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Mast rotation take 2


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Read all the threads on mast rotation and everyone has described what to do but I cant find any reference as to why should you rotate your mast...?

At a guess downwind you pull on 90 deg to create more area for directing wind into the sail or is there more to it such as affecting prebend..?

To depower up wind pull it to the winward hull to break off some air flow.?

Is this the best method for depowering your main upwind. Wy not just point higher?

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Rotation is used in conjunction with tear drop/wing shaped mastes to create far more power which is easily adjustable.

A round static mast will have a leading edge down luff which is disturbed and so unused air or power. by rotating a faired mast section the wind 'joins" to the mast and then sail in a fluid and so effecetive action.

I sail a 14sq and think the rotation style is the same as the two boats are both simlilar in design and boomless.

I have found the anti rotation to be the most important to master.

Your inhaul and downhaul are how you will resist rotation on that boat. While you can just let the mast find its own place there is a lot of performance to be gained by understanding where to set the mast.

Spend some good amount of time creating six to eight setting points along the inhaul and use the downhaul for remote fine tuning.

I have also added an RF5 and cheek block with a shock cord to make the action very positive on the inhaul.

Your over rotation device is for downwind sailing so at that time remember to release your inhaul to about 7 8th out and release downhaul and over rotate.

Originally posted by zeflyguy:

16 sq

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Thanks Will but I have visited Kurnell already but I will visit again...

As far as answering my question its needs a little more clarification.. I always like to understand the dynamics of sailing..

Form what I have understood the mast rotation is used to redirect wind flow..

How to apply this information is clear..

Pull on rotation downwind and leave it free when pointing.

However one of the posts suggests pulling on rotation upwind to depower you main which

on a very windy day might be handy or I could simply point higher to depower which to me sounds like a better solution to depowering your main. Any thoughts out there on this topic?

[This message has been edited by zeflyguy (edited 30 January 2007).]

[This message has been edited by zeflyguy (edited 30 January 2007).]

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My brother and I sail a 5.8 so it may be a bit different but we heading up alittle to depower a little rather than adjusting to much and where finding it possible to point as high any cat on the water and still maintain a fair bit of speed and make it a very comfortable ride.

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Mast rotation is critical in maintaining attached flow on the lee of the main.


Reducing rotation to depower is allowing the top of the mast to fall away, opening up the leach.

If you try to sail higher when over powered without flattening out the main and opening up the leach, then you will sail very slow, getting knocked on your ear more than making headway.

When overpowered, make the following adjustments in this order.

Main outhaul in

Cunningham tension

Lift boards 8 to 12 inches.

Drop traveller 6 to 8 inches

Reduce mast rotation.

Mast rotation last resort. I have very rearly resorted to reducing rotation even upto 25 knots.

Best way to combat being overpowered is to keep the speed up. Don't try and feather the boat up without speed or you will just get knocked on your ear.

Check out this link for some info regading sailing with a wing mast.


[This message has been edited by tornado (edited 30 January 2007).]

[This message has been edited by tornado (edited 30 January 2007).]

[This message has been edited by tornado (edited 30 January 2007).]

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What Tornado says is correct...

After aerodynamic efficiency, the question of rotation and depowering...

To rotate to 90 degrees or de-rotate to zero is mostly a question of the shape, size & wall thickness of the section.

I.e. Older small sections (E5308, like Hydra's, Mozzies and Cobra's etc) and new wing masts benefit from DE-rotation allowing the masthead to "flick" off to leeward, opening up the head of the main & de-powering.

Sections like on the 14sq, 16sq and 5.8 are strong enough to OVER-rotate to depower. I.E., Out to 90 deg.

The net affect is similar in that the leech of the main opens up, but you won't lose as much height. On these boats i wouldn't be inclined to bring rotation in to the centreline until it was blowing snotters (30kn +).

Remember too that Diamond tension, spreader rake and traveller position play a critical role in all of this...

Hope it helps,



[This message has been edited by Leapin Leroy (edited 31 January 2007).]

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