Sail and rig setup

[smight]

Merry Christmas n12 ers

Having sailed on boxing day (too much food led to a very bubbly transom) we finally had a good look at the mainsail and we seem to have a starvation crease from the hounds to the clew. Roughly force 3 with some usual bough beech gusts.

Running around 25 on the shrouds (loos gauge) not sure of other settings. We did feel a little underpowered especially on the reaches and I felt like I needed a fair bit of kicker to control the roach in the leech.

Any pointers would be much appreciated.

Thanks

George and Alice  3520

[smight]

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[grazz]

George,

Have you had a look at the tuning guide on the website. It should give you a pretty good set of steps to solve your problem

http://www.national12.org/downloads/tuning_guide_revised_2004_v1.pdf

Merry Christmas

Graham

[gbr1918]

From a standpoint of total absolute ignorance, just looking at the pic in your original post there looks to be a truckload of mast prebend.  More mast bend than luff curve is  what I think causes your hounds-to-clew crease, so would pulling the ram on to straighten the mast up a bit fix the problem?  (Couldn't work your 'more pics' link.  There may be more to be gleaned)
Dave Cooper   

[JohnM]

George

I agree with have a look at the tuning guide...

And I also agree that your mast looks very bent for offwind sailing.  The problem to deal with in a 12 is that your mainsail needs to be flat enough upwind to get you upwind but it is also your most important downwind sail - it is also your spinnaker!

You need to get used to throwing your rig around a lot to create different settings.  Downwind, ease the leeward shroud, pull the jib halyard on to move the mast forwards (NB adjust the ram lowers so that you don't invert the rig too much.  A little bit is inevitable / OK in my experience).  You can also ease the windward shroud a little too.

I don't know about 25 on loos as a setting.  I set up my rake that I want and then pull on my shrouds until the leeward one is not floppy.  This means more rig tension until we are both on the edge.  Before I start to depower I then pull it on even more!.  The problem is that the more you pull your rig tension on it looks like the more bend you are currently inducing in your mast.  This means that the distance between the hounds and the deck decreases due to excess bend and you lose power from your rig.

This is helpful too

https://www.pinbax.com/docs/Science%20Behind%20Sails.pdf

John

[smight]

Thanks for the replies all. I have read the tuning guide and definitely need to have a measure and a fiddle with the rig.

My initial feeling is the the spreaders are swept back too much, setting us up for too much prebend. I think we need to make the rig easier to tweek on the go as it's a bit of a process to get jib tension on and off!

What effect does mast foot positon have on the rig ?

Thanks again.

George

[JohnM]

George

I agree the spreaders are a good start point.  With tension on a tiny amount of bend is ok.  I would roll the boat over and put tape across the shroud base and across the spreader ends and move them keeping things parallel to each other when you view from the top of the mast.

Take measurements such as the width of the shroud base and the distance between the spreader ends and do some basic trigonometry.  You knew that one day this would come in useful!

The mast position is inextricably linked to the centreboard position as the board and rig both have a centre of effort.  You change the CoE of the rig by raking it and the board by rotating it.  Moving the mast position is possible, but much harder to change the centreboard pivot!  Most people only have a small amount of range for moving the mast foot.  If you change it then you need to start again with all of your trigonometry.

Essentially move the bottom forwards and the top will move forwards (reducing your rake) unless you angle it backwards to maintain the rake.  vice versa if you move it backwards.

From the photo i don't think this is likely to be your issue.  I would start by trying to get your mast straighter and then get used to throwing it around more between upwind and downwind.

John   

[smight]

Thanks John,

I feel a Saturday of bimbling coming on.

Will keep you posted.

George

[smight]

Update no 1:

Spreaders had a fair bit of sweep back so we have straightened these up, running less tension and less kicker and the sail seems to be much less creased. Power was tricky to gauge as we sailed on a day with little breeze. Certainly happier with how everything looks so hopefully the speed will come with it!

Thanks to all for hints and tips so far

George

[smight]

Update no 2,

Sail looks as if it is set better, still struggling for power a bit that may be not sailing in the right breeze as much as anything else!

What are people's go to control to power up first? Thinking shifty gusty lake, would it be cunningham or something a bit less obvious?

Also do you have a picture of the shroud Base trig you were referring to John?

Thanks all.

George

[JayHaich]

In gusty conditions upwind we try to set the rig to power for the lighter patches. So minimal starvation creases, lee shroud just slack when hiking upwind.  Then during gusts pull the kicker on to flatten the sail, making sure to ease again in the lulls.  So the kicker becomes the power control.

Downwind kicker, cunno, outhaul and lee shroud off.  We try to ease the cunno and kicker just before the windward mark for a quick bear away, then slacken outhaul and finally kicker again after the shroud is off.  If it is really windy it pays to keep the lee shroud and / or outhaul on to avoid being overpowered. 

I think the lee shroud has the biggest effect on downwind power.  but it is hard to play to gusts so it's generally a decision at the windward mark. 

Hopefully Graham or Tom will disclose their secrets to correct me.

[Thomas Stewart]

The picture shows too much kicker and too much leeward shroud on.
We can have a tuning session/ training session if you like, call me on 01473694714 daytime

[smight]

Sounds good to me Tom!