Daysailer Sails... weird shape?

Moderator: GreenLake

Daysailer Sails... weird shape?

Postby kobaz » Sun Jun 14, 2020 1:24 pm

Hi,

In relation to my newly wet boat:
Little bit of cleanup/history here: viewtopic.php?f=1&t=6247

The sails that came with the boat are not flat at the bottom...

There is a weird camber to the main sail.. when hoisted fully, there's a bit of a flappy channel that's created... is this on purpose? Is there a reason for this? Or is this the age of the sails (definitely far from new... about 15-20 years old).

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0614201319r.jpg (19.15 KiB) Viewed 879 times

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0614201319cr.jpg (28.74 KiB) Viewed 879 times


They do look like they were made this way. There's a straight run of stitching from the tack to the clew a few inches higher than the foot of the sail.
kobaz
 
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Re: Daysailer Sails... weird shape?

Postby igotit » Sun Jun 14, 2020 3:46 pm

I know nothing bout sails and shapes,ive never sailed my ds1,but i believe my sail is just like yours.never even hoisted mine.i assumed this was normal and standard shape.
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Re: Daysailer Sails... weird shape?

Postby GreenLake » Sun Jun 14, 2020 4:06 pm

Sails are never flat. That's the reason they are divided into panels that are broadseamed: this allows the sail to take on the curved profile that maximizes their aerodynamic efficiency.

When a sail has a boltrope along the foot, that part of it has to be in a straight line (because it's attached to a straight boom). However, the sail above should have some camber (a bit of a belly), so there needs to be some fabric that allows for that transition. That is called a "shelf". You will not find it in "loose footed" sails, that are connected at tack and clew only.

Once used often/hard enough, sail cloth will stretch and distort the intended sail shape. The sail becomes "blown out". Unless you are a sailmaker, I suspect you'll have to hoist your sail and try it out to know how well it (still) sets. In a mainsail, for example, the camber (maximum depth) may be too far aft in a used sail and too deep - the effect is that the boat responds more by heeling than accelerating when hit by a gust.

In a jib, you might see flutter in the leech. I had an old jib that had developed a flutter in the leech and nothing I would do would make it set. I inserted a very thin "leech line" into the seam at the leech and tightened it just a bit until the flutter stopped. However, I got new sails shortly thereafter, because the leech line had to be so tight that it caused a "hook" in the sail at the leech, which really does nothing for the aerodynamics. However, that leech line allowed me to continue sailing until the new sails arrived.

Sails are "consumables" - sailing with them "uses them up". I like to compare that to break pads or tires on a car. They do wear out and need to be replaced in regular intervals. If you're not demanding, you can use them for while once they are past their prime, but eventually, like that jib I mentioned, you'll work around their developing deficiencies instead of enjoying them. That set of sails I squeezed about 150 uses out of; I didn't buy the cheapest, so I figure, I spent around $7.50 on sails each time I went out. A cheaper set might have reduced that to $3.50, but would they have held up as well, and as long?

Go sailing and see whether your jib sets without leech flutter, whether your main can be flattened with outhaul and/or cunningham and whether the deepest camber of your sail is still forward of the midline. If your sails come up short, plan on replacing them, but the "weird" shape you see when you unroll them on the ground is not something to worry about - it's as it should be. Sails are not flat.
~ green ~ lake ~ ~
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Re: Daysailer Sails... weird shape?

Postby tomodda » Sun Jun 14, 2020 4:33 pm

What GL wrote... that's the shelf. The max depth of the sail camber (curve as seen from above when full of wind) should usually be 1/3 of the way back. In your first photo that the max depth of the curve in the boltrope/foot of the sail is also 1/3 of the way back. When the sail is bent to the boom, the bolt rope goes flat which means that same curve will be set into the bottom of the sail. Same all the way up.

You do want to move the max camber forward/back depending on the wind speed and how close you are sailing to the wind. You use the Cunningham (or a mainsail downhaul) and the outhaul to control the camber. Think of it like gears on a car, works the same way, trading off power vs speed. Read, ask others, observe, and experiment and learn. That's the fun of sailing, at least in my not humble opinion.
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