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Boat Building Techniques


Information about boat building techniques

Designing a Traditional Skin On Frame

I recently took on the task of designing and building a skin-on-frame kayak in the Greenland Inuit style. "Designing" a SOF kayak before building isn't really the traditional way. Typically they are built to traditional measurements based on an anthropometric measuring system i.e. using hands, hips, arm spans etc. as measurement units. These basic measurements may be tweaked based on the builders experience, making a wider/narrower or longer/shorter as needed by the user.

Trimming to a Feature Line

There are often situations where you need to trim a group of strips to follow a line, such as a chine or keel line. You could start by eye-balling the taper on each strip and hoping when you have finished installing them all that you have a smooth, fair line or, you could install a temporary strip then fit each strip one-at-a-time against that strip, but the easiest is to start by not doing any special fitting.

Form Reference Lines

I like a good set of reference lines on all my forms. These are usually supplied by gluing the paper form patterns to the MDF and leaving them there. The patterns have the reference lines so everything is good. But I'm making the Nymph and it is symmetrical so being lazy I can make two sets of forms at the same time by stacking up two pieces of MDF and cutting them both at once. But, this means the paper pattern is only on one of the two copies.

 

A quick strongback

I'm about to start building the first boats in my new shop. I'm going to exhibit at the Maine Boat Builder's Show and I need some boats to bring to it. I've decided to bring a Nymph canoe and while I am at it I figured I would build two. Unfortunately, I only have one strongback. So, yesterday I decided to build another. A strongback should be rigid and straight.

Teaching Kayak Building

I spent the weekend up in Manchester, CT teaching the S&G Night Heron class at the Connecticut Valley School of Woodworking. The class will continue next weekend.

How much wood do I need to build the boat?

A stitch and glue boat will typically use three or four sheets of 4mm Occume marine plywood. With careful cutting you may be able to be more efficient.

Strips

For a strip-built kayak a good rule of thumb is 2 board feet of western red cedar or other softwood for each foot of boat length. A board foot is a volume of wood 12" long x 12" wide by a nominal 1" thickness. Most wood you will buy is planed down to 3/4" thick or even 11/16" for some cedar and redwood.

Why "Stitch-and-Glue"?

Because stitch-and-glue boat construction uses a relatively small number of wood pieces a boat can be build in relatively short order. Because plywood is inherently quite strong for its weight the resulting boat is quite tough and lightweight with a minimum of additional reinforcement.

While the technique quickly produces a boat, that does not imply that it is necessarily easier than strip-building. The shape of a stitch-and-glue boat is largely determined by the shapes of the plywood panels. If the panels are not accurately cut, the resulting boat may be quite badly distorted.

This makes stitch and glue designs very well suited for kits.

Why "Strip-Built"?

One of the biggest benefits to building a small boat with narrow strips is how accessible it is. While it looks intimidating, taking a bundle of small strips and wrapping them around a set of forms really is a matter of patience and not one of specialized skills. The tool requirement is minimal and the technique is very tolerant of mistakes. If you fail to make perfect joints between strips, the epoxy and fiberglass will fill them in and seal the mistakes.

If you are looking for a way to mass-produce wooden boats, strip-building is probably not the best choice. It is a time consuming method. More traditional methods of boat building tend to be quicker when performed by experience craftsmen, but that speed and ability to build a usable boat is largely dependent on the skill of the builder. The strength and water-tight integrity of the finished traditionally-built vessel is a result of the ability of the builder to make tight and sound joints. This takes skill and practice.

Which is easier, Strip Built or Stitch and Glue?

Building a kayak using either the strip-built or stitch-and-glue method is within the means of most people who want to do it. Neither method is particularly difficult for anyone who is willing to take the time required. Many first time builders who have never done anything remotely like a constructing a boat have produced beautiful boats they are justifiably proud of. Wanting to do it is the most important prerequisite.

"Ease" can be broken down into at least two factors: time and skill required. A strip-built boat will take more time, a similar design of a stitch-and-glue boat will require finer skills to get right. The differences are mostly in the woodworking parts of the projects. After the woodwork is done, the fiberglassing and finish work is pretty much the same. Because a "stripper" requires individually fitting many narrow strips together, you spend a lot of time doing woodworking. Once finished with the stripping, you must sand everything smooth. Neither the stripping nor the sanding are particularly hard. While a "poor" job of stripping may look a little ragged, but even if you end up with gaps between the strips, the fiberglass and epoxy will seal all but the biggest mistakes and the finished boat will work very well.