Galion 22 conversion

  • 02 Nov 2017 09:48
    Reply # 5499266 on 5070195

    Arne,

    Two problems:

    The temper of tapered tubes is only T5, as T6 is too hard to spin-taper.

    No mating size of tube is readily available.

  • 02 Nov 2017 09:33
    Reply # 5499102 on 5070195
    Anonymous member (Administrator)

    Jami,

    Do you know what alloy (temper) is used in those aluminium tubes?

    One factor I use to check when fitting a new mast on my boats, is its weight related to the weight of the boat. I try to keep the mast down on 3%, or better 2.5% of the boat.

    Now I have guesstimated the maximum stability of your boat to be about 715kpm (+/- 10%?). I would aim for a mast with a yield strength (bending moment) of about twice that. I could be willing to go a little below this and see what happens. The lovely thing with a freestanding tube mast is that one can easily see if it is struggling during sailing. This is visible long before any damage is done. If I felt uncomfortable with it, I would insert a 3-metre length of tube up the lower end of the mast. The highest stress in such an un-tapered mast is no doubt at deck level.

    Arne


    Last modified: 14 Jul 2018 09:18 | Anonymous member (Administrator)
  • 02 Nov 2017 08:54
    Reply # 5498727 on 5070195

    Ok, thanks. Sounds like an experiment that I don't want to make at sea.

    Unless I manage to find 165-170/3 tube, I will go with 140/5 then.

    For me it would be a lot easier to use a grp flagpole at the top 4 meters than making it from wood. I wonder if this will make the upper part of the mast too flexible?

  • 02 Nov 2017 08:24
    Reply # 5498455 on 5070195

    I never like to mix materials that have different mechanical properties in this way, to carry the same kind of load at the same time. They might, or might not, reinforce each other. It's different in the case of, for instance, steel reinforced concrete, or glass reinforced plastic, where one material carries tension, the other carries compression. Here, you're asking both materials to carry tension on one side, compression on the other, as the mast flexes. But I don't have a definitive answer on this, either on theoretical grounds or from practical experience. It might work, I don't know, and the only way to find out is to try it. It would be necessary to use a timber with compressive strength equal to tensile strength, which means not the lighter softwoods. 

  • 02 Nov 2017 07:23
    Reply # 5497666 on 5070195

    How come it always happens that it's just what you need that is not available? There is not 3mm or 4mm tube available in more than 150mm diameter.

    A few steps back: did you advice me to totally forget the tapered al-flagpole option (145/2.5-2.8 mm with 2.8 meters of parallel) even with a wooden inner mast at the parallel part? The wall just isnt thick enough?

  • 01 Nov 2017 19:48
    Reply # 5490906 on 5070195

    Because you're aiming to go with a high AR rig, I believe you'll need the strongest, and more importantly, the stiffest of those options. That's the 140 x 5. My 165 x 3 mast is a little stronger and stiffer and a lot lighter, because of the thinner wall and greater diameter, and that's what I'd prefer you to have, but if it's not available in Finland, then 140 x 5 is a reasonable choice.

  • 01 Nov 2017 06:19
    Reply # 5481708 on 5070195

    Due to almost nonexistent availability of tapered al-poles in Finland, I have to go with a straight tube and the top made of something else.

    The options seem to be 130x5 and 140x5, no 140x4 (David’s suggestion) available. I suppose the 130 is not strong enough?

    Edit: 150x3 is also available.

    Last modified: 01 Nov 2017 06:35 | Anonymous member
  • 14 Sep 2017 14:16
    Reply # 5232157 on 5227569
    David Tyler wrote:

    Yes, depending on the spec of the GRP. But if this is possible, then  it is also possible to use that portion of the aluminium flagpole that has a diameter of 140 at its bottom end, and make a joining sleeve or spigot.That would be better, but rather wasteful.

    ¨...and too expensive, considering the waste. I can get my hands on cheap grp flagpoles. If I remember right, one of the members has done this to a 20" Havsfidra.
  • 14 Sep 2017 13:30
    Reply # 5227569 on 5070195

    Yes, depending on the spec of the GRP. But if this is possible, then  it is also possible to use that portion of the aluminium flagpole that has a diameter of 140 at its bottom end, and make a joining sleeve or spigot.That would be better, but rather wasteful.

  • 14 Sep 2017 10:35
    Reply # 5213400 on 5210436
    David Tyler wrote:

    I've just done some figuring, and 140/4 is coming out OK, as the lower tube on its own, so long as it is T6 temper. Could you accept this, with a wooden topmast?

    I would, gladly - but estimating from the first sketches I need a 9,5-10 m mast to keep the AR high enough, which in turn would mean 4 meters of wood (the al-tubes here are sold as 6000 mm). I'm not sure if this is achievable by myself.

    How about a 4m grp flagpole plus this 140/4 tube?

    Last modified: 14 Sep 2017 12:55 | Anonymous member
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