Optimal aluminum mast splice location

Discussion in 'Boat Design' started by abosely, Aug 8, 2023.

  1. abosely
    Joined: Mar 2015
    Posts: 190
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    Location: Big Island Hawaii

    abosely Senior Member

    Looks like will be using aluminum 6” sch 10 in 6061 T6 for masts, 6.625 diameter & .134 wall, 37’ high.

    Longest length material is available is 20’,
    so not a lot of choices when using one splice.

    I don’t know if it will make any difference where the joint is located for this rig or not,
    when have 20’ max lengths to work with.

    But thought I would ask just to be sure. :)
    Cheers. Allen

    Last edited: Aug 8, 2023
  2. abosely
    Joined: Mar 2015
    Posts: 190
    Likes: 2, Points: 18, Legacy Rep: 10
    Location: Big Island Hawaii

    abosely Senior Member

    I was looking through old posts about splicing aluminum masts and noticed that when a mast breaks from wind loads (vs running into a bridge) they tend to break at place where something is attached like spreader or where gaff saddle was riding.

    Makes sense, stress would generally tend to be greater in places like this, not that these are the places masts break.

    Initially my thought it would be best to have only one joint not two.

    But reading this made me wonder about making the splice a few inches above where the gaff sits and then would have heavier wall thickness in the section a few feet above and below where the gaff rides.

    A second potential benefit wold be that the lower splice could be placed higher or lower because length from mast base to where gaff sits will be shorter, so would give more options of where to put the lower (main) splice.

    I don’t know, maybe it won’t matter strength wise where splice is located on these simple masts (no spreaders or rigging attachments to mast other than at the top of mast.

    Unless this isn’t a good idea, will use section of 6” sch 40 with 6.625 OD, 6.065 ID, .280 wall and turn the OD down to be good fit inside the 6” sch 10, 6.357 ID with enough room for adhesive.

    That would give a nice uniform fit between the two parts allow nice even thickness of adhesive between them.

    When turning the sleeves down, would taper the inside edges on both ends of sleeve, so isn’t a step, would prevent any water that might get in sitting on sleeves lip and be smooth surface if need to feed wires later.
    Would tapering few inches inside of the sleeves be adequate to prevent stress concentration?

    Cheers, Allen
    Last edited: Aug 8, 2023
  3. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    The obvious solution is to contact the designer. What do they say ?
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