What is the best way to construct a mast with multiple short parts?

Discussion in 'Multihulls' started by freeman1, Apr 25, 2012.

  1. freeman1
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    freeman1 Junior Member

    The mast is about 5m high. I am going to break it into 3-4 shorter ones for convenience of transporting. Should I use connectors with screwthread or just make several parts with different diameter and put one into another?
     
  2. mydauphin
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    mydauphin Senior Member

    Really not easy to do, that is why you see mostly one piece units. Mast as to be strong, flexible and light. Similar to a bow. At that size you can make it tilt.

    What size boat is this for?
     
  3. Petros
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    Petros Senior Member

    I would do it like a tent pole. Use short sleeve segments as couplings epoxied into the long segments. Must be a fairly snug fit, and 6 inch long coupling segments should be good enough (3 inches either side of the joint). And if you want to assemble it quickly you can also put a shock cord inside it to keep the parts together, also like a tent pole.

    I would not use screws or threaded ends, adds too much weight and you will likely get sand or corrosion in the threads.
     
  4. champ0815
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    champ0815 Senior Member

    I agree with Petros! Since the upper part of the mast will usually be fixed to the frame of the boat by the stays, you need no threads or screws to keep them together.
    As in your other thread I recommend you to review the solutions of the commercial manufacturers of inflatable cats for the mast - especially Grabner has a very instructive website where you can find assembly instructions as PDF and videos showing the construction of the inflatable catamaran in great detail.
     
    Last edited: Apr 25, 2012
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  5. PAR
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    PAR Yacht Designer/Builder

    Sectioned masts have been around for some time, including high performance dinghies. Naturally, finding tubing sections with a tight fit is the biggest issue, without a sizing bushing. A sizing bushing is the easy way out, but does introduce a hard point on the mast. A sleeve is worse in this regard, as bushing can be fairly soft, but not a sleeve.
     
  6. MAL1968
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    MAL1968 Junior Member

    I came across an article a few days ago where a guy showed plans for a mast that was constructed of ash I believe with 8 foot board length pieces that were rounded off And joined with a 12:1 scarf joint. The article was in Norwegian so I couldn't read it but it was very detailed pictorially. I believe that he sheathed it inside and out with carbon fiber, it seems like a workable mast to me.
     
  7. PAR
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    PAR Yacht Designer/Builder

    Ash would be one of the worst materials to employ in a mast, even with the additional waste of entombing it in carbon.

    Generally, you make every effort to build light spars. Ash is heavy, not very rot resistant and frankly the sign of a foolish builder, not someone to aspire too.

    The best wooden masts are birdsmouth construction and they don't need carbon skins to work. Birdsmouth methods are well covered on the web, but getting the scantlings right for your project will take some degree of expertise in this regard.

    What is the length of mast you desire? The sail area it will carry, type of rig, weight of the boat, etc. I can offer general dimensions that will get you in the ball park, without resorting to the wrong species or high tech fabrics that cost an arm and a leg.
     
  8. masalai
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    masalai masalai

    Oh dear, 5M (less that 16ft 6ins)? leave it as one piece... If you pull your boat behind a push-bike, surely you can manage the full length mast so the top of the mast passes just over your head whilst peddling?

    If you tow your boat behind a mini or some other small car - I am sure it will fit on a roof rack and tied to the middle of that?... Do not cut the mast... there are many other far more sensible suggestions... surely ????????????
     
  9. freeman1
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    freeman1 Junior Member

    A BIG thank to all you guys. I learned a lot of things from you.
     
  10. PAR
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    PAR Yacht Designer/Builder

    Two pieces is all you need. You might consider picking up a used one design mast, that has the problem solved for you.
     
  11. ancient kayaker
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    ancient kayaker aka Terry Haines

    I assume this is for the inflatable cat in your other thread so I understand the need for a mast in several sections.

    How is the sail to be attached to the mast? Getting lashings past joints can be a challenge, parrels are heavy for such a small rig and as for a track on a home-built sectional mast . . . perhaps the best approach would be to use an aluminum tubing and a sail with a pocket. That would be suitable for a beach-launched daysailer.

    Aluminum tubing is widely available in sizes that fit together, lengths of about 1.8m are standard in Canada, 3 lengths would suffice. I am not sure what diameters are available, my source only goes up to 5.4cm but that is only for radio masts. That might suit a mast with standing rigging but I don't think it would be strong enough for a free-standing mast.
     
  12. freeman1
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    freeman1 Junior Member

    Hi Par, it's hard for me find some used mast because yacht is not yet popular in my country.

    Hi kayaker, thanks for your advice, I do plan to use 6061-T6 Aluminum alloy tube for the mast. The size is 5cm of diameter and 5mm of thickness, 1.5m long each part because it's the maximum length if I want to put them in my car. The area of main sail is about 5 sqm. So I think a 4.5m high mast is enough, which composed of 3 sections.
     
  13. Submarine Tom

    Submarine Tom Previous Member

    Freeman1,

    I'm thinking three masts in one.

    Outside layer, aluminum tubing.

    Middle layer, smaller Al tube.

    Inner core, light soft wood.

    All, interference or friction fit.

    All staggered joints, no two alligning with the other.

    Drawing to follow...
     
  14. Submarine Tom

    Submarine Tom Previous Member

    Picture quality sucks but it's the best I can do at night.

    You get the idea?

    A one piece would be better by far. Just run it over the roof strapping it to the bumper at each end.
     

    Attached Files:


  15. freeman1
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    freeman1 Junior Member

    hi Tom, I get your idea, it's great, thank you very much. What's the best way to fix these parts? Is it ok to punch some holes on the end of the tube and put some screws in these holes?
     
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