JumbleDuck
Well-Known Member
What happens when you have both and they disagree? Is there an automatic hierarchy or does someone (the skipper?) choose between them ad-hoc?
Interesting facts about the AC72...
- Thread starter Iain C
- Start date
What happens when you have both and they disagree? Is there an automatic hierarchy or does someone (the skipper?) choose between them ad-hoc?
flaming
Well-Known Member
The tactician is the boss. The strategist feeds him info like "Left is best" and he decides whether to go with that, or do something tactical with the other boat. Basically speaking the faster you thin your boat is the happier you will be to go with the strategist, but if you think the other boat is faster you'll see more gains in trying to mess with the other guy.
davidej
Well-Known Member
can anyone point me towards some details of their construction?
I looked in vain on Youtube for some film of this.
I looked in vain on Youtube for some film of this.
oldbilbo
...
As an aside, it's intriguing to note how many of the tech-developments and 'go faster' concepts now being demonstrated first saw the light of day among the articles and papers of the Amateur Yacht Research Society, over the past 25-30 years, and tried out invariably on a shoe-string budget at the Weymouth Speed Week. 'Foiling' is a case in point. So is 'canting keels'....
Many, if not most, of the stalwarts of our AYRS have the look and feel of boffins and/or cranks, but a trawl through the long list of international members who receive the Society's newsletters and Letters To Editor include a surprising sprinkling of yachting's most prominent designers. Every so often, an idea that is first explored in the newsletter and argued about ( just as in here ) at length gets a 'proof of concept' outing at Weymouth in October. Many of those ideas fall by the wayside, but some bright ideas - like kitesurfing - inspire some folks to go away, develop the notion a bit, come back with a better Mark II , then Mark III.....
Many of the seemingly good ideas fail to display well on first, or second, outings. The brightest sparks in the crowd have noted that this is more often a limitation of the materials available to the 'inventor-engineer', and quite recent advances in materials science - with real money spent on tank and wind tunnel testing/optimization - make possible artifacts such as the AC72 foils and the articulated wings.
AYRS Newsletters go to members all over the globe - to Aus, to the USA, to Russia, to South Africa, Switzerland, Holland, Argentina..... even Wales and Canada!
Have a peek at the AYRS here: http://www.ayrs.org/, click on 'Catalyst' and have a read of the topics listed back over the past dozen years or so..... and the Article Index. Be surprised, be very surprised!
Many, if not most, of the stalwarts of our AYRS have the look and feel of boffins and/or cranks, but a trawl through the long list of international members who receive the Society's newsletters and Letters To Editor include a surprising sprinkling of yachting's most prominent designers. Every so often, an idea that is first explored in the newsletter and argued about ( just as in here ) at length gets a 'proof of concept' outing at Weymouth in October. Many of those ideas fall by the wayside, but some bright ideas - like kitesurfing - inspire some folks to go away, develop the notion a bit, come back with a better Mark II , then Mark III.....
Many of the seemingly good ideas fail to display well on first, or second, outings. The brightest sparks in the crowd have noted that this is more often a limitation of the materials available to the 'inventor-engineer', and quite recent advances in materials science - with real money spent on tank and wind tunnel testing/optimization - make possible artifacts such as the AC72 foils and the articulated wings.
AYRS Newsletters go to members all over the globe - to Aus, to the USA, to Russia, to South Africa, Switzerland, Holland, Argentina..... even Wales and Canada!
Have a peek at the AYRS here: http://www.ayrs.org/, click on 'Catalyst' and have a read of the topics listed back over the past dozen years or so..... and the Article Index. Be surprised, be very surprised!
toad_oftoadhall
Well-Known Member
Agree. ISTM that if you're going in the same (net) direction at the same speed as the wind there is no wind. In other words ISTM if VMG and CMG are the same speed and direction as the wind there is no wind.
In the case described the boat is sailing net dead downwind no matter how downwind tacking the boat does, as evidenced by the balloon comment.
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stevebrassett
Well-Known Member
Understood now. It was the exact terminology that threw me. I can absolutely see how tacking downwind can result in these boats travelling faster than the wind. Still impressive how much faster, mind.
JumbleDuck
Well-Known Member
Danke schön.
A.T.
Member
Not to forget DDWFTTW:
http://www.ayrs.org/DWFTTW_from_Catalyst_N23_Jan_2006.pdf
Although described (and possibly demonstrated) by Bauer decades earlier, Goodman's little cart stared a viral debate, that resulted in this:
And today this crazy idea is mainstream, and used as a physics exam question:
http://www.aapt.org/physicsteam/2013/upload/E3-1-7-solutions.pdf
toad_oftoadhall
Well-Known Member
v = vw/α. Really?
Assume ALL useful work is lost. (α = 1)
I'll pick an arbitary value for vw of 10m/s.
v = 10 / 1
v = 10m/s.
We're still moving forward at 10m/s with 100pc of work lost.
Shurely shome mishtake?
Tomahawk
Well-Known Member
Something separate to VMG's...
If the grinders are effectively winding up the hydraulics... Why do they do it by hand?
I would kick a coupls off and replace them with Tour De France cyclists working cycle pedals... Legs are far stronger than arms.. Except for apes and chimps..
If the grinders are effectively winding up the hydraulics... Why do they do it by hand?
I would kick a coupls off and replace them with Tour De France cyclists working cycle pedals... Legs are far stronger than arms.. Except for apes and chimps..
Tomahawk
Well-Known Member
Another separate...
What would happen if you pitched Hydroptiere against Oracle?
No upper wind limit. Hydroptiere presently holds the record for a proper sailing boat... The Vectus Speed Bullet is faster but only sails on one tack
What would happen if you pitched Hydroptiere against Oracle?
No upper wind limit. Hydroptiere presently holds the record for a proper sailing boat... The Vectus Speed Bullet is faster but only sails on one tack
flaming
Well-Known Member
Balance. It's harder to pedal when you're getting knocked about than it is to wind handles with your arms.
Tomahawk
Well-Known Member
I would install bucket seats and reclining peddling positions much like those low level recumbent peddle thingies..
Let the boat bounce but the grinders are tucked in firm and steady .... If I was nice I would let them see what is happening?
Let the boat bounce but the grinders are tucked in firm and steady .... If I was nice I would let them see what is happening?
Iain C
Well-Known Member
I think you mean Vestas SailRocket... ;-)
chewi
Well-Known Member
It probably takes longer to get any pressure to unseat, cross the deck, reseat & engage the pedals than just run across & grab the handles.
The delay would be at a critical time, so you'd have to sacrifice counterweight to compensate for that
A.T.
Member
α is just the transmission loss. Hull aero drag and rolling resistance are neglected there for simplicity. The aim is to show, that v > vw is possible even with some losses, not to estimate realistic losses. Without rolling resistance you can roll at v = 10 m/s in vw of 10m/s without transmitting any power from the wheels to the propeller. While you cannot sensibly model the situation v = vw with the simple P = F *vrel approach, you can use it find the limiting v > vw.
If you want a more detailed derivation:
http://orbit.dtu.dk/fedora/objects/orbit:55484/datastreams/file_3748519/content
And estimated losses for water and land:
http://www.boatdesign.net/forums/at...w-directly-downwind-faster-than-wind-ddw2.pdf
JumbleDuck
Well-Known Member
Not as far as I can see. Alpha = 1 means no shaft work on the propeller, so it's effectively acting as an uncoupled sail, so in the limiting case and ignoring other losses you'd expect the thing to blow downwind at wind speed.
toad_oftoadhall
Well-Known Member
Yes, Hull aero drag and rolling resistance are completely neglected and therefore cannot explain the 10m/s speed despite 100pc loss. Looks like the formula is simply wrong.
As TA says, the formlua makes no allowance for that so that's no the explanation, so it looks like the formula is simply wrong.
Jamesuk
Well-Known Member
If you worried about that kind of nonsense you would not go sailing. Ever thought of making the same statement about the boat your on 'if the keel drops off, if the seacoks fail, if you hit something mid Atlantic and sink, if you are inside of the turning block and the block/fibreglass fail in a stuff breeze....
As for NOT following the AC should you be commenting? Ha
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A.T.
Member
The losses are lumped together into the transmission. This is a valid simplification, if you just want to show that steady state is possible at v > vW in principle, despite some losses. Then it doesn't matter where you put the losses.
That's not what I said. There is no contradiction between rolling at windspeed with 100% transmission loss and the formula. If you don't transmit any power, you can loose 100% of it, and it doesn't matter
The formula just gives no useful information for this case, and doesn't have to. You don't care what happens at v <= vW, if you just want to show that steady state is possible at v > vW.
The formula is correct. It follows directly from P = F * vrel:
http://en.wikipedia.org/wiki/Power_(physics)#Mechanical_power
It's just not useful at vrel = 0, but quite usefull for any vrel > 0.
Just like Coulomb's force formula is not useful at r = 0, but quite usefull for any r > 0.
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