: Paul you are really good in your clear minded scientific thinking and you
: make the best most beautiful graphics.

Thanks. Glad they can help illustrate my discussions.

: It easily explains why my friends
: and I capsized in our flat bottom boat. As the water rushed to the side,
: that side became a V bottom with water ballast and the most stable portion
: of the boat, for the boat but not for us humans.

As you'll also notice, not only did you have a v hull with uncontained watter for ballast, but the waterline beam shrank to somewhere between 1/3rd and 1/4 of what it was originally. If the boat was designed for a certain stability (pick your number for reference) when the beam at the waterline decreased all the math about stability went down, too. Roughly, a quarter the waterline, a quarter the stability numbers.

With a cylindrical hull the stability stays exactly the same regardless of the amount of tilt. Whatever is on the bottom just becomes your new keel line. Move your butt and sit on it and regain your equilibrium. Unfortunately, we put cockpit openings in our boats and so we can't build kayaks as pure cylinders. They'd be a heck of a fun thing for people who like to roll and roll and roll

Interesting to note that with the oval hull, as the boat tilts the puddle in the hull area widens, indicating a wider waterline beam, and in this case, more stable position.

: Thanks for taking the time to do this.

I do this as a hobby. If I was going to try and make a living doing this I'd have to charge a lot more and... Oh, wait, that was a different post about mixing hobbies with WORK.

PGJ