Please visit our home site at

Anke and I live aboard WAYWARD, and wrote about it's design and construction at

Access to the net comes and goes, so I'll be writing in fits and spurts.Please feel free to browse the archives, leave comments where you will and write... I'll respond as I can.

Fair winds!

Dave and Anke
triloboats swirly gmail daughter com

Monday, February 3, 2014

Water-Based WaterCraft: Options in Boatbuilding

Water-Based Materials
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...

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).
Lagging Compound - This stuff is designed to saturate cloth for wrapping water pipe. Arabol, formerly made by Borden (Elmer's Glue), used to be widely used in home-built construction. Nowadays you have to go a-hunting. Makes a soft-ish surface that's can be cut or punctured (easily repaired), but holds up well in normal traffic. Mostly used for decks, though I heard of one lapstrake(!) hull that got an extra decade of life thanks to hull sheathing.

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?


  1. I think the primary reason for Boiling Water Proof standards is the glue may be used in an engine compartment. A broken or leaking coolant fitting or hose can result in boiling water on the INSIDE of the boat. Nobody said it had to be boiling seas on the OUTSIDE. Most epoxies will fail this test, BTW, since they heat-soften quite a bit.

    Yet another reason to keep an engine out of a boat.

    1. Never thought of that, but you're right. And like your solution!

      I certainly prefer WBP rating, if possible. If not, I tend to be wary, Payson's "boiling seas" comment, notwithstanding.

      Weldwood has a proven track record, and I have no hesitations using it. The Titebond III is still pretty new, and I haven't heard much marine feedback, other than from PDRs. But it sure looks promising.

      Meanwhile, we'll keep our engines, if any, well outboard! 8)

      Dave Z

  2. I have read somewhere on the net, that titebond iii is used (in your neck of the woods/british colombia) on professional fishing boat and others to provide watertight nonslip deck covering. I like titebond, I use it for general woodwork, and have been thinking of using it on the outside of the cabin on my boat, along with some suitable cloth. Still will use epoxy on the joints and corners though.

    1. Hi Joel,

      I've not heard of TBIII (which is relatively new) used as a binding resin for a cloth matrix. But I'm interested!

      You may have heard of the late Arabol, once made by Borden Corp (makers of Elmer's Glue). It was a water-proof version of Elmer's, designed for lagging compound. It dried to a soft-ish, flexible skin. It was often used for decking as a binder for cloths ranging from burlap to polyester. It has low but adequate adhesion (have to secure the edges, and can peel the composite fairly easily to remove (a feature)).

      Generally, I hear that, on fishing boats, 15 years could be expected from Arabol/burlap, and quite possibly longer for synthetic cloth. Occasionally, I hear that it did okay as remedial sheathing. No data on initial sheathing success (I imagine it would work well).

      After it's demise, we used a similar latex lagging compound on LUNA's decks, bonding fiberglass. Deck still looks good (17 years down the road), though it needs top-coat. We did get slight bubbling along the seams of her strip-nailed (not glued) deck, though never water of fungal penetration. I'd now install at least a thin layer of ply to stabilize movement, before sheathing.

      TBIII looks promising as an improved substitute. We're hoping that the much harder cure will be less vulnerable to chafe/puncture, while still being easy to patch/repair when necessary.

      Our tests (using acrylic cloth) look very good. Four coats filled the weave and bonded well to the wood and one another. (Latex) Primer also bonded well, and we can't scratch it with a fingernail (mine are pretty hard).

      In our next boat, we're planning to use TBIII/acrylic cloth for decks and sheathing above the copper-line. Should have field reports in a year or two, if all goes well.

      RE epoxy vs TBIII - Check this out (sent in by John):

      It's a thorough test of common glues by Fine Woodworking Magazine. Surprise results of careful destruction testing: TBIII beat epoxy for strength(!) by a nose, as well as the rest of the field!. Since neither are elastomeric (which I prefer for hull joins), this suggests that TBIII would perform as well or better than epoxy for hull joins, something that many have said of Weldwood. All three exceed the fiber strength of wood.

      Advantages of TBIII are, low cost, low toxicity (therefore little cost of safety gear), comes mixed (no powder exposure or mixing costs) and non-staining water clean-up.

      Gorilla Glue (moisture activated, though not water based) pulled up a distant last place. This confirms my impressions, though I'm still perfectly satisfied with its performance for wide area (sheet) lamination. Even at 58% of the strength of TBIII (test result), it's still a mighty strong glue.

      I'm interested to hear what you choose, and why!

      Dave Z

  3. Posted on behalf of JOHN:

    Hello Dave,

    One glue characteristic you didn't mention was whether new glue would adhere well to cured glue? If I remember correctly, the poly vinyl acetates (PVAs), such as white glue, yellow glue and Titebond III, do not stick well to cured glue, and other types of glue may not stick well to them either. Also, paints and varnishes may not adhere well to some types of glues.

    A couple of interesting links:


    1. Hi John,

      Thanks for those links... interesting, and somewhat at odds with one another.

      I'm a fan of 3M5200 for hull joins (moisture activated, reenforced PU, not water-based, elastomeric), and we've had perfect success with it (no leaks or failures, ever). It wasn't covered in either article, though the latter reports its class of glue as not recommended for hull joins.

      RE adhesion to cured glue -- good point, and one I'm not really qualified to report on (lack of experience). We rough up and/or heat most (old) glue surfaces before applying a new layer, on general principles, but have never done anything systemically.

      In terms of our TBIII testing, each layer was applied every few hours (10 max, overnight) with no special prep. Instructions say not to stress the joint for 24 hours... I'm guessing that it's not completely cured between our coats (which I prefer), though it gave no observable sign of softening.

      Dave Z