Monday, 29 April 2013

18th century hovercraft?

It would be hard to detail here all of the many, many ideas we have had, some good, some bad, in answer to the technical challenges of lifting the boat and removing it from the cellar. The team at MNH includes Steve Blackford, Head of Properties and his colleagues, and, very importantly, the Technicians, led by Geoff Mitchell. So much thought has gone into our plans that we often forget how we got here. One of our contractors asked this week "Why can't you just take the boat apart and re-assemble it somewhere else?"

How not to take a boat apart # 327

It's a perfectly reasonable question, after all. The answer is that we are trying as hard as we can to preserve what we'd call Peggy's 'archaeological integrity' - that is, all of the tiny relationships between every tiny element she's made of. We know she's a very significant boat but we don't know everything about her, so we are trying to keep as much of the evidence as possible. However carefully we tried, taking her apart would damage her a lot, and that would defeat the point of moving her.

Lately Geoff and I have been thinking hard about the way that Peggy, in her steel support cradle, will slide out of the boat cellar. We are shortly going to lay rails on the cellar floor that'll eventually lead out of the door and into the yard. We have to try to get the rails precisely aligned with each other and on the correct slope. There'll be three rails including one in the centre under the keel. Geoff has designed Teflon pads that the cradle will sit on to help it slide down the rails. Now, obviously we don't want that to happen too soon (!) because the boat will be sitting still for a year or so while we prepare the site for her exit. The pads are not so slippery, nor the slope so steep, that the boat won't stay put. How then to get it moving when the time comes without causing it to judder and shake?
Geoff has invented an ingenious solution to this problem. Each Teflon pad will be fitted with a compressed air inlet. The underside will have grooves in it that will let the compressed air escape, very much like a hovercraft but without the rubber skirt. We calculate this will provide just enough lift to get the boat moving down the rails. Turning off the air supply will act as a brake. Rest assured we will film the device in action so you can see it.

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