Tornado-Cat

Boats and foils comparison

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38 minutes ago, The_Alchemist said:

I guess the US Navy should never have used the F-14 Tomcats fighter jets.  It was designed to produce about 40% of its lift from the fuselage for better survivability.  

Reference? Here's what the bottom of an F-14 looks like. Even without the appendages, there's not a lot of lift from that at sub–sonic speeds.

F14Flying.jpg

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22 minutes ago, Lickindip said:

F-14 are designed to go over Mach2, have space for 2 massive engines and a heap of armement as well as no requirement to be in contact with the ground or water to cantalever their flying ability ... extreamly useful to compare lifting bodies usefullness ay

have a crack at the below puzzle, (add your own dimensions and forces in)

if your hull is a 'lifting' (positive being up) body [orange force], then you will need to de-power your rig [blue force] earlier then any other boat who has zero lift or negative lift

You run a slightly larger risk of the hull pivoting around the water foil in a good gust of wind. But on the other hand, you will fly slightly longer and faster especially when the wind drops. Pay your money and take your choice.

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FIFY.......

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41 minutes ago, The_Alchemist said:

You sure have drank the hometown kool-aid.  Every assumption you make is that the NZ design is better.  I know you want to believe they have the most advanced design, have the greatest ideas and are never wrong, but that possibly may not be the case.  You do know that a hull that doesn’t touch the water has less hydro drag than one that “bounces” off the water?

Really?

Have I?

The only assumptions being made here are by you. I am not a Kiwi, not in Auckland, nor do I support them as a team. Admire their achievements and approach; that's all. But if that upets your sensitivities then I apologise. You must be insecure about stuff.

Thanks for the insightful bit at the end. I am much enlightened for that...... 

You must have missed the word - inevitable.

Oh, and please do continue with jet fighter analogies, because they are so relevant.

Why not throw in some small animal vetinary science analogies, because that would be just as valid.....

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as sidecar estimated above 50knts could mean 1750kg's lift

if hull weight is around 6.5T (65000N)

arms are 245kg (2450N)

Foils are 970kg (9700N)

lets just combine arms and foils and use 3.5m radius from the below figure,

so to pivot and balance forces :

from pivot to hull center is approx 5m

from pivot to center of mass on canterlever foil is approx 10.5m

so hull weight is causing  65000x5 = 325000nm

canterlever foil is causing (2450+9700)x10.5 = 127575nm

for a total of 452575nm which would be balanced by the wind reaction in the sail

if the hull was creating a lift of 1750kg (17500N) at 5m, 87500nm less force on the sail

thats 19% less wind reaction force you could generate at 50knts

someone feel free to put more exact numbers into a spreadsheet

i can tell you that i would be designing for downforce ... but hey im not employed by any of the teams so guess this is just an opinion :D

image.png.15160061f307964044f022e68159f29c.png

 

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19 minutes ago, Lickindip said:

have a crack at the below puzzle, (add your own dimensions and forces in)

if your hull is a 'lifting' (positive being up) body [orange force], then you will need to de-power your rig [blue force] earlier then any other boat who has zero lift or negative lift

You run a huge risk of the hull pivoting around the water foil in a good gust of wind

Lift from the hull also means less lift required from the foil, so less drag. Which one is better for which boat in what conditions?

The point is that it's not a simple equation of hull lift == good or bad and no one here has the data, software or ability to determine how much lift each hull creates or whether it's better or worse than less lift. I think foils, rig and sailing ability matter far more than effects with minuscule impacts like aero dynamic lift from the hull.

 

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1 hour ago, The_Alchemist said:

I guess the US Navy should never have used the F-14 Tomcats fighter jets.  It was designed to produce about 40% of its lift from the fuselage for better survivability.  

Lol that has nothing to do with AC75s...seriously. This forum is getting ridiculous 

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It is going to be interesting, once teams are sailing "their best" after more months of practice and design refinement, to look at them race and then think back to the ACA predictions.

 

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1 hour ago, The_Alchemist said:

F-14 Tomcats fighter jets.

Beautiful plane. I saw a couple in the flesh when the Constellation visited Sydney. Sadly they were just deck ornaments and non operational.

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32 minutes ago, RobG said:

Lift from the hull also means less lift required from the foil, so less drag. Which one is better for which boat in what conditions?

The point is that it's not a simple equation of hull lift == good or bad and no one here has the data, software or ability to determine how much lift each hull creates or whether it's better or worse than less lift. I think foils, rig and sailing ability matter far more than effects with minuscule impacts like aero dynamic lift from the hull.

 

i think it is possible for us to do simple calcs and use extremes either way as examples to come up with concept dirrection

the above calc shows that at 50knts a 1750kg lifting body (if thats possible) [lift = drag which we will ignore for now] vs a zero lift body [minimal drag] would have a 20% moment difference for the sail to work with

would a rig that can only produce 80% rig moment of the boat next to it even get up to 50knts? and then there is the extra drag factor of the hull in the air

unless ive f'd up the calcs bigtime this is not a 1-2% argument that suposibly could give an advantage this is 20%

if your F_LAT ability is reduced then your F_R is reduced ... this is an americas cup boat, surely maximising F_R is right up there on the priority list

you dont see to many V6 engines in a V8 Race do ya :lol:

image.png.92e44a55a5edb41b1603d55663c10022.png

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So you're saying they want downforce from the hull to increase RM? Seems reasonable from my armchair given the flat deck vs curved bottom and why bow–down attitude is often used at higher speeds.

But if downforce is generated by bow–down pitch, the main foil AoA is reduced so more flap is needed to generate lift to counteract it. But the boat is also going faster, so maybe not so much. Not a simple set of equations… :blink:

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From my armchair, I’d say they’d be looking for downforce not from the hull’s (inverted) profile, but from the Venturi “ground” effect, like F1 cars. Except that those have the rear diffuser and wing to energize it

 

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12 hours ago, RobG said:

So you're saying they want downforce from the hull to increase RM? Seems reasonable from my armchair given the flat deck vs curved bottom and why bow–down attitude is often used at higher speeds.

But if downforce is generated by bow–down pitch, the main foil AoA is reduced so more flap is needed to generate lift to counteract it. But the boat is also going faster, so maybe not so much. Not a simple set of equations… :blink:

depends on how the teams have gone about designing the basic principles of the boat.

I assume that ETNZ has learnt about bow up vs down benefits from the last cup.

if I were in their shoes id design the boat sitting in an upwind configuration (most wind over the decks), in the expected sweet spot wind conditions for cup match and have it sitting there at the predicted speed and angle. align all the equipment foils/windange/force vectors/bowdown to where they were best suited in that scenario. that would be the drag race condition we will see in the cup.

maneuver time, getting on to foils etc are only a small % of race time and can be effected by crew skill and timing massivly

what i'm assuming oracle and Artemis did in the last cup was "how fast can we make this thing go on in a straight line"

 

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I think overall you want zero lift from the hull, because once the boat is foiling it is mostly a drag device and any lift, independent of direction, will predominantly add to that drag. It neither has the profile shape nor the aspect ratio to be efficient as a wing.

I believe it can be used effectively to improve the aerodynamics of the sails, but that is about it. Any change in attitude will focus on minimizing drag and optimizing the performance of the sails.

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I expect the COR and ETNZ will set a time limit for a race in light air so that a boat foiling down wind but not upwind will be able to finish.

So the time spent semifoiling upwind will be more than half the time and will be a match winner.

Also if a boat can get up onto the foils half a knot earlier, it will mean a big lead for the foiling speed to make up?

So, for me, any help the hull can make to getting up and foiling is a big factor worth some loss of top speed?

 

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I think you're right, be interesting to see if the time limit is based on fitting into a TV time slot or on what gives enough time for a fair race at an average VMG of say 15 knots?

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1 hour ago, Kiwing said:

I expect the COR and ETNZ will set a time limit for a race in light air so that a boat foiling down wind but not upwind will be able to finish.

So the time spent semifoiling upwind will be more than half the time and will be a match winner.

Also if a boat can get up onto the foils half a knot earlier, it will mean a big lead for the foiling speed to make up?

So, for me, any help the hull can make to getting up and foiling is a big factor worth some loss of top speed?

 

This gets down to the overall solution of reducing drag over the whole race is greater than optimizing drag in some portions of the race (VMG can be used in place of drag).  Basically, a boat that can transition the quickest to foiling (either fast up or at lower winds) can overcome some additional drag while foiling.

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20 hours ago, uflux said:

Lol that has nothing to do with AC75s...seriously. This forum is getting ridiculous 

You started it with following the stupid comment

"The lifting body theory is bullshit...."

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21 hours ago, RobG said:

Reference? Here's what the bottom of an F-14 looks like. Even without the appendages, there's not a lot of lift from that at sub–sonic speeds.

F14Flying.jpg

It is not so much about the bottom of the plane as it is about the top of the plane.  ( used https://physics.weber.edu/schroeder/fluids/ for fluid charts)

F14 tomcat.jpg

f14flow3.jpg

f14 flow1.jpg

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Drag reduction is important, but somehow the implication that an airborne “scow” produces more drag than a “skiff” is possibly false. Increased drag comes from a “foil” being increasingly asymmetric and/or an AoA being increasingly greater than 0 degrees.

if you look at all these boats at 10-15 degrees off the bow, the same angle as the apparent wind sees it, they are all asymmetric “foils” the air has to go either over/under or around the sides.. in this case, I would suggest that it is less drag to push the air under/over than around, with the additional benefit that it also might produce some lift and cleaner airflow to the bottom of the sails.

To sail nose down, unless there is some other overriding benefit is an increase of AoA and should be more drag, with the boat is pointing in the wrong direction in the event of a splashdown.

No doubt in my mind that American Magic is the slickest boat of the bunch in terms of drag, InEOS is next, with out knowing how much “channeling” benefit there is, and Luna Ross the most draggy, not withstanding it’s slick tail, because of its higher, more vertical bow sections....

What happens at the bow sections, where the apparent wind hit first is key......  and they are all pretty much the same at the back (InEOS fins excepted).

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22 minutes ago, Sidecar said:

Drag reduction is important, but somehow the implication that an airborne “scow” produces more drag than a “skiff” is possibly false. Increased drag comes from a “foil” being increasingly asymmetric and/or an AoA being increasingly greater than 0 degrees.

if you look at all these boats at 10-15 degrees off the bow, the same angle as the apparent wind sees it, they are all asymmetric “foils” the air has to go either over/under or around the sides.. in this case, I would suggest that it is less drag to push the air under/over than around, with the additional benefit that it also might produce some lift and cleaner airflow to the bottom of the sails.

To sail nose down, unless there is some other overriding benefit is an increase of AoA and should be more drag, with the boat is pointing in the wrong direction in the event of a splashdown.

No doubt in my mind that American Magic is the slickest boat of the bunch in terms of drag, InEOS is next, with out knowing how much “channeling” benefit there is, and Luna Ross the most draggy, not withstanding it’s slick tail, because of its higher, more vertical bow sections....

What happens at the bow sections, where the apparent wind hit first is key......  and they are all pretty much the same at the back (InEOS fins excepted).

2D96EE73-B627-4334-81B9-C2907B9311BF.jpeg

0CE41529-938D-46D7-B5F8-F30DB004233E.jpeg

FB403D7C-BBBF-4030-A154-52248C42E8B0.jpeg

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I agree except about the importance of the bow for drag. The airflow at the stern of the boat is far more important than the bow section. As the ability for the airflow to re-connect at the stern. Rather than spill off as vortices will have a much greater affect on the total drag than the bow. 

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As I said in my earlier post, InEOS Cadillac fins (they must have justifying reasons) excluded, they are all pretty much the same at the back, so that leaves the leading edge..... and thickness and general form.

Another major drag factor is foil thickness and frontal area at ~10-15 degrees AWA. Longitudinally, they are all pretty much the same. Above the static waterline, minimum ~ central freeboard is 1.5 m and all the “boats” should  be the same. But they are not. Three have shallow dips of say 0.1 m. InEOS due to the tunnel has nearly 2/3 of its “freeboard” some 0.6 m lower. So above static waterline, even if you average them out, InEOS’ effective height is some 0.3 m lower. Below the static waterline, the protuberances of the skiffs add, (say) another 0.3 m to the overall AWA foil thickness.

So as an indication in terms of least overall thickness drag it is InEOS least, then Magic, and then pick between the “skiffs”.

Looking at sectional slices through the “boats” at~ 10- 15 degrees AWA, a number of things are noticeable:

Below static waterline, the “scows” are as clean as you could hope for. The “skiffs” have protuberances disturbing airflow, one with a keel ridge..

Above deck leading edges at the bow the “skiffs”  are more blunt, the “scows” have sharper/ more rounded entries.

Hence my overall rating earlier with a big caveat on InEOS. And then there is lift, and ground effect, as Brett Bakewell White has publicly suggested,  but I won’t go there again.

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1 hour ago, Sidecar said:

As I said in my earlier post, InEOS Cadillac fins (they must have justifying reasons) excluded, they are all pretty much the same at the back, so that leaves the leading edge..... and thickness and general form.

Another major drag factor is foil thickness and frontal area at ~10-15 degrees AWA. Longitudinally, they are all pretty much the same. Above the static waterline, minimum ~ central freeboard is 1.5 m and all the “boats” should  be the same. But they are not. Three have shallow dips of say 0.1 m. InEOS due to the tunnel has nearly 2/3 of its “freeboard” some 0.6 m lower. So above static waterline, even if you average them out, InEOS’ effective height is some 0.3 m lower. Below the static waterline, the protuberances of the skiffs add, (say) another 0.3 m to the overall AWA foil thickness.

So as an indication in terms of least overall thickness drag it is InEOS least, then Magic, and then pick between the “skiffs”.

Looking at sectional slices through the “boats” at~ 10- 15 degrees AWA, a number of things are noticeable:

Below static waterline, the “scows” are as clean as you could hope for. The “skiffs” have protuberances disturbing airflow, one with a keel ridge..

Above deck leading edges at the bow the “skiffs”  are more blunt, the “scows” have sharper/ more rounded entries.

Hence my overall rating earlier with a big caveat on InEOS. And then there is lift, and ground effect, as Brett Bakewell White has publicly suggested,  but I won’t go there again.

nice, also a rounded front edge has a lower drag coefficient than pointed edge (half sphere vs cone)

drag3.png

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2 hours ago, Sidecar said:

As I said in my earlier post, InEOS Cadillac fins (they must have justifying reasons) excluded, they are all pretty much the same at the back, so that leaves the leading edge..... and thickness and general form.

Another major drag factor is foil thickness and frontal area at ~10-15 degrees AWA. Longitudinally, they are all pretty much the same. Above the static waterline, minimum ~ central freeboard is 1.5 m and all the “boats” should  be the same. But they are not. Three have shallow dips of say 0.1 m. InEOS due to the tunnel has nearly 2/3 of its “freeboard” some 0.6 m lower. So above static waterline, even if you average them out, InEOS’ effective height is some 0.3 m lower. Below the static waterline, the protuberances of the skiffs add, (say) another 0.3 m to the overall AWA foil thickness.

So as an indication in terms of least overall thickness drag it is InEOS least, then Magic, and then pick between the “skiffs”.

Looking at sectional slices through the “boats” at~ 10- 15 degrees AWA, a number of things are noticeable:

Below static waterline, the “scows” are as clean as you could hope for. The “skiffs” have protuberances disturbing airflow, one with a keel ridge..

Above deck leading edges at the bow the “skiffs”  are more blunt, the “scows” have sharper/ more rounded entries.

Hence my overall rating earlier with a big caveat on InEOS. And then there is lift, and ground effect, as Brett Bakewell White has publicly suggested,  but I won’t go there again.

That is a very inefficient rear end. Particularly if you take into account the apparent airflow angle over the hull. High surface area drag and a whole lot of turbulence from its box structure  All the other ac75s have a much neater stern. Ineos looks like a dogs breakfast :blink:

F22D0388-5C93-4D0A-94EC-C7001994EB2C.jpeg

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8 hours ago, Sidecar said:

To sail nose down, unless there is some other overriding benefit is an increase of AoA and should be more drag, with the boat is pointing in the wrong direction in the event of a splashdown.

Side, can you just clarify what you exactly meant in this statement?

Are you referring to the AoA on the Hull Structure or the AoA of the main Hydrofoil?

Because if you are referring to the hull structure, then yes, going nose down will increase its AOA on the hull but correspondingly, reduce the AOA on the foil, possibly moving it into a lower angle of incidence and allowing the whole foil package to either run less flap or possibly smaller flaps, smaller foils or all three, also possibly allowing a slimmer foil section to be utilised, where otherwise a high lift, thicker sectioned foil might be needed to achieve similar  lift drag characteristics ( but not be trimmed out by going nose down). 

Furthermore, whilst nose down would in essence be dragging the hull structure through the air at an even more oblique angle than if level, if this in someway channels, scoops or directs a greater mass of air flow over the bottom of the rig, then is the global gain outweighed by the seemingly odd attitude of the hull structure?

You can disappear down the rabbit hole by considering every single loss and gain that flying these machines in 6 axis of freedom causes. But the teams need to unpick these essentials.

One thing is for sure - Fighter jet analogies are completely hatstand..... So expect to see plenty more of those from Cock Wombles.

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AoA of hull structure...........

I can see the wind scoop analogy. But maybe the scows scoop sufficiently horizontally, especially in the case of InEOS, where it is scoop and channel.

We are all talking in simplistic terms, the reality and overall effects are much more complex and can only really manifest them selves with computer simulation/tunnel testing which we shall never see at least not until it is all well and truly over.

Interesting times.............

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7 hours ago, uflux said:

That is a very inefficient rear end. Particularly if you take into account the apparent airflow angle over the hull. High surface area drag and a whole lot of turbulence from its box structure  All the other ac75s have a much neater stern. Ineos looks like a dogs breakfast :blink:

How dumb and stupid of them when it is so obvious to you.............

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12 hours ago, uflux said:

That is a very inefficient rear end. Particularly if you take into account the apparent airflow angle over the hull. High surface area drag and a whole lot of turbulence from its box structure  All the other ac75s have a much neater stern. Ineos looks like a dogs breakfast :blink:

F22D0388-5C93-4D0A-94EC-C7001994EB2C.jpeg
81FC2653-9941-4C19-A8C0-F23EEB4AEB55.thumb.jpeg.9b82500650ddbf716354a517190b14df.jpeg


 

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5 hours ago, Sidecar said:

How dumb and stupid of them when it is so obvious to you.............

Like everything it’s a compromise. I think they have compromised too much. Every evolutionary system has a dead end...But time will tell.

AFD51279-8979-4B20-8244-E0A7B51FCF25.jpeg

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I think you are missing out on the fact that the angle of AoA of the Hull and AoA of the foils don't have to align.

depending on the team's direction they would have the set up the sweet spot AoA of the foil/rudder combo and hull independently then fixed them together in the Arm joint. you would have to assume the teams would have some sort of adjustment of the whole foil incidence can be changed easily else they will have to have a slight positive or negative flap on which wouldn't be beneficial (maybe that's what why saw the guy sitting out on the arm the other day?)

because some above don't like the analogy of jet fighters ill go old school and go free flight model aircraft

tailplane (Yacht Rudder Foil equiv) usually set at zero incidence, wing (yacht main foil equiv) set at +3 degrees, thrust line -2 down (and a couple of degrees right for torque). the hull or fuze is fairly irrelevant except for looks

it takes a lot to fine adjust each angle against each other, you want the best climbing when under power but and efficient glide when power runs out

 

image.png

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6 hours ago, Lickindip said:

because some above don't like the analogy of jet fighters ill go old school and go free flight model aircraft

Good. Agree with much of what you say. My Beef with the Jet fighter analogies is that they are designed for a performance envelope that does not translate to that which these boats are encountering. The Air speed, altitude, force, turbulance (either surface effect or  and reynolds numbers do not make for transference. They are designed for high sub sonic and supersonic performance with wing profiles to suit both in profile and plan shape.

Performance Gliders have much greater transference, and their techology and design is of much greater relevance.  Carry on.

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2 hours ago, Boink said:

Good. Agree with much of what you say. My Beef with the Jet fighter analogies is that they are designed for a performance envelope that does not translate to that which these boats are encountering. The Air speed, altitude, force, turbulance (either surface effect or  and reynolds numbers do not make for transference. They are designed for high sub sonic and supersonic performance with wing profiles to suit both in profile and plan shape.

Performance Gliders have much greater transference, and their techology and design is of much greater relevance.  Carry on.

The only reason I brought up the F14 was to respond to the comments by uflux that lifting bodies theory was BS.  I didn't say it was applicable to the AC75.

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1 hour ago, The_Alchemist said:

The only reason I brought up the F14 was to respond to the comments by uflux that lifting bodies theory was BS.  I didn't say it was applicable to the AC75.

the lifting body is BS, its quite clear to see by basic calculations that IF a hull was to produce +ve lift then you would minimise the effective righting moment ... faster you go the worse it gets.

you effectively need to de-power your rig the more lift is produced by the hull. so you are creating a brick wall you cant push through

on the flip side if you produce -ve lift from the hull, the faster you go the more righting moment created and the more power you can put through the sails.

 

 

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On 12/17/2019 at 1:52 PM, Lickindip said:

i can tell you that i would be designing for downforce ... but hey im not employed by any of the teams so guess this is just an opinion 

You're right & thanks for doing the calcs.

We had this argument around here since TNZ started fairing up the first AC72.

 

Initially they were using angles that would generate positive lift, inefficiently but less draggy than no fairing.

But the ultimate version was clearly an inverted aerofoil that must have been producing pretty significant down-force = righting moment.

If I recall Orifice had a more neutral fairing but tending towards down-force.

 

That became more clear-cut with the AC50s: less freedom in fairing shape but they all ran aggressive bow-down.

Admittedly a key part of that was gaining righting moment on the windward rudder foil but the fairings will have contributed something as well.

 

There's no windward rudder available for JC75s but the team who has done the most sailing is continuing the aggressive bow-down attitude & that has to be for a reason.

 

I think the lift boosters are arguing hull lift = less lift needed from the foils = less foil AoA/flap/area needed = less hydro drag.

But as soon as these things take off you're going to immediately be reducing AoA/flap/area anyway and hull aero lift can't help with that initial takeoff while the bottom is in the water.

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Precisely,

rumor was ETNZ in AC50 were twisting their hulls so the windward rudder foil was creating more downforce by a hundred + kg's then other teams

this gave the more righting moment so could use that in their sails

why would the AC75 be any different with requiring max righting moment?

everyone was moaning about the widths of the boat being different even though the pivot points of the Foil Arms is +- 2mm

 

why is hull +ve lift not justifiable to help with foil lift

what would be more efficient for creating vertical lift ...

1: a pure design high aspec small wing submerged in a medium 800x the density of air

2: a compromised blob of no aspec what so ever used to house 11 working people, has volume requiements in the bow and sides incase of capsize, mounts a mast and sails and has all sorts of angles airflow over .

 

foils are designed to foil and hulls are designed to be hulls, make them efficient in what they do best and don't compromise

 

 

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1 hour ago, Foolish said:

We finally see what happens when the lack of a keel becomes important:

https://www.sailingscuttlebutt.com/2019/12/18/video-americas-cup-boat-tips-over/

Actually the keels it has (plus a large diameter mast section with a sealed section in the top) appear to have very successfully prevented it from turning upside down, exactly as planned.

I'm actually amazed at how completely undramatic that capsize and subsequent recovery was.  It looked about as bad a kid falling over in a Laser and then being helped back up by an instructor.

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Ya, but I can just see the start box of a match race, where the sole goal is to get the other boat to drop.  Race over before it starts.

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2 hours ago, Foolish said:

Ya, but I can just see the start box of a match race, where the sole goal is to get the other boat to drop.  Race over before it starts.

Plenty of AC races have already effectively been won in the start box, in a variety of ways, this is nothing new.

From what we have seen so far from ETNZ it's almost certainly still going to be easier to effectively win the race in the start box by locking someone out at the pin or commitee boat or simply penalising them than deliberately tipping them over.

Not saying it's not a valid tactic and can't be used to some degree, but if your the boat that is likely to go over surely your just going to prevent a capsize and take a penalty.

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2 hours ago, Foolish said:

Ya, but I can just see the start box of a match race, where the sole goal is to get the other boat to drop.  Race over before it starts.

Sir Ben should be a natural.

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Does somebody knows what it is ? (from the foilingweek fb page).

That looks like a foiling mono to me, with selfrighting possibility :)

Don't know if it worked well but some old inventions are worth revisiting sometimes with newer, stiffer, stronger material.

79820038_1492018494308014_3234756556012650496_o.jpg.2f614835afddc4a706a20b17971ee386.jpg

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cant see much buoyancy

just a couple of alloy tubes

probably a bitch to get off the water .... but then

looks like it would fly

i like the single foil design

 

 

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4 hours ago, Tornado-Cat said:

Does somebody knows what it is ? (from the foilingweek fb page).

That looks like a foiling mono to me, with selfrighting possibility :)

Don't know if it worked well but some old inventions are worth revisiting sometimes with newer, stiffer, stronger material.

79820038_1492018494308014_3234756556012650496_o.jpg.2f614835afddc4a706a20b17971ee386.jpg

Well it's definitely not a monohull, clearly a catamaran with the floats at the front.  I assume the upper foil bodies have significant volume and actually float the stern part of the boat.

It actually looks like a lot of fun!  Wave piercing foils are probably largely automatic and require close to zero input from the sailor.

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^ it will just make the holes bigger and the racing more farcical in the circus venues they have chosen.

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43 minutes ago, Tornado-Cat said:

struggle not to capsize in 10 kts

Is it because you sail a cat that you state such uninformed rubbish?

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1 hour ago, Tornado-Cat said:

While the big AC75 will have to limit themselves to 20 or 22 kts and struggle not to capsize in 10 kts, the F50 who already survived 30 kts gusts in Cowes will go another step forward.

https://www.catsailingnews.com/2019/12/sail-gp-new-high-wind-rig-unveiled.html

SailGP20knotsWing.webp

You say all that like you couldn't put a smaller sail on any boat you wanted to use in heavier conditions...

The 24 knots ETNZ want is EXACTLY the same limit used for the boat the F50 is derived from.

As for capsizing, we have seen one AC75 have a none damaging capsize due to a failed manuaver and suddenly they are struggling? Do we really have to bother going through google to show all the times the AC50 / F50 has come to grief in variety of ways?  Shit happens when your pushing hard in a high performance boat, even more so when your testing a brand new concept.

https://www.sail-world.com/Canada/Americas-Cup--Oracle-capsize-AC50-again-during-practice-3-x-Videos/-153646?source=google

Note the word "again" in the title, in the early days the AC50 was a serial capsizer...

 

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5 hours ago, Boybland said:

 

Note the word "again" in the title, in the early days the AC50 was a serial capsizer...

 

Paraphrasing from another thread, sarcasm font on

Oh, all that AC50 capsizing was before the F50 became a business...lol

I doubt any F50 is gonna lie down and not break bits. The saranwrap wing parts for one...

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14 hours ago, Boybland said:

You say all that like you couldn't put a smaller sail on any boat you wanted to use in heavier conditions...

The 24 knots ETNZ want is EXACTLY the same limit used for the boat the F50 is derived from.

As for capsizing, we have seen one AC75 have a none damaging capsize due to a failed manuaver and suddenly they are struggling? Do we really have to bother going through google to show all the times the AC50 / F50 has come to grief in variety of ways?  Shit happens when your pushing hard in a high performance boat, even more so when your testing a brand new concept.

https://www.sail-world.com/Canada/Americas-Cup--Oracle-capsize-AC50-again-during-practice-3-x-Videos/-153646?source=google

Note the word "again" in the title, in the early days the AC50 was a serial capsizer...

It's a pity they did not use the soft sail allow a reef or no wind limit which would have obliged teams to make it possible.

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15 hours ago, Horn Rock said:

Is it because you sail a cat that you state such uninformed rubbish?

Because it already happened to ETNZ if we believe Gladwell's reports on the conditions.

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1 hour ago, Tornado-Cat said:

It's a pity they did not use the soft sail allow a reef or no wind limit which would have obliged teams to make it possible.

Or they could just pick 5 to 25 knots which is probably 90% of days in the Hauraki Gulf and a pretty common wind range for Auckland racing, exactly like they did in Bermuda with the AC50.... 

I didn't hear too many problems with that approach last time round (not that anybody supporting SailGP could complain given it's basically exactly the same boat).

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8 hours ago, Boybland said:

Or they could just pick 5 to 25 knots which is probably 90% of days in the Hauraki Gulf and a pretty common wind range for Auckland racing, exactly like they did in Bermuda with the AC50.... 

I didn't hear too many problems with that approach last time round (not that anybody supporting SailGP could complain given it's basically exactly the same boat).

Yes, but the interest of a soft sail was to try to reef, perhaps later after this AC.

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9 hours ago, Tornado-Cat said:

Yes, but the interest of a soft sail was to try to reef, perhaps later after this AC.

And to not crane it off the boat, and to lower it at sea.

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3 minutes ago, barfy said:

And to not crane it off the boat, and to lower it at sea.

No cranes, able to reef, self righting, whats next.

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1 hour ago, trt131 said:

No cranes, able to reef, self righting, whats next.

Not really getting your point there.

The sail doesn't need to be craned, live, from the boat. It can be dropped, bagged, transferred to support craft.

Reefs? Maybe, maybe just specialized sails.

Self righting? Hard to believe that teams haven't at least done some halyard pulls to test righting. Maybe you just have not seen the videos? Maybe no-one interested in Florida or wherever? Maybe wait until the nexT capsize?

Come on, what's next on your list of things you'd like to see?

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To be honest I can't really see any real benefit for the teams to actually test the self righting outside of an actual capsize.  If you capsize in a race you have still probably lost.  It's not worth the risk of losing a days sailing just to check it and it's likely so infrequent that it's going to be a race winning manauver it's not worth practicing.

They will just work on the assumption the boats will either self right or at least be very easy to right and don't seem to sustain any real damage when they fall over.

The  most useful scenario for a team is probably if they capsize for some reason prior to the 5 minute gun on race day, in which case it gives them a genuine shot at still being ready to race.

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^ I reckon at the least inquiring minds would put a strain gauge on the halyard and take some measurements at different heels to validate your models. Still without my laptop but are there no static RM values in the measurement?

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Rule's 11.12 and 11.13 give a min righting moment at 90deg of 76 kN-m most likely requiring both foils to be in the full down position ie sticking out like a keel or centreboard to achieve.

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On 12/31/2019 at 12:04 AM, Boybland said:

To be honest I can't really see any real benefit for the teams to actually test the self righting outside of an actual capsize.  If you capsize in a race you have still probably lost.  It's not worth the risk of losing a days sailing just to check it and it's likely so infrequent that it's going to be a race winning manauver it's not worth practicing.

They will just work on the assumption the boats will either self right or at least be very easy to right and don't seem to sustain any real damage when they fall over.

The  most useful scenario for a team is probably if they capsize for some reason prior to the 5 minute gun on race day, in which case it gives them a genuine shot at still being ready to race.

No, the only logic reason why ETNZ righted the AC75 with a motor boat is that it is the fastest solution in a race.

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3 hours ago, Tornado-Cat said:

No, the only logic reason why ETNZ righted the AC75 with a motor boat is that it is the fastest solution in a race.

If that's your attempt at logic it's as futile as your attempts at sarcasm troll c*nt.

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Barfy on this one he was right. It was the quickest way. 
 

not that’s it’s allowed in a race tho. 

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8 hours ago, justsomeone said:

Rule's 11.12 and 11.13 give a min righting moment at 90deg of 76 kN-m most likely requiring both foils to be in the full down position ie sticking out like a keel or centreboard to achieve.

I thought I remembered something along those lines. Thanks for the lookup.:D

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3 hours ago, PJB said:

Barfy on this one he was right. It was the quickest way. 
 

not that’s it’s allowed in a race tho. 

But it's a measurement requirement.

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On 1/1/2020 at 8:43 PM, barfy said:

But it's a measurement requirement.

I think given the fairly strict constraints of the rule, it should be inherent in the design. There's not a lot of room to make it self–righting if it's not already.

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17 minutes ago, RobG said:

I think given the fairly strict constraints of the rule, it should be inherent in the design. There's not a lot of room to make it self–righting if it's not already.

You would hope so. I was just saying it would be something you would want to validate, and if for some reason your computer model had blown a fuse, well you would want to have a long talk with your model.

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Interesting thoughts about pumping. I don't believe we have seen the fcs rules that were decided in Nov and if they would allow these movements. Interesting. As always thanks Italian Guys.

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So, is this the place to discuss the removal of ETNZ's bowsprit?

Confirmation that it won't be used/needed, or are the kiwis up to something else? Was its removal all part of the original plan, explaining why they all look so rudimentary?

 

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55 minutes ago, Ex-yachtie said:

So, is this the place to discuss the removal of ETNZ's bowsprit?

Confirmation that it won't be used/needed, or are the kiwis up to something else? Was its removal all part of the original plan, explaining why they all look so rudimentary?

 

No bowsprit required.
The Whomper is making a comeback.

 

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5 hours ago, Ex-yachtie said:

So, is this the place to discuss the removal of ETNZ's bowsprit?

Confirmation that it won't be used/needed, or are the kiwis up to something else? Was its removal all part of the original plan, explaining why they all look so rudimentary?

 

Nope, just the minimum wind limit that Luna Rossa wants don't require a Code Zero...  So might as well test without it to see if it's worth simply removing from the rules completely.

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11.3 The forwardmost point on the hull shall be no less than 20.600 m and no greater than 20.700 m from TRP.

 

17.1 The combination of the bowsprit and the hull shall form a single linear component.
17.2 The bowsprit shall extend from the hull to at least 22.760 m forward of TRP.
17.3 No part of the bowsprit shall be:
(a) forward of a plane 22.860 m forward of TRP;

 

 

its a way to convert the class to the AC 68 .. that should make it much cheaper to build

 

at this point the bowsprit is a shall have

and its what gives the length to the design name of AC 75

 

maybe they are using it for B2 ,, but that means it cannot comply for racing in cagliari unless the protocol is amended

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Nothing says how substantial it needs to be. Just an instrument pole? Or a clever ploy to mislead the other teams in their b2 design just in the design end game.

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24 minutes ago, barfy said:

Nothing says how substantial it needs to be. Just an instrument pole? Or a clever ploy to mislead the other teams in their b2 design just in the design end game.

Read rule 17.7, and Procedure for Compliance 006. Both are available on the Official Noticeboard.

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4 minutes ago, accnick said:

Read rule 17.7

I see.

I got Google pdf viewer a couple weeks ago which didn't open the rules I dnlded a month ago. I just got another android one full of ads that won't copy text. That's my excuse for my laziness. Thanks for always coming thru with the meat nick.

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On 12/30/2019 at 9:30 AM, Tornado-Cat said:

While the big AC75 will have to limit themselves to 20 or 22 kts and struggle not to capsize in 10 kts, the F50 who already survived 30 kts gusts in Cowes will go another step forward.

https://www.catsailingnews.com/2019/12/sail-gp-new-high-wind-rig-unveiled.html

SailGP20knotsWing.webp

A smaller rig for windy conditions, who would've thunk it.

unnamed__1_.jpg?fm=webp&w=768

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^ Not sure I'd call that a Code Zero. Jib would be more accurate, surely?

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They certainly look to be playing with diffirent options up front now the lower limit looks like it's going to be 7 knots.

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2 hours ago, Sailbydate said:

^ Not sure I'd call that a Code Zero. Jib would be more accurate, surely?

You can’t tack a jib on a bowsprit (you should have learned that in 1992 :D ). Code Zeros belong to the spinnaker family (chord stipulation at half height). Before cursed Coutts messed things up, such a sail would have been called a screacher

 

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25 minutes ago, Xlot said:

You can’t tack a jib on a bowsprit (you should have learned that in 1992 :D ). Code Zeros belong to the spinnaker family (chord stipulation at half height). Before cursed Coutts messed things up, such a sail would have been called a screacher

 

Unlike "conventional" code zero's, AC 75  Class code zero's bear no relation to spinnakers. Just check the sail dimensional limits in rule 19.14. 

The issue in 1992 was the way NZL used the bowsprit when jibing the spinnaker, not how the sail was classified.

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Seen any other boat than ETNZ sporting a code zero ? 

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1 hour ago, Xlot said:

You can’t tack a jib on a bowsprit (you should have learned that in 1992 :D ). Code Zeros belong to the spinnaker family (chord stipulation at half height). Before cursed Coutts messed things up, such a sail would have been called a screacher

Not  a screecher.

To my understanding, screechers were developed for multihulls, have a high clew and are generally flatter than a code 0. Foiler code 0s are very much like a screecher (proportions, flatness) but the low clew to get deck seal makes them not a screecher.

But what's in a name? Aren't they all jibs also?

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5 minutes ago, RobG said:

 

But what's in a name? 

Well.....

Try mixing up the names of your Girlfriends, with that of that of your Lovers and Wives.

That will give you a clue.... ;)

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i found forgetting their names completely was always a bigger problem

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4 minutes ago, phill_nz said:

i found forgetting their names completely was always a bigger problem

Glad to hear I'm not the only one with that problem.

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3 hours ago, PJB said:

Seen any other boat than ETNZ sporting a code zero ? 

No, but according to others, the serious lack of any evidence of them sailing at all is due to a lack of interested spectators, not a lack of sailing.
 

In fact, following this logic, the absence you refer to is actually a sign of superiority. Because we haven’t seen any, the other teams must have better code zeros than anyone else. 

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