Splice Aluminum Mast, keel stepped

Discussion in 'Boatbuilding' started by Asa Hammond, Jun 4, 2023.

  1. Asa Hammond
    Joined: Feb 2023
    Posts: 21
    Likes: 5, Points: 3
    Location: California

    Asa Hammond Junior Member

    I have a 12 meter (42 foot ) dutch steel ketch I am working on (details elsewhere on the site). I have a mast to replace the original sitka spruce mast which was deck stepped (and was setup to pivot / fold down for going through canals I suppose), and I want to replace this with a keel stepped mast for the improvement in strength.
    The mast is a nice setup but had an issue where it was cut down from its full length and then I received it. The two pieces are 280 cm (9.18 foot) and 1458 cm(47.83 foot) long respectively. I am going to splice them together with an insert, either rivetted, screwed, epoxied or welded. The interior height from keel to deck where it will be stepped is 214 cm (7.0 foot). Previous mast height was 1425 cm(46.75 foot) from the deck. Sparcraft masts recommends a 1 - 1.2m splice in the middle of their masts that are roughly this section (14cm x 23.5 cm x 4.3mm wall) Sparcraft S-622 Mast https://www.rigrite.com/Spars/Sparcraft_Spars/S_Masts/S-622_mast.php, so I am thinking I don't need quite that length of splice if the splice is right around deck level. I could remove 80 - 100 cm from the mast and use that as the splice insert, or I could run around and source and bend some aluminum to use for the splice insert. My question is basically anyones thoughts around if I should have the splice biased above or below deck level, and what length of splice should I run in this scenario. Pointers to load equations would be great.
    This is a steel boat, deck is 3mm corten. I am looking to have roughly the same or slightly higher mast height than I am replacing. I have to replace the standing rigging no matter what.

    Intended use of boat is offshore tradewind cruising.

    Much appreciated!
     
  2. Rumars
    Joined: Mar 2013
    Posts: 1,825
    Likes: 1,137, Points: 113, Legacy Rep: 39
    Location: Germany

    Rumars Senior Member

    Whoever cut your mast whitout asking you where you wished it to be cut should pay for a new extrusion.
    You can't really use a much shorter insert then recommended since you need to cut fingers in the end to avoid a hard spot.
    If the extrusion is of sufficient dimension I would go deck stepped. If not, source or fabricate a suitable insert and have the splice shortly above deck.
     
  3. kapnD
    Joined: Jan 2003
    Posts: 1,318
    Likes: 418, Points: 83, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    I would avoid splicing, it adds layers of complication and invites hidden corrosion issues.
    Why not keep the mast step on deck, and weld in a steel support below from the deck to to the keel? Then your one piece mast would be only a couple feet shorter, surely not a huge issue for a heavy cruising boat?
     
    bajansailor likes this.
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