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Thread: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

  1. #1
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    Default Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Due to damage in last season to the luff groove from point loading stess. I'm tentatively planning to replace the luff groove for the boltrope with a bronze track and sliders. I have posted photos and diagrams here:

    https://lolfolkboat.wordpress.com/20.../rigging-year/

    The diagram of my proposed repair is at the bottom of the blog post.

    Questions:


    1. What size screws?
    2. What type of wood to glue in? Should I use spruce or a harder wood? I don't want it to split, with the addition of about 100 screws, spaced 3 inches apart.
    3. What type of epoxy? Flexible? I have lately seen advertised some epoxies that are supposed to be more flexible. This mast is designed to flex in heavy wind. I don't want to inadvertently over-stiffen it.
    4. Do I epoxy in the screws. The whole business about adding epoxy to holes in wood, per the West System Bros, has me a little skeptical.
    5. Main concern is that I donít want to split the mast along its glue-line. That's why I don't want to simply attach the track to the mast itself, because the screws would go directly into the glue-line. But I thought that if I added epoxy into the holes, after drilling them to a larger size, then it might actually end up stronger. In which case, I could just plane off the luff groove and dispense with adding another piece of wood into the slot.
    6. Second concern is to maintain flexibility in mast and need an epoxy that compliments that flexibility
    7. Should I use this as an opportunity to embed antenna and mast head light wires in to the mast? And if so, what kind of wire do I use for the masthead
    8. And unbelievably, I'm still questioning whether I shouldn't just stay with the luff groove in the mast!

    I'm a beginner with spars and rigging, and I don't think I have covered the whole thing very well, and so I am looking for guidance and experienced replies.

    Thank you in advance,
    Josh

  2. #2
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Another question: does anyone know of someone experienced with these masts in the SF area, Portland, or Chicago? Or perhaps someone who would be willing to consult me regardless of location?

  3. #3
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    I feel your pain. I’ve had the same problem when switching from luff tape on a larger sail on a composite spar.
    For a sail of that size (~160 SF), metal track is the only choice. Stainless might be easier to find.
    As for fasteners, spacing will likely be dictated by the track. I’m guessing #8’s @4” or #10’s @6”. Double up at headboard.
    As an alternative to inlaying a strip of a harder wood, I’d pot the screws as described in the Gougeon book, chapter 14. It won’t stiffen the spar and won’t introduce splitting forces. Call West System tech support.

  4. #4
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    The router will make a good shape for the insert. You might consider leaving the insert a little proud to lift the track up a bit. Many put a wood strip under the track. It makes painting or varnishing easier in years to come. On the other hand, on Meg's new masts I'm not putting in a spacer.

    For this sort of joint, it's very easy to make a very good fit, tight enough that it takes a little effort to push in. So you'll have a thin glue line and the flexing of the mast won't hurt that. If you thicken the epoxy much to make up for a sloppy fit, then you will want a flexy epoxy. If you're inserting shortish lengths, you can easily make sure that the pieces bottom out in the slot without leaving an air bubble.

    Screw size will be what fits in all those holes. An inch and a half should be long enough. You want bedding under the track and on the tip of the screw so's to prevent water intrusion.

    Sitka spruce would be best but it's a little piece so doug fir will do. It's not structural and you don't even need to make scarf joint on the individual pieces.

    G'luck

  5. #5
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Thank you for your replies, Jim and Ian. I already bought (used) bronze track from NandJmarine.com. These great guys have a sailboat bone-yard in upper Wisconsin, and they have the stuff. I spent the afternoon there recently. I think I will attach a photo. No wooden hulls, and only a couple of wood spars, but lots of other stuff.

    The track I bought looks like extruded bronze, not the rolled kind, and it's 7/8" wide. It's a pretty springy piece of metal, almost 29 feet long. I do have a photo of that, at least the end profile. I got the sliders there too. By the way, they definitely have another sizeable length of bronze mast track, maybe 30 feet, presently attached to an aluminum spar. This is the lighter, rolled track, and it might be 5/8". (If anyone's interested)

    Note: I added the two images to the original blog page at the bottom.

  6. #6
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Another one of my issues is how to best guide the router. Power tools and me get along well, but sometimes they like to go off in their own direction. My favorite cuts are when I have some sort of fence to keep me out of trouble.

    Ian I thought of leaving the insert proud of the mast a bit. I'm glad you suggested it.

  7. #7
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Josh, In addition to general boat construction, I specialize in mast work . In my own shop I had and am setting up a new forty foot spar bench which, allows a mast such as yours to be laid flat and stabilised enough to use the bench to be a solid guide base for the router. The mast should face with the groove up and be free of side ubstructions and blocked so that the groove is at a constant height. a router jig will need to be made that will slide touching the bench on both sides of the mast to keep a constant depth of cut. While the router base plate is the primary depth of cut guide, the jig contact with the bench will keep it square to the cut. The jig needs to be about ten inches in length and have a two point mast contact set of shoes made of large dowels so as to allow centering of the router during the cut just as a spar taper scribe will. If this is not clear, I can elaborate for you further. I would choose the West System Epoxy G/flex for securing the track spline. As Jim Conclin mentions, at the head board every hole needs to have a screw. For added strength on a high stress spar, I often set up a bronze cleating strap with a screw on both ends. This cleat crosses the center line of the track and is riveted to the track for better holding at the head board area. Lower down every other hole is ok for fastening.
    Jay

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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    How much afterwards stress is there on the luff groove? Can you just mend the bad spot? Is mast bend a means of trimming the main on Folkboats?
    All that being said, pictures and a blow by blow of the operation on Jay's new bench would be fascinating.
    Good luck

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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Jay and David, thank you for your comments.

    Jay, I think I get the basic idea of the stabilized mast bench. I am doing this work behind my in-laws garage. So I am thinking that I will have to use some other method than building a permanant mast bench there. My method will more likely involve a number of saw horses. I can manage to create a level height fairly well by clamping secondary cross-beams to the tops of the saw horses.

    I believe you are suggesting that the mast surface to be routed must also be an equal distance from the "bench." I suppose by "bench" will be two or three 2x10s laid end to end and fastened to the saw-horse cross beams. I think I can use a laser level to get things level. Here's an illustration of what I have so far:

    https://lolfolkboat.files.wordpress....amps.png?w=768

    I think I have some idea about the router jig itself, but it would help if you clarify. Thank you.

  10. #10
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Quote Originally Posted by David W Pratt View Post
    How much afterwards stress is there on the luff groove? Can you just mend the bad spot? Is mast bend a means of trimming the main on Folkboats?
    All that being said, pictures and a blow by blow of the operation on Jay's new bench would be fascinating.
    Good luck
    David, I don't know the answers to your questions about stress on the luff groove.

    I might be able to mend the bad spot, but then I'm back to a system that's problematic to begin with, the way I see it. I could even remove the cars off the sails and just use the luff groove with a bolt-rope, but I understand that they are prone to sticking, requires an extra pair of hands to feed the mainsail on hoisting, and then it can be difficult to douse the main in an emergency. Since I sail often short-handed, I don't want to have any extra fuss with the sail.

    All that being said, the dynamics of the mast and sail will change with the new bronze track, I feel sure. It's fairly heavy. So there will be increased weight aloft, and this mast is solid to begin with. This will increase the heeling forces, but I'm not well-versed in sailing dynamics.

    Frankly, the complexity of changing things on the sailboat makes me worry that I will do some lasting damage. I really don't know what I don't know.

  11. #11
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    I'm no expert, but you might be overthinking it a bit. I used to have a Tumlaren with a timber mast and an aluminium track screwed to it. It was fine. I think a metal track is best if you are using slides rather than a bolt rope, due to the localised stresses. Use something to keep water out of the screw holes, bedding compound or epoxy a la gougeon. Gird your loins and get on with it I reckon.

  12. #12
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Phil, you're right that I'm overthinking things. I usually do, but it's the way I roll and I'm stuck with it.

    I'm still hoping to hear from Jay about the router jig:

    ...router jig will need to be made that will slide touching the bench on both sides of the mast to keep a constant depth of cut. While the router base plate is the primary depth of cut guide, the jig contact with the bench will keep it square to the cut. The jig needs to be about ten inches in length and have a two point mast contact set of shoes made of large dowels so as to allow centering of the router during the cut just as a spar taper scribe will

  13. #13
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Wait, I think I get it. I need to make a tool like a taper scribe, which had the axis of the router bit as its center. That will guide the router down the center of the mast! Thank you for this help. I think I can do this. (I will need an old spar to practice on.)

  14. #14
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Okay, here’s my interpretation of the jig, that Jay suggested to use for cutting the new slot into the mast:

    https://lolfolkboat.files.wordpress....2-13-26-am.png

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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    That is a very good interpretation of what I am suggesting for the router jig. I would add two vertical guides to keep it level by resting on the bench. I would also make several light cuts rather than attempting to cut the slot in one pass. Looks like you have it well in mind! The job is not as difficult as one might imagine. A flat bench is the key.
    Jay

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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Quote Originally Posted by joshs View Post
    Okay, here’s my interpretation of the jig, that Jay suggested to use for cutting the new slot into the mast:

    https://lolfolkboat.files.wordpress....2-13-26-am.png
    That's the ticket. If you're familiar with a 'spar gauge'... it's just a router version of that.

    And a flat bench would definitely simplify... but isn't absolutely critical. What's most important is blocking the stick up so it doesn't roll, and so the top edge is very close to parallel to the top of your bench. Or... to be more precise... equidistant. For example -- if the best bench you can manage has a slight droop in the middle... just make sure your spar droops too. Very strongly second the notion of taking it out in multiple passes. It won't be a wide bit, and spruce is not a dense wood... but you'll still get better accuracy, with less chance of grabbing/veering with smaller bites.
    Last edited by David G; 05-20-2017 at 02:22 PM.
    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)

  17. #17
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    Here is another kind of gauge that I created for laying out the faceting lines on an elliptical mast. The bench I am using was sixty feet in length. Note the 2x4 clamping spalls. This bench was supported by 4x4 posts set into a dirt floor. My new bench will be on the second floor of my shop and will be wall supported with angled outer posts that rake back to the wall plate. This will give unobstructed foot room when making a long pass with a spar plane, skill saw or router.
    Jay
    Last edited by Jay Greer; 05-20-2017 at 12:23 PM.

  18. #18
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    David: yes, I imagine that if the spar rolls while you're cutting, you're in deep trouble.
    Last edited by joshs; 05-20-2017 at 08:29 PM.

  19. #19
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    Default Re: Sitka Mast luff groove replacement with sailtrack on Folkboat questions:

    My prototype test project is a success. I used the plate from my router table, attached some 1-1/4 inch dowels to it. These worked pretty well on some round, wooden wallpaper rollers I have in the woodshed. I went from a narrow cut to a wider one pretty successfully. I used a 2x10 for my bench.

    In actual practice, I will use (2) 16-foot lengths of 2x10 and at least 6 saw horses, plus a considerable number of height adjusters for the mast itself.

    Here are some photos: https://lolfolkboat.wordpress.com/?a...e_preview=true

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