Am also curious about penetrating expoxy. Would this be something to look into since I am using cheap plywood?   https://masepoxies.com/product/penetrating-epoxy-resin-wood-hardener-sealer

By the way, this appears to be the expoxy offered by CLC: https://masepoxies.com/product/low-viscosity-lv-epoxy-resin

and I am wondering if I should instead use the resin and slow-hardener found here:  https://masepoxies.com/product-category/marine-epoxy-system/

Nathan,

Unless you are forced to pinch every penny, I would recommend using materials from CLC. CLC has had long experience supporting amateur and home builders. When I built my Peeler Skiff back in 2014, I was impressed with the quality of the epoxy and hardener provided. It was odor free, very predictable, adhered well, and protected the plywood well. That is especially important if you are not using marine plywood.

Unless you are a very  experienced plywood an epoxy boatbuilder, you might find that deviating from CLS's recommendations could be an expensive false economy.

Regards,

Dick

Thanks Dick,

As a follow up, do you not see any real benefit to opting for penetrating epoxy in order to shore up my cheap plywood?

The price of CLCs kit doesn't bother me, but I assume that they expect most folks to be using marine-grade plywood already. So want to make sure that there is not a better option to seal up lower quality wood.

Ever hear the expression "putting lipstick on a pig"? 

That's pretty much what putting anything onto typical lumberyard plywood could be characterized as.

Saving money on plywood for a boat, then spending money to make it more durable isn't a wise choice. What you'll find in lumberyard ply will include voids in inside layers, 'football' patches often too and maybe even on surface veneers, not the best glue for bonding those layers together.

It doesn't take much bending to show these defects' presence, maybe not at first but it'll happen.

If you're gonna build a boat, skimping on materials is a fine way to cut the value of your time spent a'billding by a considerable degree.

As for colloidal silica vs. cell-o-fil: both have their place, both are common epoxy fillers used to thicken the epoxy matrix, both are structural additives. Keep in mind that it's the epoxy that provides the strength, fillers are added to modify epoxy's working characteristics to facilitate placement and finishing. SIlica's heavy when used alone, cellofil and wood flour are lighter. Often a better filleting mix can be had with using silica / cellofil in combination to make placement and subsequent finishing easier than with either one alone.

Here's a great guide to selecting and using various fillers when messing about with epoxy. The Gougeon folks retty much invented using epoxy for boat building half a century ago, the stuff they write about it has is applicable even if you're not using their brand of products.

Nathan,

It is my experience and opinion that "penetrating" epoxy does not significantly penetrate the sound wood that boats are built from. It is only good for penetrating rotten or punky wood, and even then I would trust it only for cosmetic, not structural, purposes.

To truly encapsulate and protect wood from water requires a significant surface layer of epoxy (preferably with supporting fabric) and the epoxy, itself, must be protected from wear and UV light by the appropriate marine paint or varnish.

SPCLARK is right about false economy. I wouldn't want to build a boat from exterior (not marine) plywood. Not because it isn't strong and durable encased in epoxy and glass or dynel, but because of the extra labor involved both in construction and in finishing.

Stitch and glue construction depends on the uniform bending properties of quality marine plywood. Exterior plywood is intended for flat surfaces. The types of wood and glue used, knot filler pieces, and allowable voids make it very difficult to bend into the fair curves of a CLC design without splinters and stress cracks. Not to mention that getting a boat-quality finish on exterior plywood will involve al lot of extra filler (weight) and labor; and still be substandard.

H.H. Payson & Company in Spruce Head, Maine, sells boat plans, and patterns for building boats with exterior plywood. They are good boats for their purpose, but the are not stitch and glue and they are not the elegant designs from CLC.

If you are new to stitch and glue boatbuilding, opting for cheaper plywood is setting yourself up for suffering and potential failure. There are many reasons that experienced boatbuilders opt for high-quality marine plywood. I fear that you might have to discover many of them the hard way.

Regards,

Dick