Hi Rick,
Thanks for the comments.
I wasn't aware that the Mk IV catapult on the Fletches was based on one
from the Omaha class cruisers. The little information I was able to find
suggested the catapult was a cruiser catapult but didn't specify detail. I
looked lots of cruiser photos on navsource.org but found they didn't even come
close to matching the photos of the Halford. I found Type A Mk IV on the Calling
all Fletcher Fans on this site. There are some Stevens and Pringle photos on
that thread too. In any case, that's about all the info I was able to find on
the web.
I'll do some poking around for more info on Omaha class cruisers now
too.
I have a small collection of photos for the Halford, Stevens, and
Pringle. The resolution isn't great but I'm limping along with what I have and
it has been reasonable so far.
Most of the pictures of the Stevens come from this site.
http://www.uss-stevens-dd479.us/
The Halford and Pringle photos I have are mostly from navsource.org.
In fact the photo of the Halford you posted is on navsource.org.
http://www.navsource.org/archives/05/477.htm
http://www.navsource.org/archives/05/479.htm
http://www.navsource.org/archives/05/480.htm
The photos are pretty good but higher resolution photos would certainly
be nice. Some details are pretty fuzzy when I try to zoom in on the photos I
have. Thank you for offering to provide photos

. I'll definitely send you an
email.
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In terms of the cad, it was a combination of blueprints from the
floating drydock and the phots. The blueprints were 1/96th scale so I had high
expectations and at least for the catapult am relatively disappointed. The
copyright on them is dated 1981 so I'm guessing they were drawn then. I don't
know if the blueprints are based on the catapult found on Omaha class cruisers
or whether it was just really hard to get good references at that time (no
internet for example). This is a rather obscure subject matter so it would make
it even harder to find good references I would think. It has been for me in
2011.
I have a long list of things in the blueprints that don't match the
photos but it's probably not worth listing them all here. I wish I could just
post a scanned image but it's copyrighted material so I won't. I'll mention the
first two because it had a cascade effect making a lot of the drawing less
than useful.
1. The photos of the Halford clearly show a locker just aft of the
aft stack and another between the catapult and the 53 mount. Neither of those
are in the blueprints. That wouldn't be a big deal but there isn't enough room
in the drawing to account for the space taken up by them. The walkway around
the aft end of the catapult isn't on the blueprint either which makes the error
in length even worse.
The frame numbers for the blueprints appear to be accurate. They are
a perfect match for the booklet of general plans for the Sigsbee for example.
I used frame numbers to compute the distance between the stack and 53 mount and
a get decent estimate for the length of the catapult with the walkway and
lockers accounted for.
http://www.hnsa.org/doc/plans/dd502.pdf
2. Side views of the Halford are available with a camera angle just aft
and just forward of the cat yaw axis. If you measure the photos, you'll find the
catapult spans around 40% aft and 60% forward of the yaw axis. The blueprints
have the yaw axis exactly in the middle.
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The work I did was primarily from the photos. I am using a vector
drawing package called xfig. I load the image and set my zero position to be the
nose of the catapult. I draw a rectangle along a known distance. This was
between the stack and 53 mount. The tool has a nifty feature called the scale
factor which can be set. I use successive guesses to the scale factor until the
edit dialog for the rectangle gives me the desired length. Once it's set, I can
then measure the size and offset of anything in the photo by drawing rectangles
or circles around objects in the photo and looking at the numbers in the edit
dialog. The big advantage to this approach is I only need to do the mental
gymnastics of conversion from frames to feet/inches to 1/350 scale millimeters
once. It's not perfect but works pretty well for most things. Foreshortening in
images bites me in the rear once in a while.
There are probably other/better ways of doing this stuff but it works for me. In case
what I wrote above wasn't clear, here's a snapshot of what I'm doing.