[Public-List] New mainsail...

Sun Jun 23 18:30:16 PDT 2019

My pleasure. 

G

Sent from my iPhone

> On Jun 23, 2019, at 7:08 PM, Michael Devonshire <Devonshire at jhpokorny.com> wrote:
> 
> Gordon (AKA Sensei!)
> I could not have gotten a clearer or more precise illustration anywhere. A thousand thanks- and a smart bottle of Goslings for you if ever we meet!
> Mike
> Pickle #619
> 
> Sent from my iPhone
> 
> On Jun 23, 2019, at 4:44 PM, Gordon Laco <mainstay at csolve.net> 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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>> 