Use of mast screw

[Alistair Edwards]

I have now repaired Catatonic's mast screw. However I am not sure how I should be using it.

Should I disconnect it initially while I tension the jib halyard and shrouds, and then connect it to the mast and dial to the appropriate setting?

In light winds do I set it up to just resist mast bend, or should I actually use it to reduce the natural pre-bend of the mast?

In heavy winds do I use it to put additional bend into the mast, or just slacken it off so that the mast can bend in gusts?

Is it worth winding the screw forward downwind ? Approximately how many revolutions of the wheel would you make between the on and off settings (assuming constant mast rake)?

Is there any risk of overloading the threads on the plastic deck plate or will the mast resistance make it too difficult to dial in excessive load?

[Tim Gatti]

Alistair - you should find the answers to a lot of your questions about when to apply control at mast gate level during set-up and on the water in the Tuning Guide to be found elsewhere on the N12 site.
Tim

[MattStiles]

Hi Alistair,
I used to use it to force prebend on in a drifter, then
use it to hold the mast fairly straight as soon as there was more than
3 or 4 knts of wind, then induce some bend again once we ran out of
other ways to depower.
Never used to disconnect it at all, just put the rig tension on with it attached then adjust.

Downwind
- I don't remember having played with it much. Best to just ease the
shrouds to let the mast more upright / straighter without needing to
change the screw. But we only used to release the leeward shroud... I
imagine if you released the windward one to too much try to rake the
whole mast forward things could get a bit hairy unless you wound the
screw forward too. Sounds like too much faffing to be worth it to me ;-)

Matt

[Alistair Edwards]

Thanks Matt. That all makes lots of sense.

I am surprised at the range of mast movement you can achieve.
It almost looks as though you are changing the mast rake when you start winding the screw.

I am experimenting with different screw settings. Straightening the mast in light winds certainly generates
more power. I have done quite a lot of single handed sailing over the last couple of weeks so I am starting to get a real feel for the boat.

She is indeed fantastic upwind. Thanks for the kicker tip. Top batten now flicks nicely on most of my roll tacks.

My regular crew is sailing in Catatonic for the first time on Sunday. This will also be my first opportunity to gauge my speed against another 12 (or 2).

Have fun at Burghfield.

Alistair

[grazz]

Hi Alistair, I'm a bit late on responding to your post. The answer depends on many things including your sail shape, mast stiffness and crew weight. If you can spare the time the best thing to do is read the tuning guides (as Tim mentioned). They are at
 
http://www.national12.org/downloads/tuning_guide_revised_2004_v1.pdf

There are also lots of other coaching tips

http://www.national12.org/hints/coaching/coaching_tacking.shtml

Happy sailing

Graham