Monday, August 26, 2013

Speedsurfing Tuning Tips 2

by Pierre Milutin

Previous article in the same series: Speedsurfing Tuning Tips 1

5. Profile

Once you have rigged your sail, flip it over to the otherside. Do not press the cams or the battens to flip it around. The profile of your sail is how it looks, mainly on the the luff pocket, from the bottom batten to the 3rd batten, which is above the boom.

So, you have to look at the luff pocket and those 3 cams. How much are they pushing out? For example, a flat profile is when the luff pocket has very little shape, meaning the cams are pretty flat on the mast. A deep profile is when the cams are giving a lot of
shape, pushing outwards away from the mast.

The best profile to get is when the cams are roughly 45 degrees out from the mast. Note: this is only the bottom 3 cams, not the 4th!

This will give you good shape of the sail and nice belly. You dont want too much of a belly, that becomes too powerfull and creates alot of drag.

So when you put your spacers in, put only one spacer on each cam and then rig up. Mind you – and this is very important! - when putting in spacers always loosen the batten tension first completely, so the sail gets wrinkely and then start rigging the sail with the new spacers. Once rigged, tighten the batten tension so that the wrinkles are just gone. Do not over tighten - something might break!

The way to check if the profile is good: you have to stand at the tip of the sail, lift the tip and look down along the luff pocket and see how much are the cams are goin out.

Another important factor is, if the cams are still not goin out how you want them to go, then you have a stiff batten in the sail! The stiff part is the 2nd part that is connected towards the cam. The battens usualy have 3 stage. The back part is the thickest, then comes the 2nd part which is thinner and this fits into the thicker one. Then comes the fiberglass rod which fits into the cam. So, you need to make the 2nd part of the batten longer. The length is the width of you luff pocket where the battern sits, so each 3 battens will have a different length in the luff pocket area. The batten that you will shorten is the thick battern, the back one.

6. Draft

Once your sail is rigged, you will go to the tip of the mast. Lift it to eye level - you can be on your knees for this - and look at your draft. Where it is sitting? You will find your draft on the crossbattern - the 2nd batten from the bottom which crosses your boom.

When you look at this batten shape, there will be a minor half circle goin from the edge of the luff pocket to the clew of your sail. The middle of this half circle is where your draft sits!

For example, if the middle of this minor half circle is in the middle of the sail along the crossbattern, than you draft is sitting in the middle of the sail. This is bad, bacause every time a gust hits, the power will be in the middle of the sail. That will couse alot of backhand pressure. In this situation, you can adjust as much you want your harness lines, but it will still not work good.

The best place for the draft to be is very close to the luff pocket keeping the pressure forward and of. When the draft sits forward then the sail pulls forward not sideways, so you have a constant pressure of the sail pulling forward, and no backhand pressure. Connected to this: the first notch on the harness lines should always sit parallel of the back stitching of the luff pocket exactly where the draft sits.

If your draft is way back then your harness lines will sit back, and you will not have forward pressure!

Adjust your harness lines: get on the water, start sailing and slowly let go of the boom but not completely. See where the sail is pulling. If its pulling forward move the line forward but only on small increment (or, if the sail pulls backwards, move them back) You will be surprised that only 5 mm can make the differnce.

Next article from the same series: Speedsurfing Tuning Tips 3

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