[JoeF]

Making Splinted Encased Air Beams with an eye to making hang gliders:

A renaissance of interest in an ancient method brought forth a company's neologism of "tensairity" to describe a fluid-pressurized envelope that is enhanced by splinting a compression element with cables or the like. Recreational hang gliders might develop skills in making tensairity beams for use as main wing spars or rib elements or other structural elements.

The compression elements may be coilable or segmented; also, a compression element might even be a fluid encased. The main airbeam might be porous itself; or the airbeam might be a combination of a case that could be porous and a bladder for inflating; the bladder may be made to be slightly larger than the stressed case in order to have the bladder not stressed in inflation. Valving is to be attended to. The amount of pressurization is to be managed. Pumps for inflation is part of the deal. Deflation is in the play. Connecting splinting cables or wires or webs or cords to the compression element(s) is done appropriately. Pocketing the compression element or bonding or joining the compression element(s) to the case is to be specified. Constructions may be accomplished within various budgets depending on choices of materials. Reports of constructions are invited.

Consider compression elements interior of the case, but exterior of the interior non-porous bladder when using the case-and-bladder system. Consider this for the pressing that will occur: bladder pressing compression element against the case's interior surface.

Shapes: Cigar, cylindrical, spindle, complex

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.468.8863&rep=rep1&type=pdf
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Keder

[JoeF]

Full description IS NOT in the below laconic description BELOW:
Two Mylar flats.
Bond castled rubberized fabric loops to each edge of each of the flats, but be sure to jog the castles differently on the two flats so they gear-mesh; the castled edges will permit insertion of a hinging compression element; piano hinge style; but option of fabric tunnel already joining two flats (then force compression element in tunnel(some sizing may permit keeping compression member in tunnel while coiling total assembly to short pack)). Marry the two flats after laying bladder between the two flats. Insert the two compression elements. Inflate the bladder to cause the two flats to obtain cylindrical or conical shell (depending on pattern of the flats). Size the Mylar flats per needs; valve and pressurized bladder per needs. Consider splinting cables per needs.
Above description IS NOT COMPLETE. One skilled in the attending arts probably could fulfill the making of the airbeam along the method laconically placed above.
Intent is related to a drive for busable packs at 5 ft or less. Notice that compression elements might be coilable or segmentable. Notice that the Mylar flats could be coilable for short pack (or segmented with additional cares). Such airbeam could be a main spar for a HG; or could be one of several spars for a HG wing. Or other beam in a hang glider. Or rib form.

What is said to be "Mylar" could be substituted by other thin-plate materials, even composites. Target: coilable flats or segmented flats for eventual 5-ft-or-less HG packs for recreational pilots for niche activity (wing running, ground skimming, conservative sled hang gliding, etc. (proof safety margins in designs according to one's wishes).
JpF
Target: Later have very complete description with examples and test results.

One version: Both flats married with rubberized fabric hinge (not castled, but simply two-layered permanently joined to both flats) with compression element already inserted; coil the entire assembly for tote short pack; consider coil radius to allow pilot wearing the coiled assembly around pilot's torso. The deflated bladder could remain inside the married flats. The two compression elements stay in the pocket or tunnel of the rubberized fabric hinge. Coil radius will be limited by the choice of compression elements and shelling flats.

Alternative: Rubberized fabric hinge with notches: then thread the compression element in and out of the notches. Tease image

Alternative: Have compression member be two-part and clamping the two shelling flats. Have still two compression members, even if each is a two-part assembly.

Alternative: Double keder. TeaseImage1 for double-purposed compression element and connector TeaseImage2 for keder edging thin shelling plates

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[JoeF]

Connector for the long spar flats. Connector has chamber for compression elements.

Connector for the long spar flats. Connector has chamber for compression elements.

SparFlatsConnectStrip.jpg (54.91 KiB) Viewed 6448 times

It is key that the upper surface and lower surface be sewn, as the compression elements during inflation of the spar bladder will tend to spread the connector's upper surface away from the connector's lower surface. The sewing will prevent the disruption of the bond of the connect with the spar flats.

The left and right flaps of the connecter will saddle the spar flats and be bonded to the spar flats.

WR: wing running Get fit for GS and HG WR may advance to hops and flatland hang glide take offs and landings. Safe-Splat arrangements are highly recommended.
GS: ground skimming
HG: hang gliding
SS: Safe-splat arrangement is highly recommended for WR, GS, and HG, no matter the skill or mastery level of the pilots. It takes as little as one unsafe splat to ruin a life.

[Frank Colver]

Rubberized fabric is heavy. Why not urethane coated nylon or the fabric I have written about?

Frank

[JoeF]

Hi Frank,

tensairity.GIF (6.03 KiB) Viewed 6435 times

The connector is a small part of the spar casing, not the full casing. The rubberized surface for the connector is not for holding air, but for a friction grabbing of a tensairity element. So. the mention is not competing with the material you have mentioned and descirbed. The bladder intended would be non-fabric polyurethane (TPU) as used in LEI power kites (leading-edge inflated). See: http://drtuba.eu/services/replacement-kite-bladders-valves.html
Your attention on one-piece air beam is in another ballpark where the airtightness material is bonded to fabric. Such family of air beams are used in the hull you so enjoy. Such may be explored in combination with the splinted enhacement. Result then may be compared with results from the family of air beams that keep the casement (can be non-porous) separate from the interior bladder; and then also enhanced with cabled compression element.

The compression element is a small portion of the circumference of the splinted air beam.

The connector joins two or three flats of casing; the casing need not be air tight when the bladder is set to provide the air tightness. The deal with the separation of roles for the two parts: case and bladder --involves several matters: 1. Abrasion of the casing does not hurt air tightness, as the casing is not playing air-tightness role. 2. The choices for casing may be altered while keeping the same bladder; the choices of casing allows experimentation over a range of casings and tapers without having to concern with air tightness: any fabric, any thin film, any thin plate. 3. The space between the bladder and case may be used to squeeze or hold tensairity/splint spanwise compression elements that will be cabled strategically to utilized the airbeam's girth and inflation. The bladder is ever to be oversized; this prevent stressing the bladder while the bladder inflates and presses the limiting form of the casing; this is very different from using integrated airtightness bonded to a fabric, as when the integrated fabric is stressed from inflation, then too the embedded airtightness material is stressed and stretched; and when abrasion occurs on the integrated fabric, one is eating away at the air-tightness deal. Some hang gliders will be built using both families of airbeams with and without the compression elements and splinting cabling of the airbeams.
Teasing photo:
http://media.bestkiteboarding.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/b/l/bladder_slider.jpg

http://i01.i.aliimg.com/photo/v0/60018401091/TPU_film_for_air_kite_bladder.jpg
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Recalling a version that adds a carbon-fiber coilable veneer whilst using two separate bladders to squeeze the veneer.

sketchAirBeamTwoBladdersWebCombinedSplintsCabled.png (9.73 KiB) Viewed 6435 times

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My recent posts above in this topic have had a focus on casings that may add a "shelling" role to a significant degree besides the tensairity splinting deal. Perhaps mining all three methods: shelling, tensarity/(splinting compression members), and squeezed CF interior web. Targets: short pack and effect strong-enough spar (per niche HG activity).

[JoeF]

I take some naps and wake with further alternatives on connecting things and holding compression members:
Here is today's which does not use sewing. The following has a potential of being lower mass that some of the other above noted connectors.
The following also permits highly dedicated direction for the connector parts; hence I used the word belting to give the focus on having the little fabric hinge connectors be with dominant fibers in the belting direction. Though the drawing looks like a zipper, it is not a zipper. The orang flats are wing-span long. The green tabs are fabric bonded permanently to the orange spar flats.

NonSewCase.jpg (55.11 KiB) Viewed 6426 times

[JoeF]

The following patent instruction is important in itself for some types of airbeams; but notice that the instruction is not about using axial compression elements coupled with splinting cables or webbing; however the "axial fiber bundles" begin to approximate axial compression members for resisting bending and buckling of the airbeams. The following patent's instruction is in the family of airbeam options. But what Glen and his partner instructs is fertile ground for some anticipated HG-spar options. I anticipate combining Glen's instruction with other airbeam technology (interior walls, tensairity compression elements stayed with cables or webbing, and shelling flats).

One of the patentees, at least, Glen J. Brown has a hang glider background; and he also worked closely in industrial airbeam matters with the hang glider pioneer Roy Haggard of UP Comet design fame in mid 1970s.
Some background on Glen: http://www.zzipper.com/about.php

https://www.google.com/patents/US5735083

Some terms in the patent:
spar braid
tri-axial braid
stripes
braided fiber structure
pre-wrinkle stiffness against bending

Some clips:
"A braid with three or more axial fiber bundles will resist bending about all axes."
"higher wrinkle onset moment and damage-free buckling with light-weight construction."

US5735083clipFig2.JPG (54.03 KiB) Viewed 6420 times

[JoeF]

BLADDER plays:
Low-cost quick leaky bladders for experiments?
Before going to quality TPU bladders, consider playing with low-cost polyethelene tube material. Even avoid installing neat valves by manually pinching the ends of such tubing and holding the pinch with whipping; perhaps pinch a soda-bottle top and use the cap for inflating the tube.

http://www.greatampack.com/products-page/film/tubing/

Consider wiping the interior of the low-cost polyethelene tubing with a silicon pin-hole sealing fluid to see if some pin holes stop. Experiments do not need the bladder to hold air perfectly or for a long time. Recall that the bladder is to remain overersized relative to the airbeam case; such keeps the bladder from being stressed except in minor compression of its film thickness; that is, the bladder is not to know stretch during inflation; rather, the case is to get stressed and stretched some; but the case may remain porous material or not.
http://www.csmonitor.com/var/ezflow_site/storage/images/media/images/2008/1113/p06s01-wosc.html/oballoon_p1.jpg/6313955-1-eng-US/OBALLOON_P1.jpg_full_600.jpg

[Frank Colver]

Joe, I should have mentioned, when writing about the packrafts, that they also use airtight zippers so that the tubes can be opened before inflation to insert camping supplies. I didn't get those on my boat because I didn't have need for storing inside the boat.

However, I mention this to you and others who may not have been aware that airtight zippers can be purchased for inflatable structures. This is something else you can consider in "brainstorming" design ideas. It turns out that they have been available for quite some time but I didn't know such things existed until Alpacka Raft started using them. There is no problem with leakage from these zippers.

Frank

[JoeF]

Thanks, Frank.
Topic worthy: airtight zippers with eye on HG
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I asked BobK to edit my post just above Frank's. The edit correction may take a few days. TIA.
I intended the phrase to be:
Recall that the bladder is to remain OVERsized relative to the airbeam case;