Composite Durability II

G2d’s remark in the original thread:

gelcoat?!? We don’ need no steenking

Posted by: g2d on Oct-23-10 11:53 PM (EST)

gelcoat! More filling, less taste!

Got me wondering: would it be feasible to strip the gelcoat off a carbon-kevlar kayak (or canoe for that matter) and put a clearcoat on the composite?

A clear coat is a gel coat that is clear. I think what you want is a very thin gel coat.

True in some cases, but several
builders add nothing to the surface except pigment. I have no gelcoat whatsoever on my Bluewater tandem, my Millbrooks, and my old Phoenix and Noah. For decades, some knowledgeable builders have not seen any reason for gelcoat, clear or not.

clear coat
Clearcoat is normally catalized polyurethane paint, it is not gelcoat. It’s also extremely toxic until it’s set, it’s not a home project.

Bill H.

Rember why the gelcoat is there…
…in the first place. It provides a sacrificial abrasion layer. While it’s easy to make remarks about not needing gelcoat on a boat, if you’re likely to encounter rocks, barnacles and the like in your paddling, you’ll be glad to have something between them and your composite. It’s a lot easier to repair gelcoat than to repair composites and gelcoat wear doesn’t compromise the integrity of the boat.

As to your original question, you’ll never be able to get the boat to look like one that’s made with a clear coat, as the gelcoat will be in the weave of the fabric.

Hey Bryan
Isn’t the gel coat supposed to counter UV degradation also? I think I read that somewhere.

It’s a lot easier to make "pretty"
repairs to a gelcoated boat than it is to a boat made with no gelcoat, but some of us just never cared about “pretty.” Smooth, strong, light, yes, but not “pretty.”

You are right about gelcoat being an ablation layer. But a boat built without an ablation layer will go through a lot of field ablation before the owner is forced to do anything about it. S-glass has a combination of strength and resistance to wear that can’t be matched by any other composite cloth I know of.

Yep, regardless of what’s been said, the reason for the gelcoat, other than to make it pretty and easy to sell, is to resist UV. Composites don’t like UV.

Bill H.

Thanks, good info
I was kind of looking for a winter project so I wouldn’t have to clean the basement, oh well, where’s the broom?

That too.
Gelcoat serves several purposes.

It’s not just about being "pretty"
I don’t see the point in damaging the structural layers of a boat through abrasion if you can avoid it. While S-glass is certainly very durable, you’re going to have to replace it when it gets damaged and the repair will not have the same integrity or appearance (assuming clearcoat) that the original laminate did. A clearcoated glass boat is not especially attractive, which is probably one reason why clearcoat is used mainly on Kevlar and carbon/Kevlar boats. One additional advantage of gelcoat over clearcoat is that assuming that it’s white or another color, it’s very obvious when you wear through it, so you can repair it before you do structural damage.

It’s obviously a personal choice, but I don’t like seeing gelcoat “written off” as useless, as it serves several important purposes and there ARE advantages to using it on a boat vs. other alternatives.

BTW, if you want to see serious abrasion resistance, try adding a layer of Dynel to a boat. The challenge is that unless it’s vacuum-bagged, it will soak up resin like a sponge.

Make a paddle or 3.

Dynel isn’t a whole lot more,
structurally, than gelcoat.

The philosophy behind no-gelcoat boats is that they don’t wear easily, so that any structural damage to the outer glass layer does not happen fast enough to be of concern.

One of my '73 gelcoated boats wore pretty fast until it reached the outer glass layer. Then wear slowed quite a bit. Eventually I laid some 6 oz glass cloth over the wear line.

Whatever weight I have in a hull, I want it to contribute measurably to structural strength. Gelcoat doesn’t do that. A layer of gelcoat makes any weight target harder to achieve without compromising strength.

stripper boat… NM.

Great Idea!
I’ll use the broomstick!