Latest News: Forums Technical Mast Rake Muddle

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  • #19756
    fundoctor
    Participant

    Dear Wayfarers

     

    I have Mk2 GRP WF used for cruising. Reading the WF book I decided to have a go at sorting the mast rake. When the mast is in tabernacle and the genoa untensioned the mast bolt is moving freely. When I tension the shrouds to >150Kg the mast bolt becomes fast. If I take it out and then tension it is hitting the “back” of the hole in the mast. The remedy in the WF book for this is to move the pin on the footplate back. On mine it is quite awks to undo the pin – no Allen key is “short” enough. But, I noticed, if I put one spacer thingie (forgot name) in front of the mast, with the shrouds tensioned, the mast pin is again free.

     

    My question – if I sail with one spacer in front of the mast and my mast pin free – does this render my system nicely set up? Do I need to move the pin at the foot at all.

     

    All comment appreciated

     

    Cheers

     

    Trevor

    WF 9002

    #19757
    Dave Barker
    Keymaster

    Trev – that sounds only half a solution. What happens when conditions dictate that you want to let the mast bend away further to flatten the mainsail (i.e. without spacers in place)?

    The pin behind the mast foot can be difficult or almost impossible to move, and for this reason I replaced ours with a tough plastic block held in place by a pin several holes further back in the track, and therefore easy to access and adjust. (Once you can adjust it easily the whole process becomes less tedious).

    If your pivot pin is slender enough (allowed to be 6mm for racing I think, and anything you want – or nothing at all – for cruising) I’m almost certain it should be possible to have it free moving both with and without rig tension. The amount of movement produced at mast pivot hole level by rig tension (bending the mast) is relatively small.

    Moving the mast foot back slightly will inevitably move the mast head forward slightly, all else being equal, (because the “fulcrum” point is the top of the shrouds) but as you’re already so close to achieving the correct setting it may not even be necessary to re-adjust the shrouds. Do remember to check that the mast foot is back against the restraining pin each time before you measure the rake. (With an old towel or even a mast chock to temporarily close the gap in front of the mast at deck level, a forward shove on the mast as high as you can comfortably reach should prompt the mast foot to slide back against the pin).

    When everything is further out of adjustment than in your case, rig tuning is something that you have to “home in” on. Adjust, check, re-adjust, re-check, and perhaps even again for a third time, but getting closer each time. It takes a while, but if you remember that the mast (when upright) pivots fore/aft at the top of the shrouds and not at the so-called pivot pin, it all makes sense.

    #19765
    fundoctor
    Participant

    hi dave thanks for your thorough reply I just got a little window of time to look at this before I start to get out on the water and leave all sorts of minor adjustments behind me I like the idea of trying a narrow pinas as this might be ok without the spacer in place as you say I’m not clear how to adjust the foot of the masters you describe and this may be something to check out with you at the next clothing cruising conference which I’m very hopeful to attend next year fairwinds off to fowey tomorrow trevor

    #19766
    Dave Barker
    Keymaster

    To move the mast foot back, just put the restraining pin one hole further back (aft) in the track. This is probably too coarse an adjustment, so use packers (e.g. 20p coins) between mast and pin, or a plastic block, for convenience. Make sure (when you measure rake and also when you sail) that the mast comes right back against the pin (or block) when rig tension is on. That’s the reason for the forward shove high up on the mast.

    The shrouds fix the position of the mast three-quarters of the way up, so moving the mast foot back will slightly move the mast head forward. If this wrecks your rake measurement (it probably won’t) then shorten the shrouds by one increment to compensate.

    I’ve tried to illustrate some of this here.

    Hope you had a good time in Fowey.

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