GC 32 super cat

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The point is how well they work together via the "transition radius".

 

They're not working together, but against each other, hence if there is any significant lift from the upper section, and hence drag, there will be performance gains by eliminating this (e.g. by tuning the foil position so that the upper section is not immersed at max speed). I would be very surprised if they did not already do this, but in the video there is so much spray that it is not easy to see the location of the transition.

 

Here are some images of the later foil version of VSR2 - when she set the new record, this after the earlier radical cutting down to a 300mm stub of the earlier cavitating foil.
Apologies for swerving off from the original thread topic

 

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They most assuredly do "work together" as part of the same system with the transition radius being altitude control.

 

Don't believe so, Doug, why have two foil sections fighting each other? Makes zero sense. Anyway the upper lifting section has to be mostly in air/spray at high speed. Maybe at low? speed 25 knots something is occurring there to equalize differing forces. Still seems Michael Mouse to me. But what do I know.

 

Gary, read Pauls comment again. They're not "fighting" each other-they're working together as part of an altitude control system:

 

THE double edged foil?
That top section doesn't look as if it is doing anything more than small air flatuations/potatoes to me when at speed?
Whereas the submersed cavitating hook?

 

I followed the VSR1/VSR2 efforts closely. I am also prone to noticing how less than careful wording can be misleading and/or can be twisted by people with an agenda.

The VSR2 foil was very much designed to self regulate height at the water surface.

Paul had an "unfortunate flying lesson" with VSR1. His team was not going to take any chances on a repeat.

Many of the "VSR2 improvements" were good examples of making physics work for them instead of trying to fight or actively regulate large forces. They had a very clever and talented crew. The focus on understanding and using this approach to the physics of their boat was clear.

The net total main foil vertical force had to be a very large force down given the high overall rig forces, the required RM and the light boat weight. The angle of the lower portion however was set to produce a force vector just barely off center in cancelling the net force vector from the rig. As such it only took a small amount (percentage wise) of up force from the upper portion to keep things in balance. Given the surface conditions, the upper portion was probably just clipping wave tops to generate the required balance.

The primary force lifting the boat out of the water was the "up force" from the rig net vector force (including the outboard wing extension). The boat was definitely a "hybrid" boat in that the weight was supported by more than one method. If my estimate of the overall loading is even close to correct, and if I were picky with my wording, I would say that this was more of a "flying" boat than a "foiling" or "planing" boat given that much more than 50% of the boat weight was lifted by the rig with a much smaller amount of lift from the forward planing surface. As a matter of fact, the up force from the rig was probably a lot more than 200% of boat weight. The "foiling" vertical forces were all about RM balance and height regulation, not lifting the boat.

The small performance penalty due to extra drag from the foil generating both up and down forces was a "no brainer". They knew that if and when they solved their foil cavitation/ventilation problems, they had good margins. I am sure they had overall speed predictions with sensitivity cases to confirm that having the foil generate some up force along with the required down force was not going to cause problems.

The fact that the boat was "naturally safe" instead of "on the edge" let them focus on their big challenge - getting past the cavitation/ventilation "wall" that had plagued all outright record attempt boats since the Trifoiler.

Although the "foiling" aspect of ride height control at the location of the large force balance (rig vs foil) was a key element to their approach, in context of boat type, it was really a "hybrid flying / planing / foiling" boat. Certainly not just a typical "full foiling" boat where the vast majority of boat weight is supported by foils.

 

PFlados, no one is claiming that this boat is a conventional foiler ... but most would say it is still a foiler.
If you're talking about negative attack foils; they have been around for some time on a small number of designs. Same too, with inclining rigs, although these are a rarer animal.
In transition from dragging to flying, the two edged bent foil (lift and negative lift) one shape is definitely fighting the other ... until the boat is flying ... then that up lift section is doing next to sweet FA.
But there is no doubt it is important in transitional stages when the platform is increasing or decreasing speeds.
But maybe they should try a "conventional uptip" cavitation design to keep the boat in equilibrium? Eh Doug?

 

Gary, I think they pretty much got it right when they set the record......

 

The Alinghi team have nudged up the GC32 top speed record again now set to 39.21 knots.

http://www.catsailingnews.com/2015/05/gc32-alinghi-reaches-3921knots.html

 

From the Alinghi site:

Alinghi have broken the GC32 speed record! Last week, in a training session on Lake Geneva, the team clocked 39.21 knots, well over a whole knot faster than the previous record that was set on Lake Garda in July 2014. Perhaps even more impressive, the top speed is a full five knots faster than the team’s previous personal best of 34.2 knots, set only earlier this year. With such a rapid trajectory, the elusive 40 knot barrier is in sight. Onwards and, indeed, upwards!

 

GC32 super cat

Team Spindrift GC32 foiling from www.catsailingnews.com :
https://www.youtube.com/watch?t=12&v=BxJVlxonNG8

 

The first event of the new season the Austria Cup at Lake Traunsee is kicking off today.

http://www.gc32racing.com/heading-for-the-starting-grid/

 

Day3 of racing at Lake Traunsee in Austria and live feed kicking off now.

http://www.gc32racing.com/