[KaiMartin]

• ... each side needs to take about 20 Newtons of drag. This is equivalent to about 2 kg of mass hanging at half the length of the spar.

I'm not familiar with that relationship. Is it a rule of thumb or is there some more explanation that can help show that relationship?

These sentences do a two steps:

1. Convert a force to an equivalent mass given. Consider an object with a mass of 1 kg statically hanging from a thread. The object will pull the thread due to gravity. The precise amount of force depends the circumstances. E.g, it would be a lot less on the moon and 1kg of helium would even pull upward under standard atmospheric conditions. However, if we assume a location on the surface of mother earth and a fairly high density, the 1 kg object will pull on the string with 9.81 Newtons. I only wanted to give a rough estimate. So I rounded the relation to 10 Newtons per kg.
2. For the sake of the argument I'd like to compare drag to a weight hanging from the spar at a single point. Actual drag does not apply to a single point but is distributed with varying strength all along the length of the wing. However, I implicitly simplified the situation by assuming the same amount of drag everywhere. Now I can combine drag portions of the outer wing with a portion of drag from a corresponding position on the inner wing. The torque of all of these pairs with respect to the root of the wing is equivalent to the same force applied to a point at half the spars length.

I hope, this sheds a bit of light on the argument. The relation is kind of an estimate. To me, a weight hanging from a beam is easier to visualize than a continuum of (drag) forces all along the wing.

---<)kaimartin(>---

[JoeF]

As Wing5-Iteration One progresses, some changes are noted:
1. Instead of span of 30 ft, the first iteration will be 20 ft. I will run faster .... Upon seeing how the 20-ft-span Wing5-M1-20 goes, an iteration M2 may have a longer span. The chord is expected to stay the same, so aspect ratios will change. Rib length will be 6 ft; the ribs may be hinged and pocketed; it looks like the forward end of the rib will butt against the spar's compression element. The CE will hold the cavity that will grasp the three kedered edges: two spar-case edges and the mainsail forward edge (wrapping over the CE). The wrap over and the rib pocket will permit the rib front tip to butt against the CE.
2. A very interesting concept is winning focus: "three kedered-edges-in-one rail cavity" that will permit not having a span-wide zipper, and not having to have any hook-and-loop and not having to have True Lock runs. The Eureka moment came a few days ago, reporting now.

ThreeInOneCE.png (8.33 KiB) Viewed 1295 times

[Bob Kuczewski]

KaiMartin,

Thanks for clarifying. I think I was reading more into your earlier explanation than was intended. I thought your midpoint mass example was addressing the buckling aspect of a beam ... and possibly of an inflated beam. I wasn't familiar with buckling equations, and that's why I asked.


Frank,

Thanks for the Porta-Wing reminder from hanggliding.org. The first mention of the Porta-wing here on the U.S. Hawks was Sep 27, 2011 by Joe Faust:

"Differently is the Platz, the Porta-Wing, and other super-sharp LE gliders."

             -   https://ushawks.org/forum/viewtopic.php ... 788&p=2684

Maybe you could cross-referece Joe's U.S. Hawks posts on hanggliding.org ... only joking.




Joe,

Thanks for your continued dedication to building a more compact and portable hang glider. While there are some unique flight capabilities found in modern paragliders, I think most people fly them for their portability and convenience. Making a similarly portable and convenient hang glider would be a great help to the sport ... and might save many lives. Thanks.

[JoeF]

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2AntibucklingRegionConcerns.png (2.73 KiB) Viewed 1277 times

T: tension side where the envelope or spar case material goes into tension during normal gliding.
C: compression side where compression member could aid in anti-buckling of the air beam
Notice
Cantilever airbeam as spar has in gliding mode compression on the skyward line.
But the airbeam spar part between the side flight wire anchor on the beam and the keel has a reversal where the compression side is then earthward line of the airbeam. Matter for careful discussion, this. I have overlooked this matter probably because of the photograph emphasis of a a loaded splinted airbeam supported at the beam tips while people and vehicles stand or park or roll on the upper edge of the airbeam where the compression member is integrated in the airbeam. A hang glider using side wires for rigging changes matter; the outboard section of the airbeam beyond and slightly inboard of the rigging point is in cantilever actin during normal flight loading in glide; in that section buckling of the airbeam is tempted with compression element needed for antibucking and with that compresssion element on the skyward line of the air beam. Different for the spar airbeam section between the side-wire anchor point and the keel; such inboard section is flight loaded with support from two points, thus not cantilever, and thus in need of careful analysis; the lift will tend to bow the section upward at the section's center; and thus the bottom-of-the-spar line will be in compression and thus in need of anti-buckling compression member integration. Describe my new understanding as true or false and give reasons, all invited. This would be an important change for compression-member placement for Wing5 when side-wire rigging is used.

All, contest any errors found in the analysis!

If a full wing using no flight side wires is cantilever-based, the compression member would go from wing tip to wing tip at the skyward line of the full-span air beam. But a HG using side flight wires out-rigged by the queen posts of the TCF (triangle control frame) has outboard wing sections acting in a different manner than the wing section inboard of the rigging point of the side flying wire.

Image study for cantilevered full wing

[JoeF]

Getting bladder-making-testing-repairing experience:
Involving tools and items:
Air pumps
Bladder materials: various thermoplastic films (PVC, TPU, ... ) and other films Tubular bag-making material will be explored; close ends of a length of tubular film.
Rubbing alcohol
Patches
Soldering irons and tips
Bag-sealing machine (hot element)
Adhesives
Thinners
Water tub for testing for leaks
Valves (one-way inflation, deflation)
YouTube ... how to ...
Product descriptions
Experiments and notes
Jigs
Fixtures
Work bench
Electricity
Light
Academic papers from Internet
Safety information
Ventilation
Fire extinguisher
Time
Brain
Notebook
US Hawks community and posts
=================================
Bladders for Wing5 are intended to be larger than the spar cases so that the bladder need not stretch at inflation, but stay only skin compressed.
Sand might be a real demon for Dockweiler bladders. We will see if sand becomes an Achilles Heel in these adventures. Experience is needed.
For Dockweiler-only wings, slow bladder leaks will be tolerable; adequate air pressure need only be extant for short flights.
In-session bladder repairs will not be desired.
Extra bladders for replacement are anticipated.
Up-to-the-minute decision is to have left-wing bladder and right-wing bladder. And first decision is to try fully independent bladders; then later try communicating the two bladders, so that pressure remains equalized.
Valves need to exit the spar case; reinforce the spar around the valve exit points; leave no room for bladder to poke out of the spar case.
Automatic pressure regulation will not be in the first generation of results; such matter will be left for advanced concerns once flight-success maturity is achieved and configurations are well tuned, tested, analyzed, ...
Weight of bladders will recorded and kept in focus as designs roll out.
Comparing bladders will be fun.
Salvaging valves from other inflatables is an optional tactic.
DIY valving is an option.
Defining suppliers and purchase options is a challenge.
Un-cased bladder inflations usually stretch the skin of the bladders; such puts the bladder with strains different from what occurs in using the bladder in a spar case where the bladder is larger than the spar case. The spar case will be stressed with resulting stretch, but the bladder should remain without stretching.
Sand or other foreign matter should be kept out of the spar case interior; that will be a challenge for Dockweiler operations. Potential show stopper!
Bladder-valve positions are not yet determined. Many options. Pros and cons on each position.

Bladder001.png (3.44 KiB) Viewed 1262 times

There are some commercial valves that do both: one-way inflation and then rapid deflation. But two separate valves per function will be explored first.
Kiteboarding wings that use inflated air beams are served by many commercial entities; bladders and valves galore are offered for sale. Bladder repair kits too!
Kite bladders
This is interesting, but minimum orders might not let this occur for me: HERE

[JoeF]

Secondary uses of Wing5 spars? Or ideas from the raft industry?
Maybe use the left spar and right spar to make a cataraft? Fly off land; end flight on water; rotate left wing to right wing to form a cataraft; mainsail up for wind sailing the cataraft?

https://www.saturnrafts.com/13-saturn-cataraft.html

Teasing:

Notice the marriage with the non-inflated tubes.

Fundamental decision:
Consider all the differences between using a two-part system of bladder or air cell with porous spar case and the different situation where the spar case is the non-porous air cell without a second-part bladder. Two directions for Wing5; both directions will eventually be explored. First iteration will be with the two-part system: bladder separate from the spar case.
It is not proven which system will become more satisfactory. There are pros and cons for both directions.

Some attractive things for the two-part system:
One gets to experiment with various bladders
One gets to experiment with various spar cases.
The interior of the spar case may be easily reached for work, sewing, bonding.
There is the guess that expenses might be less for iterations.
There may be the potential of being less massive than the one-part system, but final design choices matter.

Some unattractive aspects of the two-part system:
Sand between the bladder and the spar case.
Two parts instead of one part! Case and bladder. Rather than: case only.

============================
Some teases without any recommendations:
Pair of Inflatable 1.2mm PVC DIY Fishing River Pontoon Raft Boat Float Tubes NEW

===================================

pontoons, pontoon boats, pontoon, fender, tube, inflatable beam, inflatable post, cataraft, air beam, raft, inflatable raft, fender air bag,

=========================


========================
Unbaked:
Inside a porous spar case have say 5 bladders of low diameter; have those bladder air communicating so that one inflation gives air to all 5 at once; the bladders rightly chosen will fill the spar case cavity without having to have bladder skin stretching. Why go to 5 bladders instead of one larger bladder? Perhaps: to use commercial off-the-shelf bladders?
=====================================

One low-cost bladder-making material: bag-making tubular film lay-flat on a roll. Without recommendation tease Here. Shown is too wide for Wing5; type of product comes in may lay-flat widths. Cut off a length; close ends; mount valves. Polyethylene is poor performer for air tightness. TPU is target.
LinkingTeaseNonRec

Teasing:

Tease HERE And HERETOOwithoutRecommendation
=====================
Quick 5 minute experiment:

5in1sameairStuffedFirstExper.jpg (98.48 KiB) Viewed 1253 times

5in1wristhooping.jpg (43.98 KiB) Viewed 1253 times

And

5n1somerelatedlongercoatsleeve.jpg (48.41 KiB) Viewed 1252 times

WrightBackgroun5n1expmt.jpg (37.1 KiB) Viewed 1251 times

[JoeF]

Bladder of weight more than ideal, but might be for experiment:
Obtain backyard swimming pool that has three chambers and three valves. I am not yet knowing diameter of resulting hacked bladders from the product. But since the bladder will be with two runs (though one toridal), then estimate of fit is good.

Cut out the center chamber and have two rings intact. Cut out the floor of the pool. Those rings form a bladder each.
Put a ring of bladder in left wing spar case. Put a ring of bladder in right wing spar case. Cut and reinforce the spar case to allow the valve to appear barely. Inside left wing will be a ring of bladder and thus two runs of bladder having one air. Inflate the ring in the left wing; the two parts of the ring or topological torus will fill the spar case and result in a circular cross-section inflated spar. Do same for the right wing and its topological-torus bladder.

Note: such above-hacked bladders would weigh more than well-designed TPU bladders, to be done in secondary iterations.
blob:

Hacking pool to get two topological tori ready valved bladders.

2ThreeChamberedPoolHackToTwoTopologicalTorusBladders.png (223.83 KiB) Viewed 1249 times

Toridal two-run bladdering is a fresh idea for me: (two or more bladders in one spar case is not new in the art).

ToridalTwoRunOneAirInSparCase.png (8.48 KiB) Viewed 1247 times

Invested (brand : Anbber [of which I have zero experience, so no recommendation]

Order placed, thanks!

Inflatable Swimming Pools, 130"x73"x22" Ultra Full-Sized Inflatable Kiddie Pools, Family Lounge Pools, Family Swimming Pool for Adults, Kids, Babies, Toddlers, Outdoor, Garden, Backyard, for Ages 3+
Brand: Anbber

Pool arrival will be soon enough. I'll now need to get the spar-case tooling, sewing, kedering set-up going ...

==========================================I got excited about the hack and just now purchased a SECOND POOL
of a different make and such will arrive sooner than the above ordered pool:
The below is a bit longer pool. Note that ring holds the width also; such will bring wrinkling; but note that the intent is that the bladder will ever be longitudinally relaxed; the air pressure will compress the skin against the inside of the fabric spar case. Better make the spar cases and compression elements and ribs and struts and X frame and high hat and keel and rigging, etc. soon, as the bladders are arriving! Frank, X center fitting is still to be designed; I anticipate your offer being taken on the part if tooling is compatible; it is to receive four tubes: two kingposts and two queen posts; sandwich plating may not be best or desired; forging is not in our sight; overlap is not wanted; keel-near might be an asset. [ ]

Arriving _______________

JONYJ Inflatable Pool, 150'' x 72'' x 22" Family Full-Sized Inflatable Swimming Pool, Blow Up Pool for Kids, Adults, Toddlers, Oversize Lounge Kiddie Pools for Outdoor, Garden, Backyard

If the second pool second-arriving pool is not cut up for HG, then it could be a swimming therapy pool or storage bin or base for a workbench or pole-lifted shader for yard-time works, or .... But I bet it will be hacked for a HG iteration ...

[JoeF]

The pool bladder hack will give "an adjustable-length bladder" which is an interesting surprise. The same one bladder will be infolded to fit a 10-ft long spar case; but the same bladder will be able to be less infolded to fit a 12-ft spar case; similarly less infolding could have the same bladder fit a 15-ft long spar case.

Reduced resolution copy of this-morning's note on infolding excess bladder material

Aug20BladderHackAndEstCase01500pix.jpg (78.7 KiB) Viewed 1242 times

The valve position will probably be on the aft side of the spar case near the wing tip. This will have the bladder-excess material (that will be infolded) be inboard; hence the mass of that excess material will be inboard. Eventual iterations will not have excess material in their bladders.

As I do not yet know the circumference of the pool-supplied bladder, final decision on iteration-one spar case diameter will wait. Estimate is diameter of inflated spar will between over 12 inches but may go to 15 inches. Birds grow and do not always have same bone diameters.

Various folding-of-toridal-bladder options

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SideOrAtopOptionFoldBladderExcess.jpg (81.74 KiB) Viewed 1240 times

[JoeF]

Wing5 spar section outboard of side-wire rigging point will have compression member effective on top of the spar case. Some visualization may be seen in the photos of Luchinger's test of a tensairty actor as a tensairty cantilever. See: https://www.irbnet.de/daten/iconda/CIB10872.pdf from which I invert the photos indicating that the outboard lift on the spar-wing will be represent by the glob weight in the borrowed photo:

OutboardCEonSkywardTangentPixel555.jpg (91.79 KiB) Viewed 1241 times

Splinted air-beam cantilever as a possible machine actuator via air pressure to have a splinted-air-beam-cantilever actuator (wing morphing).

[JoeF]

An advanced core assembly design option for Wing5-M1 is illustrated:

Wing5coreAug20of2021.png (11.9 KiB) Viewed 1231 times

I have salvage flat plastic strapping that will be placed in an edge hem sewn to the spanwise longitudinal edges of the spar case and mainsail. Two lines of double-sided tape on the two broad faces of the strapping; then stitching will close the hem.

At assembly, the stiffened edge will be stuffed into the grooves made in the CE (compression element). The grooves are slanted to assure that the spar case and the sail edges do not come out of the grooves when the spar bladder is inflated and the aft end of the ribs make the sail taut.

The flat keder straps will extend beyond the CE ends just enough for using the extended part to form an anchor with the end of the CE; anchoring will involve also the straps that are exterior to the spar case.

The foam filler will smooth the airfoil formed by the spar case and sail.

The edge's keder strap is coilable or wrappable for packing and transportation.

The sail in the drawing is the orange line; the groove to hold the sail's kedered edge is the center of the three shown grooves.

In Wing5-M1 there will be just one CE coupler in the left wing and one coupler in the right wing's CE. M1 will be a 20-ft span experiment (high airspeed will be needed for running takeoff). M2 or so will have 24-ft span; then 30-ft span. Mass and satisfactions will begin to dictate span choices. As satisfactions are experienced, materials will be fine tuned. M1 will see some material shortcuts.

The groove for the sail keder strap might have to be angled more acutely than drawn in order to assure that the keder strap does not lift out of the groove; the angle of the sail made with the groove needs to be less than 90 degrees.

The sail keder strap may be set in its groove after the spar is inflated.

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