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Gear of the Future
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pzwinakis



Joined: 03 Aug 2000
Posts: 42
Location: Santa Cruz

PostPosted: Sat May 04, 2013 7:51 am    Post subject: Reply with quote

xander.arch: "Pzwinakis, Give us a break man. The original post here asked us to dream a bit - to think outside the box. Let's not turn this into a kite vs windsurf post."

Ok fine.. I meant no disrespect. But if it was a Kiteboard vs. Windsurfing post, my tone would have been quite different..

Good luck with your dreaming..


Last edited by pzwinakis on Sat May 04, 2013 2:23 pm; edited 1 time in total
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Georges



Joined: 10 Apr 2000
Posts: 249

PostPosted: Sat May 04, 2013 11:25 am    Post subject: Reply with quote

Cup holders would be nice. Cool
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mac



Joined: 07 Mar 1999
Posts: 4999

PostPosted: Sat May 04, 2013 11:48 am    Post subject: Reply with quote

So AHD now has a single foil windsurfer, but I can't find much out about how it performs. Rich Miller spent more than a decade in the Bay area trying to build an effective foiling windsurfer, http://www.foils.org/miller.htm, and had a number of top riders try it out. They found it hard to control, perhaps because it had 2 foils and was very complicated to steer.

It is absolutely true that speed is not the only, or most important metric to judge success. Control, range, ease of turning, ability to surf and so forth are all good metrics--just be specific, because all design involves compromises.

So has anyone seen or tested the AHD design?
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windward1



Joined: 18 Jun 2000
Posts: 652

PostPosted: Sat May 04, 2013 3:06 pm    Post subject: Windsurfing Hydfofoil Reply with quote

Hi mac,

Take a look at this:

http://www.youtube.com/watch?v=1oyWMusaDTI

I saw this single-foiled windsurfer being played with at Kanaha in , I think, 2005. The guy who had it (maybe the inventor?) was letting people he knew borrow it and try it out. It seemed easy to control with little or no learning curve.

The AHD one looks very similar. Maybe he sold the design to them or they independently came up with a similar one.

However, note that near the end of the video, a regular windsurfer is catching up and passing the foiled one. Why have the complications of a foil if it is not any faster?

Windward1
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mac



Joined: 07 Mar 1999
Posts: 4999

PostPosted: Sat May 04, 2013 3:27 pm    Post subject: Reply with quote

Thanks windward, I had forgotten that I had seen that one once. One of our locals used to sail moths, which were very fast but twitchy on their foils.

I think the design question for speed with foils is the drag equation. Most of the single foils that I have seen have a fairly large foil in the horizontal plane to counterbalance the weight of the sailor and rig. That gives form drag and flat plane drag, no matter how finely you shape the foil. I think, but I haven't tried to make the calculations, that this ends up with more drag than a formula board with a 60 cm or so fin, or a slalom board with a 34 or so cm foil. If you watch those boards at full speed, the fin is acting very close to a foil, bringing the board largely out of the water, so there is relatively little flat plane drag from the bottom of the board. Upwind, of course, the whole fin is in and the rail is also used to get better angle. I also noticed that the sail trim is less efficient in the video. Over a race course, it isn't top speed that always wins, but how much of the time you spend close to top speed. More difficulty in transitions outweighs differences in top speed.

However, I would guess that foils have a potential advantage in higher winds when the surface state of the water is the controlling factor on top speed. Unimportant for tricks, very important for speed. But I haven't seen the problem solved yet.

The foils on the AC 72's are pretty big, but they have ample power and weight to overcome the drag and balance the forces. The interesting question will come with transitions, and trying to stay up on the foil and maintain control. It should be fun to watch.
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windward1



Joined: 18 Jun 2000
Posts: 652

PostPosted: Sat May 04, 2013 3:49 pm    Post subject: Speed Reply with quote

Hi mac,

I believe your drag analysis to be correct. Given a minimum of chop, a planning hull with minimum surface contact and a fin can end up with less drag than that of a hydrofoil.

I remember my Dad telling me how fast mono-hull scows were in the Midwest. They had a lot of sail and could readily plane on the surface on the lakes on which they sailed and could rival or beat catamaran speeds.

The Moths are amazing and I am amazed at how well some of the sailors can jibe those critters given what appears to be inherent instability during the transition.

The Hydrosptere (sp?) I believe has approached the ultimate of sailing with hydrofoils and seems more 'seaworthy' than the AC 72s. The winged sails are so specialized, I cannot see them evolving into something that the everyday sailor could use. There is something to be said for rolling up you sail when your session is over.

Windward1
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mac



Joined: 07 Mar 1999
Posts: 4999

PostPosted: Sat May 04, 2013 4:05 pm    Post subject: Reply with quote

Laughing
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dvCali



Joined: 23 Aug 2007
Posts: 419

PostPosted: Sat May 04, 2013 5:06 pm    Post subject: Reply with quote

pzwinakis wrote:
Consider that I kite in the bay area, mostly in the surf. I sail anytime the conditions are good and all I need it two kites and one board. This gets me on the water in about 15 knots or so (light enough that there are absolutely no windsurfers in the water) and I can comfortably kite in up to about 30+ knots.. I talked to one of my Windsurfing friends at the beach and he was telling me about the increased wind range of the new Windsurfing gear, yet he still had 4 sails and two boards! And I can be on the water more than he can with my limited gear.

I agree that efficiency could be improved, but the situation is not as bad as you depict it. If you really are sailing 15 to 25 (let's call it 25, 30 is very rare in the BA) all you need is 1 windsurfer and 2/3 sails.

Actually, with 2 windsurf boards and 3 sails you can cover easily a huge range that a single kite cannot obtain. At my weight (160) a slalom-ish board of 105 liters with a 6.6-7.0 and a 85L Freewave with a 5.2 and 4.4 would take me out in almost any condition including sub-10 knots of wind in displacement.

Having said that ... I like my idea of the interchangeable rails. Build a board that can change shape according to conditions and windsurfers would have to bring just one board with them to cover 5 to 25.
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noshuzbluz



Joined: 18 May 2000
Posts: 771

PostPosted: Sat May 04, 2013 6:01 pm    Post subject: Reply with quote

Quote:
I like my idea of the interchangeable rails. Build a board that can change shape according to conditions and windsurfers would have to bring just one board with them to cover 5 to 25.

Or change rocker line. Maybe something equivalent to adjusting a truss rod on a guitar neck.

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dvCali



Joined: 23 Aug 2007
Posts: 419

PostPosted: Sun May 05, 2013 12:19 pm    Post subject: Reply with quote

noshuzbluz wrote:
Quote:
I like my idea of the interchangeable rails. Build a board that can change shape according to conditions and windsurfers would have to bring just one board with them to cover 5 to 25.

Or change rocker line. Maybe something equivalent to adjusting a truss rod on a guitar neck.

Possibly both. A single board 85L 225 x 58 that can add 20L to make into a 105L with a set of detachable rails and maybe change rocker using an external tension device (Witchcraft is working on a flex tail http://www.witchcraft.nu/) would do a lot. And if such a board was targeted as a mutant Freerace to Freewave it might have a market. Trick would be to make it light. But that would only apply to the 105 and the extra weight at 105L might not be such an important issue.

Mistral, by the way, tried to do something similar with a interchangeable tail I think 15 years ago. You could actually buy it. But this was when boards were long and norrow, now things are different and the short/wide paradigm might work much better to realize this idea.
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