Good morning,

I would like to know wether a chart with the following axis exist

on one axis, there is the wind speed,

on another axis, there is the sail size/surface,

and, in between, there will be the corresponding weight or tension on the sail (in lbs or kg) due to the wind speed

Has anyone come accross that type of table before? If so, where can I find it?

Mu! There are a many more factors than just wind speed. You will need a multidimensional graph, and even then it will be impossible to correctly account for sail design variances and individual preference. Trial & Error is your friend.

In the meantime, I found this

F = 1/2 * air density * (wind speed) ² * Aerodynamic coefficient * Surface.
If wind speed is 20 m/s and the sail surface is 6.4, then I get
= .5 x 1.293 x (20) ² x 1.1 x 6.4
= 0.5 x 1.293 x 400 x 1.1 x 6.4
= 1820 newton = 185 kg or 407 lbs


not sure about the drag coeficient, you chose 2, I chose 1.1. found conflicting information about what to select.

maaaaaate...just loop it round once and yank it out...any length of outhaul rope will be fine..go to your local shop and get a length....spend more time sailing than worrying about formulas and stuff.....

Yvan, talk to the other guys where you're learning, listen, watch and learn. Also Redsurfbus is on the money re line

cheers firiebob!

Another thing I thought of was dont focus on these forces. The outhaul and tension of a sail is a 'feel' gained from experience.

As a quick guide - if you are placing your boom clamp mid cut out then the sail printed stting will often be correct (not always), placed higher to the top of the cut out, add a couple of cm to the extension on the boom.

If the sail feels twitchy then you have too much outhaul on, but will go upwind very well. If it feels slow to plane and heavy you may have too little outhaul on, this can be shown as the sail will touch the other side of the boom when powered up (this is called negative outhaul and used by speed sailors when bearing off the wind).

The best thing for you to do is set your sail and spend a session adjusting the outhaul from max to mid to min in a constant wind, this will give you an idea of the different feel that the sail gives at different settings.

As for rigging, I race with people who use only 1 line of rope through the clew eyelet and nothing more, as part of adjustable outhaul setup. I prefer a double line through the eyelet. Some booms have a loop and go set up (http://www.k-bay.co.uk/_product_43824/Alloy_Tail_Piece_62cm_-_Standard), rather than pulleys there is a hole that the line comes from, a cleat and a 'rimmed catch' (cant think of what to call it) on the other side of the mid point. All you have to do is put the loop through the clew and over the catch, then tighten by pulling more line through the cleat........takes seconds to rig the outhaul this way.