British Hovercraft: Saunders-Roe, BHC, Griffon, Vosper, Vickers etc...

[Weaver]

Here's another good website with lots of info on Hovercraft: https://www.bartiesworld.co.uk/hovercraft/index.php

From there, this cutaway of a full-wdith BH.7:




I also found this excellent cutaway of the SR.N3 in military test configuration. VERY interesting. The original file is much bigger than this pic, so go and download it if this isn't clear enough for you here: https://postimg.cc/nCTgQG85



Things of note:

1. There's a storage compartment under the floor of the cargo bay, in the thickness of the floor "raft". Not clear how you access it.

2. The crewing arrangement confirms my suspicions about how the navy would choose to crew a hovercraft. The "driver" isn't called a pilot, they're called a coxwain, and the captain sits right behind them, "on the bridge" as it were. The engineer sits at their feet facing backwards, and the navigator is down in the hull, rather than behind the pilot as in the SR.N4.

I think the RN would crew an SR.N4-based minesweeeping hovercraft by having an enlisted coxwain (pilot) and engineer sitting in the front of the cockpit, with an Officer Of The Watch sat behind them. The navigator (possibly an officer) would be down in the Operations Room along with the Officer Commanding (Captain usually). Also in the ops room would be, at minimum, a radar operator and a radio operator, who between them probably have enough "bandwidth" to also operate a simple ESM+decoys system, and a couple of sonar operators (most sophisticated sonars need at least two operators), one of whom can slide over to the ROV control console next to it when the PAP-104 is in use.

I think that they'd need at least four "deckhands" to deploy and recover all the minesweeping and hunting gear and one CPO/officer to command them. I imagine they'd also want at least one electronics tech and one propulsion tech on-board, though they might also double-up as deckhands. Likewise at least one diver.

That gives 3-4 officers and 10+ enlisted crew. However that makes no allowance for a three-watch system, which raises the interesting question of what the Concept Of Operations would actually be. Would the craft be at sea for days (like a ship), in which case a three-watch system, on-board maintenance and "hotel" services (hot food, bunks, washrooms, more heads) would be needed, or would it be at sea for less than a day at a time (like an aircraft) in which case a three-watch system wouldn't be needed, maintenance would be mostly off-board at a base or tender and food could be pre-packed and self-prepared? It makes a big difference: going to a three-watch system bumps the crew up to more like 6 officers and 25-30 enlisted.

[Rick Lowe]

Like the Patrol Boats of WW2, back to base at the end of the day/night/mission.

[jcf]

SR.N4 marks comparison, for anyone inclined to convert the Airfix Mk.1 to one of the others.


You cannot view this attachment.

[jcf]

SR.N2

You cannot view this attachment.

You cannot view this attachment.

[jcf]

SR.N3

You cannot view this attachment.

You cannot view this attachment.

You cannot view this attachment.

[PR19_Kit]

SR.N4 marks comparison, for anyone inclined to convert the Airfix Mk.1 to one of the others.

I'm working on a Mk. III, and have been trying for some years now.

But a look at the diagram will show how many changes are needed. While the tapered hull of the SRN4 is pretty straightforward Whiffing practice, widening the cabin is a real pain, mainly because Airfix make it from SO many parts. You effectively have to build both sides of the cabin first, then add the widened bit before putting it all together.

Those are excellent diagrams JCF, thanks for posting them all together on one place, my data so far is a mish-mash of stuff from various sources, all to different scales of course. 

[Weaver]

Like the Patrol Boats of WW2, back to base at the end of the day/night/mission.

That's the easiest solution, but the problem is that minesweepers sometimes get deployed far from home. In 1991, five RN Hunt class self-deployed to the Gulf. That means sailing 24/7 for day or weeks, which needs enough crew to run a three-watch system for at least basic ship ops and navigation if not combat ops. There's also a bunch of "hotel load" that gets added: food stores, including cold stores, galley to prepare it all, crew to run the galley etc...

Long-distance deployments present another interesting set of question for MCM hovercraft. In Rebuilding The Royal Navy, DK Brown states that MCM(H)s could deploy at 70kts, although the need for frequent refuellings would reduce that to an average of 45kts - three times faster than a Hunt. However that raises the question of where those refuellings actually take place. On a standard fuel load, an SR.N4 could go 160-200 nautical miles at 45 knots. Does this mean that a voyage would have to be plotted between friendly refuelling stops under 200 miles apart? What happens if there just flatly isn't one? On the other hand, if they have to be accompanied by a tender/tanker, then they're limited to it's speed (no faster than a Hunt), otherwise they'll outrun it. Does the navy have to pre-position tankers along the route? What if the MCM(H) are needed in-theatre ASAP, not weeks from now?

I suppose one answer would be to have more fuel capacity on the hovercraft, either fixed, by changing the design, or temporary, by driving a fuel trailer onto it and hooking it up. The standard fuel load is 16 tons. I don't know what all the minesweeping gear weighs, but I'll bet it's less than the weight of cars in the ferry version, meaning there'd be some extra capacity.

[zenrat]

SRN4 based tankers sailing with the minesweepers?

I assume a hovercraft this size can stop, power down and float?  How would it cope with bad sea conditions while doing this?  And could it then power back up and get back up on its air cushion again?

[NARSES2]

I assume a hovercraft this size can stop, power down and float?  How would it cope with bad sea conditions while doing this?  And could it then power back up and get back up on its air cushion again?

Just as I started typing Mr Zenrat beat me to it 

Daft question perhaps, but is a hovercraft a truely ocean going vessel ? If not then how would it get to some of these distant deployments ? A massive hovercraft tender (a normal ship) designed to carry them to the Gulf etc ? And no I'm not being facetious, it's a genuine question. I know the Channel can be rough, but it doesn't come anywhere near the S Atlantic for example ?

Would the RN invest in hovercraft minesweepers if they had a limited sphere of operations ? OK I know in Whiff World they'd have the money to, but again a genuine question.

Chris

[PR19_Kit]

A massive hovercraft tender (a normal ship) designed to carry them to the Gulf etc ? And no I'm not being facetious, it's a genuine question. I know the Channel can be rough, but it doesn't come anywhere near the S Atlantic for example ?

The US Navy already made some ships specially to carry their LCACs around the world.

I'm thinking about the hovercraft equivalent of flight refuelling, how about the tanker 'craft trailing a floating 'drogue' and the receiver having a 'probe' to poke into it?

[Weaver]

SRN4 based tankers sailing with the minesweepers?

I assume a hovercraft this size can stop, power down and float?  How would it cope with bad sea conditions while doing this?  And could it then power back up and get back up on its air cushion again?

Yes, badly and yes, respectively.

The bottom of the plenum chamber is double-walled and largely consists of a flotation chamber, so the craft just becomes a giant raft. Now a raft is stable, but it's no fun at all in heavy seas.

If it's waiting for a tanker to catch up, it might be smarter to stick relatively close to land and then run up the nearest beach and wait there.

[Weaver]

I assume a hovercraft this size can stop, power down and float?  How would it cope with bad sea conditions while doing this?  And could it then power back up and get back up on its air cushion again?

Just as I started typing Mr Zenrat beat me to it 

Daft question perhaps, but is a hovercraft a truely ocean going vessel ? If not then how would it get to some of these distant deployments ? A massive hovercraft tender (a normal ship) designed to carry them to the Gulf etc ? And no I'm not being facetious, it's a genuine question. I know the Channel can be rough, but it doesn't come anywhere near the S Atlantic for example ?

Would the RN invest in hovercraft minesweepers if they had a limited sphere of operations ? OK I know in Whiff World they'd have the money to, but again a genuine question.

Chris

The SR.N4 Princess Anne was damaged by heavy weather in the Channel in 1978. She was only 7 miles off Dover, but she had to go back ot France in order to take advantage of the winds and tides.

A hovercraft facing a severe weather warning in front of it would likely be better off running for the nearest shore and waiting it out on the beach.

[Weaver]

A massive hovercraft tender (a normal ship) designed to carry them to the Gulf etc ? And no I'm not being facetious, it's a genuine question. I know the Channel can be rough, but it doesn't come anywhere near the S Atlantic for example ?

The US Navy already made some ships specially to carry their LCACs around the world.

Thing is, the LCAC was specifically designed to go inside amphibious landing ships, the SR.N4 was not. The LCAC is 47ft wide, the SR.N4 is 78ft wide. The other ship type that carries them is the Expeditionary Transfer Dock: https://en.wikipedia.org/wiki/Expeditionary_Transfer_Dock

To carry something as big as an SR.N4, you'd need something more like the heavy lift ship mentioned in that article: https://en.wikipedia.org/wiki/Heavy-lift_ship
Some of these are wide enough to let an SR.N4 fly aboard sideways, or alternatively, there are some with stern access. If you had to buy a couple of these for the Navy, it would add massively to the cost of the MCM force and they'd spend a lot of their time under-utilised, even if they were also equipped as MCM tenders. On the other hand, if you depend of chartering commercial heavy lift ships in time of need, you risk them not being available because every other navy wants them at the same time for the same reason.

Something like these would be ideal, although it could probably be a little smaller actually:
https://www.yacht-transport.com/yacht-carriers/yacht-express/
https://www.yacht-transport.com/yacht-carriers/yacht-servant/

A ship along these lines could carry, say, three SR.N4 size MCM(H)s along with all the services of a tender to keep them running. it could probably also do other useful work when it's not needed for MCM support. Such a proposal might have gone down well in the early 2000s, with "global policing" on the agenda, the Gulf War exerience fresh in mind, and Public-Private-Partnership deals (PPPs - like the RAF's Voyager tankers) en vogue. A PPP for the MCM(H) support vessels might have the commercial partners using the ship(s) for fee-paying work when the RN didn't need them, as repayment for coughing up some of the purchase cost, possibly with a clause to the effect that at least one was in home waters at all times (Can't move your MCM(H)s quickly if all the tenders are full of yachts on their way to and from the Carribean...).

However in the early 1980s, pre-Falklands, when a decision on SR.N4-based MCM(H)s would have been made, the Nott cuts made it clear that the RN was ONLY going to be focussed on a very tight, WWIII-in-Europe mission. Exepeditionary warfare and "global policing" were firmly off the agenda. An MCM(H) fleet for home waters use might still have gone down well in that context (The Hunts were funded after all, and they weren't cheap), but I couldn't see the government of the day paying for a support ship to take them round the world. Having said that, a case could probably have been made after 1982 in the post-Falklands spending boom, but the Hunts still look like a better bet for long-range deployments to me. They had a support system built into a series of containers that could be shipped anywhere quickly and installed ashore or on a suitable vessel. In 1991 it was installed on the LSL Sir Galahad (newbuild replacment for the Falklands loss), and it performed magnificently, providing tender services for not only five RN Hunts but also USN Avengers and other allied MCMVs.

I'm thinking about the hovercraft equivalent of flight refuelling, how about the tanker 'craft trailing a floating 'drogue' and the receiver having a 'probe' to poke into it?

I don't think it has to be that clever. Both craft can simply come to a stationary hover and then just hand the hose across. All you'd need to do is design a quick disconnect system so that the hose wasn't damage if the receiving craft had to suddenly maneuver and pull away.



EDIT: fleshed it out a bit more.

[jcf]

One of the EPDs, don't recall if it was the Glenn or Montauk Point, was here at Naval Base Everett for the better part of a year on trials, mostly on Puget Sound but also up and down the US West Coast. It was an interesting thing to see.

[jcf]

All of the points raised make it clear why all of the proposed long-range, blue-water ACVs
of various sorts came to nowt.
Operating a fully cushioned craft out in the open sea was always questionable, which is why
Cockerell himself proposed the sidewall hovercraft the rigid sidewalls increasing stability
and making it less sensitive to the vagaries of the weather.
Denny, Hovermarine and Bell all built sidewall hovercaft using Cockerell's basic concept.
Now I wonder if I have anything on sidewall hovercraft and surface effect ships?
🤔
😉