Trying these out today as I have been thinking they are a good idea for years on trailing edge of square tops.
Chance for you to tell me how mentally challenged I am Wouts.

Do you have a bigger picture? Cant make out where on the sail this is.

Looks like the end of a batten.

That looks very much like the wingtips on the Airbus 320 and 310! I have wondered if it would work on a sail. Let us know if you see any difference, I think it might need to be bigger though. http://www.jetphotos.net/viewphoto.php?id=264848

The other thing I have thought about was adding vortex generators to the main about a foot back from the mast, for light air sailing.

Top batten at aft end of square top.
Designed to lessen drag of vortex. SImilar to eagles wing tips. You will notice they curve up and yes the plane manufacturers are now using them to improve economy.
Yes, they may need to be bigger.

How are you going to tie it in?

Don't you need a hole somewhere to tie it into the batten pocket?

I think this was talked about some time ago. The topic being winglets, the term used for plane wings. Instead of on the end of a batten, why not the mast itself? The idea of a winglet is not one of added lift, rather it is of decreased drag.

One could make a winglet for a mast that even had some floatation in it, no? Most winglets are on the top surface only, even the airbus has a larger surface on the top, than on the bottom. I think it was conveyed that the winglet on a mast would indeed count towards sail area.

As far as vortex generators go, I don't know that you would get the same effect on a sail as you would a wing. The purpose is indeed for 'slow-flight', but, it is mostly to keep attachment over the aileron.

Might be curious to see this develop thru the years....

Yes, I photographed them the minute I had fitted the batten snugly and just after this photo I marked the holes and drilled them.
All works well.

As it happens a friends giant carbon wing sail was destroyed in a storm last year and I will form the batten out of the sides of that once I have had feedback about size etc. so the weight can be reduced.

FYI
Looking at this bird one wonders if the wing on a sail could be a cloth hinged unit that flipped over to the other side on tack as the bird and plane both exit the shape to the "lift" side.

Makes sense. And if the vortex itself isn't enought to tack the winglet, the inversion of curvature of the batten in a tack can generate the force needed to do the job.

In the picture attached, I suspect the feathers on the tip of the eagle's wings are there for stability in slow flight - not efficiency. They may even have very little affect on the airflow but may just be positioned that way to give the bird additional feedback about the airflow conditions on each end of it's wing so it can avoid a stall condition.

looks like you lost a little weight in your avitar Jake!

And he gave up smoking....

I thought that was just how he looked after the Tybee 500.
<img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" />

I don't need to smoke anymore - I got my a-cat smoking now.

I "DIG" them gloves!

You wouldn't want dish-pan hands while fighting crime (yes i am assuming you are a crime fighter... why else wear a cape!?)

That's what it's all about. Crime and dirty windows.

The joker read that and said ... "Why So Seriousssssss"
and then licked his lips and went running off the other direction. <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" />

how do the ice boat masts work? They look like they are warped in some way

I should stay out of this since I have absolutely no aerodynamic training, but as I understand it (from years of training on the Discovery Channel) the winglet, as well as those little fins that they stick on the top of plane wings were put in place to keep the air from spilling off the end of the wing thus keeping the flow more front to back and there for making it more efficient. Improved air flow/attachment equals less power needed to generate the same amount of lift.