90 x 90 Race Multi

BYM News has it ... as do other sailing sites.

Ed B was driving and stuffed it in about 20knots of breeze.

Broken mast, but boat is back safe. Should be on a crane about now.

BMWO has rented/borrowed G2 for training and the two teams might have been on the water in Orma Tris at the same time ... but oops ...

There are photos of the BMWO yard ... they built a big tent, poured a concrete floor and tossed up some walls ... tent was empty until this morning ... glimpses of great large lumps inside ... second boat is a SWAG ... but race is either July 08 or Oct 08 ...

Court hearing April 2 to decide date for sure ...

 

Thanks! Foils or no foils-that will be interesting to me.....

 

Just how do you depower those things in a hurry? Gotta be mechanical or you could lose your arm?

 

It is not always possible to dump the sheets fast enough to get the boat back.

Fast multi sailors learn how close the boat is to tripping and train themselves to have instinctive reactions to stay in control.

Imagine if the penalty for pushing too hard and broaching (monos) gets replaced by capsize or pitchpole (multis). Fast mono sailors tolerate a broach or knock down now and then ... the same actions gets you a swim and likely ends your day in a fast multi. Not much room for error.

 

Not only does it end your day, it likely ends your regatta at the speeds these boats travel. Looking at the damage to Foncia (blown carbon mast and ruptured aft beam) if this were the AC racing, then they'd simply be completely done, finished, kaput... Cup to the other guy, no matter how much slower he might have been. That, or have duplicates of everything in the spare parts bin and have the capability to exchange it all before the next day's race.

The shot below shows what was happening on Foncia to get them the pitchpole honor.

Here's the funny thing about the use of banana foils on boats like these. While they can lift the bow sections of the leeward ama and to some extent the vaka hull, as well, giving potentially faster speeds, they also have an inherent problem. These foils also lift the effective Center of Gravity and provide a very nice rotational fulcrum point around which the entire boat rotates should it be hit by a very large gust, such as encountered by Foncia.

Now, not only do the bows want to get wet, but they are being driven from a much higher point relative to the water, loading the pressure on the bows further until the boat lifts, the rudders are instantly lost as instruments of control and the boat is well beyond rescue. The same thing that happens to all multihuills in a similar scenario, just one hell of a lot faster and more violent.

For all you foiling nut cases out there, that's the bad medicine in the mix. In this case, not even a sailor with as heady a resume as Alan Gautier could effect a difference in the outcome. A truly sobering message for the boys from Alinghi.

When you live by the foil, you die by the foil.

 

Foil Madness

And you've got it Mr. Oslind. Trying to blame that accident on the foils is actually quite funny(as well as absolutely ridiculous) since the foil on the leeward hull has more lift force than the lee hull would have w/o it! No, I'd say that was crew error.....
However, most of the ORMA 60's don't have rudder t-foils-and such a foil on the lee hull and/ or on the main hull might have created a different outcome.
Where the foil causes a problem is in conditions where the lee hull flies clear of the water(along with the main hull). Then the pitch stability goes to hell and the boat can go any number of-not so pleasant- ways. But from what I've seen this wasn't even remotely related to the foil.
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Ed Baird:"As we were bearing away, always the highest risk situation on a multihull, both the leeward and the central hull dug into the water and the rudders came out. " If the boat had been flying the main hull and the leeward hull came clear of the water a crash could be possible but what usually happens is that the boat pitches up because the foil center of lift is ahead of the CG of the whole boat. Pictures leading up to this point would answer the question. But it seems apparent that the bear-away precipated the crash-not the foil.....

 

Then please give us a technical assessment regarding the altered COG due to lifted hulls and how that puts the boat in a more tenuous position.

You are right, it is funny that you solve everything with foils and can not address the issues that come with them.

 

Foils can be negative as well

Hello all

I was reminded of a few old incidents from the early days of foiling. One involved our Lock Crowther who put bow foils on his B class cat as well as the C class Helios. He was reaching on the B class when the bows dropped. He then flipped over so fast that the bloke behind called out (as her passed) "Do that again, I blinked and missed it"

One of Derek Kelsall's tris (again with bow foils) VSD capsized within sight of a freighter when they went down a wave and then pitchpoled. Everyone was saved.

What I remember reading about both incidents is that foils act upwards most of the time but if the boat becomes bow down they can of course act negatively. This happens as the boat wants to rotate through a large variation in trim usually due to a gust or swells.

If the bow goes down because of a wave or huge gust a foil can reduce the ability of the boat to quickly pull up. Todays active and sensor foils get around the problem but fixed foils will always have the ability to act in a way that you don't want if the bow goes go down.

cheers

Phil Thompson

 

Great set of references, Phil.

It's not just that the foils act as a tripping source with an elevated COG asyou mentioned, but also that when the bows do come down, they present a somewhat different buoyancy profiles to the water and allow the decks to drive additional tripping forces into the whole mess.

What we do not know, and I have not seen in any of the photos as of yet, is whether or not the leeward foil may have been catastrophically overloaded due to the monster gust. This breakage could have allowed the lee ama to plunge from its lifted riding position, immersing itself deeper in the water than if the boat had been riding on its amas without a lifting foil.

I understand Doug's response, as he has a huge amount of blabber invested in his claims for foil borne craft. It's a shame, really, that he will not recognize that lifting foils, with their apparent benefits in certain types of applications, also have some very serious penalties when conditions arise that do not favor their use. One can only hope that opinion of his will change.

Look at the realities of the solo RTW boats of Coville and Joyon. No ama mounted lifting foils on either boat for very good reason. Now, look at the lifting foil equipped maxi tri, G3, with its lifting foils. Which one of them had serious impact issues with unknown underwater object(s), possibly causing some of the propagation of damage to the eventually failed ama off New Zealand.

Hey! it was a great ride until the ama went blooey and the whole thing broke into bits. Yeah, those ama foils sure were a good idea. No wonder Joyon left them off the boat for his amazing run.

Nobody specifically blames the foils for the pitchpole, Doug. I'm suggesting that they contributed to an otherwise serious problem aboard, but may or may not have been the root cause for the flip. Overdriving a boat in a harsh condition would always lead to possible problems. When coupled with the issues present from the foils, it just makes the problem inordinately tougher to deal with. We await the truth-telling of an, after the fact, incident report from Gautier.

 

90x90 race multi

Have sailed foil yachts for 20 odd years, never end over ended or capsized BUT ..... my boats have inverted T rudder foils and in potential crashing or bow burying situations, the T keeps the stern down, lots of roaring and aerated water, but no out lifting. Also my fixed asymmetric foils in the floats are set at 2-3 degrees angle of attack, (no wands, no flaps - I think they cause more drag and ventilation problems) - you still have a slit, no matter how perfectly the foil/flaps are faired in. The foil Moths, even with their self regulating flaps, still crash impressively - but that is another story. An overlooked and important aspect of foils is that, even at so called negative angles of attack, they still provide lift. Lift at 45 degrees nose down would be minimal BUT .... you should never let a boat get into that position or situation in the first place - basic seamanship, mate (famous last words). Also the leeward foil keeps the hard pressed leeward float and main hull bows up - not flying high like Hydroptere but in reality, pretty flush with the water surface - so you are not canning your boat from high up in the air - so much for that theory. An aside: how many times has Hydroptere crashed? - I have heard nothing - and if any boat should go blue sea/sky/blue sea, it should, according to armchair theroists, happen regularly to that boat.

 

America's Cup sailed with Multihulls

Boost to Multihull Image

I was heavily involved with the multihull business back in 1988, when for the first time ever a wing-sailed 60' catamaran was unveiled to meet the rogue challenge from NZ by an unusally large custom monohull. The press went wild for awhile with stories and photos.

We thought, finally multihulls are going to get some respect. Well the Stars & Strips catamaran did clean up on the race course, but not that many minds were swayed.
Brian
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A couple of days ago, the infamous hi-speed monohuller Bill Lee wrote a short editorial in Scuttlebutt.....boy did he get some responders, and I don't think its over yet.

GUEST EDITORIAL -- Bill Lee
It is clearly time for the America's Cup to be raced in multihulls. If
The Cup is to include technology, it should be real breakthrough
advancement, not just trying to make the basic leadmine go 0.1 knots
faster. If is often argued that heavily ballasted boats are good for The
Cup because they can't squirt away from each other in a local puff,
Instead they will remain close and the racing will be tactical and
exciting. In reality, with the current boats and format, once one boat
wins the start, the lead seldom changes and the racing is rather boring.
If keeping the boats closer together is an objective, a far more
effective approach is to have much shorter races and many more of them.
An afternoon of racing should be the best 5 out of 9 with 15 minute
races and a strict 5 minutes in between.

Multihulls do have a much wider variety of spectacular and catastrophic
failure modes. For the team, avoiding these failure modes is the key to
winning. For the spectators, it is often the best part. There are other
advantages to multihulls. They weigh little more than a current AC boat
mast. What a savings in carbon fiber! The land based compounds can be
simpler and the need to ship (or fly) 40,000 pound bulbs is eliminated.
Less draft means venues can be closer in for better viewing. Multihulls
would attract huge new interest, both in technology and spectators.

"The Wizard says it's time." -- Bill Lee
______________________________________________________

....this was the initial posting I made on the subject a couple of years ago. I've cross-linked this subject thread as it had samiliar discussions, and some photos of the original America's Cup multihull.

 

LOL ... everything is a foil vs comon sense and experince ...

'the foil is still lifting with the bow down' any one want to retract that, or modify it before I blow it up?

It is known the banana foils on big tris can compound control problems. Newer designs have the ability to raise the foils under load ... why would anyone tackle that design problem for no reason?

A question and some insight from a multi guy on SA:
"... but does it have any low friction tracks in there to lift them (the foils) up while loaded? If not, the boards pull down very hard after bow down trim is a reality, and they most certainly slow the boat down very quickly inducing pitching moment due to inertial forces.

At least one groupama has a track to allow pulling it up under load, which can easily be done before bearing off. Now if it was down in the Foncia case, it wasn't the initial cause, but explains why the situation is out of hands after rudders lift. Without that issue, releasing halyard fast might have helped in that size of boat.

In a beach cat there is no time to do anything during the event. Unlike beach cats these boats can adjust sweepback of maindaggerboard. Tilting it aft prevents stalling rudders during bearing off, don't help after rudders are airborne of course."

I think he meant releasing sheet, not halyard (English is not his first language) ... but the main point is that yes, the boards/foils pull the ama DOWN when things go Tango Uniform.

When you stuff the bow and the AoA of the foil goes from normal trim to -10 deg ... the lift vector is down ... unless normal trim is greater than +10 ... now if you want to tell me that your design runs the ama foils at +10 or greater in normal trim ...

As EdB and the boys found out ... you don't just turn the rudder ...

Of course, early reports were "wind about 30" from sailors ... to their credit Alinghi came clean and said the wind was about 20 ... some gusts ... but no white squall deal ...

He turned the boat and it loaded up, started to run-away, and they stuffed it ...

The multi guys that have seen video, think they stuffed it, and it was an inertial capsize/pitchpole.

Stuff bow, boat slows, bows pitch down, lift on foil goes neg, drag on foil goes up, pulls bows down more, 12,000 pounds of boat at 20 knots ... part of it wants to stop and the rest keeps going ... basic stuff ...

 

Thanks for the post, Gary. So, let's look at what you said and compare that to the issue with the Foncia pitchpole. I'll break out your comments as individual quotes.

OK, right away this is a completely different scenario and it has only small relevance to the issue as presented with Foncia's pitchpole. Foncia has no such foils on their rudders and the issues are not the same.

Very nice, Gary, and I wish you the best with the setup... but I'm going to go way out on a llimb here and assume that you are not running banana foils in your amas. If you are, please supply a few photos of same, so we can all see them. The banana-style foils are extremely difficult to build, as you know and they have extremely high levels of loading, requiring very sophisticated engineering as well as much more complicated trunks to install in the amas. The ama mounted, straight foil issues are not relevant to the Foncia design. There is a similarity, in that your foils are in your amas, but it ends there. Again, not the same issue.

So, let's look at this angle of attack point more closely, as long as you choose to make it. Yes, I will agree that the foil will still be generating lift at a 45 degree nose down attitude. I would suggest, however, that the majority of lift being generated is not up, but forward, following the vector lines being generated (as long as the boat is moving forward) Along with that lift component, is a heavy duty drag component that has been induced by the angle of attack. This, I'm afraid, will contribute to the pitchpole, rather than
allow the boat to escape to a steady sailing state. When you couple this loss of lift with the drag component, you get a pair of hulls on the leeward side that are nosing themselves into oblivion. Soon enough the drag to drive ratio on the boat as a whole will be more than the upright condition can support. Voila! a successful pitchpole.

I suggest that the bananafoils have contributed to that mess for the same reason that they contribute to less wetted surface when they are working correctly and the boat retains a reasonable upright attitude. You get some and you have the big potential penalty when they are not oriented correctly.

I'm way to lazy right now on thie Sunday eve to go look-up the plethora of vid clips on youtube, showing ORMA 60's and the way they use their ama foils. Suffice to say, the amas are significantly removed from the water surface and wave top clutter, so that wetted surface from the foil forward, is nill. You do the math for the geometry relative to that fact and you will see that the entire forward half of the ama is well clear of the water.

From a casual observation and off the top of my head, this is several feet of clearance at times. It is this elevated position that raises the COG significantly. Enough, at times, that when a really large gust hits, the boat is well capable of toppling forward from the raised COG fulcrum, resulting in a much bigger driving force from the amas and vaka as they hit the surface pointed downward.

To pair this argument with your comments about Moths... I have also seen them take huge crashes while being tossed forward. Are you, in fact, stating that the extreme Moth pitchpole crashes are not due to being flipped forward from their own elevated COG positions? That would be news to me.

Actually, L'Hydroptere has crashed before. There's a well documented situtation in which one of the foils smashed into an unknown obstacle (shipping container, wayward whale, or just plain broken) in the water, causing the failure of that foil and a very sudden crashing of the boat back down to displacement mode. (Fairly slow boat that way, I would guess) And that brings to the discussion the very big problem of what to do with a flying, or foil assisted, boat with a smashed-off, or crap loaded foil. Perhaps you have some ideas on that topic Gary?

L'Hydroptere is a totally different animal and you already know that. It's a fully flying sailing craft with a much different foil system for much different purposes. The Foncia only uses foil assist and is not intended to fly in the same fashion as L'Hydroptere. Make your own proper references, but it's not the same thing.

Chris

 

Foil Madness

I can see a foil contributing to the end result of the event but suggesting that the event began because of the foil is probably not true.
And Chris, the banana foils are designed to work with the ama IN the water-they are NOT designed to lift the hull clear of the water but do that every now and then. It is very dangerous because then the foil becomes a surface piercing foil highly subject to ventilation. The partial immersion of the ama has long been assumed to be enough to control pitch-unless the ama is lifted clear of the water in which case there is NO pitch control and the boat is in a very,very precarious position. Some ORMAs have used a main rudder T-foil and Gitana has experimented with a non steerable t-foil just behind the rudder on the ama.
I'm not sure how correct it was but I estimated that an ORMA 60 with the main hull flying is designed to have the ama carry 30% of the load and the foil 70%. The ama buoyancy is critical for pitch control on those boats without a rudder t-foil.
On SA someone referenced a video that shows the ama in the water prior to the accident. Haven't found it yet.

 

I never said the ama was lifted clear of the water. I did say that I've seen several video clips of ORMA 60's so equipped while running at speed. Virtually, the entire forward section of the ama is well out of the water from the forward beam on. The boats so observed were running steadily at that attitude with a distinct, bow-up pitch.

You say in your post that 70% of the load is on the foil and not the ama bouyancy. That non-verified number you have produced would seem reasonable as the aft sections of the ama look to be the only surfaces in the water when riding on the foils. That description, alone, would set the COG higher than on other tris of the same size and power without banana foils for assist. It's nice of you to support the argument in this fashion.

It's real simple, Doug. Lift the COG and you increase the distance for the ama to travel in a bow down pitching motion. Increase the distance and you severely change the angle of attack for the ama when it enters the water when pressed. In so doing, you alter the buoyancy resistance shapes and also drive the ama under from an angle in which the form has much less resistance. Increase the angle of attack on the foil and the drag goes through the roof. Drag goes up with no corresponding reduction in heeling moment in the rig... and pooof! You have a Foncia in the hands of Alinghi.

Similar events happen for any multihull, Doug. They just get a whole lot worse when the ama has a banana lifting foil placed in that scenario. Produce said video that may or may not show the ama immersed when the situation started and you say nothing more than what has already been said here. As soon as the foil starts to generate drag in excess of positive upward lift with the bows depressed, it becomes a massive liability to the upright stability of the boat. The key would be to get that leeward foil up and out of the stream and take corrective action for getting the heeling/pitching moments under control.

Take off the foilmeister hat for awhile and look at it with an open mind and perhaps it will all come to you. I really don't know why you feel it necessary to argue this.