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Rake and Tension


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Ok guys, given that most of my sailing has been small(ish) boats with one hull, I have a serious question about rig setup for the GBE.

 

How much rake or helm, and how much shroud tension?

 

I've noticed there seems to be a lot of slack in the rigging, the lee shroud flopping around a lot, and a correspondingly large amount of forestay sag if I'm not cranking the mainsheet hard. 

 

My rig also seems quite upright, and with full sail I seem to have pretty neutral helm. On mono's I tend to aim for a tiny amount of weather helm, should I do the same in the cat, or does that just equate to two rudder blades dragging? I'm talking static helm, then I trim to balance in dinghy's, but obviously that doesn't work too well in a cat.

 

As I have an old-style pinhead main, I don't feel the need to crank on lots of mainsheet, and when I've tried it, the top of the main stalls out and we slow down, which is a large part of why I'm asking for thoughts on rake and rig tension.

 

I will say, however, that once we get out in some decent breeze (over abut 10 knots) I may find I need much more sheet tension. It just hasn't happened yet.

 

Oh, and on a related topic, is mast rotation pretty auto in most of the cats this size? I have to physically pull it around during each tack.

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Upwind. Flying a hull is what makes the GBE change gear and comes up 10 degrees or more.

 

We sail  more by the GPS than the woollies or sail shape, reach until we get the most speed possible then, crank  the head sail on as much as we can and close the slot. At the same time sheet the main so that the top back winds, crinkles and keep pushing the boat down as much as you can.

 

We keep the crew forward and to leeward to dig the nose down and keep the hull flying. The kids love it. One of them holds the GPS and tells me when we slow down. Speed is your friend.

 

Quite different to a mono hull.

 

Rotation of the mast is not an issue when everything is cranked on. Good idea to have less rotation when overpowered. 

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My two pence on balance:

 

If rudders are not contributing to lift they are *only* drag.

 

Drag vs Lift follows a quadratic curve so adding a little lift (from zero) on the rudders increase their drag slightly while the daggers are operating further up their drag-vs-lift curves and will loose more drag as the rudders start to share the load. This reasoning assumes rudders are reasonably sized and deep.

 

If the centre of effort of the rudders are on or very close their axle through their pintles there will be very little tiller load and if you are used to a heavy-on-the-tiller mono you may find it hard to 'read' the cat balance from the tillers.

 

I do not know what prevents your rig from rotating. Bring someone experienced along for a ride.

 

/Martin

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