End cap repair

-- Last Updated: Jul-19-13 3:39 PM EST --

Loaned my canoe out to friend and her paddling partner for a Quetico trip and when it came back the stern end cap was worn right through. I knew friend had shoulder problems (had rotator cuff and muscle repair a year ago but has another tear needing repair) and would have some difficulty with throwing a canoe. Didn't know her partner but was given the impression that he was strong and fine with proper throwing. Turned out that he also had a shoulder problem from having had rotator cuff repair previously. End result was lots of scraping of stern on rocks and erosion making surfaces during portaging. I don't want to leave the canoe that way so called place where we purchased it. Knew this canoe model hadn't been made in years but hoped I could find a replacement end cap. Owner told me he couldn't get a replacement and was not encouraging that I could find one that fit. Other models have wider end caps (shape of stern tip) so no luck using one from another model he said. He said I could try to repair it but offered me very little advice. I would like to try to repair it and thought fiberglass cloth and epoxy resin might work. Among all the stuff in the garage , I found several supplies I could try and wondered if anyone can offer some guidance. Two brands of epoxy: West Systems 105 expoxy resin with 305 hardener and two part Bondo from a fiberglass repair kit. Also two weights of glass: a light, much more drapable one and a thicker one. Darryl used the West Systems epoxy and the lighter glass to strength the blades on the canoe paddles he made. The heavier glass in the Bondo kit hasn't been used. So 1) opinions/experience of using epoxy glass for a repair and 2) would one be better to use than other? I was thinking it applying several layers would be needed (2 or 3 letting them dry in between). I've never done so would appreciate advice and words of caution from others who know about using this stuff.

Is the end cap still in one piece
and what is it made of? If the cap is sufficiently intact to serve as a framework to lay 'glass on and is made of fiberglass or ABS, West System epoxy should bond to it. If the end cap is made of something like polyethylene or polypropylene it probably won’t.

Assuming it is a non-olefin material and in more or less one piece, I would probably bond one layer of lightweight cloth to the undersurface of the cap with epoxy to cover the void. That will serve as a scaffold and backing plate to lay on additional epoxy and fiberglass.

I would have to see the defect to decide exactly what I would do, but a considerable defect can be filled in with epoxy thickened with some silica powder. You might need several applications and you might need to overfill the void a bit, then sand it down flush. If you use multiple applications of epoxy and allow each to cure before applying the next, wash the area of repair with soap and water and rinse well before applying more epoxy. This removes the amine blush which sometimes interferes with epoxy bonding.

Once the contour of the end cap is restored I would cover the whole thing with another layer of fiberglass on the upper surface to reinforce the repair. Again, I would have to see it to decide whether to use heavier (6 or 8 oz/yd cloth) or lighter (4 oz/yd) cloth.

When you are done, spray paint the whole end cap in some pleasing color. You could paint the other one to match.

find a way to show some photos here …

– Last Updated: Jul-19-13 11:21 PM EST –

....... same question , "what is the end cap made of" ??

If it's a fiberglass cloth and resin cap , I'd use vinylester resin .

FYI , in case you didn't know ... the common term fiberglass as most people think of it , is what they see when they look at a boat , a car body , etc. . The cloth is the fiberglass (or it may be some other cloth material ... the resin that saturates the cloth , is the resin and catalyst combo , which can be one of a variety of possible resins . Point is , what some may call fiberglass construction may not be fiberglass in any way ... but it all comes out basically the same in the end product , just minor physical property differences .

How old is your epoxy and catalyst ?? Personaly I wouldn't use any resin and catalyst (epoxy , vinyl-ester or poly-ester resins , nor catalyst) that's over a year old from mfg. date . The stuff has a short shelf life .

Probably "roven" cloth is what you should use to fill any missing void in the end cap , and laminate the thinner cloths under and over . But maybe it's not that extreme a repair ??

An all at the same time lay-up is your best bet if possible ... gives you a chemical bond with the layers instead of a weaker mechanical bond that happens when you wait for one layer to cure before adding the next .

Photos 1st , then many here can advise with confidence .

Also if a glass cloth cap , you can make a whole new one yourself almost as easy as a repair , sometimes easier .

And if it ain't a glass cap ... you can make it one anyway if you want to ... or wood , etc. .

Why vinylester resin? Harder to get,
doesn’t last in the container, doesn’t stick to anything as well as West epoxy.

I repeat, there is just NO reason to use any resin other than epoxy for boat repair.

West systems G-Flex…
will bond to most anything

Jack L

Vinylester resin usually has to be purchased in larger quantities and the catalyst is much more toxic. Epoxy bonds to boats made with vinylester resins just fine. I have used it for many boat repairs on vinylester boats.

I have used West System epoxy that is years old. The hardener sometimes becomes a little reddish in color, but thus far I have not had any failures to cure.

Since the OP has this at hand, I would certainly try mixing up a small batch.

G Flex will bond to polyethylene but only if the surface is carefully prepped, including oxidation by flaming with a propane torch. G Flex will not bond to polypropylene, and some other plastics. But again, the OP was asking about using materials at hand.

West System
I bought a gallon of west epoxy resin and a quantity of west system hardener (two actually, one fast one slow) approximately 20 years ago and I am still using it from time to time for boat repairs and the like and so far as I can tell it is still working perfectly. I have had seen no ill effects - except a little darker color. I would not use it to build a stripper but it is perfectly fine for repair work.

Dog Paddle Canoe Works
makes carbon fiber end caps for those not wishing to play with epoxy.

That was going to be my suggestion

Yeah, I love the aged stuff. It looks
good for repairs on mahogany furniture.

Or, he could wax the undamaged end
cap on the other end of the boat, and lay up a FG mold. Then he would wax the inside of the mold and lay up a new FG end cap. Color matching could be done by painting or by adding some West Graphite powder to the mix.

Actually, I like a crude repair. Strength over beauty. And it tends to make the boat more theft-resistant.


– Last Updated: Jul-20-13 6:58 PM EST –

Thanks for sharing your knowledge and experience with me. I took some photos so you can see the stern cap's condition on my SR Huron. I took a picture of its bow cap for comparison (although probably not needed). I suppose it's not terrible; it's shape is intact, just worn through. However, the Kevlar of the boat is exposed and vulnerable to damage. This is the first Kevlar boat we got and is still my boat of choice for Quetico tandem paddling. What's cap made of? I'd say with some certainty that cap is impregnated fiberglass (looks like it, frays like it). Definitely not plastic: I heated a wire to red then applied it to the cap. It didn't melt in--as it did when I applied it to cap on my Champlain(which looked and felt like plastic).


Relative to your comments of the age of the West Systems epoxy I have, yes it is >3 years old. I was planning to proof it before trying to use it if that's what I decide to do.

I'd like to keep my repair as uncomplicated as possible so would prefer to do repair with cap in place if possible. Maybe I could mold a small piece of heavy duty foil inside the eroded area (to cover the Kevlar),put a piece of glass over, epoxy, let dry & repeat glass and epoxy to build up. I figure the less I do, the less I can mess up.

Thats got some black in it too
Regular 5.7 ounce cloth though.

Can add graphite powder to get the black or black from simple .99 paint will work at well … Just a tiny bit.

That is pretty much what I imagined
I would probably take the cap off by drilling of the heads of the four rivets using a drill and a fairly large bit, but this would require you to have a hand-held pop rivet gun and buy a few aluminum rivets to reattach it. I would find it easier to repair with the cap off, but you can leave it on if you wish.

The cap is clearly made of some cloth fabric and your epoxy should work fine. I would first debride all the ends of the frayed fibers and bits of cap that are loose. You will then need to clean it up well using isopropyl or denatured alcohol and/or acetone.

I would cover the exposed stem of the hull below the cap as best possible with some clear plastic packing tape to avoid bonding the cap to the hull in case you ever did want to take it off. You can use your light weight cloth to cut several crescents of fabric to help fill in the void where the cap is eroded away. Try to cut these crescents so that the fibers of the cloth run at varying angles and the repair will be stronger. Lay a crescent of cloth in the hole and wet it out with a small batch of epoxy. You don’t need to wait until the epoxy is fully cured before putting on the next layer. In fact if the epoxy is still “green” you don’t have to wash it to remove the amine blush.

At summer temperatures you can probably lay in 3 or 4 layers of cloth into the hole in a day and completely fill it in. After the last layer I would completely fill the weave of the cloth with epoxy and let it fully cure, then wet sand the repair so that the cap is completely smooth and properly shaped.

I would then cut a piece of lightweight cloth the shape of the cap but a little bigger. Cut this piece “on the bias” so that the fiberglass fibers will be running at 45 degree angles to the long axis of the cap (and the boat) and it will lay down over the curvature of the cap better. Clean the cap well again and mask the hull below the cap to avoid getting epoxy on it. You can apply some epoxy to the top of the cap (a cheap acid brush works well) and then lay the cloth over the wet epoxy letting the edges hang below the bottom of the cap. Wet out the cloth thoroughly and when the epoxy is pretty much cured (but perhaps still slightly green) you can take a razor blade and slice off the excess fiberglass cloth.

After letting the epoxy on this last layer fully cure I would fill in the cloth weave with another application or two of epoxy, sand smooth if necessary, wash and spray paint the whole thing to protect the epoxy from UV exposure.

This is what I would do to get a pretty cosmetic and reasonably strong repair. If it sounds like too much work, you could fill in the void with Bondo, sand it smooth, and apply one layer of cloth over the top as described above.

A few additional points
Pblanc and several others have been spot on with their advice. I agree with using epoxy, especially if that’s what you already have on hand.

One point that has not been addressed is holding the fiberglass cloth tight to the contours of the existing cap (or a mold). Fiberglass does not willingly stay bent to tight radiuses until the resin has cured. Heavier weights of cloth are more prone to “flattening” than are lighter cloths. From the looks of the photos, I’d say the original cap was at least 8 oz. cloth. Maybe heavier. Cutting the cloth on a bias will help, but it still will likely try to spring away.

Placing the original cap or a male mold in a vacuum bag while the resin cures is the standard method of dealing with the problem and is what I generally do in such circumstances. An alternate method is to stretch plastic wrap over the assembly to hold it all together. Usually the wrap will peel off without much difficulty, once the resin cures. A downside to the plastic wrap technique is that the new cap will have a slick texture and not the cloth texture of the original.

My final point would be that from the appearance of the pictures, I’d repair and overlay the original caps as opposed to making new ones.

Marc Ornstein

Dogpaddle Canoe Works

another way …

– Last Updated: Jul-21-13 2:53 PM EST –

..... make an inside mold . I say do this as opposed to trying to use the boat itself as the mold (which would work but you might make a mess) .

Take the cap off , clean up the inside . Make a cardboard stop inside a ways back from the damaged area (a couple inches max.) and tape that in .

Either 6 mil poly or aluminum foil finger pressed to fit inside cap . Fill with plaster of paris . Remove plaster mold when hard , 20-30 mins. .

Remove cardboard . Light sand mold as needed to make reasonably smooth .

Cover mold with plastic or aluminum foil . Wet out cloth , wet out inside of repair area . Lay cloth into repair area . Put the mold back into cap to press cloth into place , Keep mold in place (clamp , etc.) , don't worry about cloth exceeding cap edges actually good to have cloth longer than needed , trim off later . You can acually trim cloth when resin starts to set up stiff or wait till cured . If I were definately putting a top layer of cloth over the cap ... I'd leave an inch or more hang out the bottom (squeeze out (w/fingers) excess resin from this part to almost nothing . When over lapping the top w/cloth , use that bottom hang out to hold top cloth with (cloths pins , pins , paper clamps/clips , anything , etc. . Trim bottom after all is done . Just squeeze out most extra resin in area to be trimed , fingers good enough (makes cut off easier) .

You can turn over while wet and patch/fill from outside . I'd just chop up shreds of cloth , add some silica filler , etc. to some mixed resin , and fill the outside , rough shape as it starts to set .

Or you can wait till inside cloth has cured . Then fill from outside .

I'd use vinylester resin and fiberglass cloth , and I'd use 3M vinylester premium filler as well ... but use epoxy if you want , just make sure you use epoxy (w/chopped cloth or silica) as filler from outside also if using epoxy .

If you ever use a carbon or arimid cloth , vinylester is not good for it , vinylester doesn't hold as well to exotic cloths , but works great w/fiberglass .

Although your SR is made of epoxy and arimid , I'd bet the caps are polyester or vinylester and fiberglass cloth . And expoxys like West or MAS that you can get are not the same thing as what your SR is made of ... they are specialized heat sheet epoxys formed in an oven .

When cured , sand to final shape as needed , add a 2oz. or 4 oz. cloth layer to top outside .

To make a whole new cap you can essentially do the same thing . Just make a mold to stretch your cloth over . In your case you could simply use the whole old cap and fill it with plaster of paris , concrete or such thing . If you didn't have a cap to work with you can easily shape a new cap mold out of dense styrofoam or wood and do a layup over it .

Have you tried talking with Souris River directly about replacement caps for your Huron , check your seriel # ?? ... 1-807-597-1292 , 1-888-226-6386