pacice

Foiling Monohull - what would it look like?

Recommended Posts

2 hours ago, Terry Hollis said:

You seem to be very confused about what is a mono hull and what is a multi hull.

Mono means one .. multi means more than one.

The AC75 has ONE HULL so that makes it a MONO HULL

As for your comments on engineering .. clearly you know nothing.

yeah

it requires some reading between the lines

it is technically a monohull by all means, but they won't be sailing it like one

to be honest, it is as much of a multihull as one could go while still keeping with the name monohull, which is why i reckon the kiwi's did it

it's just a shame that they were restricted by their dealings with the italians, i would have liked to see what they would have made with no restrictions, if it would be different to this

Share this post


Link to post
Share on other sites
4 hours ago, Terry Hollis said:

 

Mono means one .. multi means more than one.

 


If it was as simple as that we would be seeing some real monohull abomination. Even worse than the offshore scows. Maybe something like a scow hull with a great big athwartships concave bend in it.  Yes with more in common with a multi, BUT TECHNICALLY A MONOHULL .

 

Hence isn't just the term ONE HULL a little simplistic. 

What about MONOHULL = yacht in which the depth in any section does not decrease toward the centreline.

 

Aren't these AC foilers just another step along the road from the Tabarley foiler PAUL RICARD?:D

Share this post


Link to post
Share on other sites

At 40 knts boat speed in 25 knts TWS 

The apparent wind speed when sailing windward @ 40 knts would be around 60 knts

So Mates, you must hold firmly your Sailing Anarchy caps (model Hill Billy is my prefered one)  

Share this post


Link to post
Share on other sites
4 hours ago, overlay said:

What about MONOHULL = yacht in which the depth in any section does not decrease toward the centreline.

Something like this was the accepted definition for a very long time, like since the tunnel hull scow Dominion...

dominion3-gif.68770

 

Share this post


Link to post
Share on other sites
4 hours ago, Erwankerauzen said:

At 40 knts boat speed in 25 knts TWS 

The apparent wind speed when sailing windward @ 40 knts would be around 60 knts

So Mates, you must hold firmly your Sailing Anarchy caps (model Hill Billy is my prefered one)  

Not only that...

Upwind 40kt VMG at say 40 deg TW angle is 52kt boat speed ... 52kt upwind?

Downwind 50kt VMG at say 140 deg TW angle is 65kt boat speed !!!!

isn´t it cavitation territory? what was Sailrocket record again? is it April already?

 

Share this post


Link to post
Share on other sites

I agree. Those number look really overestimated, like they don't keep into account all drag parameters. Cavitation and basic aero drag from the platform (upwind) alone would make 50 knots upwind and 60 knots downwind impossible in any wind.

I would be reeeeeally astonished if in 2 years time any AC boat went consistently at 30 knots upwind vmg (that is 40 knots BS) in any wind. Cool times though :)

 

 

 

  • Like 1

Share this post


Link to post
Share on other sites

I edited the front page piece after a couple of smart designers explained what the graphs meant.

 

"Boatspeed on VMG course upwind/downwind" is what the header ought to have been.  Botin and Carrau speak good english, but clearly not good enough for my cobwebby brain.

So 40 knots of boatspeed at an upwind VMG angle...

 

apologies for being thicker than a snickers

 

 

Share this post


Link to post
Share on other sites
9 hours ago, Godzilla said:

Why is Clean comparing these boats to AC 50s?

Should we not be using AC 72s as the benchmark? Did I miss something here?

Why?  50s were quicker.

Share this post


Link to post
Share on other sites
6 hours ago, overlay said:


If it was as simple as that we would be seeing some real monohull abomination. Even worse than the offshore scows. Maybe something like a scow hull with a great big athwartships concave bend in it.  Yes with more in common with a multi, BUT TECHNICALLY A MONOHULL .

 

Hence isn't just the term ONE HULL a little simplistic. 

What about MONOHULL = yacht in which the depth in any section does not decrease toward the centreline.

 

Aren't these AC foilers just another step along the road from the Tabarley foiler PAUL RICARD?:D

Its pretty simple really

https://en.oxforddictionaries.com/definition/monohull

https://en.oxforddictionaries.com/definition/multihull

Don't overthink it.

Share this post


Link to post
Share on other sites
7 hours ago, inebriated said:

yeah

it requires some reading between the lines

it is technically a monohull by all means, but they won't be sailing it like one

to be honest, it is as much of a multihull as one could go while still keeping with the name monohull, which is why i reckon the kiwi's did it

it's just a shame that they were restricted by their dealings with the italians, i would have liked to see what they would have made with no restrictions, if it would be different to this

Monohulls are allowed to foil, just like cats are allowed to displace... Neither changes their form

Share this post


Link to post
Share on other sites
8 hours ago, dogwatch said:

Go on then. Explain why signing the framework agreement would have made it harder to win. While you are at it, since TH's comment was about the protocol rather than the framework agreement, explain how the AC35 protocol and the framework agreement were connected.

My quote was tongue-in-cheek but fuck it, this will be easy sport.

Having signed up to LA ties the hands of the winner in terms of what they can do for the next two cycles. This diminishes the ultimate power typically gained by a successful challenge and as such devalues the prize. This effects sponsorship discussions, team attitudes and ultimately desire to win - as witnessed.

If you don't see the LA as an augmentation of the protocol in that it fundamentally changed major aspects if it then I can't help you.

FWIW the LA also secured the r&d advantage of the defender, making future ACs under it also harder for challengers to win.

Chew on that ;-)

Share this post


Link to post
Share on other sites

So  in your second paragraph you are argue the Framework agreement decreased the influence of the defender but in your 4th you argue the exact opposite.

Share this post


Link to post
Share on other sites
On 2/2/2018 at 4:25 PM, Terry Hollis said:

 

The AC75 has one advantage over the cats .. it seems to be self righting.

Sorry, this has probably been covered. I'm just catching up. But, how is this design supposed to be self righting in sailing configuration? It doesn't pass the "scribbled lines in paint" test :) Is the plan to run the engines to drive the keels while the engines are upside-down and, perhaps, wet?

5a7765f5a7250_ac50renderoops.thumb.JPG.ac22b0dbdf6b8a30a88b03c18f72d59f.JPG

Share this post


Link to post
Share on other sites
25 minutes ago, jorge said:

IMHO no way these AC 35 are going to be faster than a AC50, and no way they are going to foil easier than ac 50 or 72

I don't care or expect them to be faster.

They do bring America's cup a new dimension new sailing tech, expand the horizon, more guessing and speculation for us guys too.

  • Like 1

Share this post


Link to post
Share on other sites
2 hours ago, dogwatch said:

So  in your second paragraph you are argue the Framework agreement decreased the influence of the defender but in your 4th you argue the exact opposite.

Nope... again, your inability to parse structured English is worrisome for future discussion on these boards...

Second para was about being bound by the LAs terms that were set by OTUSA with their existing advantage, cycle plan etc all in their hands. It was by signing the FA that *increased* OTUSA's power - see?

Last paragraph was referring to the LA rules that prevented signatory teams from building, testing or training on AC45 surrogate boats between cycles - meanwhile Oracle would have the benefit of having run full testing programmes in previous cycles and have a amount of data already in their hands.

This rule ensured it was harder for existing teams to catch up, and for new teams (like oh I dunno NYYC) made it basically impossible. 

Now perhaps you'll get what Hutch was going on about in regards to NYYC and the previous Prot(including FA) making it un-winnable for them. ;-) 

Share this post


Link to post
Share on other sites

^ You seem a little confused. The framework agreement applied to everyone who signed it, including OR (the whole point was to create a level playing field and sustainable event) - and the reason the  NYYC couldn't 'challenge' while OR/GGYC held the cup was because the cup is defended by the club that holds it - just like SDYC couldn't 'challenge for the cup during the 132 years the NYYC held it.

  • Like 1

Share this post


Link to post
Share on other sites
38 minutes ago, weightless said:

Sorry, this has probably been covered. I'm just catching up. But, how is this design supposed to be self righting in sailing configuration? It doesn't pass the "scribbled lines in paint" test :) Is the plan to run the engines to drive the keels while the engines are upside-down and, perhaps, wet?

 

Not engines, motors (& batteries)

Share this post


Link to post
Share on other sites
41 minutes ago, weightless said:

Sorry, this has probably been covered. I'm just catching up. But, how is this design supposed to be self righting in sailing configuration? It doesn't pass the "scribbled lines in paint" test :) Is the plan to run the engines to drive the keels while the engines are upside-down and, perhaps, wet?

 

No engine aboard.  Batteries work upside down.

Share this post


Link to post
Share on other sites
11 hours ago, Xlot said:

Unless ... they're counting on taking off like Moths and A-cats, i.e. getting to max. displacement speed, quickly easing off the sail to unload the downwind foil, climb up, quickly sheet in to accelerate. Jean Sans's estimate for take-off speed was 22 kts (20 kts VMG) with entire load on one foil, down to 16 kts with load on both foils. But would this work for such a beast?

 

Different subject: the sail. From what I remember, going to a non-slotted solid wing doesn't help for taking off, since the max. section lift coefficient remains the same or is actually lower than with a wing mast/single battened sail. It would lower drag coefficient though, hence max. speed - is it worth it?

The fact that the hull is far inboard of the foils will produce (IMO) a much smoother transition between lowriding and flight - think of Dogzilla, except replace the leeward ama with a foil - which means there will be a large 'grey area' rather than the sharp delineation we saw with the cats

Here's a simple way to unpack that: Accelerating from low speed on a cat, both the foil and the the leeward hull are loaded up until such a speed that the righting moment produced by the foil exceeds the heeling forces produced by the rig - at that point, the hull very quickly lifts out of the water, and you are up and flying.

With this new geometry, once they get past 'falling over' speed, 100% of the righting moment is provided by the leeward foil*, which means that the center hull is already beginning to unload and lift (since righting moment simultaneously counts as buoyancy) from the very beginning of the acceleration curve in a very linear way, so I could imagine a much smoother transition which would also (besides facilitating early takeoff) lend itself to much smoother landings and recoveries from the inevitable touchdowns.

My takeaway from this is that the future of foiling might very well be tris rather than cats, and that (wild and out of control as it is at the moment) the Superfoiler might be the closest thing to the direction foiling will ultimately go.

* You could theoretically get additional righting moment with windward foil, but that would increase the effective displacement, since the force would be downward.

 

Share this post


Link to post
Share on other sites
6 minutes ago, MR.CLEAN said:

No engine aboard.  Batteries work upside down.

Adding motors and lithium batteries to the AC 50s would have solved 90% of the 'issues' with them, too - just sayin'!

In fact, I bet that's exactly what they are going to do.

Share this post


Link to post
Share on other sites
56 minutes ago, surfsailor said:

My takeaway from this is that the future of foiling might very well be tris rather than cats, and that (wild and out of control as it is at the moment) the Superfoiler might be the closest thing to the direction foiling will ultimately go.

The Superfoiler configuration has many obvious advantages over the proposed AC75 design.

(1) The central hull can be very narrow which reduces drag at displacement speed and helps with take-off.

(2) The armas are permanent, which makes them easier to engineer.

(3) The foils are shorter, which makes them easier to engineer.

(3) The boat is stable due to its width.

(4) The windward armas is less dangerous to other boats in a collision than a metal t-foil.

Righting the Superfoiler is made easier by the leeward arma filling with water and the boat floating on its side with the central hull at water level.

I can't think of any good reason to use the AC75 design.

 

Share this post


Link to post
Share on other sites
48 minutes ago, Stingray~~ said:

Why is ‘Washington state’ the location of a designers meeting?

Really? Don't ask and manage to sneak in there :D

 

Share this post


Link to post
Share on other sites
9 minutes ago, Fireball said:

The Superfoiler configuration has many obvious advantages of the proposed AC75 design.

(1) The central hull can be very narrow which reduces drag at displacement speed and helps with take-off.

(2) The armas are permanent, which makes them easier to engineer.

(3) The foils are shorter, which makes them easier to engineer.

(3) The boat is stable due to its width.

(4) The windward armas is less dangerous to other boats in a collision than a metal t-foil.

Righting the Superfoiler is made easier by the leeward arma filling with water and the boat floating on its side with the central hull at water level.

I can't think of any good reason to use the AC75 design.

 

I get all that, and don't really disagree - for sure they've engineered themselves a little bit into a corner because the AC boat has to be a 'monohull', so they've eliminated the buoyant part of the amas and are compensating for that with the giant articulated spider arms.

But having said that, to address your points:

1) Amas or no, the central hull will be little more than a 'launch vehicle' (it's not going to provide much static righting moment regardless) so the shape will absolutely be optimized for getting the thing from zero to take off velocity - and they have 75 feet to work with.

2) You'll get no argument from me on this one lol. Plus much smaller motors to lift foils (less weight) since there would'nt be the massive torsional loads.

3) A fair amount of the foil engineering difficulty is proportionate to the wing span, regardless of whether it's an ama or just an arm with a wing on it. The non-submerged part of the spider arm can be whatever they want it to be, including an 'A-arm', so they have some options there.

3B) Yes, adding flotation to the amas and eliminating the max draft mode of the new concept would be a lot simpler - but then it wouldn't be a 'monohull'.

4) Probably  - but any two 75' boats colliding at a closing speed of 40-100 kts is going to be pretty deadly, so whats a little more danger?!

One good reason - they wanted a monohull, goddammit!!!! :lol:

Share this post


Link to post
Share on other sites
1 hour ago, surfsailor said:

^ You seem a little confused. The framework agreement applied to everyone who signed it, including OR (the whole point was to create a level playing field and sustainable event) - and the reason the  NYYC couldn't 'challenge' while OR/GGYC held the cup was because the cup is defended by the club that holds it - just like SDYC couldn't 'challenge for the cup during the 132 years the NYYC held it.

Agreed, but you are referring to country right? ie if another club from the US wanted to participate it would need to participate in a defenders series.

 

Share this post


Link to post
Share on other sites

^ I was referring to your 'point' that the framework agreement somehow shut out the NYYC. It didn't. Nor was it a lack of a defender series (which are held at the discretion of the defending club - you'll note that RNZYS isn't holding one) - it was the simple fact that the NYYC did not hold the cup, so they couldn't defend it. If one of the teams that signed onto the framework agreement had won, the NYYC could've challenged.

 

Share this post


Link to post
Share on other sites
1 hour ago, Xlot said:

Not engines, motors (& batteries)

 

1 hour ago, MR.CLEAN said:

No engine aboard.  Batteries work upside down.

I really do need to catch up :) Sorry for the noise. Is there an automatic system for moving the keels to right the boat in the event of a crash? Thus, "self-righting". Have the details and implications of that been hashed out already?

Share this post


Link to post
Share on other sites
8 minutes ago, surfsailor said:

I get all that, and don't really disagree - for sure they've engineered themselves a little bit into a corner because the AC boat has to be a 'monohull', so they've eliminated the buoyant part of the amas and are compensating for that with the giant articulated spider arms.

But having said that, to address your points:

1) Amas or no, the central hull will be little more than a 'launch vehicle' (it's not going to provide much static righting moment regardless) so the shape will absolutely be optimized for getting the thing from zero to take off velocity - and they have 75 feet to work with.

2) You'll get no argument from me on this one lol. Plus much smaller motors to lift foils (less weight) since there would'nt be the massive torsional loads.

3) A fair amount of the foil engineering difficulty is proportionate to the wing span, regardless of whether it's an ama or just an arm with a wing on it. The non-submerged part of the spider arm can be whatever they want it to be, including an 'A-arm', so they have some options there.

3B) Yes, adding flotation to the amas and eliminating the max draft mode of the new concept would be a lot simpler - but then it wouldn't be a 'monohull'.

4) Probably  - but any two 75' boats colliding at a closing speed of 40-100 kts is going to be pretty deadly, so whats a little more danger?!

One good reason - they wanted a monohull, goddammit!!!! :lol:

It's not hard to come up with more advantages. 

(4B) The windward arma is more robust than a metal t-foil in low speed collisions such as pre-start manuouvers.

Another point is that the Superfoiler is an actual boat that has reasonable performance based on a very small development budget in comparison to the AC teams.

The AC teams on the other hand seem to stuck with their heads in their computers and don't seem to want to go sailing. ETNZ doesn't even have their sailors on contract yet - they are a design only operation right now - the process is bizarre.

Share this post


Link to post
Share on other sites

^ Luckily it's not our money! But I expect that there will be some really cool technological developments, due to the fact that they will be able to control foil cant to an extreme degree (like kite surfers), which means they can control leeway at the same time as they have access to just massive amounts of righting moment - until it all goes pear-shaped, of course.

Mind you, this is from the vantage point of someone who (at the moment) has his head stuck in a computer designing foils, and barely has time to go surfing much less sailing. The surf is good, too.

Share this post


Link to post
Share on other sites
26 minutes ago, surfsailor said:

Mind you, this is from the vantage point of someone who (at the moment) has his head stuck in a computer designing foils, and barely has time to go surfing much less sailing. The surf is good, too.

And in Maui. Sorely tempted to give you one negative reputation point :D

 

Share this post


Link to post
Share on other sites
42 minutes ago, Fireball said:

It's not hard to come up with more advantages. 

(4B) The windward arma is more robust than a metal t-foil in low speed collisions such as pre-start manuouvers.

Another point is that the Superfoiler is an actual boat that has reasonable performance based on a very small development budget in comparison to the AC teams.

The AC teams on the other hand seem to stuck with their heads in their computers and don't seem to want to go sailing. ETNZ doesn't even have their sailors on contract yet - they are a design only operation right now - the process is bizarre.

"ETNZ doesn't even have their sailors on contract yet - they are a design only operation right now - the process is bizarre"

Most teams don't have sailors on contract yet. Its the AC, its always like this in between events.

Share this post


Link to post
Share on other sites
2 hours ago, surfsailor said:

^ I was referring to your 'point' that the framework agreement somehow shut out the NYYC. It didn't. Nor was it a lack of a defender series (which are held at the discretion of the defending club - you'll note that RNZYS isn't holding one) - it was the simple fact that the NYYC did not hold the cup, so they couldn't defend it. If one of the teams that signed onto the framework agreement had won, the NYYC could've challenged.

 

No that wasn't my point at all.. I'm well aware that NYYC didn't hold the cup - I'm not sure what's confusing you about what I wrote - the FA ensured that teams who signed it were restricted with their development activities. This makes it hard for *any* new entrant irrespective of whether they were in a challenger or defender series of they were part of the FA.

Share this post


Link to post
Share on other sites
2 hours ago, Fireball said:

The AC teams on the other hand seem to stuck with their heads in their computers and don't seem to want to go sailing. 

Go sailing in what?

Share this post


Link to post
Share on other sites
4 hours ago, Stingray~~ said:

Why is ‘Washington state’ the location of a designers meeting?

Weed is legal there.

  • Like 3

Share this post


Link to post
Share on other sites
On 03/02/2018 at 6:13 PM, Xlot said:

Downwind  I understand: in 14 kts TWS the boat reaches 20 kts in displacement mode, at which point it takes off and accelerates to 35 kts. While manouvering, the boat may slow down to 20 kts before it falls off the foils

It's upwind that it doesn't seem to make sense. Indeed, one possible interpretation of the graph might even be that the boat cannot take off while going upwind, its speed in displacement mode being capped at 16 kts, less than the 20 kts needed for take-off

As we don't speak of vmg but speed on a vmg course I was wrong and you may be right.

Share this post


Link to post
Share on other sites

This is what happened with a small 17 ft cat, pretty much the same as Franck Cammas with a GC 32.

I don't want to think about the results of the same accident with these huge 75 ft launched at 50 kts....They have to think of serious safety systems.

Sailing pic Didier Hillaire. We received this mail below from Marcus Spillane Nacra 17 Class President.  Digging a bit more I found this pic to the left and additional details at Sejlerlandsholdet / Danish Sailing Team fb, it seems Christian fell from his trapeze and the rudder blade cut made a serious cut in his leg. Also that surgery went well and he is recovering. Good to see him in pic to the left along Coen de Koning.

http://www.catsailingnews.com/

 

Share this post


Link to post
Share on other sites

Another reading (more likely) is that the foiling transition commences at 8 knots TWS.

Taking their published estimate of (approx) 32 knots boatspeed upwind in 20 TWS:

 

TWA (estimate) 35

AWA  13 (indicating rig similar to AC50)

AWS 50

VMG 26

This, one could imagine, would be near the achievable limits.

Share this post


Link to post
Share on other sites

So maybe this thing would have at least two rigs,  bit like the (restricted) 18s now, to give range  at full RM from 8 to 25 TWS?

Share this post


Link to post
Share on other sites
1 hour ago, Frogman56 said:

So maybe this thing would have at least two rigs,  bit like the (restricted) 18s now, to give range  at full RM from 8 to 25 TWS?

Froggy, 56 like your birthdate or Morbihan ?

Share this post


Link to post
Share on other sites

i wonder what would have happened if TNZ gave LR the finger and gone with a multi regardless

i guess it would be a bit dog

would they have been slapped with a law suit or a DOG challenge, or was it just a gentlemans agreement

Share this post


Link to post
Share on other sites
1 hour ago, inebriated said:

i wonder what would have happened if TNZ gave LR the finger and gone with a multi regardless

i guess it would be a bit dog

would they have been slapped with a law suit or a DOG challenge, or was it just a gentlemans agreement

GD said it was a handshake - both relished the fact that they could take each other at their word.

ETNZ and LR have had a long relationship with which to build up trust.

Share this post


Link to post
Share on other sites
Just now, rh2600 said:

GD said it was a handshake - both relished the fact that they could take each other at their word.

ETNZ and LR have had a long relationship with which to build up trust.

ok

it would have been some good drama if they turned on LR after all that $$$$

probably fair enough though hahaha

Share this post


Link to post
Share on other sites
2 hours ago, inebriated said:

i wonder what would have happened if TNZ gave LR the finger and gone with a multi regardless

i guess it would be a bit dog

would they have been slapped with a law suit or a DOG challenge, or was it just a gentlemans agreement

Both GD and LR had previously stated that they preferred monos so they would never change their mind and go to multis.

Share this post


Link to post
Share on other sites
6 hours ago, Frogman56 said:

Another reading (more likely) is that the foiling transition commences at 8 knots TWS.

Taking their published estimate of (approx) 32 knots boatspeed upwind in 20 TWS:

 

TWA (estimate) 35

AWA  13 (indicating rig similar to AC50)

AWS 50

VMG 26

This, one could imagine, would be near the achievable limits.

What is the definition of "VMG" here? Is it a nominal VMG in the centre of the course?

Share this post


Link to post
Share on other sites
7 hours ago, Tornado-Cat said:

Sailing pic Didier Hillaire. We received this mail below from Marcus Spillane Nacra 17 Class President.  Digging a bit more I found this pic to the left and additional details at Sejlerlandsholdet / Danish Sailing Team fb, it seems Christian fell from his trapeze and the rudder blade cut made a serious cut in his leg. Also that surgery went well and he is recovering. Good to see him in pic to the left along Coen de Koning.

http://www.catsailingnews.com/

Actually the AC75 might be less risky regarding cuts by rudder or foils for the on board crew. They will have a single rudder, in the middle of the boat. If a man fall, he is less likely to be caught by this rudder which has a greater lateral distance than for a cat.

Regarding the foils, there is less risk for crew members to fall on AC75 than AC50 where they could fall in front, in between the hulls with a higher risk to be caught by a foil. 

It's really collision between boats which might be scary. Even capsizes which are more likely to occur than in AC50 shouldn't be as dangerous.

  • Like 1

Share this post


Link to post
Share on other sites

Rob G,

VMG is just Velocity Made Good against (theoretical) dead upwind wind direction.

So VMG = Boatspeed  x cos TWA

Measured TWA (from the 'boats instruments') includes leeway. In this case 35 degrees TWA is a fair guess, but if its wrong by a few degrees, the boatspeed increases but the minimum efficient AWA remains.

So:

Boatspeed:  32

TWA:   35

Cos 35:  0.82 approx.

32 x 0.82 = 26. xx

Share this post


Link to post
Share on other sites
9 hours ago, Frogman56 said:

VMG is just Velocity Made Good against (theoretical) dead upwind wind direction.

So VMG = Boatspeed  x cos TWA

Thanks, so just upwind VMG as opposed to toward the mark.

Share this post


Link to post
Share on other sites
1 hour ago, RobG said:

Thanks, so just upwind VMG as opposed to toward the mark.

True but it means basically the same thing if you’re within your laylines.

Some people use CMG (Course MG) when talking marks and when reaching (especially in a current) it makes sense; but others use the CMG term with different meanings.

VMG is what means most when going either up or down.

Share this post


Link to post
Share on other sites
22 hours ago, Frogman56 said:

Another reading (more likely) is that the foiling transition commences at 8 knots TWS.

Taking their published estimate of (approx) 32 knots boatspeed upwind in 20 TWS:

 

TWA (estimate) 35

AWA  13 (indicating rig similar to AC50)

AWS 50

VMG 26

This, one could imagine, would be near the achievable limits.

Can you elaborate on why you think transition happens at 8kts? I am thinking that it happens at more like 13, on the way up and down. 8 kts is what happens after you come off the foils, which happens when you are foiling and go below 13 kts. If you are displacement and go above 13, you go up on foiles, and if you are foiling and go below 13, you come down back to displacement. This chart has data on it, but it is presented in a way that is easy to misunderstand. And labeling it "VMG" does not help. It seems to show boat speed through the water vs true wind speed with respect to the water, but in "VMG Mode", which is the most efficient upwind or downwind mode. Seems like it's very hard to show these things clearly, but there are some standard ways, and this isn't one that I am familiar with. Perhaps a polar diagram would be nicer.

Share this post


Link to post
Share on other sites

Actually, VMG is velocity made good up or downwind.  If you're directly downwind of the weather mark, then it's the same as VMC, but if you're on the layline, your VMC (to the mark) equals your boat speed, so not exactly correct to say "as long as you're inside the laylines".  The graphs would be best labelled as "boat speed when sailing optimal course to weather"

  • Like 1

Share this post


Link to post
Share on other sites

I had predicted that flexy OR1 would pitchpole with the winward bow, I now make the prediction that some AC75 will capsize on windward.

The main advantage of a cat is not only the RM, it is also safer to winward "dessalages". They lose part of this advantage with foils, but the winward hull prevents catastrophies.

The AC75 is a huge mono the crew is represented by the ballasted winward foil. While a small mono crew can get in easily, AC75 ww foils will weight a lot and, when the boat falls to winward, will hook the water at 40 kts which will at best stop the boat, probably make it capsize or, hopefully not,  disintegrate it.

Up to now I thought they would chose narrow and light hulls to foil early, now I begin to think they need strong and wide hulls for safety. Another solution would be to angle the ww foil so that it provides lift if hitting the water, not sure that can do it though.

It will be interesting to compare design choices. As for on the water, w'll have Roman Ben Hur chariot races !

Share this post


Link to post
Share on other sites
On 05/02/2018 at 3:28 PM, Frogman56 said:

Another reading (more likely) is that the foiling transition commences at 8 knots TWS.

The foils start to lift as soon as you get forward motion.  The amount of lift depends on the shape of the foils and the forward speed .. it is useless to speculate when we do not know anything about the foils.

Share this post


Link to post
Share on other sites
1 hour ago, Tornado-Cat said:

rI had predicted that flexy OR1 would pitchpole with the winward bow, I now make the prediction that some AC75 will capsize on windward.

The main advantage of a cat is not only the RM, it is also safer to winward "dessalages". They lose part of this advantage with foils, but the winward hull prevents catastrophies.

The AC75 is a huge mono the crew is represented by the ballasted winward foil. While a small mono crew can get in easily, AC75 ww foils will weight a lot and, when the boat falls to winward, will hook the water at 40 kts which will at best stop the boat, probably make it capsize or, hopefully not,  disintegrate it.

Up to now I thought they would chose narrow and light hulls to foil early, now I begin to think they need strong and wide hulls for safety. Another solution would be to angle the ww foil so that it provides lift if hitting the water, not sure that can do it though.

It will be interesting to compare design choices. As for on the water, w'll have Roman Ben Hur chariot races !

You could spend all day listing out the flaws in this new design.

They predict they will get up to 50 knots boatspeed, so let's imagine a nosedive at 50 knots (92.6 km/h). The best hull shape for this situation is long and very narrow, so you get reserve bouyancy to prevent a pitchpole,  but the deceleration is not too rapid (that's where the multihull comes in!)

Now imagine the loads and the deceleration when a wide monohull nosedives at 50 knots! We're talking crew restraints (seatbelts) and airbags here - otherwise there are going to be fatal injuries to the crew.

The best case scenario (and the most likely) is that the performance of the AC75 is not going to be anything like the claims being made. Otherwise, they will be a safety nightmare.

  • Like 2

Share this post


Link to post
Share on other sites
1 hour ago, Fireball said:

 

They predict they will get up to 50 knots boatspeed, so let's imagine a nosedive at 50 knots (92.6 km/h). The best hull shape for this situation is long and very narrow, so you get reserve bouyancy to prevent a pitchpole,

 

It's a theory, however I prefer cats with strong bows and mono volume in front may prevent them from pitch poling. That said, we may watch some pp !

Share this post


Link to post
Share on other sites

Maybe all the crew can sit in padded fox holes, that way they are only exposed during tacking or gybing when crossing the boat, if that even needs to happen? Or harnesses with inertia reels attached to the back of the boat.

Share this post


Link to post
Share on other sites
On 2/4/2018 at 8:54 AM, MR.CLEAN said:

Why?  50s were quicker.

Fair enough. See I did miss something.

Guess I was not paying attention  as Bermuda was so far from my house.

Share this post


Link to post
Share on other sites
8 hours ago, RobG said:

Thanks, so just upwind VMG as opposed to toward the mark.

If you're going upwind, meaning you can't lay the mark and a tack will be needed, then the fastest speed to windward (Vmg) is the rate of progress toward the mark. 

The velocity component toward the mark is not very useful when on upwind and downwind (meaning a gybe is required) legs.  Dead downwind of the mark, the  velocity component toward the mark equals Vmg.  When the boat approaches the layline, the velocity component in the direction of the mark is near zero, but the velocity toward the mark equals the boatspeed just after tacking on the layline.  That's why Vmg is always referenced to the wind direction.

Share this post


Link to post
Share on other sites
On 2/3/2018 at 10:26 AM, MR.CLEAN said:

hutch, Phil Lotz, and Hap Fauth presented a bunch of stuff about their campaign this morning at the US Sailing Leadership Forum.  

IMG_8737-1.JPG

 

 

 

I think these numbers are, um, shall we say, "optimistic"? 

I've made some guesses as to consistent boat speeds and angles to match these Vmg numbers.  Upwind, the boat has to touch 50 kt, and it looks like downwind it will be doing 55 kt over a fairly wide wind range.  (Note that I've multiplied the downwind apparent wind angle by 10 to get a better fit to the graph scale.)  Apparent wind angle here is defined as between the apparent wind vector and the course through the water.

In order to do these kinds of speeds without cavitating, the foils will have to be thin - on the order of 7% of the chord.  This is interesting when you consider the volume needed to provide the stated amount of ballast.  Steel and carbon composite are similar in stiffness, but steel can bend more without breaking.  So I suspect the foils may be solid steel, but I've not tried to work out just how much area that would be for the weight.

There was an interesting line in the presentation where they said the foils may be one-design except for the trailing edges and control systems.  This would lock in most of the section shape and cavitation characteristics.  

I haven't looked at the hullborne numbers, yet.  But one thing is clear - for those that want to see Code 0s being set and dowsed, there will either be Code 0s or foiling, but not both in the same race.  There's no point in flying a Code 0 when the apparent wind angle is less than 15 deg.DnwindVmg.thumb.png.f3a408ec749c6c1dd5375b8a4b23da13.png

UpwindVmg.png

Share this post


Link to post
Share on other sites
33 minutes ago, Basiliscus said:

I think these numbers are, um, shall we say, "optimistic"? 

I've made some guesses as to consistent boat speeds and angles to match these Vmg numbers.  Upwind, the boat has to touch 50 kt, and it looks like downwind it will be doing 55 kt over a fairly wide wind range.  (Note that I've multiplied the downwind apparent wind angle by 10 to get a better fit to the graph scale.)  Apparent wind angle here is defined as between the apparent wind vector and the course through the water.

In order to do these kinds of speeds without cavitating, the foils will have to be thin - on the order of 7% of the chord.  This is interesting when you consider the volume needed to provide the stated amount of ballast.  Steel and carbon composite are similar in stiffness, but steel can bend more without breaking.  So I suspect the foils may be solid steel, but I've not tried to work out just how much area that would be for the weight.

There was an interesting line in the presentation where they said the foils may be one-design except for the trailing edges and control systems.  This would lock in most of the section shape and cavitation characteristics.  

I haven't looked at the hullborne numbers, yet.  But one thing is clear - for those that want to see Code 0s being set and dowsed, there will either be Code 0s or foiling, but not both in the same race.  There's no point in flying a Code 0 when the apparent wind angle is less than 15 deg.DnwindVmg.thumb.png.f3a408ec749c6c1dd5375b8a4b23da13.png

UpwindVmg.png

There was a clarification on the SA frontpage. The numbers in the NYYC presentation are boatspeeds when sailing the maximum upwind and downwind VMG angles.

So they are (only) claiming boatspeeds of 40 knots upwind and 50 knots downwind.

 

Share this post


Link to post
Share on other sites

Hi Basiliscus, I'm focusing more on transition to foiling. Don't know if you've seen this study 

https://translate.google.com/translate?hl=&sl=fr&tl=en&u=https%3A%2F%2Fwww.uncl.com%2F2017%2F12%2F01%2Ftechniques-innovations%2Fnouvel-ac-75-nz-jean%2F

The author assumes Cl = 0.38 and gets a take-off speed of 16 kts if both foils are equally loaded, vs. 23 kts with entire weight on one foil. Your opinion? Thanks

 

P.S.: the second part of the study

https://www.uncl.com/2018/01/10/techniques-innovations/nouvel-ac-75-nz-jean-vol/

considers preliminary aspects of dynamic stability, you mignt find it more interesting

Share this post


Link to post
Share on other sites
On 2/4/2018 at 11:36 AM, jorge said:

IMHO no way these AC 35 are going to be faster than a AC50, and no way they are going to foil easier than ac 50 or 72

I can see faster, but not foiling easier/quicker...

Share this post


Link to post
Share on other sites
On 2/4/2018 at 12:48 PM, Stingray~~ said:

Why is ‘Washington state’ the location of a designers meeting?

Because Washington State is the shit... Plus we have Paulie B here (except PB is not taking part in the design - a little consulting, but thats it.)...

Share this post


Link to post
Share on other sites
21 hours ago, Fireball said:

There was a clarification on the SA frontpage. The numbers in the NYYC presentation are boatspeeds when sailing the maximum upwind and downwind VMG angles.

So they are (only) claiming boatspeeds of 40 knots upwind and 50 knots downwind.

 

I wouldn't call it a clarification, more like a speculation since it didn't come from BMQR.   After all, who talks about "Vmg courses" instead of "windward-leeward courses"?  Maybe that's a translation from French?  But it is a way of getting to more sensible numbers.

Here's a guess at filling out the rest of the picture, assuming the figures represented boat speed instead of Vmg.  I'm guessing Vmg downwind to be 15 - 44 kt, and 13 - 28 kt upwind.  Apparent wind angles of 18 - 24 deg downwind are not very different from the catamarans.  I still think they are too tight for Code 0s to be useful when foiling.  

DnwindBS.png

UpwindBS.png

Share this post


Link to post
Share on other sites
On 6.2.2018 at 2:49 AM, Tornado-Cat said:

I had predicted that flexy OR1 would pitchpole with the winward bow, I now make the prediction that some AC75 will capsize on windward.

The oracle has spoken.....

^ Great work...and thanks for the 'Ros Bif' version

Is there another phrase for 'windward capsize' ? I suspect that one might get used a bit :D

Share this post


Link to post
Share on other sites
14 hours ago, Basiliscus said:

I wouldn't call it a clarification, more like a speculation since it didn't come from BMQR.   After all, who talks about "Vmg courses" instead of "windward-leeward courses"?  Maybe that's a translation from French?  But it is a way of getting to more sensible numbers.

Here's a guess at filling out the rest of the picture, assuming the figures represented boat speed instead of Vmg.  I'm guessing Vmg downwind to be 15 - 44 kt, and 13 - 28 kt upwind.  Apparent wind angles of 18 - 24 deg downwind are not very different from the catamarans.  I still think they are too tight for Code 0s to be useful when foiling.  

DnwindBS.png

UpwindBS.png

Nice - Thank you!

Re: ‘I'm guessing Vmg downwind to be 15 - 44 kt, and 13 - 28 kt upwind.‘

Wouldn’t that be faster than even the AC50? Yowza.

Share this post


Link to post
Share on other sites

^ Keep in mind that the VPP data Basiliscus based his calculations on was from November (via a team who probably doesn't have direct access to models ETNZ and LR are using to create the rule). For sure the potential is there for extraordinary speeds based on righting moment, but realizing that potential in the open ocean with semi-soft sails might be another story.

Share this post


Link to post
Share on other sites

Its not quite open ocean, but the upwind numbers in particular are ambitious for soft sails......

Share this post


Link to post
Share on other sites
7 minutes ago, us7070 said:

so, sorry if it's been covered.., but; are the grinders going to be generating the power to move the foils up and down?

No

Share this post


Link to post
Share on other sites
37 minutes ago, us7070 said:

so, will it use some sort of stored power?

Yes, a battery-powered boat is apparently the only way to try match the fully manual AC50’s, if you are forced to go ‘mono.’

Except for the 2010 DoG Match, when SNG changed their Sailing Rules to allow engines and tried to hide it, this is an AC first. Imo it’s an okay step but, like with the auto-intelligence Herbie to the Hilt that ETNZ deployed in AC35, the rules need to very carefully this time curtail the use of stored power, including stored AI intelligence power, to some reasonable threshold or it will detract too much from the sporting element of the game. THutch referred to what ETNZ did ‘legally’ to break through the last Rule to get the win and it was a relevant point.

Share this post


Link to post
Share on other sites
37 minutes ago, Stingray~~ said:

Yes, a battery-powered boat is apparently the only way to try match the fully manual AC50’s, if you are forced to go ‘mono.’

Except for the 2010 DoG Match, when SNG changed their Sailing Rules to allow engines and tried to hide it, this is an AC first. Imo it’s an okay step but, like with the auto-intelligence Herbie to the Hilt that ETNZ deployed in AC35, the rules need to very carefully this time curtail the use of stored power, including stored AI intelligence power, to some reasonable threshold or it will detract too much from the sporting element of the game. THutch referred to what ETNZ did ‘legally’ to break through the last Rule to get the win and it was a relevant point.

Wasn't the ETNZ AC72 battery powered also? As I understand it, that was the reason they withdrew in the LV final, because their foil control battery packs weren't fully charged.

Share this post


Link to post
Share on other sites
53 minutes ago, us7070 said:

so, will it use some sort of stored power? 

The system will use battery powered electric motors .. maybe 10 kw .. It could be electro hydraulic or electro mechanical .. they haven't decided yet.

I favour electro mechanical because the ball screws are more efficient than hydraulic rams and can restore energy when the foils go down.

The latest aircraft also use ball screws.

Share this post


Link to post
Share on other sites
4 hours ago, Stingray~~ said:

Yes, a battery-powered boat is apparently the only way to try match the fully manual AC50’s, if you are forced to go ‘mono.’

 

The AC50's were about as "fully manual" as an F1 with paddle shift.

Share this post


Link to post
Share on other sites

^ Some more than others. Flight control was done by the driver on all of the boats except one - using hydraulic power to be sure, but still an essentially 'manual' operation like steering.

Share this post


Link to post
Share on other sites

I suppose that flapping the foils a few times in marginal foiling conditions could generate a little extra speed to get on the foils sooner.  But they wouldn't do that.  ;-)

Might be a great low speed maneuver in prestart though.  You could flap directly to weather or use it for turning moment.  Dial ups will be interesting.

Share this post


Link to post
Share on other sites
16 hours ago, sclarke said:

Wasn't the ETNZ AC72 battery powered also? As I understand it, that was the reason they withdrew in the LV final, because their foil control battery packs weren't fully charged.

The AC72s were allowed to have battery powered hydraulic valves, but the motive power of the hydraulics themselves had to be manual.  That is apparently not the case for the AC75, which will use battery power to actually move the foils.

I thought the use of powered systems in the 33rd AC Match was wrong, and wish they weren't going this route for the 36th AC Match.  There were things outlawed in recent matches that I think should have been allowed.  Like regenerative hydraulic systems that would have extracted power from slow retraction of the dagger foil, essentially using the weight of the boat sliding down the board to recharge accumulators before being reset by extending and tacking onto the the opposite board.  I believe this qualifies as use of the natural forces of wind and water, as the energy comes from the boat flying back up on the opposite tack.  

I think it would make more sense to allow the control systems to be hydromechanical with accumulators but no battery power for the actuation of valves.  Any kind of mechanical feedback control would be permitted.  Essentially we're talking about aircraft flight control technology circa 1960.  This would also encourage the development of controls technology that would be usable by cruisers and offshore racers where reliance on electronics for safety-critical functions is problematic.  One of the problems is this kind of hydromechanical control technology is a bit of a lost art.  Today's engineers understand CAN busses and there is a lot of off-the-shelf hardware available, but they don't have any experience with mechanical flight control systems.

  • Like 2

Share this post


Link to post
Share on other sites

^ I was also disappointed that they did not allow energy recovery systems in AC35. The current mindset regarding stored power is a weird dichotomy - accumulators are 'bad', but somehow, having an engine/motor and fuel/batteries is 'ok'. I suppose this is because sailors have gotten used to the motors running 24/7 on the canting keel boats. In any case, I'm thinking that ship has sailed - I really don't see any way  the giant spider arms on the AC 75s are going to be moved around with unassisted human power.

Re electromechanical foil systems - they could use energy recovery systems as well, and combined with PV and a really clever electronic control system (that for example momentarily manipulated the foil AoA/flap to assist raising or lowering), such a system might not require that much power (could possibly be completely self sustaining). So in terms of application to offshore racers (thinking IMOCA here), that could turn out to be a big improvement over the motors they run now. 

  • Like 2

Share this post


Link to post
Share on other sites