The AC75 feels like a big Airbus jumbo jet.

Ac75 upwind angle. So what educated opinion do you bring to the table. Its not the same as with a Moth which is loose and fast. V A square root V T cos 90 true wind angle 2 V T sin 90 true wind angle V B 2 β 90 arctan V T sin 90 true wind angle V B V T cos 90 true wind angle Sail power.

Upwind speeds in the Vampire are 17-20 knots on the AC75 30-40 knots. I presume that because of their speed the apparent wind was always forward and really they were always beating as we would know it. The visually diverting aspect of the AC75 is the foil each side which will serve alternately as a hydrofoil generating lift and as a lever producing righting moment.

Upwind the AC75 will need to build speed by coming off its optimal VMG upwind course for some time and may have to sail a reaching course to some degree Eventually speed will build and from a rig point of view while reaching sheets will be eased a little and come back on as the boat pops up. From 25 to 38 knots downwind. Lining two boats up beside each other and sailing as fast as possible but with both boats constrained to a straight-line either upwind or downwind for 10 minutes at a time.

In the catamarans for the last Americas cup I was amazed to see that in the details of the wind angles the difference in the downwind sail angle compared to the upwind angle was 4 or 5 degrees. On Thursday 19th November Emirates Team New Zealand were the last team to launch their second AC75 the boat on which the Kiwis will defend the 36th Americas Cup over the period March 6 to 21 2021Three weeks before the start of the Americas Cup World Series in Auckland Tip Shaft interviewed Martin Fischer co-design coordinator at Luna Rossa Challenge and Benjamin Muyl chief. This has nothing to do with VMG yet.

With few rudimentary calculations then and with out calling the design teams at Team New Zealand or Oracle I calculated that the apparent wind must be about 19 degrees on a downwind angle and about 16 degrees on upwind. It is clear from these equations that for small X the distinc-tion in strength and direction between true and apparent wind is weak but for large Xthe effect becomes significant and decreases with Xfor all angles. Your goal is to get the mast straight with 20 degrees of heel.

So when an AC75 is sailing upwind in 18 knots of breeze at a boatspeed of 40 knots the crew on deck will be experiencing 40 knots of wind over the decks plus a percentage of the true wind speed. You can notice the boat heeling to leeward as they enter the tack. The Protocol for this Americas Cup has forbidden us to sail more than one AC75 at a time.