Reducing weight of a Strip built hull

[Jim Dodd]

So lately, I finished up another Composite canoe. Where I use a stripper as a Male mold.
After I varnished the inside. It Dawned on me.
Why did I use Fill coats, two of them, to fill the weave of the fiberglass cloth ?

If I would have used a Saran Wrap type plastic, over the Wet out coat ? I wouldn't have needed the two fill coats, that I usually do.

I'm going to play with this on my next build.

I tried Peel Ply with no success, years ago. First it doesn't conform well to the shape of a hull. Second it still needed another fill coat to finish.

I use Window Heat shrink film, as a release, on my Male mold, and the Composite copy..
The finish on the inside of my composite, is smooth.
Now I need to wrap the outside of my composite, or stripper, after the wet out coat, and call it done!

Saving two fill coats would have a major weight saving effect !

What do you think ?

Have we been ignoring this weight saving Idea too long ?

Jim

 

[Gamma1214]

I'm not sure where you're saving the weight Jim. Is it on the inside of the stripper? I only use a wet-out coat (no fill coats) on the inside because I like the texture & extra grip.

On the exterior, I'd think you'd want to bury the weave. I've only had one scratch get into the weave so far but I'd be afraid every scratch would get deep into it with just a wet-out on the exterior.

 

[dutchlennart]

It could be , weight savings are looking after all things. From the bolds you use to put the seat in , the species of the wood , the cloth of teh glass or...

in the end working on your body to keep strenght up and weight down. Is to me more important before i hit 70. Then get the weight down from 20 tp 18 or something similar.

 

[Jim Dodd]

I'm not sure where you're saving the weight Jim. Is it on the inside of the stripper? I only use a wet-out coat (no fill coats) on the inside because I like the texture & extra grip.

On the exterior, I'd think you'd want to bury the weave. I've only had one scratch get into the weave so far but I'd be afraid every scratch would get deep into it with just a wet-out on the exterior.

The weight savings is from glassing, the outside of the canoe.
The weave is buried. so no fill coats required.
The weight savings is from not needing extra epoxy, to fill the weave..

So I need to be more clear.

Here is a simple test. Take a piece of cloth, lay it on some plastic, or wood if you'd like. Doesn't matter if it is S-glass, or E-glass.
Wet it out with mixed resin. Lay a piece of plastic, plastic drop cloth, on top.
Let cure, pull the plastic . You will see the weave of the cloth is filled, and perfectly smooth..
No need for fill coats.

The real test is to get a film of plastic, over the hull, while the epoxy, in the wet out coat, is still wet.

This would be easy if you were adding an extra layer of cloth, over just the Football.

Still working on it !

Jim

 

[Jim Dodd]

It could be , weight savings are looking after all things. From the bolds you use to put the seat in , the species of the wood , the cloth of teh glass or...

in the end working on your body to keep strenght up and weight down. Is to me more important before i hit 70. Then get the weight down from 20 tp 18 or something similar.

Picking up a 50# canoe and portaging it, is harder than doing the same with a 30# canoe.
It doesn't matter how much you weigh, or how in shape you are.

Problem, is reducing the weight of a canoe. Reducing the amount of resin needed to build a hull, by say 30% , without sacrificing the strength of the canoe ? Is a big thing !

This is all food for thought. My next canoe ! Right ?


Jim

 

[Gamma1214]

I'll certainly have to try that on some test panels before my next build. I'm not sure I understand the mechanics of it, though... How would the glass be completely buried? Does it float away from the hull during the wet-out? I mean, I suppose it would but I never would have thought it was enough to completely bury the weave if it were compressed with plastic.

You're exactly right; the only reason that I use fill coats is to bury the weave so, if it can be done during wet-out, that would be far better IMO.

I'll have to grab the roll of Saran Wrap & give it a try (but not til Fall... I'm way behind schedule already)

 

[Cruiser]

Hi Jim,
If you use .4 - .5 oz per foot per fill coat, you will be pretty close to the real answer as long as you don't apply heavy. The fill coats on my new canoe weighed in at 7.4 oz over 17 feet .... quick and dirty 7.4/17 times your boat will give you a number in the right ball park for what you could expect.
It is actually what I am planning for the thwarts, which are somewhat more easily shrink wrapped than a whole boat.

Brian

 

[Jim Dodd]

I'm surprised I hadn't thought of this before.
Getting a plastic layer, on the tumblehomed area of the wetted hull? Might be a real challenge !
Much easier over just the football.

As far as actual resin savings ? I was just throwing out a guess.

So what triggered this thread ? When I pulled my Composite hull, off the heat shrunk plastic, on the Male stripper hull.
I noticed how smooth it was, and the weave was completely filled.
Had I plastic wrapped the outside of the composite ? It too would have been smooth, with the weave buried.

I've been going over ways, to get the plastic on the wetted surface of the hull, without wrinkles.
Small areas, like the bias strips on the stems, is easy, with tape.

Now for the hull.

Jim