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18 hours ago, nav said:

No worries...the 4 foil arms are "supplied" so...

5.16 Components marked in Rule 5.1 as “Supplied” may be repaired to their original condition, but such repair
must be approved by the Measurement Committee. If a “Supplied” part is damaged beyond repair, as
demonstrated to the Measurement Committee, that part may be replaced by a new “Supplied” part.

That’s great, but how long does it take to make a foil arm?   Based on what they will look like, and reported time needed to make similar components for the previous 2 cycles, it won’t be quick.  

Not bringing this up to be be petty.  Just seems like the restrictions on the most important components for this boat are to restrictive.  

Having said that, I’d imagine if the 2 challengers confirmed to be participating were similarly concerned they’d voice their opinion.  

WetHog  :ph34r:

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12 hours ago, Tornado-Cat said:

AC 20. 7264m ...:D

Too long - sorry, you're out.

Four more years.

Next....

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1 hour ago, Xlot said:

 

"19.20  The mainsail shall be lowered to the deck without assistance from crew aloft. This should not prevent crew going aloft to resolve occasional issues "

 

Define "occasional" :D This will make the infamous Alinghi halyard lock / headboard episode seem innocuous by comparison. Imagine all the control wires going up to the various batten levels and the potential for snagging is huge.

Do you think the top control arm will have to be lowered too?

 

Easy enough to control - given a 'competent, non-partisan adjudicator!'

'Please raise, lock and then lower the sail while we watch. Thanks.'

But the rule goes further actually and says that the 'main sails' have to be able to be completely removable - without damaging the sail/skins or the mast.

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39 minutes ago, WetHog said:

That’s great, but how long does it take to make a foil arm?   Based on what they will look like, and reported time needed to make similar components for the previous 2 cycles, it won’t be quick.  

Not bringing this up to be be petty.  Just seems like the restrictions on the most important components for this boat are to restrictive.  

Having said that, I’d imagine if the 2 challengers confirmed to be participating were similarly concerned they’d voice their opinion.  

WetHog  :ph34r:

Getting there. You have read the 'per Team' restrictions in the rule - but you know nothing about the number of spares the COR/D have decided to have made in advance

And yes, getting the opinions of the 'uge number of interested teams was exactly what COR/D have been up to this week - all good

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4 hours ago, despacio avenue said:


Question from AC newbie who has followed the AC for years but not in great technical detail: I have read the new Class Rule. What does "Supplied" mean? i.e. who "supplies" and who pays for the items "supplied"?

5.2 In Rule 5.1, the terms in the column “Rule” have the following meaning:

(a) Open: The shape and construction is open to design, within the constraints specified for that com-
ponent within this AC75 Class Rule.

(b) Specified: The outer shape and some aspects of construction are specified by this AC75 Class Rule,
but other aspects of construction are open to design.

(c) Supplied: The component is supplied as standard to all Competitors. Modifications to the compo-
nents are prohibited except where specifically permitted by this AC75 Class Rule.

- who "supplies" ?

my guess is a (NZ?) manufacture under contract to COR/D, (or under contract to a daughter company they set up)

- who pays ? 

the Teams for sure

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11 hours ago, Stingray~ said:

Strangely, you also are allowed two separate foil feet on each side of the end of your foil arms. The boat will be ‘wild.’ Weird to have your support feet at the end of your arms; it’s pretty dang innovative. 

 

Nope

12.1 Each foil must comprise:
(a) a foil arm attached to a foil arm trailing edge and a foil wing, which must form a single linear component;

 

12.5 A foil wing must be symmetric about the foil wing symmetry plane, as defined in Figure 12.1, with a build
tolerance of 3.0 mm.

etc - nothing about 2 separate bits making up the wing.

1 foil arm, 1 foil arm trailing edge, 1 foil wing, 2 foil wing flaps - per side

 

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10 hours ago, barfy said:

14.2 Each foil shall comprise two foil flaps, one lying entirely on one side of the foil wing symmetry plane, and
one lying entirely on the other side of the foil wing symmetry plane.

Ailerons and Flaps

Nope

2 flaps only - attached to each foil wing

one to each side of the 'foil wing symmetry plane' (essentially the point where the foil wing attaches to the supplied foil arm)

i.e. not 2 on one side and none on the other, not 3, not overlapping, not crossing the middle of the foil wing etc

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30 minutes ago, nav said:

Getting there. You have read the 'per Team' restrictions in the rule - but you know nothing about the number of spares the COR/D have decided to have made in advance

And yes, getting the opinions of the 'uge number of interested teams was exactly what COR/D have been up to this week - all good

So how many spares have the COR/D decided to make in advance?

WetHog  :ph34r:

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^

- who knows

- they're not stupid

- it's not your problem so you can relax

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9 hours ago, barfy said:

14.8 At any cross-section and all foil flap rotation angles, when projected on to the foil wing projection plane,
the length of a foil flap must not be greater than 50% of the chord length.

The flaps are going to be substantial. Interesting times, finally moveable trim surfaces; #1 on my x-mas list for this foil fest.

Expect quantum leaps in performance.

Any guesses why they left flaps off the rudder and opted to move the whole thing again?

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9 minutes ago, nav said:

Any guesses why they left flaps off the rudder and opted to move the whole thing again?

My guess is that flaps are less efficient than moving the whole foil .. I had speculated that the main foils would be without flaps too because they had the power to adjust them but they have not gone with that route.

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38 minutes ago, Terry Hollis said:

My guess is that flaps are less efficient than moving the whole foil .. I had speculated that the main foils would be without flaps too because they had the power to adjust them but they have not gone with that route.

How are you thinking about and/or measuring 'efficiency'?

Maybe structure needed for each set-up, complexity, and reliability play some role in the decision?

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1 hour ago, nav said:

12.5 A foil wing must be symmetric about the foil wing symmetry plane, as defined in Figure 12.1, with a build
tolerance of 3.0 mm.

 

So, no inboard downward-looking "winglet" (like in Z-foils) allowed :(  There,s going to be a very rigid coupling between leeway and heeling

 

BTW, no mention at all of interchangeable foil tips

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2 hours ago, nav said:

Easy enough to control - given a 'competent, non-partisan adjudicator!'

'Please raise, lock and then lower the sail while we watch. Thanks.'

But the rule goes further actually and says that the 'main sails' have to be able to be completely removable - without damaging the sail/skins or the mast.

No. The requirement is only to lower the sail, not raise it.  So you can have all the monkeys in bosun chairs you want for hoisting, making up controls and detaching controls before lowering. 

To my earlier point regarding righting from capsize. 

18 hours ago, nav said:

10.2

When constrained to 90° of heel (such that MWP is held perpendicular to the free surface) and left free
to float to equilibrium in the other degrees of freedom:
(a) the centre of buoyancy of the hull surface shall be at least 0.830 m above MWP; and
(b) the angle between LCP and the flotation waterplane shall be no more than 5°.

I don't think this does it. It only specifies the fore and aft trim of the capsized boat, and how high it floats. Not it's return to upright. 

If correct, these boats will require tenders 100% of the time, with some substantial bollard pull to right them when things go wrong. Not a cost control feature!

SHC

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1 hour ago, Terry Hollis said:

My guess is that flaps are less efficient than moving the whole foil .. I had speculated that the main foils would be without flaps too because they had the power to adjust them but they have not gone with that route.

I had speculated that main foils and rudder foil would have flaps. However, as some aircraft fighters they have flaps on the "main wing" and theng rudder moving completely. My guess is that, even if flaps are more energy efficient for the main foils, they need to move the entire rudder foil for maximum efficiency agains pitch pole. They could have flaps too but they made the safe choice.

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2 hours ago, nav said:

Easy enough to control - given a 'competent, non-partisan adjudicator!'

'Please raise, lock and then lower the sail while we watch. Thanks.'

But the rule goes further actually and says that the 'main sails' have to be able to be completely removable - without damaging the sail/skins or the mast.

No. The requirement is only to lower the sail, not raise it.  So you can have all the monkeys in bosun chairs you want for hoisting, making up controls and detaching controls before lowering. 

To my earlier point.

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1 hour ago, nav said:

How are you thinking about and/or measuring 'efficiency'?

Maybe structure needed for each set-up, complexity, and reliability play some role in the decision?

I was thinking of hydrodynamic efficency .. If you have a foil made for maximum lift at lowest drag the addition of a flap must increase the dŕag when compared with a small change in angle of the whole flap.

In addition the extra complexity of the flaps might make it harder to have changeable tips.

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1 hour ago, Steve Clark said:

No. The requirement is only to lower the sail, not raise it.  So you can have all the monkeys in bosun chairs you want for hoisting, making up controls and detaching controls before lowering. 

To my earlier point.

Yep. It is the heads'ls that must be hoistable without anyone aloft - my mistake.

Point remains that it is easily enforceable - and if this.........  making up controls and detaching controls before lowering    means the main can't be lowered once hoisted without someone going aloft - then IMO that would obviously not be within the present rules.

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1 hour ago, Steve Clark said:

....

To my earlier point regarding righting from capsize. 

I don't think this does it. It only specifies the fore and aft trim of the capsized boat, and how high it floats. Not it's return to upright. 

If correct, these boats will require tenders 100% of the time, with some substantial bollard pull to right them when things go wrong. Not a cost control feature!

SHC

It specifies more than just F/A trim, and given a class boat with know and adjustable ballast, heeled within those attitude parameters it seems clear to me that they expect it to meet one of their stated design goals - that it be self-rightable.

I take it that that is what that clause is attempting to ensure.

Well that clause plus the required masthead buoyancy - to overcome the 2 tonnes of water trapped between the skins of the main:D

So just a rowboat as tender -spend the extra money on champagne

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1 hour ago, Terry Hollis said:

I was thinking of hydrodynamic efficency .. If you have a foil made for maximum lift at lowest drag the addition of a flap must increase the dŕag when compared with a small change in angle of the whole flap.

In addition the extra complexity of the flaps might make it harder to have changeable tips.

Not sure about the hydro efficiency question. You're probably right about flaps making interchanging the 'rudder lower' more difficult though.

Maybe all the rest considered it was about 50/50 and costs swung it?

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^ The hull clause ;) - it is very specific about undesirable things like 'tunnels' shudder

10.9 At any transverse cross-section through the hull lower surface:


(a) a path traced from the lowest point on LCP to the perimeter line must never have a component that
points down or towards LCP; and


(b) no vertical line shall cut the cross-section more than once below MWP,


except inside regions defined by cylinders of length 4.000 m and diameter 1.250 m centred on each foil
cant reference point and whose axes are aligned with the foil cant axes.

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6 hours ago, Xlot said:

 

"19.20  The mainsail shall be lowered to the deck without assistance from crew aloft. This should not prevent crew going aloft to resolve occasional issues "

Do you think the top control arm will have to be lowered too?

 

34.66 Mainsail

The combination of sail skins and associated components that are hoisted on the mast.

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 ^ OK. So, this will be different from what seen on the test tri, where the top control arm definitely couldn't be lowered

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The rule should include the following:

Within these constraints,  A team may be asked to demonstrate the the mainsail can be readily and reliably lowered from its in use configuration to deck level in "X" minutes.

Other than floating happily on its side, there is no rule that requires enough righting moment to stand a boat up.  This makes some sense because if the weather foil is in the "Seig Heil" position, half of the ballast is going to be above the deck, and the other foil is going to be more or less straight below the capsized hull.  So they must be counting on the hydraulics to move both foils to their full down position, and that will be enough moment to right the boat. This seems unsatisfactory, or at least highly undesirable.  Unseamanlike to use an old phrase.  

SHC

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So will there be hydraulic controls accessible when inverted? 

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56 minutes ago, Xlot said:

 

 ^ OK. So, this will be different from what seen on the test tri, where the top control arm definitely couldn't be lowered

Not necessarily - I was just giving you the definition. i.e. "the main must be lowered" (and this is what we mean by main).

 

But you have answered your own question haven't you?

 

Do you think the top control arm will have to be lowered too?

....on the test tri, where the top control arm definitely couldn't be lowered

 

If the control arm is not hoisted, as you suggest (i didn't notice one way or the other with the tri) then it is not part of the main - so can stay put, i.e.

34.67 Mast

All components of the rig that are not hoisted with the mainsail or headsails. This includes mainsail
support structures and control systems such as booms that are not part of the mainsail as well
as halyards, rigging, spreaders, fittings, fairings, instrument displays, instrument sensors, cameras,
cables, flotation systems and hydraulic rams that remain as part of the rig whilst sailing. Sheets shall
be considered as part of the mast if they cannot be easily disconnected from mast structures and
control systems.

 

 

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In the LR boat rendering, one set of spreaders is shown - together with conventional upper and lower shrouds, not the classic diamond for rotating masts. Is that even possible?

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Diamonds are the usual for rotating wingspars on multihulls. Lately you see more omitting the diamond and adding lower shrouds to where the spreader bases would have normally been placed. Still divides the mast into panels in the same way but the placement of the lower chainplates is trickier due to stretch of the different length shrouds. Conventional spreaders as Xlot mentions would need to be hinged in such a way that they don't rotate with the mast itself or the travel at the tips would hinder effective mast rotation.  RED HERRING had such spreaders (orginal rig) and the spreaders looked like boomerangs with a crook for the rotation. Steve Clark should be able to explain further.

    This design brief for the AC 36 has lots of 'Splainin' to Do'!

Image result for desi who said lucy you got some splaining to do

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8 hours ago, Xlot said:

So, no inboard downward-looking "winglet" (like in Z-foils) allowed :(  There,s going to be a very rigid coupling between leeway and heeling

BTW, no mention at all of interchangeable foil tips

The rule requires symmetry, so winglets on both tips should comply. If they're used at all I think they'll be very small.

I can't see a "rigid coupling between leeway and heeling" when the foils can be canted independently of heel, adjusting the vertical/horizontal lift vectors as desired.

A more general question: if 3 dimensional X,Y,Z axises are applied to the AC75, which directions do they align with? Is X fore/aft, Y port/starboard and Z vertical?

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9 hours ago, nav said:

5.2 In Rule 5.1, the terms in the column “Rule” have the following meaning:

(a) Open: The shape and construction is open to design, within the constraints specified for that com-
ponent within this AC75 Class Rule.

(b) Specified: The outer shape and some aspects of construction are specified by this AC75 Class Rule,
but other aspects of construction are open to design.

(c) Supplied: The component is supplied as standard to all Competitors. Modifications to the compo-
nents are prohibited except where specifically permitted by this AC75 Class Rule.

- who "supplies" ?

my guess is a (NZ?) manufacture under contract to COR/D, (or under contract to a daughter company they set up)

- who pays ? 

the Teams for sure

Yeaah thats me, Ive already put in a bid

maxresdefault.jpg

west-bay-1-1024x752.jpg

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Is there any effect to be gained if the Foil Control System (FCS) is mounted in such a way that the foil arms and wings vary in attack angle as they articulate, instead of remaining perfectly perpendicular to the hull’s center line? If there’s a tolerance in the rule, how much is it?

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5 hours ago, Steve Clark said:

The rule should include the following:

Within these constraints,  A team may be asked to demonstrate the the mainsail can be readily and reliably lowered from its in use configuration to deck level in "X" minutes.

Other than floating happily on its side, there is no rule that requires enough righting moment to stand a boat up.  This makes some sense because if the weather foil is in the "Seig Heil" position, half of the ballast is going to be above the deck, and the other foil is going to be more or less straight below the capsized hull.  So they must be counting on the hydraulics to move both foils to their full down position, and that will be enough moment to right the boat. This seems unsatisfactory, or at least highly undesirable.  Unseamanlike to use an old phrase.  

SHC

Steve, IMHO all this rule is unsatisfactory, complete BS

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37 minutes ago, Stingray~ said:

Is there any effect to be gained if the Foil Control System (FCS) is mounted in such a way that the foil arms vary in attack angle as they articulate, instead of being always perfectly perpendicular to the hull’s center line?

How would you manage that?

Not possible IMO, as.....

- The arms may only cant

- The cant axis is defined as being longitudinal

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On 3/29/2018 at 6:41 AM, inebriated said:

they will be supplied, and probably over engineered as a result of that so they'll have a solid lifetime. as for the trailing edges, they can be replaced and modified, it's not like they will be the hardest thing to figure out with CFD modelling for the teams

Yeah, but can the things be fetched from the bottom of the gulf?

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16 hours ago, despacio avenue said:


Question from AC newbie who has followed the AC for years but not in great technical detail: I have read the new Class Rule. What does "Supplied" mean? i.e. who "supplies" and who pays for the items "supplied"?

The Class Rule is administered by COR/D,  that is the Challenger of Record and the Defender.

You can take it that COR/D will nominate official suppliers for standard parts needed.  Cost of said parts will be the responsibility of individual teams.

EDIT:  Whoops I skipped a page. I see Nav already provided a comprehensive answer!

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10 minutes ago, KiwiJoker said:

The Class Rule is administered by COR/D,  that is the Challenger of Record and the Defender.

You can take it that COR/D will nominate official suppliers for standard parts needed.  Cost of said parts will be the responsibility of individual teams.

 

So we may have an friendly comptetition between countries with CIC built boats where official suppliers are in the defender's/CoR country for commercial purposes. Evil Larry and Ernie did not do that well.

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2 hours ago, nav said:

How would you manage that?

Not possible IMO, as.....

- The arms may only cant

- The cant axis is defined as being longitudinal

Maybe you cam affect the angle of attach by nose up/ nose down boat attitude?

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11 hours ago, Erwankerauzen said:

Any interesting details regarding the "soft main wingsail"  ??

And therein some major issues need to be resolved. A carbon wing delivers power a quantum leap of over a soft sail and importantly far more efficient depowering as the ability to depower efficiently in apparent wind sailing is where the real speed comes from. Check a 49er changing configuration coming out of the dock then powering up out in the open with a building breeze - and then check them coming into the dock and the strife it can cause with even the Gold fleet guys. As been shown by the Superfoiler, its main is large to get them up on the foils but too large when foiling because of its depowering inefficiencies as opposed to a wing.  A carbon wing on a carbon cat delivers a huge amount of power straight down top the foils and is highly efficient cutting drag when foiling. The drag of a large double skinned fully battened possibly camber induced soft sail will be huge in comparison to the equiv wing and its this drag getting up through the gears that will put these boats on their side PDQ. It takes a few hundred horsepower getting a light AC 45 upright in flat water so getting a new AC mono upright with just its foil weight is pushing it somewhat, especially as that large double skinned sail lying flat will be having a few tons of water on it.

Mind you this thing is doing OK these days, all 6.5 meters of it.

15585020_662538973924332_742523941850760962_o.jpg

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40 minutes ago, Kiwing said:

Maybe you cam affect the angle of attach by nose up/ nose down boat attitude?

Maybe they don't need it too if they have flaps on the main foils

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14 hours ago, nav said:

Nope

2 flaps only - attached to each foil wing

one to each side of the 'foil wing symmetry plane' (essentially the point where the foil wing attaches to the supplied foil arm)

i.e. not 2 on one side and none on the other, not 3, not overlapping, not crossing the middle of the foil wing etc

 

14.2 Each foil shall comprise two foil flaps, one lying entirely on one side of the foil wing symmetry plane, and
one lying entirely on the other side of the foil wing symmetry plane.

not quite nope as i quoted the class rule.

but with an "inner and outer" flap to each foil, the inner might be a huge lifting flap whilst the outside may be more for trim.

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10 hours ago, nav said:

Not sure about the hydro efficiency question. You're probably right about flaps making interchanging the 'rudder lower' more difficult though.

Maybe all the rest considered it was about 50/50 and costs swung it?

hmmm, i would think that the energy used to control pitch with flaps vrs shifting the entire lower bearing fore and aft would not be comparable. As to speed of reaction to prevent nose-in occurances, again, i would think flaps would be more instantaneous. 

THis is an interesting anomaly and certainly a question to ask when we get our 20 questions :)

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13 hours ago, Xlot said:

So, no inboard downward-looking "winglet" (like in Z-foils) allowed :(  There,s going to be a very rigid coupling between leeway and heeling

 

BTW, no mention at all of interchangeable foil tips

but 20 foil flaps can be developed. And there are no restrictions on their shape under load.

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i wonder if we will see cockpits?

there is a rule allowing them, but whether it is worth it will be interesting

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14 hours ago, Steve Clark said:

If correct, these boats will require tenders 100% of the time, with some substantial bollard pull to right them when things go wrong. Not a cost control feature!

 

My impression is that AC boats sail with tenders 100% of the time anyway. 

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6 hours ago, Tropical Madness said:

So will an AC68 be as quick as a 50?

No.

 

Both AC50 and AC72C had 47+ knots as top speed. The  50 could go up to 2,8 times the windspeed, and was very "easy" to handle. AC75 will be much heavier - but are not gaining so much in power - the max power-arm from the center is about 4,5m - thats a little more than the AC50 - but then you have ballast to deal with - and limited how far out you can put the movable ballast (men). And the sails - soft-wings vs carbon-solid- wing - ref. posts above - should be a big advantage to the 50.

 

I believe this AC75s can be a flop compared to the last two.

 

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Who cares about the top speed? The reaching start has gone anyway.

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12 hours ago, Rasputin22 said:

Diamonds are the usual for rotating wingspars on multihulls. Lately you see more omitting the diamond and adding lower shrouds to where the spreader bases would have normally been placed. Still divides the mast into panels in the same way but the placement of the lower chainplates is trickier due to stretch of the different length shrouds. Conventional spreaders as Xlot mentions would need to be hinged in such a way that they don't rotate with the mast itself or the travel at the tips would hinder effective mast rotation.  RED HERRING had such spreaders (orginal rig) and the spreaders looked like boomerangs with a crook for the rotation. Steve Clark should be able to explain further.

    This design brief for the AC 36 has lots of 'Splainin' to Do'!

 

Learned something new :)  I now notice the arrangement is also shown in the original video - so it's not likely to be a "poetic license"

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5 hours ago, SeaGul said:

No.

 

Both AC50 and AC72C had 47+ knots as top speed. The  50 could go up to 2,8 times the windspeed, and was very "easy" to handle. AC75 will be much heavier - but are not gaining so much in power - the max power-arm from the center is about 4,5m - thats a little more than the AC50 - but then you have ballast to deal with - and limited how far out you can put the movable ballast (men). And the sails - soft-wings vs carbon-solid- wing - ref. posts above - should be a big advantage to the 50.

 

I believe this AC75s can be a flop compared to the last two.

 

Thanks, that is the figure I was looking for as I did not read the rule yet.

The AC 50 had a 8,47 beam so the power arm is about the same. I guess the AC 50 is also easier to handle with a foil aligned on the rudder.

The AC75 will be heavier, imo less aerodynamic (some say the contrary though) but will have ballasted foil. I don't comment the sail/wing because we don't really know what they will come up with.

It's a no brainer that AC 50 will be faster in small and medium air, the AC75 having a chance in stronger air, if surviving.

I think we can safely assume that a new revamped AC50 would smoke the AC75 in any conditions.

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On 3/30/2018 at 8:49 AM, nav said:

^

- who knows

- they're not stupid

- it's not your problem so you can relax

I am not the only one who knows nothing.  And I am relaxed.  I won’t be on one of these boats.  Just doesn’t make sense for the 2 boat teams not to have a spare set of foil arms.  

WetHog  :ph34r:

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31 minutes ago, WetHog said:

I am not the only one who knows nothing.  And I am relaxed.  I won’t be on one of these boats.  Just doesn’t make sense for the 2 boat teams not to have a spare set of foil arms.  

WetHog  :ph34r:

I think it would be safe to assume that the supplier will be required to stock spares for all the supplied items.

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1 hour ago, Tornado-Cat said:

Thanks, that is the figure I was looking for as I did not read the rule yet.

The AC 50 had a 8,47 beam so the power arm is about the same. I guess the AC 50 is also easier to handle with a foil aligned on the rudder.

The AC75 will be heavier, imo less aerodynamic (some say the contrary though) but will have ballasted foil. I don't comment the sail/wing because we don't really know what they will come up with.

It's a no brainer that AC 50 will be faster in small and medium air, the AC75 having a chance in stronger air, if surviving.

I think we can safely assume that a new revamped AC50 would smoke the AC75 in any conditions.

 

Here are the radii from the drunk on Thursday ;)

Pick a number.....

On 3/29/2018 at 2:29 PM, inebriated said:

here is a diagram with the foil control system (OD) and restrictions

image.thumb.png.39fdbc4865ed65517c29a0e93f4e02ba.png

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On 3/30/2018 at 1:49 PM, nav said:

^

- who knows

- they're not stupid

- it's not your problem so you can relax

not stupid?   Maybe they are, maybe not, but it's very apparent from reading the rule that they haven't actually figured out the rig as yet, and that little tri they launched was a joke compared to what others have done in the past.

It all reads as though they've seized on an idea - sensible or otherwise, time will tell - and then have had to try and make it work.   Overall, they've tried too hard to do something that was different from anything else or that anyone else has done ( in your dreams boys ) in the past and been locked into a one way path as a result.

The biggest thing though is that instead of making this more about the people than the boats, then it's become more and more complex in terms of systems and they have the token monkeys just to provide a bit of power.  F1 has gone down that path and is losing it's sporting attraction and revenues as a result. 

Having a design race is great and should be part of the AC, but then coralling everyone into a single packaged area that might or might not work in practice is plain dumb.    

Saving costs?  That's bollocks, every team will spend whatever time and money it can lay it's grubby paws on.  Always have done, always will.

 

 

 

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37 minutes ago, nav said:

 

Here are the radii from the drunk on Thursday ;)

Pick a number.....

3,5 m radius + 2, 05 to the center boat = 5,55 maximum leverage IF we consider the radius as a valuable measure, as the foil is 4 m long and they can use flaps.

The foil is longer than the radius !!!!

 

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12 hours ago, barfy said:

 

14.2 Each foil shall comprise two foil flaps, one lying entirely on one side of the foil wing symmetry plane, and
one lying entirely on the other side of the foil wing symmetry plane.

not quite nope as i quoted the class rule.

but with an "inner and outer" flap to each foil, the inner might be a huge lifting flap whilst the outside may be more for trim.

It was what you added that left a lot of guess work!

On 3/30/2018 at 3:24 AM, barfy said:

Ailerons and Flaps

How many Ailerons, how many flaps... (but we've cleared that up now)

I take it that you are noting that there is no need for the (2 only allowed) 'flappy bits' attached to the foil wing to be the same?

So if a team believed there was an advantage to be had they could use different shapes and/or use the flaps independently and for different purposes.

Fair enough - looks like they could.

 

By the way, you say "inner and outer" flap (or maybe one of them is an aileron IYO) - and when they are off to the side of the boat that designation, or inboard/outboard, makes sense - not so much when they are tucked right under the hull, or at head height though!:D

im6ABs1G-0nZZPS5AmHLQz5DGN_bXDXXXM32HGTA

 

 

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On 3/29/2018 at 11:18 PM, Xlot said:

Was thinking the opposite, actually: pseudo-wave piercing bow to avoid slowing down in a wave / face plant. Will have to check impact of min.volumes

For an Archimedian boat sure, but I don't think pointy bows work as well when you are falling from a height.

Think about ETNZ's narrow bowed AC72 going nose down in SF and throwing crew like confetti....

...or what happens here...

image.png.540d10deaf43b6e3deef60d71545649b.png

 

Experience says....

image.png.f56e8bc44e858fedc3e9bfde27f19f66.png

But if the rule doesn't allow it, (which clause is that by the way - 10.11?), then pointy it is.....

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^ Might be better than loosing the rig or having the crew mushed up against the mast or a foil though?

Fattist!

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23 hours ago, Steve Clark said:

The rule should include the following:

Within these constraints,  A team may be asked to demonstrate the the mainsail can be readily and reliably lowered from its in use configuration to deck level in "X" minutes.

....

SHC

 

Requirement....

19.20 The mainsail shall be lowered to the deck without assistance from crew aloft. This should not prevent
crew going aloft to resolve occasional issues.

Compliance....

30.7 Leading up to events, the Measurement Committee will publish dates of measurement periods, during
which Competitors may present their yachtsfor measurement. The Measurement Committee will inspect
the yachts for compliance with this AC75 Class Rule, and Competitors shall provide whatever assistance
is requested by the Measurement Committee to facilitate this process.

Continued compliance....

30.14 The Measurement Committee reserve the right to re-measure or inspect any aspect of a yacht at any
time
, before or after sailing, and may publish procedures for regular measurement inspections.

Ambiguity....

30.15 When a measurement period is open:

(a) if the Measurement Committee believes there is ambiguity as to whether an element of a Competi-
tor’s yacht satisfies the AC75 Class Rule
, they may seek the advice of the Rules Committee. If the

ambiguity remains, the Rules Committee shall rule confidentially on the compliance or otherwise
of the yacht, based on the information presented to them by the Measurement Committee, after
which a measurement certificate may be issued or withheld;

 

....so good enough for most situations hopefully

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1 hour ago, Stingray~ said:

Are there clauses to prevent negative attack on the ww foil wing, for added RM?

Yes. 26.4 and 26.5.

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Sure hope there's a 'capsize override' on that - imagine the FCS refusing to move the foils while you attempt to right the boat - but instead reporting you to the umpires :lol:
 

 

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4 hours ago, Tornado-Cat said:

3,5 m radius + 2, 05 to the center boat = 5,55 maximum leverage IF we consider the radius as a valuable measure, as the foil is 4 m long and they can use flaps.

The foil is longer than the radius !!!!

 

4,6m arm is from centerline boat to center of the foilarm at the bottom of the foil - when the foil has 4 degrees attack to windward - it will be 5,6m when 23 degrees. The windward foil raised will have that  point at less than 5,9m from centre boat. I assume that the foil is symmetric around the end of foilarm.  This is measured from the cross-section figure put in a drawing program.

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11 minutes ago, SeaGul said:

4,6m arm is from centerline boat to center of the foilarm at the bottom of the foil - when the foil has 4 degrees attack to windward - it will be 5,6m when 23 degrees. The windward foil raised will have that  point at less than 5,9m from centre boat. I assume that the foil is symmetric around the end of foilarm.  This is measured from the cross-section figure put in a drawing program.

 

Yes, AKA foil wing symmetry plane (see 12.5)

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3 hours ago, nav said:

For an Archimedian boat sure, but I don't think pointy bows work as well when you are falling from a height.

Think about ETNZ's narrow bowed AC72 going nose down in SF and throwing crew like confetti....

...or what happens here...

image.png.540d10deaf43b6e3deef60d71545649b.png

 

Experience says....

image.png.f56e8bc44e858fedc3e9bfde27f19f66.png

But if the rule doesn't allow it, (which clause is that by the way - 10.11?), then pointy it is.....

Guess we'll have to wait - also check the effective impact of the min.vol. requirement - but:

- from the cross-section, hull bottom will be 1-1.5 m above mean sea level,

- bow will be 8.5 - 10.5 m ahead of foils

Ergo, pitch control authority (via slowish rudder stabilator,, no elevator) will have to be very effective, else a fairly small dive angle will result in the bow digging into a wave. Under those circumstances, what slows the boat / upsets balance less, a scow or wave piercing bow?

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^ We are both imagining our 'best bow' but seem to be thinking of different situations.

You: smoothing out as much as possible 'regular' perturbations in pitch, or bow into waves - yeah? (good point about the slow rudder response)

Me: surviving with the least damage to boat and crew the more 'irregular' situations like sudden bow-down crashes off the foils, or windward capsize for example

 

But these crazy boats will likely bring with them whole new classes of misbehavior :D

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1 hour ago, Xlot said:

Ergo, pitch control authority (via slowish rudder stabilator,, no elevator) will have to be very effective, else a fairly small dive angle will result in the bow digging into a wave. Under those circumstances, what slows the boat / upsets balance less, a scow or wave piercing bow?

^^ What really slows the boat is a 360 wheelee at 40 kts :)

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You are all talking boat and foils. I think the sail/mast is where the left field winner will come from.

Where is the loop hole?

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41 minutes ago, Tornado-Cat said:

You'll read it here before any other designer find it.

Who was the first to suggest bikes and redefined jobs for the sailors last AC?

Did someone suggest it before we saw ETNZ's boat?  They were seriously trailing it 12 months before they launched the boat!

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1 hour ago, Kiwing said:

Who was the first to suggest bikes and redefined jobs for the sailors last AC?

Did someone suggest it before we saw ETNZ's boat?  They were seriously trailing it 12 months before they launched the boat!

Bah, bikes was nothing but new, Cammas did it before, and the swedes decades before.

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2 hours ago, Tornado-Cat said:

Bah, bikes was nothing but new, Cammas did it before, and the swedes decades before.

Did the  Pelle P design of the 77 use hydraulics?

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Is there any on mast height? And the  wind-limits in the regattas?

Seems like it should be a narrow window of good wind to keep the boats balanced but not overturned -or the possibility to reef.

I less wind these will not fly - but maybe they can then use both foils in the water - both with posistive lift - but the ww just to get the hull out of water - the most load on the lw foil. 

 

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1 hour ago, SeaGul said:

 

I less wind these will not fly - but maybe they can then use both foils in the water - both with posistive lift - but the ww just to get the hull out of water 

Like this ;-). ? 

 

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12 hours ago, Kiwing said:

Flap at the back of the wing? Is this possible or likely ?

 

Your post got me thinking - not really about the sort of tab you consider, I think we should all re-read Basiliscus' seminal posts #1721 and 1747 in the Foiling Monohull thread. But considering, as you point out, that a loophole in the Rule may/has resulted in a runaway win, the question was: does a close reading of the Rule allow a slotted flap? That would really make a difference - something like this

IMG_0421.JPG

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  ^ The Rule does allow any number of sail skins. But they all have to be attached to the spar (19.18), so no

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33 minutes ago, Xlot said:

 

  ^ The Rule does allow any number of sail skins. But they all have to be attached to the spar (19.18), so no

(from a phone) does it specify full-length attachment to the spar?

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15 minutes ago, Stingray~ said:

(from a phone) does it specify full-length attachment to the spar?

That's right: "continuously attached"

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2 hours ago, Xlot said:

 

  ^ The Rule does allow any number of sail skins. But they all have to be attached to the spar (19.18), so no

Does it exclude holes (slots) in skins? I don't think I've ever seen a sail with an intentional hole but ....

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2 hours ago, Stingray~ said:

Is there much left open in the area of foil arm trailing edges?

Pretty open - not movable of course.

This is one area where a design team gets to 'express themselves'....

 

           Component                 Rule    Quantity     Change allowance
Foil arm trailing edges     Open*          6                      20% mass

 

*Open: The shape and construction is open to design, within the constraints specified for that component within this AC75 Class Rule.

 

See Figure 13.1: Foil arm modification limits

 

But still, unless someone gets cute I don't expect to see much difference there - materials maybe

 

 

 

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(after a too-strong airport bar drink..) 

Given the controllable foil wing flaps, would it be possible to set the yacht in still water and (gently) propel it forward by canting the foil arms underwater, like a bird flapping its wings in air?

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2 hours ago, Kiwing said:

Does it exclude holes (slots) in skins? I don't think I've ever seen a sail with an intentional hole but ....

As a matter of fact it does

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47 minutes ago, Stingray~ said:

(after a too-strong airport bar drink..) 

Given the controllable foil wing flaps, would it be possible to set the yacht in still water and (gently) propel it forward by canting the foil arms underwater, like a bird flapping its wings in air?

Possibly, but you won't finish before the time limit.

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