Recommendations for deep gel coat damage on kevlar kayak

vettpaddler · October 10, 2020, 6:13pm

I’ve seen a number of videos on gel coat repair of cracks, but this damage seems a bit more involved. (I’m not sure how it happened.)

This is an older kevlar Sea Star kayak and still has a beautifully finished pearl deck. I’d like to try a DIY repair of this damage, but I’m worried about getting the color correctly matched and the strength of the final repair. The longest part of the hole is about 6/10th of an inch.

Any recommendations on products to start with? Or some pointers to some videos that are more relevant?

Thanks!

PaddleDog52 · October 10, 2020, 6:25pm

Sand edges to feather 1:12 apply gecoat. Is kevlar weak if you press there? May have to reinforce on the inside if it was caused by impact.

grayhawk · October 10, 2020, 6:27pm

Just use some white Marine-Tex…
If it doesn’t quite match rub a little dirt on it… Done…

rstevens15 · October 10, 2020, 6:51pm

I’ll leave others to give advice on the repair other than to suggest that you sand down the edges so that it forms a bevel down to where the epoxy layer is firmly bonded to the Kevlar fabric to uncover any hidden damage. It’s painful to do as it enlarges the area to repair. Avoid damaging the fabric itself. Check for damage inside the boat.

A final coat of gel coat can be used to color match, but color matching is an art and not easy. Only a brand new boat might be perfectly white. As it’s on the bottom of the hull, it might help to repeat to yourself, “It’s just a boat, not a fine piece of furniture or artwork”.

vettpaddler · October 10, 2020, 7:35pm

The kevlar weave is undamaged and pressing on it has no give, it seems as hard as the gel coat itself. This spot itself is actually a few inches below the left center rim of the cockpit.

I’ve never worked with Gel coat before, but I have worked with epoxy. I like the sound of the marine-tex solution with the exception of the white spot it leaves. Would it be possible to put a layer of colored gel coat over this later on top of the epoxy? Or maybe add some pigmenting to the epoxy itself to get a closer color match?

Thanks for the great suggestions.

grayhawk · October 10, 2020, 7:44pm

Marine Tex is epoxy and you can add a dash of pigment to the white before the mix.

rstevens15 · October 10, 2020, 9:57pm

Only the White Marine-Tex can be pigmented. No pure color will be achieved by adding pigments according to the manufacturer. (Marine-Tex also recommends epoxy-friendly pigments like Evercoat’s for gel coat and epoxies.) Do not use more than 5% pigment per total volume of epoxy.

It might be easier to apply color matched gel coat over the Marine-Tex after it is sanded down as Marine-Tex is a two part putty-like compound.

TomL · October 10, 2020, 11:45pm

That’s an easy fix. It looks like it took a hit and a piece of gelcoat popped out. Tape around the hole. Fill the hole with gelcoat (my preference) or epoxy. Sand the surface smooth. Paint with Krylon or any other paint…pick a white that seems close to the color of the hull. Remove tape and go paddling.

vettpaddler · October 11, 2020, 12:37am

I’ve ordered some white marine-tex and will give it a shot. I have a few small gouges on the bottom that I’ll try to get some experience with before attempting this side repair. The Krylon idea sounds like it might work and it comes it a closely matched color.

It will be a few weeks, but I’ll post an image of the fix when complete. I’ve never had responses to questions as fast as here. Wow, thanks everyone.

LaShin · October 11, 2020, 7:57pm

I bought a beat up carbon fiber boat and plan to fix the gel coat once it cools down here in Florida. I’m sure the folks here will correct me, but from my research, you cannot gelcoat over epoxy. Keep watching the videos. Some are crap and some are excellent, but the excellent ones are not the first ones to come up. This is the second one. You might want to look for the first one. https://youtu.be/en-8SbhdF_k

There is also one video where the guy is patching a canoe . A red Canoe. And he uses the gel coat and does the sanding, but instead of all the long and tedious multiple grades of sanding, he just sprays it with a red I think it’s an oil-based high gloss paint. Looks great. I would think a couple more coats of a clear coat UV protectant would also be a good idea. To me, pushing a spray button on a spray can is a whole lot easier than sanding and sanding and sanding and sanding and sanding. I probably got it bookmarked somewhere but I can’t find it right off the top.

roym · October 11, 2020, 8:36pm

white is the easiest color to match, just buy white tinted gel coat. No paint.
lightly sand clean with acetone or even rubbing alcohol. Actuate the a small amount of gel the same as you would polyester resin. Fill in the spot , a little proud. {so you can sand some to get level} spray or brush on a bit of PVA to seal the gel so it will cure {If you didn’t buy waxed gel}. Let sit and cure overnight.

Sand with wet and dry ,{on a small block} start at 400 work to 1000 or 1500. Buff if you wish, 2000 grit. Smile and go paddling.

roym · October 11, 2020, 8:40pm

You can also cover with some Mylar or slightly thicker plastic film to seal the air out and smooth the surface, so it will cure.

sometimes this allows a no sand finish …seal the edges of the film so no air is in.

TomL · October 12, 2020, 3:22pm

I’ve used the method that Roy is recommending too. I used clear gelcoat and Glad wrap. That’s why I say it’s an easy fix…you basically just need to fill the hole with gelcoat or epoxy. Hardest part for you may be just supporting the boat on its side so your hole is on top to help the epoxy or gelcoat fill it evenly. You may find it easier to fill it most of the way with one application and then finish it with a small second application. As far as deep gouges on the bottom you can probably ignore them unless they have exposed the fabric…it looks like your boat has a nice thick gelcoat.

rstevens15 · October 12, 2020, 7:41pm

The only trouble is that except for a brand new boat, the bright white of white gel coat is probably not going to match the hull. Even brand new white hulls often vary slightly. I took a fiberglass workshop years ago and one of the experts teaching the class color matched my “white” hull. It’s an art the often can take years of experience and excellent color vision to be really good at.

I’m kind of curious about the damage to your boat. It almost seems like the epoxy or gel coat never adhered to the Kevlar fabric in this area. Maybe this was a manufacturing defect where they got some grease or other contaminant on the Kevlar. I’ve seen Kevlar boats bent at a 90° angle. There will be multiple cracks but the gel coat usually doesn’t break off like this. Often, if the boat is straightened out, you have to look closely to see the damage, although the boat is totaled.

I’d check carefully to make sure that there isn’t more delamination extending beyond what you can see.

CraigF · October 12, 2020, 9:38pm

I would probably pressure wash it to make sure there is nothing else going on,

If not I would sand everything smooth, and pour the dent full with epoxy thickened with silicone powder.

After that cures, I would sand it smooth and then paint the whole thing. Being me, I would use a polyurethane paint.

bnystrom · October 14, 2020, 12:16am

Looking at the picture, I have a few observations and concerns.

First, that doesn’t look like Kevlar, which is naturally yellow in color. That looks like coarse woven fiberglass cloth. That would actually be good, because it’s easier to work with.
There appears to be air space between the fabric and the gelcoat, which is a real concern. The fact that a chunk popped off so cleanly tends to support this observation. If the gelcoat isn’t solidly bonded to the underlying layup, you can expect more repairs like this in the future, unless you can fill the void.
The folks who suggested tapering the edges of the hole are spot-on; you need to provide plenty of surface area for the new gelcoat to bond to. If the exposed fabric actually is Kevlar, be extremely careful when sanding the gelcoat, as Kevlar will turn into a fuzzy mess if you sand it. Your best bet is to use a carbide scraper to feather the edges, as it will not cause fuzz if you accidentally scrape the Kevlar. You can find them at paint, hardware and big-box stores. If the cloth is fiberglass, there aren’t any issues with sanding, but you still want to be careful not to weaken it.
Clean the area carefully with a strong solvent like lacquer thinner or acetone and allow it to dry thoroughly before you apply gelcoat. Make sure you get finish gelcoat, as typical laminating gelcoat will not cure in the presence of air. Yes, you can cover it or add wax to it, but finish gelcoat eliminates the extra hassle. My personal favorite is Evercoat finish gelcoat paste, which is thick enough to stay in place without running and it’s stronger than liquid gelcoat, according to the manufacturer, who makes both types.
Color matching white is no big deal. You’re going to be sanding the repair with fine grits (400 - 1500), then polishing it, and you’ll clean some of the surround area in the process.
Here’s a link to a gelcoat tutorial that will give you an idea of what to expect: https://briannystrom.com/kayaking/tutorials/gelcoat-repair/
This fiberglass repair tutorial also shows reapplying gelcoat over the repaired area: https://briannystrom.com/kayaking/tutorials/fiberglass-repair/
BTW, although it’s not pertinent to your particular situation, you can apply gelcoat over fully cured epoxy, as is show in the second tutorial.

paddler231560 · October 19, 2020, 7:51pm

The pros use super glue jel with baking soda as a filler

bnystrom · October 21, 2020, 12:10pm

Pressure washing would potentially drive moisture deep into the gap between the gelcoat and the laminate (and possibly make it worse), where it would be difficult to get out and could potentially cause problems in the future, particularly if the boat will be exposed to sub-freezing temps.

I assume you mean fumed silica, which is a common thickener for epoxy. You don’t want silicone anywhere near a kayak, especially a repair.

Why would you sand and paint the entire boat when you’re only doing a small gelcoat patch?

grayhawk · October 21, 2020, 6:55pm

Like they say in the model R/C groups… “Paint adds weight”

magooch · October 22, 2020, 5:19am

First step is to really determine what fabric you’re dealing with and the nature of the separation of the gel coat from the layup. Find out what kind of resin was used in the layup if you can. I would probably call a manufacturer of resins etc. and see if they can tell you what is compatible with polyester gel coat. Also ask about what to use as a filler if there is a void that needs filling. In any case, you can protect the fabric by taping over it while tapering the edges of the hole. I use black plastic electricians tape to protect all surrounding areas that are outside the damage zone.
Masking tape sometimes doesn’t stick well and it tears up so easily.

When you are satisfied with the filling and it has cured, clean it thoroughly with acetone. Wipe the wound thoroughly with acetone again just before applying gel coat. Brush the gel coat on as others have said–a bit higher than the undamaged surface. It will shrink a little.; if it does–no big deal. Just repeat the application process after the original application has cured. Keep in mind that you do need a working temperature of at least 65 to 70 degrees F to do any of this work… I usually let it cure over-night. .

You do not need waxed gel coat, or mylar , etc. to cover the curing gel coat, just cover it with waxed paper. Here again, I use black plastic electricians tape to seal down the waxed paper, because it sticks better and is easier to peel off.

When the gel coat is fully cured tape off all of the surrounding area to protect the undamaged get coat from being scratched while you are sanding down the new gel coat. Start with dry 400 to 600 paper, just to work it down closer to the surrounding surfaces… This initial sanding is very easy and requires very little pressure… When it looks like you are pretty smooth, switch to wet sanding with 600, then 800, 1000, 1500 and 2000. This all goes very quickly and it will look like you are done. You’re not. Now you will need a real good random orbit polisher.with a sponge type polishing pad. Use any cheap polishing compound and polish to suit. Wipe on your favorite wax, or other finish and you’ve got a brand new boat.

Actually in the finishing process, I remove all of the protective tape around the repair and blend the polishing with the surrounding area. If all of this sounds hard, or tedious–it isn’t and it is very rewarding.

Another little note is don’t try to fix too many damaged areas at the same time, or at least not any multiple larger repairs. You will only have about 20 minutes of working time with any one mixture (gel and hardener), so keep the amount of mixture small. Be sure you understand the right amount of harden per amount of gel coat. Check the instructions on the gel coat container. I generally use about one drop of hardener per teaspoon of gel.

You will find that with a little experience, small repairs can be made without all the protective taping as you will quickly learn to keep your sanding within the linits of the wound.