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Viper lifting foils #244926
02/29/12 02:50 AM
02/29/12 02:50 AM
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taipanfc Offline OP
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http://catsailingnews.blogspot.com.au/2012/02/ac45s-ahpc-airborne-lfoils.html

Interesting. Allowed in the rules or not?

Still not lifting the boat out like a moth. But they say 25 knots in 20 knots of breeze. But are they sustaining those types of speeds for long periods of time or just spikes?

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Re: Viper lifting foils [Re: taipanfc] #244928
02/29/12 03:21 AM
02/29/12 03:21 AM
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Brisveagas
Aido Offline
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My standard Viper gets 10 sec averages over 20 kts so maybe it can.

I heard a rumour that these things will fit the old boats as well. You dont need to lift outof the water like a moth when you have as much power as an F16.

I wonder if there will be any more surprises before the trials.


Aido
Viper 288
Re: Viper lifting foils [Re: Aido] #244930
02/29/12 03:38 AM
02/29/12 03:38 AM
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waynemarlow Offline
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And the next big new thing will be T foils on rudders to maintain the front foils AOA, making the boat feel like an 18fter.

Re: Viper lifting foils [Re: taipanfc] #244931
02/29/12 03:42 AM
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taipanfc Offline OP
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Followed by variable AOA on the front so it doesn't hobby horse downwind. Can't imagine hobby horsing downwind is fast, but looks good for about 20secs.

Re: Viper lifting foils [Re: taipanfc] #244932
02/29/12 06:45 AM
02/29/12 06:45 AM
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Tony_F18 Offline
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I imagine a standard curved foil will stay in place just fine but what about these?
Are they locked or lashed in place somehow?

Re: Viper lifting foils [Re: taipanfc] #244936
02/29/12 08:55 AM
02/29/12 08:55 AM
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Nick F16 Offline
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F16 Rule 1.6.4 says its prohibited...

Re: Viper lifting foils [Re: Nick F16] #244939
02/29/12 09:13 AM
02/29/12 09:13 AM
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Maryland
Kris Hathaway Offline
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It's not the shoal draft option? grin


Kris Hathaway
Re: Viper lifting foils [Re: taipanfc] #244940
02/29/12 09:17 AM
02/29/12 09:17 AM
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Sebring, Florida.
Timbo Offline
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OK...so how did they get the L boards down into the hulls? Can they be slid up from underneath?

Hobie figured out how to 'foil' a long time ago, yet it never really caught on as a racing class.

Can any of you older guys who were active 'back in the day' of the Hobie Tri Foiler shed some light on some of the issues? I remember seeing a fleet of them, once, at the Wildcat regatta, but they looked like a real pita to put in the water, and weeds on the foils were always a problem.

http://www.youtube.com/watch?v=zXSgZCDVWOM

Stick with it, at about 2:37 it shows some of the design concept and the L foils, and how the ski at the front adjusts the up/down lift. It also shows Russel Long going 43 knots in his "Long Shot" during a speed run in France, in the ditch and a two up regular version going 35knots at the end. But I notice all the video speed shots are done with good wind...on FLAT WATER. Great for a lake.

I'd love to have one here on my lake, but I'm not convinced a 'lifting' foil, if C boards or L boards, is going to be fast on lumpy water, in the kind of racing we do in the ocean or lage bay. All that porpoising up and down can't be fast. You may get a small burst of speed when you come up, but when you nose dive back down, it could get ugly. They'd have to come up with a device to controld the AOA to yeild a steady ride over rough seas.

Anyone know where Gregg Ketterman is today? I wonder what he's up to, design wise.


Blade F16
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Re: Viper lifting foils [Re: taipanfc] #244942
02/29/12 09:35 AM
02/29/12 09:35 AM
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Memphis, TN
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mikeborden Offline
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I'm sure you will see these at the Olympic trials.

Timbo,
Thats probably want they did, guessing here, but that isn't allowed in the F16 rules either. You have to be able to lift the board up out of the well. Again, F16 rule.

Mike



Viper USA 132

1984 Hobie 18
Re: Viper lifting foils [Re: taipanfc] #244943
02/29/12 09:46 AM
02/29/12 09:46 AM
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Daytona Beach Florida
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orphan Offline
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Would a board with a hinged tip be illegal? If you made the tip asymetric with a hing it could be pulled up the well and the shape would push the tip to the correct possition when under speed.

Re: Viper lifting foils [Re: orphan] #244949
02/29/12 12:21 PM
02/29/12 12:21 PM
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Palm Harbor, FL
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Originally Posted by orphan
Would a board with a hinged tip be illegal?

Yes, that is illegal. According to F16 rules: "End fences/horizontal appendages below the waterline will not be allowed."


Daniel T.
Taipan F16 - USA 213
Re: Viper lifting foils [Re: taipanfc] #244954
02/29/12 01:09 PM
02/29/12 01:09 PM
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West coast of Norway
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In my opinion not allowed under current F16 rules:

Quote
Definitions
7.13 Daggerboards and Centerboards

All lift producing elements that have as the pre-dominant purpose to resist sideways movement of the craft while sailing and that aren't canted at a greater angle than 6 degrees of the vertical when the boat is level on the waterline.

A centerboard is only different from a daggerboard in the sense that it is folded or rotated away rather than slid away when in danger of hitting submerged objects.


Quote
Rules:
1.6 Daggerboards and rudders

1.6.1 The platform shall be equipped with a pair of rudders.
1.6.2 In addition to the rudders, the platform may also be equipped with a pair of daggerboards or centerboards.
1.6.3 All performance calculations, such as handicap ratings, shall be performed as if a platform has daggerboards or centerboards, even though a particular design may have neither of them.

1.6.4 (Added by vote, August 2007) For the avoidance of doubt, daggerboards/centerboards will conform to the following :
a) Curved/’Banana’ boards will not be allowed.
b) Assymetrical cross-section profile boards will be allowed.
c) Fore/aft movement of the boards when in the down position will not be allowed.
d) End fences/horizontal appendages below the waterline will not be allowed. The board shall be capable of removal, without tools, via the upper opening of the case.
e) There will be no limitation on the daggerboard/centerboard length



I dont see any interpretation that will allow for this on daggerboards. On rudders I read this in such a way that fences are allowed (like used on the Stealth).

Will be interesting to see if they send a boat with these daggers to the olympic trials. I dont know about any substantial two boat testing with this technology where the results are public.

Re: Viper lifting foils [Re: Rolf_Nilsen] #244981
02/29/12 07:50 PM
02/29/12 07:50 PM
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Brisveagas
Aido Offline
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I think it's safe to say that the f16 rules weren't a consideration when coming up with this new development. The Olympic trials are the aim.

As for the foils I had a conversation with Greg about curved foils and the like. He said that someone has done some serious work for them on this topic, and the conclusion was curved foils are quite draggy, and that straight assymetric boards is where the effort should be directed.

Oracle are also testing the same thing. I think we can draw our own conclusions from this.

Re: Viper lifting foils [Re: taipanfc] #244982
02/29/12 07:59 PM
02/29/12 07:59 PM
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Sebring, Florida.
Timbo Offline
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WHAT IF....

Put the dagger slot in the hull at a 45 degree angle, so you'd have a long, straight dagger board, but on a 45 degree angle, which would provide some amount of lift, perhaps even more than a C board...yes? And you'd be within the rules, yes?

Has that been tried yet?


Blade F16
#777
Re: Viper lifting foils [Re: taipanfc] #244984
02/29/12 08:15 PM
02/29/12 08:15 PM
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Northfield Mn
Karl_Brogger Offline
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seven degrees max angle on boards


I'm boatless.
Re: Viper lifting foils [Re: taipanfc] #244988
02/29/12 09:52 PM
02/29/12 09:52 PM
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Sebring, Florida.
Timbo Offline
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Ahh...well, we could change the rules. I think I'd rather have straight boards at a 45, than have to deal with C, or L boards, and I think that would provide more lift too.


Blade F16
#777
Re: Viper lifting foils [Re: Timbo] #245017
03/01/12 12:45 PM
03/01/12 12:45 PM
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Naples, FL
waterbug_wpb Offline
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except if you pull the board out and clip the boat next to you...


Jay

Re: Viper lifting foils [Re: Timbo] #245018
03/01/12 12:59 PM
03/01/12 12:59 PM
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Lincoln, Nebraska
FRENZIED Offline
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Originally Posted by Timbo
I think I'd rather have straight boards at a 45, than have to deal with C, or L boards, and I think that would provide more lift too.
Agreed. Whatever the angle, I can't imagine that moving curved boards back and forth is as easy as straight boards (not to mention the obstruction when they are up).

I'm very curious to see how well the AC crew handles curved dagger boards on the AC72s.

Last edited by FRENZIED; 03/01/12 01:00 PM.

LANDLOCKED
Re: Viper lifting foils [Re: FRENZIED] #245019
03/01/12 01:11 PM
03/01/12 01:11 PM
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FL
sail7seas Offline
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I wonder if a removable T(orY) foil extending off the dolphin striker would provided enough lift or practical/doable?

Re: Viper lifting foils [Re: sail7seas] #245036
03/01/12 04:30 PM
03/01/12 04:30 PM
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North-West Europe
Wouter Offline
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That would be absolutely doable and thanks for that idea. I might steal it from you.


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
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