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tuning 5.6 sail for max power to replace 7.5 in light wind
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ittiandro



Joined: 22 Nov 2009
Posts: 9

PostPosted: Thu Apr 04, 2013 9:32 am    Post subject: tuning 5.6 sail for max power to replace 7.5 in light wind Reply with quote

The ice is melting and the season is coming up. A couple of questions before my first freeze-up.
I am an intermediate sailor, with a Bic 293. As I usually sail in light winds, I normally use large sails (7.5 or 8.5). They are heavy and not very easy to manoeuver in light winds. I was thinking instead, in light winds, to use a smaller 5.6 sail (Sailworks Slalom Race cam sail) but rigged for maximum power, i.e. with the lowest amount of downhaul and the smallest amount of outhaul that will still allow the cambers to rotate. In addition, I was thinking that detensioning of the batten would further facilitate the cam rotation and give even more shape to the sail, thus compensating for the relatively small downhaul and outhaul. The point here is getting the maximum power from a small sail in light winds . What do you think?

Thanks

Ittiandro
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cgoudie1



Joined: 10 Apr 2006
Posts: 1124
Location: Killer Sturgeon Cove

PostPosted: Thu Apr 04, 2013 9:46 am    Post subject: Re: tuning 5.6 sail for max power to replace 7.5 in light wind Reply with quote

I think your detuned sail is going to have a wind range from about
16 to 18MPH, will feel heavier than a 7.5 under power, and will
still be considerably less planable than a 7.5. I detune my big
Northwaves (6.7 and 5.5), often to get max planing out of them,
and trying to get 7.5 power out of a 5.6 is not possible, you
might get 6.5 power out of
a Sailworks Hucker 5.6, if you really tuned it to be on the edge
of it's control range. Plus Northwaves and Sailworks sails were
designed for pretty broad tuning., not typical of a slalom sail
(which is designed more for the range towards the upper end of the wind
spectrum).

.02

-Craig


ittiandro wrote:
The ice is melting and the season is coming up. A couple of questions before my first freeze-up.
I am an intermediate sailor, with a Bic 293. As I usually sail in light winds, I normally use large sails (7.5 or 8.5). They are heavy and not very easy to manoeuver in light winds. I was thinking instead, in light winds, to use a smaller 5.6 sail (Sailworks Slalom Race cam sail) but rigged for maximum power, i.e. with the lowest amount of downhaul and the smallest amount of outhaul that will still allow the cambers to rotate. In addition, I was thinking that detensioning of the batten would further facilitate the cam rotation and give even more shape to the sail, thus compensating for the relatively small downhaul and outhaul. The point here is getting the maximum power from a small sail in light winds . What do you think?

Thanks

Ittiandro
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dennis_c



Joined: 05 May 1998
Posts: 612
Location: Rio

PostPosted: Thu Apr 04, 2013 10:53 am    Post subject: Reply with quote

Make that .04
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cagjr21150



Joined: 04 Apr 2005
Posts: 295

PostPosted: Thu Apr 04, 2013 11:38 am    Post subject: Reply with quote

my 2 cents...I found this on the Intermediate Skills Page of the Learners guide to windsurfing. Guy Cribb talks about getting more power out of your sail by simply raising the boom. It worked wonders for me in my light wind laboratory, here in Florida. I doubt you will get much more performance by your approach. Race sails are meant to be used in the upper limits of their wind range. Go with Cribby's wisdom: tune the sail to the numbers and raise your booms higher than where you normally set them now.
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d0uglass



Joined: 28 May 2004
Posts: 1017
Location: Bonita Springs, Florida

PostPosted: Thu Apr 04, 2013 1:38 pm    Post subject: Reply with quote

There's no substitute for sail size when it comes to power.

You could mess with your 5.6 and make it pull like a 5.8, but nothing you do is going to make it pull like an 8.5.

If you're unhappy with the feel of your larger sails you might try replacing them with different types of larger sails, or upgrading the mast and boom. A lightweight modern camless 7.5 on a 460 skinny mast with a short carbon boom will feel a lot more nimble than a heavy cambered 7.5 on a fat old 490 mast with a long aluminum boom.

A wider board will also make your big sails more manageable.

I have an 8.0 Aerotech freespeed (camless freeride sail) that gives a lot of power but still feels pretty small.

_________________
James' Blog: Windsurfing Equipment Size Calculator
http://jimbodouglass.blogspot.com/2010/11/updated-windsurf-calculator-online.html
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isobars



Joined: 12 Dec 1999
Posts: 13288

PostPosted: Thu Apr 04, 2013 2:01 pm    Post subject: Reply with quote

Define "replace"? Is this an attempt to plane while underpowered by two meters, or is this for days when you've abandoned planing and are just trying to slog as fast as possible without having to manhandle a drive-in movie screen?

Realize, too, that race sails are inherently more cumbersome than non-race sails. They are designed for one purpose: rigging too big and racing to an upwind mark for big bucks. For any other application, their disadvantages are many. First and foremost, For any given size, a race sail has LESS low end (light wind) power than any other kind of sail. You're using a turbocharged four-banger with tall gears to plow a field, and it's going to burn out the clutch.

You're the clutch.

Mike \m/
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adywind



Joined: 08 Jan 2012
Posts: 201

PostPosted: Thu Apr 04, 2013 2:03 pm    Post subject: Reply with quote

How come your big sails feel heavy?! Bic 293 OD with a 8.5 sail is a youth racing class after all. Do you mean they are heavy off the plane when you have to hold them unhooked? If so get yourself long harness lines that will make it easy to hook/unhook when off the plane.
For example I'm using Chinook adjustable HLs set to 30" when comfortably powered and planing with my 9.0 sail. When the wind is below 10 mph/ my planing threshold / I extend them to 32" and even lower my boom from neck high to chest high in the worst cases. This makes the sail flatter as cagjr21150 already mentioned /helps a bit going upwind/ and enables me to use the harness off the plane. This way the 9.0 never feels heavy. I'm 5'7".
Of course the 5.6 will move you back and fort /even the smallest sail will with this board/ but it won't get you planing. And when the wind is strong enough /over 25 mph/ for this sail your board will jump around like a raging bull catapulting you all the time becouse it will be too big and heavy for those conditions.



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Last edited by adywind on Thu Apr 04, 2013 2:58 pm; edited 1 time in total
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gregnw44



Joined: 23 Jul 2008
Posts: 189

PostPosted: Thu Apr 04, 2013 2:56 pm    Post subject: Reply with quote

Lots of good advice here that I also agree with, especially Mike's question to define "replace".
But I agree, the original poster can make the sail have more power, which will help him in nonplaning winds... but tune it back up when it gets windy.

Anyway, I have a slight hi-jack to this topic... but related Smile

cagjr says that Guy Cribb says to raise the boom to get more power.
adywind says that he lowers his boom to get more power.

I've also heard things along these lines for a long time, but have never really understood this practice (so, I just do my own thing which works for me Smile
To me, the sail should have a certain profile to work right. And yes, I know how to adj. downhaul and outhaul and batten tension to get more or less power... AND to move the "center of effort" around... AND to change the sails wind "range".
HOWEVER, why does it make any difference "where" I attach my boom to the mast?!?!?!
Because, if I attach it at the top off the mast sleeve, I'm going to extend it slightly, so I keep the sail profile the same. Or if I'm tall (I am) and for some reason, I want the boom low... then I'll shorten the boom. Again, it's the profile of the sail I care about. And I don't understand why attaching the boom hi or low makes a difference.
Enquiring minds want to know,
Greg Smile

PS - I know there are some sails that have 2 clews a few inches apart, giving you a choice where to attach the outhaul. And I understand the theory of how this might increase/decrease power a bit. Frankly, I don't think I'd ever notice that however... and doubt "most people" would (some would, I'm sure. but many wouldn't).
Anyway, I use those clew options to attempt to attach the boom at 90* to the boom, depending on where I want to clamp it on.
BUT, back to my question... I don't think "the advice given above" has to do with clew attachment locations, because neither poster mentioned it. And also, I used to hear this advice, way before they made sails with 2 clews.
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gregnw44



Joined: 23 Jul 2008
Posts: 189

PostPosted: Thu Apr 04, 2013 3:04 pm    Post subject: Reply with quote

Note - It looks like adywind edited his post, while I was writing. He put in a different pic... and changed what he wrote.

So now my question doesn't make quite as much sense, LOL
Oh well... I'll leave it the same anyway.
Greg Smile
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adywind



Joined: 08 Jan 2012
Posts: 201

PostPosted: Thu Apr 04, 2013 3:04 pm    Post subject: Reply with quote

gregnw44 wrote:
cagjr says that Guy Cribb says to raise the boom to get more power.
adywind says that he lowers his boom .

Corrected ! My fault sorry! Embarassed
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