Better for Us
Better for the Environment
Two roads diverged in a wood, and I...
I took the one less traveled by.
- From Two Roads by Robert Frost
Water-Based WaterCraft: Options in Boatbuilding
VOCs (Volatile Organic Compounds) are nasty bio-hazards.
These li'l suckers tend to be very small molecules, which walk through flesh and bone. Usually starting in liquid form, they flow or smear onto skin. They are prone to go airborne (volatile), entering by way of the lungs. Penetrating tissue, they head to the blood stream and spread out to every cell in our bodies.
Every single intruder causes some damage to tissue, especially our precious nervous systemics. Exposure symptoms range from dizziness and nausea to convulsions to long-term health problems, cancer and even death.
Safety gear is highly recommended - barrier creams, protective clothing, gloves, goggles, respirators (better yet, forced air ventilation), etc.. Macho/macha is stupid, here, boys and girls. Safety gear reduces exposure but can't eliminate it.
Like radiation, there really is no 'safe level of exposure'. There's bad, worse, critical and deadly.
But hey! We're living in an Age of Material Miracles. And water-based products with no or low VOCs and/or toxicity are proliferating. It's is possible to build a successful boat, these days, entirely with water-based products.
Plus, water-based products can be cleaned up with water (before they're cured!).
There are down-sides. Few are 'recommended' for marine uses... no warranties for 'mis-use' of this sort. They usually require at least one porous surface, or exposure to air to dry. And they cure slowly in cool, moist conditions. If they get wet before full cure (even when apparently set) it can be a sad day. They are not all completly non-toxic... we should still use safety gear, but our level of risk-upon-exposure drops dramatically.
One thing to recall, in all this, is that epoxy - that wonder-stuff - is relatively recent. The whole concept of waterproof adhesive is relatively recent. Wasn't so long ago that we built boats entirely without adhesives, using tars and leaded puckies for waterproofing. It's a low bar.
Let's look at some categories of substances we need to build boats, and some water-based products...
Glues WBP (Weather and Boiling Proof) is the Holy Grail of waterproof glues. Yet, as many point out, we don't often sail in boiling seas. Everything-but glues have done very well in the field, and are well worth a look.
PSI (Pounds per Square Inch) of adhesion is pretty much wasted after the fiber strength of woods being glued is exceeded. Once the wood tears apart, does it matter if the glue is still going strong? In comparing, consider the stresses involved, the area over which stresses distribute and the required adhesion (vs the highest potential adhesion).
DAP Weldwood Plastic Resin Glue has been used for many years, above and below the waterline. It comes in powder form (careful... has its own dangers until mixed! You don't want to breath glue dust!). It is a 'structural glue', meaning it's designed for very high loads.
TiteBond III "barely passes the WBP" test, and is not recommended below the waterline. Nor is it a 'structural glue'. Okay. Use with discretion. Shorty Routh, of PDRacer fame, has wide experience with TBIII. He also mixes with fine sawdust (he runs it through a blender!) for a thixotropic, filleting compound.
Various Contact Adhesives - These are useful for a range of jobs. Water-based versions are now on a performance par with volatile types (which are particularly nasty, vapor-wise).
Various Roofing and Flooring Adhesives - These look promising for lamination of sheet materials. Anywhere that very large area allows lower PSI adhesion. When in doubt, use a higher quality (fully waterproof) adhesive around the perimeters. Viscosity ranges considerably. Consider researching the technical data sheets for each product.
From what I can see out there, on-line, and from my (limited) experience, either glue is fully adequate as a boatbuilding glue. We've used these on faces (as opposed to edges) of our boats, and never observed a failure.
The caveat is that it's very hard to spot a partial failure within a face joint. Note also that faces are only exposed along their edges, backed by a large 'interior' to the join. Edges have far less area interior to the join, so a failure along and edge's edge will be a much larger percentage of its total bond.
One strategy for a potentially soluble glue join is to apply sever 'sacrificial' layers over exposed portions, that are easily renewed should they degrade. Haven't seen it, but a stitch in time...
Elastomeric Adhesives, Sealants, Bedding Compounds
This is the one I'm still looking for. There are plenty of elastomeric 'adhesive' sealants which are water-based, but their PSIs are low. Still, if fasteners are employed for the primary bond, the elastomerics complement them with a flexible, water-proof seal.
DAP ALEX PLUS Acrylic Latex Caulk plus Silicone - Inexpensive, non-adhesive, modest elongation and easy to work with. We use this for all bedding above the waterline.
Sashco BIG STRETCH - This is a highly gap-filling, fairly adhesive caulk with great elongation (%500!). If we chose a fastener-based strategy, this is the stuff I'd use along the edges.
Titebond III - Makes a pretty fair sealant! Applied like paint, it makes a thick, hard surface with translucent, amberish tones. Thinned with water, it penetrates end grain. A couple of applications and it appears to seal plywood edges. So far, we've only tried samples in this manner, not in the real world.
Our plan for the next boat is to coat the interior with TBIII, and delay painting to see how things go. We like the looks, and it seems very easy to clean.
Various Latex Adhesives - There's a slew of inexpensive, special purpose adhesives at your local hardware store. Look around and think out of the box! You may find your solution.
In SLACKTIDE, we used cove adhesive (made for that plastic, bathroom molding that may edge your bathroom floor) for SIP foam ply adhesive. Notched spreaders to apply gave a decent grip. Sub-floor adhesives, carpet adhesives, and contact adhesives may all have their place.
Various Water-Based, Asphalt Emulsions - These are essentially roofing tar, once cured. Before that, though, they thin and clean up with water. Made a very successful below-the-waterline coating over plywood. May have potential as a laminating option.
This probably isn't the word I'm looking for. I'll use it to mean pucky used to bed a fabric (glass or acrylic).
To apply, lay down your fabric and wet down with water. Paint on compound and let dry to the touch (very fast in warm, dry weather). Recoat, full-strength and repeat until satisfied. Prime and topcoat.
Titebond III - Hello, again! Apply just like lagging compound. Difference is, the result is very hard and scratch resistant. Four coats filled the weave. We put our test sample out in the Alaskan winter a month with rain/snow/freeze/thaw. No sign of trouble, even where water was allowed to penetrate under. I'll report back here with results of paint/immersion tests in a couple of weeks.
Our plan, pending tests, is to sheath our next boat's decks and sides (above the copper line) with acrylic cloth set in TBIII. Should have a full report, down the road.
Paints and Varnish
Latex Primer/Paint - Latex paints have benefited from the huge housing market. They've eclipsed oil based paint for marine use. Cheaper, easier to apply, better movement, don't require periodic stripping.
Water-based PolyUrethane Varnishes - These provide clear coats which are often less brittle (and generally more durable) than VOC based types, and often easier to apply.
So, we have a full range of possible or proven, water-based materials covering every niche.
I can't say that I recommend going all water-based. But I do recommend considering whether a given application allows a water-based solution.
There are new, 'greener' products coming out as demand rises. Every molecule of VOC we can keep out of our bodies and the environment is a boon.
Shall we pursue a road less traveled?