Waster my 1st cup epoxy - what's next?

Last night I mixed 3/4 of a cup (total mix) of epoxy in preparation to apply a 3" fibergalss lightweight tape on about 30" inside seam on the kayak.

I did not know how much I would need, so I mixed what I thought would be just a little more. I ended-up dipping my brush in it 2-3 times and that was it - the rest (may be 90%) had to harden and be trhown away as I simply did not need it…

Now the question. I could not for the life of me use the plastic spreader - it would just move the cloth around and lift it etc. Was I doing something wrong or what?

All I used at the end was a cheap painter’s natural bristle brush to 1st apply a thin strip of epoxy then slap the fiberglass tape onto it and then paint/saturate on top of the tape till it dieappeared. Then push here and there with gloved fingers to make it stick where it was supposed to. Mostly fine, but the edges of the tape length-wise seemed to create a slight edge and I was tempted to slap a piece of garbage bag on top of it to smooth it and press it down. That also worked OK, but I did not have anything to compress it with, so I mostly used that to spread the epoxy into a thinner layer away from the repair area so I would have less sanding to do.

I cured it overnight at 120 degree F (put an electric heater under the boat and it worked well) and now I got a mostly cured I suppose repair. But it has some signs of the plastic wrap on it.

What’s next? How to smooth it and do I need a filler coat? I think I got enough stiffness as it is from one layer…

Second, I want to apply a layer of carbon on a larger area of the hull just under and in front of the seat for about 20" to cover some blemishes and to stiffen it a bit. Would this hold over time to wear? The carbon fibers I have exposed here and there now are awfully frail and break… I understand why the kevlar weave is there as well -:wink:


use multiple coats to fill the weave
I built a couple of stitch and glue wood kayaks years ago and got a little experience with fiberglassing then. Others here, I’m sure, will share their much greater experience.

Mix the epoxy in small quantities, as you have learned. Depending on your catalyst and the ambient temperature, you want to have enough working time to not feel rushed, especially when learning. It is best not to try to completely fill the weave of the cloth in one application but rather to use several thin applications to fill the weave. The plastic spatulas and scrapers work fine once you get the hang of it. You can also try using those disposable foam paint brushes. In order to get the cloth to lay down where you want it, you generally need to “wet out” all or most of the cloth to give it enough weight to cooperate.

Beginners nearly always use too much resin which increases weight and then needs to be sanded off. The resin can be sanded, when completely cured, just like wood. You would be wise to wear a mask or work outdoors. Expect a lot of dust. The catalyst in the epoxy is also quite allergenic. You may not initially react to skin contact, but you may become sensitized by repeat exposure and the contact dermatitis that results can be most unpleasant. Make sure you wear disposable gloves as you will inevitably need to touch the wetted cloth to align it.

Sounds like a normal learning process
along the way. I never mix more than 20+ ml of epoxy at a time, using a single squirt of West metering pumps. It’s amazing how little epoxy can do the job, and more is quickly mixed when needed. However, if you mix a lot, the heat released as the epoxy starts to “go off” will cause the larger volume to gum and harden before you can use it.

It’s a good idea to paint a bit on the surface and then lay the cloth on it. A spreader is hard to use on the inside of a boat and a disposable brush can work better. Just work from the center outward until you can see the cloth is wet with air out of it.

I would not worry about sanding an inside repair or filling in the weave with resin UNLESS you or your gear will be contacting the rough edges of the cloth.

On the stiffening project, it would be better to use Kevlar inside. But the carbon will be OK, and you can add a bit of resin to the weave to protect it from foot scuffling. I have a slalom boat that is carbon inside, and it has not seemed to be wear-susceptible with epoxy in the weave.

Welcome to the club !
I would have used a much stiffer piece of poly over it, and taped it down with duct tape.

It comes out glass smooth.

I use those 3 ring binder clear plastic pieces that you slip a piece of paper or picture into or a overhead transparancy film



Some answers and more questions
Using pastic to press would worke well on the outside where the boat is convex and I can wrap the pastic around it. But I could not come-up with a good way to do it from the inside, plus I had two bulges from the recessed deck rigging to work around… So it came out a little rough but with not too much epoxy I think. I’ll probably just sand down the few rough points and be done with it - seems now just as stiff as the undamaged areas so I guess I do not need a second layer. It’s not in an area where I or gear touch nor do I see it unless I stick my head inside the cokpit so it needs not be pretty…

For the second part of the repair, which is primarily to cover cosmetically and less so to stiffen the cockpit area, I’m still not clear what to do. It would be about 1-2 square feet worth of area if I cover with a single piece. That’s still one of my main questions - I would love to somehow vacuum bag it to minimize the amount of epoxy used and for a thinner layer overall but do not know how can I bag just that small concave area. I have clear access to it, just can’t visualize a way to do it, short of filling the cockpit with a bag with water or something similar to press down with it on the wetted cloth. But then I’m afraid I might move the cloth out of position, fold it and not notice or what not. Any suggestions?

I got the slow hardener so I have at least 20 minutes to work and judging by how long it took before the repair started to set before I put some heat under it (in what was bout 70 degree temp before) I think I would may be have may be twice as much time at ambient temperature of about 70 degrees.

Resin Roller
We use a Pintar Fibertex roller that’s especially made for wetting out cloth when applying tape. It has very short, stiff bristles that seem to penetrate the weave well - it doesn’t tend to lift the tape at all. Roll on a coat of mixed epoxy resin, embed the tape, then roll again until the tape wets out. We get them thru a local fiberglass supply store - each roller can be cut into two or three sections with a hacksaw - works out to about $1.00 a shot…

A plastic scraper can then be used to work any little kinks or bubbles out of the tape. The plastic scrapers are mainly useful to spread resin over wide areas of the hull and deck panels - perfect tool for that job.

I find it can really help to dry-fit everything before mixing epoxy - that way, I’ll realize that I don’t have the length right, or I need to cut a wedge out to take a curve, or I’ll need a way to support one end of the tape until I can press it down…all the little things that can leave you with a tub of smoking epoxy…

I can give the roller a try
That should work well for the larger area I want to do next. And thanks for the dry-fitting suggestion - I did indeed do just that and it helps - my first area to repair was not particularly tricky and now that I’ve done one, I think the second should go a lot smoother, with less epoxy on the first coat and then I’ll probably just paint a second coat for smoothness if I do not find an easy way to bag it…

Some suggestions

– Last Updated: Apr-19-09 5:14 PM EST –

On a seam repair, there is no point in adding more epoxy to fill the weave, as that's purely cosmetic and it's not a visible part of the boat. You won't gain any strength and you'll just waste more epoxy.

The best tool I've found for shaping/smoothing glass tape edges is a carbide scraper. You can get them in the paint department at home centers and hardware stores. Get one with a slightly curved edge. Don't be tempted by cheaper steel scrapers. Remember, you're shaping glass, which is a hard material and it will dull steel in a heartbeat.

Carbon fiber has very low abrasion resistance, so it's not suitable for lining a cockpit unless you put a layer of fiberglass over it. If you're using carbon fiber for stiffness, fine, but if it's just cosmetic, you's be better off to lay in some glass and paint it black. If you want to make sure that it lays flat after application, cover it with a polyethylene sheet and lay bags of water on top of it.

what Brian said, scraper
when the epoxy gets to a non-tacky “green” stage that feels like soft plastic you can scrape down those rough selvaged edges that curl up.

I did the very same thing
on Saturday! I had to repair a tear in the side of a canoe, a 3 inch square on one side, and a three and four inch square on the inside. I cut my patches, then mixed 2 ounces of resin. After I applied the patches, with a brush, I was left holding the cup with 1.5 oz of mixed resin.

A little goes a looonnngggg way.

Thanks for the tips
I’m not sure how stiff it is supposed to be but I think it can use a little something. It yields a little more under pressure than the rest of the hull forward and aft of it, but in these other places the hull is narrower or close to the rear bulkhead so these areas are naturally more stiff - it might just be the way it is. I’m not keen on wasting carbon if not needed and if it would just create more work for me to cover it with a layer of glass to make it durable… I’ll probably fix the outside seam, paddle it for a while, then decide if I’m up to doing anything in that last large area…

It’s the area under the front and slightly ahead of the seat, so it won’t see much abrasion from feet but might from the seat.

Hull flex is normal…
…in the center area of most boats. The hull is wide and relatively flat, so it’s more prone to flexing. Actually, I consider it to be an advantage when you land on rocks or logs, as the hull will flex rather than cracking.

I like using the plastic
from coffee cans. i cut to size, and find the plastic nice and flexible to wet the glass around curves.

I think I’ll just leave it as is
In the larger area. May be paint some epoxy on the frail kevlar strands here and there or may be just do nothing… Will let me get on the water sooner this way -:slight_smile:

Thanks for the thoughts!

You can wet out the tape on a flat work surface, roll it up and then unroll it on the seam, working it in with a stiff brush… The tape is sewn on one edge to keep it from unraveling and can be sanded off once dry.

More than one coat is purely cosmetic and doesn’t add strength only weight.

I did not pay attention that only one edge is sewn but I did notice there is a slightly thicker edge. I’ll sand down rough areas today. I guess I effectively did what you said, except I did it in place since I had good access to the seam area - that’s right in front of the cockpit. Good hint about rolling it after wetting if I am to do something like this elsewhere in the future…


Try a scraper instead of sanding
It gives you better control and you don’t produce any itchy, dangerous (if you breathe it) dust. I find it to be faster than sanding, too. I consider a carbide scraper to be a “must have” tool for working with fiberglass.

Carbide Scraper

– Last Updated: Apr-21-09 12:41 PM EST –

I just relized what you were talking about - the scrapers used for removing paint or smoothing small patches, but from carbide steel.

How do you use that? Do you use it like a chisel to cut out the exess or do you drag it back to smooth? Would a chisel work too (got one as well).

And what did you mean by "curvy" edge model? I got some "cheap steel" ones in the garage that may just do the trick as my repair is relatively small, but would like to know for future reference.


You scrape with it

– Last Updated: Apr-22-09 8:40 AM EST –

Bahco (formerly Sandvik) makes a handled carbide scraper with a 2" wide blade that's straight on one side and slightly curved on the other. Here's a link to it:


It's designed to be used with a pull stroke and it works great on fiberglass.

I get it now…
I did not visualize it like this, but this tool makes sense now. I was thinking of the straight scrapers…

The one I have looks like it but is straight and I imagine would not work nearly as well with a pulling motion. I’ll check and see what my store carries.