Steve just posted in Davis' forum a quality description about sail matters:
Steve Pearson wrote:Re: HG Sail UV protection: 303 Aerospace Protectant Post by Steve Pearson » Sat, Nov 05 2022, 04:07:20 pm=
Woven fabric is relatively stiff in the orthogonal orientation of the fibers - the warp (long axis) and fill (short axis) - but much-much stretchier on the diagonal (bias). Sailcloth is engineered to minimize the stretch and maximize stability on all axes. That is achieved by minimizing yarn crimp, creating as tight a weave as possible, and binding the yarns together with resin. All of this improves structural performance and makes the woven structure closer to a film-type structure with isotropic structural properties but with a corresponding loss of tear strength. Some advanced woven fabrics offset this loss of tear strength with ripstop and other specialty weaves. Lower performance and less expensive fabrics have relatively higher bias stretch but it's basically impossible to control the low wing twist required for good perfomance with a stretchy bias. When you look at an old glider with a lot of twist, that's the result of the resin breaking down and the sailcloth being unable to resist high tension. AP303 lubricates the yarns and compromises the resin structure resulting in higher bias stretch and corresponding improved tear strength as the yarns can deform into bundles creating a rip-stop.
Zippers in hang glider sails? Common reasons for placing some zippers in some hang glider sails: Join left side wing to right side wing. Allow packing to happen Get access to parts and enable visual inspection ________ what else am I missing?
Uncommon possible uses of zippers in hang glider sails? Experimental changeouts of patches to explore aerodynamic matters. Explore segmenting sails for packing purposes Changeout sections of sails for advertising purposes Enable separating sail from frame for packing What else??---------___________________
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Temporary or permanent cladding of nets for HG sails? Have a mesh of about 10 cm for a net made of Dyneema string; perhaps tie a triangular meshed net.
Cover the HG with the net. Clad the individual net holes with various materials. Some choices of materials: aluminum foil, discarded plastic bag patches, paper, treated paper, silk fabric, Mylar,Dacron fabric cuttings from sail-loft floor, polycarbonate film, patches of post-party foil balloons, chicken feathers, treated broad leaves from certain plants, etc. The finished HG would have a resultant performance, like it or leave it.
Samuel Johnson on what is a net wrote:any thing reticulated or decussated, at equal distances, with interstices between the intersections
I would allow unequal distances.
Mesh? Density of holes? Holes per square meter? Holes per lineal meter? Here is one quote, not globally covering the question:
How do you define mesh size? What does mesh size mean? Count the number of openings in one inch of screen (United States mesh size). The number of openings is the mesh size. So a 4-mesh screen means there are four little squares across one linear inch of screen. A 100-mesh screen has 100 openings, and so on.
Holes or openings? HG: fill the holes with various materials to obtain low porosity.
Getting to know nets with an aim to dress a hang glider frame may be a fun adventure in itself. There are many definitions for nets. And various ways to construct a net. Perimeter anchored lines in one direction might be simply overlayed with lines from another direction also perimeter anchored; maybe avoid even "joining" where lines cross; just let the lines be; then clad the holes. Nomenclature will vary depending on the industry using a net. I have personally not yet mastered net nomenclature within any particular industry, so my prose will be immature relative to those who have such mastery. https://en.wikipedia.org/wiki/Triangula ... ar_network https://en.wikipedia.org/wiki/Surface_triangulation
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Tearing behavior of clads for different nets will be something to observe and note. Repairing a 10 cm torn patch: cut and bond a new patch.
Why? Well, HG are always covered with some kind of sail; and every sail is interpretable as a net, even if it is a single hole filled with a no-hole film of plastic. Dacron sailcloth holes might be filled with a resin to fill the tiny tiny holes of a tight weave, or not. In some sense fabrics are nets. But a full range of nets may be explored for HG coverings. Have we missed some opportunity by incomplete explorations? Wrap complex HG shapes; let the net be custom shaped; then patch up the net holes.
What nets are commercial available? What nets can be homemade? When to use three-sided holes and when to use four-sided holes? Flat intersections verses non-flat bumpy intersections, like bumpy knots? Sail smoothness may be shot in the heart by bumpy knots at net intersections.
How to bond patches onto a net? Heat fusion? Glues? Sewing? Soldering? Epoxy? Adhesive tapes? Adhesives? Iron-on? Craft glues? Hook-and-Loop? Super glue? Press-fit groove over the net's string? ??
Incomplete nets? Consider just a set of parallel strings from the HG's LE to the HG's TE. Say the lines are 5 cm apart from each other. Have no other lines traversing the parallel lines. In some sense the arrangement results in a kind of incomplete net, until one lets the LE and TE be the traverse members; then the mesh size or hole size of the net consist of very long high aspect ratio holes. Then consider patching those holes with varies ribbons of plastic or fibrous textiles, etc. Such a sail has not the ripstop of net traverse lines. Tearing might occur easily from LE to TE. Sail flight loading will show a bumpy result. What would be the aerodynamics of such a sail? Any takers on this? Maybe not. Next: Analyze spanwise parallel lines of ribbon-fill; results?
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Descending nets? Levels of ripstop? Line weights and line densities change in a descending order. HG frame is first order; then have very-large-holed net. Then fill the holes with a subnet that has smaller holes; the subnet's lines are less heavy. But then in the smaller holes have sub-sub nets of thinner lines. When the holes of sub-sub-sub-...-sub nets are a certain size, then patch those tiny holes with very-low mass non-porous fill. Judiciously designed, could descending nets be super strong, super tear-resistant, but of very low mass? Someone do the math! Optimum sizing of the descending net structure and fill choices? Masters thesis?
Knotless netting? Net failure modes? HG project reports? Raschel machine? Fishing nets Sports nets Loft nets Hammock nets Safety netting Nets laminated to nets? Laminates with netting as an element or two Braided netting Molded netting Polyethylene netting Mosquito netting IMAGE Heafy mosquito netting Bug netting Floor nets Trellis netting https://www.trellisnets.com/ Fencing netting Window netting Divider netting Lifeline netting Hammock floor Scaffolding nets Pool nets Aquaculture nets Framing a lattice Aviary netting Animal netting Zoo netting Amusement park netting Screens Web netting Rope netting Woven netting Non-woven netting Flat web netting DIY nets. DIY laminations with netting as layer or two. Diamond mesh Square mesh Triangle mesh Mist netting Catch netting Holed film? Then fill the holes with other materials. Perforated sheet? Aircraft dope https://en.wikipedia.org/wiki/Aircraft_dope Madapollam https://en.wikipedia.org/wiki/Madapollam https://www.aircraftspruce.com/catalog/ ... fabric.php Ceconite fabric Sailcloth can be seen as a netting with high mesh numbers; but nomenclature usually does not so analyze the scene. Percent open area for mesh describing Nylon netting polyester netting PTFE netting Dyneema netting Metal netting Landfill netting Baseball netting Drag cost of knots in a knotted-net HG sail??? Most netting suppliers: "Sorry, no netting with triangle openings, only square and diamond openings." Mesh and gauge.
You'll often see this symbol, “#” and a number in front of the netting material. Like #21 Poly, or #60 Nylon, for example. That number is the gauge of the net and it refers to the diameter of the twine of the batting cage net. With batting cage netting, the higher the number; the thicker the twine diameter.
Google search with quotation marks: Your search - "netting with triangle openings" - did not match any documents. Same zero: "netting with triangle mesh". Same zero for "nets with triangle mesh" Stretch netting Vented pallet netting Cargo netting Pond netting Panels of netting where the panel shape is triangle https://www.gourock.com/blog/triangle-n ... and-sizes/ One-way perforated window vinyl
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Agtec Clear Greenhouse Film 9 mil Anti-Condensation [not commonly a net; holes essentially are closed ] [probably too heavy for HG sail] Opening shapes: common, uncommon. Common: four edged, six-edged, circular edged for perforated. Uncommon: mix of two-edge and four-edge. More uncommon: three-edged.
Proposed word: Verb: "owl" as in owl it, not owlets!
I propose forming the verb in order to march toward treating a hang glider sail to possibly obtain some owl qualities. How to owl a HG sail? Owl a HG's LE? Owl a HG's TE?
Conclusion for me about the product TriAx Geogrid: 13.1 ft by 246 feet: 115 lb 3223 sq ft for 0.356 lb/sq ft. So 200 sq. ft >>>> 7 lb for HG sail, assume zero for fill of the apertures (holes, openings) and the involved glue. That is heavier than I want for my HG sail. The product has sharp edges; gloves are to be worn when handling the product; such all leads to a "No" for me on its use. Too heavy; logistics: too involved. Apertures are smaller than what might meet my aims.
But a triaxial Dyneema constructed net might do wonders; it appears the net would have to be DIY project. Names for the openings in the net: holes, openings, apertures, deductions, .. Holes can be any size when one makes one's own net.
While you're building, why not recreate these originals in a mini version using very colorful sails of US Hawks design.
Sometime in 1970 at Torrance Beach Cliffs.
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About 1 week after seeing the first bamboo kites, David Cronk came up with this prototype and tested it at Playa Del Rey.
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And the rest is history.
people will ask, "what are these"? . and you could hand them a booklet and say, "come on, I'll show ya". Your camera crew will capture great shots again of all the different body types with smiles on their faces.
Once you get close to a Hang Glider how can you not smile?
Put them in the wind with one,
.
Sometimes you gotta' push the stick forward while you're lookn' at the ground
HG sail surface texture? Slick, super smooth, rough, satin finish, golf-ball texturing, ...? What finish would be optimal? I had a short chat with Artificial Intelligence that gave the following answer on a question:
In low-speed aerodynamics for a sail, a fine satin finish surface may actually be better than a super slick smooth surface for effective sailing. This is because a completely smooth surface can sometimes create a boundary layer that is too thin, causing the air to separate from the surface of the sail and creating turbulence, which can decrease the sail's performance. On the other hand, a slightly rough or textured surface, like a fine satin finish, can help to create a thicker boundary layer, allowing the air to flow more smoothly over the sail's surface and generating more lift. However, the optimal sail surface finish also depends on other factors such as the wind conditions and the sail's shape and material. Sail designers and manufacturers often experiment with various surface finishes and textures to optimize the sail's performance for different sailing conditions.
I wonder how much has been done on seeking the optimal finish for HG sails. And what have birds come up with in this matter?
Thanks Joe, your "deep dive" into this subject and others is truly awesome.
From the Journal of Experimental Biology. For bird wings there is clearly a trade-off between lift and drag performance. Bird wings with low drag generally had low maximum lift coefficients whereas wings with high maximum lift coefficients had high drag coefficients.
In my H0 opinion, that is why the older kingpost gliders and especially the bowsprit's
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are the best of both worlds. I asked my dad once while looking at his 707 wing, "what are those little things coming out of the top of the wing"?, which he said, "those are spoilers, and they try to keep the air, 'stuck' to the wing during flight but add more drag, and the same for the slats and flaps". To me the "clean' wing of the modern Hang Glider has it's draw backs in that they seem faster and harder to land for the novice pilot. "flying like a bird is one thing, but landing like one is a whole different story"
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I think that, automatic "robot" battens and tailfeathers, are the next great invention for HG, and could be retrofitted.
Sometimes you gotta' push the stick forward while you're lookn' at the ground
I am kicking Myself for not have, when the Maker of My Sails Dick Cheney was still in the Business of Making Predator Sails. Well Dick has gone on to do things that are far less of an accomplishment than Making Sails for a Predator. I do not know what DICK IS Doing these Days. But I do know that what Ever Dick is doing for Work is a Far Cry from when He was making Predator Sails One an hope that Dick will once again be Making sails for the Predator!
I just really wish that When Dick was Making Sails that I would have bought one and set it aside.
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Join left side wing to right side wing. 
What else??---------___________________
