Latest News: Forums Technical Mast Set-up Woes

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  • #4665

    Hi Folks

    My son and I have spent many frustrating hours in the sunshine trying to get our mast set up right, in the end we have acheived a rig that measures correctly but can’t accept the pivot pin in the mast until we put a chock in front of the mast. (The chock takes ALL the prebend out and is thus not necessarily desirable to leave in except when we want to bung a pin in to drop the mast or the wind is pretty strong).

    We followed the guide in the back of the latest wayfarer book to the letter and all went well until the step with checking the pin. We found our pin was being pushed forwards in the tabernacle against the aft aspect of the pin-hole in the mast and the remedy proposed – moving the mast step pin forwards – simply didn’t work: we ran out of space to move it any further forward, and this was even after taking it way further forward than ever before. We wondered if the wording in the guide was wrong or misleading so we tried moving the mast step pin back. But that didn’t work either.

    Exhausting and totally frustrating.

    I can assure forumites that the spreaders were set correctly, the mast was the same mast, shrounds the same shrounds, genoa wire/reefing spar the same, and the mast stepping back where its always been using the same screw holes. Yet we can only achieve the correct rake and prebend by leaving the pin out.

    Anyone else had this trouble or can cast any light on it.

    Fortunately a fortnight in Brittany with the boat should make all our trouble worthwhile and its very unlikely we”ll have to shoot a bridge!!

    all best

    Boris and Angus: Delphy W6330.

    #11882
    Dave Barker
    Keymaster

    I agree that the wording in the Wayfarer Book isn’t necessarily perfect – it seems to me to be a great aide memoire for anyone who has successfully set up their boat several times previously, but not easy to follow as an instruction set (for me anyway).

    Forgive the lengthy reply, I will get to the point, but you can safely skip this paragraph, which only provides background information – in fact, just go to the last two paragraphs if you’re getting bored already. When we bought our current boat I quickly realised that there were several components that would take so long to fix up that it was more sensible to replace them altogether, including the tabernacle. Despite my best efforts to record various measurements, the pin holes didn’t seem to be in the right place in the replacement wooden tabernacle, and I had to improvise a jig to control a Forstner bit so as to enlarge and slightly relocate the holes with the new tabernacle in situ. Eventually I was more or less happy with the result, but although (or perhaps because) the pivot pin was free to move with rig tension and correct rake etc., the lower aft edge of the alloy mast foot plug tended to catch on the for’ard edge of the mast step when raising the mast, which necessitated a tricky slight lifting movement of the mast. The alloy tenon(?) also tended to get worn and mashed up passing over the edges of the countersunk holes in the surface of the mast step, increasing friction and making the mast foot reluctant to sit back as far as it should do (at least without using chocks at deck level and a forward shove above head-height on the aft side of the mast to ‘pop’ the mast into place).

    I arrived at a solution to several of this problems, involving a fair bit of work, but transforming my experience of mast raising and lowering. First, to prevent the rear corner of the mast-foot tenon from catching on the edge of the mast step I relocated the mast step (the parallel-sided track with holes either side) a little further forward. Unfortunately the fixing holes in the bottom of the step fitting are staggered, so I had to drill and countersink new ones – the step would have been too far forward if I had moved it to where the holes lined up again with the existing screw holes in the timber block beneath (it would have been effectively two holes further on). The mast when being raised now meets the surface of the step a little way back from its front edge, smoothly and progressively making contact with the horizontal surface. Next, to prevent the holes in the step from acting like a cheese grater on the mast-foot tenon I cut a piece of thin (2mm?) aluminium strip, perhaps 20mm x 90mm, to fit flat between the cheeks of the mast step. It’s held in place by one countersunk screw slightly aft of the mast, plus a very thin spread of silicone beneath it. This raises the mast by c. 2mm but fortunately seems to make little difference to the fit of the pivot pin – check first. It does give a smooth surface for the mast-foot tenon to slide over though. Finally I temporarily removed the mast-foot plug (carefully taping the halyards in their respective positions exiting the mast), filed the tenon smooth, then cleaned it up and filled the central void (plus any nicks) with epoxy thickened to peanut butter consistency. This probably doubles the bearing surface area, and gives a nice smooth, gently curved surface to run over the new aluminium shim. The mast now goes up and down as easily as anyone could wish, and more relevantly in answer to the original question, the mast also assumes the correct position back against the little restraining pin much more easily than ever before.

    As you have I think realised, the mast foot in your case, Boris and Angus, is too far forward, so if anything the restraining pin behind the mast needs to come back, but there’s no point in moving the pin further back if the mast won’t come back to meet it. You can “encourage” it backwards each time you rig the boat as described above by placing a chock between mast and deck, reaching up as high as you can comfortably manage and giving a strong forward shove, but if there’s a lot of friction below the mast it will be reluctant to co-operate. (Be careful not to dent the front of your mast at deck level – pad it with a cloth first if you’re concerned about this.) Sometimes this misalignment will suddenly and spontaneously correct itself when sailing downwind in a blow, especially with chocks in place – and scare you for a second until you realise what the sudden bang was! If you have room for a thin shim below the mast-foot tenon it will make life that little bit simpler, allowing the foot to slide more freely, but do check the pivot pin height first.

    Summary – Provided the pivot hole in the mast and in the tabernacle are at the same height you will be able to achieve the desired result. Focus on the idea that you’re fixing the position of the mast-head in 3-d space. There is a single point up there where the tip of the mast will be just where you intend; giving the correct rake and on the centre line of the boat. Crucially, the foot of the mast could be in any one of a number of positions and still satisfy that single spatial requirement up aloft, BUT only one of these positions also leaves the pivot pin free to move, and your task is to find that one position*. Then and only then you will know which is the correct hole for the mast step pin, with or without packers. (To be strictly accurate, you’re seeking the single position for the apex of the shroud/forestay “triangle” that permits the pivot pin hole to be aligned with the tabernacle hole when the mast head is in the correct position, then placing the restraining pin behind the mast foot so as to allow you to find that same setup again next time).

    *N.B. I’m not implying that the tip of the mast stays in the same place irrespective of where the mast foot sits. But by adjusting the shrouds and forestay you can get both ends of the mast where you want them, with rig tension, and thus have the pivot pin free to move. The shrouds and forestay act as a sort of tripod, and moving the mast foot backwards will move the mast head forwards. You may therefore need to shorten the shrouds slightly to keep the mast tip in the intended position.

    #11884
    Colin Parkstone
    Participant

    And do not take the spreader measurements as gospel, each boat is different so try to get the prebend and rake by having the spreaders and shrouds help you, not hinder.
    If you need more prebend, let the spreaders aft of the norm to open the distance between shroud ends and the aft of the mast for example!
    If i told you that i worked on a boat that was 25mm longer one side than the other and the shroud plate points were 25mm different each side as they had been measured from the transom, not the bow it will give you an idea of what can differ in a boat.
    Use the tools on the mast to help you, not hinder!
    CP

    #11832
    matoi
    Member

    @Andrew Morrice wrote:

    We found our pin was being pushed forwards in the tabernacle against the aft aspect of the pin-hole in the mast…
    Anyone else had this trouble or can cast any light on it.

    First, I apologize for intruding, as Dave and CP are far more experienced and knowledgeable than me.

    But, I do intrude because I have experienced something that could be similar to your situation, and which I haven’t seen much written about:
    once upon a time, after sailing in some strong winds and after coming to port, I noticed the foot of my mast had SLIPPED forward in the mast step (black track). It seemed to have slipped until the pivot pin blocked it from slipping further, being squashed by the forward part of the tabernacle pin hole, and aft side of the mast pin-hole (just like you describe).

    After starring at all this and pondering about it for some time, I came to a theory:
    If you look at the mast foot, there is a feature (which I’ve colored in orange in the image I’ll try to attach) which I presume the mast maker intended to be used to lock the foot of the mast by means of something like a second pin in the mast-step-track and which would prevent it from slipping forward (the first pin blocks the foot of the mast from slipping aft, and we all have that pin in there). Wayfarers don’t use this feature, maybe because it would be a bit of a nuisance when rigging or dismantling the boat or shooting bridges.
    The problem is hidden for those who have the jib halyard led from the mast foot aft along the centerboard case and cleated somewhere in the hull. They don’t perhaps experience the slippery consequences becase the halyard tension in such setup helps keep the mast foot against the aft (and only) pin in the mast-foot-track.
    But those who cleat the jib halyard to the mast itself, don’t have a means of keeping that foot firmly in the desired place. In such setup everything might seem ok if the rake is small and while the wind and seas haven’t yet increased the tension and started shaking the boat (the friction in the system keeps things in place like in a tower of cards)…

    So, if you happen to have the jib halyard cleated on the mast, I would suggest you consider this theory and if you don’t see it silly, perhaps before going about adjusting the rig create a way of keeping the mast foot where it belongs…

    Let me know if you do find this suggestion is all nonsense.

    All the best,
    Mato

    #11889

    thanks everyone for these very full and helpful replies.
    just to clarify, ref Dave and Matoi’s answers our mast comes back pretty reasonably through the mast step without too much resistance or mashing of the foot, and we have our rig tensioning led aft to the c/b case.
    ref Colin’s answer our spreaders were different when we aquired the boat, but a very confident boating colleague offered to change them back to the standard in the W book and I didn’t record the old settings before he did that. His set up required permanent chocking (about 12mm) but we didn’t loose the prebend as happened this year. This time round we did spend a fair bit of time thrusting the spreaders back and out to get some of the prebend back in but (as far as I recall – it was hot and we were getting tired) to no avail.
    We’ve just come back from our trip to Britanny which featured a rather unwelcome crisis with the boat which I may write up later: (suffice it to say we started our holiday with three days off the water and we were very glad I’d packed some epoxy and all my tools!). Just now she’s sailing beautifully but I’m keen to try and square the circle sometime soon. I will report back when the solution has emerged!
    B

    #11890
    Dave Barker
    Keymaster

    Glad to hear that you seem to have had some successful sailing although seemingly not a completely stress-free break (forgive the unfortunate choice of words).

    I’ve just re-read your original post, para 2, which seems crucial. The way the pivot pin was being pushed forward in the tabernacle required the restraining pin (and hence the mast) to be brought back, not forward, so I think you must have misunderstood the instructions here. But then you said that you tried bringing it backwards instead, but that didn’t work either. It should have freed the pivot pin, provided the mast foot came back to meet the restraining pin in its new, further back position. Bear in mind that (in this part of the procedure) you’re just seeking to align the holes (mast & tabernacle) with each other, fore and aft.

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