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

[Weaver]

A thread for info/discussion on British hovercraft, i.e. the ones produced by Saunders-Roe, British Hovercraft Corp, Griffon, Vosper-Thorneycroft, Vickers etc...

I'm going to start by transfering info here from the SR.N4 discussion on the Airfix thread, occasioned by the re-release of their 1/144th scale kit.

Good info pages on the SR.N4 here:

https://www.jameshovercraft.co.uk/srn4#
https://www.bartiesworld.co.uk/hovercraft/index.php

[Weaver]

There was a plan for an SR.N4 minesweeper in the 1970s. There's a drawing in Rebuilding The Royal Navy by DK Brown & George Moore. A lot of testing was done, including exploding 1100lb charges near the old SR.N3, which it survived remarkably well. Ship Dept of the RCNC (Royal Corps of Naval Constructors) were enthusiastic, but the naval staff and sonar teams were opposed. The debate was long and bitter, but Ship Dept lost in the end.

Secret Projects has a thread about it: https://www.secretprojects.co.uk/threads/srn4-hovercraft-concepts.10966/

Images from that thread:

[Weaver]

Colation of info from the other thread, mostly from Kit and me:

Kit: You can't stand on the roof when they're moving. Props are the largest ones ever made. The grey strips on the roof are rubber-coated walkways.

Image by Kit showing the walkways:




Kit: It didn't matter how close they went to props as no-one was allowed on the upper deck with the engines running anyway. I expect the roof structure wasn't all that strong in the other areas, just like 'No Step' areas on aircraft wings.

Kit: They had maybe 15+ 'house staff' aboard the Mk III I worked on, but I also noted that some got off just before they closed the doors. Maybe the car handling people stayed at the bases as they weren't needed during the crossing itself.

Weaver:  Cockpit ladder was changed from folding to fixed partly in order to act as an extra brace for the roof!

Kit: The cockpit was very 'friendly' with four of us in there. The nav's position, right at the back, is over to one side as all his nav kit take up half the wall on the starboard side. At least the Captain and First Officer have the sort of room you'd find in a small airliner, or a helicopter, but there was precious little room anywhere for a 'supernumerary hydraulics engineer'!

Weaver: In the kit, the nav sits facing sideways, but I noticed that in one of the pics on Jame's website, there are two seats in the back of the cockpit facing forewards. One of them is clearly the nav position, since it has the two radar screens, but there's no explanation of the other one.

Kit: The engine rooms were NOT manned while it was operating.

[Weaver]

My various thoughts on converting the Airfix kit to a minesweeper/minehunter (MCM(H) ) as per the artwork in post 2:

a) There are several different configurations in the various pictures I posted up-thread.

b) I don't know nearly enough about 1970/80s minesweeping/hunting to pick all the gear needed to fill up the interior (and it does need filling up, given the clear roof).

c) None of the craft the minesweepers are based on are "pure" SR.N4s: they have things like extra walkways and railings around the sides and rear, different skirts, modified exhausts (presumably so they don't roast people on the rear walkways) and (sometimes) a fin-like mast with radar and aerials on it.

If I do it, it might be a composite of them all, which will be a compromise between what I like the look of, what makes sense, and what's possible/easy to source.

I do like the one with 20mm Oerlikons in cut-outs either side of the bow.

All other things being equal, their "moment to shine" as minesweepers would be off Kuwait in the aftermath of the 1991 Gulf War, so by then they'd be on the other side of Gulf War UORs, and 10 years of in-service mods, and 15 years on from the concepts in those drawings. (Note I got the timescale a bit too early in my original post: MCM(H)s would have entered service late 1970s/early 1980s).



Possible features that occur to me:

1. IR shielded engine exhausts, a bit like those on a front-line helicopter. These could extend over the rear walkway, as per the drawings, but I wouldn't need to build upswet tube exhausts for them: just Apache-esque boxes.

2. The 20mm gunners, standing on open platforms at vehicle deck height at the front, are going to have a pretty miserable time of it when the craft is trapping on at 60 kts in any kind of seaway. Things to mitigate that might be to replace the deck-edge railings at the front corners with 4-5' high solid screens, and fit windscreens to the 20mm shields.

3. Decoy launchers.

4. Extra GPMG positions (rear corners?)

5. Javelin MANPADS LML positions on either side.



I wonder how the RN would have organized the crew for an MCM(H)?

The bridge/cockpit of the SR.N4 is pretty small, and seats the pilot, the engineer and the navigator. The pilot is the captain of the craft, just like in an aircraft, and that's fine for a 35min trip from A to B. However minesweeping and minehunting are far more ship-like activities, and while I'd expect the captain to be in the CIC during combat ops, they generally divide their time between the CIC and the bridge. Would the navy insist on having an "officer of the watch" position on-the-bridge/in-the-cockpit and how would that be accomodated?

Related: does anyone know what the crew of a civvie SRN.4 was? None of the references seem to say. They all claim three in the cockpit, but how many more were knocking about looking after the car deck, the engines, the passengers etc? Hunt class MCMVs had a complement of 45 (6 officers & 39 men) but they had a much greater endurance, so they needed enough to operate a three-watch system, provision for a galley with a cook or two, and more engineers to do more on-board self-maintenance.


In the kit, the nav sits facing sideways, but I noticed that in one of the pics on Jame's website, there are two seats in the back of the cockpit facing forewards. One of them is clearly the nav position, since it has the two radar screens, but there's no explanation of the other one.

Perhaps since an MCM(H) would have an ops room, the nav could be moved down there, leaving room in the cockpit for an Officer Of The Watch? I can't imagine the Navy being okay with not having an officer on the "bridge" so if that's not possible then they'd have to follow aircraft practice and the pilot would have to be an officer at least. That kind of makes sense given the amount of training and responsibility involved, actually. That in turn implies at least six officers on the crew (one in the cockpit, one in the Ops room, three watches), so maybe the MCM(H) would have a higher ration of officers to ratings than a Hunt (5 and 39, respectively).

[Weaver]

There's a guy selling masking sets for the SR.N4 on ebay. Handy if you're doing the many-windowed passenger version, and don't forget, the entire bridge and the cars are clear plastic, so they'll require fiddly masking too.

LINK

[jcf]

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[jcf]

A scan from Jane's Surface Skimmers 1976-77. In this layout all of the equipment, and a control cabin is installed within the car deck hold, apparently the passenger cabin spaces would be used for other things. The other layout, the one with the big magnetic loop, shows the entire hold being used for the equipment, the passenger cabins being removed.

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[jcf]

BH.7 Mk. 5A 

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[jcf]

As to crew, the Imperial Japanese Naval Air Service multi-engine land-based bombers
and large flying boats had a pilot, co-pilot and an aircraft commander who sat behind
the pilots.

[jcf]

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[jcf]

Internet Archive Janes's Surface Skimmers

Several volumes are free to borrow after you create an account.
Duplicates of 75-76, 76-77 and 79. Different scans.

[Weaver]

Cheers for all that Jon.

Think I already posted that first one in the second post, but yours is sharper. I don't particularly like that interior layout since it leaves a relatively short working deck aft and blocks off all but personnel access to the forward deck/ramp, for no particular reason that I can fathom. I do like the 20mm guns in the front corner cutouts though, and I also like the fact (purely for ease of build purposes) that it uses the standard SR.N4 ferry radar and mast setup instead of adding an extra mast like the others do.

I wonder what those four cubicles on either side of the main compartments are? Surely not heads - they wouldn't need eight for a relatively small crew and the SR.N4 already has four located in the side areas fore and aft.

That BH.7 cutaway is very useful since it shows what they think is neccessary in an Ops room for pure minsesweeping: chart table, horizontal plot and a radar console. You might add an ESM/ECM/Decoys console if the craft's so equipped, and a comms console. For mine hunting you'd need at least one (more like two) sonar consoles and a console for controlling an ROV, but they might be in a separate room (sonars often are).

My current feeling is that the best place for an ops room in an SR.N4 is forward, just behind the cockpit ladder, and offset to one side. That way you've got quick access between Ops and cockpit while preserving half-width access to the front ramp.

[PR19_Kit]

Good idea posting this new thread H, a topic that's not really covered under 'Aircraft' or 'Ships'. 

The two diagrams that JCF posted, the 1964 and '65 designs are interesting as they seem to presage pretty much what BHC did to convert the original Mk Is to the Mk IIs in 1972, that is eliminate the inboard passenger spaces to make room for more cars and widen the outer shell to restore the passenger space. They were obviously thinking well ahead.

One item that's singularly missing on the BH7 diagrams is the microwave cooker. 

Yes really. The only BH7 that was ever bought by the UK MoD, which is the one at the Hovercraft Museum at Lee-on-Solent today, XW255, has the first ever microwave cooker ever installed in any British Forces anything, vehicle, house or shed. It's located in the port side forward corner of the craft and is 'Security Protected' behind TWO interlocked hatches, and can't be operated with anyone actually inside the same compartment!    Such was the fear that such devices engendered back in the late 60s-early 70s.

The guide at the Museum gleefully demonstrates how thick the hatches are and how 'secure' the cooker is during the tours of the craft. 

I've been lucky enough to travel aboard every one of Saunders-Roe's/BHC's hovercraft designs, except the BH7, and of course the original SRN1.

They used the SRN2 and SRN3 for short times on the Isle of Wight services across the Solent, and it was pure chance I travelled on the SRN2, and subsequently kept a look out on their schedules to try out the other types, starting with the SRN5s and then the longer SRN6s. The SRN3 was distinctly rudimentary inside its vast hull as the seats looked like they'd come from a bus rather than the aircraft style seating on the SRN2-5-6 etc. but it seemed it was just tested as a trial for using larger hovercraft for passenger use.

[Weaver]

The other layout, the one with the big magnetic loop, shows the entire hold being used for the equipment, the passenger cabins being removed.

Just for clarity, the teardrop-shaped "loop" shown in the "through deck" version isn't the "magnetic loop" mentioned in the text. I believe it's an overhead I-beam with a travelling winch on it, used for moving gear around: look at how the floats in the front of the bay are positioned exactly under it. I think that in the sketch I posted (pic 1), they had the idea to extend these tracks out over the stern, supported by A-frames, and use them instead of conventional derricks to deploy the sweeps. However this has downsides:

1. any gear carried on them has to fit between the A-frame legs (questionable for a Gemini)

2. the cables would have to be attached after the load reached the end of the track, to avoid the cable being fed through the A-frame. This would mean attaching the cable to a swinging body by leaning over the railing of the extended central platform: an accident waiting to happen.

In the cutaway (pic 2) and the plan view (pic 3) the layout is modified, with the track ends sweeping inboard to depoist the load near the centre of the sweep deck, and two conventional derricks at the aft corners of the sweep deck to pick them up and deploy them. This is more time-consuming (two lifts instead of one) but avoid all the pitfalls: cables can be attached while the load is on the deck and the load can be of any practical width.

The magnetic lopp used for minesweeping is a loop of buoyant cable some 500+ yards long, towed behind the ship. The buoyance sleeve around the cable makes it very fat, which explains why the cable drum for it is so big. here's what it looks like deployed (from a Ton-class, but the Hunt setup is probably similar):

[RAFF-35]

Has anyone here read "The Foresight War"? Essentially someone travels back in time to WW2 and influences tactics and vehicle designs etc. I'm pretty sure the main character tells the UK government about hovercraft,  and something very similar to the SR.N4 takes part in the amphibious assaults in mainland Europe.