Jun 14, 2017

TNZ Capsize analyzed by Ken Read & Martin Fischer

Video source : America's Cup -
For us catsailors it doesn´t have much mystery as we've been there a few times. Baring away from a stopped position in 25 knots is about the hardest maneuver you can learn or experience.
Foiling cats have the advantage of reducing pitching and frontal capsizes as the main foil lift keeps your bow up.
In fact there is a wind range where sailing an A downwind you pitch or dig bow much less than an F18 for ie. Same with other foilers.
The F18 has a much broader and safer to sail and race wind range than any flying beachcat. You can sail in the breeze in other double handed foiler no problem too but chances you are going to start skimming or floating above say 20-25knots and high seas or chop.

Remember the AC45s floating mode at Plymouth in around 25-30knots of wind some years ago, I don´t think the AC50s would have survived that day in one piece: catsailingnews.com/2011/09/ac45s-full-throttle-at-plymouth-only.html

The other problem with foilers arise when you have a wrong rake setting or foils generates too much lift (without any inherit designed height control like the AC50s hard Ls foils as opposed to Z or Js) , There you can have disastrous consequences as seen in the video .  And that is exactly what Fischer comments,  telling Read to forget about the winglet.

It is not on the rudder losing grip causing the pitch by itself, but going high on the L foil, almost lifting out of the water, which makes for a perfect pivotal point at the mainfoil, for the rudder to come out along the stern pushed hard by the Wing power.
Frontal capsizes are originated when your cat rig overpowers and your platform cannot react at same pace.

This capsize from a stopped positions bareaway in 25knots happens on a floater and we don´t have any winglet, thus losing control on your foiler and goin high fly  it is just a classic catamaran frontal capsize on steroids.

No rudder winglet  setting would have avoid that pitch in that specific situation.  Only alternative was less mainfoil rake, but there you had the risk of a classic submarine floating mode capsize.

Ainslie and BAR got the right settings and the right turn ratio, but it was a high bet , their were also close on going down. Ben knew it beforehand on the risks as he warns the team to prepare for a hard barewaway.