Single weapon that had the greatest effect.

Another

 

Well I suppose the Liberty Ship in a convoy could stop when a U-boat was sighted and winch the boat over the side and then.......

 

We do it all the time today. We did it in the Haitian and Cuban exoduses in my day - one or two larger vessels acting as mother ships for the small vessels - providing water, fuel, etc, as needed. Right now there are 60 foot crabbers in the Bering Sea in weather every bit as bad as the North Atlantic, with no logistic support whatsoever.

Above, you're talking about vessels not designed for heavy weather being carried across as cargo. Why wouldn't they be? However, a steel hull with a deep V is all that's required for just about any weather - look at the newer 95 and 110 foot CG Cutters. There's nothing new about that hull design and those vessels go out in weather worse than anything you can imagine. You just batten down and ride it out. In weather that bad, no torpedo attack would be possible anyway, so I don't see a down side. When the weather moderates you've got a small flotilla of ASW craft around you.

 

I know some US sub chasers did transit under their own power in convoy with other ships. One such convoy is recounted in Subchaser in the South Pacific J. Henry Doscher, Jr., Capt. (USNR) ret. He was commanding one in WW 2 and transited under power from Miami to the Solomon Islands in a convoy with 11 other SC's, 5 YMS, 16 LCI(L), one AO, one AT, and one YN. So, such crossings did take place.

None of that changes that such vessels had limited capacity at sea. In the above convoy, the author recounts that the smaller ships / boats had to refuel every three days even though they carried enough fuel for about ten. This was to ensure they had fairly full tanks in case the oiler was sunk. Convoy speed was limited by the slowest ship, in their case the LCI(L)'s, to about 10 knots.
They had to take on fresh water every time they refueled as they had no means of making their own. Food, likewise, was replenished regularly as the sub chaser has only limited room for provisions and almost zero refrigeration capacity.

The other limitation is radar and sonar. In the bottom photo above of SC 718 you can see the sonar housing retracted into the hull below the bridge. Without a radome covering it like destroyers and DE got, it limits efficient operation to about 10 knots. The size of the set installed is also limited. Their small size and shallow draft also limit the effectiveness of the boat and its sound gear in heavier seas. I'd say by sea state 3 or 4 you'd see significant degradation of effectiveness where a DE or DD wouldn't be until sea state 5+.

Without radar such a boat is largely worthless against surfaced subs at night. It lacks a means to fire star shell, it has no radar so it can't easily detect a surfaced sub, has little in the way of weapons to deal with a sub on the surface, and also lacks things like night binoculars and searchlights.
In the bottom photo you can see that SC 718 does have an SO radar set fitted at the top of its mast so it is a little more capable in this respect.
Another aspect is that they are incapable of making anything but the most basic repairs to most of their equipment. They lack the crew skills, tools, and parts aboard to do that.

On the whole, these aren't the most capable little ships.

 

You're describing small vessels designed for coastal work being used as blue water vessels. I'm describing a small vessel designed for blue water. Apples and oranges. The British already had radar small enough for aircraft by 1939, and centimetric radar for aircraft good enough to detect even a periscope by 1940. There's no reason a small ASW vessel couldn't have both good radar and sonar by 1942 when the US entered the war of the Atlantic.

I just think navies in general don't tend to think that way. Anything smaller than a DE or Corvette isn't considered seaworthy, which is silly when you consider those larger vessels were/are sailing past tiny trawlers out there in blue water.

Anyway, we're well past the "what if" point - such vessels were never designed or used so it's really not within the the topic of this thread.

 

Sorry to but in and take the issue back several years but my vote goes to codebreaking, put us on the front foot.

As someone from across the Pond would also like to mention the Spitfire and its part in winning the Battle of Britain - important for ensuring our future. Only a battle and not the war, yes, but still a key player.

Brian

 

I agree that submarines could not win wars on their own, I just wanted to give them their due credit in contributing to the Allies victory, especially in the Pacific against Japan.

 

Nope! The first centimetric set was the 271, which was ship-borne, and although trialed in early 1941, only 30 sets were operational by October, 1941.

The British did have airborne radars, ASV I & ASVII, but the wavelengths were still over a meter long. The first British airborne centimetric set was the ASVIII, a modified H2S radar set, and that did not appear in numbers until about March, 1943. The slow development was mostly the result of Bomber Command & Coastal Command - Bomber Command saw the ASVIII as a detriment to their acquisition of H2S sets and Coastal Command was not firmly convinced of the centimetric radar's effectiveness.

 

I'm surprised no one's mentioned the 173-foot steel-hulled PC, probably the closest thing to our hypothetical escort. Although they could make ocean transits, I am not aware of them ever being used for open-ocean escort (side notes, transits for ships like these or LCIs etc. were planned for periods of calm weather and used routes that minimized their exposure, as opposed to year-round escort on the North Atlantic sea lanes). PCs and SCs were used in coastal waters or areas like the Caribbean or Gulf of Mexico (where their only kill of the war was scored, U-166 by PC-566) to free up larger escorts for the ocean routes.

The Flower-class corvettes were the smallest effective trans-Atlantic escorts, and experience soon showed that a larger ship was necessary, the frigate, originally "Twin-Screw Corvette". Continued production of corvettes was mainly to make use of smaller yards which could not accommodate frigates, and British corvette building transitioned to the Castle class, 50' longer than the Flowers. Most of the mid-war "Modifed Flower" class were produced in Canada, part of a remarkable shipbuilding program.

U-boats attacking convoys were not looking to get into gun battles; they generally didn't even man their deck guns, and had only the essential personnel on the bridge so as to be able to dive quickly if they were detected.

 

The first US small boat radar is the SN (CXBR) set. It was originally as an emergency set for larger ships. The set that got put on most smaller boats was the SO. This set came in 15 variants from SO to -13. This series was first tested aboard a PT boat at the Boston Navy Yard 11/25/42 and went into production in February of 1943. The various models ran on different voltages, and ranged from 10 cm to 3 cm wavelength along with other technical differences. Weight was somewhere between about 200 lbs. and 500 lbs. for a complete installation.
The earlier 10 cm SF set was also produced for small craft. It began production on 7/13/42. This set weighed 949 lbs.
SG, the earliest US 10 cm surface search set (6/41) weighed about 3000 lbs. installed.