Tooling resin for adhesive and laminating

I recently received plans for a trailerable houseboat. The designer suggests using tooling resin for both adhesive and laminating 6oz glass to both sides of the the plywood used in construction of the hull and cabin. The cabin roof acts as a sundeck using 1/2" ACX plywood with support beams 16" on center. The designer also recommends a minimum of 2 layers of 6 oz glass with a layer of 6oz tape on the chines for the hull. I have used epoxy and glass, but never tooling resin. Back in the 70's I remember glass and polyester resin being applied to wood boats with less than spectacular results. I suspect the design was created sometime in the 80's when epoxy was fairly expensive. Tooling resin is very reasonably priced about $300 CDN for a 5 gallon pail, I estimate I'll go through 3. Can tooling resin be thickened like epoxy? I need some advice on using this material or should I stick to epoxy. I would like to prefab this boat in the basement workshop. The fumes from polyester resin would be unacceptable in the house, so I may have to do my laminating in the outdoors, how would this affect this type of resin?

 

I think that in the grand scheme of things, when you add up the cost of everything at the end, the extra cost of using epoxy instead of polyester (or this tooling resin) is going to be negligible.
So I would stick with epoxy.
And IMHO epoxy fumes are easier to contend with than polyester.

 

Tooling resin properties are low exotherm and low shrinkage, great for moulds but no benefit for sheathing plywood.
Epoxy is better if you want longevity.

 

The designer may be confused by the term 'tooling resin', it can mean many different things.

Virtually any resin can be used as a tooling resin, and there are huge differences in what is marketed as a tooling resin.

Some reduce shrink, others offer high strength, some both. Others have extremely high exotherms to achieve low shrink, and others offer low exotherms to do the same thing. Some are highly filled, some aren't. The resin base can be from a low cost DCPD, to ultra high cost epoxy, it all depends on what the tooling if for.

Epoxy will give you a much higher chance of a long term good outcome than any type of polyester resin. But the real determining factor is your attention to detail in the build.

It doesn't make a difference in the type of resin used if water is allowed to reach the wood. Drill one hole that isn't sealed well and water will get to the wood. The wood doesn't care if the rest of it is covered with the best epoxy there is, or the cheapest polyester resin, it will start to rot in the near future either way.

 

69256,

This is a tough call.
I used polyester resin on my house boat.
I had experience with it and very little with epoxy at the time.
I ended up putting an International epoxy barrier coat on before bottom paint.
No regrets but if I had it to do over, and had the money, I'd go with epoxy.

In your situation, with the smell factor alone, I'd advise epoxy.
It's money well spent but you'll have to decide which brand you'll use!

Ventilate your work space well if possible as epoxy allergies can creep up on anyone.
Spend each 5-minute mixing period outside staying upwind of the epoxy.
I good helper is a great bonus for mixing, etc.

EDIT: I've never thickened polyester. Never had the need.
Remember, you can epoxy over polyester but you can't polyester over epoxy.

 

69256,

This is one of my very slight concerns over this set of plans. And similar plans for Bolger's houseboat, the Lisa B Good, and even Escargot. With the design being dated and the designer having sailed over the horizon I think you have to apply some updates liberally. I was even thinking of purchasing plans to a similar design (Devlin? ) and using the Aqua Casa floor plan but construction tips from Millie Hill. But advice from sites like this help immensely.

Not based on experience, but a whole lot of reading I would:

• Use epoxy
• If he is suggesting two layers I am thinking he is suggesting cross-hatching the weave
• Use of "peel ply" or similar for all of these flat surfaces may reduce some of the sanding.
• Or since you are prefabing you can time it (I think) so a second coat of epoxy on glass goes on at a point in the cure where sanding may not be needed (is that crazy talk)?
• Use marine plywood for the hull and possibly the roof. I am reading (again, no solid experience so discount appropriately) the quality of exterior grade plywood has gone downhill?
• I only have the study plans and will again point out no experience but I was thinking thin sheaving of walls for rigidity but then foam insulation panels, house wrap with possibly metal siding for exterior and paneling for interior. I have to be careful with that idea. If he is suggesting ply/epoxy/fiberglass I would not alter that. End up with a singly glassed structure would certainly keep things tight rolling down the road.
• Saturate the wood before glassing. I have seen stitch and glue boats where if the glass is pierced the underlying wood starts to rot (similar to commercial construction where you have glass and a core material)
• I might be tempted to reinforce with a small bit of carbon fiber. But this is me trying to alter the design to reduce weight and increase towability

 

I've built a couple of small boats with epoxy. I found that even 3/4 ounce fiberglass is enough to seal up the plywood, and that's held up very well over many years, except where there's mechanical damage. Much less epoxy used this way.

I have some epoxy I got from a boatbuilder which is great for wetting out composites, but it actually makes lousy glue. I think something like the basic Raka is more all-around. That's what I used on my boats that held up so well outside, including for gluing. On the same materials where the laminating epoxy failed, very ordinary epoxy glue was far better.

Fiberglass cloth is NOT a light way to add rigidity. Slightly thicker plywood could add more stiffness for less weight. But it wouldn't be anything like as weather resistant with paint as it would be with 3/4 oz. glass and epoxy on it. That wouldn't weigh much more than paint.