tjr818 wrote:Okay, this has got me wondering. If all the weigh is concentrated in the center of a boat the ends would be very light. Would not that make a boat more likely to "hobby-horse" than a boat with the weight concentrated equally nearer the forward and aft ends?
I am not a physicist nor a NA, but it seems that it would be easier for a wave to lift a lighter bow than a heavy one. But then when things do start moving there is that thing called momentum
Hmmm....
I found this explanation which seems to clarify it in layman's terms. It's the type of thing R. Perry always has a way of defining so anyone can comprehend. If I can find one of my NA books I'll provide a more refined definition.
"Hobbyhorsing is the tendency of a boat to pitch back and forth like a rocking or "hobby" horse. That is to say, to roll forward toward the bow along the longitudinal axis, then back toward the stern, repeating, with the horizontal axis as the pivot point. If "hobbyhorse" doesn't quite conjure the right image, think "seesaw".
The conditions that induce hobbyhorsing vary for different designs, but hobbyhorsing usually occurs in a certain amount of a seaway. Sometimes, it is not the seastate, but a motorboat wake that will induce hobbyhorsing.
To a certain extent, most boats will hobbyhorse somewhat in certain conditions. But some are more prone than others. Long overhangs at the bow and stern are one design feature that is often associated with excessive hobbyhorsing. Another is excessive weight concentration at the boat's extremities.
Hobbyhorsing can be a momentary condition, such as when a wake is encountered, or can be an ongoing issue in certain sea states during a passage. Abrupt hobbyhorsing can bring a boat to a stop -- such as when encountering a wake in light air.
But even moderate hobbyhorsing won't help boatspeed -- some energy that could be propelling the boat forward is instead partly expended in the pitching of the vessel or fighting it. In other words, the boat is rocking back and forth instead of simply moving forward, so some forward momentum is lost as the boat pitches back, on the return, toward the stern."