## Geodesic Dinghy

An idea for a small code-guided boat I had dreamt up and put aside for a possible future recently found development opportunity with the coincidence of time, place, and tools to at least build a prototype.

As first conceptualized, the vessel’s intended function would be to transport needful things between the shore and a hypothetical larger live-aboard boat moored nearby or perhaps as far as a day and a half’s rowing distance away. More specifically, it would have to be capable of carrying a week’s supply of fresh water and groceries, laundry, garbage and sewage, a 20 lb. propane tank, camping gear, and a bicycle – or a passenger.

To design such a dinghy, the code’s transport template was drawn upon with heavy reliance on the hexagonal expansion (HXP) comprised of alternating triangular prism geometry.

Although such an application rendered the term geodesic inaccurate in relation it’s technical and popular (dome) meanings, the departure might be reconciled by viewing 2 lines of continuous sphere centers, around which the boat is structured with bode geometry on either side of the flat HXP “keel” – with those lines pointed in the direction of motion.

Because the boat would be operating in very shallow water over flat muddy bottoms, I decided to employ the template’s triangle down option with its relatively flattish (19°) chines. For overall size, a simple 8’ long by 4’ wide by 2’ high (at the highest point) was sought. An HXP seating structure draws upon bode geometry angles for bracing, is one foot high for stowage, and is broken up aft of the rowing seat for ease of boarding.

Because the contours of the triangle-down geometry dipped at bow and stern, the former will be covered to guard against splash, and the latter raised for passenger safety and comfort.

For the boat’s skeleton, I used 2×2’s and 2x3s, ripping them at angles that split the total dihedrals between intersecting planes (of which there were 5). In striving for economy of material and cuts, I tried to rip each piece in half for use on either side of the boat but neglected to account for the saw blade width which is significant at these scales.

This mistake, plus the lumber’s non-perfection, the old ripper’s lack of precision, and an inexperienced operator resulted in a lot of slop. Miraculously however, it all came together. Seated on the stern above is the monarch who has been overseeing the project from her bathroom window.

Much of the slop seemed to be absorbed by the rectangles which degenerated into parallelogram. This made jig sawing, ripping, and grinding the plywood sheathing – ½” for the bottom and 3/8” elsewhere – a laborious process, but again it all came together with 1” deck screws. Seams varied from zero to ¼” gaps and were filled with fiberglass resin before laying 4” wide matting into swaths of same. It is inspected below by the old salt who is my technical advisor.

Thus are the critical phases of the project essentially completed. Painting, specialized hardware, and details remain. The next post will recount these along with initial testing to determine if the dinghy actually floats, rows, and bears loads. So far, the project has taken 3 times longer than originally estimated. Because I give myself B+ for design and a D- for craftsmanship, how well the boat will actually do is a mystery at this juncture.

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