Builders' Forum Archives
Posted by CLC on Feb 17, 2005
Boat designers have practiced upon the public since the 19th century, claiming that big chined boats are automatically easy to build. In reality, you can make a chined boat harder to build than a fully rounded shape, by requiring a lot of twist in the panels, or an arc-bottom as in the Lightning or Penguin. (You can get away with murder in terms of twisting the thin plywood used in kayaks, but try that with 3/8" plywood...) To get all that shape you have wrap the stiff plywood around a rigid mold.
Snipe-like or Lightning-like shapes can be made to form up using stitch-and-glue methods, but with great variability in the finished shape. That's the nature of stitch-and-glue, and it's also the reason that those classes don't allow stitch-and-glue methods. They want every boat to be identical to within millimeters so that no one has a hull shape advantage on the race course. People who aren't racing don't need to sweat that, and for them there are hundreds of designs that aren't sensitive to tolerances.
The Optimist Pram was always supposed to be a build-it-yourself boat. These days they are raced with a competitive fervor that defies belief. In huge, highly competitive fleets, an Opti with 6mm more rocker in the bottom panel is going to walk away from the others in light air. Thus the Optimist Class has essentially shut down home-building of Optis. If the tolerances were loosened to allow for the innocent variation you'd get from a lot of amateur-built boats, then the pro builders would take advantage of the tolerances to build faster boats.
The Windmill Class is still active and encourages home building, with wooden hulls racing alongside fiberglass hulls. Their tolerances are about 1/2". There has been some experimentation with stitch-and-glue amongst the Windmills, but ironically you still need a fairly elaborate mold or you'll definitely miss tolerance at some spot on the hull. Kind of defeats the purpose of stitch-and-glue, which is to eliminate the mold. I built three Windmills the old fashioned way, plywood-on-frame, over a complex and carefully toleranced mold.
In Response to: Re: sailboats by Mark Camp on Feb 17, 2005