[Bill Cummings]

other project was put on hold (again)....going to be back to testing sooner than anticipated,
going to reinforce the keel, and alter the front hang point dramatically,
my alterations ar going to put less stress on the keel and provide a more definite...WHACK action at the same time.........thanks for all the suggestions....
...if everything looks good after re-testing 60 pounds, will start raising the poundage in 60 pound sandbag increments and post results...RS

From the band --- May we have a drum roll please?
____________________________________________
EDIT 09:16 --
Jim, Is the stitching holding up where the mains meet the harness pod?

[reluctantsparrow]

i will check Bill, thanks for bringing that up for me to check, but I suspect it is.
What is really weird is you can always tell how many pounds were held by certain knots by how hard certain knots are to untie once they have been loaded up....like...thats why I mainly use a bowline....you can hang on that thing all day and still untie it easily....but an overhand knot?....load that thing up and you need pliers to untie it....
so...when I tied up the showstopper to the keel in the manner Peter Jamtgaard advised when he saw what I had done so far (peter is the friend who owns an engineering firm in oregon? not sure which state actually)
Anyway..that overhand knot untied very easily....which shocked me after seeing the huge crash with 60 pounds...I expected the knot to be much tighter.
Peter also advised me on some peizo meters he sees are needed to measure actual force. I laughed. And who has any Money to buy THOSE with Peter?
I am not complaining. i love my lot in life. But I realize most people who work as hard as i do have money and do not understand why someone who can do what I do does not.
I fully realize most of you are very comfortable. That is fine, so am I.
I have 36 dollars in my bank account and i AM quite comfortable.
I cant drive very far but I dont want to.
I have everything I need right here.
I realized my way of life is foreign to most of you so i thought I would share so you will understand better that I really am doing this only because its fun.
Every pulley has to be found at a garage sale....and THAT is fun!
Every rope used was found at a garage sale except for the one Kim Smith Gave me for the main zipline.
I appreciatte the offer Bill made a while back but I would rather keep it the way is...
It makes for a more interesting life experience.

[Bill Cummings]

Jim,
It seems to me that a real crash will have the basetube coming to a more abrupt stop than is shown on the zip line crash simulation.

It would follow, it seems to me, that there is a finite distance between the basetube and the helmet/keel impact area.

The zip line is stopping the keel from intersecting the pilots (helmet) inertial arc path. The pilot's path is somewhat independent from the path of the air-frame.

Just after initial impact I think we are seeing more air frame travel during the tests (distance over ground) than we would see in a real crash.

It looks like there is some elasticity in the harness suspension making the pilot go weightless (rebounding). This allows the pilots helmet and keel to close the distance. Perhaps the ARPR would impede the rebounding.

The rebounding (weightlessness of the pilot) yet still forward motion will have less weight on the frame and then probably skid the basetube forward after its initial complete stop.

If you are able to rig the glider/zip line hang point to allow the nose more downward travel I'm thinking we will see less of pilot/helmet arc travel distance to work with.

finite distance.JPG (33.64 KiB) Viewed 4247 times

Notice the slack mains and hang strap. (Rebound.)
(I should have extended the red arc line to stop at the keel and not the left leading edge.)

[Rick Masters]

This is fun to watch but why isn't the pilot hanging on to one of his uprights in a crash situation?
That is the survivable strategy in all cases.
Any pilot who flies into the ground in a prone position risks serious injury or death.
His head and neck are close to the ground and at risk of striking it.
If his head or neck hits the ground, the keel device is irrelevant.
A pilot wrapped around a downtube at the moment of impact has several survival factors going for him.
First, the downtube is going to absorb energy when it bends.
Second, the pilot is going to be thrown against the undersurface of his sail when the nose slams into the ground.
Striking the ground in a yaw and letting a leading edge take the blow, even better.
This is how to survive a hang glider crash.
The hang glider is expendable.
Use it. Break its bones, not yours.

[Bill Cummings]

This is fun to watch but why isn't the pilot hanging on to one of his uprights in a crash situation?
That is the survivable strategy in all cases.
Any pilot who flies into the ground in a prone position risks serious injury or death.
His head and neck are close to the ground and at risk of striking it.
If his head or neck hits the ground, the keel device is irrelevant.
A pilot wrapped around a downtube at the moment of impact has several survival factors going for him.
First, the downtube is going to absorb energy when it bends.
Second, the pilot is going to be thrown against the undersurface of his sail when the nose slams into the ground.
Striking the ground in a yaw and letting a leading edge take the blow, even better.
This is how to survive a hang glider crash.
The hang glider is expendable.
Use it. Break its bones, not yours.

Rick,
Good point about getting the head/neck area out of line with the keel.
I'm thinking that if there is a way to do that without grabbing somewhere mid-span on one downtube or the other
the out come could even be better if the downtube remained intact.
My old Magic 3 had .035 round inner sleeving .035 fared (sp?) and was a true crash-o-matic when it came to side forces. I pounded .058 into the new replacement when it arrived.

[Rick Masters]

the out come could even be better if the downtube remained intact.

The total force of impact is reduced by the release of heat (energy).
Heat is generated by the sudden bending of aluminum.
You don't want it to snap. You want it to bend first.
A bent leading edge or bent downtube means your hang glider was looking out for you.
If your downtube does not absorb some of the impact force, it gets absorbed somewhere else.

Likewise, the keel compression device generates heat.
The air is heated during compression.
The total amount of heat generated by the compression device can be compared to the total amount of heat generated by the bending downtube,
The one that releases the most heat in a crash is most efficient.

I am confident that compressed air will not create anywhere near the amount of heat released by bending aluminum.

[Bill Cummings]

the out come could even be better if the downtube remained intact.

The total force of impact is reduced by the release of heat (energy).
Heat is generated by the sudden bending of aluminum.
You don't want it to snap. You want it to bend first.
A bent leading edge or bent downtube means your hang glider was looking out for you.
If your downtube does not absorb some of the impact force, it gets absorbed somewhere else.

Likewise, the keel compression device generates heat.
The air is heated during compression.
The total amount of heat generated by the compression device can be compared to the total amount of heat generated by the bending downtube,
The one that releases the most heat in a crash is most efficient.

I am confident that compressed air will not create anywhere near the amount of heat released by bending aluminum.

Here is my thinking at this point in time (but it could change in a minute.) The point in time that the downtube converts the energy into heat is the most relevant consideration.
The pilot, within the cage of the air-frame, has protection from coming in contact with the ground to some degree.
When the basetube hits the ground during a crash and stops, the pilot will swing in an arc until meeting the air-frame or sailcloth.
The maximum distance the pilot travels depends on the downtubes retaining their shape.
Within this allowable maximum distance the rear restraint system will come into play.
If on another scenario a downtube does not retain its shape, due to the pilot hugging one downtube, causing it to bend or kink, the keel will lower the pilot closer to the ground. The ground will shorten the distance the pilot would have traveled.
This would shorten the distance in which the rear restraint would have an effect.
If the pilot's body was aligned in a slight cross controlled position (slightly diagonal) or even held to one side this would take the keel slightly out of the strike zone.

[reluctantsparrow]

All points considered, I am recuperating from a futile attempt to cut my thumb off with a tablesaw. only 6 stitches. Not bad.
I agree with points made by ARP, Bill C., And Rick
My test rig is inadequate and not showing real life action.
I have already reinforced the keel and mounted a quick release on the nose of the glider to drop the nose a split second after the basetube restraint lines go taught....I also was given a HUGE pulley mechanism by David Chadwick (you torrey rats probably know him, Chadwhack hangs out at Torrey at least once each winter) so hauling the glider up the tree is going to be easier....but
the speed of the test vehicle is NOT reflective of flying speed... the transfer of weight to the rear wires and rear keel IS going to alter how a glider reacts and which items, like downtubes, will be negatively impacted, etc., etc.
Looks like I have some time to think about it....thumb is healing well, glad I didnt lose it, would have been a bitch trying to hitch hike.
HOw about a really tall helmet that looks like Cat in the HATs hat (Dr. Suess) with a huge shock absorber inside?

[Bill Cummings]

Wow! That was close Jim.
Is it the pen and pencil thumb or lazy thumb?
Some people more crass than me would ask, "Was it the toilet paper thumb or the other thumb?"
If you put a leach on the tip of the thumb it will promote better blood supply while healing.
EDIT: At my age I just thought of another place I could use a leach

[reluctantsparrow]

My thumb has recovered to a sufficient degree that I can begin re-rigging the zipline to simulate a real crash. Based on input here is what I am rigging up today.
1. I am removing the sudden stop lines from the base tube to allow the ground itself to provide a more natural stopping action.
2. I am going to rig both pulleys to disconnect to allow the airframe to react naturally with the contact with the ground so there will be no dancing around midair to confuse the results. I will probably rig to allow the front pulley to disconnect a split second before the rear pulley disconnects.

I can not simulate breaking aluminum downtubes without incurring great costs but I CAN tie back the pilot with a light line designed to simulate the resistance provided by breaking aluminum before the pilot swings forward.
What think ye?