When winds are light to medium you want to present the maximum amount of sail area to the wind, but in heavier air, the closer the wind can be to 90° angle as it flows off the leech, the more efficient the sail is going to be. (well that was the theory when I was sailing full size Tornardos, many moons ago) Can see this on ice boats where there is dramatic performance difference depending on the angle the iceboat makes to the wind. I suspect the rake on AC 72's also helps the upper part of the Jib twist off & free's the leech at high wind speeds as rake has the same effect on the Jib as moving the clew further aft.
Wolfgang - FYI - the reason for the Hobie 16 to have so much mast rake is that the hulls do not have daggerboards, and thus their flat hull sides and rudders are their only lateral resistance. By having mast rake, the rudders get "loaded" up with pressure/lateral resistance which helps with ability to point higher going to windward. Without rudder load, the boat would struggle to sail to windward. On the other hand, the Hobie 18 does have boards, so extreme mast rake is not required, allowing for a more neutral helm. Dick
The theory is that the more the leech area is perpendicular to the air flow, the better the performance. One reference was ice boat record of 130 knots (240 km/h; 150 mph), Dick would know more about this as he lives near hard water most of the year Rig design/placement (C.L.R/C.E) would interesting as none of these boats use hull displacement when sailing.
Thanks Alan, now I understand. Is this part of the thinking behind the Delta Rig, such as Claudio has posted on?
Yes it was part of the Claudio's Delta project, he also wanted to reduce turbulence coming off the mast, I was going to try it on AC 120 as it proved to be a real flyer in light air however, I realised it was possibly limited to light air as soon as it got into higher wind speeds the high tension required on the forestay to stop sagging was really beyond my capability to build such a rig 1.7 meters tall. Great concept all the same that works very on smaller boats. http://www.rcsailing.net/forum1/showthread.php?5471-Delta-rig&highlight=Delta+rig
AC Espionage 30 Android mobile devices on board OMG Larry can monitor each crew members performance from his office, in real time :slaphappy
tried this, but didn't have enough wind ;-) (an early pic with my C-Rig, got now a jib closer to the bows and much more rake and two arm-winches) @Dick you're completely right! With smaler Rc-Multihulls, you are very often at a 'lot too much sail' mode. At a big cat a change from 3 Bft to 5 Bft gets you into a 'yippie' mode, at a RC-Cat you are struggling in a survival mode. So with a RC-Cat I have to control the rig in a different way as seen on RC-Monohulls. Every mistake at a RC-Cat leeds into a capsize, at a monohull you get wet sails and you move on. On hight winds a capsize on a close haul comes often with a slow winch or not enough practice. Tacking at the windward gate and bearing away to a broad reaching you are often close to a pitch pole, as you know. At that point I often could not bear away without a pitch pole. Last year I took one winch for the main and a second one for the jib, to go better thru a tack. This helped a lot. But it also helps to bear away with a luffing main and a jib under full load. Coming back to that picture with that 18 footer, I hope to get a (small) amount of lift by the sails (remember, you are in a survival mode on your RC-Cat, at low winds I leave the cat at home ;-). Wolfgang
lots of money involved. hope L.E. goes thru the Luis Vuiton Cup without too much lost money: http://www.vsail.info/2013/06/18/americas-cup-one-step-forward-five-steps-back/
Well LE came up with the recipe & now he has to eat the goose ... With debate raging about changing the rules Paul Cayard gave statement (Tom FitzGerald San Francisco Chronicle) Less than two weeks before the challengers series begins in the America's Cup, the regatta's rules are unsettled as the four teams haggle over things like the maximum allowable wind speed for the races. Regardless of how the dispute plays out, at least one key player is very unhappy that organizers missed a chance to have "the best America's Cup ever." Paul Cayard, a San Francisco native who is CEO of the Swedish team Artemis Racing, said Friday that the 72-foot catamarans being used are too big, too powerful and too dangerous. "San Francisco is one of the windiest venues in the world," he said. "But that's a good thing if you've got the right tool for it. It's a horrible thing if you've got the wrong tool. Right now we've got the wrong tool. We've got a boat that's made for San Diego (where the winds are much lighter), and we're trying to race it in San Francisco." Cayard is especially peeved at the decision to use a 38-meter (or 131-foot) wing rather than the 32-meter wing that was part of the original class rule, he said. The rules were established three years ago by Larry Ellison's Oracle Team Racing, the defender, and the Italian club Nautico di Roma, then the challenger of record. Nautico di Roma pulled out of the 2013 competition two years ago. So the rules were already set when the Swedish club that sponsors Artemis took over as the challenger of record. Originally it was planned that the big catamarans would race in Europe as well as the U.S., with the 38-meter wing only being used in places like Venice that have light winds, Cayard said. Those plans were scrapped because of the prohibitive costs of shipping the big boats. The decision to stick with the larger wing in San Francisco's powerful winds might have contributed to the Artemis capsizing (in 10-15 knots of wind) on May 9 that killed British sailor Andrew "Bart" Simpson."Accidents would have been less likely with the 32," Cayard said. If the Cup had simply used the 45-foot boats that sailed the last two years in the America's Cup World Series, Cayard said, the reduced costs would have enabled probably a dozen teams to mount challenges. "Typically, we have eight and as many as 13 challengers in the America's Cups I've been in," he said. Artemis' AC72 is built for San Diego conditions, not choppy, windy San Francisco Bay, says Paul Cayard. As Artemis tries to come back from the tragic wreckage, work is still being done on the frame of the new wing at the team's headquarters in what used to be a warehouse in Alameda. Cayard may be hoping to buy more time to get his second boat operational; right now, team officials hope it is sailing by the end of July, but Artemis may have to skip the opening round-robin of the Louis Vuitton Cup series altogether. Two members of the America's Cup international jury have so far been unsuccessful as mediators in getting the three challengers and Oracle on the same page. They have been working with a list of safety changes recommended by regatta director Iain Murray in the wake of the Artemis accident. Talks are scheduled to continue Saturday. If an agreement can't be reached, the full five-member jury will decide the case. It would begin hearing arguments Monday morning. Among the key sticking points is the recommendation that the maximum allowable wind speed for racing be lowered from 33 knots to 23 in the America's Cup finals and from 25 in the Louis Vuitton Cup challenger series to 20 in July and 21 in August. Emirates Team New Zealand is arguing for a higher speed limit, Cayard said. "They think their boat was built for the high wind speeds, so they want to make everybody race in high wind speeds, even if it's unsafe," he said. Grant Dalton, CEO of the New Zealand team, said in a statement issued by the team, "It is true that our boat was designed for the higher wind speed published in the rule in October 2010. This upper limit has been reduced by 30 percent, and Emirates Team New Zealand has gone along with this - to its own detriment - in the interests of the event. "The Artemis incident was tragic, but if Cayard feels that Artemis cannot comply with the significantly reduced wind speed, they should withdraw from the event." I tend to agree with GD comment ...what do you think ? and P.C press statement has got to be one of worst on record ... this goon has lost his marbles !!!
I think the quote actually referred to the class rules, not the Artemis design per se. It's pretty clear that this event was not well thought out, and has resulted in boats that are risky for the venue. They may be fine in other locations, but SF Bay is not a friendly body of water. Once foiling became a reality the issues of speed and control in tight spaces became critical. Besides technical failure and the possibility of hitting a floating object (the Corps of Engineers pulls 1200 *tons* of junk out of the Bay per year) we've had a helmsman go overboard on an AC boat for the first time since 1901. The sight of those crews scrambling from hull to hull in practice, much less the adrenaline-filled environment of a race for the Cup, doesn't exactly fill me with confidence. A high-speed collision at the windward gate during ebb tide conditions would present almost insuperable problems for any rescue team: visualize a tangled raft of netting, mylar, carbon fiber fragments and injured humanity in cold, murky water, all heading for the open sea at 4 kt or so. The principal preventative measure at this time appears to be prayer. Earl
So when did the venue change? I always thought it was in San Fran from the start .... mainly for easier public and media viewing - plus the waterfront updates?
There was “debate” 3 years ago of alternative venue to SF but was only talk. Personally I believe P.C rant is possibly the beginning of Artemis end of this AC, he is now lining up all his excuses as they have left it too late to test the boat (design integrity is highly questionable) and then have enough sailing time to be competitive, all signs are that they will sadly need to concede. The real issue is that as result of the Artemis incident, there have been 37 safety recommendations made where the four teams agreed on the vast majority (but not all) of the safety recommendations within protocol rules, but some include further changes to rules, this is the sticking point. ETNZ & LR have the opinion that some of the recommendations which affect the original rules are now being changed to tilt the game in favour of other teams; example is reduced 30% wind speed limits. They made trade-offs in their AC72 design to ensure they had a boat that would be reliable in the conditions originally set down under the Protocol. Apparently, OR have tamed their bucking bronco using “adjustable T rudder devices” to assist the stability of their boat, which is not illegal at this point as the boats are still in testing mode. But as the current rules stand, they would have had to remove these devices for the America's Cup finals in September. Not 100% sure but I understand that OR are trying to slip rule change under the door and using it as safety issue, trying a getting a “free out of jail” design failure card.... two weeks before kick off !!! I would not put it past PC now Artemis is all but finished that he is going to be sock puppet for OR to do everything he can to support OR rule manipulation to ensure OR can successful defend the Cup & keep it in the U.S. As COR he has done nothing but work against the challengers, that he is supposed to be representing.
P.C. tactics - let's debate at a new SD-'battlefield', before they ask you about some structural problems shown during the first artemis towing test (two days after the OR capsize) and the artemis capsize.
will there be any races at round robin, because of the eliminated fines for not racing?!? (so far they sell Spectator Tickets for the opening ceremony, nothing else)
What is "SD" Wolfgang ? Stephen Barclay says "Due to the uncertainty the above brings to the early race schedule, the America's Cup issued refunds for all spectator tickets it had sold to watch races in July during the Round Robins of the Louis Vuitton Cup" read more here With this debacle Louis Vuitton is really pissed ...all that sponsorship money out the window !!!
I'm becoming bit of an AC troll Claudio A French Naval Architect gave his technical perspective to the rudder issue on Anarchy which was very interesting:- ETNZ have a boat that is almost entirely supported on its single main foil. The rudder provides very little lift, just control forces, which are relatively small. As speed changes, lift changes. The main foil is correspondingly adjusted, as this is allowed, so the lift remains as required. The lift on the rudder changes, but since this force is relatively small, the change in attitude on the boat is not problematic, and the local effects of free surface and small size provide a natural limit to motions. When it goes wrong, the boat will pivot about its main foil, potentially creating a high bow down pitch angle, so they've included sufficient buoyancy in the bows to cope. OR have a boat where the lift is shared between the main foil and the rudder. The amount of lift provided by the rudder is still a small proportion of the total, but the rudder lift force is large compared to the rudder control force. As speed changes, lift changes. The main foil is correspondingly adjusted, but the rudder isn't. The change in force on the rudder is significant, and affects the attitude of the boat. A small rudder foil that is required to provide a lot of lift can only do so with a large angle of attack, so with a fixed angle, a large change in trim of the boat is required, hence poor control. When it goes wrong, the boat pivots about the rudder foil, and hence a reduced bow down pitch angle, and hence the boat can have lower volume bows to allow recovery. I'm sure both teams have simulated both approaches. ETNZ decided that they would go for the former, at a price of bigger main foil, lower righting moment, and more aero drag, so they have better control over a wide range of speeds for a given rudder setting. OR decided on the latter as it provides a lower drag solution but for a smaller range of speeds for a given rudder setting. Boat 1 was an extreme example of this, but boat 2 is less extreme. However, OR have found that the range of speeds over which they have good control is too small using the maximum size of rudder foil allowed. Hence, when they are running in the narrow speed range, they look good, but as soon as this is not the case, they have large pitch angles. Using a larger rudder foil requires less boat trim to generate the change in force, and hence better control. The problem OR face is if they were to move the main foils further aft and increase their size, they would then have a boat which, if it goes wrong, will not have enough buoyancy in the bow to recover from the large pitch angle that would occur with the bigger main foil. A potentially dangerous solution and rebuilding the hulls is probably not feasible, since even if they had the time, the added weight is more than their program has in the bank. They aren't allowed new hulls. Furthermore, they have made corresponding design choices with their wing that also suggest the expectation of a narrow speed range, and moving to a higher drag foil solution would present them with power issues. I suspect that OR may have been using a larger rudder foil recently to achieve the improvements we've been seeing, and consequently they already know that operating with class legal rudder foils is not a safe option for them, since if they set up the small rudder foils for lighter winds, and the winds increase during a race, they will have an unacceptably high probability of pitchpoling. As such, the move to increase allowed rudder foil size and control is a real issue for OR, as without it they will have to choose between pulling out of certain races when conditions change, or risking the boat and crew by continuing. ETNZ and LR, on the other hand, don't have this issue, and in fact increasing the rudder foil size on their boats would not only increase drag, but also create control problems due to the size of the control force generated becoming too large. Hence the current dichotomy. OR can quite legitimately claim that they need this change to improve the safety of their boat to acceptable levels. ETNZ/LR can quite legitimately claim that the issue is created by design choices. Since the AC is not just a design and sailing competition, but a design, sailing, and legal competition, we'll have to wait and see who has the best overall package Now the legal card is being threaten by Luna Rosa and if it turns into reality, it would buy time for Artemis ....a interesting Mexican stand-off !!
this will be yet another AC for the courts to play with, and will go down as yet another debacle.... just sail the 45's guys and be done with it...