Latest News: Forums Technical Can’t get pre-bend

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  • #9255
    Swiebertje
    Participant

    One more thing. Deeply countersink the bolts (screws?) in your side chocks so they will never touch the mast. Because of the forces and movements involved they will kill you mast if allowed to touch. That is why I glued mine to the boat with Sikaflex.

    #9256
    Algol
    Member

    OK, I’ll forget messing with the king post hole 🙂

    @Swiebertje wrote:

    If you can’t move the pin further aft, perhaps you need to reposition the mast step?

    I’m going to leave that idea on the backburner until I’ve done everything possible with currently possible adjustments. Right now the mast is as raked forward as it can be (7190mm to the transom). If I give the mast more rake by shortening the shrouds that should pull the whole mast backwards and hopefully bring the pin hole back into alignment (while also putting more space between the front of the mast and its slot, so win-win *touch wood*)

    #9257
    Colin Parkstone
    Participant

    Only problem I see with you just being able to put the pin through at the back of the mast hole is that your have no more room for more mast bend.

    The pin will be only letting the mast bend to that position and your put more strain on the pin when the kicker goes on harder or you take out a chock.

    Looks like you need that mast step back further in the boat. Would say you have a stainless chanel one at the moment, you could go for a new and better one but it maybe a little higher and so the mast pin may bind the hole Yet! again.

    C P

    #9258
    Algol
    Member

    What’s underneath the mast foot track? What would I be screwing into if/when I move it?

    Currently it seems to be screwed in with 3 woodscrew-like screws.

    Also, are there any reasons not to use Araldite as an adhesive for the varnished ply mast slot side spacers?

    #9259
    W10143
    Member

    Algol

    What’s underneath the mast foot track? What would I be screwing into if/when I move it?

    Buoyancy Tank in a Mk II – need to seal the screwholes well – but I seem to remember there is a reinforcement timber at that point.

    Also, are there any reasons not to use Araldite as an adhesive for the varnished ply mast slot side spacers?

    None to my knowledge – It works the same as any other epoxy and when I’ve used it has been durable enough.

    David

    #9260
    Colin Parkstone
    Participant

    Under the step is a wood reinforced pad so you can move the step,just fill the old holes and find a way not to drill and screw too close to them.

    Use Araldite or epoxy in the screw holes to hold the screws.

    As for the side pads, do varnish them as they will get wet and expand which may bind the mast movement.

    Also use stainless self tappers to hold down the step.

    If you go for a new type of step that is long, you can use a hard block instead of a pin behind the heel and hold it in place with a pin going through one of the rear holes in the step.
    This then lets you move the block via the pin, outside the confinds of the tabernacle which sometimes is just where the back pin is needed!

    C P

    #9345
    Algol
    Member

    POSTSCRIPT

    Today I moved the mast foot back 10mm. Now I have all mast settings within the recommended limits. I just need to make a 5mm chock as that’s what’s left in front of the mast

    Yay!

    #9346
    Swiebertje
    Participant

    Nice to hear things worked out fine. But I am not sure where you intend to chock the mast?

    There is no need to chock in front of the mast foot, only the aft movement must be limited. BTW, for fine adjustment, never use anything else then clean copper pennies between the mast foot and the step pin (for good luck).

    At deck level don’t chock at all as the mast must be able to move further forward when a gust of wind hits or when you pull the kicker. Chock at deck level only in very light weather to prevent the mast from bending. This will keep the main as deep as possible and at the same time allows a decent tension on the jib’s luff.

    #9347
    Algol
    Member

    @Swiebertje wrote:

    Chock at deck level only in very light weather to prevent the mast from bending.

    Is this to stop any bend or to keep the mast at the pre-bend setting?

    I’m guessing the latter because trying to stop any bend is likely to result in an inversted bend above deck level, no?

    #9348
    Colin Parkstone
    Participant

    Bert,
    I will have to disagree with the no chock in front of the mast in strong winds??

    That chock should allow he mast to bend forward yes,BUT stop the mast from binding the pin in the mast and king post.
    So yes have movement forward with the mast but not more than the pin.

    Also the rules state, no bolt forward of the mast heel in the step !!

    Algol, the later is only part right, I take out chocks in light light winds to let the mast move forward and FLATTEN the entry to the sail, not for any bepth in the sail. WHY ?

    Well, a sail only works when the wind exits the sail,ie flow.
    So if the wind is very light it takes longer to get across a rounded or full sail and hangs on to it and takes longer to exhaust.

    So a full entry is not good for light winds, flat entry, open leach via loose kicker is good.

    Then as the wind rises it becomes stronger so it can flow across the sail and not stick to it, this is when you can put in some fullness and lean against it.

    Then when the wind is strong, you cannot lean against it anymore so your want to flatten it so as to have less round and so the strong wind will exhaust fast again.

    Bit simplistic but I hope helps, from light to strong, flat ,fuller, flat !

    C P 😕

    #9349
    Algol
    Member

    So, a rule of thumb on chocks would be:

    Light airs – no chock – so sail is flattened by extra bend
    Medium – mast chocked so it doesn’t bend more than the ‘neutral’ amount and gives max sail depth
    Heavey/overpowered – no chock, flatter sail.

    I’m working on the basis that I have 1 chock that holds my mast in its medium wind setting, and remove it for light or heavy going

    Does this all look like it makes sense? 🙂

    #9350
    Colin Parkstone
    Participant

    The idea is that the chocks allow you to have as much or as little bend as you want as long as the pin does not bind.

    Control about the pin is the key!

    To take this bend in light winds further, bend the mast with the spreaders and rig tension, not by the kicker, your pull the leach on the main down too tight.

    Look at the leach tell tails, they tell you when the wind is exhausting the sail.

    Bent mast, flatter entry to the main and a flatter sail. Loose kicker to open the mainsail leach, mainsail angle and leach tension controled by the mainsheet.

    😕

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