This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.
Peter Alway (PeteAlway@aol.com) suggests an old fashioned shortcut for
generating scale plans:
I find a slide rule is better than an electronic calculator for
scheming up scale models. You just set the proportion of prototype
diameter to a standard body tube diameter and slide the sliding
doohickey back and forth to find dimensions of all the other parts.
Jack Hagerty (firstname.lastname@example.org) counters with a more modern version:
Not to sound too snobby, but I have an even better way to make perfect
scale drawings of every piece AUTOMATICALLY. Use a CAD system. Even
the cheap ones (cheap meaning ~$100) usually have a scaling function.
On mine it's one of the commands under the "Copy" function.
CAD systems don't care if the screen is a mile across or .01" across;
it's all just numbers. When I did my Titan IIIB, the sceen was set to
be about 2,000" across (the Titan/Agena is about 1,700" from tip to
the bottom of the engine bells). You just draw in all of the pieces
from your prototype reference data full size. Then, when you're done,
you invoke the scale command to do essentially what Peter alluded to
above using the diameter of the prototype and diameter of the body
tube you're going to use to set your ratio.
Continuing my example, the Titan is 120" in diameter and I used Estes
BT-80 (2.62" dia) to build it. Once I had drawn the prototype I
invoked "Copy -> Scale -> 2.62/120 -> All" and presto! Every piece,
every conduit, every strut was now the correct scale size. I just
plotted it full scale on my plotter and I had the perfect layout
Mark Bundick (email@example.com) adds:
Try using a spreadsheet. They are particularly useful in cases where
there are station numbers instead of actual dimensions in the drawing.
In column 1, enter the part name or dimension. In columns 2 and 3
enter the station numbers from drawing. In column 4, enter a formula
to take the difference between the figures in column 2 and 3. In
column 5, enter a formula to apply your scale factor to the figure in
If you want to model in a different scale, just change your scale
factor and new dimensions are generated for every part you need on our
upscaled or downscaled bird. I find it particularly helpful to just
add different body diameters in different columns and then print out a
whole page of dimensions for various sized birds.