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

[PR19_Kit]

Too right I have! 

I've actually got two copies of it, and both are pretty well worn out.

The description of the big hovercraft troop carriers crossing the Normandy beaches in D-Day is hilarious, described from the point of view of a Wehrmacht trooper who gets 'hovered over' by one! 

[Weaver]

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.

Yep - read it cover-to-cover several times, and I've actually met Tony Williams who wrote it. He's a cartridge/shell-case collector who's also written some excellent books about guns, including the "Flying Guns" series about the development of aircraft armament.

His website's pretty good too: https://quarryhs.co.uk/home/index/

Foresight War page: https://web.archive.org/web/20220126212747/https:/quarryhs.co.uk/TFWreviews.htm

I have a couple of detailed Merlins in the stash and it's always been a vague idea of mine to make a model of the Foresight War hovercraft. Modelling the skirt is the same barrier to that as it is to every other scratchbuild hovercraft project though.

[PR19_Kit]

Modelling the skirt is the same barrier to that as it is to every other scratchbuild hovercraft project though.

Hmmm, I wonder how the skirt from my 1/72 Trumpeter LCAC would fit on a 1/144 scale Mk III SRN4.................. ?

[Weaver]

Modelling the skirt is the same barrier to that as it is to every other scratchbuild hovercraft project though.

Hmmm, I wonder how the skirt from my 1/72 Trumpeter LCAC would fit on a 1/144 scale Mk III SRN4.................. ?

It's a bit hard to tell because the skirt in the Airfix kit is broken up into so many sections, but if it's any help, the plate that the skirt fits onto is 400mm long and 133mm wide.

[Weaver]

I always envisaged the hovercraft in The Foresight War being really crude and brutal, more akin to an LCAC thrown together at the last minute than an SR.N4. All struts, square boxes and canvas screens. I know the text says the ramp is below the cockpit, but it really makes much more sense to have the LCAC layout with the cockpit to the side and an open-topped vehicle deck with no height restriction.

It's described as carrying a 45 ton "Churchill" tank (not the same as the real life Churchill). That's roughly 2/3rds the load of an LCAC. The LCAC as originally built had 17,560 shp, so the WWII version would need about 11,700 shp, if it was to have the same speed (40 knots with full load, 70 knots empty). That would need eight 1,500 shp piston engines, which sounds doable: two on each side driving propulsive props and two on each side driving lift fans. The text says the engines were stripped from decommissioned Spitfires, so presumably the propulsion ones would be mounted on the tops of pylons with their original props in place.

[zenrat]

You got an extra slash in your Foresight War link H.

[Weaver]

You got an extra slash in your Foresight War link H.

Hmm, how odd...  Anyway quite right, and I've fixed it now - cheers! 

[jcf]

I always envisaged the hovercraft in The Foresight War being really crude and brutal, more akin to an LCAC thrown together at the last minute than an SR.N4. All struts, square boxes and canvas screens. I know the text says the ramp is below the cockpit, but it really makes much more sense to have the LCAC layout with the cockpit to the side and an open-topped vehicle deck with no height restriction.

It's described as carrying a 45 ton "Churchill" tank (not the same as the real life Churchill). That's roughly 2/3rds the load of an LCAC. The LCAC as originally built had 17,560 shp, so the WWII version would need about 11,700 shp, if it was to have the same speed (40 knots with full load, 70 knots empty). That would need eight 1,500 shp piston engines, which sounds doable: two on each side driving propulsive props and two on each side driving lift fans. The text says the engines were stripped from decommissioned Spitfires, so presumably the propulsion ones would be mounted on the tops of pylons with their original props in place.

Something along the lines of a mashup between the Bell Canada Model 7380 Voyageur and the Enfield Marine HM-1?
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[jcf]

EM-2, two Deutz 12-cylinder turbo-diesels or two Waukesha T400 industrial gas turbines.

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[jcf]

SARO/BHC for RN. Stretched SR.N3 on a pancake. 😉
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[jcf]

Early SR.N4 concept.

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[Weaver]

I always envisaged the hovercraft in The Foresight War being really crude and brutal, more akin to an LCAC thrown together at the last minute than an SR.N4. All struts, square boxes and canvas screens. I know the text says the ramp is below the cockpit, but it really makes much more sense to have the LCAC layout with the cockpit to the side and an open-topped vehicle deck with no height restriction.

It's described as carrying a 45 ton "Churchill" tank (not the same as the real life Churchill). That's roughly 2/3rds the load of an LCAC. The LCAC as originally built had 17,560 shp, so the WWII version would need about 11,700 shp, if it was to have the same speed (40 knots with full load, 70 knots empty). That would need eight 1,500 shp piston engines, which sounds doable: two on each side driving propulsive props and two on each side driving lift fans. The text says the engines were stripped from decommissioned Spitfires, so presumably the propulsion ones would be mounted on the tops of pylons with their original props in place.

Something along the lines of a mashup between the Bell Canada Model 7380 Voyageur and the Enfield Marine HM-1?

Kind of, but wartime-expedient crude. I see it having fixed tractor props on the top of latticework pylons, with big rudders behind them, one at each corner. That's the most expedient way of using salvaged aero engines while keeping airflow through the radiators. The lift engines would be in the middle of each side bay, with centrifugal fans pulling air through their radiators.

Personally I like the Voyager layout and would probably go for it given a free hand. It's rather remieniscent of Florida airboats, with the pilot sitting up high at the back. With anything from The Foresight War, there's a tension between whether to try to make Tony's vision faithfully or to use it as a jumping-off point for your own ideas. Me and my firend sat down with him in a pub and had a long talk about all of this, and it was apparent that a) he's stronger on some subjects than others (he's a guns guy at heart) and b) he's acutely aware of this and very open to constructive feedback.

I feel that using Merlin power-eggs (as seen on the Lancaster and Beaufighter) would be better for the thrust engines since they have the radiator and all ancilliaries packaged nicely together, making integration easier.

[Weaver]

SARO/BHC for RN. Stretched SR.N3 on a pancake. 😉
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That would have to be run the same way as the BH.7 minesweeper, with extra gear (long-arm cranes) to stream the sweeps from the side decks. It'd also be relatively awkward to move gear from one side ot the other. I think the centreline stern bay of the SR.N4 layout is WAY better for minesweeping.

What that layout would be good for is combat roles, with anti-ship missile cannisters and light guns on the side decks. The BH.7 had an option for a narrower front cabin for exactly that purpose and some of the ones bought by Iran had that layout.

[Weaver]

Early SR.N4 concept.

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The SR.N3 had pretty much that flat-iron shape, but smaller and with two props. That was the one the Inter-Service Hovercraft Trials Unit y did most of the RN tests with in the 1970s. After they'd finished with her they used her for mine-damage testing and she held up remarkably well. The last one was 1100lb just beyond her skirt. When they reboarded her, she was still hovering and the commercial radar and radio still worked.

You can see why they went to four props for the final SR.N4 design though. Drive-on, drive-off car/cargo bay, smaller number of bigger engines, the advantages (as a ferry) are obvious.

[Weaver]

Something along the lines of a mashup between the Bell Canada Model 7380 Voyageur and the Enfield Marine HM-1?
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Now that lifts 40 tons and can still do 30-45 knots on only 3000 hp. This is the thing with hovercraft: the lift power requirement is proportional to the mass, but the propulsive power, once you've got it up on that near-frictionless air cushion, is pretty much whatever you want it to be, much like a spacecraft. This thing has WAY less power than an SR.N4, for about 25% less speed. I'll bet it's acceleration at max weight is MUCH slower though.

This is interesting for the Foresight War hovercraft. Maybe if a slower speed and acceleration is acceptable, the WWII hovercraft could have much less installed power than I suggested in an earlier post, and would need far fewer engines: maybe only four early (1100-ish hp) Merlins, two for lift and two for thrust.