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PostPosted: Thu Dec 15, 2011 11:48 am 
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Joined: Fri Jun 17, 2011 12:26 pm
Posts: 371
Location: Harsens Island, Michigan
Hi All,

I have searched and read a bit online here about the batten tension and also about tapering them, along with the benefits. Unfortunately, it just left me wanting more information. Perhaps this is the 'secret sauce' of racers, and not openly discussed.

As I understand it, by tapering the battens and adjusting the tension, you can shape the sail to be more efficient. I would guess that different wind conditions would require different sail shapes, so if you were to get really technical about it, you could have a different set of tapers, adjusted to different tapers, depending on the wind conditions.

Questions:
1. is it considered 'class legal' to taper them, and do most racers do it?
2. if so, is it class legal to use other materials or non hobie battens in racing?
3. what experiences can be shared about what batten tension to use for moderate wind (say 12-18 knots)?

I should have opened with an appology. I am an engineer, and see many advantages (for racers) to invest a lot of thought into this aspect. That, and it is fun for me!

Thanks in advance,

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Steve
1979 Hobie 16 "Orange Crusher"
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PostPosted: Thu Dec 15, 2011 4:27 pm 
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Joined: Mon Feb 09, 2004 10:08 pm
Posts: 139
Location: Ottawa, Canada
Well now isn't this timely. I was just working on my battens. At best I don't think they change the sail shape that much, that's the job of the sailmaker, but you can make sure they don't fight the sail.

Answers:
1. is it considered 'class legal' to taper them, and do most racers do it?

Yes is is class legal and no most racers don't do it. They used to back in the early days, there's a section in "Welcome to A Fleet" on tapering battens. This forum was polled last year and apparently nobody does it anymore.

2. If so, is it class legal to use other materials or non hobie battens in racing? No. You have to use Hobie supplied parts. There are some quibbles: the Tiger or Wildcat when it's an F18, a Wave under IWCA rules, and the Hobie 21.

3. what experiences can be shared about what batten tension to use for moderate wind (say 12-18 knots)?

Well there's tension and tension. There's the amount of compression needed to knock them out of column. Stock battens are usually around 6 pounds for the bottom batten and close to 25 for the top batten. If I'm tapering battens I like to try and make them all about the same at about 6 pounds or less. Unless you have a flat top sail when that top batten wants to be 12 or 14 pounds.

When you're tying them in to go sailing it's usually recommended that you just barely snug the lines up when it's light and set them as hard as you can pull when it's 25 knots or so. Some boats use heavier (more tension) battens in the top for stronger winds.

Tapering instructions:
http://users.tpg.com.au/kkmiller/hobie/battens.html

The Hobie Tiger main (flat top) has stock batten tensions of 14, 11, 6.6, 4.4, 3, 3, 3 pounds.


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PostPosted: Thu Dec 15, 2011 6:05 pm 
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Joined: Mon Jul 14, 2003 7:11 pm
Posts: 4611
Location: Detroit, MI
The vast majority of racers don't play with their battens too much (we're talking about Hobie 14s / 16s / 17s / 18s here - not F18s). Once they get a good median shape, they leave them alone.

The shape of the sail is largely determined by the cut; the battens can only change it marginally. The two critical measurements are max draft (expressed as a % of the chord) and it's position (also expressed as a % of the chord). Draft determines power (more draft = more power); its position determines the velocity at which max power is obtained before the sail begins to stall.

On a Hobie 16, usually only the top 2 main battens are tapered - and they come that way from the factory. Some people taper the top jib batten to make it more flexible. Otherwise, the top of the jib is very flat.

On the 16's jib, the battens are tensioned to pull the wrinkles out, just a bit more, then left alone. Most people tape the stub end of the batten to keep the line in place and help prevent it catching on the mast / halyards.

Insofar as tension is concerned, for most conditions, you pull the wrinkles out and just enough to make the batten "stand up" - it will hold its shape under its own weight.

For heavy air - over 15 kts consistently - just pull the wrinkles out. You want them tight enough to stay seated in the luff caps during jibes, but no more.

For lumpy water (Lake St. Clair) - crank the battens in, especially the top 3 battens.

There are lots of books out there on sail shape, but don't get too wrapped up in them. On small boats, racing around the cans, one blown tack far outweighs any gains by having the perfect sail shape.

Don't leave tension on the battens for more than a few days. You'll permanently deform the sail.


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PostPosted: Thu Dec 15, 2011 8:24 pm 
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Joined: Fri Jun 17, 2011 12:26 pm
Posts: 371
Location: Harsens Island, Michigan
Thanks guys, for the additional information to ponder and digest.

I hadn't considered how the cut of the sail allows your battens to take shape or resist it. And since everyone has to race stock sails, it makes sense that the actual sailing and tacking would have a greater effect on the outcome.

Thanks again,

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1979 Hobie 16 "Orange Crusher"
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