Hull Width and Rocker
by Shirley Kysilko, Building Director
A good reason to keep the hull width as per the plan you are working from is brought out in the question from Rick Luck in the January, 1998 HUT! He raises the issue of Mad River making two boats from the same mold and calling them different models. The difference between the two boats is not so much because the seats have been moved, but because the hull has been widened. Before your boat has its thwarts, set it on a flat surface so you can see the keel line in relation to the surface. Using a band clamp around the center of the boat or some clamped-in temporary thwarts, play with the width of the hull and see what happens. If you make the hull narrower, you force the ends of the boat down and there will be less rocker. Let the hull widen out, and you will see that the ends are pulled up off your flat surface, and the boat will have more rocker.
While I will not comment on the ethics of marketing boats as completely different models, I will say that the different rocker amounts you played with on your boat under construction would result in different performance in the finished hull. This is precisely what I did with the first two canoes I built. The first was a Bob Brown 12 1/2 ft Itty Bit with a fair amount of rocker. This boat is very maneuverable, turns on a dime, and is great for paddling small creeks. After paddling it for a while, I began to wonder how the boat would paddle with no rocker. So, I built a second boat on a modified version of the original forms and eliminated all rocker. I also changed some of the profile above the waterline, but the part that really matters is the hull in the water, and this second boat is radically different from the first. It is much more difficult to turn and, therefore, tracks much better and is more suited to bigger water. These two boats are known as "Itty Bit" and the "Front Porch." Many of you have paddled the pair and seen for yourselves that you can indeed build more than one hull on the same forms.
This is my last column as your Building Director. I have enjoyed getting to talk with a lot of you about boatbuilding and have learned a lot in the past three years. I want to especially thank some of the people who have so generously shared their time and expertise to help me with the job - Bob Brown, Al Gustaveson, Bruce Kunz, John Drigot, Betty Ketter, Kay Kruel, Ray Klebba, Al Torvi, Sam Ross, John Quaife for getting me into the job in the first place, and all the people who have called with their questions and suggestions. See you on the water!
