From: HAHLLUND@finabo.abo.fi (Hans Ahllund Inf)
Newsgroups: rec.aviation.soaring
Subject: Re:Scratching
Date: 4 Oct 92 17:24:22 GMT
Organization: Abo Akademi University, Finland
X-News-Reader: VMS NEWS 1.23

Hello Fellow glider-pilots...

I would like to add my own opinions in your scratching diskussion...
  Sorry about the frustrating >> quoting..

>In addition to the existing thermalling thread,
>does anyone have tips about thermalling when
>at ,say, 1000 feet (and sweating)?

The number one rule if in "scratching" is :
  - Dont't sweat. Try to fly as normally as possible even if you are low.
                  Take a look at your flying sometimes when you get into
                  tricky situations. You often tend to get over-excited,
                  which leads to increased tension in your muscles.
                  That is, you start to do more control-inputs than 
                  necessary, and that will make you tired, and your
                  performance decreases.

>Being blown downwind takes on added significance
>while trying to keep the field in sight.
   
 This is true if you make the mistake of searching for thermals downwind.
 When flying cross-country this makes no difference because there will always
 be new fields downwind. So, you can circle in even zero lift and wait for
 better conditions.

>Thermals down below 1000' tend to be smaller and more turbulent than they 
> are at higher altitudes.  

 The first thing you have to realise is that thermals below a certain 
 altitude, depending on the day , tend to be Bubble-shaped.
 Because of this, you first have to find out in wich part of the bubble
 you are, or , if you are in the vicinity of several smaller bubbles.
 
 If you encounter weak lift that has very little sink when you enter, and
 it feels like you would be flying on a ball when trying to center, then
 you are on top of a bubble coming up. The thing is to keep centering and
 after a while you will slide into the core of the bubble.

 If you fly into the bubble from the middle, it will feel almost like you
 have encountered a "thermal-pipe" (formed by a cloud). This is the easiest
 option. Just bank hard and climb. Do not change thermal when the lift
 decreases a bit. The decrease only indicates that you have reached the top
 of the bubble. At this point lift is equal to the speed of the bubble going
 upwards.
 
 The most difficult option is if you fly into the botton of the bubble.
 There will be strong sink and a sharp, strong and tight peak of lift.
 If you have enough speed you could try pulling up and getting in to the
 bubble from below, but this rarely works. 
 
 If you are in an area of several small bubbles, just circle with farely
 moderate bank, and use a bit of dolphining between bubbles.

>One of the harder parts of scratching is judging whether a bump you feel
> is a bona-fide thermal that you can stay in or a "teaser" before you
> initiate a turn. 

  Scratching is quite easy when you get the hang of it.
  Just fly straight until you encounter lift , or sink.
  The 2 second rule before banking is quite good, but 
  when you start banking it will have to be in the right
  direction. This essential because you just have to do
  one turn in the wrong direction and you are down.....
  Try to feel where the thermal is. Fly into the direction
  where the thermal lifts your wing. Or into the direction
  that the sink lowers your wing if you are in sink only.
  If you get fooled by a teaser. That is, bank , and then 
  find nothing, bank immediately in the opposite direction.
  You have to be very aggresseive in strong conditions, but
  quite careful in weak. 
  When you center, dont't make the mistake of centering twice
  during the same circle. Center once, see what heappens, the
  center again at the next circle.
  And don't fall asleep, if the lift disappears , as it often 
  does , get into straight flight and find another bubble.
  
The difficulty of getting up when you are low depends to a great deal
on the relative "lowness". I mean that if you fly with a 400 meter
cloudbase, you don't conscider yourself low until you are at 200 meters.
But on a 2000 meter cloudbase day , even 800 meters seems very low...
When flying cross-country I switch to the "scratching mode"  if I get 
lower than 50 % of the cloudbase. Then I most often fly  downwind
to increase range and possibilities of hitting a thermal..

  Keep practising, it's the only way to ever learn soaring. 

 Sorry if I have bored you !!!!

                                     Hans Ahllund 
                                     Comp.Sci.Student
                                     Glider&Tow Pilot
                                     ]bo Akademi University
                                     Finland.
Newsgroups: rec.aviation.soaring