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33 minutes ago, noaano said:

UTC 1200:

HB 21.4 kts 171 deg, age mins: 10 err: 3.6 corrected latlon: -14.66108 -32.72014

LO 23.4 kts 158 deg, age mins: 11 err: 4.3 corrected latlon: -13.66535 -30.61117

AV 24.5 kts 168 deg, age mins: 35 err: 14.3 corrected latlon: -13.33709 -31.63229
 

 

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":A 2h18 heure française, le team PRB a été informé du sauvetage de Kevin Escoffier par Jean Le Cam. " Kevin has been rescued.  

Give it a rest chaps. HB was another attempt at evolution, and they should be applauded for spending a fuck ton of money to do so. If you want to try and be innovative you run the risk of breakages al

VG sailors at sea in the rough A translation: JLC: Damien can you receive me ? DS: Yes Jean I can (garbled)... I don't think you're receiving me that well but I receive you very well. JL

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1 hour ago, terrafirma said:

Alex has pulled a few miles on the Verdier Twins behind him and according to a quick measurement has around 740nm in these conditions until he has to pull the trigger to start turning East.

Technically speaking his COG of  <180 means has already "pulled the trigger"... but forgot to load it. 

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7 hours ago, Laurent said:

Jean Le Cam is comparing the foilers to Ferraris, and his old generation straight boards boat to a Renault 4L...

image.png.d6205992450965b0712678c129edfa40.png

 

The letter L in French is pronounced the same way than the world "aile", which means... wing. Therefore the humoristic drawing with 4 "wings" (aka foils)

When I was born, in Boston, my very young parents had a Renault 4L and not much else. They called it the “love bug.” When mom went into labor the car would not start but dad managed to pop the clutch and get us very slowly to the hospital, in time. The car was renamed the “shit box” and traded for a Volkswagen. Mom never forgave Renault, dad, or me.

Sorry for the thread drift from dipole elements, field theory, multipath reflections, double reverse antenna splitters, jsons, and githubs. Back to your fun.

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1 hour ago, Rafael said:

Michel Desjoyeaux (in March 2020): “Corum is probably the boat I have invested the most in” :D

https://www.tipandshaft.com/en/vendee-globe-2020-2021/michel-desjoyeaux-corum-is-probably-the-boat-i-have-invested-the-most-in/JuanKOo.thumb.jpg.9cc89a7dcd14f3772a3763477eda4667.jpg

Juan KO (today): “ehmmm... “

 JuanKOoo.jpg.efa30fdbc00acea1e8e5c345fdcce832.jpg CorumDistmasted.thumb.jpg.4735340ba0233d12e1198146d3be89f7.jpg

The professor is an absolute reference and a legend, no doubt, alltough I think those warning words now, sound a bit like a corporative bussiness politically correct... let's say excuse :)

And logically it's what a new uncharted technical and engineering territory, mixed with an hybrid fashionable and spectacular frankestein result (semi foiling bumping & diving under water crazy fast monohull boats) brings...

The Professor wanted T foils and the skippers didn’t vote for that so.... shrug

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28 minutes ago, stief said:

Of the many weather possibilities ahead, looking forward to watching this low develop. Thanks to the heads-up from Will Harris on (today's EN Live).

823260945_ScreenShot2020-11-20at7_54_59AM.thumb.png.3f27678dc40440c4fe0ba7b736bd556d.png 

The low weather centre is moving east, the fleet might get a good windy push from it.
Anything might happen, Alex is not far ahead from the other 2 boats anymore. Exciting!
 

 

8 minutes ago, KingMonkey said:

Yes am unclear how much they are really trying to get East right now to get some love from that, or whether they are just trying to get South as fast as possible. 

Yep, that's the gamble, and what makes this sport difficult to predict.
 

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3 hours ago, JonRowe said:

If the professor is saying it, thats a sign the skippers are thinking it. I wouldn't be surprised if they propose a new OD mast updated in specs, but allow the old one for grandfathering. 

That way new boats aren't affected because they'll just buy the new spec, existing boats have the option of upgrading if they want, and the big budget teams probably will, but that will mean a supply of older od masts for the budget teams.

It is a win-win for both newer and older because we talk about stronger heavier masts :)

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Vendier boats look faster despite being placed to west route .. it will be interesting how much they would lag behind the optimized 40S condition- Hugo boat?

Someone mentioned the experience level of Alex but those two youngsters have plenty of energy as a bonus. 

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39 minutes ago, stief said:

Amazing what you find clicking on the wrong link :lol: 3m ago a routing track showed up on Windy

1706735993_ScreenShot2020-11-20at8_27_12AM.thumb.png.8714d4acf48ce6a6717ba7833e387fba.png

Usually I click on the wrong link and it’s tits. That’s my story and I am sticking with it.

Tripon looks to be going well west. It looks like Charal will need to soon. I know the notion has been beaten to death but I wonder if he might try reaching down the coast. Rolling the forecast forward it looks not great but the alternative is far to the west. Would JB use his current circumstance to try something very different?

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21 hours ago, noaano said:

It is a website :)

If you work with scripts and JS, maybe you could work a way to make a user side (tampermonkey) script to capture that data, instead of using devtools in chrome?

I can do some JS, but have not touched it for years and happy that way :)

 

thx for the hint. I had a break from web building in a few years and now JS is everywhere. It is nice to see how all this emerged to one thing instead of being splattered overall into several languages and platforms. 

I will try use JS everywhere (smarthome, boat through arduino and raspberry). Access to https and node is all one needs. ;)

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17 minutes ago, loneshark64 said:

Would JB use his current circumstance to try something very different?

Maybe, but not the African dream. If fleet gets blocked in the South Atlantic, I'll be watching for the weather gods to send him a train out. Best indication of such a chance would be the Jules Verne boats setting out. They *really* study the routes to Capetown.

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8 minutes ago, stief said:

Maybe, but not the African dream. If fleet gets blocked in the South Atlantic, I'll be watching for the weather gods to send him a train out. Best indication of such a chance would be the Jules Verne boats setting out. They *really* study the routes to Capetown.

Yeah i was wondering about the next 1500 miles. Would be interesting.

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1 hour ago, KingMonkey said:

Yes am unclear how much they are really trying to get East right now to get some love from that, or whether they are just trying to get South as fast as possible. 

When I roll the tracker's weather forecast forward 72 hr, it looks like going south leads into a maze of light air and upwind sailing.  My guess is they will be aiming for the narrow space between the St. Helena high and the low(s?) to the SW.  And praying it doesn't pinch closed on them.

(the distance line is about 1300 nm - my guess of where three days sailing might put them)

image.png.70b58826139080aeb51c915c6d45291a.png

 

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8 hours ago, noaano said:

What???

A favourable current reduces your drag, increasing your boatspeed, its not like they go backwards. And that makes you go faster, more AWS, win-win?

And even if you disregard drag, favourable current will push you forwards and add to the wind coming from front sector. These boats go so fast that apparent is mostly forward, right?

Really? Must be some other reason.

Apparent from ahead always on these boats.

You have some source explaining this?

It's counter-intuitive when you're used to thinking about drag on a displacement boat. When foiling the more water going over the foils the better because they generate more lift and lower angles of attack can be used which generates less drag. Until the foil is at its optimum angle of attack for the least drag or as much of it is out of the water as possible the speed through water helps. I also think it's why these new generation foils are curved to depower the foil as the fly higher - it's self balancing but the faster the boats go the less foil is in the water generating drag.

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Yah it most definitely depends on the boat configuration and how much current we are talking about. When you're flying in an aircraft and trying to take off, you extend flaps, head into wind & power up. Once you're at altitude - you're trying to minimize drag and conserve fuel.The foiling equivalent would be sailing broad angles in light air to build up that apparent wind to generate enough lift to reduce the drag then pointing desired waypoint VMG and configuring the autopilot to do that so you can reef your mail early to anticipate for the worst. 

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16 minutes ago, climenuts said:
9 hours ago, noaano said:

What???

A favourable current reduces your drag, increasing your boatspeed, its not like they go backwards. And that makes you go faster, more AWS, win-win?.

It's counter-intuitive when you're used to thinking about drag on a displacement boat. When foiling the more water going over the foils the better because they generate more lift and lower angles ......

'Current' has ZERO connection with drag unless you are anchored. 

Think of 'current' as being on a moving carpet.

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Just in time. Tip&Shaft's latest analysis just arrived. Yohann Richomme goes out on a limb and says:

Quote

We will see the sequence with the first depressions next week, for the moment some big speed runs are announced in the south of Africa from the 28th, according to my routings of the day, Hugo Boss would cross the longitude of the Cape of Good Hope on the 29th .

 

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8 hours ago, noaano said:

err-field is predicted error in nautical miles from last ais-update, speed times age of update

GPS has a Horizontal Dilution of Precision (HDOP) as estimate for the accuracy of the location on the globe, and a vertical one (VDOP) too. I would suspect that the HDOP is reported for boat positions for the dilution of precision. Normally, a GPS would also report the HDOP itself. So this Err is on top of the HDOP I understand?

See for details the very technical ESA explanation here:  https://gssc.esa.int/navipedia/index.php/Positioning_Error

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26 minutes ago, jack_sparrow said:

'Current' has ZERO connection with drag unless you are anchored. 

Current will have affect on the relative velocity parts of the boat meet and go through the medium involved, yes? 

Drag (force) formula has this relative velocity through medium as one of the terms, squared, yes?

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42 minutes ago, Miffy said:

Yah it most definitely depends on the boat configuration and how much current we are talking about. When you're flying in an aircraft and trying to take off, you extend flaps, head into wind & power up. 

With aircraft, you maximise lift and minimise relative speed on ground by turning to wind. With boat the goal is different, I guess.

Going against current does increase lift, but drag also. Then again, these lifting surfaces are not allowed to have much control, so there might be edge situations where it is not so clearcut?

Actually, going against current means AoA can be relaxed for equal lift force, and vice versa. These foils would _really_ need way to control lift :)

 

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21 minutes ago, Herman said:

Normally, a GPS would also report the HDOP itself. So this Err is on top of the HDOP I understand?

This error is calculated error magnitude from last position report, speed times time. And its miles, HDOP we don't know as its not reported but that would be meters.

Maybe CEP would be fitting/right term for this error? 

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UTC 1630:

HB 24.1 kts 158 deg, age mins: 14 err: 5.6 corrected latlon: -16.18121 -32.09376

LO 22.9 kts 154 deg, age mins: 11 err: 4.2 corrected latlon: -15.22023 -30.067

AV 25.1 kts 163 deg, age mins: 103 err: 43.1 corrected latlon: -15.02942 -31.19661 

Almost finished 100% full unattended sat ais autoupdate with selenium-wire, thanks for the tip, it is pretty interesting tool. It does not work with OSX for some reason, had to install virtual team redmond -machine, but that I can live with. Started running with zerodrop shoes as well, so already second new thing to try for this week :)

 

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43 minutes ago, jack_sparrow said:

Current' has ZERO connection with drag unless you are anchored. 

Think of 'current' as being on a moving carpet.

12 minutes ago, noaano said:

Current will have affect on the relative velocity parts of the boat meet and go through the medium involved, yes

 

Through the water NO

This therefore irrelevant except for air. 

12 minutes ago, noaano said:

Drag (force) formula has this relative velocity through medium as one of the terms, squared, yes?

Maybe read posts you reply to.

Repetition is not my favourite sport.

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1 hour ago, loneshark64 said:

Usually I click on the wrong  right link and it’s tits. That’s my story and I am sticking with it.

Tripon looks to be going well west. It looks like Charal will need to soon. I know the notion has been beaten to death but I wonder if he might try reaching down the coast. Rolling the forecast forward it looks not great but the alternative is far to the west. Would JB use his current circumstance to try something very different?

FIFY

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Just now, jack_sparrow said:

Through the water NO. 

This therefore irrelevant except for air. 

Can you explain? I sail 10 kts SOG and have current coming against me head on at 5 kts. Foil keeping me aloft meets water at:

a) 5 kts

b) 10 kts

c) 15 kts

Genuinely curious. What do I miss?

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4 minutes ago, noaano said:

Can you explain? I sail 10 kts SOG and have current coming against me head on at 5 kts. Foil keeping me aloft meets water at:

a) 5 kts

b) 10 kts

c) 15 kts

Genuinely curious. What do I miss?

You missed the bits you snip from my post.

50 minutes ago, jack_sparrow said:

Think of 'current' as being on a moving carpet.

 

7 minutes ago, jack_sparrow said:

Maybe read posts you reply to.

Repetition is not my favourite sport.

 

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1 minute ago, Snowden said:

True wind is measured versus the water. Current changes true wind. Take true wind polars and add current vector to get COG.

Ok, I thought true wind is what is reported by weather stations, relative to earth. Nevermind, lets follow the race.

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1 minute ago, dolphinmaster said:

The 75's were looking for flatter water with the move towards the favorable current as much the small speed boost

Equation is indeed different for 75's, as they are so overpowered and able to trim all the time with manpower to do so. Optimal point might be "interesting", I mean they are speed limited mainly by foil cavitation I guess.

 

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3 minutes ago, Snowden said:

True wind is measured versus the water. Current changes true wind. Take true wind polars and add current vector to get COG.

Correct and only place drag comes into play with current.

12 minutes ago, jack_sparrow said:

Through the water NO

This therefore irrelevant except for air. 

 

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4 minutes ago, jack_sparrow said:

Correct and only place drag comes into play with current.

So if I release a balloon, it will not follow true wind south if current is opposite and to north?

Ground wind != true wind?

I am a bit confused, I must be genuinely missing something.

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The confusion here is because some foiling boat have certain speed regimes in which drag reduces as speed increases, due to reduced wetted surface area, reduced form drag, reduced angle of attack, and other effects. Thus, for such a vessel, speed over ground will increase if it sails against a current that allows the vessel to transition to a lower drag mode. That is what the AC boats were doing.

Think of an airboat that can't quite get on the plane. Into a current it might initially be going slower over ground, but the increased speed over water can be enough to get it planing, and once planing, it will accelerate to a higher speed over ground than had it remained in displacement mode.

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11 hours ago, Laurent said:

The letter L in French is pronounced the same way than the world "aile", which means... wing

Thanks. Had missed *that* pun. 

8 hours ago, LeoV said:

Could be, I did talk to PYL (Editor) when he started it , and I get an English weekly email for over a year. Saves translating for you ?
https://www.tipandshaft.com/en/
And T&S is his humor style.

You did, as Jack remembered too.

Re translation, had high expectations that the EN edition would curate all the machine translations of the FR articles. Read both versions, but found many of the FR articles were not on the EN edition. So after a few weeks I went back to their machine translations.

Bonus of each newsletter is the "THE 5 ARTICLES TO READ THIS WEEK". Very useful.

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23 minutes ago, inneedofadvice said:

I'm no physicist but isn't the whole point of foils to reduce the drag of the water displaced by the hull by lifting the boat out of the water? Therefore more lift=less drag on hull? 

 

22 minutes ago, hump101 said:

The confusion here is because some foiling boat have certain speed regimes in which drag reduces as speed increases, due to reduced wetted surface area.....

Yes BUT there is NO relationship between CURRENT and DRAG 

1 hour ago, jack_sparrow said:
1 hour ago, climenuts said:
10 hours ago, noaano said:

What???

A favourable current reduces your drag, increasing your boatspeed, its not like they go backwards. And that makes you go faster, more AWS, win-win?.

It's counter-intuitive when you're used to thinking about drag on a displacement boat. When foiling the more water going over the foils the better because they generate more lift and lower angles ......

'Current' has ZERO connection with drag unless you are anchored. 

Think of 'current' as being on a moving carpet.

Seems I'm the only one here not drinking. :lol:

 

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5 minutes ago, stief said:

Thanks. Had missed *that* pun. 

You did, as Jack remembered too.

Re translation, had high expectations that the EN edition would curate all the machine translations of the FR articles. Read both versions, but found many of the FR articles were not on the EN edition. So after a few weeks I went back to their machine translations.

Bonus of each newsletter is the "THE 5 ARTICLES TO READ THIS WEEK". Very useful.

a hint.

you could add a google translate plugin into Chrome webviewer so you don't have to do all this manual labor.

Open a french page and it translates automatically. 

image.thumb.png.3cb398f4561b9127987e966033236cba.png

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23 minutes ago, noaano said:

Ground wind != true wind?

Yes. This is the fundamental point and could be due to a difference between sailing and aviation parlance?

True wind is ground wind plus current (i.e. the apparent wind with zero boat speed if not anchored). Hence salty old naviguessers talk about "tidal wind".

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12 minutes ago, troll99 said:

a hint.

you could add a google translate plugin into Chrome webviewer so you don't have to do all this manual labor.

Open a french page and it translates automatically. 

Yeah, I use Chrome at times for that reason. Latest MacOS/ Safari now has auto-translate, but still beta.

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2 hours ago, loneshark64 said:

Tripon looks to be going well west. It looks like Charal will need to soon. I know the notion has been beaten to death but I wonder if he might try reaching down the coast. Rolling the forecast forward it looks not great but the alternative is far to the west. Would JB use his current circumstance to try something very different?

Tripon's gybed back as of the last sked. Would have been interesting to see him bang the corner a bit more.

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1 minute ago, jack_sparrow said:

 

Yes BUT there is NO relationship between CURRENT and DRAG 

Seems I'm the only one here not drinking. :lol:

 

There IS a relationship between speed through water and drag, and current contributes to speed through water, and hence drag. When the relationship is inverse, i.e. drag reduces as speed through water increases, then current can reduce drag and correspondingly increase speed.

You need another drink, Jack :D

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However, for the IMOCAs, I am not sure if such an regime of reduced drag with increased speed really exists. I doubt it if they are not fully flying.

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4 minutes ago, Herman said:

Quick weather guesstimate. JLC on non-foiling polars, the other 3 boats on 102% foiling polars. Now drinks at the Vrimibo :-)

Cheers. This Vrimibo? Tempted to see if I they'll let me buy you a drink.

So looks like Thomas and Thomson only an hour apart after the Agulhas Current. Cool.

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5 minutes ago, hump101 said:

However, for the IMOCAs, I am not sure if such an regime of reduced drag with increased speed really exists. I doubt it if they are not fully flying.

Of course it does - the wetted surface area is dramatically reduced even if the entire hull isn't out of the water. You can observe this effect even on 6.5s 

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12 minutes ago, hump101 said:
22 minutes ago, jack_sparrow said:

Yes BUT there is NO relationship between CURRENT and DRAG 

Seems I'm the only one here not drinking. :lol:

1 hour ago, jack_sparrow said:

Current' has ZERO connection with drag unless you are anchored. 

Think of 'current' as being on a moving carpet.

 

There IS a relationship between speed through water and drag, and current contributes to speed through water, and hence drag. When the relationship is inverse, i.e. drag reduces as speed through water increases, then current can reduce drag and correspondingly increase speed.

You need another drink, Jack :D

Add in another one. 

Current contributes to speed/direction 'over the ground' NOT 'through the water'. 

I have worked it out. 

You lot are all homeless and don't know what a fucking carpet is. :lol:

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8 minutes ago, Miffy said:

Of course it does - the wetted surface area is dramatically reduced even if the entire hull isn't out of the water. You can observe this effect even on 6.5s 

Are you absolutely sure you are seeing a negative drag curve, not just a reducing slope on the drag curve?

A negative drag curve has the characteristic that certain speeds are impossible to maintain in a steady state. So, once a certain threshold is exceeded, the boat will accelerate across a speed range which it cannot hold steady in. Conversely, if they slow below a threshold speed, they will drop rapidly down to a much slower speed. A moth is a classic illustration of this. However, something as heavy as an IMOCA or a mini will see a significant reduction in the slope of the drag curve, but not necessarily a negative slope. I don't have data for foiling IMOCAs or minis, though, hence my caveat.....

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Quentin Lucet on the Live earlier today focused on HB's hull shape and wetted surface. Not much different from what he said to Tip&Shaft last year

Quote

What did you deduce from that in terms of the general outline?
Quentin Lucet: Our overall philosophy was to work to reduce the drag to a minimum on the boat, focusing on the hydrodynamics and the foils, as we are relying on their power to sail the boat in the points of sail usually found in the Vendée Globe.

Can you give us some more detail about that?
Quentin Lucet: It involves work on several levels. Firstly, the optimisation of the mass, which we really insisted upon and the centre of gravity, which corresponded to Alex’s request to have a cockpit a long way forward. We came up with the geometry, in particular the shape of the deck line, with volume spread around the centre of the hull, which really meant gains in terms of the mass. That means we could come up with the boat that has the lowest floor to the cockpit in the whole fleet. The second matter was about the aerodynamics, with a lot of design work around the coach roof, both concerning the forward section and the back around the mainsheet traveller. We carried out windage tests using an IMOCA, which showed just how much the traveller acted as  a brake. Consequently, we no longer have a coach roof and then a protective cover over the cockpit, but with a coach roof that stretches from the foot of the mast to the transom. That adds to the protection of the skipper with the cockpit entirely closed off.

Was this closed cockpit the result of these thoughts or something requested by Alex Thomson ?
Quentin Lucet: It was more or less him that came up with that idea. Setting up such a cockpit is completely linked to the sailor who is going to be aboard: does he feel at ease or not with that option? He moved us in that direction.

In practical terms, how does Alex sail the boat with this closed cockpit?  
Quentin Lucet: Everything is centralised, and so he doesn’t need to go outside or to expose himself to the elements to ease the sail or see what the sails are doing. There is everything he needs in terms of openings to allow him to have a view ahead, behind and see the sails, so you could say it’s a sunroof. On top of that, he has installed cameras to allow him to see 360° around the boat. The other advantage is that means he will avoid filling the cockpit, the hollows in the deck and the lines with 400 litres of water: the gains in dynamic mass are huge.

Let’s talk about the hull. What are its characteristics?
Quentin Lucet: The most striking thing I think is the transom that is fairly well rounded with a chine that is not very big. The advantage is that when the boat starts to lift up, very quickly, the wetted surface is reduced, which doesn’t happen so easily with flatter hulls. Then, in terms of the flow of water, we tried to keep the lines as straight as possible, with a bow which has a big nose, which means that once the boat heels over, you reduce still further the drag from the hull.

 

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3 minutes ago, jack_sparrow said:

Stief I always thought you were a detective. :D

You've also used other terms.  Anyway, neither of us is totally senile yet, IIRC (hmmm). SA memory exercise program goes well with 12 step programs.

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17 minutes ago, Snowden said:

?? for a given true wind speed and angle current makes no difference to speed through water. (it's the speed OF the water).

For a given speed over ground, which is what matters to get from A to B, then contrary current will increase vessel speed through water.

As an aside, these few posts are the first I have ever heard of true wind speed defined as wind over water. I have only ever seen it defined as wind over ground in over 30 years as a naval architect. The data provided by sources such as Windy also follow this definition. Is it a monohull yachty thing to treat it as speed over water?

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14 hours ago, stief said:

Quite the hazard. The VOR crews had lots to say about them

 

Being able to have this discourse on a boat which is almost 100% plastic is quite something, one must say..

And even more if you consider that the "plastic usage" part of fossile fuels, is pretty much ridiculous compared to the energy usage of same fuels

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1 minute ago, Snowden said:

Not sure but clearly pre-GPS the only things you could calculate on board were app wind and wind versus water

We started with LORAN receivers using speed over ground to convert apparent wind speed/direction to true wind speed/direction. Speed through water was not used. I'm not aware of any forecasting service that has ever provided wind over water data?

Even in pre-nav systems era we were taught at undergraduate level that the current vector should be accounted for when assessing true wind speed/direction, so the wind felt by a vessel floating in a current in still air is an apparent wind, not the true wind. Happy to learn of alternative definitions, but this discussion on negative drag curves illustrates how important these definitions are to the understanding of what is happening!

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21 minutes ago, stief said:

"The other advantage is that means he will avoid filling the cockpit, the hollows in the deck and the lines with 400 litres of water: the gains in dynamic mass are huge."

 "..gains in dynamic mass are huge."

Which for other teams is the "elephant in the Southern Ocean" (which is not the SO before Chay belts me), particularly coming 'off the foil' then cranking up again. 

That potentially could add up to be a lot of fucking miles. 

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2 hours ago, climenuts said:

It's counter-intuitive when you're used to thinking about drag on a displacement boat. When foiling the more water going over the foils the better because they generate more lift and lower angles of attack can be used which generates less drag. Until the foil is at its optimum angle of attack for the least drag or as much of it is out of the water as possible the speed through water helps. I also think it's why these new generation foils are curved to depower the foil as the fly higher - it's self balancing but the faster the boats go the less foil is in the water generating drag.

Way to go :D

Foils.jpg

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8 minutes ago, yl75 said:

Being able to have this discourse on a boat which is almost 100% plastic

Yup. And carbon, and, and, etc. Haven't paid much attention, but Herrmann and Grets probably discussed this kind of irony. Like Charlie Enright's/ Mirpuri campaigns, past, present and future. As far as social awareness campaigns, I like Sam's Initiatives-Cœur type. 

But, I had no trouble accepting Rothman's and booze sponsors either :lol:

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For boats that can go faster than the wind, is "favourable current" a bad thing?   These things are machines for extracting energy from the difference in wind speed and water speed. 

They are so good at this that in 15kn of wind with no current they extract enough energy to drive the boat at 18ish kn downwind.

But if in the extreme case if they had 15kn of favourable current, then they would be effectively be becalmed and their VMG would only be 15kn! which is 3kn slower than no current. 

Does this also mean that even a small "favourable" current downwind makes less energy available and thus reduces max speed?

 

 

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1700

Boat          TWA         TWS       BS

Boss           88            11.6       21.1

Linked        89            13.8       17.0

Apivia        86             14.5       18.5

Cam          90              14.3        17.1

Bureau      102            13.6       18.5

The armchair polar for HB is still work in progress but as seen below is getting pretty close in speeds to real life.  Excepting Apivia, but clearly that is his fault and not mine!

Finally, the routing solutions for HB and Linked are stupidly close, especially given the increasing amount of inaccuracy the further out in time one goes from the start point.  But, I thought I would post it anyway.

Vendee20.JPG

vendeepolarcomp.JPG

vendeetrackup.JPG

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26 minutes ago, Snowden said:
31 minutes ago, hump101 said:

Is it a monohull yachty thing to treat it as speed over water?

Not sure but clearly pre-GPS the only things you could calculate on board were app wind and wind versus water

Not quite the "only things".

images - 2020-11-21T042511.089.jpeg

images - 2020-11-21T042552.870.jpeg

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38 minutes ago, jack_sparrow said:

 "..gains in dynamic mass are huge."

Which for other teams is the "elephant in the Southern Ocean" (which is not the SO before Chay belts me), particularly coming 'off the foil' then cranking up again. 

That potentially could add up to be a lot of fucking miles. 

I'm imagining some boats needing to run with more sail and shaking out the reef then reefing then shaking it out depending on conditions and struggle to maintain a steady speed while Hugo Boss maintains 25 knots steady in 15 knots wind with a 2nd reef main & J3. 

54 minutes ago, Snowden said:

Not sure but clearly pre-GPS the only things you could calculate on board were app wind and wind versus water

Au contraire - we always dead reckoned on the charts, water speed + sextant sighting/LORAN/visual beacons and it gives you all the same information you'd have today re observed currents just took more people to maintain the effort & time.

59 minutes ago, TheDragon said:

Sebastien Destremau's bizarre cardboard cockpit canopy on MERCI has come apart, but he finds it quite funny. Quite a character.

 

Last edition he was amusing - this edition he seems clinically insane & likely to add to more trash in the ocean. Ari is so much more of a steady follow and less of a shit show - which I can't stomach anymore in 2020. I don't even understand what his cardboard experiment was supposed to be - wood/paper fiber composites? Get some marine plywood, epoxy it and it would have lasted the way around.

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11 hours ago, Tunnel Rat said:

Complete with Renault 4 gear box. :ph34r:

image.jpeg.a61473d5a820620db30c71d89ff603db.jpeg

Got a chuckle from that, I used to own one of these (the "cargo" version) as my first car! We called it the "ham slicer" shifter!
The stickers were holding it together:
image.png.db564c5377867b62043888b0b2f623f7.png

EDIT: Also, the shifter diagram is actually wrong: the 1st gear was actually where you'd expect it to be (ie. forward left). The main weirdness was that reverse was next to 4th (where a 6th gear would have been if there was also a 5th...) with just a weak spring stopping you from getting there! So you had to make sure to pull straight back going from 3rd to 4th as going from 3rd to R would not have been good! 

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18 minutes ago, sfigone said:

For boats that can go faster than the wind, is "favourable current" a bad thing?   These things are machines for extracting energy from the difference in wind speed and water speed. 

They are so good at this that in 15kn of wind with no current they extract enough energy to drive the boat at 18ish kn downwind.

But if in the extreme case if they had 15kn of favourable current, then they would be effectively be becalmed and their VMG would only be 15kn! which is 3kn slower than no current. 

Does this also mean that even a small "favourable" current downwind makes less energy available and thus reduces max speed?

What boat without a motor and no current can go faster than the wind, going dead down wind?

From drinking to crack cocaine in the blink of an eye. :lol:

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Just now, jack_sparrow said:

What boat without a motor and no current can go faster than the wind, going dead down wind DDW?

From drinking to crack cocaine in the blink of an eye. :lol:

VMG not dead down wind.   The AC boats definitely have VMG faster than the wind.    I've not done the math for the open 60s, but it's got to be close because 18+kn boat speed downwind should be close to 15kn VMG.

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The counter-intuitive “contrary current gives higher speed over ground” thing does work for high performance boats that might increase their speed by 3 knots for just a 2 knot increase in wind speed.

Imagine a foiling boat doing 12 knots downwind with zero current and a ten knot “ground” breeze - and therefore 10 knot TWS. Add 2 knots of contrary current and TWS increases to 12 knots … and boat speed to 13. That 3 knot increase in boat speed exceeds the 2 knot loss from the current so it’s a net gain in SOG.
 
Yes, I know it’s not that simple and you can’t sail dead downwind blah blah blah but the principle is sound. I’ve done it on the Waszp and it works. Not in every situation but in the right conditions the effect is very real.
 
Now back to the Vendee. Go Pip!!
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26 minutes ago, Hitchhiker said:

Finally, the routing solutions for HB and Linked are stupidly close, especially given the increasing amount of inaccuracy the further out in time one goes from the start point.

2s!? But, I got lost trying not to misread the deltas . 

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12 minutes ago, Snowden said:
15 minutes ago, jack_sparrow said:

Not quite the "only things".

you forgot your sextant

If I reached for a sextant instead of a hand bearing compass when in the vicinity of fixed objects, I would be declared insane or drunk.

If I reached for a hand bearing compass instead of a sextant when in the vicinity no fixed objects, I would be declared insane or drunk.

If I reached for a sextant to calculate current and it's consequent impact on AWD and AWS, I would declared insane or drunk. 

I am insane or drunk for just writing that.:lol:

 

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58 minutes ago, TheDragon said:

Sebastien Destremau's bizarre cardboard cockpit canopy on MERCI has come apart, but he finds it quite funny. Quite a character.

 

I’m amazed it lasted that long. Actually, I am amazed they really were sticking at cardboard lid on in the first place!

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