The Offshore Voyaging Reference Site

How Weight Affects Boat Performance and Motion Comfort

One of my first transits of the Cape Cod Canal in Massachusetts ended in an eye-opening experience when our small cruising boat was almost stopped by 2- to 4-foot wind-over-tide chop while exiting the west end into Buzzards Bay.

It wasn’t until years later that I realized why we had pitched so uncontrollably in such otherwise tame conditions:

Although the boat design wasn’t known for pitching, several adults in the cockpit made her very stern heavy, plus several modifications by the owner had greatly increased the pitch moment of inertia. Together, the improperly-distributed mass resulted in the boat pitching horribly.

Mass (weight¹), how much, and its location, affects the performance of all boats.  

The goal of this article is to help you think about where and how you add or remove mass from your boat so you can improve performance without resorting to racer extremes.  

¹Us lay people can for our purposes here, think of weight and mass as the same, although actually they are not. Eds.

We will examine mass, the moment due to the position of the mass, and finally the moment of inertia, which can all be additive to each other.

Mass (Weight) Alone

Let’s start by pretending that we add mass to the boat and can ignore where for now. This results in three important effects:

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