[soar8hours]

Well I think a forward diagonal brace would solve that minor problem?

Tommy

[Bob Kuczewski]

Well I think a forward diagonal brace would solve that minor problem?

OK, I feel much better about it now.     

[JoeF]

Tommy,
You are hot on topic! Yeah!

JoeG :: Joe Greblo
JoeF :: Joe Faust

Gouging sand, marsh, shrubs, water .... with wheels?
Compare wheels with skis, skids, spoons, wide rollers ...
Careful study of the range of options for HG is invited.

BobK, on an alternate way to brace those afting wheels: fulcrum rocker arm at down-tube base and at the forward end of the rocker arm have a tension line to the keel.

BobK, I started a page in the gathering folder:
Limit Lines in Hang Gliders
Disclaimer: These notes are development notes, not advise.
Experiment cautiously at your own risk.
 All experimentation invites the highest of safety practices. 
No warranty of function or safety is implied in any note in this project. 
Type: Limit pilot motion with special lines to hang lines
Type: Limit pilot motion with lines from pilot mass to rear keel.
Type: Limit pilot motion with lines from TCF to pilot mass.
Type: Limit pilot motion forward during landing by drogue deployment.
Type: Limit pilot motion forward during landing by dropping anchor to land or to water.
Type: ?
Type: ?

[Bill Cummings]

I am still of the opinion that the limit lines would accelerate the pilot’s arcing. (Into the keel.)
Analogy being a ball on a string wrapping around your finger gets going faster as the string shortens with each wrap.
Or an ice skater drawing in his or her arms to speed up spinning in place.
Or a diver tucking into a tighter ball to speed up a somersault.

[Bob Kuczewski]

I am still of the opinion that the limit lines would accelerate the pilot’s arcing. (Into the keel.)
Analogy being a ball on a string wrapping around your finger gets going faster as the string shortens with each wrap.
Or an ice skater drawing in his or her arms to speed up spinning in place.
Or a diver tucking into a tighter ball to speed up a somersault.

You might be right Bill. I believe that falls under "conservation of angular momentum". According to Wikipedia:

    L = r x mv

Where L is the angular momentum, r is the distance from the point of rotation, m is the mass, and v is the velocity.

If we start with: L as 100, and r as 10, and m as 1, and v as 10, we get:

    100 = 10 x 1 x 10

If we cut the radius in half while preserving the mass (and conserving the angular momentum), then the speed (v) must double:

    100 = 5 x 1 x 20

But that doesn't account for the trade off between kinetic energy (speed) and potential energy (altitude). As the pilot swings forward, he's being lifted which is making that trade and therefore acts as a slowing effect (while speed is being converted to altitude). I'm not sure which will be stronger.

Another problem with the limit lines is that the lifting may be causing the wing to rotate (whack) even faster. That depends a lot on how much the wing resists rotation which includes an aerodynamic component (messy).

So to be honest, I'm not sure how it would work either!! It was a "back of the envelope" idea, and I'd certainly encourage testing it with either a computer model or a physical model (or both!!) before hooking any limit lines to anyone's glider.

[Bill Cummings]

"----which includes an aerodynamic component (messy)."
MESSY---

Okay mount a firing mechanism to the back of the keel angled rearward and down 45 degrees.
When the base tube inertia sensors activate (sensing the impending whack) The ballistic firing mechanism fires a piton into the ground, pavement or rock which will stretch a huge bungee cord out of the keel tube lessoning the force of the whack.
(Air bag inside the double surface)
Kind of like Spiderman would do.
Now of course this is all nonsense but like you I’m trying to inspire an ah ha moment in some inventive mind.
(Disarm momentarily for launching so as not to harpoon a launch crew member during a blown launch.)

[Bob Kuczewski]

The ballistic firing mechanism fires a piton into the ground, pavement or rock which will stretch a huge bungee cord out of the keel tube lessoning the force of the whack.
   :
(Disarm momentarily for launching so as not to harpoon a launch crew member during a blown launch.)

I never said it was the best idea I ever had.     

[soar8hours]

I am goig to step out on a limb here.....

I have always thought the main suspension lines from the harness to the keel
should be a rigid arrangement much like on a nano light trike basically.
Tubes from the each side of the harness go together & join at the keel for hook up
into a keel pivot block. Or one streamline tube from the center of the back plate
up to a hang block for comp pilots. They can pivot at the hips or hinge half way up
with a locking pin that can be realeased right before you swing up on final.

This does several things....

1) allows aerobatic flyers to never fall into the sail when upside down or slow.
2) Keeps pilots from going weightless in negative G turbulence or over the falls in thermals
3) Allows another rigid structure to push on for pwered applications or mount small engines to
4) provides a means to hook a gas filled shock at a hinge point to reduce forward whack loads
5) enables a rigid structure to incorporate a system of anti-whack rods to deploy upon landing by a pilot
( in other words... a release cord that opens flap doors on the side of the main hang tube or tubes that fold
outwards 90 degrees and will not allow a point of the hang tube or harness to pass past the downtubes. Or a set
of "J" shaped hooks that catch the base bar at some point and arrest it like a carrier plane does. Limits
the forward movement to a point to keep the pilot from hitting the keel.
Just think'n outloud abit.
My 2 cents

[Bill Cummings]

Tommy I read in HG sometime back about a suggestion for aerobatic pilots that you have just reminded me of.

Their idea was to have a rope from about the crotch area of the harness go under the base tube then fasten again, with a little slack near the harness where the shoulder straps meet the harness. It seems this could save a neck injury from an impact with the keel or getting the nose of the glider on the back of your neck.
Going upright would be an issue without some kind of adjustable jam cleat.
Some harness have the jam cleat to help them stay upright,

Edit: Hey Tommy it's late where you are --go get your beauty rest. ---Heaven knows that ---oh--never mind.

[JoeF]

Tommy,
That stiffening the hang assembly is not so far out. The matter has been mentioned in some hang glider discussions online over the years. The "kite" line set that makes our systems free-flying kites are towing tethers; our pilot mass falls and tows the hang glider's wing. Since the hang-line assembly is so short, the stiffening of such tension member in order to get assets of compression during special circumstances as you have noted, is definitely something to explore. A "kite" may be towed by stiffened tethers. Just how stiff? Do we want as I once mentioned someplace, a stiff hang that is pre-curved somewhat so that a spring action damps the compression event, that is, a slow-C tethering strut instead of string cords or webbing. The slow-C strut to hang the pilot might make less shocks at inversion or neg-g events.

On the matter of BobK's multi-staged limiting flexible hang line with many limit lines: Yes, as BillC points out and BobK confirms: conservation of angular momentum will rush the pilot's head to the keep but as planned short of the crunch of the nose in whack. Well then, with strategic bracing of helmet-neck to spine-torso and upper cushioning on pilot or at the bottom of the keel, the more rapid rise might be damped or cushioned.

The tease to explosive retrorocket on body-harness of pilot may have some merit.

And about the anchor-bungee: We are just at the beginning of such. Watch rebound challenges. Consider non-rebound methods as used in aviation arresting systems on aircraft carriers or the non-rebound tearing of fall-arrest systems ... rather than rebounding bungee. Stay open for "smart" anchoring where the "smarts" read the scene and perform the most-appropriate anchoring of the pilot in the impending crash or whack scene. Anchor that plows or drags soil or water?

HG community is at an infancy about water landing yet. I look forward to the time when thousands of launch sites open with intended water landings. The HG system would be allow safe landing on water followed by pleasant sailing to shore. Or self-kiting off the water by use of water drogue and kiting launch with ambient wind or even self-powered tow.