Vaccum bagging a strip canoe

Hello fellows,

i m new to vaccuum bagging, and i want to improve my resin/fiber ratio to save weight on my next strip planked canoe. (see this thread)

The usual way is to wet lay outside with the strips still on the stations mold. I try to figure out the right way to vaccuum bag the outside layer.

The inside layer should not be a problem, because there is no more station mold.

My proposal :

when the planking is finish, take off the « wood hull » very carrefully from the station mold, instal a layer of vaccuum bag, re instal the « wood hull » on the station mold, and then install all the layers as drawn in this picture of my own :

1. Am I Right ? how to not perfore the vaccum bag film on the inside ?
2. The vacuum bag connector have to be on the inside or on the outside ?
3. My core is in LONG grain balsa. Will it stand the pressure of vaccuum bagging?????

thank you for your help

 

Your gains are really incremental for the risk and cost.

The wee lassie is about 3 yards of fabric or less. Using 10 ounces of glass for convenience, 100% layup results in 30 ounces of epoxy. A decent reduction from vac would be 10 ounces. And this comes at great risk that the fabric will get drysucked in places. You are basically going through a LOT of trouble here for less than one pound of savings and taking on quite a bit of risk.

Remember, that wood also needs resin uptake. How much for balsa, I do not know, but it could be on the order of 2 ounces per yard or so. This means you risk removing the resins that are needed for the layup. If the wood needs 2 ounces; then you suck it all away; once it cures; you'd have a bad laminate.

I say not even close to worth it.

The other issue is the weave will be unfilled; the strands on top subject to wear and uv. Weave filling is a classic part of canoe building.

 

Knowing from experience that woodstrip layups have air holes, vacuum bagging will result in a lot of unwanted resin removal. The other thing is the bagging material can result in a rough surface, which slows down the boat.

For less waste of resin on hand layups, use a sponge foam roller. Lightly apply resin to the wood, immediately cover the hull with fabric, roll out the bubbles. lightly apply more resin to fill the weave.

 

I have vacuum bagged items that can bear the forces on their own or in/over a mold that was supported fully supported on one side but nothing like a strip kayak. Wouldn't there be some deflection/flattening between the forms?

I would consider pre-cutting and weighing the cloth to determine the resin needed for the cloth. Then I would do a 'cheater' coat on the wood first separately to address the 'uptake'. Coat the wood, wait some minutes as one does with epoxy so it can soak in, and squeegee off any pooling or touch up dry spots. Then add cloth and the necessary resin for the cloth, wet on wet, wait some minutes, and squeegee together to make a tight lamination without voids or pooling or floating cloth. The cloth could also be saturated on a wet-out table and transferred if one is comfortable doing that. After the lamination has set , do the rest of the fill coats and other finishing steps.

 

you don't need to precoat if you are not using vac; the wood uptake is only a concern if you are planning on pulling resin off into breather media, or if the laminates are very light like 4 oz. For a 10 oz laminate with 10 oz of resin; there is plenty of resin available to the wood

 

Fallguy, I agree that starting 'juicy' or 'rich' with resin is a safe bet. I would normally do the same 1:1 over wood or low density foam. Subsequent lamination would use less resin, closer to ideal, and fill coats even less than that. The nice thing about epoxy is that one can mix a little more if running short or patch the floor if there is a little extra...

B0z0x, please let us know what you decide and how it goes.

Happy New Year to all!

 

Yeah. Match the weights of the glass.

A 9.1 pound per gallon epoxy works as follows:

weigh the glass
Say 3 yards at 10 ounces is 30 ounces.

30oz/16oz is 1.875#/9.1#/gal is is 0.2 gal epoxy at 128 oz/gal is 26 oz epoxy

had some champagne; check my math

 

As above absolutely.

Risks are not worth it & may end up compromised.
Best bet is to precoat lightly, foam roller or squeegee on a falling temperature with a porous substrate.
Jeff.

 

Hello,
ok i get it, no vac !!!!!