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Old 6th March 2008, 04:23 AM   #1
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Default Hydrofoil Serenity

No, I haven't made one but after watching this kayak

http://fr.youtube.com/watch?v=U95UReP4mdo

it occurred to me that a hydrofoil should be a lot more useful for the Serenity displacement hull than the planning hydrofoil boards. Looks simpler than the Moths, could be fun.
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Old 6th March 2008, 04:44 AM   #2
Jean-Marc
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Tacking, jibing or turning that thing would be a nightmare with 2 hydrofoils 15 foot apart...

Cheers !

JM
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Old 7th March 2008, 02:54 AM   #3
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Yeah, I guess. Unless rolling it would lean into the turn like a plane.
The hydrodynamics of that is beyond me, but intuitively it feels like it should.
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Old 7th March 2008, 05:20 AM   #4
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I'm unsure whether banking the Serenity to windward or leeward will make her turn while she's on 2 hydrofoils. With a 2 hydrofoils system, you'll need a rudder to turn. Check out some jibing or tacking of flying Moth/hydrofoils or Bladerider movies on YouTube, this is very clear the rudder is doing all the turning job, not the banking of the boat.

With 1 hydrofoil, this is a different story. Lean on the inside curve to initiate a turn (foilboarding la Rush Randle, air chair, etc...).

Speedwise, I'm not sure a hydrofoiled Serenity would be faster because once she's rised above and out of the water, the hull lenght doesn't matter anymore. I can go as fast as twice the wind speed in the 3-7 knots wind range. Same numbers with a flying Bladerider : twice the wind speed. So I'm a bit skeptical as to foresee the benefits of hydrofoils under a Serenity.

Maybe Tiesda or Jim can tell us what they think about that ?

Cheers !

JM

Last edited by Jean-Marc; 7th March 2008 at 05:35 AM.
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Old 7th March 2008, 06:35 PM   #5
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I guess it does not work at all in a smallest chop.
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Old 8th March 2008, 06:51 PM   #6
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Another vid showing how it works. I'm not sure what he's saying, but the inventor seems to be a guy named Einar Rasmussen. Spose he's a long lost cousin?


http://fr.youtube.com/watch?v=uO54Zv...eature=related
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Old 10th March 2008, 01:02 AM   #7
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The C cat championship last year did pretty much prove that if your hull is efficent enough then hydorfoils aren't an advantage. But those hulls are twice the length of Serenity, which looks much more like the kayak to me,.And the vid there looks pretty convinving on the face of it.
But I've gotta concede wands and rudders would be a step to far.
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Old 12th March 2008, 02:11 AM   #8
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I agree narrow hull length is an important factor to sail fast in light wind, but it's not the only one. Sail area to weight ratio is very important as well in very light winds IMHO. This is what I've done last summer against various classes of catamaran with a Serenity + 70 cm fin + Code Red 11.0 m2 sail on ultra flat fresh water lake:

Class A cat (5.50 m lenght, 13.9 m2 main sail, 75 kg weight, one man crew) : I'm faster on all point of sail in 1-7 knots of wind. Above than that, the cat can still accelerate while the Serenity speed is topping up at around 12 knots.

Class B cat :

i) Hobbie 18 (5.50 m lenght, 22 m2 sail, 180 kg weight, 2 men crew, wing seat). I'm faster on all point of sail in 1-7 knots wind. Above than that, the Hobbie is faster while the Serenity is topping up at 12 knots Vmax.
ii) Hobbie 18 Tiger (5.50 m lenght, 21 m2 main sail, 180 kg weight, 2 men crew, wing seat). I'm faster on all point of sail. However, when the Tiger hoists her 21 m2 spinnaker, she's faster reaching & downwind.
iii) Ventilo 18' (5.50 m lenght, 20 m2 main sail, 130 kg, 1 man crew). We both are more or less on par. However, when the Ventilo hoists her 20 m2 spinnaker (2 men crew), she's faster reaching & downwind.

Class C : no drag race yet

Class 28' Ventilo M2 (8.53 m lenght, main sail 49 m2, jib 20 m2, genaker 72 m2, 375 kg weight, wing seat, 3 men crew). With only the main sail, I can barely follow her in winds around 5 knots. When she hoists the jib or genaker, I'm lost behind.

Class 35' Decision D35 (10.81 m lenght, main sail 80 m2, jib 44 m2, genoa 77 m2, reacher 128 m2, 1'250 kg weight, 5 men crew): I'm lost far behind, no questions. Being overpowered in 7/8 knots wind on a deep reach/downwind, the D35 is flying at 18-20 knots Vmax (2 x wind speed upwind and almost 3x wind speed downwind; *) , so clearly no match for any sailing boats including the Serenity in Beaufort 1-2 winds...!


So, I doubt a hydrofoiled Serenity could be faster than those large cats...

Cheers !

JM

(*) : http://mytrims.com/mytrims/trim4.asp?trimID=20273

Last edited by Jean-Marc; 12th March 2008 at 02:24 AM.
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Old 15th March 2008, 06:39 AM   #9
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Well you have been sailing against the big boys.
A less experimental way of getting more speed would be a tandem Serenity, since the tandem Div 3 were faster than the solo Div2. In fact as Serenity isn't designed to plane the advantage might be greater. Maybe there is enough volume if the mast foot could be arranged ? And a dedicated light wind long board sail like the Aerotech Dagger or Demon VG5 might give you an edge when trying to embarrass those rich boys :-)
But seriously it's fascinating to think what is th fastest way round a short course singlehanded in the various winds.
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Old 15th March 2008, 10:16 AM   #10
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Hi JM,

Regretfully, I seemed to have missed your post above, but your candor is appreciated. While a Serenity sailor may not always be the most competitive race design in the mix, I'm awfully stoked about getting my Serenity very soon.

Although I'm not a formally competitive character in my efforts, I do enjoy the speed and efficiency associated with windsurfing (in higher winds its very obvious and friendly to the individual sailor). I really itch to take advantage of the low wind design from a simple fun and experimental viewpoint. Overall, it must be remembered that formal racing is very controlled and schedule focused, so I can be having fun irrespective of yacht club restrictions almost any time of the day. Nothing against formal racing scene, it just opens doors to individual enjoyment and fulfilment. I think that the individual aspect associated with windsurfing is at the core of the sport. Really, for those of us who want "no rules" time spent, it's a heaven of sorts.
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