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Scaling Irregular Shaped Parts ?

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Scaling Irregular Shaped Parts ?

Old 02-01-2021, 06:31 AM
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A. J. Clark
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Default Scaling Irregular Shaped Parts ?

What's the easiest way to enlarge or reduce irregular shaped parts without the use of cad programs or sending to a printer? Would like to resize some formers . Thanks
Old 02-01-2021, 07:45 AM
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tedsander
 
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Oh, a hard to answer question! "Lofting" is the term you want to search on. Usually used to figure out the in between between two shapes (ie - round cowl former transitioning to a square tail former - how should the middle formers be shaped?) But it can be used to scale up already determined shapes, too.
Used to be done with a compass, rule, and math....
The hard part is finding "how to" using just pen and paper. I remember old articles about it in model magazines, but apparently no longer in my stack of saved things.
Closest I could find on-line was: Lofting-3 view drawings
Scroll down to the bottom, with the pictures of pages from an old model magazine. While that article does reference CAD, he goes into the "how to", which may help you to do it by hand.
Old 02-01-2021, 09:14 AM
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R8893
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Back in grade school we learned a technique where you take the drawing of the original object and overlay a grid of squares. Typically 1/4" squares will work. Now draw a grid with squares larger by the percentage you want enlarge. For example to double the size draw 1/2" squares. Then draw in each big square the lines that were in the corresponding smaller square.
Chuck
Old 02-03-2021, 05:01 AM
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A. J. Clark
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I took tracing paper and drew a x y coordinate system on it. Measured from the x y lines to plot the reduced shape and used the grid system as reference to make straight measurements. A little time consuming but it got the gob done.
Old 02-07-2021, 07:34 PM
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this is a little confusing at first, but it works. I haven't done it in a while.
Attached Files
File Type: pdf
airfoil scaling.pdf (627.6 KB, 36 views)

Last edited by guitarsbanjo; 02-07-2021 at 07:40 PM.
Old 02-07-2021, 08:50 PM
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tedsander
 
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Originally Posted by guitarsbanjo
this is a little confusing at first, but it works. I haven't done it in a while.
Precisely the article I was thinking about when I went digging through my old stack of saved items. Thank you for reproducing it!
Old 02-09-2021, 11:26 AM
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Often, irregular shapes are comprised of multiple standard shapes. A typical fuselage former is a rectangle with a half oval or half circle on top for example. So you might be able to use that method and then the standard methods of scaling.

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