- Jan 5View SourceMason the sails are made by Manchester and are very well made. The main has a LOT of shape, but is designed by the placement of the reef cringles to increasingly flatten the sail as reefs (3) are taken in. The third reef produces an almost flat sail. Phil commented favorably on that sail when he sailed in her. As you know he felt strongly most four sided sails these days are cut too flat. For a dinghy, with its size and somewhat limited stability I would assume you would want a somewhat flatter sail so as to better spill the wind.The WW mizzen sail is a four-sided sail with a short gaff and a sprit boom. It is cut completely flat.
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On Jan 5, 2014, at 10:41 AM, "mason smith" <masonsmith@...> wrote:
Anent this subject of flat vs shaped sails I have had some interesting experiences. First with respect to lug sails. According to my understanding, the wisdom around WoodenBoat was that lug sails, as for the Nutshell Pram, should be flat, and, according to my understanding, Robin Lincoln made them flat for the Nutshells. When I rigged my earliest Goodboats for sailing, I had Robin make standing lugsails for me. They were, I believe, utterly flat. When I needed sails sooner than Robin could supply them, I got some from Douglas Fowler, who put about 8 inches of draft in my approximately 72 sq. ft. sails. In identical boats and crews, they literally sailed circles around the flat sails.
In sailing my Micro, with sprit-boomed leg-o’mutton sails, as in sailing my Goodboats with their standing lugs, I find that lots of draft is usually good, even in surprisingly strong winds, so I set the snotter just hard enough to keep the luff full. These sails reshape the wind even in their lower parts, so that they themselves alter the apparent wind greatly, at the luff. There’s more forward vector in the resultant force and less heeling moment. As for sheeting, I have never found a set of conditions where the Micro likes to be sheeted anywhere near the centerline.
PCB has pointed out how much the cut of the sails affects the performance of 4-sided sails. How do you tell? I have wondered whether the Whalewatcher I built for Pat Connor had the benefit of really well-cut sails. They are pretty, and that boat sails very well, but how well cut are the sails, and how well could it sail? There’s only the one example.
I have some experience in sailing the decked sailing canoes of the late 19th century, especially Rushton Vespers. In them, the various spars of the antique bat-wing or “modified Bailey rig” are stiff. They are apparently intended to make the sails as flat as possible. Those old boats do sail, and are great fun to sail, but it would be charming to see what they would do with airfoils in place of inclined planes for sails.
Can’t resist a comment on boomless loose-footed sails. I have had two Drascombe Luggers, which sport this kind of sails in gunther yawls and have a great reputation. On both of them I was so annoyed by bad, baggy sail shape off the wind that I rigged sprit-booms, for safety and performance. Spritbooms are not really convenient on gunthers but I rigged them and they were worth the inconvenience. On the second one, I laminated a curved sprit-boom that I called a half-wishbone. Instead of a snotter it was fastened to the mast with a little connector and a vestige of the other half of the wishbone, if you can picture that. This juncture wrapped around the front of the mast and was held by a lashing that went around the after side of the mast, as on a windsurfer. The draft was controlled by an outhaul near the clew, easily reached at the helm. So rigged, with decent sail shape on reaches and runs, my Lugger easily beat the fleet at the North American Drascombe meet and in match races against all comers including the much longer Longboats. I was given the trophy somewhat reluctantly.
That don’t prove anything about the flat vs cut sails argument but I would say that the shape a flat sail takes up when the snotter is loose is nowhere near optimal. It’ll sail, agreed, but it will not yield the “supplementary clean gain” that a well-cut sail will. I don’t consider good sail shape a luxury on a sailboat, and even if I made my own sails out of Tyvek, I’d build shape into them, and rather more than less, for the kinds of slowish, smallish boats I sail.
I've recently experimented with a FLAT cut Leg Of Mutton Sprit boomed
Sail..This was my FIRST flat cut sail but I had read that someone was
doing it so I wanted to give it a try...
This is what I learned...First,, the wind was about 10 to 15 miles per
hour and my snotter is adjustable from the cockpit.. I always do that
no matter on all my boats. So I was confident with the adjustment.
The boat sailed crappy and would not point well at all. In fact I was
being blown lee so I tossed out an anchor and played with the rigging.
First. I thought it was the lee Board so I swung it back and forth but
no sail would not p
From my experience in Sprit Sails with darts I felt the camber was
right if not on the TO much side so I tightened the sail some then
some more and finally flat. NOPE. Did not work..
Finally I decided to let TO MUCH sail out and see what happens. The
sail began to pull..
I was off the wind and zooming along at a nice heel. The boat was
surprisingly active and fun.
Then I went down wind right up into a cove came about into a head wind
and began to tack out.
On each tack the boat moved well giving me the illusion I was tacking
back into the open waters BUT I realized I was NOT making good head
way. In fact I kept arriving almost at the exact spot on the shore
line with each tack so I realized something was amiss and I tossed out
the anchor again and started playing with the rigging..
Lee Board swung aft did not work so I swung it forward yet nothing was working..
Then I remembered how I had to let out TO MUCH slack on the snotter to
get it moving so I said, WHY NOT try that..
Then I let out a LOT more camber than I would normally consider and
pulled the sheet in line with the center line of the boat and that did
She pointed close to the wind and when I once again hit the open lake
she heeled over steeply and sailed like a dream. In fact I was moving
faster now with all that big camber than before..
Here, all this time I had always had to TIGHTEN my sprit sail to point
into a stiff wind but now with the flat cut sail I was sailing
windward with a VERY Loose Snotter....
The trick to point into the wind on this flat cut LOM seems to be to
have a LOOSE sail creating lots of camber and the boom sheeted near
the center line..
I was on the far side of the lake when the wind dropped late in the
evening like it does most of the time on this lake.. I moved forward
so the boat sit on the rocker and sailed her flat. The sail was
cleated off and the rudder tied off. The boat moved slowly along but
very predictable. Then I made a turn for the landing with a light tail
wind.. The boat seemed to be bogged down and it was getting late in
the evening so I sat on the same side as the sail heeling the boat as
far over as was safe.. The light tail wind filled that big ole loose
sail and we moved nicely along reaching the distant shore long before
the sun disappeared..
What I liked about the Flat Cut sail is it's FAST and EASY to make.
Sailing it was DIFFERENT but once I caught on it worked great..
I am not sure IF I will continue to use Flat triangle sails or not but
I did learn they can be made to work if you fly the snotter as loose
as you can given the wind conditions..
Good night, Chief..
On 1/4/14, c.ruzer@... <c.ruzer@...> wrote:
> How about those traditional sharpie "simple but sophisticated sprit-boomed
> leg-o'-mutton rigs"? I knew the trick to adjust draft in the sail, make it
> fuller in light wind for more power or flatten it when the wind gets up to
> de-power it by working the snotter on the sprit-boom. I've read about that
> just about evrywhere these sails are written of too. The benefits from being
> a self-vanging sail, done so simply, and eliminating twist without the
> bother of a mult-part kicker on the boom is often mentioned too.
> But of course there's going to be a little bit of give and stretch here and
> there in the rig, and the usual prescription is to tension the snotter as
> necessary to minimise the twist - but there's always still going to be some
> give - and you might be flattening the sail more than you want for best
> performance. So what to do? Well it's so easy and elegant, and if I've read
> or heard of it I've never taken it in before:
> "If we rig the snotter so that its height on the mast can be changed while
> underway, sail twist can be adjusted (ie. dialed in or dialed out). This
> simple adjustment can increase speed and dampen rhythmic downwind rolling."
> Your expensively cut modern bermudan mainsail and rig uses all those
> dollars and complicated highly tensioned mechanisms to adjust twist, but
> for the sharpie just use any simple way to alter the height of the snotter
> on the mast. Brilliant! I look forward to trying it.
> Twist, the right amount at the right time is good. The windspeed and
> underway the apparent wind angle too increase significantly with height
> above water. A sail that's twisted right with the head falling off just so
> presents an appropriately changing angle of attack to the changing wind
> angle and develops more power, is more efficient. When running minimise the
> twist to minimise oscilating vortices, no death rolls, and efficient.
> Is this trick of altering the snotter height mentioned in 103 Small Boat
> Rigs? That's a book I'm putting off getting - some say the best one (save
> the best till last;). I've not seen PCB or Chapelle write about this. In one
> of his books Dynamite comments on the low angle of a sprit-boom as drawn
> saying it would be better at tensioning the foot if it bisected the clew
> angle. He was thinking only of how much more he could flatten the sail with
> less effort applied to tensioning the snotter and said he'd mention it to
> PCB. I think all those 59sqft LOM sails afterward are shown with more of the
> sprit-boom angle Dynamite was after.
> Anyway there's a few more good sharpie sail tips here: