Building a Perfect Kayak: Part Three

If you remember from the previous article, I had just figured out a way to output forms from Hulls by using an extra chine above the design of the kayak. This extra chine gave me a common point in all the forms, and with the click of two buttons provided me with perfectly aligned offsets to plot on paper (albeit paper which looks like a brown paper bag, because I’m unable to buy white roll or tracing paper in Grand Marais, MN. I can’t wait to see my wood choices or maybe wood choice. Pine looks okay, right?) After I figured this out, I charted the Righting/Heeling Moments for the boat using a built in feature of the Hulls program. Finally, because it was nagging at my mind, I pulled out my old copy of John Winter’s, The Shape of the Canoe, and loaded the KAPER spreadsheet into excel.

The Final Countdown

Over the next couple of hours, using the measurements from Hulls, a good old fashion ruler and T-square, I figured out the LWL, EWL, BWL, H, Cp, LCB, LOA, BOA, Cx, and the Cb of my craft. I entered the numbers into KAPER and was pleasantly surprised. The Speed vs. Resistance charts compares very favorably to the kayaks that I’ve always liked, the Romany Explorer, the Chatham 16. It also compared well to my old Dagger Magellan, the boat that started my love for kayaking. So, I feel much more strongly, that this will be a good boat to paddle, but will it be a perfect boat…

Here are the final statistics calculated at 294 pounds. That’s a load of 250 plus my estimate that the weight of the kayak will be 44 pounds when finished (Am I dreaming?)

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Statistics

• Length Overall———–17′
• Beam——————–21.25
• Volume——————10 cu. ft. (estimate using Hulls. Not sure if correct. This seems small for the whole kayak.)
• Cockpit coaming height
• Forward—————–11.5″ to 12.5″
• Back———————7.75″
• Estimated Seat Height—-1″
• Estimated Weight——–44 lbs.

Hydrostatics

• Waterline length———14′ 10.92″
• Waterline beam———19.94″
• Draft——————–5″
• Prismatic coefficient—–0.54
• Wetted surface in sq ft–20.06
• Center of buoyancy—–53%

Speed vs. Resistance
Resistance in pounds
Speed KAPER/Winters

• 2 knots—–0.88
• 3 knots—–1.83
• 4 knots—–3.51
• 4.5 knots—5.08
• 5 knots—–7.76
• 6 knots—–12.5

The Kayak Design Work is Finished

With the numbers entered into KAPER, and my mind eased slightly more, I started to page through other back issues of Sea Kayaker looking at some other kayaks to see how my numbers compared. They actually came in slightly less than most of those reviewed, and I’m not exactly sure why. I doubled checked my measurements and calculations, ran it through KAPER a second time and it seemed that everything is okay, and maybe too good. Hopefully, not too good to be true, but I have to keep in mind that this kayak is narrower than most kayaks, and slightly less volume, or, at least, I told myself. And if you recall in the last episode, I wrote that my kayak’s lines looked like those off of the Aquanaut. Well, after looking at other boats, it sort of looks like every other kayak that I like and not just like the Aquanaut. My mind is mush from all this design — time to get to the lumberyard. It’s now a struggle for material and not design. Will they have anything other than spruce and pine? I’ve seen some nice white cedar up on the Gunflint. Hacksaw, anyone?