Took this pic at Lilacs last week, didn't really look at it until now, how is this pelican's wing tips?
I think this shows what a floppy head does, helps stop the flow over the top of the sail from high pressure side to low.

He's giving you the forks decrep.

There's a long expanation on why big birds (mainly) have the wing tips pointed up - its got a lot to do with moving the vortex's formed at the end of wings tips to produce a much more effective wing span as used on commercial jet airliners these days.

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decrepit said..
Took this pic at Lilacs last week, didn't really look at it until now, how is this pelican's wing tips?
I think this shows what a floppy head does, helps stop the flow over the top of the sail from high pressure side to low.

Nice pic Mike, using a the end plate effect as well...

Reminds me of another wing feature I came across in my uni days. The Alula or "Bastard Wing" which is the a birds freely moving first digit. It can be extended at low speeds to increase the angle of attack/lift and stop stall. I reckon it looks like the inspiration for the slot fin as well...

Here is a cool shot from Ron Dudley"s Bird Photography site:
www.featheredphotography.com/blog/2013/03/23/the-alula-bastard-wing-of-a-kestrel-in-flight/

Mike you may want to have a look at this..



also talks about anti-stall devices

http://www.bionik.tu-berlin.de/institut/xtutor1.htm

Great examples from nature. I get the feeling that there is still a lot of room for improvement in windsurfing sails. Maybe we need more radical ideas instead of just decades of incremental improvements. The newest three-batten sail do not really look that different from sails in the 80s.

Kites seem to have evolved a lot faster - 2 kite boards and 3 kites cover 10-40 knots of wind. Compare that to 3.7, 4.2, 4.7, 5.3, 5.7, 6.5, 7.5, 8.5 m windsurfing sails that do not cover quite the same range (and the list does not include all sizes we have, nor does it include duplicates in the same size for waves/freeride/speed).

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boardsurfr said..

Great examples from nature. I get the feeling that there is still a lot of room for improvement in windsurfing sails. Maybe we need more radical ideas instead of just decades of incremental improvements. The newest three-batten sail do not really look that different from sails in the 80s.

Kites seem to have evolved a lot faster - 2 kite boards and 3 kites cover 10-40 knots of wind. Compare that to 3.7, 4.2, 4.7, 5.3, 5.7, 6.5, 7.5, 8.5 m windsurfing sails that do not cover quite the same range (and the list does not include all sizes we have, nor does it include duplicates in the same size for waves/freeride/speed).

I think you will find that most birds sit out 40 knots of wind too!

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boardsurfr said..

Great examples from nature.

hmm... I'd like to see a bird to 40-50 kn (80-100 kph), without using gravity assist.

The peregrine falcon can do it :) en.wikipedia.org/wiki/List_of_birds_by_flight_speed
105-110kmh horizontal speed...and 389kmh in a hunting dive :P

&

"The greatest self-powered horizontal flight speed is achieved by the White-throated needletail, capable of such speeds as 169 km/h (105 mph), typically during mating rituals."

Speedsailing needs cheerleaders perhaps?

The common Black Duck routinely flies at up to 100 kph! 30 knots headwinds are also routinely dealt with.

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sailquik said..

The common Black Duck routinely flies at up to 100 kph! 30 knots headwinds are also routinely dealt with.

so you aim slightly ahead?

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Windxtasy said..

boardsurfr said..



Great examples from nature. I get the feeling that there is still a lot of room for improvement in windsurfing sails. Maybe we need more radical ideas instead of just decades of incremental improvements. The newest three-batten sail do not really look that different from sails in the 80s.



Kites seem to have evolved a lot faster - 2 kite boards and 3 kites cover 10-40 knots of wind. Compare that to 3.7, 4.2, 4.7, 5.3, 5.7, 6.5, 7.5, 8.5 m windsurfing sails that do not cover quite the same range (and the list does not include all sizes we have, nor does it include duplicates in the same size for waves/freeride/speed).

I think you will find that most birds sit out 40 knots of wind too!

Select to expand quote

boardsurfr said..
Great examples from nature. I get the feeling that there is still a lot of room for improvement in windsurfing sails. Maybe we need more radical ideas instead of just decades of incremental improvements. The newest three-batten sail do not really look that different from sails in the 80s.

Kites seem to have evolved a lot faster - 2 kite boards and 3 kites cover 10-40 knots of wind. Compare that to 3.7, 4.2, 4.7, 5.3, 5.7, 6.5, 7.5, 8.5 m windsurfing sails that do not cover quite the same range (and the list does not include all sizes we have, nor does it include duplicates in the same size for waves/freeride/speed).

This certainly would be an answer to the thread " what can be done to put windsurfing back on fire" ..something in that order..I guess for now manufacturers are still groping with the lightest materials and better looking sails rather than improving say airflow..

A recent photo from Burrum Heads Windfest:

...the ultimate wingsail.

So I might have just been a little hasty in my bird question... last I looked, most birds do 50-80kph (30-50mph) in level flight... indeed there is lots of complexity in measuring non-wind or gravity assisted flight.

There doesn't seem to be many white papers describing the technique for measuring horizontal bird flight...most "records" are implemented by tagging a bird, then measuring start and finish times, over a known distance (sound familiar?).


In any case, interesting to see the wing-profile of the fastest birds - most of which are quite high aspect, with a raked wing-tip, and not a lot of splay of the tip-feathers.

For a really cool video of a gravity assist: