serene – 1, part 4

inalized my new kayak design, a considerable amount of work on optimizing the hull shape, adjusting it back and forth to find out the minimum drag numbers (based on the Kaper algorithm) while keeping stabilities and other parameters under control. Some numbers: LOA / LWL (length overall / waterline): 5.500 / 4.945 m, BOA / BWL (beam overall / waterline): 0.452 / 0.420 m. I reduced the boat width to exactly my hip plus 4 fingers (that is: 36 + 9 cm, my fingers are quite big, 9 cm for 4 fingers).

Designed draft: 0.11 m, Designed displacement: 95 kg, Cp (prismatic coefficient): 0.5475, Cb (block coefficient): 0.4064, LCB (longitudinal center of buoyancy): 0.5225, VCB (vertical center of buoyancy): 0.0690 m, LCF (longitudinal center of floatation): 0.5136, Cw (waterplane coefficient): 0.6445, S (wetted surface area): 1.699 m2, Aw (waterplane area): 1.329 m2, Am (midship section area): 0.034 m2, Cm (midship coefficient): 0.7466, KMt (vertical transverse metacenter): 0.196 m.

Predicted drags at 0.11 m draft (95 kg of displacement): 3 knot ~ 7.122 N, 4 knot ~ 12.622 N, 5 knot ~ 23.763 N. Predicted drags at 0.121 m draft (110 kg of displacement): 3 knot ~ 7.679 N, 4 knot ~ 13.611 N, 5 knot ~ 25.506 N. The hull is heavily optimized for speed in the [4 ~ 5] knot range with some sacrifices in stability and load capacity. Now that all “theoretical calculations” has completed, it would take a few months to build the physical boat to tell the real truths about the design! 😀

Serene – 1, part 1
Serene – 1, part 2
Serene – 1, part 3
Serene – 1, part 4

While 45 cm could be considered “extreme” for nowadays kayak (few available on the market has width at or below that value), it’s not really so with the traditional Greenland ones, some could be as narrow as 39 cm. Well for sure, it requires lots of skills to handle such a narrow boat.

The very important point here is the CG (Center of Gravity) used in calculating stability. The Sea Kayaker magazine uses a standard 25.4 cm as CG, as a reference point to compare different kayaks. I used the midpoint of VCB and KMt as CG, which is usually [12 ~ 14] cm for my cases.

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