Airframe from non-aircraft grade material.

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stanislavz

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So let's get back to the method of using medium strength commercial (non-aerospace certified) aluminum 6061-T6 angle... and let's discuss the method of using "bent angles" instead of extrusions.

Using these angles to make a truss fuselage is not perfect, because obviously the angle has a lower buckling threshold than a tube.

BUT this is easily and reliably able to be calculated and quantified using very standard and accepted methods. The appropriate adjustment (to address the difference in buckling) can easily made to allow this. So (random example) instead of bending the L-angle from .025 aluminum sheet maybe it has to be .032 in certain places.

Being able to make an airplane fuselage out of less expensive non-aerospace material is a worthwhile goal, but it still needs to be consistent, predictable and reliable.

There is more than way to skin a ship (tennie two) :

1654250929823.png

And this Russian Argo build in aluminium angles :

1654250980354.png
 

stanislavz

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Hi Stanislavs,
All the Morgan aircraft are designed to be really strong and rugged. We are in design mode to increase the Gross weight of the Cougar and Sierra's. The trusses go from firewall to vertical tail rear spar. Sheet metal is not as sexy as composite but you can put it together in your garage without the smell going all through the house!

No criticism on going no-composite way. And yes - going down in nowhere in Australia is kind of dead-situation. Where in eu you will be saved in next 10 minutes or so.
 

stanislavz

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If you are folding why not make top hat section with the outer skin completing the box?

Because this one approach need good jigs or predrilled and bend panels.

We are not in a search for fully sheet metal airplanes here . It was done before, and it will be done next.

But we are in a way how to build that wooden framed fuselage from non-wooden alternatives.


1654251394561.png

Each stick up here have to be hand picked, check for defects, cut to size, add some glue, clamp, wait, clean glue etc.. . Where for alum tube, especially square one - you just take your chop-saw and cut all pieces to length, drill holes, debur them and they are easy to rivet. You would even build a simple cnc-thing to do it.
 

OBwanBD5

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Gidday from NZ. I'm an A&P Tech of 41 years of experience at all levels from Building Iroquois Tailbooms from scratch to doing significant repairs in everything from Cessnas to A4 Skyhawks, and Hercules to Boeing 727s. I am also an Aircraft Builder with a BD4 and BD5 Kit on the go.
I am all for using cheaper sources of Aluminium for Aircraft Building, and in many cases, Commercial Aluminium is satisfactory for Frames Formers and Ribs, but due to the loss of Strength between 2024-T3 or T4 and 6061 -T6, I would tend to pay the extra to get 2024 for Longerons and Spars. 50% Stronger than 6061-T6 in Tensile, and 33% Stronger in Shear. Also, 6061 is typically in Bare form (not Alclad) so its protection against Corrosion is not as good. It is much easier to Weld, however... due to the Silicon content, so perfect for Welded Fuel Tanks and difficult formed shapes. Here is a Table modified from the TO 1-1A-9 which is all about Strength of Aeronautical Materials and Heat Treatment referred to in the front of the AC43...
 

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Vigilant1

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OBwan,
Welcome to HBA, and thanks for the post.
I'd not heard before that 2024 was more corrosion resistant than (non Alclad) 6061, just the opposite. I'll need to read up on that I guess.

Also, 6061 is typically in Bare form (not Alclad) so its protection against Corrosion is not as good.
Looking forward to reading more about your BD builds!

Mark
 

raytol

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Welcome OBwanBD5,
There is also a Facebook page for BD-5 builders in Australia and the US with really knowledgeble people to help with questions.
I think that 6061-T6 has better inbuilt corrosion resistance so they supply it without "cladding". 2024-T3 has less inbuilt corrosion resistance which is why it is supplied it as "Alclad". 2024 is harder to work with especially for hydroforming ribs unless you buy -T0 and heat treat it. I'm in design phase at the moment and are using 2024-T3 for the flat bits or simple rolled parts and 6061-T6 for the formed parts. Everything needs Alodine ( or equivalent)
and epoxy primer to have it live a long time.
Looking forward to hearing and seeing more of your build.
 

stanislavz

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Everything needs Alodine ( or equivalent)
and epoxy primer to have it live a long time.
Question is how heavy and hard it id at the end.

And - to make one needs different set of technology than to make 10 or 1000.

I think, i did read that jigs for Cessna costs big % in airframe price.
 

OBwanBD5

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OBwan,
Welcome to HBA, and thanks for the post.
I'd not heard before that 2024 was more corrosion resistant than (non Alclad) 6061, just the opposite. I'll need to read up on that I guess.


Looking forward to reading more about your BD builds!

Mark
You are right that the core Alloy of 2024 is worse for corrosion than bare 6061, but the cladding on the ALCLAD Sheet 2024 does a great job of protecting the surface, especially when primed. Areas of danger are where Steel Screws and fittings contact bare alloy, where dissimilar metal (or Galvanic) Corrosion occurs. Also a danger in Alloy Hard-points in Carbon Fibre Aircraft, as the conductive Carbon acts like a noble metal.
 

OBwanBD5

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Welcome OBwanBD5,
There is also a Facebook page for BD-5 builders in Australia and the US with really knowledgeble people to help with questions.
I think that 6061-T6 has better inbuilt corrosion resistance so they supply it without "cladding". 2024-T3 has less inbuilt corrosion resistance which is why it is supplied it as "Alclad". 2024 is harder to work with especially for hydroforming ribs unless you buy -T0 and heat treat it. I'm in design phase at the moment and are using 2024-T3 for the flat bits or simple rolled parts and 6061-T6 for the formed parts. Everything needs Alodine ( or equivalent)
and epoxy primer to have it live a long time.
Looking forward to hearing and seeing more of your build.
Yes, I am an active member of both FB groups. Thanks
As to forming Ribs, 2024 must be formed in O-State then Heat Treated if a smooth flange is wanted, otherwise they need to be tabbed or scalloped with fluting pliers, but even commercial grade alloy needs flutes or tabs to cope with curved flanges unless shrinking tools are used. Here are a few Ribs I made for my BD-5Forming the Rib around a Wooden Former (Combined).jpg
 
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OBwanBD5

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So let's get back to the method of using medium strength commercial (non-aerospace certified) aluminum 6061-T6 angle... and let's discuss the method of using "bent angles" instead of extrusions.

Using these angles to make a truss fuselage is not perfect, because obviously the angle has a lower buckling threshold than a tube.

BUT this is easily and reliably able to be calculated and quantified using very standard and accepted methods. The appropriate adjustment (to address the difference in buckling) can easily made to allow this. So (random example) instead of bending the L-angle from .025 aluminum sheet maybe it has to be .032 in certain places.

Being able to make an airplane fuselage out of less expensive non-aerospace material is a worthwhile goal, but it still needs to be consistent, predictable and reliable.
The BD-4 is probably one of the first Homebuilt Kits available from back in 1968, and still going strong today. It's fuselage is folded 2024-T3 0.063" Angles Truss Frame, screwed together for simplicity, and it is very strong, rated at +/- 6G which is not bad for a 4-Seater. Scaled down to Light Sports it could be lighter Gauge. I wouldn't go lighter than 0.040" for longitudinal Angles due to the lop-sided strength of an L- Angle, but shorter Diagonals and Verticals could be 0.032" . I wouldn't recommend going lighter gauge due to Euler Buckling issues.Truss Frame Fuselage mask.jpg
 

stanislavz

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The BD-4 is probably one of the first Homebuilt Kits available from back in 1968, and still going strong today. It's fuselage is folded 2024-T3 0.063" Angles Truss Frame, screwed together for simplicity, and it is very strong, rated at +/- 6G which is not bad for a 4-Seater. Scaled down to Light Sports it could be lighter Gauge. I wouldn't go lighter than 0.040" for longitudinal Angles due to the lop-sided strength of an L- Angle, but shorter Diagonals and Verticals could be 0.032" . I wouldn't recommend going lighter gauge due to Euler Buckling issues.View attachment 126438
Thank you ! But it is stressed skin, glued to frame in next versions ?

Bought some "non aircraft material" - cf pultrusion, 3.16*3.16. 310 meters. 2024 or 6061 is unobtanion on this part of pond. Shipped from Usa costs twice as cf.
 

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stanislavz

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And more message - all this goes to simple comparision. Single composite skin plus omega shaped stiffener made in place using pe rod by BoKu technology (5minutes per lamiting one strip 1meter long ? ). Or cutting square tube and making gussets plus riveting.

Or cutting angles and just bolting them. Or solid riveting...
 

stanislavz

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And i did received hylite composite panel for testing. 1.2 mm thick. 1.8 kg/m2 weight. Pp core. 0.2mm slum skins.

In short - it is more rigid, than it look. I will make some tests, but now it is better than 600gsm of cf.
 

Vigilant1

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And more message - all this goes to simple comparision. Single composite skin plus omega shaped stiffener made in place using pe rod by BoKu technology (5minutes per lamiting one strip 1meter long ? ).
And, when done, the structure and outer skin are both complete.

Or cutting square tube and making gussets plus riveting.

Or cutting angles and just bolting them. Or solid riveting...
Rivetting: Let's not minimize it, though. Even with pull rivets we might clamp, mark, drill, Cleco, updrill, take apart, debur, re-Cleo, and, finally, rivet. Perhaps we can assume our homebuilder will have precision CNC capability to avoid some of these steps.
 
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stanislavz

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Perhaps we can assume our homebuilder will have precision CNC capability to avoid some of these steps.
I think it is a must (having a cnc router mill) for riveted construction to be viable on effort level compared to free form composite molds (plywood bulkheads with metal or plastic foil between or cnc hot wired foam) with in situ molded reinforcements.
 
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