Wood for Birdsmouth mast

  • 14 Jun 2019 08:24
    Reply # 7579153 on 7571097

     Staved timber mast

    Hi Michael

    I have built 24 staved timber mast out straight Oregon planks 50 mm thick

    The mast has been in use for 10 years. Each mast took me 3 month to build.

    In JRA Magazine 66 page 10 I have shown, how it could be done

  • 13 Jun 2019 14:28
    Reply # 7577372 on 7571097
    Anonymous member (Administrator)

    Frankly, Michael,
    I think it will cost you a lot more in work to build a mast from staves. Besides, the grown mast should be shaped (at least to 8-sided) and then cut in half and dug out, while the trunk is still raw. This speeds up the drying process to a few months and prevents plitting.

    Unless you already have the new junksail, the maststep and partners ready, then sailing with a JR this summer is out of the question.

    If you plan and do your homework properly, you will be ready for take-off in May, next year.

    Good luck!

    Arne


    Last modified: 13 Jun 2019 20:31 | Anonymous member (Administrator)
  • 13 Jun 2019 11:38
    Reply # 7577068 on 7571097

    Thanks for all the replies, most grateful. My hopes for a very cheap mast seem to have been dashed. 

    Annie I did not know that about my local junkies so maybe I will contact them.

    I believe using a grown mast would involve many months waiting for 

    it to dry out and then shaping it. The birdsmouth method would give me a mast very quickly.

    If I had sufficient funds I would call ALC to find out what they would

    charge for a 10m tapered column delivered to Ardoran Marine, Leargs by 

    Oban but am afraid to ask.

    About the PT wood. Before I raised the question I did do a search on the web and the 

    consensus seem to be that as long as the wood was given sufficient time to dry

    it would be ok for gluing. The treatment adds moisture to the wood and it is this 

    which causes the problem with gluing.

    I also had a crazy thought that I could fill the core of the hollow mast with

    closed cell foam to give it more structural integrity.

    Anyway I will go away and think some more.


    Michael

  • 13 Jun 2019 09:19
    Reply # 7576995 on 7571097
    Hey, Michael, are you a lucky man?  You live within coo-ee of Pol Bergius, who has his own sawmill and Dan Johnson, who makes wooden masts.  And they both own junks.  I suspect if the three of you get together, you could come up with a plan.
  • 13 Jun 2019 09:13
    Reply # 7576994 on 7571097
    Anonymous member (Administrator)

    There is an exception to the clear grain timber rule: There may well be some knots in masts, either solid or dug out, made directly from a trunk of wood. These knots stand at right angle to the surface and do no harm.

    Besides, if boats only could be built from clear, knot-free timber, then there would not have been any boatbuilding in my country, which there certainly has been, and still is.

    What I admire most with local wooden-boat builders (apart from their skills with their axe), is their ability to ‘read’ the wood and make sure the knots are placed so they do no harm (no knots at the plank’s edge, for instance).

    That said, I agree that the originally shown ‘fence planks’ didn’t look good for masts, with the knots all over the planks and in awkward positions.

    Arne


  • 12 Jun 2019 21:37
    Reply # 7575797 on 7571097

    As the others have said you certainly want clear grain good quality timber for a mast, and really for any other boat construction. It does not necessarily need to be an exotic timber. My recently sold junk rig yacht 'Footprints' had a timber mast, (staved), constructed from straight grain Pine which is our standard plantation grown building timber here in New Zealand. At 21 years that mast is still in excellent condition.

    It is often surprising what you can find in a local area. I had this dilemma when looking for framing timber for the catamaran I am building. All the exotic framing suitable timbers were very expensive and not available locally. In the end I found a local timber mill who specialise in a timber we call Macrocarpa, but which is actually Montery Cypress. I was able to purchase all my framing timber for a very reasonable price as straight grain clears. The only downside was that they were shorter lengths so for stringers I have had to scarf together to get longer lengths. But you can become proficient at scarfing pretty quickly.

    Last modified: 12 Jun 2019 21:49 | Anonymous member
  • 12 Jun 2019 15:49
    Reply # 7574315 on 7571097

    I've only tried to epoxy pressure treated wood once, and it did not hold well.  I really wouldn't do it on a mast.

    To echo David, though, the problem with the wood you have indicated is that the quality is way below what you want.  Knots in the wood, depending on location and orientation can reduce the piece's strength to almost zero.  Clear straight grain is the way to go.  

    That said, I have had some luck with the general big-box stores like Lowes or Home Depot.  You buy carefully selected large width and length 2x8, 2x10, or 2x12s, and rip the outer sides off, which can give you straight grain quarter sawn Douglas fir. If you flip them end for end, you can mitigate out some of the imperfections. You throw away the middle piece, which is nearly always flat cut.

    But I wouldn't do that for a mast, though, either.  Dimensional lumber like that is usually kiln dried and has all sorts of internal stresses that make themselves known six months after assembly in the form of twists and bends.

    You want to make friends with your local sawmill.  Explain what you're looking for, and how you want to use it.  They are usually helpful and knowledgeable.  Sometimes they are real scoundrels, too, so do your homework.

  • 11 Jun 2019 00:22
    Reply # 7571281 on 7571097

    Thanks for the reply David. The reliability of the gluing is what I was most worried about. I was wondering if anybody on here had any experience with epoxy on this type of wood.


    Michael

    Last modified: 11 Jun 2019 09:01 | Anonymous member (Administrator)
  • 11 Jun 2019 00:04
    Reply # 7571242 on 7571097

    Hi Michael,

    I would not recommend this wood for mast construction. What you need is clear straight grained wood, preferably not treated as the treatment effects the gluing reliability. The wood shown in their photographs has numerous knots and would not be strong enough for mast building.

    I would suggest trying to find a small independent sawmill that will select the timber and saw it to your specifications. When I lived in England I was lucky as there was a local sawmill of this type near my home in Bewdley, Worcestershire. I also lived in the middle of the Wyre Forest and could select trees and buy them directly from the Forestry Commission. I got enough Norway Spruce to build the solid wood masts for a friend's 55 foot ferro cement ketch on one occasion.

    All the best in your search.

    David.

  • 10 Jun 2019 22:11
    Message # 7571097

    I have found a local supplier selling 4 by 2 inch in 4.8 m lengths for £7.50 which seemed quite cheap to me. The wood is pressure treated and used for fencing. Would this be alright to use for a 10 m  mast.

    The supplier is http://www.hodgefencing.co.uk/shop/railsframing.php

    P.S This is my first post


    michael

    Last modified: 11 Jun 2019 09:02 | Anonymous member (Administrator)
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