New project: a smaller kayak
Having just completed a large kayak with ample storage space, it weighed in at sixty pounds, which is too much for my wife. But the basic design looks good, now I plan to create a slightly smaller version of the same exact design. Frames will be spaced at 13.5" instead of 15" and the depth is reduced by 2.5". I wonder how different the hull will be visually. Progress will be slow because of the holidays, tax prep, and a long-planned trip. Design dimensions are 153" by 26.6".
A hint of what is to come: The deck beams are laminated. They all have the same curvature; thus, they could all be built on the same form. The remaining parts of the frames are built from individual pieces that are half-lapped and then bonded together. The plank that all the frames are resting on will be the future keel. That keel will have a slight rocker by design. My strongback, such as it is, consists of a ten-foot long 2X6 resting on two sawhorses.
1) The offsets for all frames were mathematically calculated. The shape of the plank keel and the bow entry & stern were also calculated. The total length of the sheer and length at each frame connection, also calculated mathematically.
2) Full size drawings of frames, bow & stern, and keel ends were drawn. Most data points are only a few inches apart.
3) Individual pieces were constructed from those drawings. Midlines were marked on each frame for visual reference during assembly.
4) Given that three points define a plane, each frame can only fit in one position defined by the keel and port & starboard sheer connections. At bow and stern, additional rigid triangles are created by the bow, keel, and port & starboard sheer connections at the adjacent frames. This forces the port & starboard sheers to meet in a predetermined fixed relation.
5) With epoxy and plenty of clamps, all connections only fit in one position, allowing assembly without use of a strongback form. Planking can now proceed on this rigid underlying total frame.
Now I have started planking the hull. With natural wood, each plank has to be considered individually. Few are absolutely straight. None are the 14+ feet long needed; thus, each requires a scarf joint. I ran them all through a planer to get uniform thickness. The initial planks all are positioned in the 1st projection of the hull form, meaning they all lie in one plane and can be laid straight without any taper.
But this is a triple chine hull (four projections); at the turn of the bilge, angles change several times, and intersection of planes required that planks located at the turn of the bilge be tapered and less than full length. The taper was determined by clamping the future plank in place and then tracing the overlap from the inside of the hull as a guide for trimming.
No fasteners used; tomorrow I will bond this partial length plank in place with epoxy and plenty of clamps. Instead of spiling, I clamped the proposed new 1.5" wide plank in place and then traced (inside the hull) with a pencil the overlap between the new plank and previous plank. This guidance was then used to trim the new plank to its tapered form.
When you are laying multiple adjacent planks, you can't allow gaps due to this waviness. Thus, each plank needs to be fitted to its position, slowing the process.
posted by Wayne @ 6:28 PM
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