Hartley, I reread your post and perhaps I did not address your concerns
completely. My installation was simple. One hole in the fiberglass seat pan
as high up as practical. I used a very short large AN bolt (~5/16th). This
size bolt was gross overkill strength and weight wise but I did not have a
suitable bushing. On the back side I used an AN 970 large area washer and a
NA365 nut. On the front was the head of the bolt and the triangular steel
belt fitting. When this is good and tight the shear and bearing load on the
seat pan is spread out to the big washer size area. I'm sure in my case a
good load was transferred to the pan, Not much way to guess the value. Too
many variables.
Months later when the insurance company sold the glider I offered to help
and got a chance to examine the glider. I saw no localized damage at the
strap attach point.
Hope this helps,
Ed Byars





"Ed Byars" wrote in message
hlink.net...
Hi Hartley,
The crotch strap remained intact after doing it's job. I'm just lucky that
no serious permanent damage was done to my sensitive genitals.
I like the ideas presented relative to a six point arrangement. This sure
sounds safer, but any sensible arrangement would be virtually impossible
to
get by the LBA/FAA.
It's a shame that it's not likely that any competent person or group
would/will develop and offer for sale such a glider system. Our legal
system
just would not allow it. Maybe such a system designed for another more
numerous vehicle, auto probably, might be available for Experimental
licensed gliders. From an overall safety standpoint it may be just as
important to assure that any belting system is quickly free of the body
with
one quick push or twist. We must not forget that provision for a quick
cockpit egress may be just as important.
I'm pleased that this thread seems to have made a few of us review our
restraint system and think about possible improvement.
Ed Byars


"HL Falbaum" wrote in message
newsuPwc.19014$%F2.12354@attbi_s04...
ED
Glad you're doing well. I am curious--did the crotch strap attach point
fail, or was it intact after the crash? If it did fail, at what
estimated
load did that occur? Pehaps it does not have to hold the entire load to
be
effective--your thoughts?
Thanks

Hartley Falbaum


"Ed Byars" wrote in message
hlink.net...
I sent the following to our magazine nine months ago and didn't
receive
an
acknowledgement or receipt. I guess it was not suitable for them so I
thought I would share it with ras to maybe provoke some safety
discussion.

efb10-11-03-rev.6-5-04

You may be interested in my latest crotch strap experience.

I'm still analyzing my June 2003 accident and the cause. More later on
this.
The role of the crotch strap is significant and worthy of mention.

The last half dozen gliders I've had I added a crotch strap (usually
available from Wings & Wheels), which easily clicks into the bottom,
front
or 5th slot of the standard Gadringer belt hardware. I secure the
other
end,
which terminates with the belt into a triangular link, with a quarter
inch
hole that I bolt to the seat pan with a large "wood" washer behind the
seat
pan. My gliders are Experimental category so this is legal.

I always heard that the main purpose of a crotch strap was to keep the
lap
belt across the upper thighs and prevent it sliding up to the stomach
area.
I have since learned better.

It of course depends on the direction of the accident loads and the
direction of the inertia of the body as to how all restraint straps
come
into play.

Many glider accidents involve "dropping in" vertically wherein the
tailbone
(in the L-1, L-2 area) or higher are damaged so the belts don't help
much.
You seldom see accidents with lap belt overload, but it happens. I
have
a
sad memory of helping remove a dead friend from an inverted Ventus
cockpit
where the lap belts on both sides had pulled lose from the seat pan.
Fortunately rare but it happens.

In my "incident" the nose of the glider hit hard ground at about a 60
plus
degree angle. The "load" was about along the longitudinal axis of the
glider. Since in our modern gliders (ASW-28 in my case) we recline
(sit
supine), the inertia of my body was toward the nose with only the
crotch
strap to resist. Actually Waibel designed the seat pan to take some of
this
forward load against the bottom of the thighs. In this seating the
knees
are
bent more upward.

The nose of the glider (along with my feet) was crushed in a
calculated
energy-absorbing manner. Thank you Gerhardt Waibel! I think his
design
and
the crotch strap saved my knees.

I was conscious and lucid until the helicopter dropped me off at the
Medical College of Georgia Trauma Center.

After that I really was not with it for a couple of weeks, but after
that
time I suddenly noticed that my groin area was still quite swollen. I
realized that my crotch area had sustained a significant load and that
all
things considered had kept my body from moving more forward and no
doubt
helped minimize the leg/knee damage. I had no shoulder strap or lap
belt
marks or soreness.

Since my guess is that a significant number of glider accidents impose
loads
and body reactions similar to mine, I recommend a crotch strap. Trying
to
distribute the load to the pelvic area by wearing an athletic "cup"
may
be
good for some flights, but for some flights there are other
disadvantages.
Many contest pilots regularly wear a male external catheter and I
don't
think both would work. With just the crotch strap I always had to be
careful that the strap was adjusted somewhat to the right, was not too
tight, and did not interfere with the flow from the catheter that was
to
the
left.

I suggest reading Chip Bearden's posting which appeared in the
rec.aviation.soaring newsgroup on Nov.20 1998 which outlines a more
complex
but better seat belt design.

I hope this discussion will create more thought about glider accident
safety.

Ed Byars