People frequently call and ask us to describe the basic differences between hard-chine and multi-chine (or "soft chine") kayaks. They are equally easy to build, although multi-chine boats take about 5 hours longer. Hard-chines originated in the aboriginal skin on frame designs of Greenland. They have one sharp angle (or chine) on each side of their hulls. Multi-chine or soft-chine kayaks hail from Alaskan and Canadian waters. They have multiple chines, with less acute angles. One major performance difference between them lies in their ability to execute leaned turns.

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Paddlers do leaned turns by leaning the boat outward on a turn. To turn right, lean left. The opposite from how you lean a bicycle. When upright, the keel of a kayak tends to keep it going straight. Lean a hard-chine kayak over far enough, and the chine will start to function as a keel. However, since the chine is curved, the boat starts to carve a turn. You get some benefit from leaning a multi-chine kayak while turning. In a hard-chine boat this effect is more pronounced and felt at a lower angle of heel (in other words, even when leaning less) than in a multi-chine boat.

I designed our hard-chine Arctic Tern kayak to directly compete with our multi-chine Osprey Standard and Coho models. Like the Osprey Standard and Coho, the Arctic Tern tracks well and does a fine job of running down wind in following seas. Paddlers experience all three kayaks as extremely easy to control and paddle without a rudder. They all make great boats for extended camping or day trips. The cruising speed and stability for all three are approximately the same. Of the three boats, the Arctic Tern carves the crispest turns and is the most maneuverable. The Osprey Standard tracks the strongest and runs down wind the easiest with the most stability. The Coho displays good maneuverability, the highest top speed, and the most storage capacity.

The Murrelet Series is a great example of how maneuverability and the ability to lean turn is not limited to the discussion of  hard chine vs. multi-chine.  While all the Murrelets are multi-chined boats, the version 1 tracks much stronger (comparable to the Osprey Std.) and does not turn as easily when leaned. Version 2 has much more keel rocker, turns well when leaned and is our most maneuverable touring boat by far.

My computer studies and research into the differences between hard-chine and multi-chine kayaks show that multi-chines are somewhat more efficient. For example, if the loaded waterline length (LWL), keel profile, and cumulative stability are held the same, a multi-chine boat will have about 3.2% less wetted surface and be about 3.2% faster at cruising speeds. They will have the same top speed, the same upright turning radius, and the same stability. The hard-chine boat will be a little slower at cruising speeds but will have a tighter leaned turn. If you hold the initial stability the same, the difference is more pronounced. The shape of the stability curves differ. The same cumulative stability to 25 degrees of heel will give you less initial stability and more secondary stability in a hard-chine hull compared to a round bottom hull. A designer can trade the efficiency of a multi-chine hull for more stability instead of more speed. If I hold the wetted surface, LWL, and keel profile constant, the boats will possess the same cruising speed, top speed, and upright turning radius, but the hard-chine boat will have less stability.

A skilled designer can design excellent craft in either category. In general, if the two designs are similar in other respects, multi-chine boats, with more efficient hulls can be either quicker or more stable. Folks looking for speed often pick a multi-chine hull. For paddlers who like the performance and feel of hard-chine boats they are the right choice. Last but not least, between boats of similar performance, paddlers often let aesthetic preferences finalize the decision.