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Thread: spruce mast glue

  1. #1
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    Default spruce mast glue

    I need to make a 10' mast 2 3/4" diameter, tapered. Can I just glue up 2 pieces of straight grain 2X spruce from the lumber yard with epoxy?

  2. #2
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    Default Re: spruce mast glue

    Yes.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  3. #3
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    Default Re: spruce mast glue

    Or... 4 pieces of “1” inch !

  4. #4
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    Default Re: spruce mast glue

    I prefer G/flex epoxy. It has a perminant built in flex factor. Shellac the interior faces of the wood before final assembly. This will prevent moisture intrusion. It is cheap and drys very fast but be sure to mask off the faying surfaces that are to be glued as the shellac will prevent the glue from sticking. Remove tape and do the glue up.
    Jay

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    Default Re: spruce mast glue

    Or....Really enjoy yourself and do it birdsmouth.

  6. #6
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    Default Re: spruce mast glue

    Yes..
    If you can, run them through a planer or jointer of just hand plane the faying surfaces.

  7. #7
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    Default Re: spruce mast glue

    I'm in the G-Flex camp, it is tenacious and will flex with the mast. I have an old mast with failing glue joints and was told just to saw down the glue joints, clean off the old glue and then put it back together. I know normal epoxy likes a smooth mating surfaces but G-Flex is supposed to like a rough surface to adhere to and has gap filling properties. Is this correct?

  8. #8
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    Default Re: spruce mast glue

    Im rebuilding a hollow wooden mast at the moment, built by Collars of Oxford for a Yachting world dayboat. It appears that they used Casein glue & over the years this fails, I have done loads of these before, take the fittings off & stick a machete in one end, tap along with a mallet & the whole spar usually falls in half. As for glue I dont like epoxy for spars due to its poor uv resistance.
    I use Aerolite 306, it is time tested, UV resistant & works.

  9. #9
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    Default Re: spruce mast glue

    Quote Originally Posted by charles-caldwell View Post
    I need to make a 10' mast 2 3/4" diameter, tapered. Can I just glue up 2 pieces of straight grain 2X spruce from the lumber yard with epoxy?
    My masts are a few feet longer than yours by 3" diameter. I glued up sitka spruce 2 by 4s with epoxy. No problems in over a decade, apart from the beating they take from being struck and raised all the time.

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  10. #10
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    Default Re: spruce mast glue

    Speaking of taking a beating....Darroch, do you think if you had built birds mouth spars they would not have broken yet? Not from sailing , but from people sitting on them or getting torqued in storage etc. Birdsmouth spars can be fragile things .

  11. #11
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    Default Re: spruce mast glue

    I've wondered about their fragility but I've never handled one so I don't know. I've certainly stressed mine a few times without concern.
    I suppose the argument is less weight aloft but my mainmast only weighs 17 pounds at 13' 4" long - not sure what difference in performance a few pounds would make. A lot of people seem to think it's worthwhile.

  12. #12
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    Default Re: spruce mast glue

    Quote Originally Posted by charles-caldwell View Post
    I need to make a 10' mast 2 3/4" diameter, tapered. Can I just glue up 2 pieces of straight grain 2X spruce from the lumber yard with epoxy?
    Quote Originally Posted by Andrew2 View Post
    Or....Really enjoy yourself and do it birdsmouth.
    Birdsmouth will need to be slightly thicker to compensate for the hole up the middle, not a lot, but still thicker.
    As to keith66's comment.the glue will mostly be protected from UV by the wood. Aerolite is excellent if you can guarantee paper thin glue lines.
    It really is quite difficult to build an ugly wooden boat.

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  13. #13
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    Default Re: spruce mast glue

    I agree that G-flex, or T88 from System3, is a more ideal product for spars.

    In theory. And in most cases.

    For a stick that short and stout... the advantages of a less brittle epoxy don't really come into play much. So any basic marine epoxy would be suitable.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  14. #14
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    Default Re: spruce mast glue

    thank you one and all, think I'll try the G flex

  15. #15
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    Default Re: spruce mast glue

    Quote Originally Posted by keith66 View Post
    Im rebuilding a hollow wooden mast at the moment, built by Collars of Oxford for a Yachting world dayboat. It appears that they used Casein glue & over the years this fails, I have done loads of these before, take the fittings off & stick a machete in one end, tap along with a mallet & the whole spar usually falls in half. As for glue I dont like epoxy for spars due to its poor uv resistance.
    I use Aerolite 306, it is time tested, UV resistant & works.
    Keith
    We used to have our masts built by Collars in the 50 & 60s, two bits of spruce hollowed out, apart from the points where fittings etc.. Glued with 306, not Casein.

  16. #16
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    Default Re: spruce mast glue

    The mast on my little boat (a paradox) is just under 14ft, built as a tapered hollow box section from oregon and glued up with west system. Very light mast and whips around like a bastard in gusty conditions, but despite the lack of stiffness there have been no issues at all. I reckon a mast can be pretty lightly built and still be plenty strong enough. Having said that, for really tiny boats a simple solid (but still laminated) mast is likely to give a good result with minimal work. The mast on my big boat is solid, laminated from 4 layers of hoop pine (similar properties to Oregon) and is stupidly heavy, but appropriate for a 1934 designed gaff rigged cruising boat. There is something reassuring about a solid mast.

  17. #17
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    Default Re: spruce mast glue

    I have never had any issues with regular West system epoxy using the slow hardener. My spars just don't bend that much, or nowhere near as much as an epoxy glued recurve bow for example!

    Specificgravity .................................................. .................................................. ..1.18
    Hardness (Shore D) ASTM D-2240 .................................................. ........................ 83
    Compression yield ASTM D-695............................................... .................. 11,500 psi
    Tensile strength ASTM D638 .................................................. ......................7,300 psi
    Tensile elongation ASTM D-638 .................................................. ........................4.5%
    Tensile modulus ASTM D-638 .................................................. .............. 4.60E+05psi
    Flexural strength ASTM D-790 .................................................. ................ 11,800 psi
    Flexural modulus ASTM D-790 .................................................. .................4.50E+05
    Heat deflection temperature ASTM D-648............................................... ...........123F
    Onset of Tg by DSC .................................................. ..........................................126F
    Ultimate Tg .................................................. .................................................. .....139F

  18. #18
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    Default Re: spruce mast glue

    Quote Originally Posted by Canoeyawl View Post
    I have never had any issues with regular West system epoxy using the slow hardener. My spars just don't bend that much, or nowhere near as much as an epoxy glued recurve bow for example!

    Specificgravity .................................................. .................................................. ..1.18
    Hardness (Shore D) ASTM D-2240 .................................................. ........................ 83
    Compression yield ASTM D-695............................................... .................. 11,500 psi
    Tensile strength ASTM D638 .................................................. ......................7,300 psi
    Tensile elongation ASTM D-638 .................................................. ........................4.5%
    Tensile modulus ASTM D-638 .................................................. .............. 4.60E+05psi
    Flexural strength ASTM D-790 .................................................. ................ 11,800 psi
    Flexural modulus ASTM D-790 .................................................. .................4.50E+05
    Heat deflection temperature ASTM D-648............................................... ...........123F
    Onset of Tg by DSC .................................................. ..........................................126F
    Ultimate Tg .................................................. .................................................. .....139F
    There's nothing 'bad' about straight epoxy for spars. But G-flex is half a ninck 'better' in most circumstances.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  19. #19
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    Default Re: spruce mast glue

    I'm a huge fan of G-Flex as well as most of the other West products, however it's advantages may not apply to gluing wooden spars. Have any of you called the tech support line and asked if gluing spars is an appropriate use of G-flex? The number is: 866 937 8797

  20. #20
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    Default Re: spruce mast glue

    Quote Originally Posted by Russell Brown View Post
    I'm a huge fan of G-Flex as well as most of the other West products, however it's advantages may not apply to gluing wooden spars. Have any of you called the tech support line and asked if gluing spars is an appropriate use of G-flex? The number is: 866 937 8797
    Hi Russell - yes, I've discussed it with them. You know how cautious and measured they tend to be with anything not run-of-the-mill, but they allowed as how g-flex might be a good fit for that application. Particularly for birds-mouth construction where there is a lot of faying surface, and the rigidity factor is therefore multiplied. And even more so for unstayed masts.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  21. #21
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    Default Re: spruce mast glue

    I've just been doing something similar and blogged it here: http://scottishboating.blogspot.co.u...shop-porn.html
    Ewan G Kennedy

  22. #22
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    Default Re: spruce mast glue

    Quote Originally Posted by Andrew2 View Post
    Keith
    We used to have our masts built by Collars in the 50 & 60s, two bits of spruce hollowed out, apart from the points where fittings etc.. Glued with 306, not Casein.
    I stand corrected, I must say im surprised as i have reglued around ten collars spars, the glue line was distinctly white, I suppose 50 years is a pretty good lifespan for a spar!
    Im still inclined to use it though. Im not convinced that epoxy with tight joins will resist UV, from experience the uv breakdown goes inwards & once it starts it can only get worse.
    Dont get me wrong i like epoxy & use a lot of it, just it always gets painted!

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