YES! This is it! The thermal flattenning makes good sense. It may be
some kind of wave.. Nearest mountain to me is occationally up-wind, but
75 miles away , Mt. Katahdin (5,100'). This was a very windy day
(30kts at altitude) and they where from the mountains... but that
phenomina was too weak to ride 1-2kts coming in, 5kt peak, then boom
-8kts

As for the circle tightness... 12m Silent aint no ballasted speed
deamon. It's a light (290kg gross) ship with a 33kt stall speed and
1.36kt min-sink. It's really a Sunday thermal machine. It's also a
self launch and I have it all to myself, so I've been flying quite a
bit lately. I have a bit over 15 soaring hours just this spring (35hrs
TT-G). I've gotten pretty good at keeping it up on marginal days. I
commonly ride the stall buffet (Vs+10kts) in a 60 degree bank satisfied
with 1kt average lift just to stay up a little longer. I did 6.1hrs
last week on a day that the vario never saw anything over 4kts and
typically 1-2kts.

This kind of weather sucks for x-country cause there's rarely enough
strong lift to know I'll get home. On stronger days I have done some
"near" x-country... Headed to two nearby airport 15miles away in a
right triangle from home. But those where really just "circle-up and
slide-on-home deals", very few real risks. Highest climb: 7,000' from
a 1,500' shut-down. But I had to really milk the last 1,500'.

For a newby... I think I'm holding my own. Thank you all for the good
info. I read it all and I'll look for the book.

-Bruce

Bill Daniels wrote:
"phil collin" wrote in message
...
wrote:
I can definately identify with the horizontal turbulence phenomina that
this discusses. But what I'm talking about is not the same. I've
approached this stable at min-sink and identified lift with the
altemeter. Then the vario rises quickly for about 2 second, then the
bottom drops out and I'm in heavy sink


The shear zone near the edges of thermals will create horizontal vorticies.
If you fly through one of these shear vortices at right angles, and the
vortex is rotating the top away from your flight path, you will experience
what you described.

First, you will experience smoothly increasing lift, then as you pass
through the vortex core, a sharp transition to strong sink which will
smoothly decrease. These are commonly encountered when working small,
strong thermal cores since you are spending a lot of time in the shear zone.
A low boyancy/shear ratio can also create them. Just keep circling and
watch your averager.

Bill Daniels