Thermals and free energy

[jack.h...@gmail.com]

World gliding championships are taking place in Texas.

The fastest flight on Monday was at 164.5 km/hr over a 668 kilometres route.

(415 miles at average of 102 mph)

Jack

[Len]

That's quick. What was the mean altitude?

Len

[jack.h...@gmail.com]

Launch site Uvalde, Texas.  Cloud base about 9,000 or 10,000 feet above surface so operating height band between say 5,000 feet and cloud base.

The technique is to use only the strongest thermals and not waste undue time searching for and finding  the core.  Teams these days fly in pairs so, in effect, increasing the search area.

As the rate of climb falls off, they leave the thermal, dive at great speed, perhaps 140 mph, to the next one.  Flying so fast is not optimum for glide ratio, but is worthwhile if the next climb is expected to be very strong.  Computers enable the best speed to be flown to arrive at the next thermal lower than it would be at best glide, but that is more than made up for by rapid climb.  Rates of climb can be as much as 1,500 feet per minute.

This requires great skill and concentration.  The smallest error can mean ten places down the scoring list.

I tried to do this sort of gliding many years ago (in much lower performance gliders) but was never particularly successful.

Jack

[jack.h...@gmail.com]

Extract from forecast for today's race

Skies will remain mostly clear or isolated cu in the pre-start task area with more abundant scattered cu developing to the north and east.

Models show thunderstorms firing off 6-7pm CDT east of Uvalde in the San Antonio Metroplex area as cells drift or form toward south from the Hill Country. Considerable cu cover eastern half of Hill Country …N and NE of Uvalde… cu bases 11,000-13,000ft MSL.

The boys and the girls (yes, females compete on equal terms) should have a good day and achieve some very fast speeds.

Jack

[Len]

Thanks. That was very interesting Jack.

I often wondered about the best technique for flying from thermal to thermal.

Never got that far with my rather rudimentary gliding experience first through the air cadets at RAF Swanton Morely in Norfolk, and thereafter with the Imperial College gliding club at Lasham in Hampshire.

Len

[jack.h...@gmail.com]

Even more to it than that Len.  Pilots do not necessarily stop and climb in every thermal but 'dolphin' and just pull up through patches of lift until they find the very best and only then stop and circle.  But the risk is getting too low and having to accept a weaker-than-ideal thermal or, even worse, not finding a thermal at all.  That seemed to be my style in competitions: I'd progress along the route at great speed, but then over-do things and have to land:-(

I, too, did my first gliding solo at Swanton Morley with the Air Cadets in May 1955.

Jack

[Len]

I did my 3 solos in Oct 1967 in the good old Kirby Cadet Mk 3.

Len

Wembury

[jack.h...@gmail.com]

Perfect gliding sky.

I copied (a bit naughty) for quicker access.

But if you wish, you can see the original here.

https://wgc2024uvalde.com/wp-content/uploads/2021/01/cockpit-view.jpg

The little piece of string over the canopy provides a visual reference that you are flying through the aid without slip or skid (which would increase drag).

Jack

[jack.h...@gmail.com]

Typical task, although usually fewer turnpoints.

GPS and loggers today.  Computer programs produce results in minutes. 

In the 'good old days' photographic evidence was needed.  I would often be scorer (not many understood the complexities) and work away with my slide rule until late in the evening.   I was kept well supplied with liquid 'inducements' from the competitors so the accuracy of my slide rules operations tended to deteriorate (in a favourable direction!) as the evening wore on:-)

Jack