. > >I am hoping to entice several of you more experienced paddlers to >'wax philosophical' on the pro's and con's of the Swede form boats. > Not much philosophy to it unfortunately :-) The issue has lots of complications but here goes. >From a wave making standpoint in smooth water it does not matter which form you use so long as the longitudinal center of buoyancy (LCB) lies within the appropriate range (roughly 48 to 55% aft of forward waterline ending. This surprises most people who look upon the waterline shape as cutting through the water and the water being pushed to the side. The water actually dives under the boat and travels roughly along the buttock lines. If you can get hold of Taylor's "Speed and Power of Ships" you can see some fascinating drawings of the water flow around a wide variety of hull forms. This problem with smooth versus rough water led to the debacle with the English America's Cup challenger Sceptre. They tested only in smooth water an the results looked great. Unfortunately they had to race in rough water where the finer American boat that had more resistance in smooth water won. The location of the LCB does make a difference aft where the fuller stern provides virtual lengthening and fills in the boundary layer aft. Like anything, you can carry this too far and cause separation drag aft (see above). Another difference has to due with performance in rough water. Finer ends with flared topsides have less energy loss than fish form boats and also tend to pitch less. One of the more interesting aspects of this has to do with "how" a boat has its form. For instance, some boats have swede form waterlines but the LCB still lies forward of amidships. The opposite can occur as well. Many people look at the waterline and say "fish form" when in reality the boat has a Swede form hull. Some of the Inuit Greeenlandic boats have this shape I.E. fine waterlines forward coupled with a full underbody forward. All very confusing but fun if you enjoy that kind of thing. The control aspects of form get even more complex. If one maintains the same generic shape and shifts the LCB fore and aft you get all kinds of wonderful results. Smart designers don't work that way. They treat the boat as a system where every part interacts with every other part. In this way you can often create a boat that "looks" all wrong according to the common wisdom but actually works quite nicely. I recommend that you not get caught up in the x VS y stuff. Usually the reputation of a boat tells you more than anything else. I hasten to add ETC. to all this. Whole books get written on just one or two aspects of this topic. I am sure Matt Brose will have some comments on this as might Nick Schade. Their opinions can help a lot as both have done a lot of paddling and study of boats. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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