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New masts

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  • 29 Sep 2022 08:39
    Quote
    Reply # 12936151 on 12935878
    Anonymous member

    Meanwhile, has anyone thought to go to Siberian Larch? In 1999 


    It's very splintery and I'm not sure that wood from Russia is going to be readily available these days!
  • 29 Sep 2022 01:12
    Quote
    Reply # 12935897 on 12932409
    Anonymous member

    I build steel masts all the time in New Zealand (about twenty to date) they are robust, reasonably light, have a small cross section and give good service. 

    If you give me the sail area and LAP I can calculate the wall thickness, diameter and taper for you.
  • 29 Sep 2022 00:56
    Quote
    Reply # 12935878 on 12935287
    Anonymous member
    In Dutch the large cracks are called "windscheur"and are considered quite normal in a massive mast but:

    the dept should not exceed 30% of the diameter of the mast, two cracks almost opposite should be added up by each other ( see picture)
    the width of the crack should not exceed 5% of the diameter of the mast
    the length of the crack should not exceed 20% of the mast length.

    I suspect I'm going to simply reproduce the solid Douglas Fir masts I have. 

    Thanks for that reply on allowable cracks in solid masts.

    Meanwhile, has anyone thought to go to Siberian Larch? In 1999 I worked as a volunteer shipwright on the wood/epoxy tall ship, Tenacious, for the Jubilee Sailing Trust. They used a huge amount of Siberian Larch. It was used in the hull and laminated ribs.
  • 28 Sep 2022 17:57
    Quote
    Reply # 12935287 on 12932409
    Deleted user

    Hi Jim,

    This is a message from someone on the WoodenBoat Forum clearly quoting the same Dutch site I found:

    Numerous Dutch traditional charter sailing ship's are equipped with massive wooden masts. After a serious accident, which killed one of the customers, the guidelines for maintenance were tightened.
    In Dutch the large cracks are called "windscheur"and are considered quite normal in a massive mast but:
    the dept should not exceed 30% of the diameter of the mast, two cracks almost opposite should be added up by each other ( see picture)
    the width of the crack should not exceed 5% of the diameter of the mast
    the length of the crack should not exceed 20% of the mast length.

    Mine fail on the depth of checks before I'd looked over both masts completely. I'll continue to look for the original and post it when I find it.

    I suspect I'm going to simply reproduce the solid Douglas Fir masts I have. Unfortunately the timber is not so expensive, around 600 euros for both masts, but the delivery from the first reply is 2200 euros. I'm looking for other suppliers closer to the boatyard and talking to steel and aluminium pole suppliers as well, though so far they are wary of getting involved since they don't have the experience to calculate loads.
  • 28 Sep 2022 02:32
    Quote
    Reply # 12934496 on 12932409
    Anonymous member
    The only recommendations I could find on assessing solid masts for checks is on a Dutch Maritime Authority site that suggests maximum depth, width and length relative to the mast's length and diameter. 


    Could you give us a link to that site?
  • 27 Sep 2022 13:22
    Quote
    Reply # 12933615 on 12932409
    Anonymous member

    Hi Dermot

    There are many options when it comes to making masts. Perhaps the easiest is to use an aluminium tube with a wooden topmast section - there are a couple of threads on this forum about this. It does depend on the availability of suitable aluminium tubing though.

    A wood mast can be glued up from smaller lengths in  a number of ways. It can be solid, or nearly solid - have a look at the method Dan Johnson used on his, here;

    http://junkdorybuild.blogspot.com/2011/10/hestur.html

    (you have to click through a few pages to get to the mast pics!)

    Our first junk rigged boat had some serious looking shakes in the mast - they didn't seem to have any effect on the mast strength. I think the theory is that the shakes a the result of uneven drying - it's the bound water that has gone, all of the cellulose fibres and lignin are still there, so the wood should be pretty much as strong as it ever was. Are you sure they need replacing?
  • 26 Sep 2022 15:25
    Quote
    Message # 12932409
    Deleted user

    Having put our Alan Pape Ebbtide up for sale and got some people interested in seeing her I have now discovered that the masts are really firewood. They are solid Douglas Fir and though I was well aware of the checks that spiraled up them they gave no cause for alarm. 

    The only recommendations I could find on assessing solid masts for checks is on a Dutch Maritime Authority site that suggests maximum depth, width and length relative to the mast's length and diameter. Both mine fail with ease. So I am looking to fit new masts here in France. 

    I've checked out the possible steel and aluminium pole suppliers listed on this site and written to a couple of companies. One has refused on the basis that they know nothing about the sort of loads put on a boat mast. Another is asking about wall thickness and I wouldn't know where to start on that.

    The best solution would probably to simply replicate what I had before and be certain it would work as well and last as long.

    If anyone has any further advice or experiences I'd be happy to hear them.

    I should say I have the skills, but not the facilities to make my own hollow timber masts.

    Thanks.
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