Kiwing

The new sailing twin skin setup

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I am thinking this new engine is not nearly as powerful or controllable as the AC35 wing.

Being over 70 and the highest performance boat I have sailed is a paper tiger cat my opinion is hardly up there.

However I am in software and am aware of how good simulation software is these days so I am speculating partly on the figures put out by ETNZ from their simulations.

Does any one want to discuss this (preferably without character assassination!)

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1 minute ago, Kiwing said:

I am thinking this new engine is not nearly as powerful or controllable as the AC35 wing.

Being over 70 and the highest performance boat I have sailed is a paper tiger cat my opinion is hardly up there.

However I am in software and am aware of how good simulation software is these days so I am speculating partly on the figures put out by ETNZ from their simulations.

Does any one want to discuss this (preferably without character assassination!)

I don't think twin-skin will ever be as efficient as a rigid wing, surface area for surface area.

But I also can't see a twin-skin being used if it offers no performance advantages over regular sail.

So if what we get is a new and better type of soft sail, that can be used and hoisted in 'regular' boats, I'd see that as win. 

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2 hours ago, rh2600 said:

I don't think twin-skin will ever be as efficient as a rigid wing, surface area for surface area.

But I also can't see a twin-skin being used if it offers no performance advantages over regular sail.

So if what we get is a new and better type of soft sail, that can be used and hoisted in 'regular' boats, I'd see that as win. 

I agree, I can't imagine they would bother with the complexity if the simulations didn't show a significant performance gain, you wouldn't go there just for fun, especially not with the other obvious gamble with the foils.

Whats the current numbers for a wing versus a soft sail these days? would be nice to know what the range of possibilities we are looking at.

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2 hours ago, rh2600 said:

So if what we get is a new and better type of soft sail, that can be used and hoisted in 'regular' boats, I'd see that as win. 

What do you mean new? You do know that this is not new. It dates back to at least 2015. Glenn Ashby first saw it in Western Australia last year.

Look at THIS

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32 minutes ago, A Class Sailor said:

What do you mean new? You do know that this is not new. It dates back to at least 2015. Glenn Ashby first saw it in Western Australia last year.

Look at THIS

Given the Egyptians were sailing boats 4000 years before Christ rocked up, I'd regard something that appeared 24 months ago, and has yet to be used in any mainstream racing comp as "new"... if you'll let me ;)

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16 minutes ago, rh2600 said:

Given the Egyptians were sailing boats 4000 years before Christ rocked up, I'd regard something that appeared 24 months ago, and has yet to be used in any mainstream racing comp as "new"... if you'll let me ;)

The way you worded it suggested that it was because of the AC that we would get a new type of soft sail. Let's give credit to where credit is due, and its actually been 36 months:P.

Just because it's used in the AC doesn't mean it will get global acceptance and be adopted by many. For most, the question that should be asked is what problem this solves. In the case of the AC, it is yet another attempt to match the performance of the last 2 types of boat while trying to pretend it is something else. Going away from solid wing masts creates a significant problem of how do you generate enough power in the light winds while being able to significantly depower when you get up and foiling. The last 2 AC boats had the ability to produce righting moment from the top of their solid wings through inverting the top, so not only did they have very fine control over the camber of the rig at different points to produce low drag, they were actually able to get some benefit from the rig when depowered. They also were able to maintain airflow over the wing through tacks and gybes which is incredibly efficient compared with a flapping sail.

The interesting thing is that this type of rig has been tried on Moths and it was no better than the current rigs, which are very highly developed.

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29 minutes ago, A Class Sailor said:

The way you worded it suggested that it was...

Only in your head...

183d17bd856b9e273d5454b3238a6ecd.gif.88c235a6ffd5ba04e2556d8a5fe7fe57.gif

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14 minutes ago, A Class Sailor said:

The way you worded it suggested that it was because of the AC that we would get a new type of soft sail. Let's give credit to where credit is due, and its actually been 36 months:P.

Just because it's used in the AC doesn't mean it will get global acceptance and be adopted by many. For most, the question that should be asked is what problem this solves. In the case of the AC, it is yet another attempt to match the performance of the last 2 types of boat while trying to pretend it is something else. Going away from solid wing masts creates a significant problem of how do you generate enough power in the light winds while being able to significantly depower when you get up and foiling. The last 2 AC boats had the ability to produce righting moment from the top of their solid wings through inverting the top, so not only did they have very fine control over the camber of the rig at different points to produce low drag, they were actually able to get some benefit from the rig when depowered. They also were able to maintain airflow over the wing through tacks and gybes which is incredibly efficient compared with a flapping sail.

The interesting thing is that this type of rig has been tried on Moths and it was no better than the current rigs, which are very highly developed.

Comparing the softwing to the hardwing it is easy to see what "problem this solves".  You need to understand that the Hauraki Gulf is significantly larger than the Bermuda puddle. 

You may recall that when some boats were disabled at Bermuda they had to be towed sideways at very low speeds to get back to base where they could be repaired.  Given that the soft rig can be lowered any need for return to base can be accomplished at speed.

If you are advocating a conventional single skin soft sail instead of a double skin sail I can only suggest that the AC does pour lots of money into developing their craft so it is just possible that they will come up with something a bit more advanced than what one lonely chap was able to achieve with the International Moth class.

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6 minutes ago, Terry Hollis said:

it is just possible that they will come up with something a bit more advanced than what one lonely chap was able to achieve with the International Moth class.

aMOCWO0.gif.28242ddfa222e11c92d913cc2d11826f.gif

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Quote

The interesting thing is that this type of rig has been tried on Moths and it was no better than the current rigs, which are very highly developed.

You've declared that the current state-of-the-art SRW was no better than single-skins, and has not been adopted further as a result - fair enough.

Quote

The way you worded it suggested that it was because of the AC that we would get a new type of soft sail. 

So if the AC75 does have a double-skin rig that performs better than single skin, and then we see double-skins get adopted by other sailing rigs then you will have to concede that it was because of the AC that we would get a new type of soft sail, given your stated position above.

I look forward to waiting and watching :-)

200w_d.gif

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1 hour ago, A Class Sailor said:

........

The interesting thing is that this type of rig has been tried on Moths and it was no better than the current rigs, which are very highly developed.

Wow so ETNZ is barking up the wrong tree?  It's that case again "why use bikes we done the numbers and there is no advantage."???

Can you use a single skin main in AC36?  I guess we will see where they all go in due course.

But speculation Anyone?

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The French did the double luff main on both the Langevin designed trimaran foilers Gautier 11 and 111 way back in the early 1980s.  You somewhat angry boys here are way behind the times.

gautier2 copy.jpg

gautier3.jpg

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1 hour ago, Kiwing said:

Can you use a single skin main in AC36? 

Yes. Class rule 19.12.a.

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2 hours ago, A Class Sailor said:

 For most, the question that should be asked is what problem this solves.

IIRC it was presented as being about the relevance of the boats to the wider sport.

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I think the problem it attempts to solves is being able to lower (and maybe even reef) a wing like sail.

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Well, that is certainly an aspect of the irrelevance of wings to the wider sport.

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12 hours ago, Kiwing said:

I am thinking this new engine is not nearly as powerful or controllable as the AC35 wing.

Being over 70 and the highest performance boat I have sailed is a paper tiger cat my opinion is hardly up there.

However I am in software and am aware of how good simulation software is these days so I am speculating partly on the figures put out by ETNZ from their simulations.

Does any one want to discuss this (preferably without character assassination!)

I think this is the only major part of this class that will trickle down. It may not be a new idea, but it’s never seen the sort of R&D money it’s about to. This is what’s great about the AC. 

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Got to agree with Monkey, one real benefit to the rest of the sailing community the AC has consistantly given is that ideas old and new have always had far more money thrown at them by AC teams. Some ideas have proven to be lemons or just not worth the expense, others have been developed to an extent that the transferance to main stream sailing has been relatively cheap. Were it not for the AC I don't think a huge range of things seen on yachts today would be nearly as refined as they are, think deck hardware, keels, rigs and rigging, sailsetc all have had millions thrown at them by AC teams accelerating development. No doubt the development would have occured without the AC but at a much slower pace. Bit like a major war encourages development as cost is less of factor, at the beginning of WW2 single engine monoplanes were still a new thing, by the end we had jet fighters, were it not for the war jet planes would undoubtedly been developed but as quickly?

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L Francis Herreshoff did a double luff main with rotating mast and rigid jib stay in his "Live Yankee," designed in 1927. Plus a flexible "fish tail" rudder and the highest ballast ratio the R Class had seen to date. Got the rig design made illegal by the NYYC for his trouble.

Cheers,

Earl

 

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3 hours ago, Xlot said:

Groundhog thread

 

Sure, but it’s an outlet for the grown ups to talk instead of the usual crap in this forum where the other guy is just automatically evil. 

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@rh2600 So if what we get is a new and better type of soft sail, that can be used and hoisted in 'regular' boats, I'd see that as win. 

Northsails says:- By inverting the upper wing, the sail/wing is actually pushing backwards. It is also pushing to windward, reducing the sail’s tendency to heel the boat. The balance of the inversion and normal camber can in some conditions increase the boat’s performance.

Seems like we are on the right track and maybe help with the low wind speed RM on the 75.

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19 hours ago, Terry Hollis said:

If you are advocating a conventional single skin soft sail instead of a double skin sail I can only suggest that the AC does pour lots of money into developing their craft so it is just possible that they will come up with something a bit more advanced than what one lonely chap was able to achieve with the International Moth class.

Stop being a dick head. Did you even look at the link I posted? They have been making these rigs for all sorts of different types of boat, including keel boats, dinghies and cats. It is not one lonely chap in the Moth class. It took a bit more than that for Ashby to be impressed enough to take the idea to ETNZ.

19 hours ago, Terry Hollis said:

Comparing the softwing to the hardwing it is easy to see what "problem this solves".  You need to understand that the Hauraki Gulf is significantly larger than the Bermuda puddle.

Here is something I have never understood. ETNZ did a significant amount of training on both their AC72 and their AC50 in the Hauraki Gulf and did so in winds right up to the max limit, yet now they want to host the event, the gulf is unsuited to solid wing masts. How does that work?

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39 minutes ago, A Class Sailor said:

Here is something I have never understood. ETNZ did a significant amount of training on both their AC72 and their AC50 in the Hauraki Gulf and did so in winds right up to the max limit, yet now they want to host the event, the gulf is unsuited to solid wing masts. How does that work?

Stop being a dick head. Did you even look at the Hauraki Gulf map? They have been sailing the AC50 in a very specific location not where they can host the next AC, and they had flexibility for windows of good weather. It is not as simple as they could train in Auckland so they could host AC50 wing regettas there. It took a bit more than that for ETNZ to be knowledgeable enough to know that wings are problematic for AC36.

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33 minutes ago, rh2600 said:

Did you even look at the Hauraki Gulf map? They have been sailing the AC50 in a very specific location not where they can host the next AC, and they had flexibility for windows of good weather. It is not as simple as they could train in Auckland so they could host AC50 wing regettas there. It took a bit more than that for ETNZ to be knowledgeable enough to know that wings are problematic for AC36.

Maybe you need to stop drinking the koolaid and start using some intelligence. Go back and check. ETNZ sailed their AC72 up to 8 miles offshore in the gulf in up to 25 knots of wind. That was one of their big claims about changing wind limits in AC34 - they had sailed in worse conditions and designed their boat for those conditions. What is missing from the debate is that a well designed solid wing is actually better for when you get caught out in too much wind because you can set it up in so many ways, including reversing the camber at the top to provide righting moment or simply just blading out the top for low drag.I get fed up with people saying "you can't reef a wing" because it shows how much they don't understand. When you reef a conventional rig, you get left with a section of mast at the top causing significant drag. With a wing you simply take out all the camber and set it so that it is directly into the apparent which is low drag and effective. This isn't my view. This is the view of the ETNZ designers who presented along with BMWOR after AC34. Stop believing the rubbish about wings not being suitable for the conditions because that argument simply does not stack up.

There is only one reason why there are no solid wings in this AC and that is because Dalton and Bertelli don't like solid wings, probably because they didn't come up with them. Others in the team wanted them. The excuses put forward were truly pathetic. "cranes are too expensive"! If you believe that buying a $200K piece of plant (which still has value at the end) and training one of the team to use it is too expensive for a team that is spending $100m you are more gullible than anybody could believe. How many times do you think teams raised and lowered wing masts in the last 2 AC's yet there was only 1 damage problem. You get that simply hoisting sails that often.

So instead of going with something that could have been either one design or close to that and which everybody knew, they have been forced to go down a new route that none of the teams have any experience of and while the mast might be one design, the teams are going to have to spend a small fortune on soft wing development. The rig this time around is going to cost so much more than last time, but Dalton wanted to make the AC affordable:lol:

 

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3 minutes ago, A Class Sailor said:

Maybe you need to stop drinking the koolaid and start using some intelligence. Go back and check. ETNZ sailed their AC72 up to 8 miles offshore in the gulf in up to 25 knots of wind. That was one of their big claims about changing wind limits in AC34 - they had sailed in worse conditions and designed their boat for those conditions. What is missing from the debate is that a well designed solid wing is actually better for when you get caught out in too much wind because you can set it up in so many ways, including reversing the camber at the top to provide righting moment or simply just blading out the top for low drag.I get fed up with people saying "you can't reef a wing" because it shows how much they don't understand. When you reef a conventional rig, you get left with a section of mast at the top causing significant drag. With a wing you simply take out all the camber and set it so that it is directly into the apparent which is low drag and effective. This isn't my view. This is the view of the ETNZ designers who presented along with BMWOR after AC34. Stop believing the rubbish about wings not being suitable for the conditions because that argument simply does not stack up.

There is only one reason why there are no solid wings in this AC and that is because Dalton and Bertelli don't like solid wings, probably because they didn't come up with them. Others in the team wanted them. The excuses put forward were truly pathetic. "cranes are too expensive"! If you believe that buying a $200K piece of plant (which still has value at the end) and training one of the team to use it is too expensive for a team that is spending $100m you are more gullible than anybody could believe. How many times do you think teams raised and lowered wing masts in the last 2 AC's yet there was only 1 damage problem. You get that simply hoisting sails that often.

So instead of going with something that could have been either one design or close to that and which everybody knew, they have been forced to go down a new route that none of the teams have any experience of and while the mast might be one design, the teams are going to have to spend a small fortune on soft wing development. The rig this time around is going to cost so much more than last time, but Dalton wanted to make the AC affordable:lol:

 

yeah nah...

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....... The rig this time around is going to cost so much more than last time, but Dalton wanted to make the AC affordable ?

 

Yeah nah ....

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17 minutes ago, A Class Sailor said:

Good, solid arguments from the fanboys. Keep drinking

 c34572de-f30e-4ee1-8ee0-22d6b415ceda.thumb.jpg.475b9dff4e5377ec9fd12a781f2a329e.jpg

Fan boys of twin-skinned sail? I'm open minded, it's yet to be seen eh... could be crap, could be good..

You are the one trying to shit on everything be default for some strange reason? Here's your flavour kool-aid

LovibondsSourGrapes.jpg.289b6c2543739b1a71ed7795ce9cef1f.jpg

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1 hour ago, A Class Sailor said:

Maybe you need to stop drinking the koolaid and start using some intelligence. Go back and check. ETNZ sailed their AC72 up to 8 miles offshore in the gulf in up to 25 knots of wind.[snip]

 

I was on the water 50+ hours a week for the AC50 training and can tell you that boat was never taken out of the protected waters around browns island with any onshore breeze of consequence. The day the AC72 was out in strong winds was offshore, i remember well.

The Gulf can get groundswell of 1m easy in 20kt of ne, although usually a short period of 8 sec i imagine it would be catastrophic for the AC50 class.

Of course the Match could be held in sheltered waters, but one of the visions is to parade it up and down the reach of the eastern beaches of the north shore where there are many many vantage points for spectators. This is not the case for the "back paddock" around Browns Is.

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1 hour ago, A Class Sailor said:

< snip > What is missing from the debate is that a well designed solid wing is actually better for when you get caught out in too much wind because you can set it up in so many ways, including reversing the camber at the top to provide righting moment or simply just blading out the top for low drag.I get fed up with people saying "you can't reef a wing" because it shows how much they don't understand. When you reef a conventional rig, you get left with a section of mast at the top causing significant drag. With a wing you simply take out all the camber and set it so that it is directly into the apparent which is low drag and effective. This isn't my view. This is the view of the ETNZ designers who presented along with BMWOR after AC34. Stop believing the rubbish about wings not being suitable for the conditions because that argument simply does not stack up.

< snip >

 

Everything you say about wings is absolutely correct, but it is important to remember that the cats are tremendously stable platforms both at rest and at low speeds, whereas the new boats will have very little initial stability which is already going to make towing etc a little more dicey. The addition of a giant rigid wing on a boat with low speed stability issues would be a recipe for disaster IMHO.

I also totally defer to the local experts on the conditions at the planned venue - when you are training/testing, you can pick your days - when you’re racing to a schedule, you gotta hit it whenever it’s within whatever the wind limits are, so the boats need to be spec’d accordingly.  

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1 hour ago, Kiwing said:

....... The rig this time around is going to cost so much more than last time, but Dalton wanted to make the AC affordable ?

 

Yeah nah ....

This rig - which is based on completely untested (at this scale) technology - will literally cost exponentially more per boat than the wings in AC35.

For total total spend, you can multiply that number by 4, since 4 teams will be running parallel development programs.

Might be a good time to buy North Group stock!

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5 minutes ago, surfsailor said:

This rig - which is based on completely untested (at this scale) technology - will literally cost exponentially more per boat than the wings in AC35.

For total total spend, you can multiply that number by 4, since 4 teams will be running parallel development programs.

Might be a good time to buy North Group stock!

I wonder if this is due to the desire (misdirected or not) for the rig to have maximum development within AC in order to push it forward the most.

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^ I think it’s just an unintended consequence of a completely new boat with a completely new rig. The AC72s went thru a similar cost spiral, it’s just an inevitable part of ‘reinventing’ the wheel at this scale (75’).

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lets be real here

their will be no trickle down to any sort of normal sailor with these sails

just like wings

from what i could understand with the moth situation, the wings were cheaper, and easier to maintain for the average sailor than a conventional rig and sail

especially if they were mass produced like rigs and sails, and a single wing is compared to each sailor's two masts and sails which they bring to a regatta to be competetive

multiple wings are not needed for a moth sailor at any level, they are more versatile in their tuning and can be brought through the range

plus a wing can be repaired, e.g ETNZ fixing theirs

where they do become unrealistic though, is when one needs to transport them

very expensive.

 

while this new sail configuration may be faster than a single sail setup, and cheaper than a wing to transport, it will not be cheaper for a sailor all up

taking the moth as an example

a sailor now has two sets of two skins to go through the ranges

twice the expense of the sails, and still two masts to be competitive

as opposed to a single wing that can be taken through the ranges

i can't see this to have any trickel down to domestic sailing even at the highest levels

maybe we will see a few setting records around the world, but they don't need the AC to use them before adopting them themselves

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6 minutes ago, inebriated said:

lets be real here

their will be no trickle down to any sort of normal sailor with these sails

just like wings

from what i could understand with the moth situation, the wings were cheaper, and easier to maintain for the average sailor than a conventional rig and sail

especially if they were mass produced like rigs and sails, and a single wing is compared to each sailor's two masts and sails which they bring to a regatta to be competetive

multiple wings are not needed for a moth sailor at any level, they are more versatile in their tuning and can be brought through the range

plus a wing can be repaired, e.g ETNZ fixing theirs

where they do become unrealistic though, is when one needs to transport them

very expensive.

 

while this new sail configuration may be faster than a single sail setup, and cheaper than a wing to transport, it will not be cheaper for a sailor all up

taking the moth as an example

a sailor now has two sets of two skins to go through the ranges

twice the expense of the sails, and still two masts to be competitive

as opposed to a single wing that can be taken through the ranges

i can't see this to have any trickel down to domestic sailing even at the highest levels

maybe we will see a few setting records around the world, but they don't need the AC to use them before adopting them themselves

This argument would be true for just about every technological advancement - at first they are more expensive, but over time the costs come down to the point where it crosses over the benefit to cost ratio and is adopted. AC is likely about increasing the benefit (at high cost), assuming that over time the costs will correct themselves.

Think Tesla.. these sails are more likely to trickle down that rigid wings - for all the reason we've discussed, ETNZ has already stated, and thus why they are interested in pursuing them...

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Just now, rh2600 said:

This argument would be true for just about every technological advancement - at first they are more expensive, but over time the costs come down to the point where it crosses over the benefit to cost ratio and is adopted. AC is likely about increasing the benefit (at high cost), assuming that over time the costs will correct themselves.

 Think Tesla.. these sails are more likely to trickle down that rigid wings - for all the reason we've discussed, ETNZ has already stated, and thus why they are interested in pursuing them...

yeah

i can understand that argument for wing sails because they are a different product entirely

its just that double skinned sails will always be twice the material and roughly twice the labour to produce compared to a conventional sail

that being said, maybe the benefit to cost ratio will be achieved by that much of a speed (benefit) increase as opposed to a cost reduction

i don't think a whole lot of benefit can be squeezed out of this rig concept like can be cone with a wingsail, unless the level is that high where .05 of a knot is the difference

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1 hour ago, inebriated said:

lets be real here

their will be no trickle down to any sort of normal sailor with these sails

just like wings

from what i could understand with the moth situation, the wings were cheaper, and easier to maintain for the average sailor than a conventional rig and sail

especially if they were mass produced like rigs and sails, and a single wing is compared to each sailor's two masts and sails which they bring to a regatta to be competetive

multiple wings are not needed for a moth sailor at any level, they are more versatile in their tuning and can be brought through the range

plus a wing can be repaired, e.g ETNZ fixing theirs

where they do become unrealistic though, is when one needs to transport them

very expensive.

 

while this new sail configuration may be faster than a single sail setup, and cheaper than a wing to transport, it will not be cheaper for a sailor all up

taking the moth as an example

a sailor now has two sets of two skins to go through the ranges

twice the expense of the sails, and still two masts to be competitive

as opposed to a single wing that can be taken through the ranges

i can't see this to have any trickel down to domestic sailing even at the highest levels

maybe we will see a few setting records around the world, but they don't need the AC to use them before adopting them themselves

Have you ever owned a wing?

Have you ever put up a wing? It fucking sucks, and takes a team of people, and lots of equipment. I've put up a carbon rig alone, and alloy rigs take 2 (on beach cats I mean).

Oh and you can just leave a normal rig up on the boat (soft wing included)... you don't need to drop the whole thing every day.

Breaking the wing is nothing like breaking a mast, when you stuff the rig into the water either you break the main support and it's a massive multi-day job, or you don't break it, a instead you break up all your elements and that still requires massive amounts of time to repair, unlike a soft rig. Where either you break the whole mast (which I've done twice, and been back on the water the next day), or the mast doesn't break and the sails are un-affected. Wing = Much worse.

Another time I crewed on a boat and the skipper went through the main, I avoided everything, we went back in and pulled up another main, and were back out 15 minutes later. If you do that through a wing, your going to be up all night fixing that hole, praying it'll work the next day.

Yeah, transporting a wing sucks. More than a rig. It's nice if the rig fits in a container whole.

I'm dying to see what these guys come up with then 4 teams are throwing 100+million dollars at them, not dudes spending their own money at home.

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i wonder if there will be any components of this new rig that could be patented?  They say there will be special battens, and it looked like there was some sort of control arm at the head in one vid.

Also why would a wide monohull with 2 keels be any more tippy than the average leaner sailboat?

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Any soft sail, whether it has double luff or single luff, has a big disadvantage over a rigid wing - twist is controlled by leech tension.  This greatly increases the loads on the sail, the mast, and the rest of the boat.  The gantry Emirates has added at the head may help, but the sail will still require a lot of leech tension.  The loads needed to react the leech tension ripple through the entire design of the boat.

When you multiply the leech tension by the stretch in the sail and sheet, that is energy that has to be supplied by the crew each time the leech is unloaded and loaded again on a tack or gybe.  The mechanical advantage required to generate the leech tension means it takes some time to grind it in.  With a self-tacking rigid wing, you can basically throw the helm over and the wing will take care of itself, because the camber and twist will invert to the same values they had on the original tack.  The main crew input is to pop the camber at the appropriate moment.  These factors make a soft sail at a disadvantage to a rigid wing when doing a lot of maneuvers in a short time.

For the AC72 and AC50, the rigid wing would have been the rig of choice for stadium racing, even if it had no performance advantage over a soft rig.  

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I'm curious to know what setup is heavier. The AC72 wing or the AC75 twin skin system - mast included.

I imagine the AC72 wing was pretty damn heavy once you add up all of the hydraulic system weight. 

This option, in theory, should be lighter. 

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^ good question @Geronimo I guess there wont be much in it and only a person close to the new rig will know the answer. IMHO

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Leech and main sheet tension is low on this double skinned rig.

You know, old world angled down booms acting as vangs?

One other point that seems to be missed and BS'ed about: a double luff main does not need heavy cloth/material as a single conventional (old world?) setup. Sure the two sails will be heavier in total - but not as much as the alarmists here are claiming in said BS.

double main - Copy.jpg

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@Groucho Marx can you invert the top of this rig?

What would you guess the weight difference would be between the AC36 rig and the AC35 wing or a wing of the same sail area?

Thanks @Kiwing

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I have owned and built plenty of wings.

They aren't easy, but they are so much better than sails that  you are willing to put up with it.

The only people who deny this are people who haven't sailed with a good wing.

SHC

 

 

 

 

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It's early days for me with this rig, Kiwing, and I haven't as yet played around with inverting rig top - but it should not be difficult. Means more lines between the two sails and a cross at mast head.

The refinement and weight exhibited on the AC35 full wings was very impressive - but a soft double luff rig, I'm sure, can be constructed to weigh much less.

The D mast on Frog weighs 26 kgs including all rigging; height is 9.2 metres.

 

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I warrant you are right Steve but us Sunday afternoon sailors who started with a pram dingy sabot have seen the same thing get better to a opti, and lasers and now 29er etc.  I hope one day there will be a very robust plastic wing which rolls up and gives you some of the better performance of the perfect wings.  Until them we have to throw money at it through the AC until that thing drops out the bottom and all the variations up to high performance.  I hope this two skin is a step on the way.

Thanks

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Would be interested in having a look at "Frog". 

@Groucho Marx did she influence ETNZ? Does anyone in the team know of her and her rig?

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53 minutes ago, Kiwing said:

Would be interested in having a look at "Frog". 

@Groucho Marx did she influence ETNZ? Does anyone in the team know of her and her rig?

ETNZ got the idea from Advanced Wing Systems of Western Australia. Glenn Ashby saw it last year and went for a sail on a boat with that rig. I even provided a link to them above.

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20 hours ago, surfsailor said:

The addition of a giant rigid wing on a boat with low speed stability issues would be a recipe for disaster IMHO.

I also totally defer to the local experts on the conditions at the planned venue - when you are training/testing, you can pick your days - when you’re racing to a schedule, you gotta hit it whenever it’s within whatever the wind limits are, so the boats need to be spec’d accordingly.  

This makes zero sense. A solid wing controls power far better and is more adjustable than a soft rig, so why would it be an issue of low wind stability? Surely it's the other way around. Because the solid wing can produce more power and can be adjusted, the boat would spend less time at those low speeds as a solid wing is so much better than a soft sail at low wind speeds.

The whole issue of conditions is misleading. A properly controlled solid wing is significantly better in high winds than a soft sail because instead of reefing, you simply decamber the top and set it so it is directly into the wind. That means the section does not create any lift and has the least frag possible. There seems to be this huge misunderstanding about solid wing masts. With the level of control they had over the AC50 wings, I would much rather be caught out in too much wind with that type of wing than with a soft sail. Some of you need to make an effort to properly understand the technology and listen to people like Steve above.

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I am not very interested in grabbing credit for "who first....."

I am interested in how, in the process this system went through, was thought to be so worth investigating and how it stayed worth investigating until it now is the rig of choice.

Glen might have seen it first in WA but, although he is a big influence in ETNZ, there are many others with knowledge to add power to this rig choice.

It would not surprise me it "Frog" had some influence which is why I asked.

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1 hour ago, A Class Sailor said:

This makes zero sense. A solid wing controls power far better and is more adjustable than a soft rig, so why would it be an issue of low wind stability? Surely it's the other way around. Because the solid wing can produce more power and can be adjusted, the boat would spend less time at those low speeds as a solid wing is so much better than a soft sail at low wind speeds.

The whole issue of conditions is misleading. A properly controlled solid wing is significantly better in high winds than a soft sail because instead of reefing, you simply decamber the top and set it so it is directly into the wind. That means the section does not create any lift and has the least frag possible. There seems to be this huge misunderstanding about solid wing masts. With the level of control they had over the AC50 wings, I would much rather be caught out in too much wind with that type of wing than with a soft sail. Some of you need to make an effort to properly understand the technology and listen to people like Steve above.

You had to edit my quote to make your rant. Of course a wing is better in virtually every respect as I noted. But that's not what I was talking about - I was simply commenting that towing a tippy, massively under-ballasted 75' monohull that relies upon speed-generated hydrodynamic lift for stability will be difficult enough with bare poles (sail dropped) much less with a 40m^2 wing of fixed area that also doesn't freely rotate 180 degrees.

22 hours ago, surfsailor said:

Everything you say about wings is absolutely correct, but it is important to remember that the cats are tremendously stable platforms both at rest and at low speeds, whereas the new boats will have very little initial stability which is already going to make towing etc a little more dicey. The addition of a giant rigid wing on a boat with low speed stability issues would be a recipe for disaster IMHO.

 

 

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L. Francis Herreshoff drew up sketches and plans for an inclining wing rig back in the 1930s.

Sylvestre Langevin had 2 trimaran foilers with double luff sails in the early 1980s (see post no. 12 here).

I started Frog with a D mast a couple of years ago but have been slack in getting it finished. And I'm sure the trifoiler has had less than zero effect on ETNZ.

IMG_6373 - Copy.JPG

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8 hours ago, Steve Clark said:

I have owned and built plenty of wings.

They aren't easy, but they are so much better than sails that  you are willing to put up with it.

The only people who deny this are people who haven't sailed with a good wing.

 

 

Steve, what you are doing and are willing to put up with for a performance gain is entirely different to what the vast majority of sailors want, which is largely convenience over performance.

Even the Mothists, who are the radical early adopter party in sailing, aren't going with wings. Significant developments in materials science are needed before wings become a practical proposition for mainstream sailing. When I can roll up a wing and store it in the boat, let's talk about this again.

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4 minutes ago, dogwatch said:

Steve, what you are doing and are willing to put up with for a performance gain is entirely different to what the vast majority of sailors want, which is largely convenience over performance.

Surely we are talking about the AC in particular and the top end of performance sailing in general. I think most would agree with your comments about the vast majority of sailors

6 minutes ago, dogwatch said:

Even the Mothists, who are the radical early adopter party in sailing, aren't going with wings.

Isn't that because they changed the rules so that slotted wings aren't class legal any more.

Quote

Significant developments in materials science are needed before wings become a practical proposition for mainstream sailing. When I can roll up a wing and store it in the boat, let's talk about this again.

I don't think solid wings will ever be a practical proposition for mainstream sailing and if you can roll it up, it probably isn't going to be solid! Maybe we need the material that Batman made a cape from - when you pass a current through it, it goes rigid.

This double skin rig is a total distraction as far as trickle down is concerned. This is not a quantum leap in performance but it does give the AC boys an opportunity that a single skin sail doesn't. For the mainstream sailors, the extra cost of the mast plus effectively a second main won't give enough payback in terms of performance. If the mainstream want extra performance, there are a number of current rigs they could adopt that are very efficient at significantly less cost than one of these would be.

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Certainly the technology is there already, look at the latest paragliders.  They have double skins that inflate to make the wing shape with enough pressure to hold the wing in all breezes.  Kite boarders do the same and it is amusing watching them on the beach pumping up their double skin wings before hitting the water.

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I am not kitesurfer but AFAIK what they are inflating is the leading edge, and something similar in function to battens. They are not inflating not the entire wing. 

I am a paraglider pilot and yes most are double-skin but I don't think it is much like the AC75 design. Paragliders have no mast, nor are the top and bottom surfaces a symmetrical pair. Most of all, the separation of the surfaces is assisted by the fact that the pilot is dangling off the bottom surface.

 

 

 

 

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What I was getting at is that you could have a wing with inflated battens to hold the shape even if they have to pump the inflated battens with lots of pressure.

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2 hours ago, A Class Sailor said:

Surely we are talking about the AC in particular and the top end of performance sailing in general. I think most would agree with your comments about the vast majority of sailors

Steve's comment appeared to be general rather than targeted.

 

2 hours ago, A Class Sailor said:

Isn't that because they changed the rules so that slotted wings aren't class legal any more.

There was at least one project to put a wing on a Moth. Yes the class decided it didn't want go in that direction. According to our locals, a major issue is that it is common and quite affordable to pack a Moth into a box and air-freight it. Hence there is a good international circuit, not just pros but also those who pay their own way. Wings would stymie that.

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Here is another example of double skin experimentation.  This one from 2015.  On kite boards and A-Class catamarans.  http://herusails.com/2015/tag/a-class-wing-sail-arno-terra/

The Advanced Wing Systems design (http://gre69.wixsite.com/advancedwingsystems) as well as what Frog has now looks the most like what ETNZ and North are proposing as the skins run the full chord length of the sail. 

ETNZ did post this about sailing near a tornado in 2012: https://www.sail-world.com/USA/Americas-Cup-AC72s-caught-on-the-edge-of-tornado-Video/-104480.  I don't know if the video is still available or gone but doesn't seem to show in the article any longer.  I wouldn't think they would take the video down.

 

 

 

 

 

 

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There is no inversion of the top of the sails in all these cases, I think.

For me moving the centre of effort down the sail, increasing the go forward for reduced righting moment is the possible gain as well as increasing control options for tacking and gybing.

Just saying.....

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23 hours ago, Basiliscus said:

Any soft sail, whether it has double luff or single luff, has a big disadvantage over a rigid wing - twist is controlled by leech tension.  This greatly increases the loads on the sail, the mast, and the rest of the boat.  The gantry Emirates has added at the head may help, but the sail will still require a lot of leech tension.  The loads needed to react the leech tension ripple through the entire design of the boat.

When you multiply the leech tension by the stretch in the sail and sheet, that is energy that has to be supplied by the crew each time the leech is unloaded and loaded again on a tack or gybe.  The mechanical advantage required to generate the leech tension means it takes some time to grind it in.  With a self-tacking rigid wing, you can basically throw the helm over and the wing will take care of itself, because the camber and twist will invert to the same values they had on the original tack.  The main crew input is to pop the camber at the appropriate moment.  These factors make a soft sail at a disadvantage to a rigid wing when doing a lot of maneuvers in a short time.

For the AC72 and AC50, the rigid wing would have been the rig of choice for stadium racing, even if it had no performance advantage over a soft rig.  

Additionally, what information has been shared with me indicates that the theoretical soft wing can't achieve anywhere near as high lift coefficients as the hard wing, mainly as a function of the slot. Something tells me this hull and foil configuration are going to want TONS of power at takeoff and getting out of maneuvers. A hard wing usually helps with that. The normal "when you're foiling you don't need as much power" argument is intuitively invalidated to me by my experience with the difficulty of getting foiling and staying foiling. These systems need thrust.

DRC

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I haven’t made the inverted tip super twist thing work yet.  To date my fastest set up has been to reduce camber to the minimum and ease the sheet.  This may be because without a good seal to an impervious trampoline I don’t get the COE to drop as much as the AC designers report. Reducing Angle of Attack reduces the lift coefficient which reduces induced drag, so ideally the wing gets more efficient the less hard you sheet it.

SHC

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23 hours ago, dogwatch said:

I am not kitesurfer but AFAIK what they are inflating is the leading edge, and something similar in function to battens. They are not inflating not the entire wing. 

I am a paraglider pilot and yes most are double-skin but I don't think it is much like the AC75 design. Paragliders have no mast, nor are the top and bottom surfaces a symmetrical pair. Most of all, the separation of the surfaces is assisted by the fact that the pilot is dangling off the bottom surface.

 

 

 

 

There are 2 main types of kites, one of them has a bladder on the leading edge, and in the struts, which together act the same as the mast and batterns ( keep the shape ) on a sail boat.

The other type, is a double skinned internally connected, self inflating ' foil '. The foils use wind flow into a couple of holes in the leading edge lower surface , which have kind of an internal wind sock, that stops reverse flow. The flow then moves around the kite to eventually inflate the wing tips, through the maze of ripstop pouches. The pouches also act along with the flying line bridle - to better distribute the load on the kite and keep the shape. Overall this results in a much less rigid wing compared to the first type, however it is  much more efficient, and so upwind VMG is much higher. something you really notice a lot more, the more you generate apparent wind.

Now what is better on a sail boat, a rigid 3d aerofoil, that is unable to conform with increasing wind speeds, gusts, and has no give..... or a shape itself that is a bit soft.

From a drag point of view, I would have thought soft, but by the same token, soft is harder to make the correct shape in the first place.

How do you attach one of them to a boat, and what performance you would get Vs a conventional single skinned main. Looking fromt he outside, the single skin main = the Tube kite. The twin skin = the foil kite, which should be able to deliver higher performance.

 

https://www.iksurfmag.com/articles/issue58/dont-fear-the-foil-kite/

 

 

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"The other type, is a double skinned internally connected, self inflating ' foil '. The foils use wind flow into a couple of holes in the leading edge lower surface"

Similar in some ways to a paraglider wing then, however on a paraglider the inflation comes from all along the leading edge.

Delta+2+sharknose.jpg

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On 7/6/2018 at 7:00 AM, Kiwing said:

I warrant you are right Steve but us Sunday afternoon sailors who started with a pram dingy sabot have seen the same thing get better to a opti, and lasers and now 29er etc.  I hope one day there will be a very robust plastic wing which rolls up and gives you some of the better performance of the perfect wings.  Until them we have to throw money at it through the AC until that thing drops out the bottom and all the variations up to high performance.  I hope this two skin is a step on the way.

 Thanks

yeah, its just that two skinned sails will always be roughly twice the price of a conventional sail

plus, for say a moth, a round section mast cannot be used if the double bolt ropes are adopted, which i assume would add cost to the project.

i don't really see any of this becoming the future of sailing for the regular guy like me, the only thing that comes close is maybe the advanced wing system guys which have a single sail with in inflatable(?) inside. it would be more expensive but it looks a bit more applicable IMO

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On 7/6/2018 at 7:01 PM, dogwatch said:

There was at least one project to put a wing on a Moth. Yes the class decided it didn't want go in that direction. According to our locals, a major issue is that it is common and quite affordable to pack a Moth into a box and air-freight it. Hence there is a good international circuit, not just pros but also those who pay their own way. Wings would stymie that.

There were at least 2 different projects. Your locals might have thought that is what the issue was, but they were wrong. You can still build a solid wing under the Moth rules, but it has to be one single element with no slot. I believe a few people have built solid wings under this rule but haven't heard how they have gone, although I assume it isn't great because if it was, we would have heard.

On 7/7/2018 at 9:23 AM, Kiwing said:

I guess RM on a cat is not so challenging except in the tacks and gybes, trying to stay up on the foils?

I think you mean heeling moment and it is really important when sailing in a straight line up on foils. The lower you get the heeling moment, the less load there is on the foils which means you can use less lift on the foils and you go faster. This is why on foiling A's we are seeing the top sailmakers producing smaller and smaller heads on their sails, as they try to get the heeling moment as low as possible.

 

3 hours ago, inebriated said:

plus, for say a moth, a round section mast cannot be used if the double bolt ropes are adopted, which i assume would add cost to the project.

You are right if they use double bolt ropes, but on the Moth they don't. Instead, the "sail" wraps around the mast so they can still use the standard mast.

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On 7/7/2018 at 10:53 AM, dogwatch said:

"The other type, is a double skinned internally connected, self inflating ' foil '. The foils use wind flow into a couple of holes in the leading edge lower surface"

Similar in some ways to a paraglider wing then, however on a paraglider the inflation comes from all along the leading edge.

Delta+2+sharknose.jpg

Yeah, but for some reason, they manage it with a few inlets

 

http://www.live2kite.com/ozone-r1-v2-p-3053.html

 

 

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On 7/7/2018 at 7:53 PM, dogwatch said:

"The other type, is a double skinned internally connected, self inflating ' foil '. The foils use wind flow into a couple of holes in the leading edge lower surface"

Similar in some ways to a paraglider wing then, however on a paraglider the inflation comes from all along the leading edge.

Delta+2+sharknose.jpg

notice how the "inlets" are well below the leading edge these days, the "sharknose" design. still gives heaps of internal pressure without sacrificing much drag.

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19 hours ago, dachopper said:

Yeah, but for some reason, they manage it with a few inlets

http://www.live2kite.com/ozone-r1-v2-p-3053.html

 

Kites have water ingress to worry about. For paragliders, the more cells and hence the smoother the leading edge, the higher the performance but also more expensive. The Nova Phantom is an example of a wing that has maximised performance with a modest aspect ratio by increasing the number of cells but its also by far the most expensive wing in its class. 

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Obviously a simpler version of the concept, but still confirms that there is nothing new under the sun.

https://www.wharram.com/site/how-we-design/wharram-wingsail-rig

 

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Nice discussion, even if I am a bit late, I d like to add 2 remarks:

1-According to its very low aspect ratio, I think it is tricky to conclude anything definitive about the relevancy/ efficiency of a wing/ double side sail .... for a Moth. (Induced drag is so big compared to sail section drag)

2-CFD analysis might be the reason for the choice of a double skin sail: In other words, they optimized the global efficiency of the rig (probably drag minimization is more the issue than power maximization) for a design speed of apparent wind.

So, once this apparent wind design speed is  identified, The CFD could have concluded it was necessary to lower sail section drag, in order to achieve a global drag optimum*. 

* For an airplane,  typically this global minimum is achieved when:      induced drag= friction drag

as  one is function of 1/V^2 and the other one a function of V^2.

A double skin sail could provide an opportunity to host a second vertical spar, just like for a slotted wing (at 60% cord).  In combination with a double skin sail with ( double battens= good mechanical inertia), it could address the leech tension a bit differently than a double skin "classic sail" and remove a lot of compression stress from the main spar.

That is just an idea...

Cheers

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The paraglider/kite style ram air inflation is not readily applicable to sails because the stagnation point moves around to the other side on the opposite tack. It might be possible to fit one-way flapper valves to the inlets so they can sustain suction.  But realize the same zone goes from maximum pressure on the windward side to nearly the lowest pressure on the leeward side, and any leakage will be bad news for both lift and drag.

 

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@Basiliscus am I hearing you say this would be really easy to install in the new rig as flaps at the back edge of the D mast would be easy to control and seal? Or is the stagnation point further back, actually on the sail?

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No, the stagnation point is probably still on the D mast. 

My point was say the Design Rule allowed you to make openings in the mast where the stagnation point is when the sail is sheeted on hard.  There will be a strong suction peak on the lee side of the mast at the same time.  The flaps covering the openings on the lee side are going to have to seal against that strong suction.

The kite and parawing examples described in previous posts have the advantage that they only need to produce lift in one direction.  But a sail is not like that.  

I still have a hard time understanding what the advantages are to the double luff sail compared to the wingmast/sail combinations that were popular in the C-class catamarans before they went to rigid wingsails.  The double luff sail can eliminate the separation bubble that forms at the mast/sail junction.  But that can also be done with a large luff pocket, without having to have two sets of battens and two surfaces for the sail aft of the luff pocket.  The double luff sail may look like a rigid wingsail, but it lacks the principal advantages the wingsail has over the soft sail rig.

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Your sentence "The double luff sail ..."  answers your question?

There have been a few experimental double luff pocket mains built for Moths but to my knowledge not for any larger boats. I remember Hugo Myers drew a pocket luff on 44 foot radical catamaran Sea Bird way back in the 1970s but when boat was launched did not have this setup; just a basic rotating mast - which was ahead of its time for a racing offshore design anyway.

There is no argument that AC/C Class full wing is by far the superior race performance rig design - but we wait to see what ETNZ can produce for the next AC with the double sided mains? The result will not be superior to full wings but will be a step up from single sided mains. Plus they can be lowered. Which has to be a practical plus?

wingmasts copy.jpg

sea bird2 copy.jpg

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^ In E does the mast rotate? If it did the two skins trailing edge (leach?) would have to move relative to each other? Or would that be away of controlling the curve on the inner skin?

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In the drawing, mast is fixed. There will be considerable movement between the leech areas with this fixed mast when beating, then reaching/running. On Frog (and I guess on the new AC75s) the mast is a D and it rotates. There is still leech movement with this setup but not as much as in the above plan sketches.

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L F Herreshoff's Live Yankee was different from all in Groucho's diagram. The mast was a D, it rotated, had dual bolt ropes and the double luff extended about 1/3 of the chord.

Another interesting thing about that rig was the jib, which had a rigid, double luff, rotating "jib stay."

Cheers,

Earl

 

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