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WOW - Oracle AC45 with foils !


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#101 Nigel Texas

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Posted 25 June 2012 - 10:05 PM

Sorry for a few simplistic questions but I don't know much anything about sailing with foils...

It seems that the foil on the daggerboard and the foil on the rudder want to be at the same depth to maintain fore-and-aft trim. Wouldn't that explain the daggerboard being only halfway down?

If the foils cannot be trimmed, then wouldn't they have to rise to the surface of the water eventually, in windy conditions (surface-piercing foil)? In that case should there be a vertical extension of the daggerboard and rudder below the foil for directional control?

What is the logic for using an L-foil on the daggerboards instead of an inverted T? It seems a T-foil would create a lot less bending in the daggerboard and in the foil-to-daggerboard connection.



#102 pjh

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Posted 25 June 2012 - 10:11 PM

If there are no extra movable surfaces on the rudder, then this configuration is AC72 legal, correct?

#103 KiwiJoker

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Posted 25 June 2012 - 10:16 PM

First official word from Oracle on their web site. Flying like L Not that it tells us much we don't already know.

"During last week's training session in San Francisco, ORACLE TEAM USA sailors were learning to fly on hydrofoils. An L-shaped daggerboard and T-shaped rudders were fitted to one of the team's AC45s and the platform took flight.

"Foiling is not a new phenomenon. Many high-speed ferries rely on hydrofoils for a smooth ride for their passengers. In sailing, the Moth class has experimented with foils since the early 1970s, about the same time that designers such as Rod Macalpine-Downey were experimenting with foils at Weymouth Speed Week. In 2009 the 60-foot foiling trimaran l'Hydroptere set the record at 51.36 knots.

"Foils help reduce draft and increase speed. They are a very cost efficient way to gain performance. You can research them extensively in the computer before you build them, and they are small scale, compared with a wing. The foil project is a continuation of one started on USA 17, the team's 90-foot trimaran that won the 2010 America'sCup."


#104 Xlot

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Posted 25 June 2012 - 10:21 PM

If there are no extra movable surfaces on the rudder, then this configuration is AC72 legal, correct?


As long as there's a single (nearly vertical) axis of rotation

#105 coxcreek

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Posted 25 June 2012 - 10:24 PM

It is safe and easy for a foiling multihull to lift off reach to broad reaching. hence the baggy and loose offwind sail in one of the shots; they're sailing well downwind and you can just sit around and enjoy the view (as the crew are doing) on this point of sail. Blunted is absolutely right about trimming the platform out via crew positioning ... and I can't see, if the foils are fixed along with T rudder (the latter at zero, or close to, angle of attack) that this method is not being used to work foils, rig and platform equilibrium - remember these are hyper skilled sailors, should be no problem for them.
One obvious observation: the T rudder lifting section is incredibly fine, meaning thickness, chord is also small, high aspect ratio, nice building. Those rudders would have minimal drag even in light airs. In a breeze, it is quite obvious, the foiling AC45 would be MUCH faster.
The blisters on the wing: is Coutts' ones longer and more shovel shaped than in the foiling AC45 shots, which appear more teardrop and with less length. If they were hidden controlling arms (on Coutts") for the second wing element, then why don't they continue further aft? The bllsters are something else entirely, imo, radar, wind prophecy secret electronics, who knows?

#106 coxcreek

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Posted 25 June 2012 - 10:34 PM

About bearing away and the T rudder (and stern platform area) pops up - doesn't happen - remember the foil is going 20 knots plus through the water (at zero angle) thin, thin foil, not huge lift, therefore it is like on rails, holding itself down simply through speed. It is only when you stop, or near stop that the T rudder witl lift out and the crew get a high angle view of the onrushing water surface.

#107 ~Stingray~

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Posted 25 June 2012 - 10:52 PM

Is there any height-balancing effect caused by water pressure's increasing with depth?

#108 notallthere

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Posted 25 June 2012 - 10:57 PM

Maybe foiling is controlled using the vertical adjustment of the daggerboard instead of the more common AOA on rudder T foil (which is not AC72 legal)

#109 ~Stingray~

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Posted 25 June 2012 - 11:00 PM

^ The AOA of the board is for certain adjustable too; although most likely not while underway. Iirc the AC72 rule specifically allows for it.

edit, Xlot: didn't you complain about that being included in a revision to the rule, for cost & complexity reasons?

#110 atg

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Posted 25 June 2012 - 11:02 PM

I am rethinking my assumption of no control. These guys look too relaxed up there. Perhaps there is something keeping it in the water after all.

#111 Asymptote

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Posted 25 June 2012 - 11:09 PM

Completely clueless on foiling but not on structures. Could the L foil be inducing bend in the dagger board and attached so that it automatically reduces its angle of attack when loaded up. Sort of the way a properly designed bending spar (Finn, skiff, etc.) automatically twists and depowers a main in a puff? The daggerboard appears to be bending in the photos.

Just a thought.






#112 coxcreek

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Posted 25 June 2012 - 11:19 PM

Is there any height-balancing effect caused by water pressure's increasing with depth?


Seeing as I could never build such fine section foils as the X AC45 - and have them last, can't really answer that question. But on moderate section foils with higher lift (also more drag) as the foil reaches towards surface, ventilation begins to occur ... and then you sink down a little to deeper, non-aerated water. Guessing that the X AC45 crew are working the wing trim constantly, plus having low lift, very low drag rudder foils, then don't think they have a problem of flying the stern foil)s) clear. Anyway it is dead easy to lift the stern of a foiling multihull ... so that is why I presume the foils there are low lift, low drag. Different story with the set forward main L foils and the crew, I guess again, are watching them (feeling the boat) VERY attentively (maybe something in the blisters to help there)... because if they lift out, then you crash. But the deep running asymmetric lift sections will alleviate that problem.
Amazing developments occurring, far more than what we envisaged with the restrictive AC rule. Now they're really pushing the boundaries.

#113 Xlot

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Posted 25 June 2012 - 11:21 PM

^ The AOA of the board is for certain adjustable too; although most likely not while underway. Iirc the AC72 rule specifically allows for it.


No reason it couldn't be adjustable underway too, by fore-and-aft movement of the top (on deck) daggerboard bearing

edit, Xlot: didn't you complain about that being included in a revision to the rule, for cost & complexity reasons?


That was a Rule amendment that opened the door to canting boards. ETNZ's SL33s should have the feature, but it wouldn't seem to go with L boards

Completely clueless on foiling but not on structures. Could the L foil be inducing bend in the dagger board and attached so that it automatically reduces its angle of attack when loaded up. Sort of the way a properly designed bending spar (Finn, skiff, etc.) automatically twists and depowers a main in a puff? The daggerboard appears to be bending in the photos.

Just a thought.


But a valid one

#114 Doug Lord

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Posted 25 June 2012 - 11:33 PM

Some Russian foilers operating on rivers used what is known as "surface proximity effect" as a form of altitude control. The foil comes up to a point and then no further. Just maybe here,too? But I'm not sure it would work in rough water...

#115 chic014

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Posted 25 June 2012 - 11:35 PM

Completely clueless on foiling but not on structures. Could the L foil be inducing bend in the dagger board and attached so that it automatically reduces its angle of attack when loaded up. Sort of the way a properly designed bending spar (Finn, skiff, etc.) automatically twists and depowers a main in a puff? The daggerboard appears to be bending in the photos.

Just a thought.


Yea they potentially could have an assymetric laminate in there, so a bending load generates twist. Increase the speed, increase lift, increase the bending load from lift, the foil twists, reducing the angle of attack, reducing lift, and there you have a control system.

It's tricky laminate design but not impossible.

#116 kiwi_jon

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Posted 26 June 2012 - 12:17 AM


^ The AOA of the board is for certain adjustable too; although most likely not while underway. Iirc the AC72 rule specifically allows for it.


No reason it couldn't be adjustable underway too, by fore-and-aft movement of the top (on deck) daggerboard bearing


The bottom load-bearing daggerboard bearing must remain fixed relative to the hull and the board is only allowed 20mm logitudinal movement at that bottom bearing i.e 10mm fore and 10mm aft. Not sure that that would be enough to significantly change the angle of attack.

9. DAGGERBOARDS

9.1 Each hull shall have one daggerboard.

9.2 Daggerboards shall penetrate the hull forward of the rudder and aft of the forward
watertight bulkhead per rule 6.11.

9.3 The maximum dimension of any daggerboard shall be 7.000 m in any direction, measured
along a straight line.

9.4 The lowest load-transferring bearing shall not translate relative to the hull.

9.5 A daggerboard shall not translate longitudinally more than 0.020 m within the bearing
referred to in 9.4 above.

9.6 Daggerboards shall not have components such as trim tabs or moveable winglets that can
be adjusted while racing; however, a movable or retractable device the sole purpose of
which is the removal of weed or debris is permitted.



#117 BalticBandit

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Posted 26 June 2012 - 12:27 AM

Sorry for a few simplistic questions but I don't know much anything about sailing with foils...

It seems that the foil on the daggerboard and the foil on the rudder want to be at the same depth to maintain fore-and-aft trim. Wouldn't that explain the daggerboard being only halfway down?

No not true. No more than an airplane needs to have the wings and the horizontal Stabilizer in the same level. What matters is the relative angles of attack of each foil wrt the apparent waterflow as well as the CoG of the hull.

If the foils cannot be trimmed, then wouldn't they have to rise to the surface of the water eventually, in windy conditions (surface-piercing foil)?

A surface piercing foil is one that does not stall or ventilate when part of it lifts out of the water. That's a diferent issue. yes more speed means more lift, so that's why you have to be able to control the angle of attack somehow. you can do that with TE flaps, a fully articulating horizontal foil ("flying section") or you can vary the amount of lift in one of the foils thereby changing angle of the whole hull and in the process changing the angle of attack of the main foil.

Given what I've been reading here about the rules on the foils, the third one is the only real option.

What is the logic for using an L-foil on the daggerboards instead of an inverted T? It seems a T-foil would create a lot less bending in the daggerboard and in the foil-to-daggerboard connection.

Intersting quesiton. Assymptote has an interesting hypothesis...

#118 Tornado-Cat

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Posted 26 June 2012 - 12:31 AM

There is a lot of unknown here, but what do we know:

It is authorized for the AC 72 and the 4 different ways to control the pitch are:
- the control of the twist of the wing
- the depth control of the rudder (is it authorized ?)
- the depth of the main foil
- the angle of the foil by controlling the fore or aft movement of the dagger board in the box by 0,020 m, but it must not be enough to control the angle.

Am I missing something ? For sure a lot, but we are now in the most interesting times, guessing how the AC72 will look like and trying to understand the mind of the architects.

#119 ~Stingray~

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Posted 26 June 2012 - 12:37 AM

at SW by the Fish
--

Fisher's View: Day minus 3 ACWS Newport - The Elephant is in the Room
http://www.sail-worl...-the-Room/98938

#120 ~Stingray~

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Posted 26 June 2012 - 12:43 AM

^
"Then the matter of hydrofoils reared its ugly head. Oracle Team USA has been trialling on of its AC-45s with L-shaped daggerboards and T-foiled rudders in San Francisco with some success. It also has a backlog of experience gained in the development of USA-17, the 90-foot waterline catamaran that won the 33rd America's Cup. Whether other teams have similarly experimented is not known, but all the AC-72 design teams will have been evaluating the theories. Those theories are certain to be transformed into practicality."

#121 bush sailer

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Posted 26 June 2012 - 02:02 AM

I think that there are 2 actions happening for control. 1st as already mentioned a clever twisting laminate so when full load comes on the foil it twists and depowers. the second is speed. There will be a speed at which the boat would leap out of the water and crash - maybe 35 knots. The crew would simply detune the boat to stay under that speed. (still faster than a non foiling boat) In the photos it is very windy and they would be right at the top end of their speed range.

#122 kiwi_jon

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Posted 26 June 2012 - 02:07 AM

Well we know TNZ have been playing about with 'T' foil rudders and 'L' foil boards on the SL33's.

Posted Image


I suspect that one of the reasons for testing 'L' foils is that there is a maximum beam for the AC72 which includes appendages. A 'T' foil may well exceed that maximum beam measurement.

5.5 The overall beam of the AC72 Yacht, in measurement condition and with all components
in the position that yields the maximum beam measurement, shall not exceed 14.000 m.
Appendages, in any and all positions, shall not exceed the maximum permitted overall
beam. Conventional tillers, tiller extensions and winch handles may exceed the maximum
overall beam. Beam shall be measured between vertical planes at the transverse extents of
the AC72 Yacht parallel to the yacht centerplane.



#123 dogwatch

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Posted 26 June 2012 - 02:11 AM

Is there any height-balancing effect caused by water pressure's increasing with depth?


Lift is related to density and water is - more or less - incompressible. So the answer is no apart - possibly - from the effect of aerated water very close to the surface.

#124 frozenhawaiian

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Posted 26 June 2012 - 02:20 AM

Is it possible this wing has a 'twistable' leading edge, being controlled by a mechanism inside of that gizmo/bulb?

At the base of the mast just behind the CORE label (other masts don't have that label btw) there is visible what could be a vertical 'element' separation.

Posted Image

You can make it out in this one too

Posted Image

It may explain why the gizmo seems to almost wrap around the the wing, perhaps with control arms inside of it?

Posted Image


anybody else notice just how much the platform is torquing in that second photo?

#125 dogwatch

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Posted 26 June 2012 - 02:21 AM

Completely clueless on foiling but not on structures. Could the L foil be inducing bend in the dagger board and attached so that it automatically reduces its angle of attack when loaded up. Sort of the way a properly designed bending spar (Finn, skiff, etc.) automatically twists and depowers a main in a puff? The daggerboard appears to be bending in the photos.


Except - I think - that it's been pointed out that L-foils in effect create the opposite of Veal-heel which creates lift to windward - evidently a good thing when beating. Wouldn't a bendy foil increase the negative lift to windward, which is a bad thing?

#126 Enzedel 92

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Posted 26 June 2012 - 02:26 AM

PHOTOSHOPPED!!!!!!!

#127 SW Sailor

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Posted 26 June 2012 - 02:39 AM

I thought so too after seeing Obama at the helm.

#128 Doug Lord

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Posted 26 June 2012 - 02:49 AM

Multifoilers like the Rave, Osprey, Hobie trifoiler, and Rocker rely on active, automatic wand("feelers" on the Hobie) based control of the main foils(daggerboard foils). On all these boats the rudder foil "trails" automatically behind the main foil. The Rave and Osprey use a rudder control as an option-the boats can be sailed without moving the rudder foil at all. If you can move the main foil you don't need to move the rudder foil.
So I checked a preliminary draft I have of the 72 rule and while it says that the board may not move more than 20mm fore and aft at its lower loadbearing support it says nothing(that I saw) about pivoting the board in such a way as the top of the daggerboard moves more than that. If that is still in the final version of the rule I think how they do it is explained: the board could be pivoted to change the angle of incidence of the main foil. It would have to be manually moved but that wouldn't be that big a deal with a properly designed system.
--
This forum will not allow me to upload the rule draft so go here to post 282 if you want to look at a preliminary draft of the AC 72 rule. I imagine somebody here probably has the final version so look under "appendages", ( p11 in the draft).
http://www.boatdesign.net/forums/multihulls/34th-americas-cup-multihulls-34612-19.html

#129 K38BOB

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Posted 26 June 2012 - 02:50 AM

Good question. In the link I posted above, to the Opti kid's photos, he says that on the day he was on board the boat hit 34 knots. It's the highest AC45 speed figure that I've seen; so even if it wasn't fully lifted the day he was out, they've got that same boat really moving. Maybe too fast?

edit: he wrote "When I got back on the chase boat the AC45 got up to 34 knots, the max speed for the day."


Thats what I recall at the time

#130 kiwi_jon

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Posted 26 June 2012 - 03:29 AM

Multifoilers like the Rave, Osprey, Hobie trifoiler, and Rocker rely on active, automatic wand("feelers" on the Hobie) based control of the main foils(daggerboard foils). On all these boats the rudder foil "trails" automatically behind the main foil. The Rave and Osprey use a rudder control as an option-the boats can be sailed without moving the rudder foil at all. If you can move the main foil you don't need to move the rudder foil.
So I checked a preliminary draft I have of the 72 rule and while it says that the board may not move more than 20mm fore and aft at its lower loadbearing support it says nothing(that I saw) about pivoting the board in such a way as the top of the daggerboard moves more than that. If that is still in the final version of the rule I think how they do it is explained: the board could be pivoted to change the angle of incidence of the main foil. It would have to be manually moved but that wouldn't be that big a deal with a properly designed system.
--
This forum will not allow me to upload the rule draft so go here to post 282 if you want to look at a preliminary draft of the AC 72 rule. I imagine somebody here probably has the final version so look under "appendages", ( p11 in the draft).
http://www.boatdesign.net/forums/multihulls/34th-americas-cup-multihulls-34612-19.html


That version is old. Try this for the up-to-date version http://noticeboard.a...s-Rule-V1.1.pdf

Note that the lowest load-transferring bearing must be fixed. Makes it a bit hard to pivot the board fore and aft.

#131 yhcranafvr

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Posted 26 June 2012 - 03:38 AM

That version is old. Try this for the up-to-date version http://noticeboard.a...s-Rule-V1.1.pdf

Note that the lowest load-transferring bearing must be fixed. Makes it a bit hard to pivot the board fore and aft.


And why couldn't the lower bearing act as a axis to fore aft movement of the top bearing, as doug suggested?

#132 patiki

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Posted 26 June 2012 - 04:26 AM

Lots more here

http://www.sail-worl...d=0&tickerCID=0

#133 Scarecrow

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Posted 26 June 2012 - 05:14 AM

Forgetting the foils has anyone seen/got a full height photo of one of the blistered wings going down wind? Should be quite easy to see twist in the fwd element if its there.

#134 msouth

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Posted 26 June 2012 - 05:54 AM

Gotta be a faked pictures, there is no way of steering with t foil rudders, gotta be + rudder to not be unsafe.

#135 nacraoverlord

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Posted 26 June 2012 - 06:02 AM

Gotta be a faked pictures, there is no way of steering with t foil rudders, gotta be + rudder to not be unsafe.


The Stealth F16 and Moth both have T-Foil rudders, and I assume that they can both steer...
http://www.catsailor.com/bb_files/58669-Dscf0161.jpg

#136 atg

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Posted 26 June 2012 - 06:55 AM

That version is old. Try this for the up-to-date version http://noticeboard.a...s-Rule-V1.1.pdf

Note that the lowest load-transferring bearing must be fixed. Makes it a bit hard to pivot the board fore and aft.


Au contraire, the link you provided states only that the lower bearing shall not "translate", i.e. slide, relative to the hull. It says nothing about the lower bearing being "fixed". So the board could easily pivot there. In fact, the entire bearing could pivot.

#137 dogwatch

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Posted 26 June 2012 - 06:59 AM

The Stealth F16 and Moth both have T-Foil rudders, and I assume that they can both steer...
http://www.catsailor...69-Dscf0161.jpg


As do International 14s, British National 12s and Cherubs. Not such a very unusual arrangement these days.

#138 dogwatch

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Posted 26 June 2012 - 07:13 AM

Au contraire, the link you provided states only that the lower bearing shall not "translate", i.e. slide, relative to the hull. It says nothing about the lower bearing being "fixed". So the board could easily pivot there. In fact, the entire bearing could pivot.


Dangerous as it is to argue AC rules with KJ, I think you are correct.

9.4 The lowest load-transferring bearing shall not translate relative to the hull.


This is interesting given some earlier posts.

9.9 Daggerboards shall not be designed or used to generate force for the purpose or effect of increasing righting moment when used on the windward side of an AC72 Yacht.

These KJ has already pointed out

9.6 Daggerboards shall not have components such as trim tabs or moveable winglets that can be adjusted while racing; however, a movable or retractable device the sole purpose of which is the removal of weed or debris is permitted.

8.6 Rudders shall not have components such as trim tabs or moveable winglets, that can be adjusted while racing. However, a movable or retractable device whose sole purpose is the removal of weed or debris is permitted.

Automated systems are out

19.1 Rigging, wing, soft sails, rudders and daggerboards shall only be adjusted manually


#139 dumper

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Posted 26 June 2012 - 07:18 AM

Well we know TNZ have been playing about with 'T' foil rudders and 'L' foil boards on the SL33's.

Posted Image


I suspect that one of the reasons for testing 'L' foils is that there is a maximum beam for the AC72 which includes appendages. A 'T' foil may well exceed that maximum beam measurement.

5.5 The overall beam of the AC72 Yacht, in measurement condition and with all components
in the position that yields the maximum beam measurement, shall not exceed 14.000 m.
Appendages, in any and all positions, shall not exceed the maximum permitted overall
beam. Conventional tillers, tiller extensions and winch handles may exceed the maximum
overall beam. Beam shall be measured between vertical planes at the transverse extents of
the AC72 Yacht parallel to the yacht centerplane.


could someone please post the link to this video, thanks

#140 atg

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Posted 26 June 2012 - 07:30 AM

I am no expert, but I did chat briefly about this with one of the guys who helped write this rule.

Not to quibble, but there is nothing preventing "automated systems". Trim tabs and movable appendages on the foils are out, but there is nothing explicitly prohibiting a canting daggerboard, automated or not. The forces involved get quite large, so there may not NEED to be a rule prohibiting it explicitly, but there are a lot of clever people around. If you could get it to work with a wand, for instance, I think it could be legal, provided the lower bearing did not translate and it met all the power restrictions. The phrase " components such as trim tabs or moveable winglets that can be adjusted while racing" could be interpreted to mean the entire daggerboard, but that seems like a stretch.

With five crew perhaps they can adjust the foil incidence on the 45 daggerboard via the upper bearing with a hydraulic ram and a pump or what have you.

Personally I do not see active/automated incidence control on the rudder being a viable way to fly, but they have explicitly stated that it can only rotate on one axis within 10 degrees of vertical, and it cannot have appendages. Similarly, they seem to have banned holes in the foil to ventilate it. So to my eye the rule does a much better job of limiting what can be done with the rudder than it does limiting what can be done with the daggerboard.


Au contraire, the link you provided states only that the lower bearing shall not "translate", i.e. slide, relative to the hull. It says nothing about the lower bearing being "fixed". So the board could easily pivot there. In fact, the entire bearing could pivot.


Dangerous as it is to argue AC rules with KJ, I think you are correct.

9.4 The lowest load-transferring bearing shall not translate relative to the hull.


This is interesting given some earlier posts.

9.9 Daggerboards shall not be designed or used to generate force for the purpose or effect of increasing righting moment when used on the windward side of an AC72 Yacht.

These KJ has already pointed out

9.6 Daggerboards shall not have components such as trim tabs or moveable winglets that can be adjusted while racing; however, a movable or retractable device the sole purpose of which is the removal of weed or debris is permitted.

8.6 Rudders shall not have components such as trim tabs or moveable winglets, that can be adjusted while racing. However, a movable or retractable device whose sole purpose is the removal of weed or debris is permitted.

Automated systems are out

19.1 Rigging, wing, soft sails, rudders and daggerboards shall only be adjusted manually



#141 dogwatch

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Posted 26 June 2012 - 07:54 AM

^

I'd have thought 19.1 prohibits automated feedback systems even if powered by a wand or similar. Adjustment must be "manual".

#142 Xlot

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Posted 26 June 2012 - 08:43 AM

^^

Agree. Had missed that, makes redundant my thought that a wand would be considered an appendage and thus be illegal (appendages IIRC being limited to boards and rudders)

#143 tim b

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Posted 26 June 2012 - 10:32 AM

It may have been mentioned earlier but is the pod on the wing to control a leading edge slat or something similar to allow more sail adjustment.

Posted Image

#144 Doug Lord

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Posted 26 June 2012 - 11:26 AM


Multifoilers like the Rave, Osprey, Hobie trifoiler, and Rocker rely on active, automatic wand("feelers" on the Hobie) based control of the main foils(daggerboard foils). On all these boats the rudder foil "trails" automatically behind the main foil. The Rave and Osprey use a rudder control as an option-the boats can be sailed without moving the rudder foil at all. If you can move the main foil you don't need to move the rudder foil.
So I checked a preliminary draft I have of the 72 rule and while it says that the board may not move more than 20mm fore and aft at its lower loadbearing support it says nothing(that I saw) about pivoting the board in such a way as the top of the daggerboard moves more than that. If that is still in the final version of the rule I think how they do it is explained: the board could be pivoted to change the angle of incidence of the main foil. It would have to be manually moved but that wouldn't be that big a deal with a properly designed system.
--
This forum will not allow me to upload the rule draft so go here to post 282 if you want to look at a preliminary draft of the AC 72 rule. I imagine somebody here probably has the final version so look under "appendages", ( p11 in the draft).
http://www.boatdesign.net/forums/multihulls/34th-americas-cup-multihulls-34612-19.html


That version is old. Try this for the up-to-date version http://noticeboard.a...s-Rule-V1.1.pdf

Note that the lowest load-transferring bearing must be fixed. Makes it a bit hard to pivot the board fore and aft.

=======================
There is nothing in that version of the rule that prohibits pivoting of the daggerboard as long as it does not translate fore and aft at the lower bearing more than .02m. There is no reference to the lower bearing being fixed-just that it does not translate relative to the hull(it could pivot w/o translating). There have been foilers that used this exact method to avoid the complication of a flap. I'm more convinced than ever that this is the explanation of how they control the main foil angle of incidence. The board would not have to pivot much and could be designed to move easily even under load. But it would ,apparently, have to be done manually.

Note:
9.4 The lowest load transfering bearing shall not translate relative to the hull,
9.5 A daggerboard shall not translate more than .02m(.78")in the bearing referred to in 9.4 above.
There is a prohibition(9.9) against generating force for the pupose of increasing righting moment but the lee foil doesn't do that and the windward foil is retracted.

#145 Peter Hackett

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Posted 26 June 2012 - 11:48 AM

And are we thinking too far out of the box to have the windward L-foil in reverse camber to pull that hull down before the L sucks air? Would like to see the data on what that does to windward shroud load...

#146 pjh

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Posted 26 June 2012 - 12:02 PM

And are we thinking too far out of the box to have the windward L-foil in reverse camber to pull that hull down before the L sucks air? Would like to see the data on what that does to windward shroud load...

Too far.
9.9 Daggerboards shall not be designed or used to generate force for the purpose or effect of increasing righting moment when used on the windward side of an AC72 Yacht.

#147 the loose cannon

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Posted 26 June 2012 - 12:33 PM

Sorry to go all Ockham's razor on you, but what if it is just a daggerboard with an L foil on the bottom, and a fixed T foil on the rudder?

Would not the hull wracking induce angle of incidence?
Would not the crew have some small effect on AOA?
Would not the trimming (as mentioned by Blunted) have an impact?
Etc.

It might just be what you see...

Upwind, full foil down, I don't see much happening foiling wise other than you don't get as much tip vortex off the foils. Downwind, you don't have as much resolved force pushing down on the leward hull, (and you are going faster) so Voila! everything gets quiet and you go zipping along faster and deeper.

One way or another, it will be quite a scene to watch.

#148 Tornado-Cat

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Posted 26 June 2012 - 12:56 PM

Posted Image

#149 Tornado-Cat

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Posted 26 June 2012 - 12:58 PM

I don't know the wing well enough but isn't the top flap moving to control the pressure and thus the pitch ?

#150 atg

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Posted 26 June 2012 - 01:47 PM

^

I'd have thought 19.1 prohibits automated feedback systems even if powered by a wand or similar. Adjustment must be "manual".


Agreed. Sloppy reading on my part.

So one of the crew would have to fly the foil.

#151 ~Stingray~

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Posted 26 June 2012 - 05:02 PM

Photo from a new entry by KL


America's Cup Returns to Tradition Sort Of



Posted Image
Photo © Elizabeth Chandler

#152 Xlot

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Posted 26 June 2012 - 05:28 PM

Goldilocks here, but the rudder tip stabilizer looked too deep, this one's too near the surface - clearly, intended for foil assist, not pure foiling

#153 ~Stingray~

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Posted 26 June 2012 - 05:51 PM

Goldilocks here, but the rudder tip stabilizer looked too deep, this one's too near the surface - clearly, intended for foil assist, not pure foiling

Agreed - This rudder on ORS 4 is not be what Foiling 5 was using in those other photos. The trim-angle lines could be similar though.

#154 Koukel

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Posted 26 June 2012 - 07:25 PM

This is so boring. We should talk about bow knuckles and how the right one can give you an extra tenth of a knot.

Koukel

#155 maxmini

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Posted 26 June 2012 - 08:00 PM

This is so boring. We should talk about bow knuckles and how the right one can give you an extra tenth of a knot.

Koukel

Now now that would not be fair to the thousands of AC 45 owners on the forum :P

#156 Doug Lord

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Posted 26 June 2012 - 08:22 PM

This is so boring. We should talk about bow knuckles and how the right one can give you an extra tenth of a knot.

Koukel

=======================
Talking about an Americas Cup boat foiling is boring??!! You must be kidding!

#157 pjh

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Posted 26 June 2012 - 08:33 PM


This is so boring. We should talk about bow knuckles and how the right one can give you an extra tenth of a knot.

Koukel

=======================
Talking about an Americas Cup boat foiling is boring??!! You must be kidding!


Doug: look up "irony."

#158 ~HHN92~

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Posted 26 June 2012 - 08:45 PM



This is so boring. We should talk about bow knuckles and how the right one can give you an extra tenth of a knot.

Koukel

=======================
Talking about an Americas Cup boat foiling is boring??!! You must be kidding!


Doug: look up "irony."


Also: "Pulling your leg"

#159 Doug Lord

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Posted 26 June 2012 - 08:46 PM




This is so boring. We should talk about bow knuckles and how the right one can give you an extra tenth of a knot.

Koukel

=======================
Talking about an Americas Cup boat foiling is boring??!! You must be kidding!


Doug: look up "irony."


Also: "Pulling your leg"

=========================
Oh, well.........

#160 coxcreek

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Posted 26 June 2012 - 09:18 PM

Looking at those lines of NEGATIVE attack on the above centrally placed rudder foil(s) - that is for shitty wave conditions to keep the sterns DOWN, no lift. Sorry, so boring, eh Doug?

#161 Doug Lord

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Posted 26 June 2012 - 10:10 PM

Looking at those lines of NEGATIVE attack on the above centrally placed rudder foil(s) - that is for shitty wave conditions to keep the sterns DOWN, no lift. Sorry, so boring, eh Doug?

=============
Trying for the same "energy recovery" they go for on the mid-rudder foils on I-14's? Interesting that on Bradfields full flying foilers the rudder foil is nominally set at zero degrees relative to the static waterline and the daggerboard at +2.5 degrees.

check this real good article by Kevin Ellway:

Attached Files



#162 Fishingmickey

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Posted 26 June 2012 - 10:47 PM

I really hope this is what their 72 looks like! Although now if one aims at one day competing in the cup, do they train in moths or cats?


Both....

#163 SimonN

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Posted 26 June 2012 - 11:07 PM

On a cat, I have problems with the "recovered energy" condition. As said in the article, it works when the lift is perpendicular to the (water) flow and anybody who has sailed an I14 knows that you need to sail the boat seriously flat to get the benefit. So what happens on a cat, where you sail with heel? Because of this, I have never been convinced that recovered energy foils would work on a cat, unless you angle the foils so they are flat when the boat is heeled and lifted the windward one out of the water, whichj I don't think is practical.

However, that doesn't mean that foils on the rudder don't provide other benefits such as pitch control and reduced displacement.

#164 bluelaser

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Posted 27 June 2012 - 02:32 AM

What if the daggerboard had a profile like a parenthesis? In theory you could change the AOA by adjusting the up and down position of the board. I would not want to be the guy tasked with adjusting the board, but it could work.


Although from what I've read above above a pivoting lower bearing and a moveable upper bearing on the daggerboard seems legal. Either way foiling is badass!

#165 dogwatch

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Posted 27 June 2012 - 05:12 AM

This is so boring. We should talk about bow knuckles and how the right one can give you an extra tenth of a knot.


Never mind, there's always the ADM thread if you need more excitement.

#166 BalticBandit

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Posted 27 June 2012 - 07:49 AM

Looking at those lines of NEGATIVE attack on the above centrally placed rudder foil(s) - that is for shitty wave conditions to keep the sterns DOWN, no lift. Sorry, so boring, eh Doug?

Seems to me instead that's what you would want when flying a big gennaker in an accellerating bearoff....

#167 Il Mostro

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Posted 27 June 2012 - 08:26 AM

Maybe you all have a definitive answer to the foil or hoax question now? in which case sorry for this...

But as a Moth sailor the set up in the original Voile et Voilier pictures does not look like a serious effort. First the 'L' or 'T' foil is an inefficient and structurally poor shape. It requires an adjustable flap or ability to pivot the whole foil. The only reason we use it on the Moth is to preserve our 'mono-hull' status. A curved self levelling foil would be much superior.

Second the foil is shown to be retractable. This would require any control system to be quickly detachable from the vertical foil. It's hard enough to engineer a system with the necessary strength and precision to move the foil under load without making it quick release.

Third, if you were working on foils would you not hire the world's most successful foil designer Andrew McDougall?

I can't say if they were photo-shopped or not but it doesn't look like a viable system to me - guess I'll now be proved completely wrong!

As a footnote: I was fortunate to meet Russell Coutts a year ago and offered him a go in my Mach 2 Moth - he wasn't interested.

#168 KiwiJoker

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Posted 27 June 2012 - 09:38 AM

Maybe you all have a definitive answer to the foil or hoax question now? in which case sorry for this...

But as a Moth sailor the set up in the original Voile et Voilier pictures does not look like a serious effort. First the 'L' or 'T' foil is an inefficient and structurally poor shape. It requires an adjustable flap or ability to pivot the whole foil. The only reason we use it on the Moth is to preserve our 'mono-hull' status. A curved self levelling foil would be much superior.

Second the foil is shown to be retractable. This would require any control system to be quickly detachable from the vertical foil. It's hard enough to engineer a system with the necessary strength and precision to move the foil under load without making it quick release.

Third, if you were working on foils would you not hire the world's most successful foil designer Andrew McDougall?

I can't say if they were photo-shopped or not but it doesn't look like a viable system to me - guess I'll now be proved completely wrong!

As a footnote: I was fortunate to meet Russell Coutts a year ago and offered him a go in my Mach 2 Moth - he wasn't interested.



Thanks. Good first effort for a newbie, but ....

I think most of us here have accepted that there was no PhotoShopping involved. Multiple shots from different angles and Oracle has released the pix and made a public announcement that they are testing foils. So, accept that but at the same time we know that disinformation is part of the Cup game. And we know they aren't about to show us the details of a successful concept a year ahead of competition.

We also know from pix that ETNZ has been experimenting with L foils. Others here have guessed it's to do with max beam restrictions. Whatever, it seems like a common line of enquiry.

You wrote about controls for attitude control. That's the $64,000 question. Theories here so far but nothing definitive. Stay tuned.

#169 YANK63

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Posted 27 June 2012 - 11:33 AM

Well, I love a little drama and romance as much as the next guy Posted Image
Thanks for the Link !


The photo amazed me and when I read the thread about the suspicious gyro object on the mast I was hooked.
It occurred to me it must make a hell of a bang when it lets go he he Posted Image.

Looking forward to the press release and the first race ! sort of leaves F1 for dead !
Now this looks like some real fast entertainment.
Beats watching the usual crap on the telly these days after a hard day on the phones !
XOXO

#170 dogwatch

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Posted 27 June 2012 - 12:01 PM

Maybe you all have a definitive answer to the foil or hoax question now? in which case sorry for this...


Highly unlikely to be a hoax IMO. Certainly an area others have been researching.

As for your objections to the set-up you've seen, you need to follow the discussions on how AC72 rules constrain what can be done.

#171 MR.CLEAN

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Posted 27 June 2012 - 01:11 PM

It doesn't have to be false to still be a hoax. A smart strategist would simply tell their photographer to get as many shots as possible of the boat launched out of the water - there are plenty of SF days that will do that constantly. Then a controlled release to get everyone buzzing via V&V and SA means you get about 3/4 of the world's top-end racers and designers reading it at roughly the same time. Instant misinformation...

#172 SimonN

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Posted 27 June 2012 - 01:14 PM

I have been studying all the photos in great detail and believe I have it worked out! There is no ride height control system. It's automatic. I think everybody has been thinking in Moth terms, but this is something very different ebcause there isn't the need to have the feedback system in the same way. This is because of the weight of the boat and this, in turn, effects the speed that altitude would change plus how the boat reacts in waves.

The way i am pretty certain thsi all works is through the wings on the rudder. I think there is a bit of a gearing effect going on, whereby for any given increase in speed, the lift from the rudder increases at a higher rate than the lift from the main foil. This means that as the boat speeds up, the back lifts quicker, reducing the angle of attack of the main foil and this controlling the amount of lift. There are a number of problems with this, not least thatfor this to work, the rudder foils will be set at an angle that would make them rather draggy at lower speeds. i also suspect that this is why the rudder foils look small and rather strange, because if they get too big, they would lift out.

I don't believe that this approach would work on a light boat such as the Moth, where the changes in lift happen far quicker. The question would be at what size of boat would this transition occur - could it work on a beach cat such as an A Class or even an F18?

#173 Doug Lord

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Posted 27 June 2012 - 01:52 PM

I like the earlier suggestion: "Lets see the video". That might answer the steady state vs pop up theory. If it is steady state I'd bet on them having a manual altitude control system that pivots the lee daggerboard. You can't fly a foiler like this just using "built in" control from the rudder(unless all you want is to have the thing pop up now and then).Every multifoiler that uses fully submerged foils, like the AC 45 is using, has used active or manual control of the daggerboard foils.

#174 ~Stingray~

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Posted 27 June 2012 - 02:10 PM

I like the earlier suggestion: "Lets see the video". That might answer the steady state vs pop up theory.

Video would be great but by the 3 port-tack photos I am guessing they are somewhere in between, staying lifted for ten to twenty seconds at a time. Can't even begin to judge by just the one sb tack shot how that 'flight' went; perhaps it was too short for more shots.

#175 ~HHN92~

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Posted 27 June 2012 - 02:14 PM

I have been studying all the photos in great detail and believe I have it worked out! There is no ride height control system. It's automatic. I think everybody has been thinking in Moth terms, but this is something very different ebcause there isn't the need to have the feedback system in the same way. This is because of the weight of the boat and this, in turn, effects the speed that altitude would change plus how the boat reacts in waves.

The way i am pretty certain thsi all works is through the wings on the rudder. I think there is a bit of a gearing effect going on, whereby for any given increase in speed, the lift from the rudder increases at a higher rate than the lift from the main foil. This means that as the boat speeds up, the back lifts quicker, reducing the angle of attack of the main foil and this controlling the amount of lift. There are a number of problems with this, not least thatfor this to work, the rudder foils will be set at an angle that would make them rather draggy at lower speeds. i also suspect that this is why the rudder foils look small and rather strange, because if they get too big, they would lift out.

I don't believe that this approach would work on a light boat such as the Moth, where the changes in lift happen far quicker. The question would be at what size of boat would this transition occur - could it work on a beach cat such as an A Class or even an F18?


Sounds reasonable. Has it ever been tried or detailed?

#176 Xlot

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Posted 27 June 2012 - 02:18 PM

Still firmly in the dezinformatsiya camp, but to keep an open mind:

- rather than continuous ride control via daggerboard pivoting, there might be a couple of discrete settings with automatic "fine" adjustment through some surface effect (the horizontal part being barely submerged)

- Simon's "gearing" effect on the rudder tip stabilizer might be achieved through its aspect ratio - which is higher than the board's and thus makes it "bite" faster (also stall earlier, though)

#177 kiwi_jon

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Posted 27 June 2012 - 02:22 PM

It doesn't have to be false to still be a hoax. A smart strategist would simply tell their photographer to get as many shots as possible of the boat launched out of the water - there are plenty of SF days that will do that constantly. Then a controlled release to get everyone buzzing via V&V and SA means you get about 3/4 of the world's top-end racers and designers reading it at roughly the same time. Instant misinformation...


There are several videos on YT and Vimeo of the SF based SL33 BridgeRunner lifting on it's 'C' foil but it is only in the air for a couple of sec's before it settles back on the water. A single screen grab taken at that time would show the SL33 'foiling'.

Absent any sequence of photos or video of OR5 sustaining 'flight' then I stick with the conclusion I made earlier that the Oracle supplied photos show the AC45 momentarily lifting on the foils before settling back on the water.

#178 Tornado-Cat

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Posted 27 June 2012 - 02:37 PM

The way i am pretty certain thsi all works is through the wings on the rudder. I think there is a bit of a gearing effect going on, whereby for any given increase in speed, the lift from the rudder increases at a higher rate than the lift from the main foil. This means that as the boat speeds up, the back lifts quicker, reducing the angle of attack of the main foil and this controlling the amount of lift.

Humm, it could be the contrary.
In your explanation:
- the more speed the less lift on the front of the boat, in fact we want the contrary. Not to say that yours can't be right, but you would push too much water in medium.
- if you have a look at the last picture of the rudder (the one with a winglet in the middle of the rudder) you will notice a few white line that seem to indicate a neutral position and even a negative one (the planes work like that)

So, I think that:
- the rudder provides a moderate lift. The lift will be minimum, as set for high wind, knowing it only be a minor drag in light wind.
- the main foil provides a positive lift vs the rudder one, and it can be adjusted with the depth of the dagger board.
The control would be done by the twist of the sail and the depth of the main foil, the higher the wind, the higher the foil.

The diffculty being to adjust the differential between the two foils, which would explain the little with lines on the rudder. Whatever the explanation is right, something is sure, they fine tune the balance with the rudder foil and not the main.

#179 kiwi_jon

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Posted 27 June 2012 - 02:56 PM


I like the earlier suggestion: "Lets see the video". That might answer the steady state vs pop up theory.

Video would be great but by the 3 port-tack photos I am guessing they are somewhere in between, staying lifted for ten to twenty seconds at a time. Can't even begin to judge by just the one sb tack shot how that 'flight' went; perhaps it was too short for more shots.


The only thing we know about those photos is that they were taken on the 18th June. There is no indication of the time frame between photos but judging from the angles of the photos it would have to be one hell of a fast chase boat (think warp speed) to get into those three positions to take those shots in 10 - 20 sec's.

The photos could be minutes or hours apart. My guess is as good as yours.

Edit: looking at the photo info on the oracleracingmedia.com site the photos were taken over a period of 12 minutes.

#180 Xlot

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Posted 27 June 2012 - 03:04 PM

Please: it's a (horizontal) stabilizer. Winglets are totally different animals, their purpose being reducing induced drag

#181 Xlot

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Posted 27 June 2012 - 03:12 PM

It doesn't have to be false to still be a hoax. A smart strategist would simply tell their photographer to get as many shots as possible of the boat launched out of the water - there are plenty of SF days that will do that constantly. Then a controlled release to get everyone buzzing via V&V and SA means you get about 3/4 of the world's top-end racers and designers reading it at roughly the same time. Instant misinformation...


Tend to agree - but other teams' spies (how does one apply to be one, BTW?) would know immediately, wouldn't they? Wonder how many are on the Bay already, FV reported that even LR's training (and yes, foiling experiments) on their SL33 in Sardinia were 'observed'

#182 kiwi_jon

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Posted 27 June 2012 - 03:19 PM

^^^^^

Oracle had a spy (Matty Mason) in Auckland 'observing' TNZ's SL33's when they started sailing with the wing.

I suspect that the other teams will take it for what it is. A poor attempt at mis-information.

There is no doubt that the other teams are also playing with foils that will provide lift. It's not really anything new or even exciting.

Hell, even the 12 meters had wings. :lol:

#183 nroose

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Posted 27 June 2012 - 03:23 PM

I think OR released these photos and announced their foiling work because they knew all that was already known by the competition, and so they might as well get us excited, and hopefully boost the audience for Newport.

Even if it is just for 20 seconds at a time, plenty of us try to surf waves when we know we can't stay on them for long. But I am guessing they will get better than that - so many details they can change to control the flight.

I am very much looking forward to next Summer!

#184 nav

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Posted 27 June 2012 - 04:53 PM

Maybe you all have a definitive answer to the foil or hoax question now? in which case sorry for this...

But as a Moth sailor the set up in the original Voile et Voilier pictures does not look like a serious effort. First the 'L' or 'T' foil is an inefficient and structurally poor shape. It requires an adjustable flap or ability to pivot the whole foil. The only reason we use it on the Moth is to preserve our 'mono-hull' status. A curved self levelling foil would be much superior.

Second the foil is shown to be retractable. This would require any control system to be quickly detachable from the vertical foil. It's hard enough to engineer a system with the necessary strength and precision to move the foil under load without making it quick release.

Third, if you were working on foils would you not hire the world's most successful foil designer Andrew McDougall?

I can't say if they were photo-shopped or not but it doesn't look like a viable system to me - guess I'll now be proved completely wrong!

As a footnote: I was fortunate to meet Russell Coutts a year ago and offered him a go in my Mach 2 Moth - he wasn't interested.


Really though we must all be asleep - especially the SF crowd. There coulda/shouda been video of them out testing.

When I went looking for webcams to check out the fire - I watched ORTUSA5 sail right across the frame. There was no 'secret testing' surely, just a bunch of unobservant/disinterested people.

Too late to do anything now though I guess.

#185 dogwatch

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Posted 27 June 2012 - 06:02 PM

Fisher's View: Day minus 3 ACWS Newport - The Elephant is in the Room
http://www.sail-worl...-the-Room/98938


Then the matter of hydrofoils reared its ugly head. Oracle Team USA has been trialling on of its AC-45s with L-shaped daggerboards and T-foiled rudders in San Francisco with some success. It also has a backlog of experience gained in the development of USA-17, the 90-foot waterline catamaran that won the 33rd America's Cup. Whether other teams have similarly experimented is not known, but all the AC-72 design teams will have been evaluating the theories. Those theories are certain to be transformed into practicality.

So for those who believe this is a hoax, is Fisher 1. a gullible fool or 2. a knowing vehicle of OR disinformation?

#186 Börni

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Posted 27 June 2012 - 06:26 PM

Found something interesting. Look at the picture of the foiling AC 45 on Jimmies Facebook entry . See this little extension on the downside of the windward foil. Just a fence?? The official picture of Oracle don't show that. They must be photoshopped to hide something???

Attached Files



#187 bluelaser

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Posted 27 June 2012 - 06:28 PM

You're right, Good catch. The fence in the middle and the bubble on the vertex of the L are missing in the official pic.

Here is the official pic for comparison again:

Posted Image

#188 Monster Mash

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Posted 27 June 2012 - 06:39 PM

^

Love this site.

#189 ~Stingray~

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Posted 27 June 2012 - 06:48 PM

^ Holy Carumba's, you're right!

From Jimmie's FB version:

Posted Image

#190 Xlot

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Posted 27 June 2012 - 07:00 PM

Very good indeed! Wonder why they took the trouble of photoshopping out the acorn: it's so obvious as a means to minimize interference drag (Moths have it, FFS) that its omission actually draws attention to the part.

The "fence" is more interesting - but shouldn't it be on the foil's upper side? Would match the hypothesis of near-surface operation

#191 ~Stingray~

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Posted 27 June 2012 - 07:05 PM

We've actually seen an acorn before; but not the fence; was some time back, could have been a different board

#192 porthos

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Posted 27 June 2012 - 07:19 PM

Very good indeed! Wonder why they took the trouble of photoshopping out the acorn: it's so obvious as a means to minimize interference drag (Moths have it, FFS) that its omission actually draws attention to the part.

The "fence" is more interesting - but shouldn't it be on the foil's upper side? Would match the hypothesis of near-surface operation


Is it possible those things were photoshopped *in* to the photo on JS's page (i.e., the acorn and fence are not actually there and that the original photo posted is the true one)?

#193 nav

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Posted 27 June 2012 - 07:22 PM

Ahhh but...photoshopped out - or photoshopped in?! Posted Image

A secret - hidden in an enigma etc etc

Edit - Great mind Porthos

#194 Tony-F18

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Posted 27 June 2012 - 07:26 PM

What about this shot?
Does look like a bit of a pod, but no fin halfway...
Posted Image

#195 Xlot

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Posted 27 June 2012 - 07:29 PM

Great mind Porthos


:lol: :lol:

#196 bluelaser

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Posted 27 June 2012 - 08:33 PM

Photoshopped out.

If you zoom way in on the windward board in this photo, you will notice what looks like a heat refraction off the bottom of the board. Most likely that is where someone chopped out the fence and Acorn:

http://www.sail-worl...SFOJUN33121.jpg

#197 Tornado-Cat

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Posted 27 June 2012 - 09:09 PM

When I see this last picture it seems to confirm that the rudder has a smaller lifting effect than the main foil, so the pitch would be controlled by the depth of the main one.

If there is an hoax it would be the bigger one at the bottom of the rudder. How can the rudder work efficiently if out of the water ?

#198 Doug Lord

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Posted 27 June 2012 - 09:18 PM

When I see this last picture it seems to confirm that the rudder has a smaller lifting effect than the main foil, so the pitch would be controlled by the depth of the main one.

If there is an hoax it would be the bigger one at the bottom of the rudder. How can the rudder work efficiently if out of the water ?

====================
On most multifoilers, the rudder load at takeoff is about 20% of the total and gets less with speed...
-----
Congrads to Borni for spotting the "thing" under the windward foil-most definitely something fishy going on somewhere-just not sure where yet....

#199 Tornado-Cat

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Posted 27 June 2012 - 09:33 PM


When I see this last picture it seems to confirm that the rudder has a smaller lifting effect than the main foil, so the pitch would be controlled by the depth of the main one.

If there is an hoax it would be the bigger one at the bottom of the rudder. How can the rudder work efficiently if out of the water ?

====================
On most multifoilers, the rudder load at takeoff is about 20% of the total and gets less with speed...
-----
Congrads to Borni for spotting the "thing" under the windward foil-most definitely something fishy going on somewhere-just not sure where yet....

Then, do you think the "winglet" would be to help taking off ?

#200 Koukel

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Posted 27 June 2012 - 09:40 PM

If heel is to leeward and the angle of the L is slightly less than 90 degrees, then the tip of the lifting foil would break the surface and reduce lift progressively. Spitty could adjust his height with more or less heel as well as more or less speed.

That's my guess.

Koukel




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