The Ship Model Forum

Hello,

A question came to mind when I re-examined one of the fine images of CA-30 taken at Darwin NAT in WW2. (#10070/933831)

It shows what appears to be some kind of small spotting glass or scope mounted atop the aft searchlight control station (& earlier torpedo control, before the TTs were removed). I remembered that I have another pic of CA-30 in Manila Bay, ca. 1941, which shows the thing more clearly, with a sailor nearby.
I simply don't know what it was. Something for the searchlights? Or, navigational?
I believe it is shown in the Floating Drydock plans, but there was no info on it...

Anyone know? Or, familiar with such? seen on another US cruiser?

TIA

Hello, perhaps it may be an aux director, but why would it not appear on pre-WW2 photos?

Interestingly, it can´t be seen on this final CA-30 photo - either obscured by sailors or not there.

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Battle of Savo Island Collection (all 1/700)
Recently completed: USS Wilson DD-408
At works: USS Astoria CA-34 | USS Patterson DD-392 & USS Bagley DD-386 | HMAS Australia
Prep stage: USS Vincennes CA-44 | Yubari | Kako

Hello,

Thanks for the reply. Navigational is a good guess, I think. I believe it could be obscured by all the guys standing there in that Tjilatjap photo (some of whom I must have known).
It's in several prewar photos, in fact.
And I definitely have another very clear image of it in place prewar...Probably spring or summer of '41 while the cruiser was exercising in Manila Bay.
Appears in her Mare Island shots in fall '40 when undergoing her final major refit. (See snip)

The aft director's scope at secondary conn was notoriously sketchy, so the more I think about it, I do wonder if it was related to that...although navigational might make more sense.
But that siting out in the open is awfully precarious & no anecdotal references about exist from survivors AFAIK.
Also, it would be unlikely it escaped some damage from the Feb. 4th bombing, which wrecked much of the Main Radio position which is two levels below it...

is a range finder not navigation related.

That's a good point...

Makes me wonder if the navy--always thrifty, of course--recycled the original navigational RF on the foremast, and re-sited it aft...after it had been emplaced above the original position briefly.
Only appears there above in late '40 pix, after the MK19 on the foremast (Sky Forward) had been installed.
By early '41 (or so) it is gone from the foremast...and that open scope aft appears...

See pix.

G-Opt, what makes you say it is a "navigational range finder" when it is not on the navigation bridge level? the various Booklet of General Plans i have of heavy cruisers shows a 12' range finder on the foremast.

Neither has anything to do with navigation. The large one is the main gun director and the small one is a rangefinder for the secondary 5" guns. Chicago in 1941

OK, some mistaken info being inserted now.
Re those directors:

These cruisers had their secondary directors upgraded in the 1939-41 period, with the revamped MK19 shielded mounts used. Sky Forward atop the bridge and Sky Aft atop Secondary Conn.

But they did not all get identical upgrades. (No line drawings are entirely accurate, I'm afraid.) The placement of Sky Aft was particularly troubling & was usually re-sited atop the cut-down mainmast. CA-30 was lost before they could do that, however.

The Main Battery Director (a MK24 IIRC) for the 8" guns on CA-30 and CA-31 still atop the foremast as always. Spot 1/Director 1. The Gunnery Officer (Al Maher) position was just below that.
Spot 2 (Bruce Nelson) was the auxiliary director scope in Secondary Conn, almost useless as it turned out.

Since Augie had not yet rec'd. her upgrades--she still had only 4 5"/25cal guns--she had no need for two new MK19s yet...And had no degaussing coil then, etc.

I knew the officer in CA-30's Sky Fwd (Leon W. Rogers) pretty well, as well as some of his crew in there with him, so there's no question about that. He had responsibility for the 5" battery.
The officer (Bruce Skidmore) in the 8" MB director on the foretop did not survive.

I'm just speculating that they chucked that CA-30 RF or whatever it is atop the after SL Control & Main Radio since they had it...but they removed the shielding.

Of interest to this evolution, I have a pic of CA-30 leaving LaHaina in late '39 or early '40 with her new MK19 directors in place, but no 1.1" guns/tubs yet, and not all of her expanded 5" battery either. So, pressumably that work was completed at her Mare Island refit late Summer/early Fall 1940 before she went back out to the P.I. to relieve Augusta.

What this tells us is that the upgrades were done over a long(ish) period of time, bit by bit, and at least in CA-30's case, never fully completed before she went to war. It seems this was due to difficulty in scheduling yard time, getting the funding, and transporting the right parts to the right place.

Hope this is helpful.

you don't use a target range finder for navigation so why are you calling it a "navigational rangefinder"?

I'll try to clarify this if I can:

1) the MB director w/its scope is not on the level of the MB. The secondary battery directors are not on the same level as the secondary batteries.

2) "In July 1940 the Scouting Force recommended installation of navigational rangefinders on the forward machinegun platform, and by November this modification had been approved for the Louisville, Northampton, and Houston, using 12-ft. MK 35 rangefinders. When the supply of those units ran out, 2.5 meter rangefinders were approved for the Pensacola, Salt Lake City, and Chester."
Norman Friedman, US Cruisers: An Illustrated Design History (1984), p. 134.

3) So, the original RF (which were 15') were probably not navigational. The later units definitely were. I was in error about that distinction for sure. But knew I'd read about navigational RFs in a reputable source at some point.

Thanks for helping clear this up for me.

In case any of the comments are assuming that rangefinders are for fire control only and not for navigation, here's an interesting 1924 piece in Lloyd's that talks about navigational rangefinders: https://books.google.ca/books?id=MisWAQ ... 22&f=false

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De quoi s'agit-il?

The object in question looks (to me) to be the same small rangefinder seen in the foreground of this photo of DE-263 in 1945: NH 91630 (note that this photo also shows the Mark 52 director with ranging radar aft of the small rangefinder)

I've noticed this same rangefinder on the pre-war DDs and the as-built Atlanta and Juneau above the pilot house. I have seen it referred to as a "navigational rangefinder" and also a "short base tactical rangefinder". My understanding was that this type of rangefinder could be used for gunnery but also for taking range readings off landmasses or ashore landmarks for navigational purposes in the pre-radar days. I have not been able to find a mark and mod for the unit. Cheers

Thanks for the info. I appreciate it.

Recently was able to access the finest CA-30 Scrapbook/photo album that I know of, and found many late photos of the ship, with that little aft RF showing. The scrapbook--which I had not been able to view in person since the mid-Nineties--came back to the States sometime after 12 October 1941, which surprised me. (Sadly, had no good phone or camera with me, so only got crude snaps.)

How exactly it got back just before the war started, I do not know, but it is still in superb condition.