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Single Tube Fuselage idea

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FritzW

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This almost gets the parts count down to "one" ;)



image_12123.jpg Swag Roller Dies.jpg a Harbor Freight tubing roller and a set of SWAG dies

OTW1.jpg bend a tube like this

OTW2.jpg OTW3.jpg OTW4.jpg attach them together with two pieces of angle and some rivnuts (no rivet bucking needed inside a tube)

OTW5.jpg throw on a seat and motor mount (lander gear TBD) The seat mount would act like a huge gusset to alleviate some of the "Aford-A-Plane phobia".

Bending the tube would be a challenge but when it was done most of the fuselage is finished. The tail, gear and wings would be standard UL ...maybe
 

bmcj

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My concern is that your angle brackets are carrying the load in the bend and the riv-nuts will be loaded more in tension than in shear as it is currently shown. I think you want to put vertical plates on each side (maybe wrapped around the top or bottom too) to join the tubes.
 

erkki67

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How long is your single tube, 19 or 21' ?
For the ease of manufacturing 2 vertical plates riveted with blind rivets would be the way to go.
If required you could enlighten where possible by using FEM to obtimize weight and structure.
I like your out of the box thinking ;):gig:
 

Dan Thomas

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By the time you have tubing big enough to resist the torsion loads, it's too big to bend at any reasonable radius.

A famous designer, Ladislao Pazmany, once said something like "lightness usually comes at the expense of complexity." Simple structures are usually heavier than is ideal. Pazmany's airplanes were very good, light designs that took a little more work to build. His two-seat PL-1 was built as a trainer by the Taiwanese. The improved PL-2's empty weight was 200 pounds less than a Cessna 150's, and that's with a considerably heavier engine than the 150's. And it was faster, too.

22.jpg
 

FritzW

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The first draft had plates on the side and Avdel Avbolts but it looked like the tubes could rack back and forth and peel the rivets (Avbolts) out. If there was something added to prevent racking, maybe just shorter angles, then plates would be the way to go.

But I think the real challenge would be the landing gear. Every way I've come up with puts too much torque on the bottom section of the tube.

For ease of handling the tube in the roller I think it'd need to be done in two sections with a splice somewhere around the main spar before the "boom" makes it's first bend.

Yeah, rivnuts (rivstuds in this case) are a bad idea. Mainly because I don't think they handle curved surfaces like the tube wall very well. I think I'm going back to Avbolts. ...or just some good, hefty, Cherry Max's

...I'm going to have to pour a glass of thinking fluid and give due consideration to the landing gear.
 

Sockmonkey

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Maybe use the wing and landing gear struts to brace it in a form like so? M
Buy some tinkertoys or something so you can play with various shapes in 3D easily.
Maybe one of those lego kinex sets.
 

Hot Wings

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BigBen

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I agree that a mono-wheel mounted close to the lower wing strut attachment point would be a very light and rigid solution.
 

FritzW

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By the time you have tubing big enough to resist the torsion loads, it's too big to bend at any reasonable radius
Thanks for the insight. Would you mind sharing the math you used to come up with that fact? What torsion load did you use and how did you come up with it? What landing gear configuration, wheel spacing and gross weight did you use to determine the torque loads? What did you use for a "reasonable radius"? What diameter, wall thickness, material and temper did you use in your calculations to determine this fact? But most importantly, can you tell tell me what the hell a "Single Tube Fuselage idea" has to do with anything that was ever designed by Mr. Pazmany?

I place tremendous value on the opinions of HBA members:
"My concern is that..."
"you might realize some..."
"...vertical plates might help"
"I think I'd choose..."
"you could enlighten where possible by using..."
"Maybe use the..."
"Steel, at least for me, ended up being lighter..."
"...hand pumped hydraulic pipe bender"
"I agree that a mono-wheel..."


But stating an opinion (inevitably negative) as a fact, ie. "too big to bend at any reasonable radius" without ANY basis in fact just chaps my ass.

>>>This concludes my monthly rant on people pulling opinions (always negative) out of their butts and calling them facts<<<
 

erkki67

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for the LDG gear attachment, how about with a second bracket in he FWD LWR bent, as the torsion loads would not only be distributed to he tube itself but also being absorbed due to bent section, no?
 

erkki67

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landing gear options for single tube fuselage
And what about implementing the landing gear support into the engine mount, a little bit like on the Van's RV3,4,6 and so on?!
 
Last edited:

Aerowerx

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...But stating an opinion (inevitably negative) as a fact, ie. "too big to bend at any reasonable radius" without ANY basis in fact just chaps my ass.

>>>This concludes my monthly rant on people pulling opinions (always negative) out of their butts and calling them facts<<<
Exactly what I have been thinking!

But you forgot to mention those who post a question that has already been answered earlier in a thread.
 
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