Aluminum Tube & Gusset Airbike / Legal Eagle / Parasol Thread

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Victor Bravo, Oct 8, 2019.

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  1. Oct 28, 2019 #261

    ScaleBirdsScott

    ScaleBirdsScott

    ScaleBirdsScott

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    The little 3V is exactly why I'm interested in the idea of a fun little T&G type, UL style bird.

    There's other options; the Polini is about half the weight and all.

    But the idea of sticking a little high-wing Legal Eagle type hot rod in the garage with a 3V swinging on the front seems quite cool.
     
  2. Oct 28, 2019 #262

    litespeed

    litespeed

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    A great example of compression of the aircraft to take the impulse loads of sudden impact.

    It collapsed all structures and took the big G loads away from the body of the pilot. The main structure of the cockpit appears to have remained mainly intact but closeups would be needed to see.

    Ideally I would have a bit more strength than these Airdromes have built in, but that is easy to do for a much stronger cockpit. This video shows the beauty of tube and gusset alloy, light, cheap and strong but compressible when it goes wrong.

    Because of the short nose of the Airdrome, it has limited compression room. Other designs can design in much more room for the compression and safety cell.

    How would he have faired in a steel tube version of the same aircraft?

    I reckon worse by far- the steel fuselage has a lot more strength in areas that stop it compressing and shed G loads of impact. So I expect more G would have been transmitted to the poor pilot.

    Ideally every part of the aircraft, except the soft mushy human inside and his cockpit- should be disposable in a crash, all just part of crush structure. This is where overbuilding structures is the enemy, sure it must exceed any expected flight loads and heavy landing, but bar the cockpit, no more.

    Any extra strength just reduces the ability to take away g loads from the crash impulse. Shedding wings, tailplanes, landing gear, crushing firewall forward items etc all help keep you alive.

    This video gives a lot to learn about making a safe strong tube and gusset aircraft. We need to design for the extra space for compressable safety structures and that includes for the seat area to save on spinal injury.

    Good design does not have to be heavy or difficult, just done with safety in mind when the earth rises to smack you in the face. Or a **** Ferris wheel decides you stop you like King Kong at 50kts.
    The Morgan that smacked the Ferris wheel would have been like a tree and they not only walked away after been craned down, it was flying again in weeks.

    The Morgan is a Tube and gusset design that is then metal skinned. Extremely strong cockpit, light, cheap and fast to make. And a proven crashworthy design. Would a Vans Rv12 have survived as well- No. A steel and rag ? No.

    If we think carefully about it and design it well, a tube, gusset and skinned as sandwich cockpit is probably the ultimate homebuilt safety structure. Yes in theory a carbon Kevlar tub would be even better but that is big bucks for homebuilt.


    Think about F1 cars- before the modern carbon era, the best were Alloy tube and sheet combinations riveted and bonded where needed. Far better than the steel tubes of earlier designs. Even today a lot of the best sports cars still have a alloy tub. Lotus anyone?

    That WW1 replica was not designed with safety in mind. Think what a designed for survivable crashes design could do. The poor bugger might have walked away, dusted himself off, and drank some champagne toasting to the day he returns the favour. **** Red Baron.
     
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  3. Oct 28, 2019 #263

    litespeed

    litespeed

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    The Verner 3 is a awesome little motor for Tube and Gusset.

    Love the big torque. The heads and cylinders might be industrial ones but which I do not know. They are over 500cc each. So not a single or V twin I know of.

    Cost aside, the perfect motor for a fun machine.
     
  4. Oct 28, 2019 #264

    ScaleBirdsScott

    ScaleBirdsScott

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    All the Verner heads start life intending to go on a Honda GX390. Some of their brethren might end up being drafted onto on some go-fast kart, having to withstand some 6,000 RPM or more for various aggressive bouts of abuse. Meanwhile The Verner-bound heads will get some upgraded valves and take on a bit more of a wallop in the bottom when let out of the stable, but otherwise stand to live a relatively comfortable, highly pampered life; and with a number of mates to boot.
     
  5. Oct 28, 2019 #265

    Victor Bravo

    Victor Bravo

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    My very limited understanding is that the only big issue with the Verner 3 cylinder engines, specifically on the Legal Eagle ultralights, has been the rotational movement ("rocking") due to firing pulse and torque cycle. Les Homan in California reportedly cracked one or two welds at the fuselage upright tube joints under the wing attach.

    So the only additional or "different" work that might need to be done for this engine is a mounting system that can deal with that rotational movement, which I'm guessing is higher amplitude and lower frequency than many other engines. Tube and gusset, using rivets... especially blind rivets... could obviously be more affected by this kind of problem than other types of structure.

    Perhaps some sort of a "lazy susan" bearing or "rotational compliance" movement can be incorporated into the mounting plate, between the engine and the airframe. Roller bearings between two plates? Perhaps there are some kind of clever elastomeric mounts that can absorb this movement.... some part number of Lord mounts, or Barry mounts?? This would quickly get outside of my ability to quantify and mitigate.
     
  6. Oct 28, 2019 #266

    ScaleBirdsScott

    ScaleBirdsScott

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    I've seen Les go through a number of approaches to the engine mount over the last few years. At last Oshkosh he seemed confident he'd gotten it pretty good.

    20190725_182430.jpg

    In his latest video you can see it idling and I'm surprised how little it's shaking now compared to before.

     
  7. Oct 28, 2019 #267

    saini flyer

    saini flyer

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    Are there links to the Morgan sierra being build from start to finish specially with the square tubing? If it indeed takes only 500hrs to "build" Vs the matched hole laser CNC'd RV12 kit to "assemble" at 800 hrs... why not just improve on the manufacturing and "kitting" aspect of the Morgan family. They have a single seat, 2 seater, a 4 seater, a sailplane covering all bases! I genuinely want to know what is missing from them to be widely popular tube & gusset planes?
     
  8. Oct 28, 2019 #268

    FritzW

    FritzW

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    Closest I could find is a youtube video of one under construction.

    Speaking only for myself: The look of the airplane does nothing for me. It's not at all ugly, it just looks like all the other airplanes that look just like it, there's nothing that would make me want to take a second look.
     
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  9. Oct 28, 2019 #269

    ScaleBirdsScott

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    The looks are pretty bog standard for a little SBS LSA-type for sure. But seeing that it's built simply from tube into a stout little box, and has relatively simple wing construction, from the builder's perspective it seems like a good way to get a simple kit built up that at least looks, IMO, fairly normal in the end. So it has that going for it.

    The biggest reason, I bet, that it has't gotten on more in the world is that it comes from Australia and so mostly a matter of exposure. How many have made it off the continent? There isn't enough unique things going for it that someone in the major Northern markets would pay the freight on a relatively unknown design. If a bunch had made or do make it to the US or European markets at some point and conjure a following, the location would be less of an issue for sure.

    But are they popular where they're from? If they are then it should seem that location is a big factor moreso than the design itself.
     
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  10. Oct 28, 2019 #270

    Vigilant1

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    The Morgan designs, to my eye, do look fairly "swoopy" and clean for sheet covered AL construction.

    The Morgan web site indicates many of the designs have welded steel tube construction in the cabin. I'm just repeating what their site says . . .
     
  11. Oct 28, 2019 #271

    saini flyer

    saini flyer

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    I have nothing for or against the morgan look but like some of their claims,
    1. Ease of construction (as Fritz linked to the video...) No welding in the fuselage
    2. The only 4 seater allowing easy derigging of wings in <10 min (yes, the sportsman has folding wings but is ~$200k)
    3. 120knots with a Jabiru carrying 4
    4. LSA equivalent empty weight< 800 lbs empty
    5. 2100 lb gross.... that's a lot of payload (1300lbs). Even the composite MCR4s did not have this
    6. The 28knot stall for 4 seater just sounds funny for the specs but even if it is 45 knots like a LSA, it is commendable.
    I have no idea how many are flying, but their occasional reference on HBA has intrigued me to at least explore the design and fabrication method but dont know where to get a complete build log or even an assembly manual!
     
  12. Oct 29, 2019 #272

    litespeed

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    The Morgan does have a limited amount of welded parts, mainly the spar carrythrough in the cabin.

    It is a very simple part, easy to make and comes with the kit.

    For the size of our market and with the preference for high wing- the Morgan is actually popular with builders.
     
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  13. Nov 2, 2019 #273

    spikews

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    Not to muddy the waters, but the Heath Parasol was a wood frame with brackets that were wire braced. Keeping all the crossmembers & longerons in proper placement. But that was the ones that were part of the 'kit'. Factory used the o/a & steel tube fuselage. Or am I mistaken?
     
  14. Nov 2, 2019 #274

    Aerowerx

    Aerowerx

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    I believe the original Heath Super Parasol was steel tube with gussets. Roofing nails used as rivets. I have a copy of the original 1930s vintage article describing its construction. There is enough information given for an experienced builder to replicate one.

    I have never read that the kit version was wood. Are you confusing it with some of the modern replicas, which are wood?
     
  15. Nov 2, 2019 #275

    TFF

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    I only know about the steel. Stampe biplane is wood and brackets.
     
  16. Nov 3, 2019 #276

    spikews

    spikews

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    No. I was at Fla-Bob airport back about 1974 Working on Steen Skybolt aircraft. and was walking the back line of hangers. I stopped in at Marquart's shop and in the rear of the shop he had a wood fuselage that was held in compression by wires & brackets. No bolts through the wood members. It looked quite old (to me). Ed told me what it was. BTW, different subject, he had an acetylene manufacturing apparatus. He used so much in the A/C repairs it was cheaper to make than buy bottles. That's all I know or think.
     
  17. Nov 3, 2019 #277

    Aerowerx

    Aerowerx

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    And did he say that it was an original Heath Super Parasol from the 1930s? Maybe there were other models that were made of wood.

    From Wikipedia: (my emphasis)
    Note the underlined section. The empennage was wood and wire braced.
     
  18. Nov 3, 2019 #278

    Geraldc

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    The original welded tube fuselages were made from the best available material at the time.
    I am sure that square tubing was not available back then.Maybe someone older tan me would know?So the choices were tube or angle.
     
  19. Nov 4, 2019 #279

    spikews

    spikews

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    No I was not told that it was a SUPER Heath. Just that it was a Heath. Homebuilt. I do remember reading that the fuselages built in the factory were welded steel tube, but not the ones that were for home construction from parts. It was my feeling that he felt it wasn't safe for a home welder to do a safe job on the extra thin steel.
     
  20. Nov 4, 2019 #280

    Aerowerx

    Aerowerx

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    The construction article from the 1930s Modern Mechanix magazine does not use a welded tube fuselage, but tube and gussets.

    The tools required were pliers, screwdriver, hacksaw, hammer, small hand drill, chisel, center punch, and a file. (Winginitt, you get this?)
     

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