DEVELOPING THE DD TANK

They started testing amphibious tanks at the end of the First World War but none of them worked very well. In the years leading up to the Second World War they became something of a fixation. They fell into two categories:-

First there were those that had integral buoyancy, that were designed to float with preparation. Either…

Tank Museum photo No. 1612/D/4

they were small, like L1E3 and almost useless or…

so large as to be ridiculous, like AT1* here.

Alternatively you could add bits to an ordinary tank to make it float but…

Tank Museum photo No. 2785/C/6

these usually turned out to be so wide, like this Covenanter with special floats, that they would not fit on landing craft and…

Tank Museum photo No. 2230/D/4

had to limit themselves to inland waters. In addition there was the awkward business of carrying the floats around in lorries, ready to fit to the tanks when required. Granted floats such as these, marketed by Nicholas Straussler and fitted to a Light Tank Mark VI, were collapsible but they were still bulky and difficult to handle.

Straussler ultimately solved the problem by inventing his folding screen, which gave buoyancy to a conventional tank without adding much to its bulk. It might not be perfect, but it worked.

Tank Museum photo No. 1595/D/6

The first application was to a Light Tank Mark VII, or Tetrarch, which was tested in Portsmouth Harbour. That proved successful and it was agreed to enter production with the valentine, a reliable British tank that was already in service.

Tank Museum photo No. 0342/C/1.

Here the prototype is seen undergoing evaluation, below is a production model afloat, with a much larger crew than normal.

Tank Museum photo No. 2192/C/4

Most DD tank crews, American, British and Canadian did their initial training on the Valentine DD.

For 1944, however, it was agreed that the Valentine was a bit passed its prime so the principle was applied to the Sherman, which by that time was in service with all Allied armies.

Tank Museum photo No. 0338/A/2

One great advantage with the Sherman was that it could swim with its gun pointing forwards, ready to fight as soon as it landed.

Tank Museum photo No. 0143/E/3

Even so, a 35 ton tank was quite a deadweight in the water and freeboard was limited. This Sherman DD, heading for the Isle of Wight, is meeting calm seas but once it got choppy there was considerable danger.

Yet the Sherman was not the last of the line. Drawings exist for DD versions of the Cromwell and Churchill tanks, although these were never built, and even after the war trials were carried out with a Centurion DD.

Tank Museum photo No. 6220/C/4

This, however, was probably going too far. Tanks were getting heavier so floatation screens were getting bigger and stronger. By the end of the 1950s such projects had been dropped, at least as far as main battle tanks are concerned.

Tank Museum photo No. 2797/C/4