[Bill Cummings]

OK Bill,

If you draw the arc that the pilot follows due to the harness suspension and then do the same for the chest harness it will show where the pilots head will be at any time during a nose in. The further forward the pilot is so the lower he/she would be pulled. When standing upright the pilots head would be closer to the keel.

Tony

Front restraint rope added..JPG

What looks like the far downtube is really the hang strap.
What looks like the basetube is really the ARP Restraint Rope.
Imagine the far downtube is hidden behind the nearest downtube.

Tony,
I'm thinking that using wheels along with the ARP,R (R=Restraint Rope) one could also make a nose skid that is hidden under the fabric nose cone (Sacrificial piece) waiting to cause a skidding situation rather than a nose dig in.
Still to figure out is what the "G" load would be for an average whack at let's say -- 30mph (on the high side-). Then plan on the tension strength (breaking strength) of the ARPR for the way it must be routed. I would want the ARPR to break after the control frame but not before.
I want to keep in mind that if I load a ARPR in the middle of the cord that it will break before a straight in line load would.
http://ushawks.org/forum/viewtopic.php?f=25&t=1146
(Thanks Bob!)
Just looking at the action diagram in the link above I would guess that the ARPR being loaded in the middle, if it is routed to both downtube bottoms, one would have to add 0.6 times to the cords breaking strength.

[Bob Kuczewski]

I must have showed up after the logo changing party. Now I am curious what it used to look like.

We just added our new mission statement to the bottom: "To Promote, Protect, and Server Recreationaly Hang Gliding". 

I do like the way OUR acronym USHHGA pronounces exactly like USHPA did BEFORE the para-merger....that was very clever

The "SHH" part ( ) has the additional connotation to keep it quiet because USHPA might expel you if they find you're a member. The very first "charge" listed in my kangaroo kourt USHPA expulsion was this:

The behavior upon which the board has determined that you should be expelled from the association falls into the following categories:

1. Creation of at least two national hang gliding organizations with the stated purpose of competing with USHPA, one of which you currently control;

So we have to go by USHHhhhhhGA.   

[ARP]

Bill,

I have not attempted to calculate the loads and the breaking strains of the restraint line(s). The material they are made from will also have an elastic property that needs to be accounted for. The trial and error method of RS should work fine, as no one is at risk, and various options can be tried. Yes the line should not give way before the frame collapses but once the frame goes the whole thing is compromised anyway. As mentioned before, safety lines usually have breakaway stitching that allows progressive stretch before the final arrest, thereby reducing the shock loading to the person. Depending on the available distance between the pilot's head, at full stretch, and the keel is sufficient then this could be an added feature.

On one of my early gliders I truncated the the nose to form a T rather than an A shape and used a thick foam nose cone that improved the aerodynamic shape as well as preventing it digging in.

It must also be noted that Lilienthal did, at times, fit a hoop to the nose of his gliders to protect the pilot in a nose in crash which prove successful on at least one occasion.

Tony

[reluctantsparrow]

I found some nice pulleys Bill, but thanks for the offer. I will get around to further safe splat testing at some point but right now I am fully occupied developing and testing a totally different device.

In answer to ARPs inquiry,

I will probably not test any of the ideas that do not utilize the pilots harness fully as a safety system. I am convinced the splat arrest needs to come from behind the pilot, pulling back on the harness to spread out G forces to the pilots body.

a line running from one corner of the basetube, through the pilots harness, to the other corner of the basetube presents many problems in my mind as Bill also pointed out such as.... how would one launch or rotate for landing with such a rig and would it interfere with towing?
But my main resistance to the idea is it does not utillize the pilots harness to spread out g forces to the pilots body and there is no room to install shock absorbtion devices.
a forward attachment point would allow the mass of the pilots body rear of the attachment point to converge on the attach point and if that attach point was firm, with no shock absorbtion.....?
I see a cartoon crash scenario where the pilot from the chest foreward looks fine but from the chest rearward looks like an accordian.
Also, we are looking for a restraint system that works in high G crash scenarios (or at least I am)
i am not looking for a device that only works in low G scenarios....like my tests so far....totally low G.
I only used 60 pounds in the tests so far and the glider was not moving that fast due to bad pulleys mostly....
In future tests that airframe is going to be really moving and there is going to be 200 pounds loaded into that harness...a real life scenario....
Our goal is to bring all that sand to a gentle stop with no damage to the glider, sandbags, harness, wires, etc.
but like I said...I have another project running that takes priority for me at this time....
when My other project is complete I will return to testing safe splat devices.....RS

[ARP]

RS,

With the lower restraint attached to the front of the pilot harness the loads will transfer through the harness webbing to the main shoulder straps. The same would apply to your rear restraint so the resulting load path will be the same. The leg straps will not restrain the body going forward but the harness cocoon, with a back plate, will help keep the body in line. The main purpose was to stop the head colliding with the aircraft nose or keel tube as it is the most vulnerable part of your anatomy. To protect the whole body, something like an airbag inside the cocoon to splint the body would be needed. What I am proposing is a simple strap restraint to prevent the head collision.

With your rear restraint the anchor point will be high up which will allow the head to jerk upwards and collide with the keel in a whiplash action. By using the base bar of the control frame a triangle is formed which prevents the head going any higher once the full extension of the line is reached in association with the main harness support.

If the crash is at high speed then your endeavour to also save damage to the glider is a forlorn one. The fact that the glider absorbs the impact and eventually gives means that the pilot is saved. Stopping a glider dead at full speed is going to be anything but gentle. The best you can hope for is to minimise major trauma to pilot at the expense of damage to the glider. .

I addressed the question of the line getting caught up on a tow trolley earlier as not insurmountable given some thought but the main problem was to prevent head injuries during a crash. If you look at the drawing done by Bill you will see that the chest restraint does not impair the pilots ability to rotate upright for both take off and landing.

What do pilots do with their VG tension line when towing to prevent it becoming entangled around the trolley ?

[Bill Cummings]

(RS)

....a line running from one corner of the basetube, through the pilots harness, to the other corner of the basetube presents many problems in my mind as Bill also pointed out such as.... how would one launch or rotate for landing with such a rig and would it interfere with towing?
But my main resistance to the idea is it does not utillize the pilots harness to spread out g forces to the pilots body and there is no room to install shock absorbtion devices.
a forward attachment point would allow the mass of the pilots body rear of the attachment point to converge on the attach point and if that attach point was firm, with no shock absorbtion.....?

RS I think my first reading had me thinking as ARP appears to be thinking. After reading several more times my understanding now is that you were not stating that the front attachment method would not stop the pilot with the harness --- but --- that it would not stop the pilot with the same, give, or shock relief.

The front attachment as ARP and I have been advancing works more along the thinking of a seat belt restraint as opposed to the thinking that works along the lines of an air bag. (a restraint with some "give," slower loading, or inertial dampening.)
My thinking at this stage of the front attachment restraint (R&D) will be, later, to add some type of dampening to the system.

Now as to: (ARP)

With your rear restraint the anchor point will be high up which will allow the head to jerk upwards and collide with the keel in a whiplash action. By using the base bar of the control frame a triangle is formed which prevents the head going any higher once the full extension of the line is reached in association with the main harness support.

My thoughts are, that as tested so far on the zip-line by RS, the rear restraint idea has mitigated to a greater extent the whiplash problem.
This happened when the lower wires took more of the load instead of directly going to the keel.
Will it be enough? I think we will have to wait until RS is freed up to test with 200 or so pounds of sand bags. It might show a whiplash.
_______________________________________________________________
As for the VG cord stowing, - a bungee ball tie around the down tube would be a good way to keep the dangling VG cord from touching the launching platform.

[ARP]

Bill,

The original idea from RS was to use the keel tube with a shock absorbing damper inside the keel. The later idea was to use the rear rigging wires with a sliding arrangement travelling down the wires towards the control base bar. Depending on how far the restraint lines travel, down the wires, the tension will pull on the wire like the string on a bow bending the rear part of the keel down. The spring reaction to this may well produce a whiplash action on the pilot mass. By fixing the restraint lines to the base of the uprights the load is directly in line with the rear rigging wires to the keel without the bow springing effect.

On either of the proposed restraint systems, arrest cannot take effect until the pilot reaches the foremost control position. That point will vary on each glider and for each pilot, so any progressive stop system will have to be tailored to the particular combination of glider and pilot. If there is sufficient distance to fit a progressive stop then a built in energy absorption device would be helpful. However the prime action needed is to provide a device to prevent the pilots head hitting the nose/keel, in a crash situation.

I asked about the VG line to show that it does not appear to be a problem with current towing operations. Likewise I see no difference with the lower restraint line(s) causing a problem.

[reluctantsparrow]

Okay, I see it, However, a perfect safe splat device that will work very well in a large percentage of crash scenarios has already been invented.
They are called Wheels, more specifically, adequate wheels, that can handle the weight of the aircraft, the speed of touchdown, and the terrain to be landed in.
I wrote an article about this many moons ago and I have noticed more pilots flying with adequate wheels, but not too many, especially in comps, where adequate wheels are needed the most due to landings in varied terrain, mostly plowed fields where NW comps are held (chelan)
If a pilot wants to fly without wheels for personal efficiency (which I respect)... that same pilot is not going to fly with any safe splat device that increases drag no matter how effective it is.
I am not interested in developing a safe splat device to protect the other group of pilots that fly without adequate wheels for ego reasons. I would rather let them die in the manner of their choosing.
I have been flying 44 years and never had to use my parachute once (knock on wood) and yet flying with a parachute is required safety equipment in a comp.
I have flown with my helmet which is also required safety equipment and have only crashed once in a manner where the helmet probably prevented injury.
My twelve inch wheels have saved my bacon three times......but wheels are not required safety equipment.
I am not too impressed with our sports intelligence and I really have no desire to develop a safety device to save those who are too proud to slap on a pair of adequate wheels and would not slap on a safe splat device for the same reasons...such as....I am a great pilot, I am so good I dont need safety devices...or....I am into hang gliding to look cool, and that safety device is not cool.....
I say let them die in the manner of their choosing.
Yes, I am an ice cold bastard...but...
I will get back around to testing these ideas because it is fun.
That is my only motivation.

[ARP]

RS,

Yes wheels work well for relatively smooth landing surfaces and deliberate wheel landings are often conducted by the tandem flight operators. Skids also provide protection and can be used on rougher surfaces with less of a drag penalty.

The drag penalty and weight penalty of the lower restraint are far less and might be acceptable even for those that want to look "cool". The added safety feature of the lower restraint as a back up suspension, if a pilot fails to clip in properly on the main, solves another problem that has been a concern of many.

[Bill Cummings]

Hawks,
I've not been around a set up glider for a little while due to the triple digit heat in our desert southwest area.
We came close to going out to Dry Canyon today but one by one we called it off.
If we had gone out today with the 100 degree heat in the LZ I couldn't imagine anyone that would be willing to stay in the harness long enough to do a range of motion rigging adjustment test with the front restraint R&D.
O to 4 mph in the LZ @ 100 degrees would be like cooking bird in a, New Wave Oven.
I still hope to do this test and use the GoPro so others can offer up suggestions.