cracked welding at spreader connections

Discussion in 'Sailboats' started by urisvan, Nov 21, 2022.

  1. urisvan
    Joined: Nov 2005
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    Location: istanbul

    urisvan Senior Member

    Hi,
    in the boat that i am the captain, there are parts that connect spreaders to the mast(as normal:)) as you can see at the "pic1".
    these aluminium parts are welded to the aluminiım mast.

    as the owner said to me that some years ago they noticed some paint on one of these welding falled off and after they applied dye penetrant they found some cracks at one of those welding. and they made the same dye test to two more welding areas. i have sent the picture of these test (pic 2,3,4)

    He also i want to be sure about the strenght of the mast. So what would you recommend?

    -I think, the welding is not regular so dye test doesnt seem to give good answers.
    -i am thinking to go up the mast, first clean these areas and then check the welding with magnifier, if i see some suspicious areas i can make a dye test.
    -if the welding is not smooth, first grind it well untill it is smooth and then make dye test.
    -slack the shrouds and make the weldings again at the bad areas after i grind them well

    Regards
    Ulash
     

    Attached Files:

  2. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Hi Ulash,
    Can you advise please how tall this mast is?
    And how old it is - and how old is the rigging if the rigging has been renewed at some stage?

    This sounds like a recipe for disaster, if you are really planning on re-welding these joints while sitting in a bosun's chair up the mast.
    It would be much safer and no doubt easier in the long run if you simply lower the mast with a crane.
     
  3. rangebowdrie
    Joined: Nov 2009
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    rangebowdrie Senior Member

    It was hard for me to make out clearly, but were those brackets not originally designed to be secured to the mast with either rivets or machine screws?
     
  4. urisvan
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    urisvan Senior Member

    it is 4 spreader mast, i am not sure but i guess around 25 metres maybe some more. it is a 40 years old boat and the mast as well. the owner says the rigging changed 12 years ago.
     
  5. urisvan
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    urisvan Senior Member

    hi rangebowdrie,

    it would be better that way but unfortunately not.
     
  6. urisvan
    Joined: Nov 2005
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    urisvan Senior Member

    Hi Bajansailor.

    I think inspecting can be done while the mast is up. But if many of the joints needs rewelding then it will be better to take the mast down maybe.

    So the first question is
    How can i make a proper inspection?

    Regards
    Ulash
     
  7. AJB
    Joined: Jul 2021
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    Location: 31 42S 152 04 E

    AJB Junior Member

    It is moderately miraculous that the thing remains erect. The structural integrity of the tube is likely to have been compromised by what are essentially fatigue cracks.
     
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  8. wet feet
    Joined: Nov 2004
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    Location: East Anglia,England

    wet feet Senior Member

    I have to admit to being a little surprised to see the brackets welded to the mast.I would have expected the extrusion to be heat treated and the welding won't have done anything good for the process,unless it was done prior to the treatment.Which leads to the point that welding at this stage will have a similar effect.It will also warm up the inside of the extrusion and perhaps remove any protective coating that was in there.I bought a very slim camera that can attach to my phone a while ago and would recommend that something similar is fed into the mast to take a look at the inside,it might be better to find out now.Which leads on from the point raised in post #7.
     
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  9. urisvan
    Joined: Nov 2005
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    urisvan Senior Member

    AJB,

    Do you mean that, if these fatigue cracks appears at these joints, we should be suspicious about the mast itself?

    I am not sure but i think extrusion can flex and dont get hurted while the welding can not and after poundimg on the heavy seas it can crack...

    then should we check the mast and try to find clues like small cracks on the mast?

    Regards
    Ulash
     
  10. AJB
    Joined: Jul 2021
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    Location: 31 42S 152 04 E

    AJB Junior Member

    Three issues:
    1. The properties of the alloy are reduced in the way of the weld... a bit like 'tear on the dotted line', so the weld functions like a hole in the mast wall.
    2. Under normal aeroelastic loadings, the spreaders deflect the mast wall, primarily by the vertical movement of the tips when attached semi rigidly at the base. Ideally, spreaders should have some freedom of alignment at the inboard end, for durable ocean use.
    3. Stress concentrations inevitably arise.

    Etc...
     
  11. urisvan
    Joined: Nov 2005
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    urisvan Senior Member

    Yes,
    I have got you. shock loads and fatigue of the spreaders will be transfered to the mast by the brackets and i agree that there is too much stress concentration at that little area, unless the mast is not supported from inside it can be likely that there can be minor cracks at the inner side of the mast wall under the brackets...

    so maybe after checking the mast from inside by small camera(if we can), maybe we should consider of changing the bracket system completely (without changing the spreaders).

    so what would be the ideal connection without changing the spreaders? Think that we lower the mast, grind out all the brackets and make another safer system from the beginning. It will be hinged again but what would be the shape of the bracket and how will be connected to the mast?

    Regards
    Ulash
     
  12. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    The ideal would be what it was probably like originally, ie with spreader brackets riveted onto the mast in similar fashion to almost every other aluminium mast that you see.
     
  13. AJB
    Joined: Jul 2021
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    Location: 31 42S 152 04 E

    AJB Junior Member

    Lets call the new attachment fittings 'gudgeons'.... because that is more or less what they should be. If they are located (each pair) equidistant from the fore & aft CL of the spar tube they can be identical and of similar material to your existing, possibly 5083 alloy. The spreader attachment pins should be horizontal, allowing spreader tip vertical movement without exerting any bending stress on the gudgeon or the mast wall from this source. Mechanically fasten gudgeon into mast wall, possibly using an epoxy paste bed as well. For cruising/long ocean, through bolts prefered over rivets...

    You will need to modify the inboard spreader ends, retaing the existing spreader geometry. One possible method would be to use off the shelf ss onion studs, in 12mm 316 good for a few tonnes and readily available. The 12 mm accepts that pin size and has a 12 mm threaded end that you could plug tap into your spreader tube.
     
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  14. AJB
    Joined: Jul 2021
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    Location: 31 42S 152 04 E

    AJB Junior Member

    Also, just tidy up the existing welds after removing the bases. Alignment of the new gudgeon bases in the way of the welds should help the overall structure somewhat.
     

  15. urisvan
    Joined: Nov 2005
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    urisvan Senior Member

    Hi AJB,

    I appreciate your effort but something that you have written sounds nice but seems like undoable if not impossible to me like "plug tapping the stud in the spreader tube". through the mast bolt fasttening is also difficult at the curved ends i guess, if i was at the middle part where the mast is more or less flat it is easier of course like shroud attachments.

    and i think to make the pins horizantal is not necessary, there will be some space for articulation even if the pin is vertical. and more at the exixsting problem the crack is at the fore side of the bracket welding. which means the fore and aft motion caused it. If it was caused by up and down motion of the spreader the crack would be at the up or down side.

    For my opinion more traditional way of connection is safer. a plate riveted to the mast. I will try to add a drawing.

    regards
    Ulash
     
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