Will my epoxy repair last?

Need advice on the long-term viability of a field repair I executed on a 4 day solo kayaking trip. Boat is Current Designs Vision 120 composite Kevlar and fiberglass with gelcoat. Damage came from stern smacking down hard on an impossible-to-see submerged rock on a high-wind day in which big waves were tossing me up and down. As a big wave receded, my boat crashed down and the stern struck a submerged rock. Damage is about 4 inches long and ½ to ¾ inch wide, on the bottom of the hull and at the stern nearly at the end of the stern, where the rounded hull bottom turns into a more v-shape. The hull struck the rock right on that pointy v-shaped portion, and the gel coat cracked off clear down to the woven Kevlar and fiberglass along that v-shape, in a 4 inch by ¾ inch cracked-off chunk. With the boat in the water, this damaged portion is completely submerged at all times. It is not up on the rocker or above the waterline. It’s on the bottom of the hull, stern-side, where the hull becomes v-shaped.

I kept paddling after striking the rock, because I hadn’t thought the smack on the rock was a hard enough hit to do any serious damage, and I found the damage only after setting up camp for the night, about 4 more paddling hours after I hit the rock. From inside the hull, I inspected and confirmed that the layers of fiber material were not punctured through, and I saw no cracking and nothing looked amiss, aside from the fact that you could see the damage even from the inside of the hull if you positioned the boat so the setting sun was shining on the bottom of the hull. You could see pretty well through the fiber layers where the gel coat was busted off. It was possible to induce some flex in those layers of fiber if I pushed from the inside or from the outside on the area where the gelcoat has busted off.

Since I pretty much never go anywhere in life without a supply of PC-7 epoxy putty in my gear bag, I cleaned the damaged area and picked off any final loose chips of gelcoat and let the sun fully dry the surface. I didn’t have denatured alcohol or acetone or any other cleaner so I just used my backpacking microfiber towel to rub the area as clean as I could without having any solvent cleaner on hand. The variety of PC-7 was their Marine formula – the stick of dough with the hardener inside sort of like those Combos pretzel snacks with the cheesy filling inside. I carefully kneaded the PC-7 Marine dough to mix the hardener thoroughly, and I applied the PC-7 epoxy putty to the damaged area, and pushed it hard and firmly into contact with the underlying fiber layers. I smoothed it as much as I could and gave a good overlap around the perimeter of the broken gelcoat. This stuff has a 90 minute time to full cure, and this was evening, so by morning when it was time to put the boat back in the water, the PC-7 was cured up hard as a rock. I paddled another 50 miles over two more days and completed my trip with no more rock bashing, and the PC-7 repair looked as good when I finished the trip as when I first made the repair.

So, is the boat as good as new, aside from the ugly PC-7 epoxy putty blob hidden under the stern? Shall I just smooth it with a few grit sizes of wet sand paper to smooth it down, and be done with it? Or should I take it to my local kayak outfitter, which has a great boat repair shop, and have them remove my repair and replace it with whatever high tech stuff they want to use?

I don’t care about aesthetics. I don’t care if I have to spend a lot of money to fix it. I just want to know if it’s a reliable long-term repair as-is with the JB Weld, or if I should have a pro boat repair shop remove my repair and do a more high-tech repair. Advice and consultation, please.

That immediate keel area’s cloth is
generally pretty rigid. If you could push / dent the fibers, there is a good chance you cracked or delamed something … I would beef up the INSIDE with a few plys layed in nice and neat over the dry/prepped surface. If you are o.k. with the blob, leave it there for now 'till it wears down then fix the outside with possible glass and be ready with gelcoat to do a nice cosmetic finish.

how to check for delamination?
Thanks for the answer. You mention I might have cracked or delaminated the area since I could flex the fabric where the gelcoat busted out. If so, is building it up on the inside sufficient in itself, or should I cut out the cloth inside the perimeter of the busted out gelcoat? My intuition tells me it’s better not to cut anything out, but instead just to build up inside as you suggested. However, if doing it the right way means doing it the more difficult way, I am willing to take the difficult approach. I want to do it right. I’m thinking of a strip of KeelEazy over the repaired area, too, to protect it against the next time you hear that horrible bash sound and feel crash in slow motion!

Thats what the inside beefing up will
do …

For sure the “right” way to do it is get all that junk off there but its on now and laying the glass inside will have a beneficial side effect next time you hit.

With the glob on there now, you may not see it as well as before but the quickest way to check for damage was the look through. A bright flashlight held by an assistant can reveal some stuff too. Before the glob and even now to a but lesser degree ( again because of the blob ), you will be able to determine damage by simply tapping on the surroundng area with the tip of your key. It should all sound the same. Lower frequency = probable damage.

Get the kayak inverted on saw horses,
out in the sun, and peer into the inside of the stern to see if the cloth is cracked or damaged. In a way, it’s too bad that PC-7 is there, because it may obscure the view. You could take it off before inspection. Split cloth will be more obvious, but delamination would show as clouded or mottled patterns.

If repair is needed, it may be difficult to do inside. Your damage is similar to what occurs on composite ww kayaks and canoes when they wham down on a ledge in a river. I had an old c-1 that kept cracking down the center of the stern on ledges, and I would then put a 3 layer concentric patch on the outside. They all cracked. Finally I made up a 3 layer concentric patch for the inside, using Nylon. I basted it together with a single “cross” of thread. I cleaned and sanded the inside using Ethafoam on a broom handle to hold the sandpaper. I switched to a bent nail on the end of the broom handle. I wet out all three patches (basted together) with epoxy, and using the handle and nail, dropped the patch over the inside of the stern split. I didn’t have any more splits.

But if you do a good 3 layer glass patch on the outside, you may not need an inside patch. Getting whammed on a rock like that will not be a frequent occurence for a sea kayaker, unless you’re in the Tsunami Rangers.

keeleazy good idea?
OK. Thanks for all the good info. I will do an inside-the-hull glass repair. How much wider than the missing chunk of gel coat should the largest patch be? And I assume the smallest patch should be at least slightly wider than the missing chunk, right? When done with this inside repair, I intend to smooth down the PC-7 blob so it is flush with the rest of the hull, and then apply a strip of Keeleazy, which I just read about today on this message board. Good idea? I didn’t specify that this happened on the mighty mile-wide, always shallow Susquehanna River, where i do the bulk of my paddling. Rocks, rocks, and more rocks everywhere. I know, I know, a plastic boat might be the better choice. I have one. But I hate portaging it.

don’t go by the missing chunk
The chipped gel coat isn’t structural so it’s not the indicator for damage in the laminate. It’s damage to the hull you’re concerned about. The missing gel coat can distract you to thinking that is where the damage is when it may be a crack extending beyond the missing gel coat. If there’s a crack/soft spot extending up beyond the gel coat that’s where you want glass to extend about an inch beyond.

If the repair is in an awkward position gd2 suggestion of minicell on the end of a stick then wrapped with sandpaper is a good one.

I just did a repair on a Gulfstream in a similar position where the kevlar on the inside showed a crack extending up about an inch beyond the chipped gelcoat, on the exterior I had to grind down an area of cracked gel coat about 6"x2" and build up a replacement for a section of heavy roving that had popped away from the underlying kevlar.

It can get very messy attempting to glass beyond ones reach but I was very pleased with the results using the following materials:

  1. First the interior repair was done with two 3" strips of 9oz tape one layed 1/2"-3/4" over the other in a slight “v”
  2. Getting glass into position was done by making a temporary backing plate of thin plastic garbage bag material (the very cheap kind that comes in a roll) that was about 5"x9" made up of multiple laters. The reason for that is the wet tape can shift around with the first layer and not get bunched up. On the back of the plastic I put a couple layers of 2" blue tape so it would be stiff enough to put into position without folding in half but not so stiff I couldn’t press it down.
  3. After cleaning/drying/sanding the area I pinched the glass tape holder at one end and put it into position after measuring how far my reach had to get it, doing this all blind requires some idea where the patch can be placed. Looking inside I could see if it needed a little adjustment then with the stick with minicell I pushed down gently into the keel and sides. Next day the backing peeled off leaving a nearly invisible patch without bubbles.

    I had to repair the outside because the keel had a strip of 24oz roving that was about 2" wide but it popped completely off the underlying kevlar laminate so I had to grind down it then reglass with multiple layers to replace the popped piece and cover the cracks that extended up the side a bit.

    It’s kind of funny how much effort goes into making these boats light with disparate materials, I think I’d rather have a bunch of solid layers of glass cloth.

…my guesstimate is , it will probably flake off or separate from the hull( at least microscopically) in the future…I seriously doubt, given the timeline, that the damaged area was 100% dry b4 the repair was made,ie: the hull fibers were thoroughly soaked and only surface dried. therefore , i’m sure there’s still plenty of moisture in there. I vote to repair it more thoroughly. U can use those canoe kevlar skid plate kits to repair it and repaint that repair. the fact that U are not to concerned about the looks is a plus. Structurally sound seems to be your concern.

Yep on that Lee … Roving + Kevlar
is a wasted effort. One will be ‘gone’ long before the other as you saw.

why do they do that?
It’s weird, we’ve got an old Tofino that doesn’t have any cracks in the hull, it’s nearly solid kevlar and it holds up fine after being dropped/bashed. But it’s obvious the strip of roving had no desire to remain attached to the underlieng glass/kevlar. It was a big drop from the top of a SUV to the ground. Maybe they should make the kayaks out of tuff-weave. As long as I’m on a roll I’m not too convinced that one huge piece of core material is the way to go, it’s pretty standard with all these Chinese boats and it does seem to be as durable as a solid roving boat or as forgiving as the older kevlar boats. I don’t think there’s enough glass on either side.

Theres more to it
I recommend epoxy from west systems and not something that has been on the shelf at Home Depot for 4 1/2 years. Epoxy will generally bond to anything, unlike polyester resin.

There are different kinds of cloth- biaxial and triaxial which can be used to give the damaged area extra strength–it depends on the forces exerted on the area in question.

Mix the resin and the hardener very accurately, and pay attention to the ambient temperature so that it cures properly. You can get special resin/harderner for curing in cooler temps.

I can’t say that I have repaird a fiberglass kayak, but I did replace two fiberglassed-in engine stringers underneath a 330HP marine engine.

Paying attention to the details pays off big time.