Deadrise of multichine boats ?

[fcfc]

How it is mesured ?
For instance on a flat bottom double chine sailboat.

thanks.

[lewisboats]

If it has deadrise it isn't flat bottomed. Deadrise is the measure of the angle from keel to the first chine. 0 angle is flat, anything else is x degrees of deadrise.

Steve

[fcfc]

It is my problem.

For round hull, the deadrise is the angle beteen the keel and a virtual chine tangeant to 50 deg. So a rather flat bottom round hull may not have a zero deadrise.

Now for double hard chine flat bottom. a 10 ft beam boat may have a 2ft/ 3 ft wide bottom. and have the second plate 45 deg.

It is very different from a flat boat having a 10 ft wide flat bottom.

See http://users.win.be/ws200711/microch..._sections.html for what I mean.

Thanks for answering.

[lewisboats]

It's still a flat bottom boat, just that the flat part is rather narrow, so... no deadrise. Looks like you have a hard chine up front with a rounded bilge to the rear, to the point of having a little tumblehome. To have deadrise you need to start in the middle of the bottom (keel) and have a measurable angle to the first chine or to the bilge. Incline the first side panel as much as you like, but it is still inclination, not deadrise because it doesn't start at the keel. I have designed canoes where there is 8 degrees of deadrise, and the first side panel starts at 38 or so degrees. See picture. Only the Vee part in the bottom panel is considered to have deadrise, the rest are inclined panels. What is circled is the deadrise. If I made the bottom flat, then there would not be Any deadrise, but the panels would still have the same inclination (see the other picture).

Steve