The America's Cup

[Michael Rogers]

This is not relevant to Swallowboats (knowing Matt's flair for innovation, I should probably add 'yet'), but please can someone explain how those catamarans do nearly 40 knots in a 20 knot wind? I know the wetted area is negligible once they are up on their foils, and I know those things we call a mainsail are probably as efficient and complex as an aircraft wing, but it still seems like getting more out than is put in - which isn't proper science. Is there an explanation which a bear of very little maths-and-physics brain like me could understand?

Regardless, it made for fantastic television!

Michael

[Peter Cockerton]

Micheal

This may help with understand the speed of these craft
http://www.sailnet.com/forums/learning-sail-articles/18848-understanding-apparent-wind.html

I have also been watching the coverage and as you say great tv, you have to feel for the NZ team robbed of the win by a couple of mins on that 40 min rule.

Peter

[Michael Rogers]

Many thanks indeed, Peter, that's a very helpful and well-written article, which I'm beginning to understand. I've printed it off, and will study it! And, clearly, for 'iceboat' read 'cat on foils'.

I was, of course, aware of apparent wind in a rather unstructured way, and had noted the AC cats tack/gybing downwind (as the faster asymmetrics do when racing). I think I've been hung up on - 'there's only so much energy to drive the boat in a given wind, so where does all that extra energy come from which is needed to make the boat sail so fast?' Of course it isn't extra energy, it's the energy already there but usually needed to overcome friction.

Amazing racing. And yes, as you say, hard luck on the Kiwis. However the 'national' status of both crews is misleading. I understand that Team Oracle USA (sic) comprised something like 7 Kiwis, 6 Aussies, 3 Dutchmen and a Brit!!

Michael

[Andy Dingle]

You ‎will of course be aware of the International Moth that has been sailing on foils for ages, quite amazing. I see on their web site that they now have a '30 knot Club' for those sailors that have sailed at that speed and recorded it on their GPS. Wonder what mods we can do to a Bayraider ...?!

I was very impressed to read that the New Zealand campaign for the America's Cup was paid for by the good Tax Payers of New Zealand! Very impressive. You can imagine the outcry if it was muted that the tax payers in this country be asked to pay for a British campaign! I for one would happily have my taxes diverted to something worthwhile for a change...

I've also been getting my 'Sailing on Telly' fix from www.sail.tv (ok, yes it's on't t'internet, not the telly) and was delighted when I was watching some racing from Bosham featuring some lovely old classic Fireballs, Merlin Rockets, International 14's etc to suddenly see a Bayraider flying across the waves amidst them, great stuff!
Not quite a classic yet but the writing must be on the wall I reckon.


Andy

[Peter Taylor]

I'm not sure about this idea that ice-yachts ( or any other fast sailboats) sail fast because they "make their own wind". If that were so, on a calm day you could give them a push and they'd sail on for ever!

I've always assumed that boats can sail faster than the wind because on a reach the wind is constantly applying a force to the sail. If this force is greater than the frictional drag force then the boat will accelerate and continue to accelerate until it reaches a speed where the friction/drag is as great as the wind force. the wind speed is not in itself a limiting factor.

For a displacement boat the drag increases rapidly as the hull speed is approached so the boat usually sails slower than the wind. For a semi-displacement or planing hull faster speeds can actually decrease the water drag (over displacement mode) so the boat can achieve a higher speed compared to the wind. If the drag force is reduced even more through the use of foils the ultimate speed  reached can be very high with respect to the wind.

Can the apparent wind effect actually act to speed a boat up? I can't decide and enlightenment would be appreciated. On a dead run you can't go at or faster than the wind speed because the accelerating force goes away. Hence fast boats tack down wind. If the apparent wind brings the wind flow over the boat round from the quarter to the beam, that might induce more lift from the sails. And the change in force is non-linear. But of course, if you go too fast compared to the true wind the apparent wind comes onto the bow and stops you - so a pushed ice yacht doesn't go on for ever!

There is now talk of a British Americas Cup Challenge - maybe we could enter an International Moth, they go at similar speeds to the AC72's and we might be able to afford one or two!
Peter

[Mrs Chippy]

We in New Zealand have been glued to the Americas Cup and feel very much that Team NZ is our national team, albeit sponsored by multi-nationals as well as tax payer funding.
The team arrived back in Auckland today and thousands turned out to welcome them home
http://www.stuff.co.nz/sport/americas-cup/9244908/Team-NZ-get-heroes-welcome-in-Auckland
For those who don't know, both of the teams'AC72s were built in New Zealand so we have a lot to be proud of as a sailing nation.

[Mrs Chippy]

And on the "It's sailing, but not as we know it, Jim" note ....... how IT contributed to the performance of the AC72s


http://www.nzherald.co.nz/sport/news/article.cfm?c_id=4&objectid=11134945