On Jun 20, 6:55*am, BruceGreeff wrote:
We have had excellent results from a mirage F1 drag chute.

Light, low drag when closed, very fast stable opening.
Tough as one could hope for - we get ~2500 launches on rough stony earth
before condition demands replacement. Unfortunately the surplus stock we
obtained when the F1s were retired is now used up. Soon we will have to
get a new chute.

Much smaller solid canvas chutes have worse drag , shaking and opening
on launch behaviour.

Drag is influenced by shape and material/surface.

On 2011/06/20 07:58 AM, Markus Graeber wrote:









On Jun 19, 8:17 pm, Tony *wrote:
We (Greater Boston Soaring Club) had our first Spectra "glider flinging"
session today and were surprised that we saw no altitude improvement
after switching from steel cable. The winds were not favorable and our
heights may improve in time. .... But that's not the question.

We have the option of launching from either asphalt or turf. From a
Spectra wear point of view, which would be preferred?

Tony V. LS6-b "6N"

Besides anything else that has been said one core component and its
effect on launch height that is almost always overlooked is the
parachute. The drag a big, unwieldy parachute creates even when it is
folded during the launch can have a much bigger effect than
differences in cable weight etc. Just using a well designed parachute
with a low profile when folded can easily get you a couple of hundered
feet compared to some drag monster commandeered from some other
unrelated application...

Markus Graeber

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

It's certainly true parachutes can hurt the height achieved.
Fortunately, there are alternatives.

Traditionally, parachutes were there to prevent steel cable from
kinking and tangling - Spectra/Dyneema rarely does either. Some clubs
have eliminated the parachute and just let the soft rope fall. Others
have used ~20" diameter plastic drag disks cut from the bottoms of
plastic barrels which are far cheaper and tend to protect the weak
link hardware. The drag disk can also eliminate the need to remove
and fold up an expensive parachute for the rope retrieve - just let
the disk drag behind the retrieve car.

Spectra/Dyneema rope forces a lot of changes in winches and
operational procedures.

Bill D

Spectra/Dyneema requires far less drag in the system than steel.