winch launch, rope length
P.J.B...@net.hcc.nl
A decrease in rope length has brought quite some discussions within
our soaring club.
Obviously at the end of the launch the height gained is less, but is
it significant? In the old situation the usable rope length was approx
1000 meters, now it is 850.
Thos who say that the difference is negligible claim that for the last
part of the launch the ship is in a near horizontal position, so not
much height is gained in those last 150 meters anyway.
From this seasons experience however, we have the impression that
those 500+ m release heights have become a rarity and 400 m is the
norm now. Maybe the difference is less pronounced on those days with a
10 - 15 kts headwind, but more noticeable in a no wind situation.
Since this can't be a new problem, someone out there has the answer
and can devise a mathematical sound proof for the one theory or the
other. We would be most interested.
Peter Bouman
Aeroclub Salland, The Netherlands
email : P.J.B...@net.HCC.nl
Dirk Brokken
P.J.B...@net.HCC.nl wrote:
: A decrease in rope length has brought quite some discussions within
: our soaring club.
: Obviously at the end of the launch the height gained is less, but is
: it significant? In the old situation the usable rope length was approx
: 1000 meters, now it is 850.
: Thos who say that the difference is negligible claim that for the last
: part of the launch the ship is in a near horizontal position, so not
: much height is gained in those last 150 meters anyway.
That's true, but the 'last part' starts later if your cable is longer, so
you end up higher on a longer cable...
This is not exactly a mathematically sound proof, I know.
Greetings, Dirk.
P.S. In een Thermiek van een aantal jaren (weet niet hoeveel) terug hebben wat
resultaten gestaan van metingen tijdens lierstarts. Misschien staat daar iets bij.
--
Dirk Brokken, Tel. +31 40 2473170
Eindhoven University of Technology, Fax +31 40 2447355
Faculty of Mechanical Engineering, Room Wh 1.14
P.O. Box 513, 5600 MB Eindhoven,
The Netherlands.
E-mail: di...@wfw.wtb.tue.nl
Bob May
P.J.B...@net.HCC.nl wrote:
>
> A decrease in rope length has brought quite some discussions within
> our soaring club.
> Obviously at the end of the launch the height gained is less, but is
> it significant? In the old situation the usable rope length was approx
> 1000 meters, now it is 850.
> Thos who say that the difference is negligible claim that for the last
> part of the launch the ship is in a near horizontal position, so not
> much height is gained in those last 150 meters anyway.
> those 500+ m release heights have become a rarity and 400 m is the
> norm now. Maybe the difference is less pronounced on those days with a
> 10 - 15 kts headwind, but more noticeable in a no wind situation.
>
> Since this can't be a new problem, someone out there has the answer
> and can devise a mathematical sound proof for the one theory or the
> other. We would be most interested.
>
Simple formula: longer rope = higher launch
I've tried to devise a mathmatical model of a winch launch in the past.
My conclusion was that its beyond my humble abilities. However, the
following things seem clear to me:
1. A certian length of rope will be used to accelerate the glider from a
stand still to flying speed. All other things being the same (glider,
winch, wind, rolling resistance), the length used to do this will be
independant of the total length of the rope.
2. At release, the length of cable remaining is approximately equal to
the release altitude.
3. The longer time you can be in the steep part of the climb, the higher
you can get. Since the rope is being reeled in at approximately a
constant speed, the longer the rope, the higher you go.
Bob May
Nilton Renno
Dirk Brokken wrote:
>
> P.J.B...@net.HCC.nl wrote:
>
Does anyone have suggestions for fixing a small crack in a
canopy? What kind of glue should I use? Where can I get
glue?
Thanks,
--Nilton Renno'
P.J.B...@net.hcc.nl
A decrease in rope length has brought quite some discussions within
our soaring club.
Obviously at the end of the launch the height gained is less, but is
it significant? In the old situation the usable rope length was approx
1000 meters, now it is 850.
Thos who say that the difference is negligible claim that for the last
part of the launch the ship is in a near horizontal position, so not
much height is gained in those last 150 meters anyway.
From this seasons experience however, we have the impression that
those 500+ m release heights have become a rarity and 400 m is the
norm now. Maybe the difference is less pronounced on those days with a
10 - 15 kts headwind, but more noticeable in a no wind situation.
Since this can't be a new problem, someone out there has the answer
and can devise a mathematical sound proof for the one theory or the
other. Thanks in advance, we will be most interested.
bob mackey
>Does anyone have suggestions for fixing a small crack in a
>canopy? What kind of glue should I use? Where can I get
>glue?
>
>Thanks,
> --Nilton Renno'
Small cracks can be permanently repaired with a drop of methylene
chloride solvent. It wicks into the crack, dissolves the plastic, then
disipates leaving the crack welded shut. Anyplace the solvent touches
will be fogged, so be very careful. The best method I have found is to
drill a small (1-2 mm) stop hole at the end of the crack. Then using a
syringe with a sharp needle, apply the smallest possible droplet of
solvent to the inside of the hole so that it can flow out into the
crack. Practice on some scrap material before you risk your canopy.
It's easy to make it much worse using this method if you are not
careful.
When done perfectly, the crack is almost invisible.
Note that methylene chloride is toxic. It causes liver damage, and may
increase your risk of cancer. So use the smallest possible amount, and
don't inhale it or get it on your skin. If you are at the University
of Arizona campus, try asking a chemist for a few milliliters. There
is no need to go buy a liter somewhere.
-bob mackey
bma...@ucsd.edu
Raul Blacksten
I think you will find that winch launch altitude equals 1/2 the
length of the cable, whether it is 850 or 1000 meters. So from
your 850 meter cable, a 400 to 425 meter launch is what is to
be expected.
--
***************************************************************
RAUL BLACKSTEN Wishing you green air!
Vintage Sailplane Association Archivist
ra...@earthlink.net
<http://www.earthlink.net/~raulb>
"It may not be smart or correct, but it's one of the things
which make us what we are" --Red Green, The New Red Green Show
Henrik Soderstrom
Bob May <bob...@comcat.com> wrote:
>P.J.B...@net.HCC.nl wrote:
>>
>> A decrease in rope length has brought quite some discussions within
>> our soaring club.
Don´t understand this. Why should anyone want to winch with a cable
shorter than the available length of the field ??? (am I missing
something ?)
<snip>
>
>3. The longer time you can be in the steep part of the climb, the higher
>you can get. Since the rope is being reeled in at approximately a
>constant speed, the longer the rope, the higher you go.
Or in other words: the further away from the winch you start out
the higher the launch. IMHO this is determined by the length of
the field as long as the cable is "long enough".
Cheers /Henrik
Geoff Butler
In article <4uo2bu$e...@grootstal.nijmegen.inter.nl.net>,
P.J.B...@net.HCC.nl writes
>
>A decrease in rope length has brought quite some discussions within
>our soaring club.
>it significant? In the old situation the usable rope length was approx
>1000 meters, now it is 850.
>Thos who say that the difference is negligible claim that for the last
>part of the launch the ship is in a near horizontal position, so not
>much height is gained in those last 150 meters anyway.
With a shorter cable, there are differences all the way through the
launch, not just at the top. From the perspective of the aircraft, what
matters is the force transmited by the cable and *the direction of that
force*. As a glider launches, the angle of the cable at the hook varies.
If you launch on a shorter cable, you make this angle vary more quickly,
which means that the downward component comes into play more quickly.
If you launch on a shorter cable, you are not just taking away the end
of the launch, you're scaling the whole launch down. (It's not that
simple, of course, because the forces, the aircraft, and the cable
weight don't change.) If you scale your launch down from 1000m to 850m,
that's 15%, and you can reasonably expect to lose 15% of your launch
height, so I would expect 500m launches to be reduced to 450m.
Geoff Butler
Bob May
bob mackey wrote:
>
> On Tue, 13 Aug 1996 10:16:09 -0700, Nilton Renno
> <re...@soar.atmo.arizona.edu> wrote:
>
> >Does anyone have suggestions for fixing a small crack in a
> >canopy? What kind of glue should I use? Where can I get
> >glue?
> >
> >Thanks,
> > --Nilton Renno'
>
> Small cracks can be permanently repaired with a drop of methylene
> chloride solvent. It wicks into the crack, dissolves the plastic, then
>
> Note that methylene chloride is toxic. It causes liver damage, and may
> increase your risk of cancer. So use the smallest possible amount, and
>
> don't inhale it or get it on your skin. If you are at the University
> of Arizona campus, try asking a chemist for a few milliliters. There
> is no need to go buy a liter somewhere.
>
> -bob mackey
> bma...@ucsd.edu
Peolpe who deal with plastics for a living use solvent welding as
described to glue plastics together. I'm not sure if its methylene
chloride of some other nasty chemical. At any rate, you can buy (or
maybe beg) small containers from a plastic supply house, or a sign shop,
or similar place.
Bob May
Mike I. Green
1. Stop drill the crack - I use a ~1/16 inch drill that is centered
on the end of the crack. It is important that the crack not extend
beyond the drill hole.
2. Tapp Plastic sells a kit to glue plexiglass. It consists of a
solvent in a glass bottle and a plastic bottle with a hyperdermic
needle on the end. One puts some of the solvent in the plastic
bottle and uses the hyperdermic needle to apply the solvent along
the crack. The solvent is sucked into the crack by cappilary action.
Remaining solvent is put back into the glass bottle.
Good luck,
Nilton Renno <re...@soar.atmo.arizona.edu> wrote:
>Dirk Brokken wrote:
>>
>> P.J.B...@net.HCC.nl wrote:
>>
>
>Does anyone have suggestions for fixing a small crack in a
>canopy? What kind of glue should I use? Where can I get
>glue?
>
>Thanks,
> --Nilton Renno'
--
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| Magnetic Measurements Engineering |
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Doug Haluza
On Aug 25, 1996 05:13:46 in article <Re: Crack in a canopy>, '"Mike I.
Green" <mig...@lbl.gov>' wrote:
>solvent in a glass bottle and a plastic bottle with a hyperdermic
>needle on the end. One puts some of the solvent in the plastic
>bottle and uses the hyperdermic needle
A hyperdrmic needle wouldn't be very useful since it would be used above
the skin. A hypodermic needle goes below the skin.
Doug Haluza
MMayo42013
This is one of many cases where thinking of the energy involved can be
helpful. The winch does some work reeling in the cable a certain
distance (approximately the cable length minus launch height) with a more
or less constant force. Most of that work goes into the glider's kinetic
and potential energy, i.e. speed and altitude. Some is dissipated in the
air. So if the cable is shorter the winch does proportionally less
work, and thus the glider receives less potential energy, i.e. less
altitude. Very roughly, the launch height will be proportional the the
cable length.
Jon Minhinnick
In article <4vpfhi$a...@news1.t1.usa.pipeline.com> Doug Haluza wrote :
Yes, but it does allow a very fine, precisely controlled bead of solvent
into the top of the crack. Been there, done that, for a crack in my Ka6
canopy. It worked very well, too.
-----------------------------------------------------------------
jo...@voyager.co.nz using NETcetera II (Lite)
( I want to die quietly like my grandfather, not screaming
like his passengers... )
-----------------------------------------------------------------
Chris E. Becht
Doug Haluza (dha...@nyc.pipeline.com) wrote:
: On Aug 25, 1996 05:13:46 in article <Re: Crack in a canopy>, '"Mike I.
: Green" <mig...@lbl.gov>' wrote:
:
:
: >solvent in a glass bottle and a plastic bottle with a hyperdermic
: >needle on the end. One puts some of the solvent in the plastic
: >bottle and uses the hyperdermic needle
: --
: A hyperdrmic needle wouldn't be very useful since it would be used above
: the skin. A hypodermic needle goes below the skin.
I don't know about you, but I, for one am not (willingly) sticking
a needle full of solvent through *my* skin.
--
Life is like a cow.
You get out of it what you put in. cali...@crl.com
But, umm... different somehow.