 12th, 2022, 7:11 am 

Joined: June 28th, 2001, 7:00 pm
Posts: 2224
Location: Freeland, Maryland USA
The wear, for now, appears to be mostly through the vinyl skin on the Royalex sandwich. Royalex is a five layer ||||| sandwich; the outer layers are vinyl covering a layer of ABS (hard acrylonitrile butadiene styrene plastic), with a layer of foam as the core. The vinyl skin serves largely as a UV barrier, and you can see how the kevlar felt skid plates prevented wear on the vinyl layer beneath.

The ABS layer beneath the vinyl skin can be of varying thickness depending on where on the hull, usually thickest at the stems, and on how the manufacturer speced the Royalex sheets that used in that particular model canoe. “Lightweight” Royalex canoes used fairly thin ABS to help keep the pounds off.

Some UV protection for the exposed ABS layer is a good idea, especially if the canoe is stored outside. A coat or enamel paint will provide a UV barrier, until it too scrapes off, and it will.

A longer lasting repair would be to install cloth of some sort with epoxy, and that gets into the weeds of material availability and technique. My preference would be to install a layer of Dynel fabric, compressed under release treated peel ply. Without the peel ply compression Dynel fabric will swell like an old sweatshirt when epoxy saturated, and the Dynel surface will set up wood rasp rough.

The benefit of Dynel is that it is at least 5 times as abrasion resistant as S-glass or E-glass. I did a bunch of impact and abrasion testing with glass and Dynel but another experimenter’s test better summed up the results:

Scraping at the epoxied fabrics with 6 pound fire brick held on a 45 degree angle
The test with 6oz fiberglass cloth took 52 strokes to cut through to the wood
The 5.5oz Dynel has more than 250 strokes and is still not through to the wood.

But, as Recped notes
recped wrote:
(dynel is just about impossible to obtain in Canada).

The next best alternative would be to epoxy two layers of S-glass cloth, with one layer laid on the bias, with the weave XXXX and the other with the weave laid ####.

This link is more about installing skid plates using Dynel fabric or narrow Dynel sleeve, but the application and technique are much the same for covering larger areas or using fiberglass cloth.

Depending on the frequency of rocky river use you can fix it now, fit it soon or fix it later, but it is easier to repair before the wear gets into the foam core.

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