> Actually, this gives me an idea. If you're doing your own design,
> and don't have the computational capabilities to asses volume required
> and achieved, you could buil the hull with extra freeboard, put it
> in a swimming pool or other calm water before attaching the deck,
> get in, and draw a curve where you want the sheerline to be.

> Better yet, load the hull with the amount of weight you will
> carry, plus your own weight, plus an estimated weight to account for
> the deck and outfitting stuff (seat, etc.). Now you can be outside
> the boat, so it'll be easy to trace the waterline, and sketch the
> sheerline along one side.

> Then, you can match the two sides, and cut the hull, and then
> add a deck to suit the hull.

> Quick, cheap, and dirty.

>

I think Archimedes beat you to this idea. Of course he discovered the concept in a bath tub, so while it may have been quick and cheap, odds are that he wasn't still dirty.

By the way, if you use water to partially sink your boat in your still pond and you carefully pump out the contents and measure them you will have a very accurate idea of the displacement of your boat. However, since there is no guarantee that the boat will sink evenly, or stay on an even keel when it is half full of water, (it should be designed that way, but if you are doing a freeform design this concept might get bypassed), you might have some difficulty determining the waterline if you use water to submerge the boat. Better to use solid weights, or at least put the water in some containers so it doesn't slosh around.

Most people don't have a lot of problems with this, despite the seeming mathematical complexity. After determining the rocker ( if any ) in the hull, they draw a straight line from bow to stern such that this line is horizontal when the rocker is right, and (on a kayak or canoe) about 4 inches from the deepest part of the bottom. They keep this line horizontal by moving the load fore or aft to level the boat. On a one person boat they reposition their seating arangement.

If the load is light the line is visible above the water, and on windy days the owner complains about the ``sail effect'' of the high bow.

If the load is great then the line is submerged and the owner complains about the sluggish performance and bottom scraping.

As I see it, the job isn't to design an accurate waterline mark, the job is to learn which complaints are appropriate for the wind and load conditions. I have reasons to believe this is the origin of ``Salty Language''

Paul Jacobson