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Byte CII and weather helm

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tack'ho View Drop Down
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Post Options Post Options   Quote tack'ho Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 09 at 3:22pm

Originally posted by Jon Emmett

On another point you need a consistent angle of heel for a Laser which is just off flat (to hold the centreboard securely in it's casing so it doesn't wobble about too much.

As ever I stand corrected



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zailor View Drop Down
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Post Options Post Options   Quote zailor Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 09 at 5:43pm

Well you learn something useful everyday.

 

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Medway Maniac View Drop Down
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Post Options Post Options   Quote Medway Maniac Quote  Post ReplyReply Direct Link To This Post Posted: 27 May 09 at 10:37am

Originally posted by Jon Emmett

If you have non-stretch rope and it slips a couple of mm then the rudder raises a corresponding amount.

If the rope is stretchy and pulled really tight then the rudder is held really tight and if it slips very slightly the rudder is still held really tight.

By that logic, shouldn't we all be using stretchy main halyards? Or is the trick to use the stretchy stuff only on the 3:1 adjuster and non-stretch on the rest (majority)

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Jon Emmett View Drop Down
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Post Options Post Options   Quote Jon Emmett Quote  Post ReplyReply Direct Link To This Post Posted: 27 May 09 at 11:48am
Haylards are usually 1:1 so you do not want any stretch in the rope. When you put on the cunningham you add huge amounts of loads to the Halyard which would pull the sail down the mast (if it stretch 5mm it would come down 5mm).

The length of a typical halyard (which goes from the top to the bottom of the mast) is also much greater than that of a rudder downhaul. So an approx 1% strech in a Halyard may be 5mm where a 1% strech in a rudder downhaul may well be less than 1mm.  

The loads on the rudder are relatively small and with low stretch rope it can be hard to get it to sit fully in the teeth of the cleat or other jammer (it may will slip 1 or 2 mm) which is far less than 1/3 mm (1mm stretch taking into account 3 to 1 sytem) due to stretch.Remembering when you pull a rope very tight (low or high stretch) it sits in the cleat better.
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Post Options Post Options   Quote Lukepiewalker Quote  Post ReplyReply Direct Link To This Post Posted: 27 May 09 at 12:46pm
I like to think of it as a little shock absorber in case of grounding too.
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Post Options Post Options   Quote laser193713 Quote  Post ReplyReply Direct Link To This Post Posted: 27 May 09 at 1:29pm

with your halyard you dont pull it hard up against the top of the mast, it slipping down 2mm because of the cleat wont slow you down, with the rudder though you pull it down so it is resting tight against whatever is stopping it going down further...to keep it close you need to be able to pull the rope that 2mm further using the stretch so that when it cleats and falls back that 2mm it is held by the unstretched rope in the same place.  To make up for this with your halyard you should just pull it up slightly higher to allow for the slippage in the cleat.

 

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Post Options Post Options   Quote zailor Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 09 at 10:04pm

Originally posted by Jon Emmett



For the rudder buy a new cleat and some stretchy rope and put in a purchase system.


Can you recomend a rope make/model/type?

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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 09 at 10:22pm
Originally posted by Jon Emmett

On another point you need a consistent angle of heel for a Laser which is just off flat (to hold the centreboard securely in it's casing so it doesn't wobble about too much.

Could you explain how that works please? If the water is flat then surely the board will be held against the casing by the side load (unless you are on an absolutely dead run, which isn't fast) and if you are not in flat water but being joggled about by waves why should a bit of heel help?
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Jon Emmett View Drop Down
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Post Options Post Options   Quote Jon Emmett Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 09 at 8:58am
I would go to Rooster for rope and the cleat.

Regards the Laser Centreboard if the boat is dead flat there is a chance that in the advent of header or lull the boat will come on top of you then when the boat goes to leeward or back flat again the board will wobble in the casing losing flow.

By having a (very small amount of leeward heel) which to most people seems like the boat is flat (and from a coaching perspective we are usually saying get the boat flat - just like we say hike straight legged <but really mean just off straight>) we ensure the board is held against the casing (the bottom of the board on the windward side and the top on the leeward) at all times.
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Post Options Post Options   Quote Daniel Holman Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 09 at 9:13am

Jim is right re: the sideforce keeping the dagger in position in the laser. It usually comes up when going in for a tack, or going in to adjust something, usually when slamming on a wave. Keep on buying those crappy pieces of rubber for a fiver.

Const leeward heel is important because it means that the rudder and dagger loading is (more) constant. Less experienced sailors will often, through lack of steering / sheeting / kinetics have their boats cyclicly heeling hard, then on top of them. This feeling of the boat "staggering around" upwind means that there is alternatively big weather and lee helm, both of which are slow, to reactively correct the situation. A really quick sailor will be using his/her weight and steering fairly aggresively upwind in breeze to keep the constant heel

The laser likes about 5 deg leeward heel upwind. This is beacuse it is a shallow and flat bottomed boat, limited in righting moment, so the small heel angle significantly shifts the centre of bouyancy to leeward, and thus increases the righting arm. This gain is enough to mitigate some of the negative effects of too much heel, such as weather helm. To a point...

Most sailors think they're flat when they're at 5 or 10 deg though.

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