Viewing 6 posts - 1 through 6 (of 6 total)
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  • #2510
    Liam
    Participant

    I plan on building a small motor canoe which is a proximate 13ft using the stitch and glue method however I am unsure as to if I should use epoxy resin or polyester resin. I understand that epoxy is the better of the two but the price difference is a major factor so I was hoping someone could tell me if it would work and be structurally sound with polyester resin.

    #2516
    Louis
    Keymaster

    Hello Liam, good questions here we go.

    Superglue will be more the efficient for the stitch and glue method of creating a canoe.
    I presume you are wanting the resin to laminate the canoe after you have made the shell using the stitch and glue method.

    First of all, lets look at the perks of both Polyester and Epoxy and then I’ll follow it with some questions.

    Epoxy –

    Pros

    • Strong mechanical bond to most materials, it will take to wood well.
    • Sets at colder temperatures.
    • Waterproof.
    • Long life expectancy for wooden epoxy boats 20 years +
    • Good Chemical Resistance.

    Cons

    • Not very flexible will crack under stress.
    • Not UV resistant so it will require a topcoat.
    • More expensive than Polyester Resin and Vinylester Resins.
    • Can’t be thinned easily as the chemicals effect how the epoxy will set.

    Polyester Resin

    Pros

    • Can be made flexible using fairly cheap additives.
    • Can be used as a UV resistant Top coat with a wax additive in the last coat.

    Cons

    • Won’t adhere to wood as strongly as epoxy.
    • Requires temperatures of 20 degrees and above.
    • May allow water to penetrate if left in the water for long periods of┬átime.

    I personally have always used polyester resin for gel coat repairs and priming surfaces. I always used a syringe some disposable gloves, and a cup with measurements on the side. I add a flexible additive to the mixture so that flexible areas don’t crack. It’s notable that you can also address the flex and strength with laminating.

    However, that said in your case you will be adhering to wood so Epoxy will give you better results and less chance of delamination. It will however require a topcoat to seal it in. I’m guessing flexibility won’t be an issue if a strong cloth is used with plenty of layers.

    Conclusion

    Ethier will work but polyester resin will be cheaper and in my opinion easier to work with. You won’t need to worry about the topcoat. A UV resistant Epoxy with flexibility would be better if you can afford it. There are some flexible epoxies available to be on the safe side. But you will definitely need some form of epoxy compatible topcoat if you can’t find something with UV resistance and flexibility.

    Something to consider

    Imagen you have built the perfect canoe, you leave it outside for a few seasons but the epoxy has faded in the SUN and now looks a bit naff you can’t just paint over it because it’s a canoe any 1 part paint will fall off with use, you’ll need something strong and compatible.

    Hope that helps Liam!

    #2520
    Fergal Butler
    Participant

    Just my two cent’s worth if you are new to working with these I would go with epoxy you will get a stronger bond with the wood and more time to work with it, polyester can go off very quick and if you are not used to working with it you might end up in a mess. I use a lot of “west systems” epoxy it is more expensive but for the size of a canoe it shouldn’t hurt too much you can also buy it with pumps that make it very straight forward for mixing and they have lots of videos on their web site if you need any help.
    Best of luck.

    #2535
    Craig
    Participant

    Both epoxy and polyester will do the job well but getting a good quality brand is more crucial as some cheaper blended resins are very poor.

    One thing to consider is what kind of canoe you want? thick and strong will suit epoxy better or light and flexible will suit polyester better. Polyester has more flex but lacks strength. epoxy resin has its own strength with no substrate whereas polyester isn’t that strong without other materials to bond too.

    I would err on the side of choosing epoxy as the cost increase isn’t a lot with something as small as a canoe, but you will probably end up requiring a 2 part polyester paint to put on top of the epoxy to shield it from UV.

    #2743
    Liam
    Participant

    Considering the small size of the boat the price difference between epoxy and polyester will be relatively small along with the benefits it offers, I have decided to go with the epoxy.
    Which brings me on to a couple of questions:
    Can anyone recommend a good epoxy?
    What filler should I use?
    How much coverage would I get from say 500ml? (Just to get an idea of how much I will need)
    What’s amine blush and how do I avoid it/remedy it?

    #2930
    Nick
    Participant

    I’ve built several small boats (2 kayaks, a small tender and a sailing dinghy) using epoxy from Fyne Boat Kits which is both very good value and easy to work with. Otherwise East Coast Fibreglass is a very good supplier.
    My 4p on epoxy or polyester for small stitch & glue boats is always to go for epoxy for the structural work – the filleting and taping. Whether or not you then sheath it or coat it with epoxy (or even polyester)is much more debatable; it add a lot of weight and is only any good until the film is breached – then it hold the water inside the wood ! I would suggest that you forget sheathing/coating with gloop and go for painting – or even varnishing. For a boat that isn’t going to be in the water all the time (so long as you don’t need show quality) exterior quality house paint is fine.
    Amine blush is a byproduct of some epoxy types curing and is often not easily seen. What it does is prevent subsequent layers of paint or varnish from curing properly, so you need to get rid of it. You can get round it by either (a) covering the epoxy with a layer of peel ply (ECF sells it) when it is wet which is then removed after curing, taking the amine blush with it or (b) scrubbing the cured epoxy with a plastic pan scourer pad and a lot of fresh water or (c) sanding down then washing off with fresh water before painting/varnishing.

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