C-Forum

After trying PC-7 epoxy to repair cracks on the inside of my Outrage, I went back to 3M urethane adhesive. The PC-7 was much too brittle for unsupported repair in the flexible part of a Royalex hull, and re-cracked right away.

Original discussion here:
http://cboats.net/cforum/viewtopic.php? ... hlight=pc7

Recently, I've also cracked some 3M adhesive. So it's not perfect either. (And I think I'll go back to adding some fiberglassing over the repairs, as it appears my Outrage is prone to cracking.)

3M is expensive, and it cracked, so I'm looking for alternatives. I'm thinking Goop won't be enough? I was going to go for JB Weld, either the 2-part tubes or the roll, but the hardware guy recommended a PC marine epoxy. But I wonder if all "epoxies" will be too stiff?

Any experience with PC marine epoxy (roll) or PC-11 epoxy (2-part)?

Is JB Weld more flexible than these epoxies or 3M adhesive?

Is Goop really an option for a cracking hull?

Thanks, Pat.

p.s. Similar thread on some products here:
http://cboats.net/cforum/viewtopic.php? ... hlight=pc7

yarnellboat wrote: 1-Is JB Weld more flexible than these epoxies or 3M adhesive?

2-Is Goop really an option for a cracked hull?

In my experience with these:
1-JB weld is more rigid than 3M in my opinion

2-I think Goop would be OK as a temporary solution with some structure,ie.glass mat,ABS,etc.

is the cracking vertical or horizontal to the water line?

The key is to keep the patch flexible or a new crack will appear along the edge of the patch. I just got hold of some scrap raft material which I plan on using for patching cracks. I've been using it for making tie downs, etc. and I figure that it would be perfect for patching cracks because it's very strong and very flexible. I've never seen any cracks develop along the edges of the tie downs that I've made. I just use Vynabond for gluing them down.

I have been using Kevlar cloth (don't use Kevlar mat) with West System epoxy for large patches. Cracks will sometime appear along the edges after awhile but you can cut down on the new cracks by sanding down the edges of the Kevlar patch real well. This will keep the edges of the patch soft and flexible.

I've never tried Goop. Let us know if it works.

I've worn out three Outrages so far due to running steep creeks and I'm on my fourth. I've found that I get much less damage around my saddle if I keep the saddle free floating. This leads to the possibility of the boat being turned inside out in case of a pin so I glue a sheet of 3" thick Minicell in back of my saddle and have it stop 2" below the thwart. This allows the bottom of the boat to flex 2" and still help prevent the boat from being turned inside out.

I agree on the "floating" saddle, but I've always thought of this in terms of wear & tear on the outside of the hull beneath the saddle.

My cracks go every which way. Initailly there was one along side a thigh-strap d-ring. Now I've had about 6 cracks in front of my saddle and near my knees. Parallel, perpendicular, L-shaped, and diagonal.

The most recent crack, in the 3M, is a new one, not a re-opened one and not along side the seam of a repair, but I did whack it pretty good.

I think whatever I use will be fine if I fiberglass it too, which apparently it's time to do. But I may not use the PC-11 epoxy if it might be too stiff/brittle.

I agree on the "floating" saddle, but I've always thought of this in terms of wear & tear on the outside of the hull beneath the saddle.

First of all, you live up north in the cold country. Once, while paddling while snowing, a kayak (a Mongoose) went through the side of my Whitesell causing a huge hole and coming to rest against my saddle. Royalex does get a bit brittle in the cold so it does tend to crack easier. I fixed the hole with two sheets of Kevlar.

As far as the cracks in front of the saddle and knees go that is caused when the boat rides up over a rock. The boat flexes as it rides over the rock until it hits something hard like your knee or saddle. This causes a lot of stress, especially in cold weather.

With as much damage as you describe I suggest that you remove your saddle and knee pads then cover the floor with a large sheet of Kevlar. I would put a couple more layers under the front edges of your saddle an knee pads.

For inside cracks the best solution I found was pretty simple - First take a 12-16 penny nail and de stress the end of the crack by drilling a small hole through the top layer of vinyl. Then apply a vinyl patch. You can often find sheet vinyl in old fashoned hardware stores or if you have a plastics shop in your area. For inside patches I use the thinnest I can find. Vynabond the patch into place like you would a dring. I have also found the grey sheets they use for shower pan liners (to waterproof before they lay tile) to work quite well although it is a bit thicker than you need inside - it is good for worn chines or bow and stern wear areas. The grey PVC can be found at your building supply places and even Home Depot.

Doing this I have never had a crack continue. Glass on the inside of the boat will fracure easily due to the stress of stretching as the boat flexes inward. Kevlar may be better but good old vinyl does the trick.

kevlar patches work the best. I seem to have had better luck avoiding recracking.

One important truth to accept here is that we break our boats and when we fix them there is a strong likelihood that they will break again, often in the same place. We tend to break them in the same places because those are the places where the rubber meets the road. My "fixes" are generally temporary extensions on the life of a canoe that I have abused beyond what is reasonable.


I had never thought in terms of the free floating saddle as way to decrease damage. Thanks for the great idea.

Chris Kelly

Thanks all. I've been distracted from the Outrage by outfitting the Score, and blowing out its rim a bit.

I think I'll have to go with Kevlar patches and epoxy in the high-impact zone (in front of the saddle), where I've experienced re-cracking. I'll try the PC-11 marine epoxy to fill the cleaned-out cracks.

With some of the further-out new cracks, I may try plain Goop in one and PC-11 on the other, just for experimentation. If I have an extra crack, or if these re-crack (I can't see Goop alone doing much, although some have recommended it; and I can imagine PC-11 being to stiff alone), I'll also try a vinyl patch, but I can't see that adding much protection; then again, it seems to have worked for Jim P., so I'll try it.

Jim, a friend did a big vinyl patch on the outside of his worn bottom & chines (old Viper 11), and the vinyl patch is a nighmare in terms of how sticky it is on rocks.

I may as well try a variety of things now before it really becomes time to rip everything out and re-do the whole bottom. I'll also start saving for a new OC-1.

Cheers, P.

Lots of good advice already. The secret to a good patch is to avoid lines where stiffness changes abruptly. Kevlar and epoxy are good materials for inside patches, but you need to lay the biggest patch down first, then a smaller one, then smaller still, until the smallest one just covers the crack by maybe an inch all around. Having the most layers in the middle helps keep the hull from bending enough there to re-crack.

I also like Jim P 's advice about vinyl patches. It used to be common to use heat molded Kydex (a vinyl) for grunch pads on the outside of the boat, and they held up quite well.

I've owned and paddled a MR Synergy since about 1997, and haven't seen any inside cracks. Must be doing too much ezwater.

As Jim M. pointed out, it was cold out and on an ice-cold river (as always in BC). It was also during a low-water run, and I am a heavy guy - so there were some major impacts/stresses. On the other hand, I only paddle class II-III, and maybe 40 days/year, so it gets fairly gentle treatment, relatively speaking.

I'm not a total rookie at boat repair, but I haven't had experience with cracks and re-cracks like these. I bought the boat used and cheap 2 years ago, in good condition but with 1 crack (at plastic-base d-ring in front of saddle). It was a rental and may have been stored in the sun for 10 years.

I too have certainly seen many old, well-used boats not develop this cracking. I don't know whether it's been the storage, the batch of Royalex, the cold rivers, the paddling/paddler, the outfitting, the age or what, but this hull has become pretty crackable.

But I'm sure I can get a few more seasons out of it if I try!

P.

Intersting about the sticky patch. You sure he didn't use Aluminum?

Never even thought aout it till I saw your post. I just figured vinyl is vinyl, its the outer layer on ABS, so why not rebuild it with the same material? I guess different manufacturers may do slightly diff formulas resulting in softer and sticker sheets?

Next I'll test my Ocoee out by sticking the orginal chine on a rock, reattain, to go back and stick the other chine on the same rock again. Of course the first impact should slide easier than the second if the algae on the rock wears off so as might have to repeat the test on many different rocks, trying left chine 1st then right chine 1st. Dam I might need new patches b4 the test ends!

Give this a try.. head over to a plastics store and pic up some kydex 1/8th inch plastic. Cut it to a football shape to cover the crack.. it can be heat formed if need be with a heat gun available at most hardware stores. sand an apply 3m structural adhesive to both sides and glue it into place. the kydex is flexable and stronger than abs. if your really into it, feather the edges of the plastic on a beltsander ( or similar device) . Ive found this workes really well. ... Cheers...