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Thread: Gluing Mast with Boltrope Groove

  1. #1
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    Default Gluing Mast with Boltrope Groove

    I'm building a Dudley Dix "Argie 10", and rather than using the sleeved-sail aluminum mast shown in the drawings, I plan to use a wooden-spar Solent lug or gunter rig. I've bought a used sail that has boltropes on the luff and foot, and plan to glue up the upper mast and the boom from two halves with a boltrope groove between, similar to the spars shown for the YM "Senior":

    My dimensions would be a little different, I would use douglas fir instead of spruce, and my boltrope groove would be square instead of circular. (I don't have a router, so I would cut it with a dado set on a table saw. It will lose a little strength relative to the round groove, but since I will be using a boltrope rather than slugs there will be no concentrated stress.)

    My question is: How do I keep the groove free of glue squeeze-out?

    There is a UK website that demonstrates just this type of construction: http://www.boat-building.org/learn-s...oom-gaff-spar/ . On it the builder uses polyurethane glue. The squeeze-out foams up and can be easily scraped out with a custom tool. Since he is in the UK, I assume that the polyurethane he is using is Balcotan. I could use his method, but I've seen many bad reviews of polyurethane - for me, probably Gorilla Glue - on the forum. I'd hate to have my mast split apart while sailing.

    Is Gorilla Glue or some other polyurethane suitable for this application?

    If I don't use polyurethane, I would go with a yellow PVA glue, Titebond III. I figure I could run a string down the groove before gluing. Then after the spar was clamped but before the glue got hard I could pull a damp cloth pig through the groove until all the glue was gone. I would either wax or varnish the groove before gluing to make it easier to get the glue off. This might leave a little glue in the corners of the square, but there they wouldn't contact the boltrope. I figure that this kind of cleaning would be much easier to do with PVA than with epoxy.

    Does this sound like a plan that would work?

    Does anyone have other suggestions?
    I will beg you for advice, your reply will be concise, and I will listen very nicely and then go out and do exactly what I want! (Apologies to Lerner and Lowe.)

  2. #2
    Join Date
    May 2016
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    Niagara, ONT Canada
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    Default Re: Gluing Mast with Boltrope Groove

    So this idea occurred... Find some cheap candles that fit the groove, chop the tops off if they're not square, glob mast together with ample epoxy with excess squeezing out into the groove, and fill it with candles end to end... might need to tape them down over the top, now theoretically you get a circular section epoxy lined groove, and the candles should come out easily.
    2019: returning from being sidelined with medical probs, crossing fingers worst is over, still in "armchair enthusiast" mode for time being.

  3. #3
    Join Date
    Oct 2010
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    Default Re: Gluing Mast with Boltrope Groove

    Look up "cove cutting on a table saw". This may provide you with an alternate to a dado cut groove. You could try placing a piece of sacrificial cord in the groove when gluing and clamping then removing it from either end before the glue sets.

  4. #4
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    se pa (Bristol PA)
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    Default

    Don't know if they come in the size you need:

    Yonico 14471 4 Bit Ball End Grooving Router Bit Set 1/2-Inch Shank https://www.amazon.com/dp/B078HJPVZS..._yemuDbWSDNA5N.

    Boat rope sails are a PITA!
    Last edited by DeniseO30; 08-11-2019 at 10:38 PM.
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  5. #5
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    Default Re: Gluing Mast with Boltrope Groove

    No... foaming polyurethane glue is not suitable for spars. Not strong. Brittle - and fails with flexure. Precisely what one does not want for a spar.

    My go-to these days is G-flex epoxy (West System), or the equivalent.

    If you don't want to mess with epoxy - modified PVA's - like Titebond II and Titebond III

    Or resorcinol, which is a bit demanding to work with... or plastic resin glue which seems to dry out, granulate, and fail after 4 or 5 or 6 decades.

  6. #6
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    Default

    Uh...oh. "my boltrope groove would be square instead of circular. (I don't have a router, so I would cut it with a dado set on a table saw".
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  7. #7
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    Default Re: Gluing Mast with Boltrope Groove

    Quote Originally Posted by alkorn View Post
    Titebond III. I figure I could run a string down the groove before gluing. Then after the spar was clamped but before the glue got hard I could pull a damp cloth pig through the groove until all the glue was gone. I would either wax or varnish the groove before gluing to make it easier to get the glue off. This might leave a little glue in the corners of the square, but there they wouldn't contact the boltrope. I figure that this kind of cleaning would be much easier to do with PVA than with epoxy.

    Does this sound like a plan that would work?

    Does anyone have other suggestions?
    This should work OK.
    However, using your rag pull through should get rid of the epoxy as well before it starts to set up.
    It really is quite difficult to build an ugly wooden boat.

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  8. #8
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    Default Re: Gluing Mast with Boltrope Groove

    Quote Originally Posted by DeniseO30 View Post
    Uh...oh. "my boltrope groove would be square instead of circular. (I don't have a router, so I would cut it with a dado set on a table saw".
    look into MOLDING BLADES for your table saw

    a quick search came up w/ this

    https://www.amazon.com/CMT-235-006-0...gateway&sr=8-5

    though this one has fixed cutter tips there are some w/ removable/switchable cutters

    https://www.amazon.com/Corob-Molding...gateway&sr=8-1

    that can use different shaped knives

    https://www.amazon.com/s?k=Corob+Cut...ref=nb_sb_noss

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    steve

  9. #9
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    Hyannis, MA, USA
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    Default Re: Gluing Mast with Boltrope Groove

    If you can't find a machine tool for rounding, you can do it by hand in far less time than driving to a store and hunting for the thing. Dado out as you plan but perhaps a hair thicker on the wood. The two edges on each half that matter are then easily rounded down with some 80# sandpaper and a little Norwegian Steam.

    It should be possible to make really great faying surfaces, like so perfect that you could use Weldwood. But I'd use unthickened epoxy. Epoxy is very slippery so you want to clamp the ends to a bench or something so they don't reposition themselves while you do the major clamping. If you don't have a hundred clamps, put down as many as you have pretty close together (3" to 6") and duct tape in between, moving now unneeded clamps further along the spar as you go.

    With epoxy, the idea of the sacrificial cord in the slot, to be pulled out before the epoxy kicks so use the slowest setting goo you can find and work in the cool, is great.

    Most spar makers put any taper in on the sides and front leaving the aft face, where your luff grove is, dead straight. You'll need shims or careful height control on your spar bench to work with the luff groove up.

    G'luck

  10. #10
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    Default Re: Gluing Mast with Boltrope Groove

    My gp14 uses a similar system to what you describe. Being built in 1964, it still has it's wooden mast. When I brought her home, the mast easily split into two halves along the glue line. I cleaned everything up and used slightly thickened epoxy and a load of spring clamps to put it back together. To control the squeeze out, I did not use a lot of epoxy and then I ran more than a few small bits of rag soaked in vinegar along the bolt rope path to clean up the excess. Worked a charm and going on almost three years now.

    My Gp14 also uses internal halyards, I have not seen any marks on the ropes as obviously I could not control or clean up any glue there.

    However, if you contact Dudley, who is a really nice guy btw, he will probably recommend Resorcinol
    "If you think you are too small to make a difference, try sleeping with a mosquito"

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  11. #11
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    Default Re: Gluing Mast with Boltrope Groove

    Can you hire a router so that you can cut the correct groove for a boltrope?One of the cheap cutters from ebay will work adequately and you can take note of Art's comments about hollowing the mast since you can take a chunk of weight out of the least useful part of the mast with several passes of the same cutter.Then wrap a piece of sandpaper round a short piece of rubber hose to sand the ridges out.

  12. #12
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    Default Re: Gluing Mast with Boltrope Groove

    Somewhere have seen masts made with a split piece of 1/2" I.D. PVC plumbing pipe functioning as the boltrope slot, set into a square groove in a laminated wooden mast with epoxy filler filling the empty space and sticking it solidly in there. I don't remember where it was, but I think it may have been the mast for an iceboat.

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