Type A Mk IV catapult for USS Stevens conversion

[David Nielsen]

I am working on a 1/350 conversion of the Tamiya Fletcher to a USS Stevens. I thought I would try cad and 3D printing for the catapult.
I bought the Floating Drydock Stevens plans to start. It turns out they will be useful for the overall project but the catapult part of the plans
are a poor match against the photos of the real thing (Stevens, Halford, and Pringle). I hope what I have turns out to be a reasonable
representation. The overall length of the part is approximately 52mm from the nose to the aft edge of the walkway.

I was thinking of adding rivet detail but I think my desire to add detail needs to be tempered with the reality of them being too small to be
printed or seen. The last screenshot I have includes two rivets on the right side of the catapult in the center of the image. They're 0.06mm
half sphere's. This makes them larger than rivets would be but the added detail might be worth some artistic license. The Dragon USS
Gearing model has rivet detail on the 5in mounts but they're around 0.3mm in diameter (maybe 0.28?). What is the practical limit on how
small rivet detail can be for 3D printing and be visible?

Here are some screenshots of my catapult.

[Cadman]

Nice work. I think you will find many ships don't match their plans. As built usually reflects the real world adjustments that need to be made. Good photos will always be a big help.

[Roscoe]

Looks good, nice job...

About the rivet size for 3D printing, you can always send whatever company you plan on using a small sample with different sizes to see which works best, it shouldn't cost too much and then you can add them to the model accordingly.

look forward to more,
Dean

[Fritz]

Beautiful work Dave!

FOr tolerances you may need to contact whichever SLA vender to find out what they are. To give an example, the process we've decided to use for the Nautilus has a minimum "dot"size of 0.006" which means that depending on the treatment an object gets by the machine as it creates the layer outlines, a 0.004" item may either be over-scale, or not come out at all. Anything below 0.01" becomes iffy. Then there is the cumulative deviation where any Item about one inch large may have a resulting output dimension of 1 inch +/- 0.01" . Then there is an added +/- 0.002" deviation for every inch after that. example a 2" item will be 2" +/-0.012", 3" would be +/-0.014" etc.. This can cause issues in that a wafer 0.02" thick may result in anything between 0.03" thick to not being replicated at all. A general rule of thumb is that any recess or hole less than 0.01" wide and deep, my wind up filled in.

HTH

[David Nielsen]

Beautiful work Dave!

FOr tolerances you may need to contact whichever SLA vender to find out what they are. To give an example, the process we've decided to use for the Nautilus has a minimum "dot"size of 0.006" which means that depending on the treatment an object gets by the machine as it creates the layer outlines, a 0.004" item may either be over-scale, or not come out at all. Anything below 0.01" becomes iffy. Then there is the cumulative deviation where any Item about one inch large may have a resulting output dimension of 1 inch +/- 0.01" . Then there is an added +/- 0.002" deviation for every inch after that. example a 2" item will be 2" +/-0.012", 3" would be +/-0.014" etc.. This can cause issues in that a wafer 0.02" thick may result in anything between 0.03" thick to not being replicated at all. A general rule of thumb is that any recess or hole less than 0.01" wide and deep, my wind up filled in.

HTH

Hi Fritz,
Thanks for the info. The numbers and general rule of thumb definitely help.

David

[Rick E Davis]

Dave,

Sweet!!! I don't know what all sources you are using or if you are strictly working from photos (if you are, you are great at it!!!), but the Mk IV catapult used on the FLETCHERS was a new manufactured upgraded slightly version of the Mk IV catapult used on the OMAHA class cruisers. I have not tried to see if there are any drawings available for the OMAHA catapults.

I have several photos of the catapult on STEVENS and HALFORD that you can use if you want. Send me an E-mail via this board. Samples of close-ups below. Close-ups of the portside of the catapult are harder to get. Then there are even rarer views of STEVENS "other" CAT that was onboard her. (This is a for real photo of the STEVENS cat)

[David Nielsen]

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.

-------------------------------
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.

-------------------------------
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.

[DrPR]

David,

The whole ship "blueprints" that are available from many sources really are just sketches. Most are made from Booklets of General Plans or from whole ship profile and plan drawings in the original blueprint collection. In both cases these drawings are just general references for where the parts of ships are located. These drawings are made before the real construction blueprints are drawn and usually do not incorporate changes made during later design stages. In many cases they are very inaccurate.

This could account for the 50/50 catapult dimensions in the drawings and the 60/40 dimensions of the real thing. Only the working blueprints for the catepults will show the actual dimensions, and even these may be off a bit. Shipyards had a habit of doing things their way and not necessarily how it is shown on the blueprints, and often there were later modifications that never made it into the archives blueprint collections. This is especially true for rushed wartime modifications.

Working from photos is the only way to know for sure how a ship was built - unless the ship still exists. I use a similar "photoguestimation" technique to what you are doing, even when I have a working blueprint.

Phil

[Rick E Davis]

Phil,

What you say is mostly true, but from what I have found in looking through almost three dozen Booklets of General Plans of FLETCHERS during the 1950's and from talking to others who have researched drawings for other USN ships at NARA II (College Park), the LAST configuration is what will be found on the Plans. The General Plans like almost any "Full Assembly" drawings that I dealt with way back when I was a draftsman (35 years ago) generally won't be all that accurate. They show general arrangements and overall dimensions, but the actual dimensions and final production construction of specific areas of the ship may or may not be reflected and need to be found on individual part drawings. If a change didn't in general impact the overall appearance or "assembly", the Full Assembly or General Plans would not be changed. Plus, Overall Plans may or may not have been drawn BEFORE or AFTER the construction Engineering Drawings. So I wouldn't necessarily trust trying to scale from these drawings, unless there are other ways to verify (photos help). I have not dug into the full ship plans at the Archives, generally for WWII ships they are on microfiche/film. I haven't taken the time to explore those to see accuracy or range of when the drawings were completed. Dave McComb at DestroyerHistory.Org had the complete Bath Iron Works Engineering Drawings for the FLETCHER class digitized (pricey) and put them on DVDs, well worth the $35.00 cost. BIW built units cover four of the major configurations during the war (none of the aircraft-handling units) and are a treasure trove of information. Most drawings will list the changes made to the original plans and the final date will be shown. BIW didn't update them for changes made AFTER they delivered the units they built. I don't know what USN plans for individual ships would show for FLETCHERS in the microfilm versions.

True enough that different builders did some things differently when building their ships. But, they still were working from the same USN provided drawings (in most cases drawn up by Gibbs and Cox as the official USN agent). If they didn't follow the plans according to official direction, they may not get paid. Where things would go off track is where in a rush, SOMEONE in the USN chain would AUTHORIZE a deviation to the standard. Any such deviation was "suppose" to be corrected during a future yard period, but some ships never were corrected.

In the case of the Aircraft-Handling FLETCHERS, all of the units were updated eventually to the standard five twin 40-mm configuration and the General Plans and individual Ship plans reflect that. Finding drawings of the Aircraft-Handling FLETCHERS is next to impossible. I know of cases where "someone" with access to shipyard plans (plans for all USN ships were sent to ALL USN yards because they never knew when they may be repairing one of them) was able to "save" a set of out-dated plans once they were to be replaced by the new plans.

While working on an article on the Aircraft-Handling FLETCHERS, I tried to find drawings of catapults. Apparently none were saved after 1947. So for the Mk IV catapult, general dimensions and "eye-balling" from photos is about the only way to get there. I didn't think of trying to look at OHAMA class cruiser drawings, to see if there was a possible near accurate drawing of the catapult there.

[DrPR]

Rick,

I am most familiar with the Cleveland class cruisers, and the CLG modifications that were done in the 1950s.

The original USS Cleveland CL-55 drawings have been saved in the National Archives. In this incomplete drawing set of 4730 blueprints there are a succession of modifications through the three construction phases for this class. This makes it tricky to figure out which drawings were used for what ship, or even if a particular drawing was used for any ship. Later drawings always state that they supercede earlier drawings, but the earlier drawings may not say they have been superceded. You really need to find drawings labeled "Working Plan."

In any case, the whole ship profile and plan drawings in the Cleveland class blueprints were prepared before any ships were constructed, and they do not reflect later changes. They are marked with notes that they have been superceded by later drawings. Unfortunately, the later drawings apparently have not been saved, at least at the National Archives.

This is especially annoying because I am interested in the third phase "square bridge" version of the Clevelands (the majority of the ships) and I have been unable to find drawings showing the changes for these ships. There were at least another 4200 blueprints prepared in various shipyards for all the variations in the Clevelands, but most of these are not in the Archives. The index reels for these have been saved, and it is clear that each yard made its own set of blueprints. It looks like changes that came about during the war were not implemented by all yards at the same time.

One other confounding factor is that the ships were often not completed until after the first shakedown cruise. They were often built with the quad 1.1 machine guns, but it appears that few, if any, of the Clevelands actually went to war with these installed. After the shakedown cruise the 1.1s were removed and replaced with twin Bofors 40mm guns. Often some of the directors weren't installed until after the shakedown cruise. So even photos can be misleading. You need to compare the date of photos with the date of the yard period following the shakedown cruise.

The Booklets of General Plans were updated periodically, but they are pretty crude drawings. The BOGP for the USS Miami contains the only drawings I have found for the square bridge versions, and they have no dimensions and are too small to be very useful.

The shipyards had tremendous leeway in building the Clevelands. In fact, the differences are so pronounced you can just about say which yard built a ship just by looking at a profile photo. The most obvious difference is the trash burner smoke pipe. It is on the port side of the aft funnel on some ships, up the forward edge of the aft funnel on others, but one yard (and only one) put it on the port quarter of the forward funnel! At a single time in 1944 all three versions were being constructed.

Likewise, for the CLG conversions each yard made alterations to the "official" plans. No two ships had the exact same structure for the radar towers. The pipes are attached together using different gusset plates, welding techniques, etc. Each yard apparently used whatever materials they had on hand for some parts of the construction. For example, the USS Oklahoma City CLG-5 had water tight and air tight doors unlike anything I have seen on any Navy blueprints. They were not the same as the doors on the USS Little Rock CLG-4, her sister ship.

And the minute the ships were commissioned each experienced a different sequence of modifications. I would be surprised to find that any two were the same at a given time. All of this makes it extremely difficult to make a truly accurate model of any of these ships.

Phil

[Rick E Davis]

Amazing, I didn't know that drawings of the Square-bridge version of the CLEVELAND class were not available at NARA. You probably have already, but did you try looking for drawings of VINCENNES (CL-64) as the lead ship of the revised design or one of the later units, like DAYTON? Again, I have just started going through drawings at NARA. I have been using the Booklets of General Plans for the 1950s era FLETCHERS to see what the various configurations were (particularly sonar not visible in photos) at their decommissioning.

I could see that the CLGs all being different in configurations, there were various combinations of gun armament (three or six 6-in) and missile batteries (Talos or Terrier) arrangements ... I can't remember if any two were suppose to be the same?

I'm quite aware that many, if not a majority, of the USN ships during WWII were heavily modified between completion by the builder and the post-shakedown period. I have noted that the early CLEVELAND class units were in varied configurations trying to catch-up. The process of getting the changes in configuration on contract with each builder varied and the selection of "when" and on "which" ship they were incorporated in the "production line" varied ... sometimes by months. I have MANY pages of both such such cases for the FLETCHER class. Additions in armament and sensors were changing so rapidly, they couldn't afford to stop delivery of ships waiting for the contractors to catch-up. The post-shakedown overhaul was a good time to get things done to the "latest" authorizations prior to heading to the Pacific war zones.

Good luck on your hunt.

[DrPR]

Rick,

Microfilm 32099 is specifically for the Vincennes CL-64, plus CL-65, CL-66, CL-67, CL-82 and CL-83. Of course I immediately bought all six reels, 1361 blueprints. To my tremendous disappointment about 1355 of the drawings are for modifications to the plumbing for the heads, new wiring routes, etc. Nothing for the hull or superstructure! None of the major changes of the Vincennes square bridge design!! It does have nice drawings of the smoke pipes (funnels) and propellers (the propeller blueprints in the Cleveland CL-55 microfilm 5537* are unreadable) so all was not lost.

Microfilm 32048 is for the the Miami CL-89, plus CL-90, Oklahoma City CL-91, CL-92 and CL-93. This time I bought the Index reel first. 1708 blueprints of machinery spaces and electrical diagrams. Again, no hull or superstructure drawings. Bummer! However, if you want to build the boilers, turbines, condensers, etc., it contains a very nice set of drawings for just about every part, right down to pipes, valves and brass labels. Someday, after sanity has totally left me I just might make a CAD model of the engineering spaces.

Finally, microfilm 32011 is blueprints drawn by Newport News Shipbuilding Corp. for CL-62, CL-63, CL-80, CL-81, CL-86, CL-101 and CL-102. The Index is 335 single spaced typed pages listing what may be every drawing created for the Cleveland class, about 9,000 to 10,000 in all. Unfortunately, the microfilm contains only 1272 blueprints, and again these are mainly engineering and wiring. No hull or superstructure.

* Microfilm 5537 is the original almost complete set of plans for the Cleveland CL-55, CL-56, CL-57, CL-58 and CL-60.

For the CLGs the Little Rock CLG-4 and Oklahoma City CLG-5 were supposed to be the same, and they started out almost identical. However, the Oklahoma City underwent an extensive 15 month period of modifications after only three years that made a large number of changes, some major. After 19 years in and out of shipyards the OK City had a huge number of modifications. The major driving force behind the OK City's continuous series of modifications is that she was shot at for eight years in Vietnam and she received every anti-Soviet weapons system modification in the books. In contrast the Little Rock today is almost the same as when it left the yards in 1960. With no disrespect intended, the Little Rock had a pretty cushy 16 year Atlantic/Med cruise.

The Providence CLG-6 and Springfield CLG-7 (Terrier ships) were also nearly identical at recommissioning. The Galveston CLG-3 (Talos) and Topeka CLG-8 (Terrier) were each unique.

Phil

[Rick E Davis]

Dang, that does suck. I have been much luckier with Dave McComb having gone to the trouble of digitizing the Bath Iron Works FLETCHER class Engineering Drawings and putting them on a DVD for sale. As far as I can tell they are pretty complete. It does take a little effort to sort out which drawings go with which configuration of FLETCHER they built, but it can be done. The earliest drawings they have still had Gibbs and Cox title blocks and listed the other early builders of FLETCHERS, so I know that all builders started out with the same plans. As I researched through the textual records, I found out that the "common" configuration for FLETCHERS started to fall apart in mid-1943 as waivers were provided to each of the eleven builders yards because of "GET THEM BUILT ASAP".

[DrPR]

Rick,

As I understand it there is a collection of the original paper blueprints at the National Archives. I haven't seen them, so some of the missing Cleveland blueprints may be there. All I have is what they have on microfilm.

Some of the Cleveland drawings may also exist in shipyard collections, but I have no idea where those might be today. Most were on the east coast and I am on the west coast. It would cost me a small fortune to track them down and copy them, if they still exist. I have already spent more than $2000 just for microfilm.

Phil