There is a bewildering range of epoxy resins on the market today.
So, which resins to use when building wooden boats?
There are two main types in use in boat building.
However, despite being used to build GRP boats they are not suitable for building with wood.
They are much less porous and have superior gap filling ability.
As with most things in life you get what you pay for.
Good quality marine epoxies are expensive.
The less you pay the more likely it is that the resin has been diluted.
Whether it’s been diluted with cheap filler or non solvent thinner it will reduce its quality.
Stick to (sorry about the pun) a good quality, well known brand of ‘marine’ epoxy, it’ll pay in the end.
Before we get carried away with how wonderful epoxies are we need to bear in mind that there are some and there is a growing concern among the scientific community about the adverse health and environmental risks of traditional petrolium based epoxies.
After application and during the curing process, epoxy resin releases a wax-like’ film onto the surface called ‘Amine Blush’.
This amine blush will prevent subsequent layers of epoxy and other products fully adhering unless removed properly.
The best way to reduce blushing is to work in warm temperatures (the epoxy sets up fast, reducing the blush window) and with humidity at low levels.
It would be best to avoid conditions where moisture is coming out of the air as temperatures fall.
Amine blush is water soluble so, thoroughly washing the cured epoxy with clean warm water, soap, and a stiff brush or Scotch-Brite™ pad is the only way to completely remove it.
Sanding before removing the amine blush may sand the blush deeper into the surface making it much harder to remove.
Even those products labelled as ‘amine blush free’ or ‘no blush formula’ are best washed.
Solvents like Acetone will not remove the blush.
If there is a good reason not to get your project wet, you can use West System’s “Peel Ply”.
Peel ply is a finely woven nylon fabric that will not bond to epoxy, however, the amine blush forms on the peel ply, not on your cured epoxy.
Simply follow the instructions to apply peel ply, ensure that the peel ply is thoroughly wetted out, let your epoxy cure and then remove the peel ply once cured and before applying the next coating, the blush will have formed on the peel ply not on the epoxy below.
Another advantage to using peel ply is that it’s fine woven pattern is impressed into the epoxy coating, creating a ready to bond to, graded, textured surface.
come in two
parts, the resin and a hardener
Mixing ratios will vary from one product to the next.
are numerous epoxy resin thickeners which are available commercially,
such as micro balloons, talc, silica and the like.
Most are strong and sand easily and are available in a range of colors.
You can use sawdust or even white wheat flour.
I have heard of pulverised limestone and Portland cement being used successfully, however these must be a bugger to sand.
A layer of fiberglass cloth is used to add a high degree of protection, strength, abrasion and impact resistance. There are a number of different forms.
There are some specialist epoxy resin coatings which can be applied to damp and saturated surfaces and even underwater.
There are also underwater epoxy putties which can be used for emergency repair work.
Epoxies present more health and environmental risks than any other boatbuilding materials.
Entropy Resins are made using a plant-based epoxy called "Super Sap" instead of petroleum based products.
Not only is “Super Sap” resin is sustainable but you can apply without fumes so there is no need to wear a respirator.
Environmental benefits include bio-based content sources and a reduced carbon footprint.
“Super Sap” uses a pine pulp based resin sourced from by-product of paper manufacturing processes and plant based byproduct from bio fuels processing.
It's relatively low viscosity and great adhesion to all substrates makes it an excellent composite laminating resin.
Some products even feature air release additives that allow for smooth brush on coatings.
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