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Old 09-06-2016, 01:35 PM
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Kugelfang Kugelfang is offline
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When do you start adding interior support structures?

Yeah, it's me again.

I'm working on my first design intended for completion (we'll see if I get that far!). DELAG's LZ-17, Sachsen--one of Zeppelin's pre-war civilian airships.

This is intended to be built at 1/250 scale which means the model will be 24.8" long and 2.29" in diameter. Since these early airships didn't have a very aerodynamic shape, most of it will be a consistent width tube about 17.8 inches in length. Clearly too big to be printed out on 8.5x11" sheets as a single part. It will have to be broken up. The question is: should I design to have as few, larger parts as possible, or should I go for more smaller parts? Would more seams for the smaller parts add strength to the structure or do smaller parts just increase the chance for misalignment between the parts?

Is there a strength advantage to using 110# card versus 67# card?

Should a model this size have an internal framework? At first I was thinking 'no' since it does have a triangular keel part that runs along the bottom of the main envelope. To be honest I'd rather avoid the complexity of an internal structure, but now I'm second guessing that, too.

Thoughts?

Thanks,

--jeff
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Old 09-06-2016, 01:50 PM
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Miles Linnabery Miles Linnabery is offline
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Dear Jeff:
Look to the past to Learn about the future. History Statement. Go look at how others have done Airships, Ralph Currell in Canada, Made some great airships with formers and tabs that lock together. Look him up in our links section in upper right corner of the home page.
Good luck,
Miles
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Old 09-06-2016, 02:04 PM
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Kugelfang Kugelfang is offline
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Thanks, Miles.

I looked at Mr. Currel's airships, even built one a few years ago. His models are a bit small for me to build--fumbled fingered that I am--and that's one of the reasons I've gone to a bigger scale for this design. I don't think I could build something with tabs like that with less than a 2" diameter. I don't remember him using formers. I'll have to look at his stuff again.

I also came across Thorsten Brand's 1/144 scale LZ45. He's gone to the other extreme and uses a full egg-crate internal structure--but his model is 45" long so I'm sure it needs that amount of support.

I'm just not quite sure where the happy medium is.

--jeff
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Old 09-06-2016, 02:59 PM
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Vermin_King Vermin_King is offline
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I think it depends on how it is to be displayed. From your dimensions listed above, it isn't going to have a very large cross-section for the length. If I were having it hang, I would make a triangular tube and attach it inside the top length to give it extra support. If you were planning on it sitting on a desk, I'd do the thing with card forming X's through it.
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Old 09-06-2016, 11:26 PM
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I think easier for people to give suggestion if you could post an image of your design.
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Old 09-07-2016, 02:37 AM
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Sure, here's an image with circular formers added.

In reviewing Ralph Currel's models I noticed he does indeed use formers. I didn't remember that at all. Since his airships are roughly the same diameter and he chose to do it this way that's probably a good lead to follow. I like the idea of X-shaped formers but I think there'd be less of a chance of deforming the envelope shape if circular ones are used. I'm not entirely sold on this but it seems the easiest, most practical solution.

I've got concerns over the support brackets for the props and the framework of the empannage. At this scale those parts will be very small. I'm sure I'll have to make them out of scale but I think that's an issue I'll have to solve during beta builds.

--jeff
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Old 09-07-2016, 09:54 AM
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At the length you stated, it looks to me like you already have enough formers. Of course, if a given section between them doesn't seem strong enough, you can always add another in the middle. At this size, I don't think you'll need a center keel.
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Old 09-10-2016, 12:04 AM
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This is how I would do to add structural integrity to the frame. I do that to all my aircraft and ship designs.
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Old 09-10-2016, 12:11 AM
Hazooka Hazooka is offline
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Briliant! This gives more stiffness to the frame than the perpendicular ones.
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Old 09-10-2016, 07:53 AM
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Allen's central support is exactly what popped into my head.
I think Vermin was suggesting the same thing.

...
Re sections (more parts) as opposed to longer tubes (less parts).

Obviously the issue of part placement on the printed sheet decides how many (minimum) parts you must have.
Its nice to have as few parts as possible since more sections to connect adds work and effort.
And you need to align more Parts along a longer area.

However, rolling tubes is not the easiest thing...rolling longer sections for this model is just as difficult.
I think keeping each part straight/parallel/true becomes harder the longer the section.

I would rather connect shorter sections with a model of this size.
-And, with the sheer number of connecting lines, seams, framework elements on a subject like this
it would be easy to hide the seams of the model within the design.
-And, since the connections are usually overlaps or added layers, it adds rigidity and strength to a model of this size.
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