seat belts and restraints

On 9 Dec 2004 09:58:52 -0700, (Mark James Boyd)
wrote:

Here's a wierd idea:

Get longer wings. If the wings hit an updraft, they will
go up, and flex, but the fuselage won't go up right away,
kind of a "shock absorber." Then the wings will reflex,
giving extra thrust, and dissipating the G's. A few oscillations
later and you'll feel real queasy, but you'll have more glide
and less G's. Better all around, right?

OK, a bit off thread, but has anyone modeled this (dynamic)
interaction? Sure sure, we know about best glide, but what
about the effect of long wings flapping like a seagull in turbulence?

In principle, it's possible to extract energy from fluid flow that
varies over a scale smaller than the size of the vehicle -- in other
words, if THIS part of the aircraft and THAT part are in measurably
different airflow.

There's a gadget sometimes demonstrated on model boats called a "wave
motor," that demonstrates this. You equip the boat with a lightweight
frame sticking down from the hull, and mount some hinged vanes on it.
The vertical motion of waves gets smaller with increasing depth, so
the vanes are alternately dragged up and pushed down with respect to
the deeper water, and they propel the boat.

So all we have to do is figure out the transition from "in principle"
to "in fiberglass"...;-)

rj

"Steve B" wrote in message
...
I believe that the shoulder restraints are recommended to be anchored
no more than 5 degrees below the shoulder and 30 degrees above the
shoulder in a vehicle IIRC.

In a glider I would think that the reclined position would change the
dynamics of the restraint. Because of the reclined position I would
think that there would be less of a tendency to compress the spine
when the shoulder straps are under a load. Is the 5th strap and
submerging the issue?

Would a low anchor point help with the upward motion of the pilot? How
would a low anchor point respond with a reclined seating position in a
crash?

Sounds like keeping your head intact is a primary concern and spine is
secondary?

So I am thinking 2nd set of straps with a low anchor point (for head
to canopy interference) and the standard straps to keep from
submerging (family jewels to 5th strap interference).

Steve

snip some stuff

Okay, how about this:
Below the adjusters on each of the shoulder straps, sew an extra strap.
They should be long enough to go over your shoulders and Y together
somewhere in the vicinity of the small of your back.
A single strap continues down from there, through a slot in the seatpan, to
a low anchor point. It continues through the rear low anchor point to a
front low anchor point, where it becomes the crotch strap.
Now tightening the crotch strap will also pull down on your shoulders. The
low anchor point shouldn't compress your spine, because the rear low anchor
point should be in front of your shoulders.
Because the additional straps pull your shoulders down and forward, you
can't slide up and back along the normal shoulder straps to bump your head.
Because it's adjustable, it should fit more than one pilot. There's extra
strap, but the same number of adjusters, so it shouldn't be too expensive.

Obviously, a similar scheme could be used with two straps under the seat pan
in a 6-point harness arrangement.

Tim Ward

Mark James Boyd wrote:
Here's a wierd idea:

Get longer wings. If the wings hit an updraft, they will
go up, and flex, but the fuselage won't go up right away,
kind of a "shock absorber." Then the wings will reflex,
giving extra thrust, and dissipating the G's. A few oscillations
later and you'll feel real queasy, but you'll have more glide
and less G's. Better all around, right?

OK, a bit off thread, but has anyone modeled this (dynamic)
interaction? Sure sure, we know about best glide, but what
about the effect of long wings flapping like a seagull in turbulence?

You don't have to go to long wings to enjoy this effect, but just buy an
ASW20 ("A" or C model, though the B was relatively flexible, too)!

A lot of 20 owners thought/think that the 20 did well in dolphin flight
because of this, compared to the stiff winged Ventus, but it might be
the Ventus just had separation problems near the root, unrelated to wing
stiffness.
--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

"Eric Greenwell" wrote in message
...
Mark James Boyd wrote:
Here's a wierd idea:

Get longer wings. If the wings hit an updraft, they will
go up, and flex, but the fuselage won't go up right away,
kind of a "shock absorber." Then the wings will reflex,
giving extra thrust, and dissipating the G's. A few oscillations
later and you'll feel real queasy, but you'll have more glide
and less G's. Better all around, right?

OK, a bit off thread, but has anyone modeled this (dynamic)
interaction? Sure sure, we know about best glide, but what
about the effect of long wings flapping like a seagull in turbulence?

You don't have to go to long wings to enjoy this effect, but just buy an
ASW20 ("A" or C model, though the B was relatively flexible, too)!

A lot of 20 owners thought/think that the 20 did well in dolphin flight
because of this, compared to the stiff winged Ventus, but it might be
the Ventus just had separation problems near the root, unrelated to wing
stiffness.
--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Now THAT's interesting. My stiff carbon winged Nimbus 2C isn't worth a damn
at dolphin flight. I've wondered why.

BTW, I wasn't flying the Nimbus when I got hammered by the wave rotor. I'm
afraid to fly it in rotor conditions with empty wing tanks as I would have
to do for high wave flight.

Bill Daniels

"Mark James Boyd" wrote in message
news:41b8925c$1@darkstar...
Here's a wierd idea:

Get longer wings. If the wings hit an updraft, they will
go up, and flex, but the fuselage won't go up right away,
kind of a "shock absorber." Then the wings will reflex,
giving extra thrust, and dissipating the G's. A few oscillations
later and you'll feel real queasy, but you'll have more glide
and less G's. Better all around, right?

OK, a bit off thread, but has anyone modeled this (dynamic)
interaction? Sure sure, we know about best glide, but what
about the effect of long wings flapping like a seagull in turbulence?

This does NOT seem to be the same kind of thing Gary
Osaba does in the Sparrowhawk or Carbon Dragon (with super stiff
wings), but it seems related...

Any long-wingers care to comment?


I thought you guys with short stiff ones already knew that us blokes with
long floppy ones got all that extra go from the flapping motion.

:-)

Ian ( 25.5 metres )

My 4-point belts were as tight as I could get them but they still didn't
do
enough to keep my head from hitting the canopy.

Is it a matter of having no further travel in the adjuster, i.e. the
adjuster stopping against a fold or stitch? Are the belts simply too long?
I've had that problem (in regular turbulence... I've never been in rotor)
after a bigger person had used the ship. Fortunately in the Blanik L13, the
other end of the belt is also adjustable for length - don't know about
yours.

Or are they sufficiently short, i.e. stopping your shoulders from moving
upward at all, but your head and neck are able to stretch upward to the
point that your head hits? If that's the case, it seems to me that solid
shoulder bars would not perform any better than straps.

Eric Greenwell wrote:
Mark James Boyd wrote:
Here's a wierd idea:

Get longer wings. If the wings hit an updraft, they will
go up, and flex, but the fuselage won't go up right away,
kind of a "shock absorber." Then the wings will reflex,
giving extra thrust, and dissipating the G's. A few oscillations
later and you'll feel real queasy, but you'll have more glide
and less G's. Better all around, right?

OK, a bit off thread, but has anyone modeled this (dynamic)
interaction? Sure sure, we know about best glide, but what
about the effect of long wings flapping like a seagull in turbulence?

You don't have to go to long wings to enjoy this effect, but just buy an
ASW20 ("A" or C model, though the B was relatively flexible, too)!

Or a Pegase of the first series, which had soft wings. This is indeed
comfortable in gusty air.

--

Michel TALON

On Fri, 10 Dec 2004 08:44:36 UTC, (Michel
Talon) wrote:

: Or a Pegase of the first series, which had soft wings. This is indeed
: comfortable in gusty air.

I had great fun flying one of Brian Spreckley's Pegases is France few
years back, and this energy storage in the wing was very obvious. When
you hit a thermal you could see the tips move up, then catapult the
glider a little later.

It's also important in, for example, rowing eights. Having the boat
slightly flexible means that some of the initial thrust from each
stroke is stored in the hull, then released as the rower pull more
gently towards the end of the stroke. One reason that the early
carbon-fibre eights weren't terribly successful, and were replaced by
more flexible moulded wooden ones.

Ian


--

At 05:30 10 December 2004, Tango4 wrote:

I thought you guys with short stiff ones already knew
that us blokes with
long floppy ones got all that extra go from the flapping
motion.

:-)

Ian ( 25.5 metres )

Now that is impressive :-)

Don (20 metres)

Don Johnstone wrote:

Ian ( 25.5 metres )

Now that is impressive :-)

Don (20 metres)

I always believed that size didn't matter?

Stefan (23 cm)