[C320-list] double main sheet control?

[Jeff Hare]

Here are my thoughts, I have a lot to learn here, and there may be many
different ways of looking at this or different explanations, so take it at
face value.  Feel free to correct me wherever I'm wrong here.

In my simple mind, mainsail trim all boils down these 3 things:  (anything
more complicated than this and my head pops).

  1) adjusting the tension on the three edges of the main sail.
  2) trimming the boom in and out to get the leading edge of the main lined
up properly with the wind.
  3) adjusting the foil shape of the sail (DRAFT and DRAFT Position).. how
flat or curved the sail is allowed to be and how far away from the mast the
deepest part of the curve sits.

LEECH SHAPE is how straight you keep the back edge of the sail. ( to
controls twist).
DRAFT is how much belly you have/allow in the sail  (controls amount of
power generated)
DRAFT LOCATION is how close to the mast the deepest part of the belly is.
(controls how far aft the center of power occurs which acts like a lever
against the mast)

Now, controlling the three edges of the sail:

Tension of the FOOT of the sail with the outhaul the sail helps flatten the
sail somewhat. Lots more when you have a loose footed main.
Tension of the LUFF with the Halyard and Cunningham moves the DRAFT LOCATION
(forward I believe to reduce the leverage effect and stop rounding up so
much).
Tension of the LEECH with the mainsheet/traveler when going upwind, and the
Boom vang when heading off wind controls twist.

The mainsheet traveler can be pulled to way to windward, but the boom itself
should NEVER (in my experience) be windward of the centerline.  Generally I
find that if I needed to pull the traveler way up to windward, it's because
I'm close hauled in medium light wind and want a little twist.  Without
pulling the traveler up to windward, I can't get the boom centerline without
pulling DOWN too hard on the boom and removing all my twist.

Keep in mind when you're heeled, your sail isn't straight up and down, so
the wind is running not horizontally across your sail but partially UP your
sail, so look at the shape of the sail along the path of the sail the wind
sees and look to optimize that foil.

Alas, I always lose when racing.   Both times...  :)  But I like to cruise
FAST.  :)

-Jeff

-----Original Message-----
From: c320-list-bounces at lists.catalina320.com
[mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Dennis Harris
Sent: Friday, September 14, 2012 3:24 PM
To: C320-List at Catalina320.com
Subject: Re: [C320-list] double main sheet control?

Chris or others,

On moving draft with mainsheet, please elaborate how/when this is done.  If
boom height is controlled via vang, then it seems that mainsheet simply
extends the range of movement of angle of attack greater than allowed with
the traveler.

Dennis Harris   C-320 #694

-----Original Message-----
From: Chris Burti
Sent: Friday, September 14, 2012 12:21 PM
To: C320-List at catalina320.com
Subject: Re: [C320-list] double main sheet control?

Proper sail trim dictates that you use the traveller primarily for changing
the angle of attack, the vang for pulling the boom down or raising it to
reduce twist, the mainsheet, outhaul and halyard/cunningham to move the
draft of the sail forward or aft.

If you wish to move the boom in heavy air without using the winch, either
luff up a little or ease the vang to reduce pressure on the sail. Either end
of the sheet may be used. Both ends of the traveler should be synced.


On Thu, Sep 13, 2012 at 4:35 PM, Gene Helfman <genehelfman at gmail.com> wrote:
>  Having sailed for 50+ years on boats with only one main sheet, I'll 
> admit to being totally perplexed with the port and starboard sheet 
> arrangement on the 320, especially when going upwind in anything other 
> than light air.
>
> My instincts tell me that hardening the upwind sheet should pull the 
> boom down and also bring it to windward (recognizing that the traveler 
> also determines boom alignment).  To do this, do you slack the downwind
sheet?
>  When I do this, the boom moves quickly downwind, making it even 
> harder to pull the boom and sail to the upwind side, often requiring 
> putting the sheet on the winch and cranking hard.  Is there a protocol?
>
> thanks,
> gene
> Satori #398
> Gene Helfman, Professor Emeritus
> Odum School of Ecology, University of Georgia PERMANENT address:
>     498 Shoreland Dr., Lopez Is., WA 98261
>     (360) 468-2136
>     genehelfman at gmail.com
>
> "Give a man a fish and he'll eat for a day, Teach a man to fish and 
> he'll deplete the
>       oceans."
>
> The Book of Bob, Ironies 24:7



--
Chris Burti
Farmville, NC