Some people I know run for the soap and water when a drop of jelly spills off a sandwich. They won’t eat powdered doughnuts, or even ice cream cones for fear of the messiness. Not me! I’ll happily lick chocolate off my fingers, my knuckles, my palms, the back of my hands, my elbows and all the way down my arm, almost any surface. However, messiness aversion comes on strong for me when we substitute epoxy for chocolate.
So with that introduction, and with an intermission between boat building activities, I’m using this posting to compare a couple of boatbuilding techniques.
First, a very brief survey of my boat building experience. It includes a lot of self study, a couple of weeks with very traditional cedar strakes on oak framing at the Wooden Boat School, a decked canoe built with solid wood planking around solid wood bulkheads using copper and bronze fasteners, and a decked canoe built with plywood using stitch and glue fastening.
Eva Won, built to Harry Bryan’s Fiddlehead drawings, is as close to “traditional” boat construction as we get with small solo boats. I intentionally said traditional boat and not traditional canoe because the traditional canoe is made of many thin steam bent ribs, very thin planking and canvas covering. This “canoe” is built more like a boat than a canoe. It just has the general shape of a canoe.
The preponderance of the work for this boat was traditional wood working. I spent a lot of time dimensioning lumber. Yes, I could have had the lumber yard do that milling, but I enjoy it and enjoyed it for Eva Won.
After milling, the actual building entailed a lot of joinery, none of it including straight lines or 90 degree joins. The boat takes shape from the basic structural components, the stems and bulkheads, carefully positioned on a strongback. Part of the shaping includes finding the shapes of the strakes through the spiling process. Careful fitting was essential at almost all stages.
Joins of the bottom and structural members were glued and screwed, but with very little real gooey epoxy. Joins of the strakes were wood to wood, held by copper clinch nails. No glue. These joints and others were sealed with gooey stuff that allows reversal.
In short, this form of construction is mostly careful woodworking and joinery. Note that I said “careful” and not “fine.” It’s a boat, not a piano.
While there was a bit of epoxy glue, it was rather small. I used less than a quart of West System resin.
Finish was traditional paints.
There’s little milling with this technique. The careful work was cutting high quality marine plywood to specific patterns. In general, this plywood is mostly 1/2 the thickness of the lumber used on the previous boat. After the parts were cut, small holes were drilled at intervals along the edges. The boat took shape when these edges were pulled together with short lengths of twisted copper wire, the stitches. No strongback is needed because the boat is self-shaping.
After it’s wired together, thickened glue and fiberglass fabric was used to reinforce each join. Hence the “stitch-n-glue” name for the technique. Next, a layer of fiberglass cloth and several layers of epoxy coating provide extra strength for the thin plywood.
Epoxy, epoxy, and more epoxy define the bulk of the work time. Followed by sanding epoxy, sanding epoxy, and sanding epoxy. Almost a gallon of epoxy.
Finish was traditional paints. They are needed because as tough as epoxy is, it has little UV protection and needs paint or varnish to provide that protection.
Boat building is often thought of as a winter activity; build a boat instead of trying to break through the ice to go boating. Traditional boat building has little sensitivity to temperature. Many boat building shops are unheated or, like mine, only moderately heated. Typical boat building attire includes lined jeans and boots, flannel shirts sweaters and jackets. In short, it’s rarely too cold to build. Ah, but not so with epoxy. Around 40 degrees, it doesn’t react at all. 50 degrees is bare minimum. Warmer is always better. So, stitch-n-glue building can’t happen in the dead of winter in many shops, and takes longer (slow cure times) in cool shops.
Then, there’s weight. One of the popular beliefs is that glued plywood construction is “ultralight.” There are several boat building books promulgating the technique and having “ultralight” in their titles. Yet, my two boats ended up within a few pounds of each other. They are relatively the same volume (one 12 feet long, the other 13, the short one a bit deeper than the other). One weighs 47 pounds, the other 51. There’s no great weight difference.
At this scale, small solo craft, there’s no weight advantage with the “ultralight” technique. The weight advantage actually becomes manifest in larger boats. Consider a simple 14 foot “Flatiron Skiff” built of traditional materials. That boat, with the capacity for 3 adults a child a dog and two cats, will have stout side planks of 3/4 inch thickness, or more. The bottoms are usually many cross planks of 4/4 thickness. With strong frames, thwarts, and gunwales, those skiffs end up at 150-250 pounds, and require a trailer for transport. A similar “Flatie” built as glued plywood is significantly lighter, often finishing at 70-80 pounds, and being “cartopable.” Similar savings can be found for a variety of round bottom small boats, those intended for 400-700 pounds of load capacity. There is truth to the “ultralight” idea, but it’s for larger boats, not the solo canoes.
So, how do the techniques compare? From my experiences I see it as: joinery versus goo spreading, cold weather building versus warm weather building, keep on joining versus wait for goo to cure, easy finishing versus lots of sanding, using my good ole badger hair brush versus using lots of throw away brushes spreaders rollers and gloves.
Which do you enjoy more?
Lastly, epoxy isn’t chocolate. Epoxy sensitivity, manifested by various allergy symptoms including severe rashes, is inevitable for anyone who is constantly exposed without proper protection. You don’t get that with chocolate.
Want to guess what our next boat might be?
photo credit: Sara Goldsmith via Flickr