Hot summer days mostly in Auckland, bring the warble gloaming on, and the Prada Cup races over the last few days.

www.americascup.com/

www.youtube.com/results?search_query=prada+cup+2021

We read and some write about carbon fiber tonearms, but these 75 ft yachts hydro foiling at up to almost motorway speeds, like F1 on water, sometimes touching 50 knots,or just over, often above 30 knots, these are fast boats, have changed the yachting world, so some say,

A calculator or two:
www.disastercenter.com/convert.htm
www.ginifab.com/feeds/miles_to_km/kph_to_mph.html

and are built from and modified with carbon fiber, the hulls and sails too.



Easier and nicer to replay from the live stream on YouTube I think rather than from the americascup site itself, if only because you can full screen with YT.

Like F1 on water, imagine bugs skating on surface tension...


shows today's two races an hour or more after.

So we've gone from 1-1 to 2-2, over 4 races.

Astonishing technology in these boats, and the virtual eye software making the overlays, so a great screen experience.

Or www.americascup.com/

It's only about a half hour per race, so easily watchable. Albeit an hour between race starts.

I notice that TV1 coverage is different to the above links, and that those above links are ~ 30 sec behind TVNZ.

However IMHO they have better, great commentary, and of course no ads.

Great views of the islands and spectators, & fleet etc.

For those not in Auckland. ;=})

Enjoying the racing but hope it gets to a stage where the boat that wins the start doesn't always emerge victorious. Like F1 it'd be nice to see some passing.
Maybe a change of course will make a change.

My wife is claiming victory either way being an Italian kiwi but I feel her distaste for one J Spittle is colouring her objectivity.😁

I've found this event to be less interesting than the previous one partly due to the lack of entries for the Prada cup and I liked the multi hulls more than the current boats. However you can't ignore the technology and I still have trouble getting my head around just how such large boats fly so fast on a small outrigger.

Irrelevant to our listening pleasures I know but interesting none-the-less. Each layer of carbon fibre on the AC75s hull is tightened (just like the reinforcing in concrete bridge beams) before the epoxy is applied and when all layers (each in a precise direction) are completed, baked. The hull thickness (apart from the internal structure, fittings and bracing) is LESS than 1/2 mm thick. The 1 1/4 ton steel forged arms are all made in Hawera. Human power would be insufficient to raise and lower these. The two batteries aboard (inconveniently placed fore and aft) which power the hydraulics lifting these arms weigh 40kg each. There might be an audio trickle-down path somewhere.

Thanks for that Peter0c, I was wondering where all the 6.5 T came from. On the tele yesterday they said that each of the foils weighed as much as a Toyota Yaris which seems a lot for a 4m long bit of carbon fibre ? ( Id be thinking that a Yaris would be about a T ? )

The arms are steel (the factory that makes them is otherwise involved in making rotary milking sheds and stuff for the gas industry) and only the foils are carbon. Everything else is carbon and all the controls are hydraulic. Everything above the deck (e.g. sail trimming) is by human power whilst below the deck (e.g. raising the arms and trim tabs on the foils including on the rudder) is battery powered.

Thanks for the input peter0c. Amazing technology. Much like Formula 1 on water.
I'm surprised the arms are made from steel. I would have thought they would be from some high tech alloy.
Or are they intentionally from 'heavy' steel to act as counterweights for stability ?

The arms give the boat 'righting moment' just as steel keels and lead bulbs do on conventional mono hulls. I was amazed about the thinness of the hulls.

I thought that the carbon fibre composite is layered up in resin, maybe vacuum applied to extract voids, no heat involved.

The foils have a 'bulb' or weighting in the arms, for 'righting moment' counter-weighting needed when the windward foil is in the air, out of the water - as Pete says.

DarkLantern blog - darklanternforowen.wordpress.com

Oh that makes sense, I wondered why the hell they don't fall over on their side.

See if you can figure this one out. The AC75s are capable of sailing at 4 times the wind speed, hard on uphill into it or downhill on a reach or more likely a run. They obviously can't go directly into the wind - about 40 degrees off with respect to true wind direction - nor directly downhill. However they can go slightly deeper (i.e. more directly downwind) than they can go into the wind. It therefore takes a minimum of 4 or 5 tacks (changing direction whilst going into the wind)) to get from the bottom start mark to the top and 3 or 4 gybes (changing direction with the wind behind) to get back to the bottom mark. So in effect by going across the wind when beating uphill they can get leverage resulting in speeds greater than the wind. The same occurs downhill but this is also more difficult to get your head around. The explanation for the uphill speed is something called apparent wind, which is the wind speed and the apparent changed direction of it as the boat sees it. Think for a bit about a child on a bike that has a flag on it. When the child is not peddeling it is pretty easy to see from the flag the true wind direction. Now when they peddle in any direction, the angle of the flag will be dependent on 1) the true wind direction and 2) the direction that the bike is heading 3) the speed of the bike and 3) the true wind speed. It is the same with yachts but the huge apparent wind / boat speed generated by these things makes the sail settings going downhill very different. With traditional displacement yachts the sails are hard on or pulled in tight when going into the wind and let out (the main by up to 80 degrees) when going downhill with the wind. Older traditional yachts had only symmetrical spinnakers when going downwind and these allowed the boats to go nearly directly downwind but no more than the true wind speed. Newer displacement yachts use gennakers which are non-symmetrical sails and allows them to leverage the wind and create apparent wind. The AC75s take it a step further (they go too fast to allow the use of gennakers) in that they create so much apparent wind and speed that the jib and the main sail need to be kept fairly tight in rather that let right out when going downhill. In fact they only let the main out 12 degrees when doing downwind; even then the traveler (the bit that moves the boom from side to side) is pulled quite high up on the windward side. It looks like only the outhaul (the bit that pulls the bottom of the mainsail back along the boom and thus tightens or loosens it) is let go whilst going downwind. Just to confuse matters, neither of the TNZ or Prada AC75s actually have a boom - the US and UK boats did - so just how they adjust the outhaul is a mystery. All of the mainsail controls (the sheet, traveler and outhaul) are hydraulically driven as is I suspect the jib sheet. (The word sheet normally refers to the bit of rope that lets the mainsail and jib in and out and for that matter, a spinnaker or gennaker if the boat has them). Putting this all together the AC75s appear to be pulling themselves up with their bootlaces such is the power of the apparent wind that they generate. Just 3 years ago most boat designers and builders would have scoffed if it had been suggested that it was possible to foil a monohull on a single leg plus a small foil on the rudder (not forgetting the trim tabs on both) and get close to 60 knots. Of course those knots is not the speed directly to the mark (this is known as velocity made good or VMG which you will hear from the commentators) but the increased speed generated by the apparent wind more than compensates for the extra distance sailed by a factor of about 1.8. Now wouldn't it be great if audio made such rapid technical gains over about a 3 year period.

Phew Peter, 

just throw mega-bucks at a problem and see what solutions arrive?

Yachting has come a long way since I learnt to sail (and team row), at Jellicoe sea scouts on the Invercargill Estuary, in a trusty clinker-built - as a lad in the 60s:








Ahoy there...

"I see music as a lifetime affair." [Rory Gallagher]

Need to move the event down to Bluff. Plenty of breeze out in Foveaux Strait.

I was a sea scout too! 1957-59. Wow, a lifetime ago.

Wow, I was only 5-7 at that time, but remember Dad & his Dad building boats in the big boat shed-workshop behind the house.
Grandad especially had been involved with yachts and early power boats when he was younger.
I've been impressed by the skills in, of construction ever since then, on and off.

So also to Peter0C, thanks so much for providing that technical input!

It prompted me to explore a bit further; there's easily more detail out there on a search, although I haven't watched videos yet.

Thanks!

My Grandfather was a boat builder. Spent many a happy summer holiday on a kauri displacement launch he built. He worked out of a shed on Barrys Point Rd on the North Shore which used to be the family farm back in the day. Sold it all to early, apparently it would be worth quite a bit now.

Family friends had a Cavalier 32. I get why people get it but not for me I haven't got the patience for sailing.

Nothing wrong with launches either.

A friend has a ~100yr old one that he nevertheless didn't compete with in this 2008 centennial memorial race for the 1908 Rudder Cup race in Auckland.

forum.woodenboat.com/showthread.php?89616-100-years-since-the-last-Rudder-Cup

Also:

waitematawoodys.com/tag/rudder-cup/