molds

Mold Construction ~ April 26-June 29, 2004

Jonah transfers the No. 7 Station line to a board

The molds are, as the name implies, temporary forms that define the shape of the hull. They are transverse sections through the hull at 3’ on center intervals. The shape for each mold is taken directly from the body plan on the lofting floor. The materal I am using is discarded pallet wood, kindly donated by my landlord and HomeDepot pine 2x4s for the spalls. I don’t know what kind of wood the pattlet boards are (I have sent a sample to the Forest Product Labratory for identification – they replied, but I could not read the wood pathologist’s handwriting, so the mystery remains!). The boards are narrower than the ideal (6″+/-) which translated into allot more work, as to form sharp curves I had to cut many short pieces and splice them together.

As we are building the hull upside down, as opposed to shear up as is traditional, I plan on placing the longitudinal ribbands inside the frames. Thus I subtracted both hull and frame thickness from the body plan lines (ribbands will be notched into the molds). This technique is not unusual in modern “cold molded” hulls, although even the venerable Howard Chapelle in his 1969 classic Boatbuilding outlines this method. For any given mold I transferred the body plan line onto a pallet board using specially fabricated “pointers” that provide a point to clamp a batten to raised 1” off the lofting floor (see picture at left).

Marking a board at station No. 9. Note that pointers hold batten at 1" off lofting floor.

Thus the bodyline would be transferred to a board. I would then screw another board to the first and cut both simultaneously on the band saw in order to produce a starboard and port sides of the mold. Each mold consisted of two overlapping layers of boards nailed together to a total thickness of 2”. The cross spalls were fastened at the 2′ and the -1′ waterlines. Both the upper and lower shear, load water line, center line and the buttucks lines were marked.

Early in the mold building process the family returned for a day, including my grandparents visting from Wisconsin, to inspect the mold building. My grandparents were visiting us that fatefull Christmas over 17 years ago when my mother gave my father plans to a 12′ catspaw dingy. My Dad and Granddad hit the basement after the presents where opened and began tearing up old bookshealves to build a strong back and molds. So they have been present at the start of evey boat we have built.