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Thread: Mast repair -mixing wood species

  1. #1
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    Default Mast repair -mixing wood species

    Well it finally happened. My old 1931 main mast gave it up yesterday. Upon first inspection I found some rot just under the top pulley. Once that popped the wind pressure was just too much for the next panel. Still in the early thought stages as it's only been 24 hours. Yeah,getting the sails off and everything on deck was a bitch, but I had an incredible crew.
    Imediately I started thinking repair or build new. I'd prefer repair. However,is it advisable to repair Sitka mast with Douglas fir?...old growth v grain is available here.
    Most importantly, nobody got a scratch. May have been some soiled underwear.

  2. #2
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    Default Re: Mast repair -mixing wood species

    Sure. Especially that you are repairing a spot that gave up . This "pulley"...it the halyard sheave?
    Good fir is stronger and it sounds like not a lot needs fixin.
    By "panel", do you mean a panel of a sail or a bigger piece of the mast?

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    Default Re: Mast repair -mixing wood species

    Yes halyard sheave. mast panel.

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    Default Re: Mast repair -mixing wood species

    The second break was just above the lower shrouds mostly on a 5 foot splice. But I need a closer look.

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    Default Re: Mast repair -mixing wood species

    Seems CLC shipping out of Annapolis could UPS you a chunk of sitka if mixing it up makes you uncomfortable. https://www.clcboats.com/modules/cat...e=sitka-spruce
    2019: returning from being sidelined with medical probs, crossing fingers worst is over, still in "armchair enthusiast" mode for time being.

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    Default Re: Mast repair -mixing wood species

    Glad to hear there were no injuries! Sitka Spruce has a vertical strength in combination with its lightness that makes it desirable if lightness is a prime prerequisite.
    Is this mast a box section, hollow eclipse or is it solid? or a hollowed out of two halves stick? How tall is it
    Jay

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    Default Re: Mast repair -mixing wood species

    It's a hollow round ,two halves stick. I'm not really uncomfortable mixing woods. Weight is not an issue. The previous mast was oversized and twice the weight....and completely rotten. This mast was awesome for a few years. The total height is about 55'.
    Last edited by mariner2k; 07-15-2019 at 06:19 PM.

  8. #8
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    Default Re: Mast repair -mixing wood species

    In truth, yoou might want to build a good temporary spar bench in order to keep the scarfs aligned . Only the areas where the scarfs will be made need to be set up with cross spalls as seen below. But, the whole mast needs to be straight and well supported as you will be rotating it to fair the new sections. In order to have a solid core to clamp to, consider making a hollow plug to support each scarf from within but will allow for drainage. I am a stickler on shellacking the inner sides of spars in order to discourage rot from taking hold. A core box plane, if you can find or make one will take the curse out of hollowing the halves. https://www.woodmagazine.com/woodwor.../the-stanley-5. I am using West System G/flex epoxy for spar making now as it moves with wood that needs to bend or flex. And, it holds until Charon ends up sculling through an ice flow!
    Jay

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    Default Re: Mast repair -mixing wood species

    When mixing wood I would worry most about differences in stiffness and swelling. If one piece is a lot stiffer than the rest, it could cause a stress concentration where they join. Using a long scarf should help, and the difference between Sitka and DF isn't huge. Swelling differences also cause stress, but here the difference is very small, so not a problem.

    https://www.fpl.fs.fed.us/documnts/f...chapter_05.pdf
    Wood Database; Eric got his strength numbers from another source, so I wouldn't say that they are inaccurate, just different data. No two trees are exactly the same.
    https://www.wood-database.com/douglas-fir/
    https://www.wood-database.com/sitka-spruce/
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  10. #10
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    Default Re: Mast repair -mixing wood species

    I've mixed woods on spar repairs in the past without any ill effects.

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    Default Re: Mast repair -mixing wood species

    Thanks. I do plan on building a bench. I really just want to do this once. As the weather cools I will probably build a little quonset style workshop. For some reason the link wouldn't come through for me. The original scarfs are about 5' . I plan on sticking with that length.

    Someone in an older thread had a similar problem. I ultimately think my cause and his cause of the rot were similar. I had reglued, and refinished this mast in my yard. I had it covered in tyvek all of the time until the last month. It was wet and humid
    There is a reasonable chance I encountered a fungus then.
    Any opinions on a clothespin splice for the top?

  12. #12
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    Default Re: Mast repair -mixing wood species

    One more question....at least
    Is epoxy the best glue for the job?

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    Default Re: Mast repair -mixing wood species

    We use West System G/flex for all of the spar work we do. This is an adhesive that has a slight flex factor built into it that does not become brittle with the passage of time. As a result, the expansion and contraction of different wood grains is not a factor of concern.
    In fact the mast seen below is the main mast of our H28 "Bright Star". The new section that was spliced on is Sitka Spruce while the rest of the mast is Douglas fir.
    I am specutalting that perhaps the rot in your spar may have been caused by inadequate drainage. Hollow masts do suffer from condensation on there interiors with changes in humidity and heat, even over night. As mentioned before, I do believe that several coats of shellac, on the interior of a mast prior to glue up , helps to prevent rot from getting a toe hold. Of course, faying surfaces are protected by masking during shellac application.
    Jay

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    Default Re: Mast repair -mixing wood species

    Quote Originally Posted by Jay Greer View Post
    In truth, you might want to build a good temporary spar bench in order to keep the scarfs aligned . Only the areas where the scarfs will be made need to be set up with cross spalls as seen below. But, the whole mast needs to be straight and well supported as you will be rotating it to fair the new sections. In order to have a solid core to clamp to, consider making a hollow plug to support each scarf from within but will allow for drainage. I am a stickler on shellacking the inner sides of spars in order to discourage rot from taking hold. A core box plane, if you can find or make one will take the curse out of hollowing the halves. https://www.woodmagazine.com/woodwor.../the-stanley-5. I am using West System G/flex epoxy for spar making now as it moves with wood that needs to bend or flex. And, it holds until Charon ends up sculling through an ice flow!
    Jay
    Your link is missing a few characters.
    https://www.woodmagazine.com/woodwor...core-box-plane
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

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    Default Re: Mast repair -mixing wood species

    Thanks for the correction Dave! The address worked for me. I didn't know it would not transfer correctly.
    Any way, a core box plane really helps when cutting a half round hollow in a mast blank. I have had mine for over fifty years and it has done a lot of good work for me in that time. A thin guide made of door skin ply can be tacked on to guide the plane and protect the glue seam if necessary when working with spruce. A clean up of the small groves left by the plane can be skimmed off with a round bottom wood bodied plane once the core box plane has hogged out the bulk of the meat. Some core box planes were made with wooden bodies which would be a simple thing to do for the mast builder if he can't find one on eBay. I just checked on eBay and saw several for sale for much much more than I paid for mine at a garage sale. Scarry prices but the tool will do that job of hollowing out a half circle very well!
    Jay
    Last edited by Jay Greer; 07-16-2019 at 02:31 PM.

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    Default Re: Mast repair -mixing wood species

    I believe in my case the rot started from an end a grain just below the sheave. The rest of the mast looked fine. Once those upper shrouds were off, Game over until the next supported section.

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    Default Re: Mast repair -mixing wood species

    Do you add anything to the G flex epoxy? From my recollection the stuff is pretty thick.

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    Default Re: Mast repair -mixing wood species

    G/flex is available in two consistancy's. I like the thick one as it spreads easily with a wooden spatula or putty knife and stays put.
    Jay

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    Default Re: Mast repair -mixing wood species

    Quote Originally Posted by Jay Greer View Post
    G/flex is available in two consistancy's. I like the thick one as it spreads easily with a wooden spatula or putty knife and stays put.
    Jay
    Do you precoat the part with unthickened epoxy first, or just spread G/flex on the bare wood?

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    Default Re: Mast repair -mixing wood species

    Any good books on scarfing?

  21. #21
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    Default Re: Mast repair -mixing wood species

    As to the OP - while it's not absolutely perfect to mix species... in this instance it's not a big deal.

    Agree that, for spars, G-flex, or comparable, is the better choice.
    David G
    Harbor Woodworks
    https://www.facebook.com/HarborWoodworks/

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    Default Re: Mast repair -mixing wood species

    I am of the belief that applying G/flex to bare wood allows it to sink in to the grain and form a better bond. I have. been using it since it was first introduced and have never had a problem with it.
    Jay

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    Default Re: Mast repair -mixing wood species

    Quote Originally Posted by mariner2k View Post
    Any good books on scarfing?
    There are a lot of videos on Utube that should help you. For spar splicing, it is wise to work at 12:1. I sometimes will chalk one side and check the fit by massaging one against the other. Then plane off or scrape the high marks. Carbon paper works as well but can darken the seam where it contacts. Air blast removes chalk dust.
    Jay

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    Default Re: Mast repair -mixing wood species

    Thanks, I'm sure when the time comes I will have another question or 2

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