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Polar Bear

Paddlewheel Minesweepers?

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Polar Bear

This query/ tangent comes from the following topic

 

Anyway it got me thinking. Not so much that HMS Shirley was a paddlewheel minesweeper but that she was newly built as part of the Emergency War Programme (she was launched 1917 - one almost certainly incorrect source suggests early 1918). Further she wasnt alone. She appears to be one of eight 'improved' versions of her class (along with 24 unimproved vessels). So, my query (queries). Are paddlewheelers somehow inherently better at minesweeping than screw powered vessels? Is that why even late in the war scarce resources were poured in to these 32 vessels? Alternatively was a paddlewheel vessel easier to produce? Did it use up less resources? I can't see how. Or was it simply that some (I assume (!) small) shipyards were still producing paddlewheelers and didnt have the ability to produce screw powered vessels?

 

Or is there something I'm missing?

 

Any thoughts would be very appreciated.

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gmac101

Paddle wheelers have a few advantages over screw vessels particularly in calm waters, the big advantage is that, by running the paddle wheels in opposite directions the ship can spin on its axis making it very manoeuvrable. The wheels can also be fixed easily by raising the damaged portion above the waterline and the vessel doesn’t need any underwater penetrations and this reduces the risk of flooding and makes maintenance easier.  A well designed paddle wheel is nearly as efficient as a propeller but in open sea rolling reduces the efficiency.  

 

I can imagine that in sheltered waters they would make great minesweepers 

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Polar Bear

Thanks for that gmac101. I hadnt considered the calm waters aspect (or indeed the damage aspect). Admittedly from what I can see of their useage quite a lot seems to be out in The North Sea. In other words not calm waters but perhaps they were intended to be used closer in and the requirements of the time resulted in them being used further out.

 

Anyway, thank you for your thoughts.

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seaJane

The Wikipedia entry suggests that water tended to overwhelm the paddle box if the sea was at all rough.

https://en.m.wikipedia.org/wiki/Racecourse-class_minesweeper

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Polar Bear

Thank you for that SeaJane. I had indeed seen that and it was a small part of what had got me wondering about why we were still producing paddlewheelers. On the other hand I think gmac101 has it right. They were intended for inshore work (where they would be fine. Probably more than fine) and some at least ended up forced to operate elsewhere.

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The Dark

The earliest Racecourses were built by Ailsa, which did paddlewheel ships before the war. It may simply have been a case of finding something for that portion of the yard to build without major retooling (they did build screw-driven Insect gunboats and Hunt minesweepers as well). They ended up being shallower draft than the screw-driven Hunt-class by a foot, which is always a positive attribute for a sweeper. In 1912 Ailsa was the 42nd largest shipyard in the UK, constructing 9 ships of total gross tonnage 14,035. By number of ships it was a fairly active yard, but it built small ships (Vickers, for instance, built only 4 ships, but their combined tonnage was 52,860).

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KizmeRD

The superior speed of paddlewheel minesweepers was also an advantage. Most had been built pre-war for passenger use and they were faster than many commercial trawlers and drifters in use during the Great War. The relative lack of speed of many of the auxilliary minesweepers used in the Dardanelles, for example, was a huge problem when operating in places where the tidal stream was almost equal to the maximum operating speed of the ship. If sailing against the tide, it made them almost static relative to the land, resulting in them being less effective in their ability to cut moored mines, and making them farly easy targets for shore based guns.

Michael

Edited by KizmeRD
Ref. to Gallipoli deleted.

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Hyacinth1326

I seem to recall that there was a high casualty rate among the Racecourse class,  Ascot always makes me feel very sad.

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Polar Bear

Thank you for all who have replied. It has given me a much more complete picture of something I hadnt considered before.

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The Dark
9 hours ago, Hyacinth1326 said:

I seem to recall that there was a high casualty rate among the Racecourse class,  Ascot always makes me feel very sad.

 

Five of twenty-four were sunk - Ascot by U-Boat on 10/11/18, Kempton by mine on 24/6/17, Ludlow by mine on 29/12/16, Plumpton by mine on 19/10/18, and Redcar by mine on 24/6/17 (24 June 1917 was a bad day for the Racecourses - both Kempton and Redcar were lost off Dover). Another half dozen mercantile conversions from civilian paddlewheel ship to minesweeper were sunk (five by mine, one by collision at the entrance to Harwich harbor), but that was out of 50+ converted vessels.

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Lawryleslie

It’s very surprising, apart from cost, that paddle wheel propulsion was even considered for vessels other than harbour support. By the mid 19th century it had been proven, by both instrumentation devised by Brunel and trials, that screw was more efficient than paddle wheel and as early as the 1853 Fleet Review the majority of steam ships attending were screw propulsion. There were many cons such as vulnerability from enemy weaponry with all machinery above the waterline, inability for a paddle steamer to perform a complete broadside and, particularly for minesweepers, much greater water turbulence. The only advantage apart from lower cost was better manoeuvrability at low speed. (Source The Engineering Branch of The Royal Navy by Commander M A Barton RN. 2018)

By the time of WW1 shipyards were well versed in the production of screw powered ships so this would not have been a reason to build paddle steamers. The only plausible reason would be lower cost and speed of building which would have been less complicated.

Edited by Lawryleslie

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horatio2

Ditmarr and Colledge note apropos paddle sweepers:

"The shallow draught, high speed and manoeuvrability of these ships made them desirable for most minesweeping work but they were far less satisfactory than trawlers as all-weather minesweepers. ... {ASCOT Class paddlers] were bulit as a result of the success of the hired paddlers in sweeping coastal waters ... Moored mines situated in areas where the range of tide was great could be swept much more safely by these types because of their shallow draft [7 feet] ."

 

It would appear that propulsive efficiency was not the deciding factor.

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KizmeRD

Excellent summary by D&C - in addition, I might add that small vessels of any type were in very high demand by the Admiralty. The fact that there were 50 or more paddle steamers available for war service at the outset of the war could not simply be ignored, and they were successful enough in the auxilliary inshore minesweeper role that the navy even went ahead and built its own new ones.

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rolt968

Two of the PMSs having become excursion steamers also served in WW2.

There was also the Dance class of "Tunnel" minesweepers where the propeller was in a tunnel to reduce the draught.

(I also wondered in both cases if it reduced the risk of fouling the propeller in confined waters.)

RM

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KizmeRD

The tunnel minesweepers were originally built for the inland waterways transport section (Royal Engineers) designed as a tug for towing barges in Mesopotamia. They were twin screwed, with the propellers sited higher than normal, partially recessed into the ships hull (imagine half circular channels cut into the bottom of the ship at the stern end, This arrangement made it less likely to damage the propellers if the ship grounded in shallow,water. They were brought into service at the end of the war to clear river estuaries of mines along the coast of France and Belgium.

Edited by KizmeRD

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wallace2

Agree with Horatio 2 that shallow draft would be a major consideration in the employment of Paddle Wheel Minesweepers.  That was my first thought on reading the thread.

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