Spectacular Blow Over at Key West Worlds!

[Jimboat]

I was asked some time ago, about "the forces that cause 2 tunnel hulls to flip simultaneously when the are too close together?"

Here's the explanation that I wrote up...

In general, if 2 tunnel boats are side by side, then they each start out on the edge of dynamic stability. If they get close enough together, their decks start to act as one large wide wing, instead of two smaller wings, with both boats experiencing an instantaneous increase in aerodynamic lift. This is because the higher aspect ratio wider wing is more efficient (larger Lift coefficient, CLa) than a low aspect ratio wing. This small add'l lift is enough to cause an instability of the boat. Even if the experienced increase in lift is relatively small, this added aerodynamic lift is applied forward of the boat's dynamic CG, causing a slight increase in angle of attack... which causes an increase in Lift... which causes an increase in angle of attack...which causes an increase in Lift... etc, and ultimately.... blowover. Also, if one boat following another then the following boat can see increased airflow also causing blow over.

Also, here's an article on blowover that explains some of the engineering behind it.