I think there are downsides that
haven't been brought up. For example the cabin sole being the
hull bottom is normally going to be narrower than it would be if
raised a bit.... Case in point the boat that I was originally
looking at, Kohler's KD 860 is flat bottom, but the sole is raised
per the image below:
The other concern I have is the
lack of stiffness of a flat surface versus one that is curved in
at least one axis. That means that means more reinforcing or
heavier material, or both. With foam sandwich, thicker core of
course accomplishes this with almost no additional weight... In
ply construction it's a different story, and an overall weight
savings over the rounded bottom may be a realistic expectation.
The shallower draft offered by a
flat bottom may offer an additional asset on a multihull with
daggers or Rob's fore and aft rudders in that it should skate
sideways more easily with the boards up offering less resistance
in storm conditions. Without heeling as a "safety valve", the
ability to move in response to a gust is said to be important. A
monohull with it's huge keel has to stand and take a beating like
a big heavy boxer, while a multihull can dance away and give to
blows, either accelerating or skating sideways. Lightness and a
shallow bite into the surface of the sea should be an asset.
Regarding performance differences,
I think we are looking at what in real life are pretty trivial
differences. There is far more to be gained I think from light
weight construction and from keeping payload down than from the
difference between flat and round bottoms. There is also the
possibility of surfing with a flat bottom, more so than a rounded
one.
H.W.
Thanks Rick, good info.
So from a performance only perspective.
Upwind, lower overall height reduces wind resistance
Light air, weight savings reduces wetted surface overall
as opposed to somewhat higher wetter surface of the
section...
You mention that a three panel optimized will be shorter
than a half round... wouldn't this knock some points off
the top end?
I can see some weight saving from floors and lower
structure but a shorter hull runs counter to overall
performance. Maybe I'm missing somethin.