[reluctantsparrow]

In real life the line is going to be pulling from the top of the right shoulder strap (or the left side)....
Right now the line from the harness is solidly anchored to the top of the right shoulder strap but I guess that did not really show up in the video or made clear.
...the reason in my head for the fancy rigging to both straps is there are no arms or neck on the test dummy that usually help hold the straps in position on the pilots shoulders...I would have just ran the line from the top of the shoulder, diagonally downward to the bottom of the opposite shoulder strap, but then I could not get in or out of the harness for demonstration purposes..in real life the line would terminate at the top of one shoulder strap or the other....

[Bill Cummings]

Copy that Jim!
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Sidewinder Restraint Cord
I'm thinking about tying off the Sidewinder Restraint Cord to the back of the shoulder strap.
Pilots flying with a cocoon harness could easily find and anchor strap but pod harnesses like Jim is using might take installing two grommets to run the line around a rear shoulder strap.
I just left a message for Ole to call me back to remind me what the leach line that he gave me was called (502) and the breaking strength.
I'm wondering if a cord strong enough to get a pilot turned on the swing through and then break so the pilot continues on to impact the sail to the side of the keel may be desirable?

[Rick Masters]

You don't need a line to turn your body sideways.
That happens when you hang onto the downtube.
The primary purpose of the line is to compress the foam and extend the collision.
The secondary purpose is to prevent the pilot from reaching the danger zone on high-aspect ratio gliders where the nose or leading edge could slam down on the pilot.
It should be used in concert with hanging onto one downtube.
Because again, it's up to the pilot to make the right survival move before impact.
Nothing is going to fix his mistake if he blows it.

Attaching the line in a way it could be wrapped around the pilot's neck in a tumble would be a big, big mistake. Get it away from the neck and route it as short as possible.

My guess is an attachment point halfway down a midpoint harness suspension line would work best. The line can't be elastic. I think a 1/16 inch plastic-coated steel cable would work best. The slickest way to route it from the compression foam device would be through an angled sleeve passing through the bottom of the keel as close to the upright junction as is proven effective. The pilot should impact the sail sideways at the moment full compression of the foam is accomplished.

[reluctantsparrow]

Okay, soaking in all the input....I am concerned somebody might see how I rigged the line under the pilot neck and not get the memo so I am going to make it clear on the next video that that was for testing purposes only...and then re-route the line to pass directly from one shoulder strap to the other....BEHIND the pilots neck.
I disagree about the pilots responibility to grab a downtube......I want a line/foam device that does all the work for the pilot..here is why....
a full on launch run from a flat slope launch in thermally conditions where the pilot screws up and begins his run just as something changes and the glider gets ahead of the pilot. Now the pilot is playing catch up with the glider to no avail and his speed is increasing as the glider gets ahead of him, catches the ground, and comes to an abrupt halt, leading the pilot into a head first dive right into the keel.....this is what took out a good buddy of mine that never makes mistakes....then made one....and now he sits in a wheelchair....
I dont see a pilot in that flat out run....glider gets ahead of him scenario..being able to switch gears fast enough to grab a downtube. I also think the experienced pilot is going to not give up but use both hands to throw out the DTs as far as possible hoping for a last ditch save and get airborne....
yep, the instinctual reaction in that scenario is going to be to get that thing flying, run harder and harder, then push way out with both hands at the last minute.....not abandon all hope and wrap two hands around one DT....
A line tied to only one side....routed properly as to not decapitate the pilot, tied into a compression piston of some sort on the rear keel(stinger).....so everything is aftermarket....no changes made to the certified configuration, easy to use.....easy to hook into....does not interfere with any control movements or ground handling actions....does not interfere with towing...creates very low drag.....then only kicks in when all else has failed is what I am shooting for...
Most our accidents that result in injury are chalked up to pilot error.....If we are really looking for a device that prevents injuries from occurring than we should be looking for a device that not only works in spite of pilot error, but is geared to kick in because of pilot error.

[Bill Cummings]

Okay, soaking in all the input....I am concerned somebody might see how I rigged the line under the pilot neck and not get the memo so I am going to make it clear on the next video that that was for testing purposes only...and then re-route the line to pass directly from one shoulder strap to the other....BEHIND the pilots neck.
I disagree about the pilots responibility to grab a downtube......I want a line/foam device that does all the work for the pilot..here is why....
a full on launch run from a flat slope launch in thermally conditions where the pilot screws up and begins his run just as something changes and the glider gets ahead of the pilot. Now the pilot is playing catch up with the glider to no avail and his speed is increasing as the glider gets ahead of him, catches the ground, and comes to an abrupt halt, leading the pilot into a head first dive right into the keel.....this is what took out a good buddy of mine that never makes mistakes....then made one....and now he sits in a wheelchair....
I dont see a pilot in that flat out run....glider gets ahead of him scenario..being able to switch gears fast enough to grab a downtube. I also think the experienced pilot is going to not give up but use both hands to throw out the DTs as far as possible hoping for a last ditch save and get airborne....
yep, the instinctual reaction in that scenario is going to be to get that thing flying, run harder and harder, then push way out with both hands at the last minute.....not abandon all hope and wrap two hands around one DT....
A line tied to only one side....routed properly as to not decapitate the pilot, tied into a compression piston of some sort on the rear keel(stinger).....so everything is aftermarket....no changes made to the certified configuration, easy to use.....easy to hook into....does not interfere with any control movements or ground handling actions....does not interfere with towing...creates very low drag.....then only kicks in when all else has failed is what I am shooting for...
Most our accidents that result in injury are chalked up to pilot error.....If we are really looking for a device that prevents injuries from occurring than we should be looking for a device that not only works in spite of pilot error, but is geared to kick in because of pilot error.

[Rick Masters]

No way.
If a pilot is holding both downtubes and slams into the ground, he will shoot straight forward.
An attachment of the compression line to the shoulder strap won't have enough moment arm to spin him.
In fact, the moment arm will approach zero as the line goes tight (not good) and pulls toward the centerline (primary vector) of force.
Attached to the shoulder, it will only arch his back (probably not good) and raise his head and shoulders toward the keel (probably not good).

A pilot who holds onto one downtube rotates so that his body is parallel to the sail.
If the line is tied just forward of the hips and the pilot grabs a downtube - eureka! - it is acting on the center of mass of the pilot (good).
The real problem here is that the pilot who holds onto both downtubes shoots forward and runs out of room.
His head is near impact when the compression device starts to work.
Not enough room. Not enough time.
His head is two feet forward of his hips and two feet forward of the point the compression line is trying to stop him from reaching..
His entire body mass is piledriving onto his neck at impact.

I predict the line will not turn him enough to help him if your focus is on the line causing significant rotation.
He has to do it himself by grabbing a downtube.
It's part of piloting.

Again, the compression device and the line serve only to extend the time of collision and thereby reducing the potentially catastrophic forces acting on the pilot.
It isn't going to do anything else well.
It's not a Swiss army knife.

[Bill Cummings]

moment arm(Noun)
The perpendicular distance from a pivot to a point undergoing torque.
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Massachusetts Institute of Technology
It is defined as the product of the force (F) and the moment arm (d). The moment arm or lever arm is the perpendicular distance between the line of action of the force and the center of moments. Moment = Force x Distance or M = (F)(d) The Center of Moments may be the actual point about which the force causes rotation.

Wouldn't the perpendicular distance be about 6 to 8 inches from the shoulder attachment Point?
Me = 187 lbs, + harness = 20 lbs, = 207 lbs.
How could this arrangement not cause a rotation?

[Rick Masters]

Wouldn't the perpendicular distance be about 6 to 8 inches from the shoulder attachment Point?

Your line of force will be the trajectory of the pilot's mass.
You might get 8 inches L with him angled this way, or 0 inches L with him angled that way.
It's not just an unknown, it's a variable. You can't depend on it. You can't design for it.
Besides, it's a bad idea.
I sense some confusion here as to what the purpose of the device is.
The purpose of the device is to extend the collision.
It doesn't have anything to do with rotating the pilot.
That's what I mean by the Swiss army knife approach.
The primary objective should be perfectly met..
Don't try to dilute it by making it do other things.
If you attach the compression line off center of the pilot's mass, it will have less effect.
You want to maximize the force caused by the pilot's mass surging forward to operate the compression device to best effectiveness. If you try to spin the pilot with the line, too, you're throwing a lot away.

The moment arm for a pilot hanging onto one downtube is a foot or a foot and a half, every time.
That's good. Use that.
It's a significant and reliable moment arm.
The compression device line should be connected to the center of the pilot's mass, attached just forward of the hips, I would think.
The pilot's mass causes the compression of the foam.
The pilot's grabbing onto a down tube causes the rotation.
Flying hang gliders can be dangerous and we're talking about crashing them here.
I expect the pilot to grab a downtube.
That's REALLY important.
And the compression device might help a little bit.

[Bill Cummings]

Rick>
Your line of force will be the trajectory of the pilot's mass.
You might get 8 inches L with him angled this way, or 0 inches L with him angled that way.
It's not just an unknown, it's a variable. You can't depend on it. You can't design for it.

Thanks Rick,
I can see it now.

0 rotation.JPG (21.79 KiB) Viewed 4756 times

CG or CM = center of pilot mass.
AP = Attachment point.
If they line up there will be no rotation.
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But could the same be said of the one sided ARP restraint to the corner of the control frame?

[reluctantsparrow]

Went ahead and did a test with the sidewinder line hooked all the way back to the keel piston behind the rear flying wire/landing wire junction and it was a total fail. Too much forward travel...as the pilot swung forward and up towards the keel the restraint line is also approaching the keel allowing more forward travel (too much).
I would post the vid (a lot to be learned from it) but I just cant seem to upload it to youtube right now for some reason. Tried posting it like ten times....checked all my internet connections....retarted my computor...then gave up posting it to youtube....too bad....the results are simply smashing (nice solid impact dead center on the noseplate....a balloon head goes right through what would be a sail_
What I saw in that test is that a lower attach points along the rear flying wires is vital to the success of any line configuration due to the geometry of the situation.
the lower attach point along the rear flying wires is also vital to keep all lines out of sight behind the pilot with zero risk of entanglement......I had loaded 180 pounds of sand which was soaking wet so closer to 200 pounds on the sidewinder test with no failure of any glider parts...just a failure of the line itself to meet geometric requirements....the sidewinder did not turn the pilot sideways as Rick predicted it would not.....a straight ahead impact into the noseplate.... the sidewinder without any lower attach to the flyng wires did not engage the rear piston at all.....too long, like the Arp line....the geometry just did not work out for the attach points I have available on the old harness I am using....I am going back to testing the showstopper or bermuda triangle... Which both keep the lines out of the way of the pilot and both seem to have the right geometry to prevent head impact with the keel or sail....in fact...I think the sidewinder would have worked equally as well if it had of been routed down to the pulley on the rear flying wire before being attached to the pilot....but no...the sidewinder did NOTHING to turn the pilot sideways....it just plowed straight forward....
finally got it to upload...nice crash....a total fail but learned a lot...
In contrast to what I say on video, on closer inspection the trolly release actually did work properly....