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  #11  
Old 05-28-2012, 12:11 PM
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Tail prototype

Today I tested the tail of the monster.

Here below the sequence I followed.

1) I cut out the parts of the box and of the diagonal fins

2) I glued the fins on the corners of the faces of the box and the plaques on the sides.



3) I glued the vertical fins at the marks on the faces



4) I cut the rear spoilers and I glued them on the interior side of the box.



5) I cut and glued the parts of the internal "funnel (?)"



I glued together the faces of the box



A first comparison between Little Boy and Fat Man




6) The last details added and protoype completed




I found some minor mistake that I can easily correct.

What do You think about color, detail, rendering, shape, etc. ?
I'm quite satisfied for the result, but any criticism and suggestion at this stage is welcome.

Best, Nando
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  #12  
Old 05-28-2012, 12:39 PM
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From where I stand the build looks exactly like the rendering! So very well done!

Cheers!
Jim
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  #13  
Old 05-29-2012, 09:28 AM
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You don't waste any time, Nando. I am off to the printer today to enlarge my Little Boy to 1/4 scale which will make it about 30 inches long. My intention is to scratchbuild the interior and do a cutaway. I'll let you know if and how it turns out.

Thank you for the inspiring design work!
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  #14  
Old 05-29-2012, 04:10 PM
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Thanks for the encouragement.

Here small progress: all the parts of the tail colored and arranged with the sheet to be printed back , everything in Inkscape.




@cdavenport

Very huge model indeed! I hope that you don't encounter problems resizing my design so much. I never tested a vector file at this level and I don't know if there is some issue or some trick to avoid problem. Let me know how it turns out: I have so much to learn in this field.

Best, Nando
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  #15  
Old 05-30-2012, 11:55 PM
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It was a simple procedure. I just printed your file and enlarged that.
I am going to use your parts as templates. Rather than spill the beans from a can that may not be opened for awhile, I'll post pics as I build the model.

Concerning Fat Man, you have done a magnificent job of rendering the tail assembly. It's a work of art.

I have never seen it in such detail. I can tell you from looking at its structure that it was designed to retard the fall of the bomb by creating drag. Modern nuclear weapons employ a parachute drag system to allow the bomber to escape the worst of the blast effects.

Keep up the great work, Nando!
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  #16  
Old 05-31-2012, 08:30 AM
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Stabilty

Quote:
Originally Posted by cdavenport View Post
...
I can tell you from looking at its structure that it was designed to retard the fall of the bomb by creating drag. Modern nuclear weapons employ a parachute drag system to
allow the bomber to escape the worst of the blast effects.
...
About the function of the tail structure, I found a reference when they talk about the difficulties to stabilize in a correct and predictable way the bomb when it falls.
Little Boy, with its simple and conventional shape, didn't give any relevant problem regarding its stability, but Fat Man with his fat shape had a tendence to roll, doing unpredictable its trajectory. The shape evolved giving a more aerodynamic profile to the body, doing it to seem to an egg, and enlarging and adding a sort of hopper to the tail.

The data from Wikipedia are

Fat Man
Weight 10,213 pounds (4,633 kg)
Length 10.7 feet (3.3 m)
Diameter 5 feet (1.5 m)

Little Boy
Weight 9,700 pounds (4,400 kg)[1]
Length 120 inches (3.0 m)[1]
Diameter 28 inches (710 mm)[1]

If we compare the data, we can see that the lenght and the mass for both the weapons are similar. What is different is the diameter, almost double in Fat Man than in Little Boy.
So, regarding the speed, bigger frontal section = bigger resistance = less velocity and more time for the bomber to go away.

Rather, for the stability issue, we had to increase the resistance of the tail, like we do with the feathers on the tail of an arrow and so making slimmer the Man.

I don't know if my interpretation is correct, but comparing the two bombs, it seems logical, in my mind.

I can't wait to see your model.

Best, Nando
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  #17  
Old 05-31-2012, 11:44 AM
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So, then, the high drag tail assembly had the effect of lengthening the bomb aerodynamically. Quite the opposite of what I was thinking. Still, an excellent job on your part of rendering such a complex part!
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  #18  
Old 06-04-2012, 03:41 AM
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Unfoldng the Body

Here some example where I am with the project.
I have corrected the model in SU to allow the Pepakura unfolded it well



Then I did some more work using Inkscape to prepare the model for the test build



I have now to add some particular for start the test build.
Then correct the errors, color the model, add particulars, add the references, write the instructions, build the model, edit the final release, ...

Best, Nando
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  #19  
Old 06-05-2012, 03:04 PM
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Details on the Body

First I added more details on the body using SU.



The I unfolded in Pepakura the model and I arranged the parts on two pages.



Then I edited the parts, converting them using Inkscape and testing some color.



Now I have the first version printed and I can start the test build of the body.



Best, Nando
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  #20  
Old 06-06-2012, 09:23 AM
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the front half part of the body

The daily progress: cut, fold and glue







No tabs



Only one bulkhead



A compare between the two prototypes



Best, Nando
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