Great video on homepage and short article on training.

Cheshirecatman.

http://www.cammas-groupama.com/en/index.jsp

http://www.cammas-groupama.com/en/franck_cammas/actualites_cammas/actualites_team/actu_equipe_40.jsp

Realizing this is a promotional video, interesting to see the stern dragging in such flat water, or is this the normal attitude for tri's?

I saw that too - may have been too much of that lifting daggerboard in the water.

It does appear to have an odd attitude, but considering lateral resistance and the fact it is powered up (flying two hulls) there is little evidence of imbalance from the rudder(s) and the crew don't seem to be fighting with the boat. Looking closely, most of the spray appears to be a 'bow wave' with some interference from the foil but the flow at the stern looks quite clean for the speed. Also the refit suggests it isn't an original design fault.

http://www.cammas-groupama.com/en/trimarans/groupama2/actualites_groupama2/actu_groupama2_19.jsp

Cheshirecatman

These ORMA 60's are semi foilers.

The plates create enough lift to get the bows up so they can be driven harder down wind, and also, reduce drag as there is less drag with the hull up than is created by the extra drag by the sterns being down a little.

Take a look at any fast boat in the water (power boats too), it's going bow up, else it wouldn't be going as fast as possible. Pushing the nose down is slow, even slower when you stuff a wave!

A longer video is on YouTube.

That is because they have the power at the back and so bing pushed; also, when boats plane, they adopt a bows up attitude.

Normal ? I don't know , but I do know that the inwardly canted daggerboard (bruce foil) is producting so much lift that it is foiling almost the entire weight of the boat and that is why it is lifting the lee hull clear of the water. ORMA 60 tris tend to do this above 30 knots boatspeed.

So if a very large portion of the weight is effectively foiled off the bruce foil then we can't really talk about dragging the sterns anymore as these are now only acting as a sort of trim tab. Meaning the associated drag coming off these "dragged sterns" is probably very modest and much lower then the dag reductions gained by going foiling.

I guess it won't be long till we'll see some T-foil fitted to the rudders. Then the system will selfregulate and adjust the tail dragging to the right angle of attack required by the foil. Then we'll be seeing a small jump in ORMA 60 performance.

Wouter

You notice how flat the water is, that helps!

What are the chances of seeing something similar in the race for the auld mug?

Cheshirecatman

Gitana's Orma60 did have a t-foil rudders at one point - I remember seeing a photo of them capsized and they explained that while the t-foil rudders did certainly gain traction, when they lost grip with the water, it resulted in a very fast pitchpole.

I don't understand why these two AC teams, BMO and Alinghy, are trying to "Train up" their mono teams to sail Cats and Tri's. Why not just go out and hire the best Cat and Tri racers today, and use them? The learning curve is too steep to climb if they are going to be racing the AC on big cats or tri's this October. I'd love to see the look on Larry Ellison's face if he was driving and did something like in that picture above! "Umm, Larry...ease the main..."

****-up or joke to be had in sailing, it seems to be at multihulls expense.

All the more reason not to train up their mono teams. Just let them continue to train and race the leaners while they hire a race proven multihull team, ready to go, no disruption to the leaner programs at all. Why try to do both with the same people, it's not like -lack of money- is an issue. Bertarelli already has a multihull background and team ready to race too. I'm surprised he wants more time to "train".

Fair point, perhaps I am being too cynical and they all really love multihulls after all.

Now I am being sarcastic - sorry

Paul

I'd suggest two thoughts.
1 - These sailors work well as a team and regardless of boat they are going to be tactically strong.

2 - They're not going to give up their ticket to the big dance just because they have to wear a different pair of shoes...

Here's what I hope happens. These guys all get addicted to the speed, just like we all did, and they decide to continue using big cats or tri's for the AC forever! It would be very hard to go back to the expense and slow speed of one of those big Mono's after racing around on a ORMA 60 I would think! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> Maybe we will finally see a revolution in mainstream yachting line of thinking. It's already happening in the charter boat world.

Geant also has an inverted T rudder in the mainhull.

When the ORMA 60 start "Bruce foiling" then the T-foil on the rudders is not there to prevent a capsize but to prevent the bruce foil from stalling and dropping the boat back into the water. That is a wholly different function.

What they have now is an unstable system. Look at it this way.

ORMA 60 goes over 30 knots and at some point the bruce foil develops sufficient force to lift the leeward bow c.q. hull higher in the water. The angle of attack of the bruce foil now also increases resulting in even more bruce foil lift which lift the bow even higher and again increases angle of attack which ... etc

This cycle will continue till the bruce foil reaches such a high angle of attack that is stalls, losing a very large portion of its lift which drops down the bow c.q. hull which reduces angle of attack to such a point that the whole proces starts all over again. You can actually see this happening in the video. They can't really keep the boat to "level flight".

The only way to stabilize this is by using a second set of foils on the sterns, these can be bruce foils also by T-foil are strong prefered because then the system will finds its own stable working point without having the crew actively trim the T-foil. Actually Hydropthere uses this exact same principle and it is perfectly stabilized in flight.

Also in my opinion the Gitana 60 T-foil doesn't look large enough for the job.

At of course at some point everything ends, see here a F16 with T-foils that pushed it too hard :




It ended with the skipper flipping the boat.

Wouter