Vampire at 27 knots

Good morning all,

 

A short missive on a slightly different subject from normal.  No kites involved ....but sailing on foils.  Those of you whom I've not cautght up with for a while won't know why I'm in England...but that may become clear over the next month...which culminates in Foiling Week at Lake Garda in Italy.

 

Some technical sailing stuff to come - which won't interest everyone.  The short version: Sailing at 27 knots in 10 knots of breeze is amazing. 

 

The longer version: 

 

The Vampire Project is nicely summed up by this video (https://www.youtube.com/watch?v=To2yjKkozZM).  I've corresponded and discussed foils with it's driver/financier/ideas man/helm, William Sunnucks, for a few years.  He invited me to go for a quick spin on the Solent on Saturday.  Goodness me....I saw the speedo hit 27 knots at one point and we estimated the wind speed at 10knots.  Astonishing sailing.  With a 21sqm main, 6sqm jib, and 21:1 main sheet system well loaded up, we weren't even on the trapeze when beating (at 17knots!).  When reaching William was mostly saying, "too much righting moment".  Bear in mind that the sail was still fully sheeted in - but I had to go to leeward of the boom to get the heel angle where William wanted it!  

 

About 5° heel to windward when beating and 10° to leeward when reaching.  The cant angle of the board is 25°.  So when beating the effective cant is about 30° and reaching about half that.  The objective is to get all the lateral lift from the horizontal (well, horizontal if it wasn't canted) wand controlled foil and have zero lift from the section intersecting the  water surface.

 

I'm glad I'd had an outing with AW on a conventionally rigged cat (ie with mast rather than kite) last weekend.  (AW: I think the traveler was only 2:1.)  It could have been very embarrassing otherwise.  Initially I was trimming the main way too coarsely - and bear in mind that a 21:1 purchase system means even a metre of easing, which was more than I was doing, would only drop the control length by 50mm!  After a few minutes I got that control finer so we kept foiling better.    Beating, the leeward hull is about a metre above the water and we aim to keep the windward hull just skimming above the water surface.  So easing too much can easily result in a big spray off the bow and loss of a lot of speed...I got in trouble from the skipper a couple of times!

 

When reaching, after a few false attempts at trimming, William convinced me to just keep sheeted on and he'd manage the heeling from the helm...so there's me, cowering under the boom holding on for dear life as we scream along and the skipper calmly moves the (steering) angles around to sit at optimum (heeling) angle.  Incredible.

 

Lessons for foiling kite boats?  Plenty...but I have to do lots of thinking about it.

 

Amsterdam this afternoon (kite boats and Peter Lynn kite HQ), Brittany on Thursday.

 

Ciao