Thanks Northsea - I understand the physics (I'm an engineer). I think the excess heal was a little "showboating" by Alex, personally...while his outboard starboard foil is gone, he still has a rather long and efficient keel that only looses grip with the additional heal - regardless, it's definitely fun to watch.

How these boats have evolved is pretty impressive. They are effectively sailing on a side-edge hull profile not unlike a multihulls on one hull. Unlike a multihull, they maintain self-righting properties.

Thanks for that diagram. It looks like the foil is one piece from side to side? Is that right? In the updates I've seen from Alex he keeps talking about needing to get down there and saw off the jagged bits and I couldn't figure out why that was necessary...but if he needs that to retract into the hull in order to extend the other foil, I can see how that might be a problem.