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Captain Pegg

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Captain Pegg last won the day on May 25 2019

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    Vulpes

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  1. I read it that the OP had already bought the boat from Norton Canes (Glascote) brokerage and now couldn't afford the additional work. So is it the case that he's actually selling it through Norton Canes but isn't sure he should? If the risk of hull failure isn't tenable then I agree, sell it.
  2. That is what you need to do. You queried at the outset who you should trust but don't be in any doubt you have bought the boat from someone well qualified to know and who is as reputable as you're going to find. Over-plating is an emotive subject and speaking as the owner of an over-plated craft - where both the original and over plating is of some vintage - I consider a lot of well intended advice is unhelpful. During my ownership I've learnt quite a bit about over-plating and I know of a couple of places who seem to have developed good methods and are experienced in undertaking such work. I'm sure there are others but not all have the same capabilities. I bought my boat in 2015 and speaking to my surveyor during a BSS examination last Friday he suggested it probably has a value tending toward double what I bought it for. To be fair, realising that in the market is another thing because there is always a risk involved. It does have features that make it more desirable to certain buyers than Ramble On but I think it is in indication that an over plated boat is not automatically a basket case. ETA - I think I misread the OPs situation so the first bit probably makes no sense.
  3. But those questions were the premise of the point you queried and the suggestion to go read a book without even bothering to address the actual point I raised I thought was pretty condescending. As it happens I've studied and practiced structural engineering to a high degree so I don't need to be told that box sections are intrinsically good in torsion. I'd far sooner debate from knowledge than from reference material, I want to hear what people really know and understand, warts and all. Save reading up for afterward when you can go and check up on something you realise you maybe didn't know as well as you thought. I still though suspect that if you induced a twist into a narrowboat accidently it wouldn't take that much to cause cabin distortion that could cause internal damage to linings or fittings, and that would be a result of the thin cabin sides and profile. I'd agree it wouldn't get any near failing but as is common in inhabited spaces serviceability criteria take precedence over structural criteria in design. As boxes go they aren't that great.
  4. I totally agree and my knowledge is similar in that while I was once a fully fledged structural designer it was a long time ago. All I said was that I didn't think a narrowboat would withstand being twisted very well - despite the fact that box sections do have intrinsically good torsional capabilities in comparison to other shapes - and that it isn't the prime consideration in any case. Mr D seems to think I'm missing something. He's just posted so let's see.
  5. I have no idea what a bias-cut dress is but I think that's the point. I'm not at all sure that what Google tells me is the same thing you're referring to. Let's leave other people's work out of it since there's enough of that on the forum. I'm just working from what I think I know and if you know better, fine. So assuming I'm wrong - since otherwise what's the point of your post? - what's the answer to the following questions: Does the presence of thinner plates for the cabin structure compared to the hull make a narrowboat hull less torsionally stiff than if the whole thing were made of 10mm plate? Do the (near) right angled corners make it less torsionally stiff than if it were a circle of the same wall thickness and the same internal cross sectional area? Do less torsionally stiff structures deform more under the same load than torsionally stiffer members?
  6. Lifting at two points has never bothered me because there's so much metal in a narrowboat and a good deal of it is well dispersed although it is heavily weighted toward the bottom. I think that if you tried to apply a serious twisting action to a narrowboat hull the roof plate would bend significantly, I don't think there's a whole lot of torsional stiffness there.
  7. The 4-5mm plates welded at near right angles to one another that form the average narrowboat cabin don't really possess much torsional resistance. In any case when being lifted a boat is basically a beam, you are trying not to twist it. What the cabin - and particularly any ribs that run from gunwale to gunwale supporting the sides and roof - will do, is to brace the top edge of the hull to allow it bend without buckling. That is exactly what the chain and cross-plank arrangement on an open hold does, with a much greater degree of structural efficiency, that being the prime purpose of those members.
  8. I watched my boat be slipped on bogies on a tramway last year. The difficulties weren't in the way it was slipped or the way it was supported when in dock but the maneuvering required to extricate the bogies from underneath the boat once on land, which involved use of a jack. The moment pressure was applied to the jack the boat could only ever have been supported in two places. It was hauled out on two bogies anyway.
  9. And of course the centre line wasn't commonly provided on early leisure boats.
  10. I suspect gunwales on early pleasure boats were provided for much the same reason as on working motor boats which is to provide access to the hold (and thence to further beyond) from the stern, remembering that on motor boats the engine room had solid bulkheads whereas on butty boats there was a door from the cabin into the back end of the hold. The gunwales on historic working boats and other properly designed leisure boats are much wider than those on most modern leisure craft. I think a traditional stern without gunwales would be very awkward. I wouldn't want one. It'd be a right pain to reach the front deck without them, involving clambering over furniture with my boots on. I don't use the gunwales to gain access to the roof either, even though there are footsteps for that purpose. I only use the footstep inside the hatch for that. And without the gunwales I'd have to turn the boat around to clean down the cabin sides.
  11. I made no mention of different methods of docking in my first post. I simply referred to situations where the stresses would likely be highest. A boat won't necessarily be on only two supports but it could be - because at times many are - so it represents a worst case in terms of how to calculate the stresses with which a narrowboat hull needs to cope. You wouldn't design it based upon what any particular yard does or any single owner prefers, but on what reasonably might happen.
  12. No plates were punctured in the sinking of the Titanic. And what it mostly explains anyway is why ships are built in steel grades with yield stresses typically twice that of those used in narrowboat construction.
  13. Maintainability is what Tony was referring to but it isn't the same thing as a serviceability design criteria. That is about the ability of an object to fulfil it's user's requirements throughout it's service life.
  14. I was indeed merely referring to the structural elements but I do find that the business of attending to the vagaries of the non-boating sections of the boat detract from the pure enjoyment of owning a boat and going boating on it. I can understand the appeal of a simple life in a boatman's cabin if your objective is to go boating.
  15. Agreed, canal craft are built to serviceability criteria.
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