Hovey Delta Bird

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Dana

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Eddy current will find cracks but it won't tell you anything about heat treat.

It won't be T0. Welding brings it down to T0 initially, but it then naturally ages and recovers some strength, back to, IIRC, the equivalent of T4 or so. But in a tube structure, the critical failure mode is usually buckling in the middle of the tube so it may not be an issue. If the main wing attach fittings or such are welded on when they're supposed to be riveted then that may be more of a concern.

Dana
 

TFF

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You can distinguish all the alloys of aluminum and treat with eddy current. It's how they test ball bearings being manufactured. Goes through a ring, good keeps rolling, bad gets kicked. I had to be tested yearly when I worked at the airline. It's not how we used it but the airline had an instructor from here http://www.ridgewater.edu/programs-and-majors/technical-programs/nondestructive-testing/Pages/default.aspx give initial and recurrent classes. He made you do it all to pass. He was the guy and so is that school. They came up with the testing of 737 skin so Hawaii would have less convertible airliners. Help fix the Harley manufacturing during the AMF days testing for porosity. It was always a good time when he came in.
 

Dana

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Eddy current testing, at least in my experience (we use it where I work to find malformed parts on the production line) is very sensitive to the part shape, which is why it's great for finding discontinuities (e.g. cracks). I can see that it might be able to detect alloy differences in identically shaped parts, but absent a reference part of the exact same shape? But the system we use is older, the output is a swirly graph for each part and the good/bad determination is a set of areas the curve must pass through and others the curve must not pass through... all experimentally determined by running known good and bad parts.

Dana
 

12notes

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It won't be T0. Welding brings it down to T0 initially, but it then naturally ages and recovers some strength, back to, IIRC, the equivalent of T4 or so. But in a tube structure, the critical failure mode is usually buckling in the middle of the tube so it may not be an issue. If the main wing attach fittings or such are welded on when they're supposed to be riveted then that may be more of a concern.
The wing attach tubes going across the frame are welded, but have two smaller diameter tubes inside of them which are screwed in along the length. I would think this is probably strong enough. However, I'm more concerned about the wings themselves.
Looking at the pictures, the front and rear wing spars are welded ladder structures with a couple of diagonals. The ribs and aileron hinges are riveted on to them. This would seem to make the wings much more prone to folding if it wasn't treated properly.
 

TFF

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Most of my work is with pencil probes. Literally draw the probe across the part like coloring a picture. In manufacturing most machines are set to do one job or only designed for one. I was taught to program it for any job. The instructor would bring in the scope of probes; we only had ones for the jobs we would do. We had nice machines, but the instructor woul bring in a half dozen different types and brands we had to set up. I never got qualified for ultrasonic. I did have penetrant and mag particle.
 

BJC

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FWIW, I am very leery of welded aluminum in primary structure. I could refer you to six or eight ultralight designers who used it, but they are all dead.


BJC
 

12notes

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I am feeling less than confident in the aircraft. Unless I can find some proof that this was a designed-to-be-welded frame made by a kit manufacturer, this airframe may just be a test stand for the engine. Even if I could get this heat treated, I'll be wondering what other builder-designed "improvements" I might find.

If the engine is good, I may just build something else around it. A Hummelbird is looking tempting right now.
 

Tom H

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I am feeling less than confident in the aircraft. Unless I can find some proof that this was a designed-to-be-welded frame made by a kit manufacturer, this airframe may just be a test stand for the engine. Even if I could get this heat treated, I'll be wondering what other builder-designed "improvements" I might find.

If the engine is good, I may just build something else around it. A Hummelbird is looking tempting right now.
Patrick, first thing that I thought about was just to gusset and rivet the joints. I know you picked up some extra weight from the welding that you don't need. The rivets for the gussets may be far enough away from the weld joints to get back into T6 material?

Tom H
 
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Victor Bravo

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The only Hummel aircraft I was ever close to (Ultra-Cruiser) did not radiate an aura of "robustness" by any means. You could be stepping out of the pot and into the fire.
 

12notes

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Hooked up the engine yesterday, it fired and ran on the first blade. So I have an engine needing a project. It's the wrong prop, though, a 58x28 Tennessee Prop, it seems everyone recommends a 54x24 prop for the 1/2 VW. But hey, free engine.

I'm not rebuilding the Hovey Delta Bird. I just won't feel comfortable with anything short of completely rebuilding the airframe, and that's too much work to me for a plane that flies at 45mph.

Not really finding any other plans for the 1/2 VW I'm interested in other than the Hummel Bird. I need to find a local one to see how I fit.
 

TFF

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There was a Hummel at OSH flying with the other ULs. It was eating them up speed wise. No rocket, but it was probably doing 5 mph faster than anything else in the air and either having to get out of line by circling or pass and cut off the slower planes. They were all doing the turn to final over my campsite.
 

Dana

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The Hummel Ultracruiser is pretty cool too...

[video=youtube_share;ey_Re9zJ2QE]https://youtu.be/ey_Re9zJ2QE[/video]

Dana
 

choppergirl

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So if you giving up on the Delta Bird from paranoia, are you giving it away free?

If someone offers an aircraft for free, I say yes and figure out the details later. :ban:

Weld joints schmeld joints don't matter to me if it's a pilotless drone attack aircraft...

Hummelbird, a can of worms just like any other gravity defying contraption...
 

12notes

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Discovering a issue in the wings of a plane that make them much weaker than designed exactly at the points where the most strength is required and refusing to fly it is far from paranoia, particularly when the frame protecting me also suffers the same problem. Although I don't have a problem with flying an experimental category aircraft, I do not wish to fly an actual experiment in structural integrity.

I would give it away to someone who was willing to sign an agreement that it is never to be flown, which puts you out of the running, unfortunately. Pilotless planes can still cause damage if the wings fold. Maybe that's what you meant by "attack aircraft". I can't knowingly allow this aircraft to fly, since I know there's a problem with the structure. If something bad happens, I don't have a legally defensible position.

I only found 12 Hummel Birds in the NTSB database, one had a problem with the lifting body and canard flipping it which makes me doubt it's even related to the Hummel Bird, and one was a Hummel Ultra Cruiser which hit trees (I'm pretty sure another was, it's listed as an Ultralight, which the Hummel Bird is not), so that's at most 10 Hummel Bird accidents. 5 were engine out off field landings - 1 fatal. The fatal one was someone who bought a previously built plane, changed the engine and was also on his first flight. The other four engine outs had no injuries, including one that flipped. Another non-injury report was a ground loop on landing. One with serious injuries due to a stall-spin on a go-around attempt (this was listed as an ultralight). 1 was the 1st flight loss of control incident you linked to, which also stated "Examination of the airplane confirmed flight control continuity, and did not reveal any pre-impact mechanical malfunctions with the airframe or engine", so it looks like pilot induced oscillations into a stall. 1 was between 31 and 58 pounds over gross weight, depending on fuel load, and porpoised into a fatal stall/spin on takeoff. The final incident was a failure of the rudder attach bolt in flight, which was fatal.

The last one is concerning, but none of the others indicate a problem with the design, and there's no way to tell if the failed bolt is a design flaw, a bad/incorrect part, or an assembly error. Since this has only been reported once, and there's been a lot of Hummel Birds built (can't find a reliable number at the moment), it seems more likely to be a bad part or assembly problem. I'm going to research it, though, and see what the builder's forums say. If anyone knows of any specific problems with the design, I'd love to hear them.
 

12notes

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Ultracruiser is cool, but needs more power to go 20mph slower in cruise than the Hummel Bird (HB-105mph@35HP, UC-85mph@45HP). Although this thread is in the ultralight section, as that's what I started with, I don't need it to be an ultralight.
 

BJC

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Discovering a issue in the wings of a plane that make them much weaker than designed exactly at the points where the most strength is required and refusing to fly it is far from paranoia, particularly when the frame protecting me also suffers the same problem. Although I don't have a problem with flying an experimental category aircraft, I do not wish to fly an actual experiment in structural integrity.

I would give it away to someone who was willing to sign an agreement that it is never to be flown, which puts you out of the running, unfortunately. Pilotless planes can still cause damage if the wings fold. Maybe that's what you meant by "attack aircraft". I can't knowingly allow this aircraft to fly, since I know there's a problem with the structure. If something bad happens, I don't have a legally defensible position.
If you expect to have, or expect to have, enough assets to attract a lawyer willing to work on contingncy, you might want to destroy it.

Related question: Has anyone here actually flown a Hovey design? How did it perform?


BJC
 
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