Repairing Cracked Royalex Canoe???


I recently acquired a royalex whitewater canoe that needs some repair. It took a good impact at the bow and has a crack in the Royalex that runs lengthwise for a couple of feet on the bottom of the canoe. It has caused part of the outer layer of the Royalex to chip off at the point of impact as well.

I took it to a boat shop to repair and they don’t want to do it because they feel it would take a lot of work and then there would be no guarantee it would hold b/c they think that the repair could flex and therefore break.

I still want to try to fix the boat. It’s worth a try.

What do you recommend? I am looking for a good fix and not necessarily something that is going to look pretty.



Ohters here far more knowledgable
than I am. I will read their ideas with interest. I have made some rough home owner type repairs to old royalex boats to keep them going over the years. I used fiberglass cloth, not mat, and epoxy resin (west system). I used two layers of cloth. Worked fine. It does add weight. Not pretty.

g-flex epoxy resin

– Last Updated: Jan-27-12 6:04 AM EST –

and g2d will add more info on the glass to be used. I patched a hole in the bow of my Encore (seal launch into a rock, DUH) with the g-flex and 2 layers 6 oz. glass, and it's held up great.

Seeing as your repair is on the bottom, I'm guessing g2d will recommend another type of glass, perhaps s-glass.

So far using g-flex, I have patched a kevlar canoe, a royalex canoe, a truck mirror (metal to glass), a truck rack, metal/metal using glass). Great stuff, flexibility is what makes it great for royalex. Don't use too much, I've got drip marks running down my hull (oh my) as this stuff wets-out for hours it seems.


– Last Updated: Jan-27-12 7:31 AM EST –

I would use G-Flex epoxy in preference to the more usual 2 part epoxies such as WEST 105/205 etc. The usual epoxies can bond well to Royalex but the greater flexibility of G-Flex will better match the flexibility of the Royalex and make it less likely for the repair to separate over time. And I would use 2 to 3 layers of 6oz/yd E-'glass. S-'glass is fine if you have it, but more expensive and a bit trickier to work with. Try to have the fibers on at least one of the 'glass layers oriented on bias for more strength.

Before you lay on your first layer of 'glass, fill in the crack with unthickened G-Flex. Turn the boat upside down with the crack skyward and fill in the crack. Warming the G-Flex a little with a heat gun or hair drier will make it less viscous and better able to fill in the crack. You may need to do this a couple of times to completely fill in the crack but the G-Flex can be mixed up by eye in very small batches, so you will have little or no wastage.

Any void left by missing pieces of the outer solid stratum of Royalex need to be built up flush with the surrounding hull surface with G-Flex and you might want to thicken the epoxy with colloidal silica powder for this purpose. The G-Flex is easily shaped and sanded when fully cured. Again, it may take several iterations before the hull is fully filled and faired.

If the crack runs along the keel line of the boat, or close to it, and is reasonably near the stem, you can cut your glass in a tear drop shape and apply it as a skid plate. Three layers of 6oz glass will make an admirable abrasion plate for future misadventures. As you use the G-Flex, keep coming back to it periodically to rework it until fully cured. This may take over an hour depending on ambient temperature. You can keep reshaping any sags or runs right up to the time it cures.

Once you are done, spray your repair with Krylon Fusion spray paint to protect the epoxy from UV.

Pretty much what I did
Repaired my old Royalex WW canoe. The old kevlar skid plate was cracking and falling off in small sections. This was the stern which, over much time, took some pounding on drops over rocky rapids.

This happened to another of my canoes and it struck me that the epoxy I used for the kevlar skid plates didn’t have the flex to bend with the hull and so over time the plates cracked.

So last summer I used G-Flex. Stipped the kevlar off using a chisel and found I had a long crack along the keel, exposing the foam core. The royalex was delaminating from the core. So I cleaned up the crack, cut away the Royalex to the point of delamination. Used G-flex mixed with silica to create a peanut butter consistency and then filled the crack and into the edges of delamination. Tapered and smoothed it all out.

To create a new skid plate I used Dynel cloth. Used 2 pieces. One small one to cover the crack with about 2 inches extra on each side. G-Flex used for that. Then a 2nd Dynel piece larger than the first - also with G-Flex.

Others seem to like FG - I don’t have much experience with that and didn’t want to sand and feather everything out. I wanted simple and didn’t care much what the bottom of an old Royalex WW canoe looked like. That said it still looks pretty good as I mixed some green pigment into the G-Flex when applying the Dynel skid plates and it matches the rest of the hull pretty nicely.

Canoe repair held up wonderfully on a 2 week trip of Class II-III water later that summer

I use Dynel cloth for abrasion plates on Royalex canoes. It is said to have less structural strength than fiberglass, but is more abrasion resistant.

Dynel frays along the cut edge but has less tendency to do so than fiberglass does. Dynel soaks up quite a bit more epoxy than fiberglass, but that is not undesirable for a skid plate.

If I were repairing this canoe, I would fill in the crack with unthickened G-Flex, fill and fair the hull with G-Flex thickened with colloidal silica, cover the repair with at least one layer of 6oz/yd fiberglass cut on the bias, and cover that with a Dynel abrasion plate, mixing graphite powder into the G-Flex to give it a nice black appearance and make it opaque to UV.

But that is because I already have all the materials on hand.

Remember the Chipewan?
Besides both stems being cracked, I put these cracks in it when I tried to melt the oil-can out of the bottom:

Repaired it with epoxy filler and a couple layers of glass on the inside of the boat. On the outside, I covered the whole bottom with a layer of dynel, so there was basically a fabric “bread” layer sandwiching the hull. I used the boat at least 50 days before passing it on, and the repair never hinted at failing. I recommend two layers of glass inside and out.

I’m not overly impressed by dynel. I’d use fiberglass cloth. FG is much easier to shape over compound curves. True, the unraveling of the cloth is inconvenient and annoying, but there are ways to deal with it.

Or, you might want to write DougD about applying a layer of sheet aluminum, attached with liquid nails and wallboard screws.

When I did the Chipewan, West System had not yet introduced G-flex, so I was using regular West System. I’d be more confident with g-flex.

Good luck with it ~~Chip

What is the diference between
gflex and west system resin? I’ve used West system with great success for this sort of thing. My repairs have lasted more than 15 years with lots of abuse. But I all ears.

G/flex is West System.

Followed the link to west
but I can’t find anything there that explains how the stuff differs from West System resin. ??? Maybe I’m missing it?

I’m confused now.
It must be me.

I did find
one youtube that said it is different because it bonds to typically hard to bond materials like thermoplastics. Nothing about royalex. Nothing about being more flexible. I have had excellent results with west system epoxy and royalex repair and so I would be reluctant to switch for a royalex repair - unless someone has more to offer on this –

G-Flex vs 105/205
G-Flex was formulated by WEST Systems to provide better bonds to plastics than their standard 105 resin and 205,206,207 hardener combo. It has advantages and disadvantages in comparison.

It is more expensive but it can be mixed 1:1 by volume, and the mix ratio is not nearly as critical as with 105/205. This allows very small batches to be mixed by eye without the need for metering pumps. It reliably bonds to polyethylene, which 105/205 does not. It has a lower modulus of elasticity, which means it is more flexible when cured. This may allow a more reliable long-term bond to flexible substrates that are subjected to repeated stress.

It is more viscous than 105/205 so it takes a little longer to wet out cloth, but it seems to have a longer pot life. It does not cure as clear as 105/205 though. When mixed it somewhat resembles honey in consistency and has that color when cured.

I have seen durable repairs to Royalex done with 105/205 as well. But I have seen others that separated from the hull over time.

old school royalex repair
Hi Matt

In the late 70’s I broke all four ash gunnel strips and tore both sides of my Mad River Explorer down to the bottom in a pin. It was repaired by a guy at U. Mass Maintenance Dept. He used ABS rod and an industrial heat gun. I subsequently repaired a few “cold cracks” the same way. Those repairs held up for another 15 years before the canoe died from sun exposure (my brother stored it in the sunlight year around).

While I could explain how to do such a repair, today I would use G-Flex as it’s easier and would look better.


I would use 105/205 rather than G-flex
because several concentric layers of cloth will be needed, and G-flex doesn’t wet out cloth as easily as 105/205. With suitable preparation, 105/205 will stick quite well and will bind the cloth layers very effectively. I suspect that the hardness and rigidity of 105/205 may be more compatible with the stiffness of glass cloth than G-flex.

G-flex can, of course, assist in initial bonding of the crack.

Glass cloth should be bias cut so that double the # of fibers cross the break. The glass must go on largest piece first, and so on down to the smallest. The fiber orientation should be varied a bit from one layer to the next.

Cloth layers largest first?
Do I understand this correctly? So when repairing a crack you would lay the largest piece of cloth, wet it out, then lay a smaller piece and wet it out, etc?

Correction to my post above
These questions had me go out in the yard and look at my canoe patchwork. I was mistaken in the order which I laid out my Dynel. Large piece first and then a second smaller piece over the area that takes the most abuse.

I don’t patch up boats often and when I do get advice from others with more experience. The general wisdom I received was large first patch, small patch second.

Patching fabrics to select - seemed to be a lot of differing opinions on what to use - and perhaps that is due the nature of the boat you’re repairing and the conditions the boat is subjected to out on the water.

I don’t think it matters
If you are using multiple layers of cloth, they should be concentric in size to avoid a big stress riser at the edge of multiple cloth layers.

I have done repairs in which the layers became progressively smaller and others in which they became progressively larger and not seen any difference in durability. Furthermore, I have seen some instructional videos of fiberglass repairs done by professionals in which the layers became progressively larger.

The bit about using progressively smaller layers probably originated with Charlie Walbridge in his book

“Boatbuilder’s Manual” but I have read that book multiple times and I don’t recall Charlie making any logical case for why it would be better to have the layers get progressively smaller as opposed to larger. If you like to do repairs in which multiple concentric layers are all wetted out and applied together then having the largest layer deepest allows the edges of the cloth layers to be feathered after the resin cures.

I prefer to apply cloth layers one at a time and feather the edge of each before applying the next.

Walbridge said it matters. West says
it matters. And if you have the patience to think through what happens when patching material bridges the interrupted layers of a hull, you’ll see it matters. The largest patch going down first will bridge and bond together every exposed layer of the laminate under repair.

For most purposes it may seem not to make a difference, but everywhere that a larger patch bridges over the edge of a smaller patch, there is a stress riser. When a smaller patch goes over a larger patch, the stress riser can be quickly alleviated by tapering the edge of the smaller patch.

I can accept people saying that it “doesn’t matter much” but not that it is easier to go smaller to larger. It isn’t. Over convex surfaces like the stems, it is distinctly easier to go larger to smaller, and it better accomodates the necessity of using bias cut for the largest patches.