Which bird thermals the best?

I hear Gill Spreakley is pretty good!

on my last flight in the Cherokee there were a bunch of seagulls
flying around. they thermal but they suck at it. the were never in
the core and are a pain to gaggle with as they are just a huge blob of
birds. I was at some times surrounded above and below and on all
sides by hundreds of birds. one thing they are good at is getting out
of the way

On Tue, 16 Nov 2010 03:26:01 -0800, Wiktor Moskwa wrote:


I would avoid White Storks, especially on weak days - they're great
soarers but they're low wing loading let's them use thermals
that would just reduce glider's descent rate a bit.

According to Henk Tennekes ("The simple science of flight") a bird can't
make a living unless its min.sink speed is 1 m/s or less. I'd think that
land birds are unlikely to be much better than that sinply because the
amount of wing they'd need would make life awkward in trees, etc.

Our gliders can certainly outperform some soaring birds. Some years ago
on an almost flat calm evening I was sitting in a very weak thermal,
flying an SZD 51-1 Junior slowly in fairly wide circles and climbing at
half a knot or less, but hey, it was a nice evening and the drift wasn't
taking me anywhere, so I was just enjoying my last flight of the day.
After a while I was joined by a pair of black-backed gulls. They flew
several turns without gaining on me and then left, coming back 5 minutes
later and somewhat lower. This time they flew one turn and exited, not to
be seen again. I could almost hear one of them saying as they flew off
"See, I told you that thermal was too weak last time".


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Birds I have thermalled with -

Cape Griffon (White Backed Vultures) thermal very well, but you have to
be careful there is a "vulture restaurant" near the Drakensberg Club
outside Underberg. (Natal Province - South Africa) So sometimes you join
them in a thermal, only to discover they have sought out the descending
air so they can get on the ground for grub. They are gregarious and join
the gliders quite happily. Occasionally you get one clown who thermals
the wrong way and causes chaos.

Bearded vulture - this is a huge bird, which I have only had the
priviledge of flying with once as they don't like gliders and get
aggressive - Based on a sample of one Two up in a K13, and trying to
stay up in the only thermal in the sky trickling off a stony conical
hill. Desperately clinging to about .5kt we got thrashed in the Grob 103
Twin Astir - The Cape Griffon with us were also left in his dust. One
assumes that the massive wings help. I was interested to see the camber
on the wings changing as the bird optimised the smallest variations in
lift. They eat the marrow in bones, so meal times consist of descend to
a carcass, lift off with a heavy ungainly load and climb high - then
drop the bone onto rocks to break it - descend to eat - fly back to
carcase. Repeat. Clearly those that can thermal well get to eat best.

Tawny Eagle on the Platberg ridge also out climbed me - this time in a
K13 - maybe it is the way I fly. We met doing the 180 turn at the end of
one beat. The Eagle turned well inside us and was clearly able to stay
in a very tight , very strong core of lift rising up from a gulley.

Gymnogene - flew a couple of turns with me in a Bergfalke II-55. It was
late afternoon, and I think the motivation was curiosity on the way to
it's roost for the night. I got carefully inspected and then left - at
about the same height. Sample of one does not say much, but despite the
wing aspect ration he was not climbing well. Also - This is the only
solo bird I have had join me in a thermal and turn opposite.

Yellow Billed thermal very well. They have often helped me over the
Vredefort dome - generally marking good lift.Problem is they are so
agile they can use lift which even the Cirrus can't turn in...

European swifts are often to be seen right in the core of strong
thermals at high altitude. The seem to be able to combine hawking
insects and thermalling with relatively little flapping in between the
aerial gymnastics. They really get into the core of the thermal.

Never flown with them but the Bateleur Eagles seem to thermal very well
too.



On 2010/11/15 1:59 PM, Scott Alexander wrote:
So in a recent conversation with a greatly experienced soaring pilot,
I was told that Buzzard's have terrible thermaling skills. I tend to
agree with this as it sure seems Buzzards don't get into the core and
stay there. The lesson learned was don't let Turkey Buzzard show you
where the core is, just let them lead you to the thermal.

I thought it would be interesting to ask you good people if anyone has
any knowledge on these issues. Does anyone know which broad winged
birds have better or worse centering techniques that you can use to
your advantage?

SA

--
Bruce Greeff
T59D #1771 & Std Cirrus #57

I came across another contender this week for best thermalling bird,
although not really a bird... more an extinct flying reptile.
Apparently the Quetzalcoatlus (largest of the pterosaurs) might have
been quite the efficient soarer, with a 10m+ wingspan. Here's the
article: http://www.plosone.org/article/info%...l.pone.0013982.
Figure 2 is the most relevant for this discussion, with a nice two-by-
two diagram mapping bird and pterosaur species based on their aspect
ratios and wing loadings.

The theorized launch method was potentially quite unique as well
(quadrapedal launch), although not likely to replace the aerotow or
winch launch. There's a video recreation with this story:
http://news.sciencemag.org/scienceno...rs.html?ref=hp

Coincidentally, there even happens to be a photographic depiction of
an attempt to thermal with Quetzalcoatlus (http://tv.sky.com/3d-
attenborough-doc-to-debut-this-xmas). I think by the look on Sir
David Attenborough's face he must have been wishing the giant reptile
were FLARM equipped.