Eva Too

The aft bulkhead doesn’t fit as well as I would like, probably a consequence of the lofting error that kept the garboard plank from joining the bottom well. When the bulkhead’s bottom edge is flat against the bottom, the top does not rise high enough. When lifted up, the top section fits very well but leaves gaps below. Some builders of stitch-n-glue boats would suggest using it anyway. Just wire it so the top meets the sheers and fill the bottom gaps with thickened epoxy. It will be reinforced with fiberglass tape anyway. I figure that structural members ought to fit well, so I’m not happy with the gap filling suggestion. I remade the part.

Of course, there was not enough left over plywood for the complete part, only enough for the bottom half. OK, lets cut and butt join. How should that spliced on piece be laid out accurately? The corners are the critical point and there are only four. The other lines can be constructed if they are accurately marked. Ah-ha, a quickly made pointing stick will do the job. I’ve seen some complex shapes defined with pointing sticks. I inked the lines on the back (never seen) side of the bulkhead to show you the technique. The builder’s triangle on the stick was not for the usual up / down, but to show which surface is visible, eliminating any error due to the point not being precisely centered. (See, precision is not essential in all layout tools.) The rest is a matter of waiting for epoxy to cure, cutting to the new lines and trimming to fit more snugly than the original part.

Jamestown Distributors provided a ship date well off into the future when I ordered the hatches and some other things from them. Then, they beat that estimate by well over a week. Exceeding expectations is always a good way to keep customers happy.

The bulkheads close off the ends of the boat, forming watertight flotation chambers. Many people also use these areas for storage of the things they take along on their canoeing adventures. Access can be by hatches cut into the deck, or by hatches cut into the bulkheads. The true voyager likes the deck hatches for frequent and easy use. We won’t be using our canoes for voyaging, so the much simpler bulkhead hatches will do just fine. Round “deck plates” are the solution of choice for bulkhead hatches.

My turning saw, a bird’s mouth bench accessory, and a rasp made the work easy.

It’s a shame I don’t do videos. You would have enjoyed watching me reassemble the turning saw after inserting its blade through a pilot hole in the bulkhead. With tension loosened, a turning saw is an extremely loose collection of parts, and a human does not have enough hands to keep the parts together while reassembling it “in space.” Hint: use a little piece of masking tape to hold one end of the blade in its socket, and a short piece of string tied loosely around the toggle to keep it were it belongs.

Did you know that this is National Procrastination Week? Probably not. Formal announcements are planned for next week. (maybe)

The stitching is not done yet. A few more parts need to be wired into place. A fore and an aft bulkhead go in next. Two deck support knees also get wired into place. The building guide suggests trimming these parts to fit and after they are fitted start tightening all those ties. I found that the planks were not pulled well enough together (with the loose ties) to allow good fitting of the bulkheads. So, I did the tie tightening first. The boat gradually transformed from a flimsy shaky floppy uninspiring collection of parts to a pretty firm hull. It was a lot easier to know where to trim the bulkheads with the planks better aligned.

The bulkheads form watertight flotation compartments. Each bulkhead will receive a round hatch, and the holes for the hatches need to be cut before wiring the bulkheads into the boat. Some time ago, I procrastinated about ordering the hatches, and now I wait while they are on backorder.

Just as there are few straight lines in a boat, there are few 90 degree joins.  Consider the join of the top planks at either end of the boat, an acute angle. These kinds of joins, sometimes with compound angles, are hard to cut exactly with the first cut. I sneak up on the join by cutting a generous approximation and then trimming to exactness with a rasp. This works OK for small structural members such as the sheer clamp which is only 1/2 inch by 3/4 inch.

I made the cut mark on the top of the sheer clamp by holding the plank in what I hope will be its final position and then sighting along a center line that is drawn on the boat’s bottom board. The plank was so near vertical that the cut needed no compound adjustment. Sorry for no pictures of that cut, it was chaotic enough cutting a free floating floppy thing in mid air without also having to manage a camera. Then, as it says on the shampoo bottle, “rinse and repeat” for the matching cuts.

Now, the fun part, trimming to fit. A good rasp makes quick work of this, but only if you know where to use it. I learned this chalk trick technique from Greg Rössell at the Wooden Boat School. It’s very simple and works incredibly well. In words: Mark one part of the join with bright chalk. Rub that part against the other part of the join where it will leave a trace on the high point(s) of contact. Remove the high point. “Rinse and repeat” until the rubbing produces an even transfer. Done!  Click on any of the images for a larger version.

Stitch-n-Glue vs. Traditional

Responding to Al Navas’ comment wondering how the epoxy is used in stitch-n-glue construction, here’a very short and woefully incomplete comparison of two boat building techniques.

Traditional boat building, such as my previous boat Eva-Won, uses solid wood components, frames, bulkheads, and planks that are generally nailed to each other. The joins between planks are made watertight with caulking, usually a flexible compound. All of the wood parts expand and contract independently with changes in moisture, staying more or less watertight. Some joins, such as the sheer clamp, use epoxy as a simple glue.

Stitch-n-Glue construction uses marine grade plywood, much thinner and lighter than traditional boat lumber. As seen in the previous post, the parts are stitched together. Then, thickened epoxy combines with strips of fiberglass cloth to glue and strengthen the joins. The exterior is then covered with fiberglass cloth that is adhered (and filled) with epoxy. Surfaces that are not fiberglassed are clear coated with epoxy. The result has almost no structural components, depending on monocoque construction for strength. Since all the wood is encased, there is less moisture related movement than with traditional construction.

Pros and cons of each technique have been omitted for your reading pleasure.