[JoeF]

Low cost experimenting with polyethylene tubing for bladders is an option before going to high quality TPU bladder making.
One supplier of the polyethylene tubing:
http://www.uline.com/Grp_43/Poly-Tubing?pricode=WB139&AdKeyword=poly%20tubing

Care to distinguish: "Only lay flat tubing will work when a seamless, pinhole-free tube is required. Slit sealed poly tubing is not as strong and has inherent pinholes."

Consider using flat poly; DIY tubing by using tapes or sealing hot tool (thermal impulse sealer) (takes skill). (hot iron and buffer?).

An often asked question is how to translate lay flat width to diameter and diameter to layflat width.
To calculate lay flat width, multiply diameter X 3.1416 X .5 = layflat width
To calculate diameter, multiply layflat width X .6368 = diameter

Vinyl sheet is another playing-around bladder experimenting material; note the inflated swimming pool toy products using vinyl sheet.
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Bladder-only playing:



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Some airbeam development: JP Aerospace - Airbeam Development, 5.5 psi
http://spacefellowship.com/news/art11134/jp-aerospace-airbeam-development-5-5-psi.html Note: Their experiment was not using compression elements splinted, but only glued seams and ribbon wrapped hooping. Their target was somewhat different from a HG main spar.


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http://www.federalfabrics.com/airbeam-products/

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Splint (compression element) tied to fluid beam. [Do similarly to repair a broken arm or broken tree limb, etc. Ancient art, but a coined term by a tradenamed company has gained some mileage on the tech: Tensairty® ]

[JoeF]

Hang gliders using airbeam main spar(s) that are formed by splint or tensairity techniques
will have options on how to integrate the spars' compression elements.
Knowing the options and pros and cons of those options may be wise and practical preamble to final builds.
In support of such option space, I ask as follows:

How important might it be to bond a compression element (CE) all along the case of the bladdered airbeam? Notice the difference between the several strategies:
== Only connect the CE to the ends of the case.
== Have a pocket in the case that lets the CE be loose longitudinally; slide the CE into the pocket and attached the CE to the ends of the case.
== Have a longitudinally zippered pocket; have the pocket interior surface relative to the CE surface be grabby in some way; place the CE in the pocket and close the zipper; aim to have the result that the CE cannot slide because of the grabby surfaces and the tightness of the pocket when the zipper is closed. This assures that matching stations along the CE do not change relative to stations along the length of the case. Snug fit and no motion difference between points of the CE and points of the case.
== Weld or glue or stitch a CE to the case. This obtains relative station keeping for the CE-case relationship.
== Magnetically set CE to a case that has a magnetic matching part.
== Have CE and case have Velcro matching parts; have the arrangement fully exterior to the case.
== Have CE and case have Velcro matching parts; have the arrangement fully interior to the case.
== Have CE and case have Velcro matching parts; have the arrangement fully interior to a zippered pocket on the case.
== [Feel free to describe other options for integrating the CEs]

Notice that a splinted air beam spar with CEs may have one, two, three, or more CEs integrated in the spar case. Notice that tote strategies will have influence over integration-of-CE-to-case option choice. Will one want CEs coiled separate from packing case and bladder? Will one want CEs coiled while bonded to case? One might have CE choice that is too stiff to conveniently coil under chosen pack specification; perhaps segmented CEs will be preferred in order to reach tote-length choices (say under 5-ft length). So, to keep CE with case or not during tote may lead to choosing a different option. Appreciate in the options that station-keeping of CE points to case position points may be achieved by CEs that are permanently bonded to cases or by CEs unbonded but held firmly with capability of release of CE from case for tote, repair, replacement, substitution, inspection, cleaning, ...

And recall that an airbeam may be with simple chamber or with hybrid chamber; in hybrid chambers there may be two or three or four bladders; there may be a fabric wall interior of the main case of simple or Y or V or W or X or cross walling format; there may be thin plates squeeze by multiple bladders (and those plates may be segmented or coilable for tote; and those thin plates could feature lightening hole patterns). And bladders may be simple or complex; exterior surfaces of bladders may be smooth or textured rough (for various matching-to-interior-of-case dynamics); and there maybe multiple bladders within one case without walling or plates.

Reports of anyone's experiments with airbeams is ever invited.

[JoeF]

Some rough notes from a walk I just took:
Richard Miller noted that reefable spars may one day be important to hang gliding. I think his day is arriving. Again.

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Case? Cases? Spar casing in airbeam complexes and splinted airbeam complexes:

Tree strategy: annual rings. Fill sandwiching; between shell layers. For tote, coil.
Say: three layers along with coilable foam fill.
Un roll the spar shell to 5-ft flat; then along the 5-ft axis roll the wing-span into the 5-ft pack roll; the interior of the pack roll could hold other parts and gear.

How do shell cases react to having a positively inflated bladder at the core? Compare spars with shell-wrap cases against specialized fabric cases.
Notice that CEs (compression elements may be squeezed between core bladders and the casing (either fabric casing or thin-plate shell casing or multiple-wrap thin-shell casing.

Note how more than one 5-ft roll of shell casing may be used, say two. Wrap one to spar shell; then have another to wrap. Note how flexible foam bonded to shell casing could roll up also.

Notice the sandwich effects of foam sandwiching shell casings. TeaseIMAGE#1

How to fix shell casings by hoops when the shell casing is from flat? Maybe have a final net tubing or light fabric of Dacron or Kevlar; having one final outside fixed-diameter tubing could hoop hold secondary shell cases that are from flats. Notice how the secondary split shell cases will be pushed by the core bladder inflation pressures to a diameter to snug up to the diameter of the most external tubing.

Notice how interior secondary shell casings need not fill a full circumference of the hoop diameter of the gross spar; indeed there may be opportunity to tune segments of the span with secondary partial shell. Think aeroelastic needs and shaping needs and aerodynamic needs. Note how sandwiching thin coilable plates with foam will retain the system short-pack tote targets.

Notice the opportunity in the surface texture of coilable flats that roll to be spar shell layers; consider how much sliding is wanted or not wanted. Consider asymmetrical sliding for certain aeroelastic purposes. Smooth and glossy surface? Matte surface? Rough surface? Directionally rough surface. Bias? Interlocking valleys?

Pressurized beams whose walls are sandwiches of thin sheet and foam?
I have not and probably will not master the paper yet unread:Exact, Hierarchical Solutions for Localized Loadings in Isotropic, Laminated, and Sandwich Shells by E. Carrera and G. Giunta

[JoeF]

Different approach to beams is the direction of Lawrence R. Bosch which entails tensioned staying of core parts.
Full story: http://www.captivecolumn.com/default.htm
Copy of patent, circa 1967 US3501880

But note: In 1929 or so, an England-based team seems to be ahead of Bosch and Brown: https://www.google.com/patents/US1798064

Just how Bosch's direction will compare with splinted encased airbearms for HG main-spar purposes is not known.
So far, in competition by splinted tactics in airbeam realms: I am seeing Bosch core material replaced with air and shell-compression elements and his tension members replaced with tensioned cases. Gut blush without proof: tensairity will win for the short-pack HG main spar purposes.

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Explore Adam's skeleton tower: https://www.google.com/patents/US297331, circa year 1881.

Again, I am guessing that splinted compression-elemented encased bladdered airbeams will win over Adam's skeleton tower for the short-pack HG main spar.

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Snelson's Needle Tower is in the spar mix for play. But just how it will play for the HG main spar is still up in the air.
https://tensegrity.wikispaces.com/file/view/Needle_Tower_by_Snelson_photo_by_BAR_photography.jpg
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Piece-together coilable webs for box spars is a direction that one might take to obtain busable 5-ft-pack HG spar.
That is, have webs that assemble at site into box spars or H spars; then fit airfoil shapers from coiled material. Etc.
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In the mix: Deployable truss modules. Piece things together at flight site. Have main HG spar be truss based. Tote the parts.
Various solutions. Triangular cross section could then receive finishing airfoil coilable L.E. ; then canted ribs with tensionsed T.E.. Sock it to finish.
http://www.scielo.br/img/revistas/rem/v67n3/a03fig04.jpg
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https://www.google.com/patents/US1293208 Ryan. Circa 1918.
Spar, rod, tube, pole, mast, and the like. For HG short pak: couplings would be needed. Ryan would be in the family of aluminum tube COTS, CF COTS, etc. Or the mod of Falcon of WW, etc.
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More from Glen Brown:
https://www.google.com/patents/US8141301 See for all images.
My take is that he should have cited Bosch, but apparently did not.
Externally braced inflatable structures
https://patentimages.storage.googleapis.com/US8141301B2/US08141301-20120327-D00000.png
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