Wing tie-down kit

On Aug 5, 7:29*pm, raulb wrote:

I bought 2 back belts with velcro closing (but without the shoulder
straps) and a couple of textile motorcycle tiedown loops (not the
ratchet straps, but what you put on the bike to protect it from the
metal hooks) and had *2 excellent tiedown cuffs for less than $25
lot. *For the nervous, they can be stitched.


In the 35 years I have been in this sport I have seen 3 ships upside
down on the ramp................so when I leave the ship tied out I
make sure its adequately secured. The trailing edge cusp distributes
the load and prevents cauging flaps or ailerons. The force is all
forward and then down over the leading edge and ratchet'd down against
wing stands. I also chock both wheels.
JJ

I am sorry JJ. I mis-read the posts. I didn't realize you were
selling these things until after I posted. I thought I was thumbing
my nose at someone else.

On Aug 6, 10:25*am, raulb wrote:
I am sorryJJ. *I mis-read the posts. *I didn't realize you were
selling these things until after I posted. *I thought I was thumbing
my nose at someone else.

I've been using JJ's tie-down kit with my ASW27 successfully. The
ASW27 does not have otherwise any acceptable method for tie down which
I know off. JJ's tie downs can go over the aileron or flaps without
damaging them since the force is mostly all forward. I use them over
the aileron/flap juncture. They are small enough to be carried easily
in most gliders. I also carry JJ's wing tip detachable wheel, another
great JJ product, for aeroretrieves from dirt strips without wing
runner. Both kits can be carried easily in my 27 compartment.
I recently landed at Minden and used the tie downs without wing
stands. The wind was calm when I landed but started blowing at dawn
and was gusting over 30 when I arrived at the airport. It even blew
the wind sock away, but the tie downs held nicely with no harm to the
wings. JJ's tie down kit passed the test :-)

Both products are available from Williams Soaring Center:
http://store.williamssoaring.com/Mer...tegory_Code=SP

Ramy

On Sep 12, 2:13*pm, Ramy wrote:
On Aug 6, 10:25*am, raulb wrote:

I am sorryJJ. *I mis-read the posts. *I didn't realize you were
selling these things until after I posted. *I thought I was thumbing
my nose at someone else.

I've been using JJ's tie-down kit with my ASW27 successfully. The
ASW27 does not have otherwise any acceptable method for tie down which
I know off. JJ's tie downs can go over the aileron or flaps without
damaging them since the force is mostly all forward.

Ramy

I thread nylon webbing around the divebrake pivot on the -27 (the
steel tube that runs between the foreward and aft walls of the box
about 1.5 inches down inside the divebrake box itself - not the tube
that sticks up and holds the panels) then back down over the leading
edge of the wing to whatever I'm tying to - no fabrication required.
The same principle applies as for JJ's rig only more so since the
webbing comes straight up out of the box, makes a 90-degree turn to
follow the top surface of the wing to the leading edge and then
straight down to the ground. The force on the divebrake pivot would be
straight up if the tiedown comes under tension, but I think most of
the force would be tranmitted to the top surface of the wing from
surface fricton leaving the residual loads on the pivot relatively
low. I also put wingstands under both wings so I am not sinching the
dihedral out of my wings.

I'm told the factory doesn't recommend tying to the divebrakes, but I
suspect they were thinking about wrapping rope around the tubes that
stick up when the brakes are deployed - pulling on those would put a
lot of torque on the pivot.

JJ's design looks good (thanks JJ!) as long as they are ensured of
pulling the trailing edge forward along the chord - on a control
surface I'd worry that it might deflect upward
under tension and hurt something.

9B

The ideal location for the trailing edge cuff is over the trailing
edge of the wing at a location where no control surface is located, as
in a standard class ship. On a 15 meter bird like the 27, the whole
trailing edge is either flap or aileron. I have used the trailing edge
cuff where the flap and aileron meet for years on my Nimbus-3 and LS-6
without causing any control surface damage. Any slight upward pressure
is restrained in the flap and aileron push-rods which are loaded in
tension as upward forces are trying to raise both control surfaces
together.

I would however, reconsider pulling upward on the spoiler push-rod
which is quite strong in tension, but quite weak when bending loads
are applied.
JJ

I'm told the factory doesn't recommend tying to the divebrakes, but I
suspect they were thinking about wrapping rope around the tubes that
stick up when the brakes are deployed - pulling on those would put a
lot of torque on the pivot.

JJ's design looks good (thanks JJ!) as long as they are ensured of
pulling the trailing edge forward along the chord - on a control
surface I'd worry that it might deflect upward
under tension and hurt something.

9B

On Sep 14, 8:05*am, JJ Sinclair wrote:
The ideal location for the trailing edge cuff is over the trailing
edge of the wing at a location where no control surface is located, as
in a standard class ship. On a 15 meter bird like the 27, the whole
trailing edge is either flap or aileron. I have used the trailing edge
cuff where the flap and aileron meet for years on my Nimbus-3 and LS-6
without causing any control surface damage. Any slight upward pressure
is restrained in the flap and aileron push-rods which are loaded in
tension as upward forces are trying to raise both control surfaces
together.

*I would however, reconsider pulling upward on the spoiler push-rod
which is quite strong in tension, but quite weak when bending loads
are applied.
JJ

Hey JJ,

I don't tie to the pushrod. I agree, it is is too long and not likely
stong in bending load. Instead I thread the webbing around the 1.5-
inch long T that is the bottom of the whole pivot for the divebrake.
There is one inboard and one outboard on each divebrake - I tend to
tie to the outboard one. They are essentially the bottom corners of
the whole parallelogram that allows each divebrake to swing up out of
the box. Since they run chordwise inside the box and are anchored fore
and aft by 3/4" steel bearings set in carbon fiber next to the spar it
would seem to me to be one of the more stout parts on the whole wing
structure - certainly at least as strong as control surface hinges.
But since I have not cut into my wing to see how it's really put
together I can't be absolutely sure which is why I was asking around
from people who maybe have seen inside a -27 wing.

If it's still not totally clear which part I'm talking about I'll take
a picture when I get home. I've never had a problem with doing it this
way. On the other hand, I've never seen any tiedown actually rip off
of the airplane even though I've seen some pretty sketchy methods - so
lack of a catastrophe doesn't prove much.

I guess you can get away with putting the JJ rig at the flap/divebrake
intersection as long as there isn't a lot of play in the control
circuit so everything stays snug and aligned. But here's a thought
experiment - I cup the cuff over the trailing edge and lay the web
across the top surface of the wing, then I squat in front of my glider
and yank on the strap from a low angle as hard as I can to simulate a
big wind gust trying to lift my glider up. Those -27 control surfaces
seem so thin and delicate - it makes me nervous to think about it. But
I don't glue gliders back together for a living so maybe I'm being too
squeamish.

9B

On Sep 14, 5:11*pm, wrote:
On Sep 14, 8:05*am, JJ Sinclair wrote:

The ideal location for the trailing edge cuff is over the trailing
edge of the wing at a location where no control surface is located, as
in a standard class ship. On a 15 meter bird like the 27, the whole
trailing edge is either flap or aileron. I have used the trailing edge
cuff where the flap and aileron meet for years on my Nimbus-3 and LS-6
without causing any control surface damage. Any slight upward pressure
is restrained in the flap and aileron push-rods which are loaded in
tension as upward forces are trying to raise both control surfaces
together.

*I would however, reconsider pulling upward on the spoiler push-rod
which is quite strong in tension, but quite weak when bending loads
are applied.
JJ

Hey JJ,

I don't tie to the pushrod. I agree, it is is too long and not likely
stong in bending load. *Instead I thread the webbing around the 1.5-
inch long T that is the bottom of the whole pivot for the divebrake.
There is one inboard and one outboard on each divebrake - I tend to
tie to the outboard one. They are essentially the bottom corners of
the whole parallelogram that allows each divebrake to swing up out of
the box. Since they run chordwise inside the box and are anchored fore
and aft by 3/4" steel bearings set in carbon fiber next to the spar it
would seem to me to be one of the more stout parts on the whole wing
structure - certainly at least as strong as control surface hinges.
But since I have not cut into my wing to see how it's really put
together I can't be absolutely sure which is why I was asking around
from people who maybe have seen inside a -27 wing.

If it's still not totally clear which part I'm talking about I'll take
a picture when I get home. I've never had a problem with doing it this
way. On the other hand, I've never seen any tiedown actually rip off
of the airplane even though I've seen some pretty sketchy methods - so
lack of a catastrophe doesn't prove much.
Schleicher wisely recommends against using the spoilers as a tie-down
location because you are applying high loads to a butt weld which is
weak under side loads. The same loads will be present when using the
short drive arm to attach a web strap, although admittedly not as high
as attaching to the vertical arms. If you bend anthing in there, your
spoilers won't close and lock completery.............guess how I know
this to be true?

The loads applied using the trailing edge cuff are 90% forward and 10%
upward. As demonstrated by 20 years in use, the control hinges are
plenty strong enough to withstand the forward load and the control
mechanism is plenty strong enough to take the 10% upward load. The
cuff is well padded and bent to an angle that grips the sides before
the trailing edge seats fully.

What we're talking about here is the lesser of two evils while still
providing an acceptable solution to tying the ship down when
necessary.
JJ


I guess you can get away with putting the JJ rig at the flap/divebrake
intersection as long as there isn't a lot of play in the control
circuit so everything stays snug and aligned. But here's a thought
experiment - *I cup the cuff over the trailing edge and lay the web
across the top surface of the wing, then I squat in front of my glider
and yank on the strap from a low angle as hard as I can to simulate a
big wind gust trying to lift my glider up. Those -27 control surfaces
seem so thin and delicate - it makes me nervous to think about it. But
I don't glue gliders back together for a living so maybe I'm being too
squeamish.

9B