On Sat, 30 Jan 2010 14:22:29 -0800, brianDG303 wrote:

Many of the instruments are dimensioned, so you could just scale up or
down until they measured correctly, and then you could draw a clearnav
or paste in an image file and scale that until it matched as well.

I've done that with another CAD package (TrueCAD for Windows, a medium
priced 2-D CAD package). My method should work with any 2-D CAD system of
at least equal capability to TrueCAD, so ACAD should do it easily. Here
are the steps:
- pick a pair of measurement points, which must show up really clearly
and be as sharp as possible. The further apart they are the better
the final accuracy will be.
- measure between the points as accurately as possible
- make a photo of the panel.
- pull the image of the panel into your CAD system
- start a new layer and draw round the significant lines etc on the photo
using a cubic spline and enough points to give smooth curves. Avoid
using polygons because these need lots of points to approximate smooth.
Draw 3 point circles where possible.
- delete the photo layer
- adjust the scale of the drawing until the CAD measurement tool givess
the correct measurement. TrueCAD lets you select the points and
specify the distance you want, which sets the correct drawing scale,
and then adjust the zoom factor to fill the window, so ACAD will
probably do the same.

I use this trick when designing free flight models. I can generate a
scaleless wing section with a section plotting program, pull it into
TrueCAD and adjust it to match the required wing chord. Getting the chord
right within 0.05mm was trivial, so the main limitation on your accuracy
will be that of picking suitable points on the panel and of getting an
accurate measurement. I think I'd use a metric ruler to place masking
tape patches with their edges parallel and an exact number of mm apart
before making the photo. I'd also mark the exact measurement places with
pencil lines at right angles to the edges.

Its my experience that some ways of using CAD are not all that obvious,
so I hope I'm not telling you stuff you already know.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |