The strength of all the strings used during soundings must not exceed 23 kp
(230 N). Knots in the strings weaken the strength to the minimum of 45 % of the original
string strength. This results in a string strength of 10 kp (100 N) which is
sucient for
soundings with Radiosonde RS41.
CAUTION!
Attach all optional sounding accessories next to the balloon, otherwise they disturb the
measuring environment of the radiosonde and no proper temperature and humidity
measurements can be made.
Visit www.vaisala.com/RS41 to watch short videos on how to make a hanger board and
how to attach the unwinder to the hanger board, and how to attach the unwinder to the
parachute.
3.3.1 Totex Parachute 5710-5
The recommended parachute is Totex type 5710-5 (Vaisala code 15045). See option 1 in
Figure 4 (page 20).
Totex parachute 5710-5 has an elastic ribbon loop below the spreader. Attach the unwinder
to the loop by pushing the hook out the other side in the same fashion as with the folded
balloon neck.
3.3.2
Non-Totex Parachute
If you are using a parachute that has no firm objects to prevent the unwinder from twisting,
use a hanger board. The hanger board provides more stability during the sounding. See
option 3 in Figure 4 (page 20).
3.3.2.1 Making a Hanger Board
The string used with the hanger board must have a diameter of > 1.5 mm and the strength
must be 250 … 350 N.
See the steps below for instructions on how to make a hanger board out of the radiosonde
cardboard package. See also the video in www.vaisala.com/RS41.
To make the hanger board, you need the following items:
• Radiosonde handling box cardboard package
• Scissors
• Some string
1. Cut the radiosonde cardboard package to one whole piece that is big enough to make a
hanger board.
2. Make one hole at one end of the hanger board, four holes at the other. Make the four
holes so that two holes are on top of each other.
Chapter 3 – Operation
21
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