The Christmas road test: Shannon-class lifeboat

I was lucky enough to see the test boat come ashore at Dungeness - 18 tons of boat hitting the gravel beach at somewhere near 20 knots, and ending up well above the high water mark. It was then just winched onto its trailer. Something incredible to see, but I wonder how many times you can do that to a boat that size if you want a long service life, or is there some form of sacrificial bottom to them?
 
richardsn9 said:
I was lucky enough to see the test boat come ashore at Dungeness - 18 tons of boat hitting the gravel beach at somewhere near 20 knots, and ending up well above the high water mark. It was then just winched onto its trailer. Something incredible to see, but I wonder how many times you can do that to a boat that size if you want a long service life, or is there some form of sacrificial bottom to them?
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I suspect it's not something they intend to do very often. But in the conditions that they are expected to operate in it must be comforting to know that you can just drive her up the beach at full whack at the end of the day.
 
Woodlouse said:
I suspect it's not something they intend to do very often.
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Possibly not at max chat, but running the boat up the beach is how they'll recover it every time. No harbour - that's what the Shannon was invented for.

I believe there's kevlar etc in the layup for protection.

Pete
 
prv said:
Possibly not at max chat, but running the boat up the beach is how they'll recover it every time. No harbour - that's what the Shannon was invented for.

I believe there's kevlar etc in the layup for protection.

Pete
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They have tractor trailers do they not? I would have thought standard procedure would be to drive the trailer into the sea and drive the boat onto it. Save the running up the beach option for when it's rougher.
 
Woodlouse said:
They have tractor trailers do they not? I would have thought standard procedure would be to drive the trailer into the sea and drive the boat onto it. Save the running up the beach option for when it's rougher.
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I could be wrong, but I believe the current beach boats are always driven onto the beach and then hauled onto the carriage. It's quite a performance, too, reminiscent of the building of Stonehenge with seemingly dozens of people, log rollers, ropes and chains. Some stations turn it round balanced on a turntable with a big bloke on a pole each side holding it upright. The new Shannon carriage eliminates most of this with its clever hydraulics.

Pete
 
You'd not specify Kevlar where you'd get that degree of abrasion. Kevlar is very strong, but you'd expect to have a thick sacrificial layer before you get to any Kevlar mat. Back in the 80's we used to used coherent Kevlar Mat (uni-directional) for reinforcement as it was cheaper and you could lay it in the direction you wanted the strength. From memory ,it was great in tension, less so in compression, and where compressive loads were expected we used Carbon. It's strange these days that they are in relatively common usage. We thought them exotic material then.
 
An interesting article I thought, and the clip of the boat beaching at full chat is amazing.

It's worth also looking at this clip showing the launch and recovery of the Shannon. http://www.youtube.com/watch?v=Aiqyxa7NYpE The way the cradle is elevated at launch so the boat hits the water with some speed, must really help to get clear if there's a bit of a sea running. I would imagine that the recovery part of the clip is probably closer to a typical beaching than the one of it being run up the beach at 20 kts. It's worth watching the clip to the end to see the boat being turned in the cradle so it's ready for launching.

Compare it to this footage for launch and recovery of an earlier generation of boats http://www.youtube.com/watch?v=v1cw0u8sye0

Finally, if you look on this clip at about 1:50 you can see the crash stop that the shannon can do which is mentioned in the article being performed.
http://www.youtube.com/watch?v=AEYldlpb_FQ

In all, it certainly helps to answer some of the questions raised elsewhere on this forum regarding the costs of Shannon, and demonstrates what an excellent piece of kit it is.
 
The launch looks fiddly and I would imagine difficult to do if there was a serious storm and heavy seas on the beach.

I thought this is why lifeboats lived at the top of big ramps like this one:-

boathsewhole.jpg
 
michaelchapman said:
The launch looks fiddly and I would imagine difficult to do if there was a serious storm and heavy seas on the beach.

I thought this is why lifeboats lived at the top of big ramps like this one:-
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So what do you do when the bottom of the ramp comes down to half a mile of sand and mudflats at low tide?

Different sites need different kinds of launch. The beach boats will launch from different spots depending on the state of tide - and in some places the wind direction. I believe one of them drives up to a mile to one of its possible launch points.

Others lie afloat, where there's a harbour to put them in. There are slipways, where there's no harbour but the sea doesn't retreat too far at low tide. And there's even one site where they lower an all-weather boat down a wall from davits.

It all depends on local conditions.

Pete
 
Topcat47 said:
You'd not specify Kevlar where you'd get that degree of abrasion. Kevlar is very strong, but you'd expect to have a thick sacrificial layer before you get to any Kevlar mat. Back in the 80's we used to used coherent Kevlar Mat (uni-directional) for reinforcement as it was cheaper and you could lay it in the direction you wanted the strength. From memory ,it was great in tension, less so in compression, and where compressive loads were expected we used Carbon. It's strange these days that they are in relatively common usage. We thought them exotic material then.
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Topcat47,

I've never been involved with the construction, but if bullet-proof vests are kevlar as often quoted, surely that's one of the ultimate compressive loads ?!

As for the lifeboat beaching, surely that's a handy emergency move; I can't believe even the RNLI would throw money away like that every time ?
 
It looks like a standard medium vee hull, so what's so special about it?

What are those wierd looking bilge keels on the aft section?
 
Seajet said:
As for the lifeboat beaching, surely that's a handy emergency move; I can't believe even the RNLI would throw money away like that every time ?
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Nope, it's what the boat is specifically designed to do. They've been recovering their "carriage boats" like that since the days the carriages were pulled by horses or bullocks. Admittedly they may not beach at full throttle every time, but if it's rough then they'll want to get well up out of the breakers ASAP.

Don't understand why you think money has something to do with it?

Pete
 
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