Coating interior of resin-starved boat

[dan_f]

I have a kevlar kayak that apparently absorbs water from the interior. The kevlar cloth takes on a white cast when water sits inside for any period, even during a paddle. The layup appears to be rather resin starved, so the kevlar fibers have little protection.

I would like to coat the interior with a water-resistant coating, but am not sure what would be the best material. Easy application is obviously preferred. I am considering an epoxy primer/sealer like Awlgrip. Any suggestions?

Thanks,

Dan

[Ben Fuller]

Awlgrip is reasonably toxic; I am not sure you can get your head with resprirator into the boat. It also does not come in small quantities. Designed for spray application etc.

If you want to epoxy it consider a slow or no blush epoxy, then overcoat a UV protective polyurthane varnish, or forgo the epoxy completely.

[Brian Nystrom]

Awlgrip comes in quarts, which is about as small a quantity as one could expect.

If the boat was mine, I'd used epoxy. Before doing so, you need to rinse the boat thoroughly to remove any salt on/in the surface. Allow it to dry completely. You should probably wipe the surface with denatured alcohol to remove any oily material, at least in the cockpit, and allow that to dry. Mix the epoxy and pour it into a paint tray. I prefer to apply it with a roller made for the purpose (West System sell roller covers made for epoxy). I find that cutting the roller cover in half and using it on a 3" roller frame works best. Roll it on thin in order minimize runs.

While you're applying epoxy, you also have the opportunity to apply an extra layer of fiberglass where your heels rub on the hull, if you wish.

I wouldn't bother coating the epoxy with anything since it's inside the boat where it will receive little or no UV exposure.

[chetpk]

A number of years back while researching coatings, I was told by some boat builders/fiberglass fabricators that Awlgrip can only be safely applied while wearing a full suit with an outside air source. Unless Awlgrip has changed since then or has a new product out they absolutely recommended that it not be applied while just wearing a regular facial respirator. They were dealing with it in spray form and maybe rolling it on is a different issue.

You do want to seal it as Kevlar will draw in water.

[djlewis]

What's the boat? Isn't the manufacturer supposed to take care of that in the construction?

--David.

[Dee Hall]

Dan,

I observed the same thing early on in my Currituck, but I don't think it's what you think it is. Kevlar absorbs resin very well during vacuum bagging, and as long as there are no bubbles and the fibers are completely covered, it is not resin starved.

In fact, I believe that the whitish color you are seeing is actually the resin. The resin in a kayak can absorb a few pounds of water during a trip (yes, it really is heavier at the end). It doesn't degrade the resin since the resin lets it go as it dries out. Sometimes there are impurities that leave it white for a while.

I wouldn't seal it, or at least not the whole kayak. I sealed it near one of my bulkheads because there is a stiffener in mine for the keel that slowly wicked moisture through the bulkhead. I just used marine epoxy. However, if you seal the whole hull, it's going to add a lot of weight to the boat and could possibly seal IN moisture which might be bad.

-Dee

[dan_f]

Thanks to all who replied. The affected boat is an Impex Susquehanna. My carbon-kevlar Currituck has a cracked deck, but that's another story, and I've contacted Impex about that problem. I'm much less a fan of carbon-kevlar construction now.

The Susquehana is a plain kevlar layup. Here, the fibers look almost exposed to me, particularly compared with my Currituck which has a much smoother hull and compared with other boats I've seen. The fibers get white when exposed to water on a normal paddle.

If I were to add a thin coat of epoxy, what would be a good type to use?

Thanks for the warnings about Awlgrip.

[djlewis]

I suggest you contact Danny Mongno of Impex. He is really quite avid about staying in contact with paddlers and fixing their problems with Impex (and other brands too, amazingly enough). In fact, you may see him driving around here from time to time with a truckload of kayaks, heading out to teach, demo, play or just paddle with folks.

In fact, mention all your problems with Impex products -- thirsty kevlar, cracked decks, etc. He's amazingly responsive. (And he owns the company!)

http://www.impexkayak.com/contact.html

--David.

PS: Wow -- looks like some folks have already picked up on your issue and have posted on the Impex web forum...

http://www.impexkayak.com/chat/index.php

You might chime in there, or still consider asking Danny directly, especially about a cracked deck.

[dan_f]

David-I have contacted Impex about the boat with the cracked deck. They have been a bit slow about responding, but I hope to hear something soon. The correct contact person for warranty is joe@impexkayak.com . The e-mail address on the web site is a black hole.

[Dee Hall]

I have noticed that the carbon-kevlar layups are coated with a smooth layer of resin. This makes sense because the carbon fibers have no ability to stand up to abrasive contact.

Kevlar, on the other hand, is extremely strong, and can put up with lots of rubbing with just about anything. That is why you need to buy special scissors for cutting the cloth and tape. So unlike the carbon-kevlar layup, it is not going to be covered with extra resin. It will fuzz up a bit under your heels, but that's about it.

When they make the boat, they don't want to use extra resin because it doesn't add extra strength, that comes from the fibers stiffened by gluing them together with the resin. The whole point of using Kevlar is to keep the weight down, so adding more resin for cosmetic purposes defeats the purpose.

Because the surface is bumpy, with the only resin being that which the Kevlar absorbed (it absorbs a lot), it may look exposed, but it is very unlikely to be. If it appears to be turning white, then you can be sure that it isn't exposed. It is the resin that is turning white. The Kevlar doesn't change color.

I'd like to know Joe and/or Danny's answer on the white color. I've been curious about it. Since it hasn't cause any degradation of the resin in my boat over the years, I haven't been worried.

If you still want to add some epoxy in area, any laminating epoxy you find in a marine store is fine. You are going to have to sand the surface first which is going to expose those fibers, which are probably fine up until that point. Then wash it with clean water and wait for it to dry.

-Dee

[dan_f]

Hi Dee,

Thanks for the thoughtful message. Perhaps the discoloration that I have been seeing is indeed benign. All resin that I have encountered will turn white if soaked in water, so your explanation makes sense to me.

Dan

[Brian Nystrom]

You'll end up with a huge fuzzy mess and if you coat the resulting surface, it will end up feeling like sandpaper. Since the coat you're applying is for cosmetic purposes rather than being structural, there is no need to sand. Clean the surface carefully, first with water, then with denatured alcohol or lacquer thinner. Make sure it's completely dry before you coat it.

If you do need to shape Kevlar, use a sharp scraper, preferably a carbide scraper that will hold its edge. Scraping shears the fibers cleanly, rather than turning them into fuzz.

[dan_f]

Thanks Brian!

Dan

[Dee Hall]

Brian has a good point. I sanded the Kevlar when applying epoxy for structural changes such as when I moved the bulkheads. I lightly touch-sanded when sealing with epoxy. Even then, it did lift the fibers a little and create a rough surface.

-Dee