Recon diary

The_Alchemist

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By exactly the same metric LR have just as much chance of being in the same doom spiral as INEOS if their boat is slower, you couch the LR proposition as interesting, whereas is INEOS- doomed to fail
Really? LR is zipping around all over the place and INEOS looks like a bucking bronco and can barely stay on their foils.
 

Stingray~

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Really? LR is zipping around all over the place and INEOS looks like a bucking bronco and can barely stay on their foils.
Are you really willing to get into a sh*tfight with JAL for stating the obvious? ;D

Allison and his AMG crew must still be scratching their heads, being used to flat tracks instead.
 

The_Alchemist

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Can you pump liquid into the foils to increase their cross section? With no liquid it becomes a super cavitating foil?
Like I talked about earlier. No pumping needed.

The leading edge of the foil could be filled with a fluid that holds it to the rounded shape of a typical foil. When at speed, a value could be opened (or pressure activated) and the fluid would be pushed back into reservoirs in the foil or foil arm. The leading edge of the foil distorts into a cutting edge that is defined by some framework within the foil … from ( to < …. The fluid reservoir could be under pressure such that it would flow back into the cutting edge and reform the original shape when the boat slows down to a certain speed.

The idea is to try to transform a normal foil into a supercavitating foil when the boat reaches the speed where it could use it.

Another idea is maybe just parts of the foil length are shaped as supercavitating (Zones), would that work?

That is my rough brain fart, what do you guys think?
 

Stingray~

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Like I talked about earlier. No pumping needed.

The leading edge of the foil could be filled with a fluid that holds it to the rounded shape of a typical foil. When at speed, a value could be opened (or pressure activated) and the fluid would be pushed back into reservoirs in the foil or foil arm. The leading edge of the foil distorts into a cutting edge that is defined by some framework within the foil … from ( to < …. The fluid reservoir could be under pressure such that it would flow back into the cutting edge and reform the original shape when the boat slows down to a certain speed.

The idea is to try to transform a normal foil into a supercavitating foil when the boat reaches the speed where it could use it.

Another idea is maybe just parts of the foil length are shaped as supercavitating (Zones), would that work?

That is my rough brain fart, what do you guys think?
It's a great discussion, if the rules do allow things as radical as this.

JAL posted a nice graphic showing just how different 'normal' foils are from the super-cavitation shapes and yes, it's a bit daunting.

The leading edge could maybe be done in a fashion you describe; and to get the vertical trailing edge, maybe the flaps could retract to inside the foil? Perhaps in concert with the pressure activation you imagined, for the leading edge.
 

buckdouger

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It's a great discussion, if the rules do allow things as radical as this.

JAL posted a nice graphic showing just how different 'normal' foils are from the super-cavitation shapes and yes, it's a bit daunting.

The leading edge could maybe be done in a fashion you describe; and to get the horizontally-vertical trailing edge, maybe the flaps could retract to inside the foil?
Don't forget while all of this stuff is going on the foils need to be not much bigger than is absolutely necessary, must have sufficient structure to hold the yacht up, and possibly carry some ballast. Within the constraints of the rule, the use case of the boats, the types of materials and equipment generally available, I'm afraid it's probably out of reach.
 

Stingray~

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Don't forget while all of this stuff is going on the foils need to be not much bigger than is absolutely necessary, must have sufficient structure to hold the yacht up, and possibly carry some ballast. Within the constraints of the rule, the use case of the boats, the types of materials and equipment generally available, I'm afraid it's probably out of reach.
Generally agree but there may well be degrees of morphing achievable through cleverness, to at least postpone the cavitation onset. You'd have to worry about the rudder foil too.
 

Stingray~

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Another dimension of course might be to 'allow' the foil junction to not be 90 to the arm.
 
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buckdouger

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Would there be any benefit to 'allowing' the foils to rake aft, under pressure?
There is some merit to this. I've seen a few papers that suggest the onset of cavitation for a swept foil is delayed similarly to swept wings and shockwaves, as you'd maybe guess. I've also previously looked for rules that prevent the main wing from pivoting and I'm not sure it's banned, the hinge rules at least deal only with the flap.
It would change the balance fore, aft; it takes away design flexibility at the junction to the bulb.
I'd struggle to imagine teams had not thought of this and ruled out out so maybe there are rules in other sections e.g. control that rule it out, or the benefits or practicalities render it undesirable.
 

Stingray~

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There is some merit to this. I've seen a few papers that suggest the onset of cavitation for a swept foil is delayed similarly to swept wings and shockwaves, as you'd maybe guess. I've also previously looked for rules that prevent the main wing from pivoting and I'm not sure it's banned, the hinge rules at least deal only with the flap.
It would change the balance fore, aft; it takes away design flexibility at the junction to the bulb.
I'd struggle to imagine teams had not thought of this and ruled out out so maybe there are rules in other sections e.g. control that rule it out, or the benefits or practicalities render it undesirable.
Makes sense.

For an even more 'far out there' possibility, as well as pivoting to it could the foil wing junction elevate up and down the arm?
 
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Dogfish

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I don't see cavitation as a problem in Barcelona. AM at 50kts should be at the boundary and experiencing the start of some cavitation. However it seems you can go a bit faster than initially though before cavitation becomes a problem. With the sea state I suspect some of these super fast sections in flat water may not be as fast as expected. I think TNZ have made a tactical blunder and negated a lot of their advantage by going to Barcelona. It's going to be really interesting that's for sure.
 
I don't see cavitation as a problem in Barcelona. AM at 50kts should be at the boundary and experiencing the start of some cavitation. However it seems you can go a bit faster than initially though before cavitation becomes a problem. With the sea state I suspect some of these super fast sections in flat water may not be as fast as expected. I think TNZ have made a tactical blunder and negated a lot of their advantage by going to Barcelona. It's going to be really interesting that's for sure.
we love interesting cups.
 

enigmatically2

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and how is any of this rule compliant?
Not in the slightest as you know (unless you want to take a Russian attitude to truth). For others, rules include:

10.1
Each foil shall comprise only:
(a) one foil arm and one foil wing, which shall be connected to each other according to a detail provided
within the foil arm stock specification.
(b) one foil flap; and
(c) one or more foil systems.

10.6 The only foil arm movement permitted relative to the hull is cant, being a rotation about the foil arm cant
axis, a longitudinal axis whose position is defined in Figure 10.2.

10.10
10.10 Control surface actuators are permitted within foil systems to rotate foil flaps about the axis described in
Rule 13.11. Any deformation in the foil resulting from this actuation is restricted by Rule 13.14. No other
devices are permitted to modify the shape of a foil.

13.9 The chord length of a foil flap shall be no more than 50% of the chord length of the foil.

13.14 The cross‐sectional shapes of the foil wing and foil flap shall lie within ±2.0 mm of their blueprint’s local
cross‐section, except over the surface of any foil flexure, to be satisfied:
(a) at any cross‐section through a foil perpendicular to the local foil flap hinge axis;
(b) for all foil flap rotation angles and twists; and
(c) in the absence of external forces except gravity.
 

shebeen

Super Anarchist
We all (I think) agree the double track and the leech control is worth it. But why not let it slide across controlled via a rope to centre-line?
The gain of that is what seems marginal
agreed, something like my orange line should work (obviously with the negative purchase required in practice) without needing to square up the slider on the tracks?

1675675109380.png


maybe something more going on here
 

Mozzy Sails

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The problem with the orange is that when the jib sheet is anywhere but dead central and aligned with the orange it will torque the car on the tracks and jam.

They could maybe do a more elaborate job with the tracks to resit that torque. But you'd have to weight up the weight and friction of more sets of bearing / rollers versus this set up.

I sailed a merlin this weekend which is a 3D jib angle adjuster (not self tacking). But one problem with the system was that it twisted and became hard to move using only a central puller.
 

shebeen

Super Anarchist
The problem with the orange is that when the jib sheet is anywhere but dead central and aligned with the orange it will torque the car on the tracks and jam.

They could maybe do a more elaborate job with the tracks to resit that torque. But you'd have to weight up the weight and friction of more sets of bearing / rollers versus this set up.

I sailed a merlin this weekend which is a 3D jib angle adjuster (not self tacking). But one problem with the system was that it twisted and became hard to move using only a central puller.
i defer to your significant knowledge/experience then!
 


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