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Re: The 5 ft-packed-HG Movement

Postby Bob Kuczewski » Sun Jul 31, 2022 6:39 am

I think the recent posts about cross country and safety are getting a bit far off topic from the intention of the 5 foot packed glider topic. Of course, a 5 foot packed glider might be great for cross country flying, but that's a different discussion from the safety and desirability of cross country flying in general.

So to keep this topic on focus ("The 5 ft-packed-HG Movement"), I've quoted these last few posts in the topic titled "Flying XC Question". Please reply there about safety and desirability of cross country flying in general and leave this topic for discussions of the "The 5 ft-packed-HG Movement". These discussions could include how a 5 foot packed glider could benefit cross country flying. But discussions about the safety and desirability of cross country flying in general would be a better fit for the other topic here:

     https://ushawks.org/forum/viewtopic.php?f=2&t=3824

Finally, I apologize to Joe for my part in taking this topic off on a bit of a tangent. Please continue your good work and discussions on the 5 ft-packed-HG Movement.
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Re: The 5 ft-packed-HG Movement

Postby Frank Colver » Sun Jul 31, 2022 12:25 pm

Thank you, moderator!
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Re: The 5 ft-packed-HG Movement

Postby JoeF » Mon Aug 01, 2022 7:45 pm

Anti-buckling gain from overlap method of joining two beam parts:
Carry two parts of a desired beam; those two parts are to be joined to make a final-lengthed beam. Though the two parts could be different lengths, suppose for the moment both parts are of the same length, say both 5 ft. long (or both 4 ft long; or both 3 ft long). Working for the moment with the 5-ft parts, and say, for the moment, choose overlap method (other methods would have other results) to join the two parts to make the final beam. The amount of overlap subtracts once from the 10-ft resulted final beam; suppose for the moment the overlap is 1/2 ft resulting in a 9-ft 6-in beam. Overlap might be via side-by-side join or by telescopic fitting or similar designs. Notice that the central region of the beam obtains the anti-buckling when the final beam is under compression. This concept space might be tapped by some who are working on HG packings to meet the 5-ft packing (or less than 5-ft packing, if desired).

If one wanted an 8-ft rib and had a pack title of 5 ft max, then one woul5d have many choices for two parts that make an overlap to give the rib: say 5 ft and 3.5 ft using 0.5 ft overlap; or 4.5 ft and 4 ft using 0.5 ft overland. Etc. Infinite choices within the chosen limits. The two beam parts need not be of homogeneous form or density or taper; so a huge other space of design is available.

Teases:
https://scoutpioneering.com/tag/overlapping-spars/
https://www.woodmagazine.com/woodworkin ... end-to-end
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Re: The 5 ft-packed-HG Movement

Postby JoeF » Tue Aug 02, 2022 11:14 am

HG at 4-ft pack (or 5-ft, or 3-ft, etc.) might employ rigging lines. An optional design direction is "soft rigging" rather than harder steel rigging. This note relates to a tactic that is optional in soft rigging: pigtailed lark's head knots grabbing soft knots:
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Re: The 5 ft-packed-HG Movement

Postby JoeF » Wed Aug 03, 2022 9:28 pm

The beams of a HG packing to a length of 5 ft or less might be of bamboo, wood, aluminum, steel, fiberglass-epoxy, epoxied fiberglass, etc.; that is, a design decision might focus on one type of material. Or the various beams in one HG might vary in material type. Design away! Getting the most value from a material may take study, art, and advanced craft. Quick-and-dirty efforts might be a choice at time where losses may be acceptable. Purpose and price are other dimensions to the design space. >

Each material has its safety space. Heed such spaces!

Teases:
https://en.wikipedia.org/wiki/Aluminium_alloy
https://en.wikipedia.org/wiki/Bamboo_construction
https://www.compositesworld.com/
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Re: The 5 ft-packed-HG Movement

Postby Bob Kuczewski » Thu Aug 04, 2022 9:56 am

JoeF wrote:The beams of a HG packing to a length of 5 ft or less might be of bamboo, wood, aluminum, steel, fiberglass-epoxy, epoxied fiberglass, etc.

You've also mentioned beams of compressed air.

For structure, there are anti-compression elements, anti-bending elements, and anti-stretching elements. Anti-stretching is easiest using cables or lines. Anti-bending can use beams or sometimes fabrics. Anti-compression is the toughest problem, and that's where we generally turn to beams.

That got me thinking about paragliders. Where are their beams? The answer is that they use ram air inflated beams. The ram air at our flying speeds isn't enough for much rigidity without lots of support from anti-stretching elements (lines) and anti-bending elements (fabric). That's why paragliders suffer from collapse.

What's my point? Maybe the 5 ft. packed glider could reduce its need for compression elements (or reduce the needed strength of those elements) by considering the anti-compression elements and strategies used in paragliders. Maybe a paraglider-like wing with much lighter rigid structures (splints?) could avoid the pitfalls of a purely air-inflated wing? As a PG pilot, I've often wondered if adding a little bit of rigid structure could eliminate the collapse problem.
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Re: The 5 ft-packed-HG Movement

Postby Frank Colver » Thu Aug 04, 2022 11:52 am

I've seen some discussion of adding rigid elements to paragliders but it usually boils down to: too much. How much structure would it take to keep a paraglider's shape in turbulence?

Also, if the pilot is still hanging well below the wing, by strings, the "cravat" problem of a tip going under strings and getting hung up inducing a death spiral could still exist. And the loss of control by slack strings.

Of course it is always important to continue to think and discuss the possibilities of a hybrid structure, between PG and HG. I'm not throwing "cold water" on the idea.

I wish i had the facilities, materials, and talents of Alpacka Raft Inc at my disposal, to play with inflatable wings. I visit them every fall and when I look at their products I think: if only one of those resembled a wing.......... :think:

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Re: The 5 ft-packed-HG Movement

Postby JoeF » Sun Aug 07, 2022 2:18 pm

Keeping a lateral eye on tensegrity (fully distinguish from splinted-based tensairity),
we add a paper for study (paper might be a challenge to obtain fully).

Design and control of tensegrity morphing airfoils
Muhao Chena, Jiacheng Liub, Robert E. Skeltona

Chen, M., Liu, J., & Skelton, R.E. (2020). Design and control of tensegrity morphing airfoils. Mechanics Research Communications, 103, 103480.
================================================================
How might findings influence the present topic in US Hawks?
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