Winglets on trailing edge

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.
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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=

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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.

Winglets are there to help the tip vortex form in the tip of the wing instead of anywhere else, thus keeping the entire wing span effective for more time than without them.

An alternative theory is that the winglets are designed to

intercept

the vortex at an appropriate angle to produce thrust.

Consider a propeller spinning in a straight flow producing thrust. That's easy to understand because we see it all the time.

Now invert it so that a fixed foil is in a spinning flow. This is the case at the tip of a wing with a winglet attached.

The fluid wants to move from the high pressure side to the low pressure side which generates a vortex/twist in the flow. Put a small foil at a slight angle in the way of this twisting flow and you may be able to generate some thrust.

I really don't know. In fact, my previous post was based on what I could learn from Chapter 3.12 of John Denker's online book

, from where I quote the following:

My view is the following:
Sails are different from wings. A sail tip does not rotate/move due to boat motion/waves at speeds that are relatively high compared to the wind speed. IF winglets help keep the vortex in place, they could possibly boost performance.

All the time you blokes have spent looking up, YOUV'E JUST MISSED THE LAYLINE!

Sorry couldn't resist, Carry on, its good stuff [If I only understood it]

I believe that theory can be extended to the difference between old pin head sails and the newer square tops. The difference between the two is not complete to get more sail area up high...rather, on the pin head, as the air spills around the top of the sail on the windward side, it will curl around the back of the sail near the top. With the pin-head, this

leaking

air around the top would wash downward on the leeward side washing out some of the good airflow generating lift. By adding the square head, the amount of air that would leak to the backside is reduced. I believe the winglet takes this to the next step.

I don't know, wouldn't winglets increase the drag to leeward? And all the planes you see them on operate at fairly constant angles of attack, with the way cat masts move around it seems like it would add more drag, for example every time the bows go up and down over a wave it would raise and lower the angle, and keep shaking the airflow off. As a longtime hangglider pilot I've seen different tries at the winglet idea, and nobody has been able to make it work, mostly because every time the wing yaws a little it brings one side to too low an angle as the other side goes to too high an angle. One of those ideas that seem good but that don't work in actual use, maybe?

Maybe, maybe not.
Handgliders are closer to boat speeds, but don't have the same problem of flow attching/detaching near the top of the sail (wing tip) due to waves. It could just happen that a winglet would guide the vortex and help the flow remain attached all the way to the top when the sail moves due to waves. I really don't know and my guess is that even an experienced aerodynamics specialist will ask for wind tunnel tests before giving a final answer.

I think Luiz has hit on the biggest problem when it comes to winglets on sails or foils on sailboats. We are not operating in

smooth flow

all the time like an airplane is. With the up-down motion of a sailboat going through waves, there is a side loading on the winglet, from both sides, as it goes up and down, and I think that constant change of flow direction will make them quite a bit less efficient than on an airplane wing.

It may just increase drag without any real increase in lift.

Jake, i am not sure you can trust a book on how to fly by John Denver!....

Ohhhhh, John Denker.....

never mind (spoken in a high pitch voice like Gilda Radner)