9½' Dinghy
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Design Number 230
1984 |
This design was done for a firm planning to rotomold the boats in plastic. Rotomolding is a specialized method of
construction. It involves the creation of a metal form of both the outside and inside shape of the boat. Inside
these forms are dumped pellets of the special plastic. The form is heated while it is being rotated in two axes
at the same time. The heat melts the plastic and it forms itself into the shape of the mold. Most of the boat
fenders we see, often made as net floats, are made this way.
I spent quite a lot of time thinking about how the mold was to be built of steel. I came to be increasingly concerned
about the work involved in trying to recreate the sweeping shapes of traditional lapstrake wooden plank layout in steel.
I felt it would be much too complex a project.
The result of this cogitation was to try the idea of making the laplines all straight lines on the body plan view.
This looked good on the drawings, and the work involved in building the molds should be considerably reduced. The
layout is much simpler, and the offsets are just given along the laps, as if they were diagonals.
The wooden lapstrake construction shown on the plans is a good way to build the boat. The simplified lap layout and
lofting will make fitting the planks much easier and thus quicker.
If a sailing version is desired, I'd use the rig and parts off the 9' Pacific Peapod design.
| Particulars: | Imperial | Metric |
|---|
| Length overall | 9'-6" | 2.90 m |
| Length datum waterline | 8'-3" | 2.51 m |
| Beam | 4'-6" | 1.37 m |
| Draft | 0'-7"/2'-6" | 0.18/0.76 m |
| Freeboard: | Forward | 1'-7" | 0.48 m |
| Least | 1'-0" | 0.30 m |
| Aft | 1'-2 3/8” | 0.36 m |
| Estimated structural weight | 90 lbs. | 41 kg. |
| Displacement, to DWL | 260 lbs. | 118 kg. |
| Displacement-length ratio | 207 | |
| Sail area | 58 sq. ft. | 5.39 m2 |
| Sail area-displacement ratio | 22.78 | |
| Prismatic coefficient | .586 | |
| Pounds per inch immersion | 110 | |
| Entrance half-angle | 29° | |
Note: The displacement numbers are calculated to the arbitrarily chosen DWL.
The calculated ratios of displacement-length and sail area-displacement will vary widely
depending on the loading of the vessel.
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