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Old Dec 15, 2010, 11:59 AM
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Auburn, WA
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Sea gull dynamic soaring?

I was driving the 520 bridge in Seattle yesterday. I'm used to seeing seagulls traversing the bridge by cruising along the windward side of the bridge. But yesterday I saw a gull cross from the windward to the leeward side then dive down, fly along the waterline, then fly back up about 40' straight above the bridge, then dive back down on the leeward side, fly along the water, then fly back up 40' above the bridge and continued to do this in succession.

Am I right in presuming this was in effect dynamic soaring or is there some other phenomenon that might allow the bird to maintain energy/lift on the leeward side like that?
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Old Dec 15, 2010, 01:29 PM
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Daemon's Avatar
Lakewood, Colorado
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Gulls are master fliers. It's certainly very possible.

ian
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Old Dec 16, 2010, 05:10 PM
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Dr. Ferdinand Hendriks wrote his disertation at UCLA on Gulls DSing. Back in the early 70's. YOu might be able to find a copy of his paper someplace. Pretty technical.

JDK
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Old Dec 17, 2010, 01:27 AM
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Interesting, I google'd his name and came up with another thread with a presentation of his. Interestingly he also mentions "gust soaring" as a viable technique for list. I wonder if this is why I see so many gulls flying high altitudes in the midst of big storms.
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Old Dec 17, 2010, 01:31 AM
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Interesting link if anyone is as interested in this as I am at the moment...

http://www.eounion.org/pdf/v21/AS-2-1-Pennycuick.pdf
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Old Dec 17, 2010, 01:50 PM
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Yes, that's a very interesting article. His diagram of a sharp tipped wave with a separation
bubble on the lee side, represents the classic DS groove. The discussion of what
happens with a sudden "gust" from directly below, in the context of a relatively
fixed glide ratio is also useful to understanding why the albatross and our DS gliders gain
more forward airspeed than the gust speed, as long as the aircraft turns to
orients itself so the "gust" acts from directly below.

ian
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Old Dec 17, 2010, 05:02 PM
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Joined Mar 2005
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The most amazing thing I ever seen was 2 crows sitting on the side of a round about. It was blowing about 35knots and because the land was cleared the air must have been pretty laminar.
1 crow was waiting for cars to go buy then jumping in the still air spreading his wings then would get hit by 35 knots and flare up about 5 or 6 feet then tuck his wings and land on the same spot. He did it to the 3 cars in front of me, I assume my car and. The one behind me. His mate sitting next to him was just standing and watching him. I assume he was scoring him on height and style.
It was very cool.
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Old Dec 17, 2010, 07:23 PM
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Looking for albatross vids and stumbled on this one. Pretty amazing to see
a bird that big flying underwater.
Diving albatross Freediving (1 min 58 sec)


Various vids of other underwater birds show that some fly, and some paddle.

ian
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Old Dec 18, 2010, 02:49 AM
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The first I ever heard of DS. was a book called, "The Wandering Albatross" by William Jameson. It was published in the late fifties by Morrow and later as a paperback by Doubleday Anchor books. I read it after a very positive review in The Scientific American.

The next time I heard af DS was when I joined my present RC club and one of the glider guys told me DS'ers were hitting speeds like 160 mph! I was a bit skeptical, but read up on it. Where it's gone since then is more than a bit mind blowing.

Pete
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Old Dec 19, 2010, 01:13 AM
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I had a good experience today of having a peregrine pulling laps with me, not just one or two, but 3, 4 or 5 in a row before bailing for a moment or two while I did a couple, then back in again. It did it more than once too, I landed to change planes and it came back to do some more. I've had them follow through the shear at the top of a table shape slope I fly, but nothing like this before!

What's more, it looked like it knew what it was doing, diving down low to miss the turblent shear when I struggled to get back through it.

While they certainly weren't mind blowing speeds, it was really cool to be swapping paint/feathers with the bird often a wingspan or two away during the laps. I'm pretty pi$$ed that I didn't take me keychain camera with me - I was tempted but figured I wouldn't see anything worthwhile. Winds are predicted to be good again tomorrow, so watch this space.

Steve
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Old Dec 19, 2010, 02:46 AM
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There's a national geographic video on YouTube where they clocked a peregrine at 242mph with on-board (so to speak) instrumentation. Found it on Google but weirdly enough the URL wouldn't stay put long enough to grab it.

Hmm... I think I got the URL:

High-Velocity Falcon (2 min 59 sec)


It was in a stoop with it's wings completely folded, but at that speed it was still able to open it's wings to regain normal flight.

Amazing to fly with a bird like that. I hope you get some.videos of it.

Pete
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Old Dec 19, 2010, 08:16 AM
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The pdf above just dramatically altered my concept of how DS works for RC gliders:
Quote:
In the example above, the albatross flying into a horizontal gust of 1 m s 1 would get nearly 14 times as much energy by rolling belly-towind, as it would get if it received the same gust from directly ahead, with its wings level.
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