Back in the second post in this series, I was thinking about how to translate the arc bottom of the original sailing canoe into something I could build in stitch and glue. Using the original linesplan, I’ve modeled several different version of the hull in Delftship that allow me to make some numerical comparisons between them. All I’ve changed in each case is the number of chines and the underwater shape–everything else is the same (with the exception of some small changes to the bow profile to accommodate an additional chine). The design waterline and draft of 4″ are as on the original plans, and all these hulls are shown in a full bow-on view.
Here’s the original arc-bottomed hull, which displaces .117 short tons, or 234 lbs.
Here’s the same hull with all of the arc taken out of the bottom sections so that there’s just a straight section from chine to keel. This results in a significantly lower displacement of only .075 tons, or 150 lbs. How much displacement do we want or need? Well, I’d say something at least equal to the original hull. I’m also keeping in mind the displacement of my hard-chine 16-30 hull, which is .133 tons, or 266 lbs. From my experience in building and sailing those boats, they float pretty much on their marks with a sailor of average weight, so there’s a good comparison for what displacement we should shoot for in a two-masted, decked 16′ sailing canoe built in stitch and glue. I don’t think 150 lbs is going to do it.
Here I’ve added another chine and pulled it down amidships to make a nearly flat bottom. I may have overdone it on the extra volume, though, because now our displacement is up to .139 tons, or 278 lbs. I’m not sure we need quite all of that.
If I introduce just a little deadrise into the midships sections, leaving the ends unchanged, the displacement decreases to .128 tons, or 256 lbs, which is pretty close to our 16-30 hull.
So far, so good. The next step is to add the deck and deck camber, put the bulkheads in the right places instead of just at a uniform 1′ interval and expand the individual hull panels. Then, I’ll buy some balsa wood and make a 1 1/2″ – 1′ model.
Until next time. . .
Playing With Boats 