"Minesweeper Clearance Path Widths? WWII and Modern" Topic

I'd like to know if anyone can provide a rough guide for how wide a path WWII and Modern vessels can clear, when they are on minesweeping duties?

I suspect it depends somewhat upon the type and size of the vessels, and gear available, and that smaller boats would be restricted to a narrower path, while larger trawlers, and dedicated minesweepers could clear wider ones.

Sweeping speeds would be helpful to know as well. I suspect they may need to move at a fairly slow to moderate pace, but don't really know for sure, for all vessels (I do recall reading an account of MGBs or MTBs being pressed into service in a UK estuary/river during WWII by speeding across suspected mine areas to use their hulls to detonate pressure mines [Crazy, right? With no M/S gear to help keep them and their crews safe, just speed.], with predictable results).

Any rough guides, or ideas on where to find this info would be appreciated, as mentioned, for both WWII tech, and more Modern (1950s era and later), tech:

WWII:
1. Patrol Boat/Small, wooden Minelayer/MGB/MTB
2. Trawler
3. Dedicated Minesweeper
4. Other, e.g. perhaps Corvettes, Frigates, Destroyer Escorts, and Destroyers

Modern:
1. Patrol Boat/Small ML/MGB/MTB
2. Trawler
3. Dedicated Minesweeper
4. Others, as above
5. Helicopters towing minesweeping sleds

Very interesting question that I don't have an answer for – a good read of WWII is "Out sweeps". The type of mines fuse – contact, pressure, acoustic, magnetic or electric and it's settings and depth sown all makes for more variables. You are correct that a larger vessel usually used longer sweeps, but they cost more to use/lose. As to acoustic mines one of the sweeps used was a massive drop hammer that when operated would make the sweeper ring like a giant bell and hopefully detonate the mine before the sweeper got too close.

It's been 30 years since I was in Tons, so take this with a healthy pinch of salt (sad thing is though I probably still have my Mid's notes somewhere in the shed).

The RN used an oropesa sweep, which was usually a single wire off one quarter, but could be a double sweep with a wire off each quarter. In theory a single wire would sweep approx one cable (200 yds), but current/tidal stream would effect that. Speed was maybe 8-10 kts tops, but again very dependent on the conditions.

The key questions with sweeping (and minehunting for that matter) are always what confidence do you want, and where is the swept channel? Don't quote me, but I think a single ship, single sweep only gave about a 50% confidence – if you don't know how many mines were there in the first place how do know when you've swept them all? (cf. US helo sweeps about which the RN muppets were generally pretty sniffy – super fast & super cool, but how do know what effect it had?)

The doctrine included planning tools for squadron sweeps with sweep wires overlapping to improve sweep confidence (and give trailing sweepers protection), but sweeping had pretty much given way to hunting by my day.

The question of where the swept lane actually was could be solved by laying buoys at the time of the sweep, or by having an MCMV conduct a lead-through. Don't forget, the world before GPS wasn't that long ago and back in ye olden days (generally) only MCMVs and survey vesseals would have anything more accurate than visual fixing.

Minehunting, btw, is an altogether slower process. On Tons we generally hunted at about 2 kts, and then you could be stationary for an hour or more if you found something as the divers went down (not sure, but I don't think ROVs sped things up much, just made it safer). Of course in theory hunting produces higher confidence and reduces the need for multiple sweeps, so there's an element of swings and roundabouts.

As I say, all very hazy memory but shouldn't be wildly off the mark.

Thanks for the first hand information in an area that doesn't get much press.

IIRC, our "navigation channel" drills involved areas not more than 400yds wide, with multiple turns in them.

I would go with Woollygooseuk, my time in Tons was probably concurrent with his but I also had experience of the Rivers.

In the Rivers we would tow a Deep Armed Teamed (DAT) Sweep at about 10 knots. As implied by the name it was a two ship job with the sweep curving in an arc between the two. Separation between ships was 400 yards and we reckoned on an effective swept width of 300 yards. With multiple pairs of ships we would work in formation so a subsequent pair overlapped the previous one by 50%.

Going back to WW2 capabilities I seem to remember the staff requirement for the Bangor class was to tow an Orepesa sweep at 10 knots. Assume other, purpose built sweepers would be similar. Trawlers being designed to pull heavy nets through the water would again be similar. BYMS and MMS used for inshore sweeping were probably slower, say 7-8 knots and used a lighter contact sweep, so probably had a narrower swept path.

I can't remember what the width was for influence sweeping against magnetic or acoustic mines. I suspect the former was narrower than sweeping for contact mines. A detailed search of the internet for the "Double-L" sweep should turn up the information. Most influence sweeping would be at a similar speed tp contact sweeping.

I also would recommend "Out Sweeps" by Lund and Ludlam for details of how sweeping was carried out.

Thank you for the replies, and detailed info.

I really appreciate them.

Sincerely,

Rob

General Quarters 3 covers this in painful detail. Emphasis is on the fact that this is a SLOW process.

Remember, any ship can be a minesweeper. Once.

Remember, any ship can be a minesweeper. Once.

Yeah, a friend of mine served on a Minesweeper in Vietnam. Apparently his ship was responsible for clearing Haiphong Harbor, and one day a fishing junk came out into the area his ship was still clearing. They wouldn't stop, even when the minesweeper said, "DANGEROUS!!!"

The fishing boat was under motors, not sail, and about 5 minutes after the minesweeper first tried to warn them off, KABOOM. Nothing left of the ship but toothpicks.