This was the concept video form last year, but early October this year Sir Ben Ainslie and his team launched the new AC75 prototype. For the 36th America's Cup race to be held in New Zealand in March 2021 the rules have changed again. Instead of foiling catamarans which were pretty quick, they will be foiling mono hulled beasts of 75ft.
Insane facts....
The average mono hull yacht can sail at around 40 - 60% of the true wind speed but a catamaran can achieve up to 70-80% when beating or reaching, downwind is slightly different and then controlled by the possible hull design speed. Foiling dinghy's and yachts work on the same principal as sand and ice yachts which, yes this is fact, have been recorded up to 100mph and 9 times the speed of the wind. Initially America's cup Catamarans were expected to achieve 120% of true wind speed and 160% downwind, however, get this, they have been recorded at up to 280% of true wind speed with a top end of 47knts.
These new AC75 foiling mono hulls are expected to hit the magic 50knts and that's faster than one or two sports boats I know.
I expect some of you already know this, but if not, these speeds are achieved because of something we have all experienced at some time in our lives but not really thought about much, apparent wind. In the lower picture on our front page is Shibbs boat doing about 25kts (at a guess). There is a breeze blowing which may be coming from his 2 o'clock on his starboard side at 5knts, however when at rest his hair is not being blown but at planning speeds it is, quite a lot. The wind direction has now shifted to almost straight ahead and the wind speed is way more that 5kts and approaching 30knts, this is the apparent wind speed and direction. The faster he goes the greater the apparent wind and the more his hair will blow around. If he had sails he would be limited by his hull speed but out of the water with not much drag his boat would sail near to the true wind speed. With added technology and aerodynamics the sails would have a greater low pressure are on the lea or downwind side of the sail, the faster he went the higher the apparent wind speed. This lower pressure propels the boat faster until it couldn't achieve any more speed because of drag or dynamic limitations.
If you have the time, look up the calculations and theory behind it all, I usually get bored after the first sentence, but watching these boys and girls winding the hydraulic line adjusters at full chat and seeing a fast rib or support boat trying to keep up is truly amazing.
