Improved Tribal Class Destroyers
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Ship Characteristics

Dimensions Length 394 ft
Beam 37.8 ft
Draft 9.5 feet
Displacement (standard) 2,250 tons
Displacement (full load) 3,050 tons
Performance Speed (max) 36.5 knots
Speed (cruising) 15 knots
Endurance 5,800 nm @ 15 knots
Armament Guns 10 4 inch Mark XIX, 8 40mm
Torpedoes 8 21 inch

Background

Their advocates have always called them an inspired adaptation of a design to meet changing requirements and strategic situations that provided the expertise and basis for post-War Australian naval construction. Their opponents describe them as an improvised collection of left-overs from other people's defense programs that were obsolete before they were ever laid down. One thing the Improved Tribal class can claim is a fair measure of controversy.

The resulting ships were much better than the British originals, in anti-aircraft terms at least, but they still left much to be desired. The RAN wanted to do better. Although they had been cut off from the UK, they still had access to the original Tribal design studies and, in searching through these for inspiration, they came upon one variant that inspired much concentrated thought. Most historians are so used to 4.7 inch being the standard British destroyer armament, they forget that in the late 1930s, the 4 inch twin mount won much favor as a dual-purpose alternative. Improved rate of fire appeared to compensate for the lighter shell, and anyway, a destroyer getting hit by a 4 inch shell wouldn't really be much less hurt than after being hit by a 4.7. Of course, the twin 4 inch had an anti-aircraft role; the twin 4.7 did not. One of the original design studies, that was dropped only very late in the design process, had five twin 4 inch mounts and a quadruple two pounder instead of four twin 4.7s and two quadruple twos. To Australian eyes, the five twin four inch mount solution seemed to make a lot more sense, especially since more than five years had passed since the original decision. In fact, the RAN quickly began to believe that the British had made the wrong choice and elected to adopt the five twin four inch mount configuration for the four new ships.

As might be expected, switching to the alternative design solution wasn't quite as easy as it sounded but it was no nightmare either. The problems involved in replacing a twin 4.7 with a twin 4 had already been solved; it was a simple matter of pulling and replacing. The extra mount was harder but the aft quadruple two pounder position had actually been designed with a twin four inch in mind (which begged the question as to why a 4.7 mount was sacrificed in the first group). The worst problems were with the guns themselves.

The twin 4 inch is often described as being dual purpose but it wasn't really. To get a high rate of fire at high elevation, the guns were mounted high in the trunnions. That puts the breeches low down when in AA mode, allowing them to be loaded rapidly. However, the same feature put the breeches uncomfortably high up when the guns were in low angle mode, making them hard to load and greatly reducing rate of fire. The solution was to lower the guns in the trunnion but position the mounting on a ring that incorporated a pit for the breeches. Thus, the breeches were equally accessible for high and low angle fire. With five mounts, the new Tribals could put forward a very high volume of fire, more than twice that of the American Fletcher class.

At this point, the design still looked very much like a Tribal, despite its extra gun mount. Close-range AA would be two twin 40mm mountings, between the funnels. The problem now was those funnels. They led to the machinery and Australia couldn't make the needed powertrain. The earlier ships had used equipment imported from the UK. That was no longer accessible and an alternative needed to be found. Here, serendipitously, things broke Australia's way. The German Type XXI was rapidly approaching an in-service date and the US Navy knew it, thanks to espionage out of Geneva. To this day nobody knows quite how although it has been suggested that the "Red Orchestra" spy ring working out of Geneva may have obtained the details. Be that as it may, the US Navy had a very good handle on what the Type XXI was and what it can do as early as mid-1943. Despite the German's fond belief to the contrary, the Type XXI and its performance were a blown secret. It was already understood that the slow DEs and corvettes that had defeated the Type VII and IX weren't going to hack it when faced with the Type XXI.

As 1943 faded into 1944 and the Type XXIs neared their operational debut, the US Navy started a massive program converting Fletchers and Gleaves class destroyers to fast ASW escorts. The newer six-gun Gearing and Sumner class destroyers were already taking over the fleet escort roles so the older destroyers were available for mass conversion. Up in Canada, the yards there started their own conversion of British destroyers to a fast ASW standard. With these massive conversion programs under way, Sumner/Gearing production had to be slowed down to make facilities available. That made some sets of Gearing machinery available and the RAN snapped them up, not to mention sufficient Mark 37 directors for not only the new Tribals but several other ships notably the surviving L and M class destroyers in RN service.

Redesigning the basic Tribal class hull wasn't as easy as it seemed. Some of the news was good; the Gearing machinery delivered 60,000 shp as opposed to 44,000 from the older power train. In addition, the American machinery was more efficient and the new ships would be longer-ranged than their older semi-sisters. The problem was that the Gearing plant was designed on the unit machinery base with alternating boiler and engine rooms and redesigning it just wasnt on. As a result, it was too long to fit in the space available.

This is where another bit of serendipity came in. Because the Tribals were the last British destroyer design to be transverse-framed, they could be lengthened more easily than a longitudinally-framed design. It was relatively easy to lengthen the hull amidships to accommodate the new plant. To maintain stability and keep stress within bounds, beam was increased. The internal design was modified to accommodate the Gearing unit layout. These changes put a lot of extra space between the funnels so an extra set of torpedo tubes is worked in. The extra beam allowed additional twin 40mm mounts to be added, increasing the battery from two such mountings to eight.

The larger hull made another change possible. A second Mark 37 fire control system was worked in aft, between Q and X four inch twin mounts. This turned the new class into very effective anti-aircraft ships, considered by some to be almost equal to the American Atlanta class light cruisers.

The new class followed the early ships in using the names of Australian Tribes, and HMAS Walpiri was laid down in 1947 (along with Kurnai, followed by Pitjanjara and Larakia in 1948 . By then their layout seemed dated and their design eccentric, appearance factors that hid the fact that they could deliver an impressive volume of fire. In the mid-1950s they were "lightly" modernized with new radars and fire control systems.

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However, their major upgrade came in the early 1960s. The four ships were stripped to their basic hull, their machinery being thoroughly reconditioned. Then, their foredeck was extended most of the way back to the stern, making them essentially flush-decked. A new bridge structure was provided that extended to the hull sides and allowed enough extra volume for a fully-functional combat information center. Armament was completely changed, all of the old weapons being replaced. A twin 57mm Bofors mount was installed aft, the guns being removed from the cruisers on their receiving MOG mounts. The stern was redesigned to accommodate a pair of Limbo ASW mortars. Amidships, the torpedo tubes were initially replaced by four fixed torpedo tubes mounted within the superstructure. These were reloadable and fired a new, heavyweight anti-submarine torpedo. This was an interim measure, essentially space and weight reservation a new ASW weapon called Ikara, a missile carrying an anti-submarine torpedo. Air defense was provided by a quadruple MOG launcher aft. Finally, provision was made for a light gun mount above the bridge, this eventually being filled by a 35mm BOER twin mount. The greatest change couldn't be seen. A new and powerful scanning sonar was installed and this turned the ships into capable ASW combatants. These modified second run Tribals ships served on for another fifteen years, finally being decommissioned in 1979/80, their legacy lived on though. Immediately post-war, the Australian Navy started to design its new class of destroyers, ships that represented a further expansion of the original Tribal design.

Class Members

Name Ordered Laid Down Launched Commissioned Fate
Walpiri 1942 1947 1951 1952 Scrapped 1979
Kurnai 1942 1947 1951 1952 Scrapped 1979
Pitjanjara 1942 1948 1952 1953 Scrapped 1980
Larakia 1942 1948 1953 1954 Scrapped 1980
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