Boat stability at the human scale

Boat stability is discussed here mostly through mathematical formulas and from an engineering perspective, but at the lowest end of boat size there are tiny lightweight vessels for one or two passengers, where stability is affected by the passengers' weight, and it is strongly related to ergonomics.
The W twin hull form keeps its lead in stability with this new 31" wide (79 cm), 80 lbs (36 kg) roto-molded kayak / canoe that doubles as a car-top boat / microskiff:



The paddler in this video is 6 ft tall (183 cm) and weighs 205 lbs (93 kg).

And let's not forget that not everyone is young and fit, and many people (especially in the US) are overweight and elderly, which means that they require more stable kayaks and small boats.

Here is a tall, 300 lbs (136 kg) elderly man testing the same boat / fishing kayak (the new Wavewalk 700) for the first time -



More about this design for kayak and very small boat stability >

 

Crew weight (movable ballast), and its effect on stability, can be calculated through engineering methods based on mathematical formulas.

 

I think we're playing with the language to talk without saying anything.
Assimilate the crew to a ballast may be admissible syntactically but conceptually not have anything to do both concepts.
".. engineering methods based on mathematical formulas." I do not know really what that means, but the phrase has a great scientific appearance.

 

Assume whatever is loose (unrestrained) can go to the worst possible position in the boat to compromise stability, and work from there. And the "worst possible position" can include people hanging on to overhead rails on small boats centre console T-canopies if the boat lurches into a broach......never liked that.