This day, seventy years ago, 07/29/1942

Seventy years ago on this day, Wednesday, July 29, 1942 (during the Battle of the Atlantic two merchant ships were sunk): The Norwegian steam merchant Bill was torpedoed and sunk by U-155; and the unescorted Canadian steam merchant Prescodoc was torpedoed and sunk by the U-160.

There were 87 U-Boats at Sea (Events this day - U-Boat Net).

U-210 sights Convoy ON.115 in the North Atlantic (41 Ships). Within a week 3 ships will be sunk and two damaged.

In July, 1942:  97 ships (458,351 tons) were sunk and 11 ships (90,138 tons) were damaged by U-boats and mines.

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The First Battle of El Alamein ended. The British had stopped the Afrika Korps advance into Egypt.

Soviet Marshal Josef Stalin began moving massive numbers of troops into the Stalingrad area.

Gas rationing began on the East Coast of the United States.

Operation Watchtower began as 17,000 U.S. Marines boarded ships near Fiji on July 26, 1942. The Watchtower force, numbering 75 warships and transports left for Guadalcanal on July 31. The USS San Francisco is in the Watchtower Force. 

07/29/2012 - Fuse Settings & Kw

Today started wet and rainy I didn't get a chance to walk my 4 mile loop.   After a little while it cleared up, and it turned out to be a nice day. I managed to conduct three tours.

During one of the tours I was asked about the kw rating of the Main Propulsion Generators. The answer turned out to pretty easy. It was detailed on the USS Slater Web site - Description of B-2, The generators were Allis-Chambers, 1200 KW, 525 VDC, 750 RPM, The USS Slater has four.  The picture above is the main generator in the forward motor room.  In the description of the aft motor room B-4, there is a panoramic view.

The USS Slater has a power plant arrangement that is similar to fleet submarines.  There is a detail description of WWII US Navy submarine generators on the Historic Naval Ships Web Site.

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At the 3" 50 cal I was asked what was the minimal time setting of the mechanical time fuse (MTF)?  A mechanical time fuse is used for shooting at airplanes.  This minimal time is referred to as arming delay (a safety feature).  It is the minimal setting from the time a gun is fired, until a projectile can detonate.

The short answer is 0.60-second for the 30-second mechanical time fuze.  There appropriate projectile (3" Mk26) is detailed in the US Explosive Ordnance Manual (OP1664, May 28, 1947). The fuse referenced is Mk21 MTF (same manual, OP1664 page 105). 

At a muzzle velocity of 2700 ft per second, the .60 delay, means that the shell will travel somewhat less than 540 yards (2700 * .60 / 3).  The muzzle velocity is the highest rate of travel for a projectile but it will slow the further the projectile travels.  The rate is influenced by the gun elevation.  You need range tables to determine the exact value for a given elevation.

btw - Detail Information of the 3" 50 cal. is available in OP 811, 1943

7/18/2012 - Coast Guard Convoy Video

On the 15th of July, we gave a tour to a WWII Coast Guard man who served on Patrol Frigates (PF). I ran across this Coast Guard Video that shows PFs in action.