Dennis
It got the better of me and pruning the tress was not as interesting.
The sensitivity analysis showed less than 2% improvement by increasing the length. You can achieve an almost similar result by increasing the flare. If this is carried through to the stems then you get a reasonable increase in LWL as the hull is loaded.
This is my first attempt:
http://www.rickwill.bigpondhosting.com/DC9_ww_hull.fbm
You can extend sides upwards to a deckline. I have left the markers so you can see what I started with for 100kg. I would just keep the flare all the way up to the required deckline to reduce joints. It may end up a bit wider but this gives heaps of reserve buoyancy for a shorter hull than the lw hull. The bottom of the hull is only 7" wide so I do not think it will slam badly if you drop it. This is narrower than the bottom on my pedal boats.
Rick
--- In harryproa@yahoogroups.com.au, Dennis Cox <dec720@...> wrote:
>
> First goal - would be to use this weekend to start work on the leeward hull. I
> can more readily design during the week. I would appreciate a second set of
> eyes... particularily since you can hopefully point out where I can get some of
> that percentage back. I was real careful. Five doesn't seem that bad to me...
> IN FACT the major take way for me was to realize that this being such a cheap,
> flat, slab sided design is ONLY 5% off the most optimized design is surprising.
>
> Second - There is no way to put it nicely... my lake sailing here just plain
> sucks! I don't know how many times there's been predictions for 10 mph and I
> get out on my Hobie and get stranded several miles from the landing... shaking
> and baking in the sun as all the motor boats set up a general 2 foot chop. That
> was part of the reason for the heavier 360 kg initial numbers. To carry a
> battery and trolling motor.
>
>
> Third - As I see it, this boat has a far different mission than the big/cruise
> boat. Speed and testing is its only purpose. I guess that means that I was
> focusing more on shifting weight for various conditons to get the windward hull
> up out of the water. Therefore, I might be able to fly the windward hull in 5
> knots or 20 knots of wind with equal ease. My thoughts were:
> * Make the cross beams parallel and simple I beam construction.
> * Use the top flange as a track for the small deck.
> * Use a brake winch to position the deck.
> Windward Hull - I currently have a nearly rockerless windward hull penned for
> the 60 footer... long and skinny. However, your logic makes sense. If there is
> more rocker, it would tend to make the hull wider in the center... better
> interior room. More importantly... in conjunction with the rocker, it would
> funnel more water under the wider section creating more dynamic lift. Too bad
> we have no way of quantifying that. Next week, I'll scratch my head some more,
> I have been thinking of adding a dynamic lift to the Flotsam program. I was
> going to stay away from the wave theory version since Michlet, Godzilla and
> Flotilla have that in spades. I was simply thinking of a speed (momentum of
> water) striking the hull and doing the basic integration I'm doing for the
> static case now.
>
> But basically, I see the flat bottom with rocker as helping that.
>
> Any thoughts... anyone?
>
> Dennis