Advice on dropping a rudder as the seal is rusted out

Discussion in 'Metal Boat Building' started by Banksy, Dec 9, 2021.

  1. Banksy
    Joined: Dec 2021
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    Location: Sydney Australia

    Banksy Junior Member

    I'm new to steel hulls and have a 41' vessel sitting on the hard standing so think it a good opportunity to drop the rudder to make some repairs around the hull section where the rudder shaft drops down through the hull. The round seal looks to suffer a lot of deep rust internally. The previous owner had the vessel huled out doe to leakage around this area. There's a temporory patch been welded into place but I feel I might cut the whole lot out to better assess the damage and then refit a new hull plate around the rudder shaft hole and weld in a new flange where the shaft goes throug hthe hull.

    Note: When I drop the rudder down it will hit the concrete hard standing so won't come completely out. I'm thinking I might drop it & then cut a square section out of the hull (10cm around the hole) & then lift the hull upwards and over the rudder stock..
    Is this feasible ?
     

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  2. Banksy
    Joined: Dec 2021
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    Location: Sydney Australia

    Banksy Junior Member

    In the followng pics you can see the clearance height from base to ground. It's approx. 1.5- 2 ft. If I wanted to remove the rudder completely I'd have to have the vessel lifted... yes ??
     

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  3. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Is there a bolted on shoe at the base of the skeg that you can remove to allow the rudder to drop?

    Re your hard standing, is this in a boatyard? If so, would it be feasible to move the boat to another area of the yard where it might be possible to dig a hole (if necessary) under the rudder to drop it?
    In your first post the clearance above the ground appears to be maybe 6" - 8" (?)

    But if you do actually have 18" - 24" clearance under the rudder (re the first photo in the second post), then you might find that the length of the stock in the rudder tube is less, thus allowing you to drop the rudder fully?
    Is it relatively easy to remove the shoe(if fitted) and test this out?
     
  4. Banksy
    Joined: Dec 2021
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    Location: Sydney Australia

    Banksy Junior Member

    Hi Bajansailor - yes the rudder is held in place with a skeg shoe with several bolts located unI might have to heat the bolts first as they look to be seized.
    I have pic of the shoe here somewhere
     
  5. Banksy
    Joined: Dec 2021
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    Location: Sydney Australia

    Banksy Junior Member

    Here a closer internal shot of the rudder post & the rudder shoe
     

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  6. wet feet
    Joined: Nov 2004
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    wet feet Senior Member

    My guess would be that you are going to have to get the boat lifted.If you were on hard standing,it might be feasible to dig a rudder pit-given permission to do so, on a good concrete pad I would doubt that permission would be forthcoming.It would be smart to remove all obstacles to the rudder coming out before even talking to the crane operator about a precise time for the job.With the amount of rust evident it may be a fight to get all the hardware free.I would think that a good soaking with penetrating oil should be under way before the spanners come out and a lot of pictures and sketches will be invaluable during the rebuild process.
     
  7. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    I agree with wet feet re getting everything ready in advance before going for the Big Lift.
    See if you can get everything undone, and the rudder dropped a bit.
    You might even find that you then don't need to lift the boat, or at least not by very much.

    Re the photo of the very rusty bottom bearing, it might be worthwhile rebuilding this assembly in S/S instead, with a new bearing?
     
  8. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    There is no need to completely remove the rudder to do the repair. Dropping it to the ground should be enough for welding. The corrosion may not be too bad. It appears to be mostly cosmetic and not a significant loss of section. Remember that scale rust is about 10 fold the loss of section.
     
  9. wet feet
    Joined: Nov 2004
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    wet feet Senior Member

    Looking at the images I can't immediately see which part is believed to be the source of the leak. The nearest approximation to a seal that is on show looks a lot like a stuffing box, is it possible that re-packing might fix the leak problem? On the other hand,there is an amount of corrosion of the whole rudder and it's attendant fittings and It would probably be a good long term plan to drop it and investigate all the nooks and crannies. Perhaps welding up any wasted areas and then removing those nice,new anodes before having it hot dip galvanised up to a point a little below the gland. It might also be worth adding a tapped hole to the top of the stock as it can be a good way to hold the rudder in place while working on it, if it doesn't already have one. When tied up to a pontoon, it isn't feasible to go outside with a bottle jack to hold the rudder up.
     

  10. Banksy
    Joined: Dec 2021
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    Location: Sydney Australia

    Banksy Junior Member

    I did not know that Gonzo. I've been scraping back what looks like flat shells of rust on other areas of the hull & was under the impression there's probably only 1mm left of actual steel as some sections that broke away looks to be 3-4mm thick but I guess the rust expands some becoming thicker.
    I guess a good method would be to hit any corroded area with a welding scaling hammer & if it breaks right through it's time to cut out that area completely.
     
    bajansailor likes this.
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