Sail GP-a new Grand Prix Foiling Cat Racing League

The story here: Pressure Drop - AP Leaks The News http://www.pressure-drop.us/forums/content.php?8629-AP-Leaks-The-News
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More from catsailingnews.com : "Sail GP" launched with former AC50s | Catamaran Racing, News & Design https://www.catsailingnews.com/2018/10/sail-gp-launched-to-be-raced-on-former.html

 

More F50 design detail: F50s upgrades preview over AC50s | Catamaran Racing, News & Design https://www.catsailingnews.com/2018/10/f50s-upgrades-preview-over-ac50s.html

Excerpt:

These boats have been redesigned, re-engineered and rebuilt from the inside out.
Supercharged
Take, for example, flight control. This is the command and control system so vital to maintaining stable flight to keep the boat sailing at pace. And here the F50 designers have really gone to work.

For the F50 both the foil and rudder pitch will be actively controlled. This should make the flight of the boat through the manoeuvres significantly more efficient.

The foils have been produced in higher modulus carbon fibre, producing a thinner section which has less resistance at high boat speeds. The geometry of the boards has been extended outside the maximum beam of the boat which provides more righting moment and a smoother transition between the vertical and horizontal sections of the foil. All of this translates into significantly higher ultimate boat speeds, where the onset of cavitation on the board occurs at a much higher speed as compared to a foil designed under the AC50 class rule.

Batteries have been brought in and are connected to a new hydraulic accumulator to power the foil and rudder pitch control, the jib sheet, and the wing twist control freeing up the two grinders to work on providing power to the wing sheet.

The flight of the boat can be controlled from the twist grips on the steering wheel or from a joystick controlled by the crew member sitting in position 3 (flight controller). The ride height of the boat can be adjusted independent of the fore and aft bow down pitch.

What seems like miles of hydraulic lines stitched inside the hulls and under the floorboards are used to distribute power to cant the boards to the most efficient angle and activate the rudder pitch control system.

The helmsman can control the ride height, the jib sheet, and the rudder differential from push buttons on the steering wheel. The helmsman can also adjust the speed at which those functions are adjusted by adjusting a dial in the centre of the steering wheel. Teamwork and communication will be key to achieving speed and efficiency.

Top speeds are expected to be 53 knots when the boat is reaching in 20 knots of wind speed. The onset of cavitation is predicted to occur at approximately 48 knots of boat speed – a process where high speed causes the water to bubble near the foil, reducing lift and ultimately limiting the ability to fly the boat efficiently once the cavitation becomes excessive.

With battery power on board the teams will have more freedom to tack or gybe more frequently. Skippers and tacticians won’t find themselves waiting for grinders to build power in the system before they can call for the next maneuver.

The F50s will sail with just five crew, the batteries freeing up one grinding position on board. This has led to a complete redesign of the cockpit layout.

Six F50s will be on the water for the first event in Sydney, Australia in February 2019. Three have been extensively modified using parts from parts of the previous AC50 models. Three sets of the F50s hulls are complete new builds. All of the work was done at Core Builders Composites in New Zealand.

 

More on Sail GP: SailGP Receives World Sailing Status >> Scuttlebutt Sailing News https://www.sailingscuttlebutt.com/2018/10/04/sailgp-receives-world-sailing-status/?utm_medium=email&utm_campaign=Scuttlebutt%205181%20-%20October%205%202018&utm_content=Scuttlebutt%205181%20-%20October%205%202018+CID_5651d977b696b68b9e625bc81f748d17&utm_source=Email%20Newsletter&utm_term=SailGP%20Receives%20World%20Sailing%20Status

 

More on SailGP and the "new" AC 50's from Seahorse magazine:
Really, truly this time? - Seahorse Magazine https://www.seahorsemagazine.com/137-content/november-2018/679-really-truly-this-time

 

First F50 flys:

 

When error is not an option-incredible SAILGP drone video: VIDEO: When error is not an option >> Scuttlebutt Sailing News https://www.sailingscuttlebutt.com/2018/11/11/video-error-not-option/?utm_medium=email&utm_campaign=Scuttlebutt%205207%20%20November%2012%202018&utm_content=Scuttlebutt%205207%20%20November%2012%202018+CID_a72a612f2a19f0ccd44e076c4abe6f1d&utm_source=Email%20Newsletter

 

Sail GP--article includes a couple of videos:
SailGP F50s: One Design & Focus on Sailors skills | Catamaran Racing, News & Design https://www.catsailingnews.com/2019/01/sailgp-f50s-one-design-focus-on-sailors.html#more

 

F50 Flight Controls:
SailGP F50 flight Controls Walk through by Tom Slingby | Catamaran Racing, News & Design https://www.catsailingnews.com/2019/01/sailgp-f50-flight-controls-walk-through.html

 

Sail GP: Wing Table Revealed: (from catsailingnews.com)

 

What Kyle didn't really mention is the fundamental purpose of the table. It is really a mechanical computer that expresses the equation, CAn = Kn * CA1, where CAn is the angle of one of the upper control arms (CA2, CA3, CA4) and CA1 is the angle of the bottom control arm. (Also known as bottom camber.) When the bottom of the wing folds like a taco, the table is slaved to CA1 so it tilts. The control cables from the other control arms come down to the cars on the table, and the tilt of the table controls the upper control arms. The distance of the cars from the axis of rotation of the table determines the lever arm for those cables. This is the value of Kn in the equation. Changing the distance of the cars from center is like changing gears in your car.

The twist cylinder is mounted to the underside of the table for convenience, and the chain drives work like the control lines on a mainsheet traveler. In normal use, the cars are not moving very much. The wing sheet moves the entire wing, like playing the traveler on a soft sail. However, it is possible to hold the sheet and play the twist, in which case, the cars would be actively moving back and forth.

Each car has its own track so that the cars can move past each other. When a car goes past center, the value of Kn changes sign. This allows the top of the flap to be inverted.

Because the upper control arms have a linear relationship to the bottom control arm, the wing is self tacking. When the deflection of CA1 is zero, the entire flap is lined up like a board with the main element. As the bottom of the wing inverts to the same angle it had on the previous tack, all of the other control arms also go to their opposite position. No adjustment is needed to come out of the tack with the same camber and twist that the wing had going into the tack. Self-tacking was one of the key requirements for the system when it was designed for the AC72. The near-capsize of Aotearoa showed why OTUSA wanted to have a self-tacking system for safety.

Besides the sheet that goes to the clew of the flap, there's a second sheet to the clew of the main element. This is the inverter line, and it allows the crew to control just when the wing pops to the opposite tack. The inverter line is especially useful in light winds, when friction can keep the wing from popping through when the crew wants it.

 

So the table tilt is monotonic? stbd tack is front up, and port is back up, or vice versa, and the pivot is between the forward and aft sets of cars? The twist cylinder moves the pairs of cars towards or away from the pivot. The cables run bell cranks in the wing.

There doesn't appear to be any force feedback or load balancing?

Is the table - CA 1 slaving entirely fixed, or can it be shaped?

How does the overall aero-elastic stiffness of the flaps compare to the control stiffness? How positive/repeatable are the settings over wind load. What I'm trying to ask is to what extent does the system buffer gusts and is the buffering in the cables or the flap structure.

 

The table moves like a teeter-totter, an equal amount in both directions. I think you mean "symmetric" instead of "monotonic." Yes, the pairs of cars move together toward or away from the pivot.

The first prototype on an AC45 had the axis fore-aft and tilted side-to-side. That is what was inside the large bulbous fairing that appeared in photographs. The side-to-side tilt was easier to understand, but it took up too much room. The axis was turned 90 deg so the table tilted about a transverse axis so it could be totally enclosed within the main element. But the function was still the same, and it worked as you describe.

The cables attach to the table at equal distances either side of the axis. However, the load is predominantly on one cable or the other, because of the airloads on the flap. Basically, the tension on the sheet gets transferred up the cables to the flaps.

The CA1 gearing to the table is fixed. The deflection of CA1 is limited by the camber control to the control arm. The sideways airloads on the entire wing are reacted by the ball, shroud, and sheet. The ball and shroud are at one end, the sheet is at the other, and the hinge line is in between. So it's like holding a piece of paper between two sides and putting a weight in the middle - it wants to fold in half. The same thing is happening with the wing. It wants to fold up, and it's only necessary to limit the folding by a line to the centerline of the main element. That makes the folding symmetrical on each tack for the same setting of the limiter.

Different arrangements have been used for the shapes of the control arms. On the AC45, the arms stick out on either side of the flap. On the AC72 and AC50, the arms look like a hammerhead. The arm extends forward and there's a sector at the end. The cables go around a sheave and then in the transverse direction tangent to the sector at the main element centerline. This keeps the arm mostly within the main element contour for lower drag. The ends of the hammerhead stick out on the lee side when the flap is deflected. There are no bellcranks.

The flaps are very flexible in torsion and stiff in bending. There is a control arm at the bottom of each flap segment. The flap segments are pinned to the adjacent segments, so each control arm controls not only the bottom of one segment but the top of the segment below, too.

The system is very repeatable. This is in part due to the stiffness of the cables. Each control arm has a sensor that measures control arm rotation, and the wing trimmer can trim each control arm to a target value. This compensates for any stretch in the cables. In order to reduce the stretch in the cables, there's an inverse purchase at the bottom and a regular purchase at the top. This makes the cable move much more than the table, but it reduces the tension in the cable.

The buffering in gusts is done by the skill of the wing trimmer, easing and trimming in on the sheet (or actively trimming the twist), just like flying a hull with a conventional soft sail rig.

 

I just gotta ask - Am I the only one who noticed the helm knob goes up to eleven? See Doug's video of Slingsby walk-through. Post #9, twenty seconds in.

 

You must be! I sure didn't notice that..... This stuff redefines "complexity".