Category: Rangefinders

Pompom director Mk I

The pom pom director Mk I is an elusive director. The Mk 1* was fitted to Rodney & Nelson, Hood, Furious (2), Royal Sovereign (2), Barham, and locations at Fort Cumberland, Devonport, and to Vickers-Armstrongs. The Mk I** was also fitted to Hood, as well as Barham, Ramillies (2), Repulse (2), Nelson, and locations at Porthmouth, Crayford, Chatman, and to Vickers-Armstrong. The differences between the versions consists of a cross wire foresight and some additional knobs although the older units were updated. The differences with the MkI** are unknown to me.

Knowing where these directors were fitted doesn’t really help in finding images. The location aboard HMS Hood is known but there are no photographs. Fortunately, Admiralty record Adm 186-316 in the UK’s National archives, entitled “Pamphlet on the director for the 2-PDR “M” Mark V Pom Pom” from 1932 contains a few pictures and diagrams. I ordered a copy for 30 pounds, just hoping the information would be there. Fortunately, it was! This pamphlet will be sent to the official HMS Hood site later.

From the material I gathered, it was clear that the directors Mk II to IV were smaller updates to the existing design while keeping a general family resemblance. The Mk I didn’t fit this pattern as the space located aboard HMS Hood for these directors was too small for the Mk IIs: the Mk I had to be smaller.

Here’s all the photographic material of the Mk I I could find. No measurements or general dimensions and no details of the lower part of the director.

The picture above shows something that does resemble the director greatly and is so far the only picture I have of the Mk I director “in the wild”. It also allows me to estimate the general dimensions, even though the dimensions of its emplacement are estimates as well.

Here’s the reconstruction in Autocad. The image at right is with the estimated tub dimensions of the spotting top emplacements.

This is the model of the Mk I together with the better-documented Mk II director. It’s not really much lower, but it does have a smaller footprint. I do not know if there are chairs and platforms fitted to the pedestal, as I do not have any more information. I do know there were more chairs fitted to the Mk II so that model will be updated later when my new etch set is completed. Of course, several etched parts for the foresight bars of this Mk I director will be included.

Here you can see the Mk I directors at their correct location. I copied an earlier picture with the Mk IIs. Note that the splinter shield now runs behind the directors, as is evident on photographs printed in Chesneau’s book. I changed the sponsons too: the radius of curvature is now equal to the radius of the circular emplacements on the spotting top when the directors where fitted aloft (AOTS Hood). The final locations were also fitted a bit lower than deck level to match the photographs better.

So, a lot of work and money spent on two puny directors that nobody knows what they look like… but one step closer to getting this model more correct than any other. I guess that matters.

Pompom director Mk II

Each of the octuple 2-prd pompoms of HMS Hood is fitted with its own director. From the Anatomy of the Ship book follows they have been placed on the fore top (spotting top) in cylindrical emplacements and moved down to the fore bridge in 1936. A third director was fitted in 1938 to the aft searchlight platform when the third pompom was placed. Now, the third director is a Mk II while the first two are Mk Is. The Mk II is available through John Lambert Plans, drawing L/0/64. I was hoping that the Mk II and Mk I were comparable. They are not.

This is a picture of a pompom director Mk IV fitted with the ‘Yagi’ aerial that was used for the radar Type 282, 283, and 285 that were also to be fitted on HMS Hood. The director itself seems to the same type as the Mk IIs and MIIs.

This picture shows two pompom directors as seen on the bridge of HMS Prince of Wales.

Here are the three models of the director Mk II with some etched parts, rod, and tube. The drawing shows great detail that can be added to these small models. The difficult part was cutting the tubing and adding the hand wheels. They kept falling off.

This image shows the directors at the correct location. However, they are much too large. They cannot rotate and the are too high to match any photograph of HMS Hood after 1936.

At left the aft searchlight platform is shown, indicating the location of the director. The top right image shows the location of the Mk Is prior to moving them to the fore bridge, the bottom right image shows them at their final location. From these images is well visible the Mk Is can hardly be seen.

High-Angle Control System Mk III*

HMS Hood was fitted with three HACS Mk III* directors (High-Angle Control System). These small high-angle/low-angle rangefinders were fitted around 1939, replacing one HACS Mk II on the (aft) searchlight platform. Information on this particular rangefinder was very hard to come by, as the Mk III* was only fitted to a few ships for a brief period of time. Most photographs show the round Mk IV-VIs, and the Mk IIs don’t really look like the Mk IIIs. To make matters worse, HMS Hood was not fitted with the Mk III, but the Mk III*, but I think the distinction is only that the Mk III has a 12-foot rangefinder and the Mk III* has a 15 foot rangefinder. The “Anatomy of the Ship: HMS Hood” by John Roberts shows a 3D view, most likely retraced from a picture but that’s about it. The good thing about scratch building is that everything takes so much time that you can sit around and wait for the information to sprout on the web. Strangely enough, this is exactly what happened, on the site of Godfrey Dykes. This site is colorful, to say the least, and may trigger epileptic fits, but I was ecstatic just finding the information.

The pictures on that site are cut up into 6 strange sub drawings, not entirely along well-accepted lines for cropping images but seemingly random. Not really a problem for Paint-Shop Pro. I first knitted the images together, making sure all parts scaled equally well by the pixel. I then imported the drawing into AutoCAD and remodeled the rangefinder taking the distance of the 15 rangefinder to scale the drawing. This drawing formed the basis for my work plan. There is only one really good shot of the rangefinder taken from above (check your references, most books show this picture), a few of various pictures of the ship and one picture of the rangefinder from the wreck. The official HMS Hood site later added similar information to its site, plus a few documents I exchanged with them, more than trumping the information on the site by Dykes. However, by this time the model was already nearly complete and there was no conflicting information. How’s that for a change?

With this information I was able to not only make an accurate model of the rangefinder which is a first (well, to me it is, most kits have some HACS-resembling blob, showing that the rangefinder s largely undocumented. Perhaps there are many British modeling clubs that have more information.), but I could even build a little bit of the interior. Although most kits and drawings show the rangefinder with a canvas cover, that cover is rarely seen on the photographs! The openings in the rangefinder’s roof are often covered with canvas, but not with the large hood.

Well, wishing a rangefinder with an interior doesn’t make it so, and building it proved to be just as a challenge as building the secondary armament. The floor of the HACS is odd-angles only. This picture shows the base plate and the first walls. A bit of rod (and a spacer) will become the first part of the rangefinder arms. A small block is glued in the center as a support for the front plate.

The frame of the HACS is nearly complete. The complex shape at the front is simulating using blocks and putty. Note that the rear panel is sloped at its lower end.

There is a smaller rangefinder with some optical equipment in the HACS. I etched the frame, but I made a series of errors. The top right pic shows I added a few disks, so that I could later cut the frame to pieces (lower left). I then added the frame to a strip, so that the base of the frame fits in the HACS. Note I use a very long strip, this makes handling the part a lot easier.

The rest of the etched part was added back to the frame and I even added a few chairs. How cute! At this point I wondered how much of the interior remains to be seen and whether I should stop here or whether I should continue adding more detail.

Fine, I added the commander’s chair at the back and I later added two chairs, one on either side of the center rangefinder. There is actually a sixth chair next to the commander’s chair but that one didn’t make it. Now the rangefinder fits within the body of the HACS. Note that I really needed to cut up the part, there isn’t much room.

The top left image shows the rangefinder with some tubing added. I bought this tubing from Cammett Limited. This tubing by Scale Caliber has an inner diameter of 0.1 mm (0.039″) and an outer diameter of 0.3mm (0.118″). They have more, so I suggest hopping over to their site and order some. I cut the tubing to size using my drill, putting the knife to the tubing.

You can’t actually see that much of the interior. I gave it a quick coat of grey, as the inside will be hard to paint with the rooftop in place. The rooftop was made from a series of strips (bottom left). This part was cut to size (slightly) and glued into place. The lower-right image shows the roof in place. Actually, this is the second roof; the first attempt wasn’t very good.

Here you can see the HACS with its roof trimmed to size. Looks nice, don’t you think? Well, I don’t. Note that the roof of the aft rangefinder is not well-centered and required putty to get into shape and that the front of the roof curves rather badly at the inside of the HACS. I didn’t really keep track of the position of the roof relative to the rear wall, being rather occupied by getting it glued to the HACS in the first place, so that was also not very good.

So, this is the roof Mk III (top left). I made six copies, so that I could keep the best three for the model. I taped five of them to a rod with sort-of the right diameter, having lost one already when sanding. The lower-left image shows the parts during boiling. This will soften the parts and they will keep their shapes when cooled down, so they do not have to be forced into a curve. It’s similar to the vacuum forming. The right pic shows the final result. The inner strips are so thin that bending them by force is exactly what made them look so poor with my previous attempt, so boiling them was a good idea.

The HACS director models with the roofs in place. Much better! Without having to force them into shape, I could place them far more easily and I could pay more attention to the alignment with the rear wall. Even though the slits in the roof are thin, the suggestion of the interior looks very good! The connection of the roof with the HACS needs a little extra work though, plus that I broke off a part of the front of the center HACS model.

I received some comments that the interior is all nice and such, but invisible once the part is finished, as there is some large canvas cover on the rangefinder. This cover is present on most kits and drawings. If you look at the above picture, the top-left rangefinder indeed has this cover, but this is the HACS Mk II. The rest of the pictures show the Mk IIIs which nearly always are without the cover. The third pic from the left, top row, shows that the openings themselves were closed off with covers when not needed, but the larger cover is not used. The two right pictures on the lower row are taken from an aircraft with HMS Hood at sea. So, definitely no covers! This doesn’t mean that the rangefinders did not have them, because I did find two pictures with all the HACS MkIIIs with the top cover in place. So, to be fair, I posted these as well. Apparently, these covers were rarely used and keeping them down is the norm. From this little study is also visible that the rear rangefinder didn’t have these flanges that are clearly visible on the forward rangefinders. Also note that the aft rangefinder was always positioned facing forward.

Here the units are complete with all detail except two covers on the front. The etched parts were etched at the wrong scale. The rangefinder to be placed aft (lowest here) doesn’t have the large flange. The interior remains well-visible.

A side shot showing off some nice detail, such as the roll-engine compartment with a small etched detail part. The window frame on the front plate was also designed for the rangefinder.

Just as a reminder that this is still a 1:350 model and that all pictures are taken at my camera’s macro setting. Ah, done!

Main Rangefinders

This post was updated 16th of November 2008

These two objects are HMS Hood’s main rangefinders. One is situated on top of the conning tower, the other one on top of the spotting top. The parts are built up from simple circle segments.

The conning tower’s range finder still has its stereoscopic rangefinder which I built with the viewports open, just as is possible for the rangefinders of the main armament (which I kept close).

The top rangefinder houses the radar antenna for the Type 284 Gunnery Radar. There aren’t many good pictures of the frame of the radar which is a guestimate, but there is an excellent drawing in Campbell’s “Naval weapons of world war II” and a few pics of other ships carrying the same antenna. It’s much more solid than all the etched parts.

Note the configuration of the rear of the rangefinder, which doesn’t have the typical box shape added to it as found on all drawings and all but the latest models. Yours truly found out, from careful observation, that the roof of the rangefinder was locally heightened and that the box shape followed from an optical illusion, probably caused the small ladder. Having the latest photographic finds on the official HMS Hood site helped, of course. A few custom-etched parts were fitted later, a few hatches and so forth.

A small detail was added later to the forward rangefinder make from tube. The steel tube was first heated and then pressed into shape with a pointed object. Two of these tubes were trimmed to size and inserted into a plastic strip.

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