Mast collar size

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  • 21 May 2018 10:43
    Reply # 6246233 on 6097536

    For those who are math averse, I found an app on line that will calculate the material dimensions of a cone for you. It'a called Cone Calc.

  • 14 May 2018 22:21
    Reply # 6173759 on 6172190
    The new owners removed it hoping that the Spartite compound they used would make the joint watertight. It didn't.
    Unless you use Spartite with the intention of never removing the mast, it's bound to leak, for the simple and sufficient reason that you put releasing agent on one of the surfaces.  If air can get down it, sooner or later water will, in my experience.
  • 14 May 2018 21:18
    Reply # 6172190 on 6097536

    I made a simple mast collar for Marco Polo/Teleport.

    I had an awning maker make me a cone that was snug at top and bottom. At the top, I had him fold the edge of the fabric inward to form a sleeve that was about 2.5cm wide. It was stitched. We left a gap of about 1.25cm. Same at the bottom made large enough to fit over the flange at deck. I slipped a long SS hose clamp into the sleeve until it emerged at the gap from the other side. It was fitted into the tightening nut assembly and the screw was tightened at the gap. The sleeve was a little wider and the hose clamp. I a[[pied white silicone sealant at the top of the collar be holding the looseish sleeve out ward with my finger nail. I applied the silicon into the V gap that I made. When the cloth sprung back, it compressed the silicone a bit. Then let it set. It never leaked. The new owners removed it hoping that the Spartite compound they used would make the joint watertight. It didn't. All in all, a very simple design. Very long hose clamps were not hard to find.

  • 11 May 2018 14:09
    Reply # 6148920 on 6097536
    Deleted user

    I  think, if a close fit collar system - or, say, a close fit collar with a nylon/Delrin bushing the way to fit it would be to lower the mast to just about the deck, slip the upper collar up the mast, fit the mast through the hole in the deck (which will be larger or as large as "normal" clearances), attach the lower collar and bolt the two together until almost tight.

    At that point, the mast would nigh perfectly perpendicular to the deck, no rattling around, not at risk of bending.

    Then keep lowering until it lines up with the lower collar, and once bedded, tightening it all up.

    The yard I know will actually only mast a boat in the water, I'm guessing it's easier to wiggle a boat in the water about a bit than fine align a crane on dry land?

    As far as water sealing, of course you'd need something extra, may be just duct tape, but the idea is the same theory that holds copper pipes joints together in domestic plumbing, eg the "olives" in plumbing compression joints.

  • 09 May 2018 10:43
    Reply # 6144960 on 6097536
    Anonymous member (Administrator)


    on my present boat I went back to the straightforward PJR practice with wedges around the mast at the partners. Since there was no need for room for altering the mast rake (that is done initially at the mast step), the clearance between collar and mast could be set to just 20mm. I’ve found that if the wedges are made with very little rise (1-2mm over its length), they will never climb back upwards in use. I also make them from cheap spruce, which will be a bit compressed in use. After another tapping down of the wedges, after a few sails, one can just about forget them. One or two wedges may feel looser than the others, but I don’t worry about that. For extra peace of mind, one can pass a round or two of duct tape around them, just below deck level.
    This setup makes stepping and un-stepping the mast very quick and easy.


       ..step forward for more...

  • 09 May 2018 07:34
    Reply # 6144845 on 6097536
    Deleted user

    The honest answer is, I don't know.

    The trick with close tolerance metalwork is to leave it all loose during assembly, and tighten it all up even once all the parts are set in place, so it tightens into place exactly. I suspect doing so would give you every bit as much wiggle room as a standard mast.

    To remove, do the reverse.

    If I was trying it, and it's making me think as it's a lot cheaper than the equivalent "marine" stuff what I'd do is test it/align it with a 6' or 2m length of mast tubing and put a radius on the mouth to help guide the full mast in.

    If your mast is tapered, you might earn a little more clearances 2m from the base.

    You can also buy mast collar tubes (link) to fit with stepped masts that might size up right.

    Like so ... the companies that make them also make rings to match.

    Remember, the brief was to make something out of nothing for nothing.

  • 09 May 2018 06:03
    Reply # 6144781 on 6144733
    Jami Jokinen wrote:

    Very interesting, thanks.

    My problem here is the need to install the mast every spring and uninstall in the autumn. Usually the mast crane has to be used with the boat in the water. I’m afraid that sliding the mast to a very tight-fit hole (especially a long one = your two collars idea) is if not impossible, at least very difficult with  a risk of bending the mast. 

    I quite agree Jami: alas so many great ideas don't stand up to reality.  Even with the boat firmly supported ashore, the placing of the mast into the partners is never that straightforward; cranes simply aren't precision instruments.  And a tight fit still isn't a waterproof fit! 

    David Tyler's 'Spartite' alternative seems a good way to go, if your gaps aren't too big.

    And the truth of the matter is that if you are in a remote location, on a tight budget, with limited resources, the issue of an overlarge partner can be adequately remedied with wedges.  On Fantail I had parallel partners and mast.  I 'foxed' the wedges, ie put them in from the top and then another row from the bottom.  While the boat is stationary, the top layer can be driven in hard enough for the operation.  I put just a little foaming polyurethane glue on the bottom ones as I drove them in.  This was effective in stopping the paired wedges from working either up or down. but they could be removed without too many headaches.  If you wreck them in the process, it's not the end of the world.

    To be honest, I deliberately went for quite a gap between partners and mast because I wasn't at all confident that the mast would go into the step and end up at the intended angle.  Having a bit of room to play with meant that I could adjust the angle quite significantly.  In fact, as so often happens with these things, it all worked out satisfactorily and the mast ended up in the correct position and at the correct angle.  But a loose fit at the partners might make you a bit less nervous about the position of your mast step.

    The mast was waterproofed with a rubber gaiter, well sealed with duct tape.  Then an elegant fabric cover was fitted over the top, protecting both rubber and tape from the sun.  The whole thing was easy to examine, remove or replace and low budget.  It never leaked, either, something that I was seriously motivated to prevent, with the hole being over my pillow!

    Last modified: 09 May 2018 06:17 | Anonymous member
  • 09 May 2018 05:02
    Reply # 6144733 on 6097536

    Very interesting, thanks.

    My problem here is the need to install the mast every spring and uninstall in the autumn. Usually the mast crane has to be used with the boat in the water. I’m afraid that sliding the mast to a very tight-fit hole (especially a long one = your two collars idea) is if not impossible, at least very difficult with  a risk of bending the mast. 

    Last modified: 09 May 2018 05:03 | Anonymous member
  • 08 May 2018 20:46
    Reply # 6143955 on 6097536
    Deleted user
    Jami Jokinen wrote:

    Holy cow! The inner diameter is 131mm, and the lower part of my mast will be 130mm. I suppose this is unusable, because:

    Back on topic, I was thinking about the collar suggestion, and refer back to the compression ring idea ... and how they could be used as deck collars as well.

    Two face to face sandwiching the fibreglass as a collar, then one as a step.

    These are actually slip fit "Welding Necks" used in gas, oil, industrial fluid industries.

     (Interestingly, most come with finished surfaces and face-to-face gaskets to size, as they were designed to bolt large pipes together. Pipe sizes that pretty well match round mast sizes).

    You say there is only 1mm clearance? I'm actually thinking that is a good thing, about what you would want (if it is 1mm total, it is .5mm on each side). What I dont know is how thick the protrusion is but it looks plenty thick enough to machine.

    So - all approximates for the sake of discussion - work with the idea of machining a broad ringed but shallow band on the inside of it, say, 3mm deep (as in 6mm total) and 26mm high, it could be possible to make a 3.5mm thick shim, a bushing actually, out of a strip of metal by wrapping it around your mast until it follows the curve. You want to leave a compression gap between the ends.

    Actual dimension are open to discussion, say 25mm high.

    The compression ring/bushing will fit that into the ringed groove.

    The sides of the protrusion look thick enough to drill and tap a useful thread into them at an equal distances, if not welded some stainless steel nuts on around the side, and install grub screws into them. I'd go for a short and fat as you can fit.

    Now, install the bushing into the groove, drop the mast into it, tighten the bushing up as a compression ring equally all round, using some Loctite on the screws and, lastly, once it is all set, run a ring of silicon gunk around the gap at the top. You may find it seals perfectly as it is.

    With a close tolerance above, you should get near perfect alignment on the keel at the step.

    You could even use two such necks as a deck collar, one above (pointing up) and one below the cabin roof (pointing down) clamped together and sealed, using two such bushings/shims systems, say, 4" apart. 

     The advantage of that is you have twice the amount of surface area to spread the forces across, and they would align up perfectly, so you end up with the same effect as having a single longer pipe with a collar welded around it.

    This is similar the set up they use on motorcycle front forks. At the end of the stanchions, inside the fork legs, there are bushings/shims managing huge and persistent forces (imagine 1,000lbs of motorcycle and riders, travelling at 150mph, dealing with 1,000s of bumps a minute). They last for 10,000s of miles of such punishment.

    Now go back to the old fashioned way of banging in chocks of wood. How does it compare? How much actual contact area does it have to spread its load across? The only advantage wood might have is absorbing is shocks, the disadvantage being it deforms when it does - fixed by being tapped in further - (before eventually falls apart and need replaced).

    To do the wood chocks really nicely, I'd say you'd probably need someone with a big wood lathe - so there's not that much difference in manufacture and this way you might end up without having to have a big gaiter on it.

    Possible problem ... fitting any curvation on the cabin top. Would work best where the front hatch has to be used/replaced with a perfectly flat surface. Someone else would have to comment on the fibreglass's strength. You'd probably want a broad layer of ply to spread any loads.

    Absolute overkill from an engineering point of view, but just offered as brainstorming though ... if they are cheap, they may be worth playing with.

    Your mast would fit absolutely straight, top and bottom, so leave the final bolt and glue up until last. But the flanges are actually design to feed a pipe (mast) into them.

    Is that clear? Critique away at will ...

  • 07 May 2018 22:41
    Reply # 6142234 on 6140243
    Deleted user
    Graeme Kenyon wrote:

    Hi Anonymous Member – nobody is trying to "insult" or "spread prejudice against" anybody (your words ...)

    I'm sorry but I'd say calling an entire stranger "discourteous", as a first 'off topic' response to a first post from a new member, coming from a well established member, is just that.

    Strange welcome committee you guys have.

    And so can I ask, as with David's response above, is that the hazing over now ... or is it just starting? Am I expected to run the gauntlet of forum regulars as well, on top of paying my £7?

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