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pacice

Foiling Monohull - what would it look like?

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6 hours ago, dachopper said:

Hypothetically.......

You could have some mechanism on the foil, that changed it's characteristics such as: some kind of trailing edge flap that deployed ( mechanical ) 

A. Which would allow the higher speeds with minimal drag penalty before use followed by a large increase to convert speed into extra lift / drag, and then large drag reduction once hull is out and flap is pulled back in

B. Fit a flexible membrane over the top surface ( like rubber or something ) and just inflate to increase camber at takeoff speeds.

 

They both sound crazy, but we are talking Americas cup, so whoever figures out how to accelerate until foiling

 

https://www.youtube.com/watch?v=RU78lAJRIsQ

It also needs to weigh 1.2 to 1.5 tons and be strong enough to support a 7 ton boat and it's dynamic loading.

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7 hours ago, Terry Hollis said:

It also needs to weigh 1.2 to 1.5 tons and be strong enough to support a 7 ton boat and it's dynamic loading.

I would imagine start with the 1.2 to 1.5 tonne high speed foil, then "add" / integrate the components to allow slower speeds.

Like the aero design of the Pagani Haura, 

I'm sure they went for the shape first, then added the active aero / drag reducers after.

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On 1/4/2018 at 1:22 PM, Terry Hollis said:

It also needs to weigh 1.2 to 1.5 tons and be strong enough to support a 7 ton boat and it's dynamic loading.

I really wonder about appendage twist or harmonic oscillation interfering with control and or foiling stability. Lots of mass that could contribute to interesting consequences.

The "model" says it will work, but is the model catching everything?

These yachts will not be sailing in very close quarters to each other.

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39 minutes ago, jorgensen said:

I really wonder about appendage twist or harmonic oscillation interfering with control and or foiling stability. Lots of mass that could contribute to interesting consequences.

The "model" says it will work, but is the model catching everything?

These yachts will not be sailing in very close quarters to each other.

According to the cartoon released by ETNZ these boats will be match racing with very close quarters manoeuvres. All with a t foil weighing over 1 tonne sticking out in the air to windward. What could possibly go wrong?

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25 minutes ago, Fireball said:

According to the cartoon released by ETNZ these boats will be match racing with very close quarters manoeuvres. All with a t foil weighing over 1 tonne sticking out in the air to windward. What could possibly go wrong?

Yes, that and the foiling with big gennies are a bit cartoonish, it was done by the animation company ARL as a promotional/informative piece for ETNZ - not by the actual ETNZ Design team. The general dimensions are likely the most accurate part (supplied to them) although I’m a touch skeptical the foil wings will look anything like that basic. Back to safety, it’s not just the opposing crew who’d need to stay clear - those things could drop hard enough to sink the other boat.

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59 minutes ago, ~Stingray~ said:

Re-posting, just for fun

 

Grant Simmers describes the AC75 very well .. I never tire of watching that clip.

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4 hours ago, ~Stingray~ said:

Yes, that and the foiling with big gennies are a bit cartoonish, it was done by the animation company ARL as a promotional/informative piece for ETNZ - not by the actual ETNZ Design team. The general dimensions are likely the most accurate part (supplied to them) although I’m a touch skeptical the foil wings will look anything like that basic. Back to safety, it’s not just the opposing crew who’d need to stay clear - those things could drop hard enough to sink the other boat.

 

The height of the windward foil relative to the other boat could vary a lot. It could be low if the boat was rolling to windward, or it could be high if the boat was heeling. So the list of disaster scenarios is huge, for example:

It could hole the other boat and presumably they will need enough reserve buoyancy to prevent them sinking when full of water.

It could hole the other boat and get torn out of the side of the boat, so now there's two boats full of water.

It could get tangled with the other boat's foil, potentially ripping them both out of the sides of the respective boats.

It could also take out the shrouds of the other boat. If the other boat was to windward (like some of the close quarters manoeuvres in the cartoon) then it's rig would collapse onto the leeward boat. So we could have broken mast(s).

It could take out crew members in the other boat. They will need some sort of protection from a huge t foil being scraped over their deck.

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17 minutes ago, Fireball said:

 

The height of the windward foil relative to the other boat could vary a lot. It could be low if the boat was rolling to windward, or it could be high if the boat was heeling. So the list of disaster scenarios is huge, for example:

It could hole the other boat and presumably they will need enough reserve buoyancy to prevent them sinking when full of water.

It could hole the other boat and get torn out of the side of the boat, so now there's two boats full of water.

It could get tangled with the other boat's foil, potentially ripping them both out of the sides of the respective boats.

It could also take out the shrouds of the other boat. If the other boat was to windward (like some of the close quarters manoeuvres in the cartoon) then it's rig would collapse onto the leeward boat. So we could have broken mast(s).

It could take out crew members in the other boat. They will need some sort of protection from a huge t foil being scraped over their deck.

I don't see those accidents happening .. For one thing it will always be on the windward side and very visible so even a certain British skipper will know to keep clear.  On top of that they will have penalties for being too close to the diamond boundary. 

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3 hours ago, Terry Hollis said:

I don't see those accidents happening .. For one thing it will always be on the windward side and very visible so even a certain British skipper will know to keep clear.  On top of that they will have penalties for being too close to the diamond boundary. 

"a certain British skipper"

whatever do you mean? :)

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7 hours ago, Terry Hollis said:

I don't see those accidents happening ..

I can´t even see those boats foiling as in the clip... Waiting to prove me wrong-

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49 minutes ago, jorge said:

I can´t even see those boats foiling as in the clip... Waiting to prove me wrong-

You wont see proof until they are built and sailing but we can speculate on what might happen.

First off ETNZ say it will foil and they have an impeccable record on predicting the performance of foiling catamarans for AC34 and AC35 as they worked on day one and revolutionised foiling multi hulls in all sizes.

The mono is expected to get onto its foils at a higher wind speed than the AC50's so it is likely that there could be problems with foiling tacks and gybes when the wind strength is lower. In addition they will sailing in displacement mode when the wind strength is at the minimum. 

 

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1 hour ago, Erwankerauzen said:

Hi 

Does anybody knowswhat will be the mast and mainsail concept ?

A classic teardrop mast + full batten sail ???

Happy Sunday

Nobody outside ETNZ knows what the mainsail arrangement will be ..  ETNZ have stated that it wont be a rigid wing but they are looking at some of the designs of wing sails that can be lowered but nothing has been finalised.

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14 minutes ago, Terry Hollis said:

You wont see proof until they are built and sailing but we can speculate on what might happen.

First off ETNZ say it will foil and they have an impeccable record on predicting the performance of foiling catamarans for AC34 and AC35 as they worked on day one and revolutionised foiling multi hulls in all sizes.

The mono is expected to get onto its foils at a higher wind speed than the AC50's so it is likely that there could be problems with foiling tacks and gybes when the wind strength is lower. In addition they will sailing in displacement mode when the wind strength is at the minimum. 

 

Meh.

Bit like a Moth vs a Wasp .

Why would you want to sail some thing thats slower , heavier , and takes longer to get up on foils .

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23 minutes ago, Justaquickone said:

Meh.

Bit like a Moth vs a Wasp .

Why would you want to sail some thing thats slower , heavier , and takes longer to get up on foils .

The expectation is that the AC75 will be faster than the AC50 when the breeze gets up .. as for weight it will be only slightly heavier than the AC72 

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1 hour ago, Terry Hollis said:

The expectation is that the AC75 will be faster than the AC50 when the breeze gets up .. as for weight it will be only slightly heavier than the AC72 

Question is how much speed increases with wind strength (given optimal size of wing) when your main limitations are non super cavetating foils and air resistance . Any data? My guess is that the increase is minimal. If you reach 40 knots in 10 knots of wind. Perhaps you reach 45 in 40 knots.

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3 hours ago, Justaquickone said:

Why would you want to sail some thing thats slower , heavier , and takes longer to get up on foils .

Because a $B pays you a six or seven figure sum to do so. Next question?

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3 hours ago, Terry Hollis said:

The expectation is that the AC75 will be faster than the AC50 when the breeze gets up .. as for weight it will be only slightly heavier than the AC72 

True, some speak of over 50 kts, but I am very skeptic, just imagine the aero drag of the huge hull and ballasted foils. They could optimize AC50 beams for aero. I don't know if they be able to do so for the huge foils for both hydro and aero. Not to speak of the brutal stop if the hulll hits the water.

And, even more important, new AC50 will be optimized with better foils, possibly to modify their geometry in flight.

You will have a ligther and easier boat to fly. Its only limitation will be the one design

On the other hand, the only adavantage of the JC75 will, as an AC boat, that its rules should be more open to development. That is what will make the difference with a boat which concept will stay or disappear.

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TC there is an AC50 rule - it belongs at the moment, along with all the other IP, to the RNZYS

I think you must be referring to the Spiteful49 - a billionaires' bath toy

The relative performance of 2 so far vapourware only boats that will never compete is important how?

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2 minutes ago, nav said:

TC there is an AC50 rule - it belongs at the moment, along with all the other IP, to the RNZYS

I think you must be referring to the Spiteful49 - a billionaires' bath toy

In fact it's neither a 50 or a 49 ft, but a 15M. If the project flies, they will surely rename the faster new boat :)

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Would love to see the AC teams to shock everyone and go "Just kidding" and have a 70-75 foot box rule standard monohull but it looks like we are going with these odd boats.  

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6 hours ago, Terry Hollis said:

The expectation is that the AC75 will be faster than the AC50 when the breeze gets up .. as for weight it will be only slightly heavier than the AC72 

Due  to foil shape limitations the last 2 editions pretty much toped out at the same maximum speed and that was with wing sails as well .

Are we even sure of what rigs the new boats will carry ?

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Boats & Gear

AMERICAS CUP 36: A Bold Leap Into the Unknown Aboard the New AC75 Foiling Monohull

 Category: Boats & Gear
 Created: Sunday, 07 January 2018 17:54
 Written by Charles Doane
 
 

You have to hand it to the Kiwis and Italians who now control the fate of the Auld Mug: they are not lacking in imagination. Nor are they unwilling to take risks. Their concept for the new AC75 monohull in which the next America’s Cup cycle will be sailed, with a pair of canting T-foils sprouting out its sides like insect legs, is both highly creative and unprecedented. My favorite editorial remark so far, from the Daily Sail’s James Boyd in a Facebook thread, is that the new AC boat looks like it wants to crawl up on a beach and lay eggs.

The easiest way to grasp how radical the AC75 is and how it will work (hopefully) is to watch the fabulous promotional video released by the Royal New Zealand Yacht Squadron:

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35 minutes ago, ~Stingray~ said:

Boats & Gear

AMERICAS CUP 36: A Bold Leap Into the Unknown Aboard the New AC75 Foiling Monohull

 Category: Boats & Gear
 Created: Sunday, 07 January 2018 17:54
 Written by Charles Doane
 
 

You have to hand it to the Kiwis and Italians who now control the fate of the Auld Mug: they are not lacking in imagination. Nor are they unwilling to take risks. Their concept for the new AC75 monohull in which the next America’s Cup cycle will be sailed, with a pair of canting T-foils sprouting out its sides like insect legs, is both highly creative and unprecedented. My favorite editorial remark so far, from the Daily Sail’s James Boyd in a Facebook thread, is that the new AC boat looks like it wants to crawl up on a beach and lay eggs.

The easiest way to grasp how radical the AC75 is and how it will work (hopefully) is to watch the fabulous promotional video released by the Royal New Zealand Yacht Squadron:

Have seen plenty of vapourware presentations that haven't quite lived up to expectations,( hopefully) this one surprises ?

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11 minutes ago, Justaquickone said:

(James Boyd) “It looks like it wants to crawl up on a beach and lay eggs.”

I love that quote! Saw it in German, nice to see it re-confirmed and with a link.

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5 minutes ago, etienne.billiet said:

Jean Sans has further worked on take off, flight control, and stability steadiness. An additional technical brief will be posted in theh coming day on our french site https://www.uncl.com/courses/technique/. Will "google english" be OK or shall we sppenf time at translating?

The English pdf you posted last time was nice

http://forums.sailinganarchy.com/applications/core/interface/file/attachment.php?id=253077

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29 minutes ago, etienne.billiet said:

Jean Sans has further worked on take off, flight control, and stability steadiness. An additional technical brief will be posted in theh coming day on our french site https://www.uncl.com/courses/technique/. Will "google english" be OK or shall we sppenf time at translating?

Great! Please flag the original as it comes out, and then we'll see how best to proceed

 

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2 hours ago, etienne.billiet said:

Jean Sans has further worked on take off, flight control, and stability steadiness. 

About stability, curious to see if Jean maintains the 80/20 load split between foil and rudder. This was debated to death for the AC50, and the consensus sort of was that this might be valid on take-off, but for a stable flight the rudder stabilizer should have negative lift - same as conventional airplanes

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44 minutes ago, nav said:

^ He does use 80/20 in his calcs, I shuddered when I saw it......

https://www.uncl.com/2017/12/01/techniques-innovations/nouvel-ac-75-nz-jean/

but ...

The lift on the foil associated with saffron is lower than the theoretical 20%, it would give the boat a lift, which should not be a handicap in the take-off phase.

etc

How about that....................................................................................................................................................

Well, it depends:  "The lift on the foil associated with saffron is lower than the theoretical 20%, it would give the boat a lift, which should not be a handicap in the take-off phase."

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43 minutes ago, nav said:

La portance sur le foil associé au safran est plus faible que le 20% théorique, cela donnerait du cabrage au bateau, ce qui ne devrait pas être un handicap dans la phase de décollage.

 

Lift on the rudder foil is lower than the theoric 20%, which will give "rearing" to the boat, which should not be a handicap in this take off part of the flight.

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16 hours ago, Tornado-Cat said:

True, some speak of over 50 kts, but I am very skeptic, just imagine the aero drag of the huge hull and ballasted foils. They could optimize AC50 beams for aero. I don't know if they be able to do so for the huge foils for both hydro and aero. Not to speak of the brutal stop if the hulll hits the water.

And, even more important, new AC50 will be optimized with better foils, possibly to modify their geometry in flight.

You will have a ligther and easier boat to fly. Its only limitation will be the one design

On the other hand, the only adavantage of the JC75 will, as an AC boat, that its rules should be more open to development. That is what will make the difference with a boat which concept will stay or disappear.

The AC72's were marginally faster than the AC50's in spite of the fact they were at a very early stage in the development of the foils .. The AC50's were more aerodynamic and had their races in smoother water but they had a slightly lower top speed.

I think the higher righting moment of the AC72's must have given them the edge and I think this factor also applies to the AC75's particularly when the rougher water of the Hauraki Gulf is considered.

On top of that they have time to further refine the foils and even add extra controls for the wider range of wind that expected.

 

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Im finding it a bit hard to believe the boats are going to be any faster than the last 2 incarnations of the AC .Flaps , Wands, Controls or whatever .

My understanding is that you would have to move into Sail Rocket territory with super cavitating foils and that does not a course racer make .

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31 minutes ago, Justaquickone said:

Im finding it a bit hard to believe the boats are going to be any faster than the last 2 incarnations of the AC .Flaps , Wands, Controls or whatever .

My understanding is that you would have to move into Sail Rocket territory with super cavitating foils and that does not a course racer make .

Being faster doesn't mean "Sail Rocket territory" .. half a knot faster is still faster.

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1 hour ago, Justaquickone said:

Im finding it a bit hard to believe the boats are going to be any faster than the last 2 incarnations of the AC .Flaps , Wands, Controls or whatever .

My understanding is that you would have to move into Sail Rocket territory with super cavitating foils and that does not a course racer make .

Faster around a W/L course does not take them into super-cavitating territory. The fastest point of sailing in AC34/35 was the reaching start and that is gone from AC36.

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28 minutes ago, dogwatch said:

Faster around a W/L course does not take them into super-cavitating territory. The fastest point of sailing in AC34/35 was the reaching start and that is gone from AC36.

My memory may have diminished a little but in San Fran I thought NZ's top speed was obtained on one of the runs ?

Feel free correct me if I'm mistaken.

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3 hours ago, Terry Hollis said:

The AC72's were marginally faster than the AC50's in spite of the fact they were at a very early stage in the development of the foils .. The AC50's were more aerodynamic and had their races in smoother water but they had a slightly lower top speed.

I think the higher righting moment of the AC72's must have given them the edge and I think this factor also applies to the AC75's particularly when the rougher water of the Hauraki Gulf is considered.

On top of that they have time to further refine the foils and even add extra controls for the wider range of wind that expected.

 

Some data claims AC50s were faster:

From: https://en.wikipedia.org/wiki/AC50

The class achieved a maximum peak speed of 47.2 knots (87.4 km/h) over the water, recorded by ACRM telemetry aboard Magic Blue.[2]

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I still have AC 35 footage stored on my work computer, when I'm back again after holidays i'll try  and find a bit of time to go back through it .

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23 hours ago, Tornado-Cat said:

True, some speak of over 50 kts, but I am very skeptic, just imagine the aero drag of the huge hull and ballasted foils. They could optimize AC50 beams for aero. I don't know if they be able to do so for the huge foils for both hydro and aero. Not to speak of the brutal stop if the hulll hits the water.

And, even more important, new AC50 will be optimized with better foils, possibly to modify their geometry in flight.

You will have a ligther and easier boat to fly. Its only limitation will be the one design

On the other hand, the only adavantage of the JC75 will, as an AC boat, that its rules should be more open to development. That is what will make the difference with a boat which concept will stay or disappear.

You can optimize a Cat for aero all you like, there is always going to be more of it, than there is of a mono = more drag.

I think there are a bunch of foils out there now that provide supercavitation, and reasonable performance with sub cavitation / takeoff mode.

The issue is at higher angles of attack - 4 - 7 degrees, these foils have multiple times the co-efficient of drag than traditional foils. until the AoA is back down 

There will be a crossover point.... question is, will the boat get there under wind power?

 

Could they inject air onto the leading edge to force the foil to be cupercavitating at high speed :)

 like some other new marine designs

 

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5 hours ago, Justaquickone said:

Im finding it a bit hard to believe the boats are going to be any faster than the last 2 incarnations of the AC .Flaps , Wands, Controls or whatever .

My understanding is that you would have to move into Sail Rocket territory with super cavitating foils and that does not a course racer make .

Sail Rocket did not need or use super cavitating foils. Base ventilating was (and still is) more efficient and fast enough for the task at hand.

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Fun article: https://www.sailingworld.com/on-fast-track-to-cup

On a Fast Track to the Cup

Young American engineer Robyn Lesh earns a seat at Bella Mente Quantum Racing’s design table for the 36th America’s Cup.

By Ellinor Walters 1 hour ago
 
...

Simply to lift the boat with the lever arm of the length of the foil the joint will need to withstand nearly 100,000N-m of moment with almost no room for an internal lever arm.”

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So the above posts are proof of what I suggested, comparing boats that will never compete against other is pretty much pointless

Not least because:

- you all come up with different 'best' numbers (even for the same class/event!)

- no one seems to agree on the significant number anyway - straight line/instantaneous/sustained/full course .....

- conditions vary

Gotta laugh at the 'aero' comments too, if as it appears ^ (one of) the top speed(s) belongs to the Tractor - openly derided as the most un-aerodynamic of them all !?

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7 minutes ago, ~Stingray~ said:

Simply to lift the boat with the lever arm of the length of the foil the joint will need to withstand nearly 100,000N-m of moment with almost no room for an internal lever arm.”

"Houston, we have a problem"

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18 minutes ago, arneelof said:

 

I can't recall exactly, the link was from wikipedia: https://en.wikipedia.org/wiki/AC72

From there,

The fastest race speed recorded was on Emirates Team New Zealandwhich was 47.57 knots (88 km/h, 55 mph) in 21.8 knots of wind (2.2 times the wind speed) on September 24, 2013.[8]

(me:) The top AC50 recorded speeds were 47.22 (Artemis) and 47.20 (SoftBank) on June 6, 2017:

AC50_SOG_MAX.thumb.PNG.a39c4dcec70ca88f6ed0ad10a44b3de2.PNG

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2 hours ago, ~Stingray~ said:

Simply to lift the boat with the lever arm of the length of the foil the joint will need to withstand nearly 100,000N-m of moment with almost no room for an internal lever arm.”

Most assuredly showing my age / male chauvinism, but the pretty young thing needs not worry: the common lever mechanism will certainly be in the (slightly more experienced) hands of Messrs Cariboni and possibly Francesco Binetti Pozzi

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2 hours ago, Xlot said:

Most assuredly showing my age / male chauvinism, but the pretty young thing needs not worry: the common lever mechanism will certainly be in the (slightly more experienced) hands of Messrs Cariboni and possibly Francesco Binetti Pozzi

Perhaps she could suggest cedar

http://rosalindrobynl.wixsite.com/rlesh/building-t50

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  ^ Possibly (except of course epoxy doesn't "dry"...). Reminds me of when, many many moons ago, it was instilled into me that a graduate engineer is the animal most dangerous to self and others in the Creation

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3 hours ago, Xlot said:

Most assuredly showing my age / male chauvinism, but the pretty young thing needs not worry: the common lever mechanism will certainly be in the (slightly more experienced) hands of Messrs Cariboni and possibly Francesco Binetti Pozzi

You most certainly have, 

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34 minutes ago, Xlot said:

 

  ^ Possibly (except of course epoxy doesn't "dry"...). Reminds me of when, many many moons ago, it was instilled into me that a graduate engineer is the animal most dangerous to self and others in the Creation

Do we get to hear your technical view?

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7 hours ago, ~Stingray~ said:

Fun article: https://www.sailingworld.com/on-fast-track-to-cup

On a Fast Track to the Cup

Young American engineer Robyn Lesh earns a seat at Bella Mente Quantum Racing’s design table for the 36th America’s Cup.

By Ellinor Walters 1 hour ago
 
...

Simply to lift the boat with the lever arm of the length of the foil the joint will need to withstand nearly 100,000N-m of moment with almost no room for an internal lever arm.”

Also from there,

“From the prior AC boats the loads on the foils nearly doubled during maneuvers. I don't expect there is a way to create an articulating joint that can withstand that amount of force without some sort of locking mechanism for when the foils are in lifting mode. A difficult component of a lock is that the boat-lifting foil orientation is in the center of the foils' range of motion and the foil must articulate in both directions beyond this point. And the whole foil mechanism must be contained in a waterproof compartment!”

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On 4/01/2018 at 5:22 PM, Groucho Marx said:

In reply to Hoom: there are some very bright people at ETNZ involved with this radical design and none of us, we, the wankers, know anything about the proposed craft ... because no one has ever sailed such a beast or maybe even thought of such a configuration; it is beyond radical.

On Groucho and Sid, lift is generated from the foils the moment the boat begins moving, the floats are there really for when at rest or in light airs. But you can bury float and foil if ... you are insanely insensitive, with full main sheeted hard in way too much wind strength. This is pretty much the same as sailing any boat design - but maybe on lightweight minimalist foilers, you have to be a little more sensitive? However I have sailed Groucho in fresh winds with both float foils lifted, (these were angled daggers in cases) as an experiment and was surprised with the stiffness, didn't expect it. But the boat is very wide, square for its length - and that must help too.

Upwind performance is very good, pretty much the same as any light design with deep asymmetric foils - but then there is a dagger in main hull plus the T type foils in floats and on rudder. Some foil nutters say put a T foil on the main dagger; I've not tried that -  but have done so on my skimming dish 18 foot monohull which lifts off on reaches.

Thanks :)

I think you undersell the relevance of your experience, there aren't very many people who have sailed these kind of foil stabilised mono/tri-foilers.

 

Yes they are very bright people with a great track record but it is a concept really far from anything else previously tried, starting very big & without any sub-scale prototype proof of concept before they write the rule/design a bunch of one-design components, I feel its really a huge huge risk.

 

My concern for the initial stability is the AC72/50 both had the big initial righting moment by flying a hull prior to takeoff & lee hull was pretty often well pressed, JC75 has less beam & much less initial righting moment with a draggier fat hull.

 

16 hours ago, Terry Hollis said:

The AC72's were marginally faster than the AC50's in spite of the fact they were at a very early stage in the development of the foils .. The AC50's were more aerodynamic and had their races in smoother water but they had a slightly lower top speed.

I think its not that AC50s were faster in top speed in high winds but they were clearly faster for a given lower wind speed, possibly faster average overall.

 

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Figaro 3 fitted with a T-Rudder and Centerboard and then scaled up !!!!       this little PRODUCTION boat is starting to show what can be achieved..... so don't 'right off the impossible' just yet.  

 

Groucho has it nailed...  we know nothing....

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It will be interesting to see these boats preforming a slow tack.

As the boat comes out the tack, it will struggle to great enough power to create enough speed to get up on the foils. I believe we will see more than one of them fall over in the pre-start. 

The advantage of a Cat, is the width, and the ability to great maximum power to build up the speed. With the AC75, you have a narrow light boat that will be very tender, and the crews will need work to keep the boat upright.

 

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8 hours ago, hoom said:

I think its not that AC50s were faster in top speed in high winds but they were clearly faster for a given lower wind speed, possibly faster average overall.

Yes I agree that the AC50's were much faster round a course in almost all wind conditions.

Having said that I can't help but wonder how the AC72''s would have performed if they had been used in AC35 instead of the AC50's .. the extra time for development would have made a huge difference.

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6 hours ago, Tornado-Cat said:

Some predict over 50kts but I would like to see their maximum speed due to the aero drag of their huge hulls. I mean, depending on the rule.

One of the advantages the AC75 foiling mono has over the foiling cats is the superior aero.  No massive beams large nets and decks together with one hull instead of two. 

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21 minutes ago, Terry Hollis said:

Yes I agree that the AC50's were much faster round a course in almost all wind conditions.

Having said that I can't help but wonder how the AC72''s would have performed if they had been used in AC35 instead of the AC50's .. the extra time for development would have made a huge difference.

Magnificently

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10 hours ago, ~Stingray~ said:

Also from there,

“From the prior AC boats the loads on the foils nearly doubled during maneuvers. I don't expect there is a way to create an articulating joint that can withstand that amount of force without some sort of locking mechanism for when the foils are in lifting mode. A difficult component of a lock is that the boat-lifting foil orientation is in the center of the foils' range of motion and the foil must articulate in both directions beyond this point. And the whole foil mechanism must be contained in a waterproof compartment!”

 

Aw, but she's a weight control engineer FFS, which is as junior as it gets on the project totem pole - perfect case for Sutor, ne ultra crepidam!

[and writing twice that epoxy "dries" in my book would bring to an early end a job interview - and an MIT grad at that,  just imagine!]

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I would think it's more a case of find solutions (at least for all the common parts and mechanisms) then finish the rule...

Verdier already said they will make changes to the original proposal if required

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2 hours ago, Terry Hollis said:

One of the advantages the AC75 foiling mono has over the foiling cats is the superior aero.  No massive beams large nets and decks together with one hull instead of two. 

One of the advantage of a new AC50 would be to use the beams with flaps like a plane in order to control the RM.

I bet AC75 speed, with the actual hull design, will not top 47 kts, but I bet the final design will change, Verdier must be working on it.

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2 hours ago, Terry Hollis said:

One of the advantages the AC75 foiling mono has over the foiling cats is the superior aero.  No massive beams large nets and decks together with one hull instead of two. 

i'm no expert on aero drag

but surely 2 skinny hulls, faired beams and crew in a cockpit would produce less aero drag than a fat monohull with an open deck and crew that are facing full winds on their whole body, unless they can put everyone in pits, which would take away from GD's return to more relatable mono hulls

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3 minutes ago, MR PLOW 270 said:

 

i'm no expert on aero drag

but surely 2 skinny hulls, faired beams and crew in a cockpit would produce less aero drag than a fat monohull with an open deck and crew that are facing full winds on their whole body, unless they can put everyone in pits, which would take away from GD's return to more relatable mono hulls

Why do you think it will be a "fat monohull" ? The monohull only weighs 7 tons .. fractionally more than the AC72.

The hull will be no larger than it needs to be to accommodate the crew. It wont need to be beamy for righting moment. 

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Just now, Terry Hollis said:

Why do you think it will be a "fat monohull" ? The monohull only weighs 7 tons .. fractionally more than the AC72.

The hull will be no larger than it needs to be to accommodate the crew. It wont need to be beamy for righting moment. 

i'm not saying fat as in heavy or anything, just a fair head on profile

it would be close, but i'd say it would be thicker than the two hulls of an AC50

it wont need to be beamy for righting moment, although i don't think the rules will permit a narrow enough beam to get better aero than the ac50

Image result for ac75

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21 hours ago, ~Stingray~ said:

Fun article: https://www.sailingworld.com/on-fast-track-to-cup

On a Fast Track to the Cup

Young American engineer Robyn Lesh earns a seat at Bella Mente Quantum Racing’s design table for the 36th America’s Cup.

By Ellinor Walters 1 hour ago
 
...

Simply to lift the boat with the lever arm of the length of the foil the joint will need to withstand nearly 100,000N-m of moment with almost no room for an internal lever arm.”

External lever it is then

 

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2 hours ago, Tornado-Cat said:

One of the advantage of a new AC50 would be to use the beams with flaps like a plane in order to control the RM.

I bet AC75 speed, with the actual hull design, will not top 47 kts, but I bet the final design will change, Verdier must be working on it.

 

Unless you think the ' NEW' AC 50 is going to be doing 200 kts, then flaps are not going to do a thing except give the Cat design even more drag.

 

 

 

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49 minutes ago, MR PLOW 270 said:

i'm not saying fat as in heavy or anything, just a fair head on profile

it would be close, but i'd say it would be thicker than the two hulls of an AC50

it wont need to be beamy for righting moment, although i don't think the rules will permit a narrow enough beam to get better aero than the ac50

Image result for ac75

So look at that picture, Split the Hull in half down the middle so that now you have maybe 30% more Hull surface area, then add 2 x  massive cross beams ( One front and one rear ) and netting to go with it.

 

Part of the drag equation involves skin friction, and interference drag. Those cross beams look to have more cross sectional area than the hulls, and behind them you have a flat trampoline, so part of the equation involves almost cat 4 x hulls worth of cross sectional frontage + the worlds best drag inducer in the middle. Netting.

 

ETNZ-01.thumb.jpg.7979feb1830c25d6d3b72eb53543e3fd.jpg

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36 minutes ago, dachopper said:

External lever it is then

 

Indeed, that's a possibility - say with the lever protruding just for the bottom rotation to the docking position. Would require interesting structural solutions, like an outsize keel tube to keep bow and stern together. But - again - this is much better left to specialists.

In terms of hull shape, we all know this is really a - foiling, ballasred, self-righting - tri, so why not have a tri center hull? On another tack, IIRC similar-sized ULDBs were just 3 m wide, so if the Rule will allow/impose a 5 m width for the foil hinges, one could have two side nacelles on a 3 m wide hull. Keep in mind take-off will be confined to a beam reach or running

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Just now, dachopper said:

So look at that picture, Split the Hull in half down the middle so that now you have maybe 30% more Hull surface area, then add 2 x  massive cross beams ( One front and one rear ) and netting to go with it.

 

Part of the drag equation involves skin friction, and interference drag. Those cross beams look to have more cross sectional area than the hulls, and behind them you have a flat trampoline, so part of the equation involves almost cat 4 x hulls worth of cross sectional frontage + the worlds best drag inducer in the middle. Netting.

 

ETNZ-01.thumb.jpg.7979feb1830c25d6d3b72eb53543e3fd.jpg

ok, fair point that the netting would be shitty for aero

we aren't talking about the 72 though, we're talking about the 50

considering the netting now, then yeah, the 75 may have a little bit less aero drag than the 50, but a lot less drag if they find out a way to streamline the bodies, like Oracle did in the 72/ ETNZ in the 50

this being said, i still don't think that the 75 will be faster than the 50

the 75 has less beam across the foils (i think??!), ie less RM from the foils alone

the 50 could provide RM from its rudder foils, it doesent look as though the 75 can

the 50 weighs much less, also meaning less foil in the water, giving less drag (unless windward rudder is providing shit tones of RM)

the 50 has just as much weight to windward as it has providing balance in the foils, albeit further inboard, but not much

the wingsail is more efficient than a soft sail

and if we're talking about all around speed, not top speed, the 75's will be a dog to foil in light winds and the manoeuvres will be much harder (i don't think we'll see 100% dry time this cycle)

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