Saturday, August 24, 2013

Speedsurfing Tuning Tips 1

by Pierre Milutin

These are the most important points to look for on the sail, and what to do…

1. Reccomended mast

First of all, it's best when you buy a race sail, to stick with the recomened mast for it, unless you really know what you are looking for!

2. Downhaul (DH)

Always look whats recomened and work way from there. DH adjustments only work well within 5 to 10mm not more than that, especially when underdownhauling.

Example - your extension is, say, up to 22 cm - which is written on the sail - so if it is light wind, the max you would underdownhaul is down to 10 mm. I would recommend 5 mm – that's all it takes. If you start goin more, you will kill the power in the sail making it heavier in your hands and putting a lot of down force on the board (meaning pushing the nose down to much). As the wind picks up you put it back to recommened.

The problem is, if you under DH your sail, you close the top leach which is your exhaust, and then your sail can't breath, which causes it to be heavier and underpowered. If a gust hits, you dont go faster and it becomes hard to sail. The sail has to feel very light in your hands and well balanced and when a gust hits it has to drive!

When the wind picks up more stronger, you can try to put over DH, let say, 5mm more than what's recommened, but only when totally fully powered to gain controll...

If you over DH too much, say up to 10mm, then your rig will be way flat causing it to be twitchy. The draft of the sail will go back and forth. On the boom you will have front hand pressure then back hand pressure etc., and also the top leach will be way too much open killing way too much power.

3. Outhaul (OH)

Always start of with neutral OH. That should be that the sail is just touching the boom. However, this also depends on the profile of the sail. For example, Neil Pryde have a deep profile, so you dont need negative OH. You just need it to touch the boom but not too much. On the North Sails and Maui Sails, the profile is more flatter so you need to give negative OH to put in the power again. You have to try it on the water and see what gives you the best results!

Dont forget: if you have a sail with a deep profile, you only need to let of the OH very little when doing speed runs. Otherwise, when you let of too much OH, you will kill the power in the sail and also creating too much drag because the sail starts loosing shape.

4. Leach Twist

The best way too find out your correct DH to get the right twist is to look up at the top of the sail while you pull on the DH. Count 3 battens down and in the middle of the 3rd and 4th batten on the monofilm look how far does the crease go in towards the luff pocket.

You want the crease to be roughly around 10 cm from the luff pocket. It is something you have to play with, to find the right settings for the sail to work at its full capacity. Like I wrote, it's only a 5mm increments on the DH!

We have two different kind of twists on the sail: static twist and dynamic twist, which both have to work together.

Static twist is the top leach. You dont want you sail to twist too much. While you have the rig on the ground, you put your foot on the mast base and press down. The top of the sail rises and you look at your twist. If its bagging down alot then you have a mast problem - way too stiff mast. You need the sail to have a nice even twist - like a ice long half circle twist evenly!

Dynamic twist is the bottom half of the sail which is the part above the clew. Normally, on the beach once rigged, the first 2 batterns above the clew, the leach should be a little bit tight. If its way too tight then you have the same problem - way too stiff mast .

How does the dynamic twist work?

When sailing, you have to keep your eye on this to see how it works ! Say you hit a little lull after a gust. The bottom second battens above the clew: the leach should tighten up which gives you consistant power through the lull. If the leach was loose, you will still go through the lull, but slower, because the sail is not giving you the power that you need at the moment.

Next, when a good gust hits, then the leach should open up and you will see from the top of the sail to the bottom clew of the sails that leach will compleley open up, creating a nice even half circle. That means that the sails exhaust is work great and still giving you control and power.

Static and dynamic twist should work together. If one fails, you are automatically of the pace and the sail will feel wrong.


Next article in the same series: Speedsurfing Tuning Tips 2

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