Builders' Forum Archives
Re: Butt Joins
Posted by Laszlo on May 25, 2004
Joint methods should be done as specified by the designer. In particular, unless you know what you're doing with designing fiberglass laminations, you should not replace scarfs with taped butt joints. There just isn't enough bonding surface, so the tape must provide a lot of the structural strength. Unless you use the right combination of glass weight, fiber orientation and number of layers, you'll get very wet.
You're actually much safer substituting butt plates, but those have their own problems. The main one is that they can change the shape of the hull. You end up with a locally thicker piece of hull which resists bending more than the rest of the hull. Besides deforming the hull from its intended shape, this can act as a local stress concentrator.
Boats which were designed for taped butt joints have a guaranteed lamination schedule provided by the designer. Boats that were designed for butt plates have a curve that is not bothered by the extra hull thickness at the joint. These boats were designed to be scarfed, so I'd go with the scarf.
It's not that big a deal with a little practice, so just practice on some Home Depot wood until you get good at it.
Or buy the precut kit and all you'll need to do is glue the scarfs together.
In Response to: Butt Joins by David Wallace on May 25, 2004