Cup Spy Nov 30 : Not a day for the faint hearted on the Gulf of Angels .. Is a Pole a Mast Tube?
by Richard Gladwell/Sail-world.com/nz 1 Dec 2022 17:43 PST
1 December 2022
Luna Rossa Prada Pirelli - LEQ12 - November 30, 2022 - Cagliari, Sardinia © Ugo Fonolla / America's Cup
What happened in the Cup - November 30, 2022:
- Luna Rossa sailed their LEQ12 on the Gulf of Cagliari, in their strongest breeze yet, and had a valuable, incident free session.
- American Magic stayed ashore in Pensacola
- INEOS Britannia stayed in the shed in Barcelona
- Alinghi Red Bull Racing went into the shed in Barcelona on November 16, for upgrades and is yet to emerge
- Emirates Team New Zealand are repairing their AC40/LEQ20 after a violent nosedive on November 21. There is no date announced when it will begin sailing.
- The measurement debate continues as to whether the Brit's Instrumentation Pole is in fact a Mast tube - they are only allowed one Mast tube on the LEQ12
Luna Rossa Prada Pirelli, the Italian America's Cup challenger say they had a "productive practice day" on Wednesday, sailing in their strongest wind yet in their LEQ12 prototype.
It was a day of two halves, with six crew aboard, and the #4 jib - their smallest - was used for the first time in the 17-20kts NW breeze, which greeted the team on their arrival on Golfo degli Angeli (the Gulf of Angels).
The afternoon was better as the breeze became more angelic and the sun appeared.
During the lunch-break the breeze stayed constant in direction, but dropped to 9-12kts, to which the team responded by changing up to their J2, and had two crew taken off the 12 metre long prototype - presumably to reduce weight. However the performance data from the half-size AC75, would have been more relevant with just half the crew allowed for the AC75. Even so, the recon team charged with pursuing Luna Rossa, reported that they struggled to keep pace with the flying LEQ12.
Vittorio Bissaro, Italian 2016 Olympic representative in the Nacra 17, was on board Luna Rossa and described the experience:
"It was my first time in this condition [20kts]. I really enjoyed the opportunity. We were out in the higher end of the wind range. The boat is pretty scary in that condition, because it's so fast, so nervous - it was shaking. "
Bissaro has two role on the LEQ12 - that of sail trimmer and flight controller.
When analysing relative boat performance in the AC75's or AC40's, it is very useful to know whether the flight control system is running on automatic to enable consistent performance data collection, or if the sailors are have it on manual for training purposes.
"The biggest difference between the autopilot and me is that so far, the autopilot is a lot better than a human. So it's a target for us to reach the autopilot's performance,' Bissario explained.
"The flight trimmer's role is basically try to level the boat and have a ride height that is constant through the water," he explained.
"For today, as an example - and the day before - we had the Mistral wind. A Mistral wind is normally is super flat here, and usually with some swell from outside, so today the sea was not that consistent. Keeping the ride height constant with these bumpy sea, is not always easy.
"So it's a very demanding role, and very important for performance. It is nice to try and beat the autopilot," he added.
Responding to a question as to whether Luna Rossa had reached the target for their performance in these wind conditions, Bissario said "as you can imagine, it is still an early stage, and early days for us with this boat."
"We are talking about performance, but always with a little of consideration for the fact that the boat has not been on the water for very long.
"But all in all, it was a very good day on the water. Sometimes we reach what we are expecting - sometimes we don't. But that means that we just have to investigate and try to do it on the next day".
Session Statistics - Cagliari - November 30, 2022 - Luna Rossa Prada Pirelli - LEQ12
- Wind Strength 9-11kts (AM) 16kts (PM)
- Wind Direction: N-NW (AM) NW (PM)
- Sea State: Slight (AM)
- Roll out: 0600hrs Dock Out: 0900hrs
- Dock In: 1430hrs Crane out: 1500hrs
- Total Tacks: 0 - Fully foiling: 0; Touch & Go: 0; Touch Down: 0
- Total Gybes: 2 - Fully foiling: 0; Touch & Go: 0; Touch Down: 1
Crew: Jimmy Spithill, Ruggero Tita, Vittorio Bissaro, Umberto Molineris, Andrea Tesei, Marco Gradoni
INEOS Britannia - LEQ12 - Mallorca
Off the water the Rules Roundabout picked up pace, as the teams and Rules Committee try to come to a conclusion as to whether an "Instrumentation Post" constitutes a "Mast Tube", and is therefore covered by the rule restricting teams to just one "Mast Tube" for their LEQ12's.
INEOS Britannia revealed what looked to be a very tall towing strut, which also bristled with instrumentation devices.
The penny never really dropped when we first saw the controversial Pole in the Recon File System. First thought was that the Brits were going over the top with their calibration.
Towing posts were used in the run up to the 2017 America's Cup, when a small spar/strut was strapped unto the mast step for the wingsailed catamaran. The strut was attached by stays to the hulls of the catamaran, and it was a safety measure to prevent excess hull wracking and damage during the towing trials, if something did not go according to plan.
Having gone to all the trouble of fitting the Instrumentation Pole, it was a little surprising to see the Brits tow testing the next day leaving their newly rigged spar ashore.
Part of the Rules Roundabout is its complete anonymity - so a team can ask for an interpretation, or give their response, without disclosing their design thinking to other teams.
All a team knows is what they have submitted - and the guess work begins on who has triggered the initial request, and the follow-on responses to the responses.
The purpose of the Instrumentation Post is clearly a way of getting around the ban on tank testing, and gives the ability to tank test in full scale.
It also enables the LEQ12 to have a sailing mode and a towing mode. In the latter mode heel can be induced in a measured and controlled way - as is done in real tank testing, The outcomes can be shown visually and also measured. The downside, of course, is that the test platform and foils are being towed in propwash from the chase boat - unless they tow at an angle, which starts getting awkward, with a chance of the platform being overturned.
The Brits are clearly pushing out the boundaries of precision testing, well beyond what has gone before - where previously a tow test on a foiler was just a means of checking for leaks, foil control systems operation and the like.
INEOS Britannia's approach is to very precisely calibrate their test platform - and effectively give it a double use - when sails are hoisted, or towed without sails to check foil performance and issues. The sail-less platform is probably the best way to attack the foilers problem of cavitation, which is the Sound Barrier of foiling and is speed inhibiting.
Find a solution that pushes out that boundary to a significant degree, and you've probably won the America's Cup.
The approach is not novel, Frank Bethwaite used to tow full size NS14's behind a small outboard boat on the sheltered reaches of Sydney Harbour - with a spring balance inserted into the tow rope. In that way he discovered the way different shaped hulls transitioned from displacement to planing, and devised hull shapes which flattened the "drag-hump", or allowed a boat to transition from displacement to planing mode with a minimum of energy.
Interestingly Bethwaite, a brilliant man, was quite dismissive of small scale testing. "We towed only real hulls, which were ballasted to real sailing weights. We never trusted models because such unpredictable things happen in the scale changes from model to full size."
His last projects - detailed in "High Performance Sailing" hinged around foiling - with 49er hulls - both in sailing mode, but also by attaching a long shaft outboard to the 49er. The controlled power of an engine erased many of the error factors, which it seems the Brits are well aware of - and are keen to avoid in their performance data collection.
Interestingly, in its draft interpretation, the Rules Committee opined that to fall within the "principal spar" requirement contained in the definition of a Mast Tube, "the towing post need only resemble one (or more) aspects of either the form or function of a mast tube".
It is very hard to see how a reasonable argument could be sustained that a round metal tube, a few metres long, with instruments strapped onto it, could be construed as the Principal Spar on a yacht which normally uses a D-Section carbon mast with double sail tracks down the aft edge to hoist the double skinned mainsail.