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Theo

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Posts posted by Theo

  1. 5 hours ago, system 4-50 said:

    from Wiki:

    For nearly all models of induction cooktops, a cooking vessel must be made of, or contain, a ferrous metal such as cast iron or some stainless steels. The iron in the pot concentrates the current to produce heat in the metal. If the metal is too thin, or does not provide enough resistance to current flow, heating will not be effective. Induction tops typically will not heat copper or aluminum vessels because the magnetic field cannot produce a concentrated current, but cast iron, carbon steel and stainless steel pans usually work. Any vessel can be used if placed on a suitable metal disk which functions as a conventional hotplate.

     

    That, to me as an ex physics teacher, looks all wrong.  Iron does not concentrate current.  It has a higher resistivity than copper or aluminium but the current will be distributed through iron in the same way as through other metals.

    8 minutes ago, Theo said:

    That, to me as an ex physics teacher, looks all wrong.  Iron does not concentrate current.  It has a higher resistivity than copper or aluminium but the current will be distributed through iron in the same way as through other metals.

    Hm...

     

    I had ignored the skin effect.  Thanks all.  As said, more research required.

     

    N

  2. I have been cogitating on the idea of an induction hob on the boat.  We have recently bought a new cooker for our house kitchen with an induction hob for the house and have fund it completely excellent.

     

    I have looked up the literature on how they work and all the articles say that they work by the induction of eddy currents in the base of the pan.  If this is the case they should work perfectly well with any metal pan.  This is not the case.  They don't work with thick or thin ground based or otherwise aluminium pans.  AFAICT they only work with ferro-magnetic based pans.  We have one or two cast le Creuset pans and they work perfectly.  The new ones that we bought are, presumeably, a ferro-magnetic stainless steel.

    This indicates to me that eddy currents pay little part in the heating.  It also indicates that a more likely heating effect is by the repeated magnetic cycling giving rise to hysteresis "losses". When we use our new pans on our induction hob they make sometimes make a low buzzing noise as the coils in the cooker are energised.

    I would be really interested to hear other people's views on this.

     

    Nick

  3. 13 hours ago, Tony Brooks said:

     

    Unless the design has been altered, the seal is a carbon ring in a rubber diaphragm pushed onto the back of the impeller by a spring, a bit like the PSS shaft seal. The diaphragm allows the seal to "wave about" yet still stay on the back of the impeller. i don't find it strange, but you were very wise to swap the pump. FWIW unless you have a decent press and a degree of skill to remove the impeller, changing the bearing is not as easy as some here seem to think. You also need to change the seal assembly.

    Thanks, Tony.  Always helpful and to the point!

     

    Nick

  4. On 23/08/2023 at 20:23, mrsmelly said:

    Well to be honest its non of the above :) The nearest would be cassette but my preference without a doubt as a long term liveaboard was Porta bogs, so closest here is cassette so I will play along and tick it :P

    Ditto.  As long as I could get one with a couple of spare holding tanks.

  5. 6 minutes ago, IanD said:

    And the anchor type/weight?

     

    Danforths and similar are cheap and very common but not very effective for their weight -- or looked at another way, the ones used are often too light for a 60' narrowboat because a heavy enough one is pretty unmanageable... 😉

     

    (before anyone asks me -- 10kg Kobra + 5m of 8mm chain + 25m of 14mm anchorplait...)

    16kg danforth

     

  6. Having just come up the Severn and the Avon the fact that my cooling water pump has just failed emphasized how important it is to have an anchor ready to be deployed.

     

    We are on the North Stratford now and the engine cooling water pump is defunct but it is a manageable problem.  If it had happened on the Severn and we hadn't had the anchor ready it would have been life threatening.  On wide rivers like the Severn and the Trent we have the anchor at the front.  On these rivers, if you are going downstream there is room to be brought up and swing round head to the current.  On narrow rivers like the Avon and the Soar we have the anchor at the stern if going downstream.  Not ideal but better than being unable to turn and wedging right across the river with the current trying the capsize us.

     

    I know that this topic has been aired before but I think that it's worth saying again that on a river an anchor is an essential piece of safety equipment and needs to be ready for deployment in an emergency. 

     

    I frequently pass boats with the anchor neatly stowed on the roof with nothing attached to it.  Even if the crew know exactly where the chain cable and warp is it will take several vital minutes of panicky work to get it ready to deploy.

     

    N

    • Greenie 3
  7. 18 hours ago, Alan de Enfield said:

    Good as in he is thorough and ensures everything is safe and compliant?, or

     

    Good as in he sits in the cabin has a cup of tea and some choccy biscuits and writes out the 'pass' certificate without looking at the boat?

    Tempting just to say the former.  Certainly not the latter.  The former but leavened with common sense would be good.

  8. I really do need to sort out the horrid state of the engine hole.  The issues as I see them are:

     

    • I had a leaky exhaust pipe which sooted things up a bit.
    • There is lots of frass from the drive belts.
    • The swims need painting scraping and painting

    What's the best way to start?

    Steam clean?  Will that damage the electrics?

    Solvents?  Will they damage plastic bits?

     

    Polluting the cut should not be a problem because I han direct the bilge pump into into a plastic can.

     

    All hints and tips gratefully received.

     

    Nick

  9. I have solar with a Victron SmartSolar HQ204684PFB controller and an Adverc.  I don't think that either of these are adjustable for a lower charging voltage.  I will have another look to see if I can disable equalisation if this is advisable.

     

    The Adverc manual says that it keeps the charging voltage down to 14.4V alternating with 13.something.  The 14.4V is OK for the batteries.  The error starts showing when we are an hour or so into the day's cruise and the SG is showing about 97% SoC.  I haven't seen the voltage go over 14.4V.

     

    It seems to me that I can disable the E03.  Am I correct?

     

    N

  10. Theodora has a triple drive belt from the gearbox to the prop shaft.  I have jsut replaced it with the spares that I keep on the boat and now need to buy a new set.  Trouble is there is no legible code on either the old set or the new set.  So what do I ask for?

     

    I would imagine that I would cut oneof the old belts so that I can measure its length accurately and measure the width of the pulley groove.  Will that be enough information to give to the supplier?

     

    They are a bit of a sweat to replace.  What do you think of the PowerTwist belts? Being able to "break" the belt would save my having to unbolt one of the Plummer blocks.

     

    N

     

     

  11. On 28/07/2023 at 09:16, Jen-in-Wellies said:

    I read the title and my first thought was Leeds and Liverpool.

    Ditto

    On 30/07/2023 at 08:54, Tonka said:

    Back pumps from the sea upto the lakes from both sides. It is not rocket science

    Not a good idea to put sea water into a sensitive FW habitat.  However a commercial advantage would be that you could load the ships more heavilyif the cana became saltwater instead of fresh.

  12. On 05/06/2023 at 11:19, BEngo said:

    I have had poured concrete since 1989.    It has given me no troubles.  I know of a number of other boats with it, again, they have had no trouble. 

     

     Like everything, it needs to be done well to be durable.  There are a number of lumpy water boats made  out of ferro concrete where a concrete shell is sprayed or trowelled over a steel rod frame.  They are insurable if they have been maintained.  There are even some concrete canal craft dating back to WW1. There are thousands (millions?)  of reinforced concrete structures from bridges to car parks around the world and where these are constructed to a good design and properly maintained they have given good service for many years.

     

     

    There are negatives:

    You must plan ahead.

     

      Adjusting concrete ballast is noisy, and you need to take the floor up.  You dont need a pneumatic drill though.  A Kango hammer is quite enough.

     

    You have to think long and hard about how much you need and the overall trim.   I left myself needing about half a ton of extra loose ballast, which was handy for trimming..  This has nearly all gone overboard  over the years, p as middle age spread has set in.

     

    The steel needs to be properly clean, and ideally cement washed before the main pour goes in.

     

    You need to work quickly  get it in,  pokered and vibrated solid.  It is physical work.  Bulk concrete goes off quite fast, especially if it is warm- so dont sit down for a brew after the truck driver has shot the load into the bottom.

     

    Would I do it again?  Only if I could not get hold of some lead or steel blocks instead.  If the only alternative was bricks or paving slabs, certainly.

     

     

    N

     

    When we were down at Sharpness a few days ago we went to view the Purton Hulks.  The ferro-cement barges which had been deliberately holed and left there to reinforce the bank we much the best preserved.  In fact, apart from the holes in them they looked perfect.  Built in 1941 and in the weather and not maintained ever since.  Perhaps we should try ferro-cement narrowboats.  They wouldn't need any extra ballast and wouldn't have much room inside either.  The ferro-cement was very thick (about 4"?)

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