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-   -   What makes a board carry bigger sails? (http://www.star-board-windsurfing.com/forum/showthread.php?t=2676)

Andy1234 11th September 2007 02:59 PM

What makes a board carry bigger sails?
 
Hi

What exactly makes a board carry bigger sails?

Example: same volume, but a hugh difference in recommended max. sail size:
- Kombat: 96L, 237cm, 62cm -> max. sail 6.5
- iSonic: 96L, 244cm, 59cm -> max. sail 7.8

Ok, what's obvious: Kombat has only US Box and is therefore limited regarding fin size. But if the Kombat had a Powerbox, what attributes are deciding the max. sail size? (Of course: the Kombat wouldn't be a freestyle-wave board anymore with 7.8 ...)

Andy

Egor 11th September 2007 05:30 PM

Lots of variables involved, fin size, rail, rocker, tail width or one foot off. The board might work with 5.2 to 7.8 but the optimal range would be more like 6 to 7m

geo 11th September 2007 06:41 PM

Pretty obvious to me. Roughly I see the following. Not valid 100% in absolute terms, but true if one considers the kit actually used and its development.
Bigger sails are deeper, so develope greater side pull that needs more fin lift to be compensated, so need a bigger fin. To carry a bigger fin with more lift, you need a wider tail in order to have enough leverage to keep the board flat. This is the main thing.
Of course, along with wider tail, other design features come along. Larger volume will keep you afloat with your heavier rig; thicker rails will not bury so easily when pumping a big sail... and so on.
As for rockerline, I see that Carbon Art reveals their rocker pattern (and more rocker patterns are measured i. e. by the Planche Mag test team) and I see it's the same (exactly for some ranges, roughly for others; slalom range is actually divided in two, with small differences) throughout the ranges; so I guess it's not that important relatively to max sail size (in other words: CA SL 52, suggested sails 4.5 to 6.5, and CA SL 62, suggested sails 6.0 to 8.0, share the same rockerline). I guess that intended use range is more important and I guess i. e. different iSonic models have different rockerlines depending on focous on speed sailing, high wind slalom, light wind slalom or early planing.

Unregistered 11th September 2007 11:52 PM

i found i could easily have a 6.5 on a board with a said max of 5.7, whats with that?

geo 12th September 2007 01:02 AM

Oh well I forgot the first example. The Kombat has a tail just about 1 cm. narrower than the iSonic, which of course does not explain all that difference in suggested sail size. But the two boards are totally different in intended use, and the sails used on them should be different as well. My reasoning applies better (if at all!) to boards with the same intended use.

Per 14th September 2007 01:38 AM

Well as I see it the sail type makes a difference too. The iSonic is supposed to use a full on slalom sail. Normally hard core race sails do not have so much bottom end grunt (fullness and sideways forces) as their size may indicate, compared to more "free" sails. The centre of effort (the place where the power is generated from) is very low and very much forward and all that extra canvas up there is hanging loose most of the time mostly ventilating the sail at high speed in powered conditions.
If you put a 7.8 freestyle sail with five battens and a high centre of effort (great for manouvres, early planing and slashing around) and a tight leech I don't think you will find any pleasure in using this size on the iSonic.


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