Join Date: Feb 2000
Location: Annapolis, Md
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The term ''Tumblehome'' is quite an old term. I believe that I have seen reference to the term in late 19th century descriptions of vessels. The term is probably a lot older than that even. The term refers to feature of a boat design where the topsides (between the waterline and the deck) at the deck is narrower than the topsides lower on the hull.
The source of the term is pretty much self evident as the topsides ''tumble'' in toward the deck.
The use of tumblehome came into being for one of three reasons. The earliest form of tumblehome appears on multidecked warships as a way to move the heavy weight of cannons and ball in towards the center line of the ship as their tophamper weight was being located higher in the air.
When tumblehome occurs on non military vessels and somewhere near amidships it generally came into being as a way of cheating a measurement rule (either taxation or racing) where the measurements are taken at the deck or at some arbitrary point on the topsides.
The Third reason for having tumblehome usually occurs near the transom and are typically assocated with elliptical transoms. In the days when the boom often hung well past the transom and the sheets were often run to boomkins, the tumblehome at the transom kept lines from fouling on the corners of the transom.
When you see tumblehome in a boat today it is generally a stylistic thing trying to harken back to some other era. From a yacht design standpoint, the traditional forms of tumblehome do nothing good for a boat.
That said some modern race boats have taken to radiusing the deck near the rail as a way of reducing drag when rail down, increasing the limit of positive stability, and reducing weight aloft and outboard.
One last point, I don''t know that I have ever seen the term ''tumblehome stern''. I would think that the proper syntax would be ''tumblehome at the stern'' as in ''she displacyed a lot of tumblehome at her stern''.