Arwen's meanderings

Hi everyone and welcome to my dinghy cruising blog about my John Welsford designed 'navigator' named Arwen. Built over three years, Arwen was launched in August 2007. She is a standing lug yawl 14' 6" in length. This blog records our dinghy cruising voyages together around the coastal waters of SW England.
Arwen has an associated YouTube channel so visit www.YouTube.com/c/plymouthwelshboy to find our most recent cruises and click subscribe.
On this blog you will find posts about dinghy cruising locations, accounts of our voyages, maintenance tips and 'How to's' ranging from rigging standing lug sails and building galley boxes to using 'anchor buddies' and creating 'pilotage notes'. I hope you find something that inspires you to get out on the water in your boat. Drop us a comment and happy sailing.
Steve and Arwen

Monday 12 September 2011

'Re-writing the laws of physics'

.......................in the new generation of sail boats.



I promised a blog this week about the technical side of the AC45’s and about the crews who sail them so here goes.....and I hope I’ve got this all correct.

The new standard AC 45's

built for speed and to test the skills of all crews

Firstly each boat has a crew of five and there is plenty of power and sail to handle as sailing conditions yesterday showed. The helmsman seems to have the physically less demanding job on board but needs the quickest reactions as demonstrated on board one of the Oracle boats during the speed trials along the Hoe yesterday. A sharp turn at the end almost resulted in a capsize but for some very judicious use of the tiller. Sharp reactions avoid pitch-poling as well.

I think the curved arm at the back houses a camera or GPS unit

The idea is to keep the leeward hull in the water and the windward hull out of it

The helmsman controls the traveller as well, one of the primary power controls on the huge wing sail. These wing sails are not like conventional ones. They are difficult to ‘read’ and so someone with plenty of experience and a sound working knowledge of these designs has the responsibility of wing trimmer; and when not trimming the wing, that person helps out the crew with other jobs.


........so that order was ignored then.....................


Someone under enormous pressure is the jib/spinnaker trimmer. This persons job is simple (!), namely keeping the head sails at optimum trim. Upwind, that would be the jib. Downwind it’s the spinnaker. And talking of pressure how about taking on the role of bowman? After calling time and distance to the start, your role would then get very physical, with having to crawl out onto the bowsprit to raise spinnaker up or down. Apart from that, you’d be the muscle on board, providing extra back up for the jib/spinnaker trimmer or raising the dagger boards during manoeuvres.

You have to expect getting wet!!!

The jib is the only bit of the boat which each team can design themselves

Finally there is the tactician....chief planner and decision maker. He tells the helmsman what the next moves might be, as well as having a few lines of his own to sort out too. The tactician controls the camber line which controls the shape of the wing and the runner line which controls mast support. Basically, each boat is short crewed and everyone has to pitch in.....super fit, super fast, super strong and heart beats at 150 beats per minute for at least 30 minutes stretches at a time! And throw in to this mix some precise choreography, nerves of steel and complex team work......these guys – true athletes!

round the first mark and heading back up to the next

time for a pause and team talk



So what about the AC45’s themselves? Well being in an excellent position on Saturday morning at Millbay docks afforded me a bird’s eye close up view of these amazing craft.


"So you ARE sure it goes in this slot here?"
"Dunno - where's the instructions like?"



‘Built for speed but with some seriously geeky technology’ is the tag line from the America’s cup squads and they aren’t kidding. Designed so that all teams are sailing identical boats, the AC 45 has two primary aims. Firstly, it’s there to help teams make the transition to a catamaran and wing sail boat of 72 feet long (22m) on which the finals will be raced in San Francisco in July 2013. Secondly, the AC 45 is durable, portable and able to take hard racing (yeah – that was demonstrated yesterday in 30 mph winds in Plymouth Sound) and one which can be packed up and shipped anywhere worldwide.


"2.7m high ye say?"

There are some clever design features as well. Take the jib headsail. It is the only bit of kit on the boat that is left up to each individual team to design. The rest is standard across all seven boats. The jib is critical because it sets up the airflow up onto the wing.....so you can bet there is some serious research and experimentation going on here with all design teams watching each other pretty closely!!

Those wing sails are HUGE. 20m high with hinges – they are a two part wing. The forward rigid D section is the lad bearing part and then that is the rear aft section divided into three flaps, controlled by four hinges. The bottom hinge controls camber or depth of sail; tightening it reduces depth and power the sail creates; the upper three hinges control twist (which increases sail when tightened). Each wing has carbon fibre ribs and these are covered in what I can best describe as ‘shrink wrap’. I guess they have to be easy to repair because one or two looked damaged yesterday after several capsize incidents.


"20 m high? Yur havin' a laugh mate"


"So where did they say this bit goes?"

"Damn....it won't stretch this far.....huh!"

As far as I can work out, I think there are three main controls, camber, twist and the mainsheet traveller. There seems to be some on board electronics which appear to pre-set the twist before each leg. Camber is manually adjusted as you come out of a tack so that you can accelerate rapidly. The mainsheet gets adjusted constantly. The aim seems to be to get just enough control to lift the windward hull out of the water. I don’t think these guys sail for perfect trim. I think they keep a good look out for puffs of wind instead of looking at the wing!! I’m told a 10 to 1 block and tackle system is used to control wing twist.


the stresses on that wing sail mount must be mega huge

Haven't quite worked out what the vertical white markings on the cross strut are for yet

"Er....boys......think I've got me thumb trapped....."

Electronics wise – well I saw the normal log counters, wind speed indicator logs etc. But there was some other stuff. The cross struts have lights on them and they change colour. I saw red and yellow/amber at various times throughout the day. I think, but need to confirm, that yellow//amber lights warn the crew that they have a penalty and they must de-power for at least three boat lengths before powering back up.

"Whoaa, it's so tippy boys!"

"No idea what these ropes do but they look strong!"

on board computer?

There are four ‘fully active’ cameras on every boat which can pan, tilt, zoom etc to capture all the on board action. These images are beamed live over the Internet. Each boat has 14 microphones on board so viewers can hear what is happening...shouted instructions and spray hitting people in the face...very surround sound experience like!


not much netting  for'ard of the strut. Hope the bowman is sure footed

super fitness required for those winches

carbon fibre struts wrapped in super strong cling film!

Three helicopters follow all the action. They spent a good part of yesterday morning flying low and buzzing early morning risers on the Hoe. One techie had a very neat gizmo on a tripod which he kept tilting a turning to face approaching helicopters. I never did get to finds out what it was but it did look an impressive piece of kit. Maybe it is something to do with the new informative graphics which are superimposed onto aerial shots to show key details of the race.





Large arrows show wind direction, while lay lines, tacks and competition routes are highlighted on screen in real time. Incidents are explained in real time with ‘LIVELINE. These are the on screen graphics, which I have to say, are really quite clever and informative, and remember I’m a Luddite not easily impressed by IT! Other on board technology includes GPS and here the techies have excelled. They can track the boats to within 2cm (yes 2cm) of their real position!! It’s to help determine the exact distance between boats and how close they get.....2cm at 25kts........oh yeah! And all to ensure that live onscreen action looks accurate!!



Well in the next blog entry which will be the last before the weekend I will try and make sense of the race course.....but I need to get my head around that. Whilst it all seems really exciting (well it is) it also seems completely chaotic out there!

Steve

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