Rudder for Thames barge hardware etc.

Discussion in 'Boat Design' started by Alfie, Mar 12, 2020.

  1. Alfie
    Joined: Mar 2020
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    Location: Falmouth

    Alfie New Member

    Hi all,

    I'm making a rudder for a newly acquired replica steel Thames sailing barge built in 1992. It's been on the hard for a few years, and the old wooden rudder rotted out and was thrown away a long time ago. There is a large steel bushing/bearing welded to a projection of the skeg, and two gudgeons further up the transom. I have the builders drawings for the boat, which give me a general idea of the rudder shape and size - it's not terribly complicated, but it is big and heavy at about 1200mm long and ~2400mm top to bottom. I'm going to make it from greenheart salvaged from Falmouth docks, splined and through bolted fore-aft with several lengths of 16mm stainless stud. I'll make galvanised pintles and gudgeons with straps that extend ~2/3 of the way across the rudder to further strengthen it. The gudgeon on the bottom will take the (substantial) weight of the rudder and the two gudgeons higher up will keep everything in line with a long loose pin to fix everything in place. I'm fairly confident this all makes sense, although if anyone has any input it would be much appreciated.

    The part I'm a bit stuck on is the bottom bearing. The gudgeon/bearing there is just steel, and a bit rusted. As far as I can tell its original bore was 40mm. I've attached a quick sketch of the arrangement. I would like to make all the hardware in mild steel, and have it galvanised, as this seems most in keeping with the boat and is cheaper. However, this means I'd have to make a pretty generous fit at the bottom gudgeon, which would inevitably rattle and wear the galv off in short order. There also won't be any meaningful protection for the moving parts beyond the stickiest grease I can find, and a stainless thrust washer. Is this an issue? Will constant movement and annual greasing keep it sweet?

    Another option could be to press fit a delrin top-hat bushing to the bottom gudgeon, and make a stainless pintle that will fit in it snugly and stay smooth and round. I would then worry about rust swelling the between the gudgeon and bushing making the fit really tight, and wearing out the bearing in short order. I would also have to make the bottom pintle/strap in stainless, which isn't that appealing. Would a galvanised pintle in a plastic bush wear the plastic so fast as to be pointless? It seems like a horrible bearing surface.

    Any thoughts on how best to make this? I would definitely rather go with something simple, cheap and robust than anything too engineered, but I only want to do this once.
     

    Attached Files:

  2. gwboats
    Joined: Sep 2005
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    gwboats Naval Architect

    Hello Alfie, welcome to the forum.
    Just a quick note to say that the old Thames barges usually did not have a bottom pintle. Their arrangement was to have 3 pairs of of gudgeons on transom and rudder all connected by a steel round bar about 2" (50mm) diameter droped through. The reason for this was that these old barges took the ground a lot when working and the rudder was free to lift a few inches if the bottom was particularly uneven. The worm gear steering at the top was also articulated to allow for this vertical movement.
    For your case though I would not advise using stainless steel underwater for this application but fit bronze bushes to mild steel pintles. If all the steel is hot dipped galvanized (except bearing surfaces) and the steering is worked regularly you should get many years of reliable service.
    Good luck.
    G
     
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  3. gonzo
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    gonzo Senior Member

    Old boats had gudgeons and pintles with a rather loose fit by modern standards. As previously mentioned, if the rudder gets used, rust will not build up enough to seize it. Can you post a photo of the barge?
     
  4. MikeJohns
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    MikeJohns Senior Member

    A lot of commercial craft of all sizes use steel ( rather than S.S.s) rudder shafts. Grease, epoxy paint and an anode will see then last often for longer than S.S., there are some good inert plastics that make excellent bushings these days. Tap any bushing for a Grease zerk and put a blanking bolt in while in service. Haulout extra work is to check the anode, take blanking plugs out screw in a grease zerk and give a few pumps, wipe of the excess grease.
     
  5. gonzo
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    gonzo Senior Member

    Dumping grease in the water is a major no no. It is illegal.
     
  6. MikeJohns
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    MikeJohns Senior Member

    That's why the excess is wiped off. Important part of the spec these days !
     
  7. gonzo
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    gonzo Senior Member

    Greasing an underwater bushing is a thing of the very distant past. If you need a tighter fit, use a cutlass bearing.
     
  8. MikeJohns
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    MikeJohns Senior Member

    What regulations say that ?

    Grease is a necessary requirement of a lot of immersed equipment, it’s even permitted to use non environmentally acceptable lubricants if it’s the only feasible option.
    There’s a number of marine greases that meet what is termed the Environmentally acceptable marine lubricants requirement for immersion in contact with seawater, even under the USA’s EPA rules. Half the oil industry would shut down if they couldn't use grease in seawater.

    If you have a plain steel shaft running in a bush in seawater it should be greased, never a cutlass bearing.
     
  9. gonzo
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    gonzo Senior Member

  10. MikeJohns
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    MikeJohns Senior Member

    But neither of those links are relevant.

    Did you look up EAL's ? You can get marine grease that complies.

    The USA's EAL requirements have been around for quite a while now. There are even exemptions in vessel permits for the use of non-complaint lubricants if it's not feasible to use an EAL.

    It's not even sensible for a lot of the marine industry to avoid greased bearings in contact with seawater especially the oil and fishing industries.

    For a relatively small bush with a film of non-washout non-sheen grease then even in the USA the EPA will be happy. I'd like to see any specific regulation that says that is not the case since it's contrary to all the guidelines I have.

    There have been problems with small craft when people recharging grease filled ports from inside the boat while it's in the water, leaving floating gobs of grease. That's rightly prosecuted when detected but sensibly used grease is quite acceptable.
     
  11. gonzo
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    gonzo Senior Member

  12. MikeJohns
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    MikeJohns Senior Member

    Gonzo you do know that there are Non-Sheen Non- washout EPA approved marine greases don't you ?

    None of those docs you linked prohibit such grease in a rudder plain bearing.

    The use of EALs in below-the-waterline equipment was mandated for vessels calling in US waters by the US Environmental Protection Agency (EPA), in 2013. That includes greased bushes exposed to seawater such as lubrication of pump, rudder, stabilizer bearings etc. All the lubricants have to be documented on the vessel permit if they are in contact with seawater.


    Have you even looked this up ?
     
  13. gonzo
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    gonzo Senior Member

    You are proposing a complicated job that requires documentation and book-keeping. The most important engineering and building method is KISS
     

  14. MikeJohns
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    MikeJohns Senior Member

    Not at all !

    Once again: It's perfectly permissible to use grease in a plain rudder bearing. None of the waterproof non-washout greases in a relatively small rudder bush will cause any problem whatsoever. But there are even EPA approved greases for the application.

    Only a commercial vessel has a requirement to lists the lubricants on the general vessel permit. Leisure vessels don't have such a requirement. It's just the no sheen and no gobs of grease rule.
     
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