Stability Factor and Optimum Capacity

To help you interpret the table below
Our kayak plans are well tested, but each has its own unique characteristics. It is important before beginning your project to know what kind of kayak you will be paddling on launch day. We offer some science here to help with your decision. A table of stability and capacity values for the various canoes follows this explanation.

Stability Factor
We wanted to give our customers a reference for the stability of our boats. Our designer Steve Killing came up with the stability factor: the technical description is at the bottom of this page, but the real value is in comparing with other boats. Numbers range from about 70 to 120 - the larger the value, the greater the sideways stability. Many novice kayakers find boats below 95 to be just a bit skitterish, around 100 to be average and over 105 to be very stable. Your experience level will determine the stability you need. The Venture although it may appear low at 72 is for smaller people and because their percentage of body weight to boat weight is low and their center of gravity is low, the boat is comfortably stable.

Optimum Capacity
These capacities are the total weight of kayak plus contents that we know works well in the boat. The kayaks can be loaded more heavily, but their performance will begin to suffer. For example, the Endeavour 17 is listed at 150-260lbs. The 150 would be a small person in a 50 lb kayak on a solo day paddle. The boat also performs well with a large paddler (170lbs), plus pack (40lbs), plus kayak (50lbs). We know you can do the math.

These stability factors are calculated for solo kayaks at a common displacement of 250 lbs unless otherwise noted above. In the case of the True North this is slightly below the normal capacity, but provides a better comparison. The values are the metacentric height at 15 degrees of heel with 7.50" taken as 100 percent for kayaks

re: Stability
We were striving for an easy way for paddlers to compare the stability of various canoes and kayaks before they start building, or before they buy a canoe. I now use this for all canoes and kayaks that I design, including BlueWater and Bear Mountain designs.

No single number will tell the whole story, but I think this number has guided many people to the correct canoe and avoided big surprises on launch day.

The calculation is done on the computer defined shape. I load the canoe to 400 lbs for a tandem and 250 lbs for a single and then heel it to 15 degrees. The software maintains the correct displacement as the boat heels. Once in this attitude the stability is related to the distance from the center of gravity (which I set at the waterline for all canoes as a base point) and the metacenter. The metacenter is the point (usually about 12" above the waterline) where the vertical line through the center of buoyancy intersects the centerline. The higher it is the greater the stability.

The determination of the metacenter is not easy without a computer program and to do a physical test on an existing boat in the water is very difficult, so it is easiest to have the designer determine these numbers.

Once the metacenter at 15 degrees has been determined, the stability factor is simply the metacentric height in inches divided by 12.24 (for kayaks use 7.50) times 100.

A stability factor of 111 is comfortable for all novices - the Freedom 17'9

A stability of 100 is comfortable for most paddlers - the Bob Special is at 100

Some novices will feel a boat at 98 to be initially tender, but after a few paddles will be quite comfortable - the Freedom 17

The Huron Cruiser at 92 is not comfortable for most novices

Hiawatha at 88 is a challenging boat for some canoeists to paddle.

The marathon at 49 is well beyond my skill level.