Frank Scalfano wrote:I hired a guy to recaulk my deck, and he has finished about half the deck, and has gone through a case of TDS. By the way, he has had to pull a few of the screws and is of the opinion that these are sheet metal screws and inappropriate for the application. I think they are from the original construction. I know that Bud recommends the stove head type screws, but my guy appears to be right about the threads and the lack of a shank on the screws. I know enough about screws to know that unless you over drill the hole through the teak, you would need a shanked screw to insure that the screws hold the boards firmly to the deck.
It is necessary to use self tapping screws (sometimes called sheet metal screws) to fasten into fiberglass. These were used throughout the construction of the Westsail boats, even on wood to wood and metal to wood fastening. We used a pan head screw (you call then stove head screws) because the edges of the screw will bite into the teak, but not spread it like a flat head screw with a taper on the underside would do. The flat head screws tend to start a crack around each hole, while the pan head screws will not.
It is also necessary to use a tapered drill bit with a countersink on it, so that the hole in the wood will be large enough so the sheet metal screw will bite into the fiberglass and pull the wood down to it. The countersink will make the hole necessary to cover the screw with a bung.
That is the reason you will find pan head self tapping screws on most of the Westsail boat construction.