[Public-List] New mainsail...

[Greg Hounsell]

Thanks Gord!

On Sun, Jun 23, 2019, 4:44 PM Gordon Laco via Public-List <
public-list at lists.alberg30.org> wrote:

> Hello Michael.
>
> In basic principals, mainsails are made with a three-dimensional shape in
> them that is in the form of the classic aircraft wing ‘airfoil’ wing shape…
> rather just the top surface of the wing shape because the fabric the sail
> is made of has negligible thickness.
>
> When the sail is set and trimmed for the apparent wind, you can see its
> shape when you look up at it.   You’ll see that there is fullness or curve
> in the sail and you’ll be able to see where the deepest part of that curve
> is.   A ‘good’ sail which still retains the shape the sailmaker built into
> it, will have the deepest part of the curve somewhat further forward of the
> sail’s middle area.   There will be a curve near the luff, or leading edge,
> then a long flat area aft fo the deepest part.  This is the airfoil shape
> that means power.
>
> You can tweak the deepest part of the curve forward by increasing tension
> on the luff of the sail… this is done by increasing halyard tension, by
> pulling down on the downhaul under the gooseneck (this is why its important
> to have the gooseneck on a track) and by pulling down on the fabric of the
> leading edge of the sail from the tack (lower forward corner) using the
> ‘Cunningham’ (this adjustment was really developed by a guy of that name…)
>
> When the sail is in good condition, these tweaks will help get the best
> out of the sail… but sails don’t last forever.  Dacron sailcloth is made
> with a resin that helps lock the warp and weft of the cloth in stability…
> but UV radiation and flogging breaks down the resin resulting in stretchier
> sail cloth… and that results in sails that are termed ‘bagged out’.
>
> One symptom of a bagged out sail is that deepest part of the curve, the
> draft, that I mentioned above, moving aft.  Once the sail deforms so that
> deepest part of the draft or curve is too far aft and instead of developing
> power to drive the boat forward, the sail ends up developing more heeling
> force that usable power.   The result of this is that for a given wind
> speed, the boat heels over more… that means the weather helm required to
> keep her head down and on course increases, and that means that you’re
> sailing with more angle on the rudder than is desirable.  If you feel a lot
> of ‘weight’ on the tiller, well that’s directly related to the drag the
> rudder is putting on the boat.   The obvious cure is the ease the
> mainsail’s sheet to let the boat back on her feet a little,… but sailing
> with the sheet eased is not fast because the sail isn’t driving the boat
> like it should.
>
> Another negative development in an aging sail is that stretchiness I
> mentioned above that comes into the picture as the resin in the cloth is
> broken down.  As the load on the sail increases in heavier air, the sail
> cloth stretches and INCREASES its fullness… exactly the opposite of what
> you want in order to control the boat.  This exacerbates the problems being
> created by the draft of the sail moving aft as the sail ages and deforms…
>
> So how do you know if your main has these problems?
>
> First off, if your mainsail is more that ten years or so old, you can
> assume that it’s far past it’s prime with regard to shape.  It is entirely
> possible that the sail is still strong, but with regard to shape it is
> shot… bagged out.
>
> Well you might say, I’m a cruising sailor and I don’t care so much about
> fine points of performance…. to that I would suggest that for cruising
> sailors good sails are more important than they are to racing sailors
> because cruising sailors are concerned with safety and seaworthiness rather
> than winning races.   Sails with good powerful shapes will let the boat
> sail without drama in higher winds than bagged out sails… you’ll go to
> windward better, you’ll have to reef later, you’ll generally have a better
> safer sailing boat.
>
> There’s lots on line about this stuff, please feel free to ask as you get
> into it…
>
> Gordon Laco
> #426 Surprise
>
>
>
>
> > On Jun 23, 2019, at 1:32 PM, Michael Devonshire <
> Devonshire at jhpokorny.com> wrote:
> >
> > Gordon, as a “newbie” here, can you give me a hint about how to tell
> if/when a mating is bagged?
> > Thanks
> > Mike D
> > Pickle 619
> >
> > Sent from my iPhone
> >
> >> On Jun 23, 2019, at 11:55 AM, Gordon Laco via Public-List <
> public-list at lists.alberg30.org> wrote:
> >>
> >> Hello Gang,
> >>
> >> I must be becoming an adult…
> >>
> >> Last year I bit the bullet and bought a new genoa.  A new sail is a
> wonderful thing, but sadly I didn’t notice much of a change in SURPRISE’s
> performance.  Silly me, I realized later that our main was long past the
> blush of youth and it’s the main getting bagged out that leads to heavy
> helm, and that leads to a slow boat upwind.
> >>
> >> So this spring I ordered a new main.  Now I’ve got a one year old genny
> and a brand new main.   I’ve finally broken the silly schedule I was on
> where I always had one old sail and one new one.  We bent the main on last
> night… can’t wait to take it out for its first sail.
> >>
> >> A new sail is truly a wonderful thing…
> >>
> >> Gordon Laco
> >> #426 Surprise
> >>
> >> PS - I can’t remember how many times I’ve been told by A30 sailors that
> our boats have mains that are too big, and that is why their boats are
> heavy on the helm.  I met one fellow who told me he was using an old Dragon
> main and he figured THAT, with it’s short foot, was a better sail.   No, no
> no.   The reason for heavy helm is either simply slack outhauls, incorrect
> mast rake, or bagged a bagged out mainsail that needs to be replaced.
> There’s no reason why an A30 shouldn’t be sweet-sailing with light helm…
> >>
> >>
> >>
> >>
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