Is there a cheapest/lightest/simplest wing structure other than aluminium tube and fabric?

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Aesquire

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Filling with foam to reinforce the tubing, reduces that, increases overall strength as well, allowing for fewer, or possibly no cabling, while reducing drag due to cabling. Foam is generally lighter than aluminum and steel.
The Albatross was a minimum mass cable braced design. So in that case no, foam is just dead weight.

But that's an edge case! Will filling a fiberglass or carbon fiber tube with foam make it stronger? Eh. Meh.

It will help hold the broken parts in loose formation, but the foam takes zero strain in any normal sense. The perimeter of composite takes all the load until it fails, and the foam is useless. Sure it's lighter than rock or iron, but so are soap bubbles. Just a waste of money and mass.

Where foam comes into it's own is shaping like ribs under fabric, or even a Rutan full core composite moldless construction. You'd get lighter structure if you used molds and infusion to better optimize resin /fiber ratio.

But that's a LOT of work. Mold-less foam core can be done in a basement or garage with a leveled table and hand tools. There's a lot of hand sanding but making molds takes that too.

The owner/builder of Lionheart said he sanded and filled the fuselage molds until he could see the reflection of the mountains outside his shop without distortion. That's more hand work than a typical Rutan design. He was rewarded by a lovely result, though.

Mike Arnold's videos are great. And the best advice besides those seems to be from the designer of Symmetry. Do each step once, as perfect as you can, so the next takes less work. He put extra effort into making the foam smooth, so irregularities didn't have to be sanded off the composite. He put extra effort into making the layup even, so the finish layer of micro didn't have unnecessary lumps to sand off, & layed one thick enough smooth layer of micro so the final sanding to shape within hundredths was a one time job.

Wish I'd heard that advice before my first lousy glass job. :)
 

J.L. Frusha

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The Albatross was a minimum mass cable braced design. So in that case no, foam is just dead weight.

But that's an edge case! Will filling a fiberglass or carbon fiber tube with foam make it stronger? Eh. Meh.

It will help hold the broken parts in loose formation, but the foam takes zero strain in any normal sense. The perimeter of composite takes all the load until it fails, and the foam is useless. Sure it's lighter than rock or iron, but so are soap bubbles. Just a waste of money and mass.

Where foam comes into it's own is shaping like ribs under fabric, or even a Rutan full core composite moldless construction. You'd get lighter structure if you used molds and infusion to better optimize resin /fiber ratio.

But that's a LOT of work. Mold-less foam core can be done in a basement or garage with a leveled table and hand tools. There's a lot of hand sanding but making molds takes that too.

The owner/builder of Lionheart said he sanded and filled the fuselage molds until he could see the reflection of the mountains outside his shop without distortion. That's more hand work than a typical Rutan design. He was rewarded by a lovely result, though.

Mike Arnold's videos are great. And the best advice besides those seems to be from the designer of Symmetry. Do each step once, as perfect as you can, so the next takes less work. He put extra effort into making the foam smooth, so irregularities didn't have to be sanded off the composite. He put extra effort into making the layup even, so the finish layer of micro didn't have unnecessary lumps to sand off, & layed one thick enough smooth layer of micro so the final sanding to shape within hundredths was a one time job.

Wish I'd heard that advice before my first lousy glass job. :)
Hovey Whing Ding II had a glass reinforced thin-wall aluminum tail boom with internal foam reinforcement. Minus the engine and prop, it weighed in around 110 lbs. Being a conventional LG setup, the tube needed the extra reinforcement to keep from buckling. Slender spars will, too, to minimize weight. Better safe than sorry, IMHO.
 

J.L. Frusha

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Perhaps crash damage would have been less catastrophic, if they had used foam reinforcement...


"Crashes like this were common with the Condor."
1642765955602.png

The Albatross had similar problems which lead Bryan Allen to say "The Albatross has crashed three times in the last 1/2 hour of flight testing. On two the these occasions I have suffered minor injuries... I think that you possibly have not realized that the philosophy of "fly, crash, repair, and fly again" which was used in the early stages of the Condor project is no longer a valid method. The pilot is going to be maimed or killed if this philosophy is used on an aircraft which can so easily be popped up to 30 or 50 ft."

Here you see him jumping clear of the Gossamer Albatross- out the port side where there is no door- when the Albatross has become uncontrollable. This was to keep the impending damage to a minimum. Photo copyright by Don Monroe.




1642766198101.png
 

oriol

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The Gossamer Odissey is worth reading. It tells the story behind Mac Cready pedal powered airplanes.

Speaking from memories. They where testing their prototype in an airfield in where there were also Stearmans, used as cropdusters. The airplane was so light and fragile, that the wing collapsed once because of the Stearman´s slipstream. After that they waited long enough after a Stearman´s took off, before testing their airplane.

Of course safety was a concern for mac Cready and his team. The protos used to fly close to the ground. believe that no one was hurt, during the many hours flying . During the channel cross there was a Zodiac following the Albatross. The aircraft was so draggy and light, that the wind blow it and made it drift. The pilot resisted like a hero until he reached the ground. The airplane limited performances were overcome by the pilot legs and willing.

Aesquire your adventures testing hangliders sounds really inspiring! It feels like hanging out with the Wrights at Kitty hawk.

Thanks Riggerrob for the explanantion about spaceship inflatable modules!

There was a local company that was investing in space tourism with balloons instead of rockets, but I think the project stalled. I do not know if a modern version of the inflatoplane could be more performing and practical than a parafan? It would be cool to have a Part 103 inflatoplane.

Cheers,

Oriol
 
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Riggerrob

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Yup, that was my thought as well, the hardware bill from AS&S would be staggering for turnbuckles alone. If it could be done with pretensioned Dyneema bonded in place without hardware that would be very interesting.
You don't need turnbuckles with braided, core-less suspension line (Dacron, Dyneema, Polyethaline, Dynema, Microline, Kevlar, HDPE, etc.). You can copy a technique from the parachute industry. Loop the running end of a line around a compression strut, then finger-trap the running end of the line into the fixed middle portion, then finger-trap it out and tie a knot. Changing the position of the knot makes it easy to change the length of the line.
Finger-trapping has become the dominant method for splicing suspension lines ever since square parachutes became fashionable more than 40 years ago. A finger-trapped splice is as strong as the original line ... IOW stronger than any other knot or stitching. Once a splice has been finger-trapped, any additional stitching is a mere formality because it only prevents the splice from slipping while it is not loaded. As soon as you load a finger-trapped splice, it will not slip.
I can even teach you a finger-trapping method that requires zero stitching ... but it is not adjustable once completed. See Parachute Labs ...

Oh! And start with pre-stretched suspension line.
Heat-treating - at the cordage mill - also helps stabilize the lines.
 
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J.L. Frusha

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You don't need turnbuckles with braided, core-less suspension line (Dacron, Dyneema, Polyethaline, Dynema, Microline, Kevlar, HDPE, etc.0. You can copy a technique from the parachute industry. Loop the running end of a line around a compression strut, then finger-trap the running end of the line into the fixed middle portion, then finger-trap it out and tie a knot. Changing the position of the knot makes it easy to change the length of the line.

Oh! And start with pre-stretched suspension line.
Heat-treating - at the cordage mill - also helps stabilize the lines.
1642806721216.png
 

Aesquire

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Hovey Whing Ding II had a glass reinforced thin-wall aluminum tail boom with internal foam reinforcement
Well!

the difference between me and those folk who tell you ( insert scam here, you'll know ), is I can be wrong!

Riggerrob is a real pro at this. Good advice. I just got back into parafoils the last couple years, and have to relearn a bunch, especially unlearn old techniques that don't work on the new materials, and old techniques that were verboten on the old stuff, but works on new. Stuff that was a fail on sheathed paracord is SOP in Dyneema unsheathed. "Lark's head knot? Wth is that?" Kinda stuff.

I was trying to explain an original Rogallo kite ( just fabric, no hard stuff ) to a buddy, by taking a square 2x2 yards of ripstop nylon, adding taped loops, then saying, "then you just run lines to make the shape you want under windload" . .. To which he replied "sounds complicated!" ... Uh, yeah. 3 hours later I finally had it trimmed well enough to fly straight. If I'd done the math I'd forgotten from last century, it would have gone quicker. ( mutter mutter it's just fracking triangles! I used to do this all day. Grumble cos of what again? mutter )
 

cluttonfred

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You don't need turnbuckles with braided, core-less suspension line (Dacron, Dyneema, Polyethaline, Dynema, Microline, Kevlar, HDPE, etc.). You can copy a technique from the parachute industry.
For anyone like me who needs pictures….

1642844058687.png

Riggerrob, I would love to see an example of the adjustable version you described.
 

henryk

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Looks about like a Princeton Sailwing...
-yes,
but in my solution LE is tubular (construction,loading) wit "D" shape formed via spring foil insert into upper pocket...(todays hang gliders like).

+ it is possible to involve LE tube autriggers,
as Rupert Sweet-Escott was made in His VOYAGER hang glider

+ "Sliding Ribs "
His patent...

 
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cluttonfred

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Keep in mind that Oratex uses heat-activated glue, essentially tiny beads of high-temp hot glue in suspension heated with a 100°C iron, so while I’m not 100% sure I don’t think it can be applied directly over most types of foam.
 
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