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 15, 2019

karmarepair

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I assume this is the Neirrh. I'm pretty impressed, me.

Some of the clusters look like they would be HARD to handle in Tube and gusset; I'm thinking in particular of the joint between the aft Cabane and the upper longeron.

Thoughts?

Last edited: Oct 15, 2019
2. Oct 15, 2019

pwood66889

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The "Big Cluster" behind the 3-longeron frame is indeed a difficulty. It can end up as big as a basket ball! A solution is to extent the tube on top past the wings, LePelican style. And there are franes I have seen where there is a triangle behind the pilot and a pentagon in front.

3. Oct 15, 2019

FritzW

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If you look close there aren't that many parts, and a lot of those are duplicates.

4. Oct 15, 2019

FritzW

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...as I slide my chair out of the way and bust a beer bottle on the edge of the table. I'm sure you meant Neirrh instead of Nanni lol

The hard part about that cluster is getting to it with a torch, you need three elbows on each arm. ...and have eyes that don't need bifocals.

I think it could be pretty easy with T&G but it'd take a little machine work. Which wouldn't be a problem if a CNC machine was involved in the rest of the design anyway.

5. Oct 15, 2019

Bill-Higdon

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The high wing Longster also was built this way

6. Oct 15, 2019

karmarepair

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Hmm. I'm looking at my copy of the 1933 Flying Manual, and Henderson Longster is square until the first station aft of the pilot. And the "baseball" cluster is the intersection of 8 tubes! It's shown gusseted, in steel, pinned and brazed. It also uses a Pratt/Howe truss with verticals vice the Warren truss Fritz is using. That MAY make gusset design easier.

7. Oct 15, 2019

karmarepair

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Corrected. And make sure and bust the bottle with your stroke down and away from the edge of the table, not straight down. Better you don't know how I know.

I'm sure you could work it out, but I'm skeptical. I'm thinking LAYERS of overlapping gussets on that joint. Any two tubes must form a plane. Long could do things in steel on the Longster on his gussets aluminum will not stand for.

8. Oct 15, 2019

Victor Bravo

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We can compare the fuselage from the Nierrh to a four longeron Baby Ace fuselage, and see the difference in the complexity of the clusters...

It looks to me like the four longeron system may have a couple more tubes in the parts count, but the clusters seem less difficult, since some portion of even the more complex clusters can be done while the sides are flat on a building table.

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9. Oct 15, 2019

BJC

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BINGO. The key to so many things about flying is learning where to look. Same thing goes for welding, and, as you said, being able to see clearly is essential.

BJC

10. Oct 15, 2019

karmarepair

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Some notes on the Texas Parasol. First, what's wrong with it is NOT the fuselage, although there were quibbles about rivets (see http://www3.sympatico.ca/murray.j/rivets.htm) For details on what IS wrong with the cabanes and the wings, see http://www.raa.ca/magazine_pdf/Sept-Oct-12 Lowres 2.pdf

The fuselage is mostly constructed of 3/4 x 1/8 6061-T6 Angle. As a FIRST ORDER approximation, the nearest square tubing in WEIGHT per linear foot (.2) is .75" by .062 wall. ROUND tubing that diameter and wall thickness runs .165#/foot. The original angle design did NOT reduce longeron size proceeding aft to the tailplane. Just going to round .062 tubing would cut at least 10 lbs off the fuselage weight.

I was thinking the gussets could be just circles of sheet. Drill to suit, or perhaps punch them (with a Roper Whitney punch and a template) to suit any of the intersection angles the truss requires.

Rivets - Cherry N and Avex rivets in Stainless LOOK like they have the shear strength of an aluminum driven rivet (and the Texas Parasol used either TWO 1/8" or ONE 5/32" driven rivet per joint), but their fatigue resistance is poor and part of the reason is they don't retain their mandrels, and even if they DID, the mandel does NOT extend past the shear plane of the fastened sheets. And they don't compress the sheets together as well as a driven rivet.

I'd like to try these https://www.vintagetrailersupply.co..._90siPnOyjewCGccckvtGS9Wpz4JNHf0aAuRKEALw_wcB . The mandrel breaks ABOVE the manufactured head, and you trim them down. Shear numbers are great, and likely to stay that way. Better than anything cheaper (ss pops same size =$.14 ea qty 100), cheaper ($ .30 ea) than anything better (Cherry max <which needs special tooling> $.60 - .80 ea). Standard AN rivets are about$.03 ea for comparison.

Graham Lee, just before he died, used his construction style on a cute little runabout, the Miranda, which to my knowledge has never been completed, although forums show several projects started. I've long been intrigued by it, and I think it would suit one one of the larger 2 cylinder conversions, perhaps a Kohler Command Pro CH 750 (747cc) or 680 (674cc) running an Ace redrive (plane is designed around a BIG prop for such a little plane). https://www.nieuports.com/copy-of-sopwith

11. Oct 15, 2019

karmarepair

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12. Oct 15, 2019

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VB Here is the Skylite Fuselage which is also a Parasol. Just needs to be increased in size 15% or so to get it out of the ultralight category an into using the DP1 engine. Tube size changes as well, but with tube and gusset it will be a new build anyhow.. Im just at the other end of the airport may as well start with this and I give you the plans....

13. Oct 15, 2019

TFF

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Three or four tube depends on what you can give up on weight as much as ease. A Legal Eagle if built light should come out ten pounds under the 103 weight. Looked at differently , the average builder has a free ten pounds to glob glue and paint on before being overweight. The cluster at the back of the LE could be split into more than one point. Slight different look but your not preserving the look of a Spitfire.

On welding, people saying they can’t weld, are you saying the joints fall apart or just don’t look pretty? Most welding in the homebuilt world did not look pretty until about ten to fifteen years ago when only professional welders took over building welded planes. It really has made a mess of the thought process. Pretty is great, but the job is melting two pieces of metal together. If it’s strong , it’s strong. Any real welded homebuilt airplane done by an amateur, shows a progression of skill. It is one of the keys of a real amateur built airplane. Badge of honor if you will.

As for angle or round. If the angle structure never can make it to the point of twist, it should be a non issue. Debating tube over angle just means different engineering magic was performed. Picking like or dislike on bad engineering makes no sense. Rivet designed structures design the rivet to be the weak link by a few pounds of strength. The rivets are supposed to give and be replaced without damaging the other structures. An out of the ordinary hard landing having rivets go before tubes is what is supposed to happen. It might suck to cut fabric to get there to fix, but if the margins are right , you should not have to replace the tubes. Now if you go and fly twenty more times, you get what you pay for when it eats the rivet holes out. Wonder why it collapsed that last flight.

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14. Oct 15, 2019

Victor Bravo

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Other folks here with formal training can feel free to correct me, but I do believe I have learned that aircraft riveted joints should be designed for "bearing failure" of the base metal sheet/tube and NOT "shear failure" of the fastener. Shear failure means that when the load reaches a certain point the first rivet fails, which puts the same total load on a fewer number of rivets, so the second rivet fails sooner than the first, which puts the load on even fewer rivets and then the third rivet fails really fast, and the structure "un-zips" almost instantly.

As I said, anyone who has the education to verify or contradict this, please do so ASAP

15. Oct 15, 2019

Victor Bravo

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Yes, circular shaped "universal gussets" was something we discussed on this thread already, and I believe that there is some merit tot his.

16. Oct 15, 2019

erkki67

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2 - 2,5 D rivet diameter edge distance, 4 -6 D rivet diameter stance. A row of min 4 blind fasteners is a good start. Rivet diameter is 3 t of the thinnest component to be clamped, or next bigger suitable diameter available.

17. Oct 15, 2019

FritzW

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This started out as a high wing coupe but turned into a Sportster along the way...

Carlson spars, Sportster gear, (havent drawn the rear spar fittings yet), the wings could fold but it'd be a pain.

The exhaust ring fits. Painting the speed ring and case fairing candy apple red should add about 10 kts.

18. Oct 15, 2019

Pops

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Has to be a Coupe.
My first model airplane was a Cleveland 32" wingspan kit of a Clip Wing Monocoupe with I was 8 years old that I received for my birthday. I am still in love with that aircraft.
I was at an airshow when I was 15 years old and got to talk to the pilot of this Monocoupe for a while after he landed because of loosing a fuel cap while doing rolls.

https://airandspace.si.edu/collection-objects/monocoupe-110-special

19. Oct 15, 2019

plncraze

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Pops, was the pilot of the Monocoupe the same guy who did the handcuffed acrobatic routine?
And who is going to respond to VB's comment about loads in a fitting? I keep thinking "peel" like in composites when seeing this fittings with all the rivets.

20. Oct 15, 2019

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