July 19, 2016

The boats that chuckle

A MESSAGE from Frank, in Columbus, Ohio, says:

“Dear John: You once wrote a column about lapstrake planking. I was recently visiting in New England and saw lots of lapstrake wooden boats. What’s the advantage?”

Well Frank, the first thing is that it’s beautiful. If you like looking at pretty girls, you’ll like looking at lapstrake. It emphasizes all the curves. That’s not actually why boats were built with overlapping planks, or strakes, in the first place, though.

Because each plank overlaps the one below it, the thickness is almost doubled along each edge. That makes it very stiff and strong — suitable for one-design racing dinghies, smallish fishing boats landing on beaches, or ship’s launches that take a good pounding. And because it’s so strong, a lapstrake (or clinker-built) hull is normally much lighter than its carvel-planked cousin.

But building in lapstrake is a fine art, and mostly a lost one these days except in a few wooden-boat centers scattered around the country. In the old days the planks had to be finished so finely that they would not leak even in the absence of caulking. These days, a fine bead of polyurethane or polysulphide makes it easier to form a watertight seal along the plank edges but formerly it was the skill of the boatwright alone that kept the water out.

The planking always starts at the keel and works its way upwards. Copper nails with rooves fasten the planks together with a minimum overlap of about 5/8 inch with 1/4-inch planks — and more on bigger boats, of course. At the stem and transom, where the planks come together, the strakes need expert treatment and call for fine woodworking skills.

Older wooden boats without caulking would open cracks along the seams if they dried out for too long, but if they were allowed to soak in water again for a couple of days, the wood would swell and cure that problem.

There isn’t much lapstrake construction around these days, of course, at least not in commercial production, but when fiberglass took over from wood some 60 years or more ago some boatbuilders thought it might be a good idea to produce lapstrake GRP boats.

The problem is that fiberglass doesn’t like to make sudden sharp bends, and lapstrake is ALL sharp bends between one plank and the next if you run your hand down the side of the hull from top to bottom. So they had to fillet the joints between planks into nice gentle curves, which took more material and added weight — and that, in turn, negated the light-weight advantage of lapstrake hulls. I expect the construction of a lapstrake mould was also much more difficult and expensive than a plain carvel one. The net result was that a fiberglass lapstrake hull was strong and pretty and more maintenance-free, but often impractical from the point of view of construction and cost.

One-off wooden racing boats are rarely built in lapstrake, despite the weight advantage, because of the added resistance of each lap at slow speeds and because the greater surface area of the hull results in more drag.

One thing that surprises people who have never owned a lapstrake boat is how much noise they make at anchor. Each little passing wavelet smacks into the underside of the laps with great zest, resulting in an unexpectedly loud chorus of noise that owners of lapstrake boats are wont to dismiss as cheerful “chuckles.” But let me tell you, Frank, that if you’re anchored nearby, in the middle of an otherwise quiet night, you might not be chuckling so much.  

Today’s Thought
This sort of thing takes a deal of training.
— W. S. Gilbert, Ruddigore

A newly released government report reveals why universities are often referred to as “storehouses of knowledge.”
“It is simply that undergraduates bring so much knowledge in,” says the report, “and graduates take so little out.”

1 comment:

57 Degrees North said...

Beaching indeed! You neglected to mention the other use those fair-haired gentlemen from the North made of their fast and shallow-drafted lapstrake ships. When you are finished committing wholesale murder and lifting any valuables that aren't nailed down, including (most likely) the nails, it helps to be able to get your transportation back in the water in a timely fashion...

NorSea Yachts claims that it takes about forty percent more time to lay up one of their 27 footers than it would the same hull in a smooth configuration. That's pretty significant.

And I for one, like the sound of a chuckling lapstrake hull... Even if they are anchored near me! One of my early unrequited loves was a GRP folkboat. Even tied to the dock she sounded active and lively. As such things do, it marked me for life...