INEOS AC 2-0

[flaming]

The big question I have now about INEOS is which foils they will use when the racing is for keeps. They have the ones they launched B1 with, the current ones, and the W foil ones that they have sailed a bit on. I think we can rule out the 1st set, so are they currently sailing the set they think are going to be their "match" foils if they get there, or is that when they change to the W foils?

 

[Bobc]

Sailing upwind is really tricky in a fast boat that has high apparent, because as you go faster the apparent moves back pushing you off even further. Even in the 18s, you have to actively stop yourself from following the tell-tales, or you end up just reaching everywhere. So there's a real balance in keeping the boat-speed to keep the pressure and speed whilst still trying to keep height to work the boat up.

It's similar downwind, as going a bit higher can bring the apparent forwards and increase boat-speed, which then has the effect of bearing you back off to where you were previously, just with more speed.

It's really not the same as displacement sailing, and really messes with your head for a while. Also, unlike conventional boats, these guys are looking in front for the gusts going downwind as they are sailing faster than the puffs, which still messes with my head.

 

[Laser310]

Sailing upwind is really tricky in a fast boat that has high apparent, because as you go faster the apparent moves back pushing you off even further. Even in the 18s, you have to actively stop yourself from following the tell-tales, or you end up just reaching everywhere. So there's a real balance in keeping the boat-speed to keep the pressure and speed whilst still trying to keep height to work the boat up.

It's similar downwind, as going a bit higher can bring the apparent forwards and increase boat-speed, which then has the effect of bearing you back off to where you were previously, just with more speed.

It's really not the same as displacement sailing, and really messes with your head for a while. Also, unlike conventional boats, these guys are looking in front for the gusts going downwind as they are sailing faster than the puffs, which still messes with my head.

it's an interesting issue.

I wonder to what extent they are sailing by feel, and to what extent they are sailing by instrument numbers.

I'm not a pilot.., but I am told that on a lot of high performance planes, it's very much a situation of trusting the instruments

i would guess that sailing these boats too much by feel might have you up.., down.., all over the place.

 

[RJJ]

Sailing upwind is really tricky in a fast boat that has high apparent, because as you go faster the apparent moves back pushing you off even further. Even in the 18s, you have to actively stop yourself from following the tell-tales, or you end up just reaching everywhere. So there's a real balance in keeping the boat-speed to keep the pressure and speed whilst still trying to keep height to work the boat up.

It's similar downwind, as going a bit higher can bring the apparent forwards and increase boat-speed, which then has the effect of bearing you back off to where you were previously, just with more speed.

It's really not the same as displacement sailing, and really messes with your head for a while. Also, unlike conventional boats, these guys are looking in front for the gusts going downwind as they are sailing faster than the puffs, which still messes with my head.

True - I'll never forget the first time I bore away properly on the RS600.

However, surely as regards the tell-tales you just cut the sails flatter to suit?

Definitely true though that longer distance sailed isn't negative on its own. They could always do a straight-line course; they'd have to drop the sails and row though ;-)

 

[Bobc]

it's an interesting issue.

I wonder to what extent they are sailing by feel, and to what extent they are sailing by instrument numbers.

I'm not a pilot.., but I am told that on a lot of high performance planes, it's very much a situation of trusting the instruments

i would guess that sailing these boats too much by feel might have you up.., down.., all over the place.

All by numbers. You should see the cool piece of kit that Giles has.

 

[Bobc]

However, surely as regards the tell-tales you just cut the sails flatter to suit?

Well, no. You're always trying to get flow over the sail, so the tell tales have to flow. The cut of the sail won't change that other than if you change the angle of attack.

Also because these boats go from 6kts to 50kts, the sails need to go from very deep and with the draft at about 38% to very flat with the draft at about 45% in about 5 seconds, otherwise they would just stall.

It's all incredibly difficult stuff, and the only way they can do this is by essentially programming and automating it (humans could never do it fast enough or accurately enough). Hence all the electronics and hydraulic systems. They have basically got a rig setting for every knot of wind speed and pressure setting programmed in, and the boat essentially sets itself up for that on the go.

 

[Buck Turgidson]

At one point I'm sure I saw boat speed of 30+kt and a VMG of 6!!! Does not compute ???

 

[Kukri]

At one point I'm sure I saw boat speed of 30+kt and a VMG of 6!!! Does not compute ???

0h, I am sure I have achieved a boat speed of five knots and a VMG of one knot before now!?

 

[flaming]

At one point I'm sure I saw boat speed of 30+kt and a VMG of 6!!! Does not compute ???

Sure it does. TWA of circa 135-140 downwind, when you are approaching the layline you're not actually going towards the mark very fast at all. After the gybe and you are pointing at the mark your VMG will be equal to your speed.

 

[Wansworth]

A friend of mine has commented that the Uk boat is the only one with a Uk crew whilst LR has jimmy Spital and a
AM Dean Barkerwho is a new zealander

 

[flaming]

A friend of mine has commented that the Uk boat is the only one with a Uk crew whilst LR has jimmy Spital and a
AM Dean Barkerwho is a new zealander

AM also has British Olympic Gold Medalist and 3 time (back to back) moth world champion Paul Goodison trimming their main.

INEOS has Luke Parkinson who is an Aussie on the boat, but plenty of NZ talent off the water.

 

[Laser310]

Sure it does. TWA of circa 135-140 downwind, when you are approaching the layline you're not actually going towards the mark very fast at all. After the gybe and you are pointing at the mark your VMG will be equal to your speed.

VMG is calculated w.r.t. the wind, not the mark

 

[flaming]

VMG is calculated w.r.t. the wind, not the mark

It can be either, I was under the impression it was the mark (or centre of the gate) for the data on the screen during the racing.
Still can be 30kts speed and 6kts VMG up/down wind, especially when just taking off in a light wind race.

 

[Laser310]

It can be either, I was under the impression it was the mark (or centre of the gate) for the data on the screen during the racing.
Still can be 30kts speed and 6kts VMG up/down wind, especially when just taking off in a light wind race.

The convention is to report velocity made good on the mark as VMC - although, in some systems this measure uses SOG rather than BSP.

For sure, the AC TV coverage is not going to get that technical...

I am pretty certain the numbers you see on the coverage are the actual on board instrument numbers (they are being streamed), which use the standard convention of VMG being relative to the TWD

by the way - the recorded data from the boats for each race can be viewed here:

stats

 

[flaming]

The convention is to report velocity made good on the mark as VMC - although, in some systems this measure uses SOG rather than BSP.

For sure, the AC TV coverage is not going to get that technical...

I am pretty certain the numbers you see on the coverage are the actual on board instrument numbers (they are being streamed), which use the standard convention of VMG being relative to the TWD

by the way - the recorded data from the boats for each race can be viewed here:

stats

I'm pretty sure the speed figures are GPS. Having a quick look at that data set, I'm leaning more towards VMG being to mark for 2 reasons.

1, VMG is recorded as positive on the downwind legs, which would not be the convention for VMG/wind.
2. In match 5, GBR VS ITA, you see negative VMG for both boats during a tack on the 1st leg. This would not be consistent with the high speed tacks that happened in that race with regard to VMG/Wind, but could be explained by a post tack speed build phase briefly taking them away from a mark after a wind shift.

 

[TLouth7]

There doesn't seem to be any easily available information on how VMG is being calculated, I would note the Yachting Monthly described it as being to the mark.

At ~1:26:00 in the linked video Ineos put in a tack near the edge of the course and VMG gets up to much closer to boatspeed. Of course this is not definitive but you would not expect to see a massive difference in VMG in the same patch of water if calculated wrt wind.

 

[Laser310]

I'm pretty sure the speed figures are GPS

it's getting more common for fast boats to not measure BSP, and to instead use SOG for everything - including the wind calculations, which conventionally use BSP not SOG

but fast boats can not reliably measure BSP so there is no choice - many just omit the BSP sensor

i have no doubt that the AC boats are in this category

I have had the issue on some fast catamarans - at 25-30kts or more.., BSP gets somewhat unreliable.., and because all the wind numbers are calculated from BSP, those are unreliable and can bounce around. This causes problems when the AP is set to steer to wind. At high speeds, it can be better to tell the instruments to use SOG rather than BSP for the wind calculations.

 

[Laser310]

The convention within yacht racing generally is that VMG is wrt the wind - for example, B&G instruments make this clear in their documentation, as does both Expedition and Adrena software

I agree - it's possible the tv coverage is not following this convention

The positive/negative issue could easily be fudged in the data, by reporting absolute value of VMG - this is common

looking at the data in the link i provided above, if VMG were wrt the mark, you would expect it to soar on the final approach to the mark on every leg, when the boat is pointed right at it

in general, looking across a few prada cup races, this does not happen.

in fact, what i see is that right at the end of the end of windward legs , it usually drops as they bear off to round the mark.

so - i still lean towards the position that they are following the convention of reporting VMG wrt the wind

 

[RivalRedwing]

it's getting more common for fast boats to not measure BSP, and to instead use SOG for everything - including the wind calculations, which conventionally use BSP not SOG

but fast boats can not reliably measure BSP so there is no choice - many just omit the BSP sensor

i have no doubt that the AC boats are in this category

I have had the issue on some fast catamarans - at 25-30kts or more.., BSP gets somewhat unreliable.., and because all the wind numbers are calculated from BSP, those are unreliable and can bounce around. This causes problems when the AP is set to steer to wind. At high speeds, it can be better to tell the instruments to use SOG rather than BSP for the wind calculations.

A bit of an issue with the location of the impeller on an AC boat too

 

[flaming]

looking at the data in the link i provided above, if VMG were wrt the mark, you would expect it to soar on the final approach to the mark on every leg, when the boat is pointed right at it

in general, looking across a few prada cup races, this does not happen.

in fact, what i see is that right at the end of the end of windward legs , it usually drops as they bear off to round the mark.

so - i still lean towards the position that they are following the convention of reporting VMG wrt the wind

It's a gate mark, so the VMG position would be the middle of the gate, which would correlate with VMG reducing as they get to the mark and turn away from the centre to either of the marks.