- I meant to observe first that if there is increased area under the

waterline at this cross section then that at first would appear to

indicate more water being displaced. If more water is displaced then

the boat is being sunk not lifted as stated.

Sail heeling forces may account for the boat being pressed into the

water, and so the increased displacement. However the experiment

involved heeling the boat by shifting fishing weights athwartships

without dynamic sail forces, and so there seems need to explain how

the extra water came to be displaced when the total mass of the boat

remained constant.

Graeme

--- In bolger@yahoogroups.com, "graeme19121984" <graeme19121984@...>

wrote:>

graph

> Guy,

>

> at your "The Stiffness of an Advanced Sharpie" at

> http://faculty.valpo.edu/gvandegr/ there is this:

>

>

> "This axis of rotation ensures that the total area of this

> underwater section remains constant. Close inspection of the

> indicates that the rotation slightly increases the area under the

of

> waterline. Hence the rotation is accompanied by a slight lifting

> the boat, which becomes important only at large angle, I believe."

be

>

> What lifts the boat? How is it lifted if it remains the same mass?

> (disregarding any lifting component of the forces on any sail)

>

> I can imagine wider hull sections aft coming into play as they are

> immersed (more) with increasing heel, and so perhaps lifting this

> represented midships cross section. If this is the case then the

> data set gained from only this representative cross section would

> insufficient to construct a generally representative model.

>

> If this is not the case it would appear that, as the boat is not

> able to just arbitrarily "lift" by some unknown means, then the

> assumptions made from this represented cross section are somewhat

> erroneous and therefore any further calculations based on them are

> also going to be in error. My calculus skills are too rusty to

> comment on your derived equations, and the insights and intuitions

> gained, other than to raise the point that any initial error in

> assumptions may be compounded, perhaps more than trivially so.

>

>

> Graeme

> - Thanks for warning me about lathe. I would want to do any scarfing

myself. Regarding the enthusiasm problem, middle school kids can get

enthused about anything. I just have to verify that the middle school

is aware of the safety issues. Also, a novice amateur boatbuilder

might like the idea of an overbuilt dinghy. I didn't regret

overbuilding my Piccup Pram until I tried to lift it. Guy.

--- In bolger@yahoogroups.com, "derbyrm" <derbyrm@...> wrote:

>

> Careful on the lath. ...

> ... don't you first have to find someone who is as enthusiastic

about the idea as you are?

>