Latest News: Forums Technical Pivot Pin

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  • #3782
    Elsegood
    Member

    I am a novice Wayfarer and have just purchased a MK11 9365. The boat did not come with a proper Pivot Pin and we are at the head scratching stage and would be grateful for any advice.

    Can any bolt be used for the purpose and if so wehat would be the ideal diamater. I originally thought that this would have to be a tight fit but I think i have read somewhere that soem play is desirable. I’m presuming the pin is kept in place one the sail is up and that the mast once tuned is held in place by ‘chocks’ I know its a noddy question but do I have that right?

    Thanks & regards to all Paul

    #7201
    Bob Harland
    Participant

    Paul, you are correct about the pin, it’s use is only for pivoting the mast when raising or lowering. When sailing there should not be any pressure on the pin and it should rotate freely.
    The class rules state a pivot pin diameter 6mm (1/4″), there’s an example on Trident’s shop;
    http://shop.trident-uk.com/acatalog/Other_Spar_Fittings8.html

    You certainly want to use plain rod rather than a bolt, I would guess it’s pretty easy to make one yourself if you have access to suitable materials and tools.

    bob

    PS
    If anyone knows where you can get mini R clips rather than split rings/pins perhaps they could let us know.

    #7202
    Elsegood
    Member

    Thank you for your promt response Bob. It’s all coming clear now and what a fantastic service from UKWA. Given that the pin has no mast supporting role does the mast just sit there standing on the foot held in place by the forestay and shrouds. If so I guess the chocks then come into play. I don’t have any of these but I’ve seen elsewhere that they can be easily made up. I wondered if the rubber tapered door stops you see might work in a pinch.

    With regard to R Clips. I have found a selection of these, at Fox’s Marina Ipswich, down to a size (and smaller) that fits through the hole in the lower rudder pinacle. I felt that was a good idea!

    With thanks Paul

    #7203
    Bob Harland
    Participant

    The racing people will fit chocks forward of the mast – between the foredeck and mast, this is to limit the bend of the mast. There will still be a gap with the chock in place. Laterally the fit at the foredeck is usually snug, more recent masts had a collar to achieve this, as I recall older masts did not.
    The main thing is the stop (mast step pin) at the base of the mast support – usually adjustable in a track. This is aft of the mast heel it self, and the kicker works against this stop and your deck level chocks to control the bend in the mast.

    You might want to refer to the tuning setup guide on;
    http://wayfarer.org.uk/index.php?option=com_content&task=blogcategory&id=31&Itemid=104
    – this talks about the pivot pin and the mast step pin and how to get them right.

    So it’s really the shrouds, jib halyard/forestay and mast step pin that dictate where the mast sits.
    The deck level chocks and kicker will then control mast bend. The chocks only limit the mast bend at deck level. You will need some input from a racing person for more detail on using the deck level chocks. We had some with our boat made from perspex, timber might be better (it floats, not sure about perspex!). The shape is a sort of fat stemmed T, so they don’t drop down. For cruising and club racing you don’t need them.


    You might want to buy the Wayfarer Book, available on CD from the secretary;
    http://wayfarer.org.uk/index.php?option=com_content&task=view&id=37&Itemid=162
    The book covers a lot of this stuff.

    thanks for the tip on the R clips

    bob

    #7204
    Elsegood
    Member

    Thanks Bob: I’m awaiting a Wayfarer Guide but i’m grateful for the advice.It’s something i can tick off my query list. Regards Paul

    #7215
    John1162
    Member

    I have just spent half a day setting up my new mast using the tuning guide on the web site and yes it did take half a day. I now have a mast that I can bend or straighten using plywood chocks.
    Bob, I am pleased you will not be using chocks when cruising. I might be able to get in front of you.

    #7217
    W10143
    Member

    John

    I’d better set my mast up properly for Holy Is then!

    David

    #7219
    matoi
    Member

    Hello all!

    I haven’t yet used chocks, but was recently reminded about this when I noticed that my mast slides a little bit forward in the mast step when a bit higher jib halyard tension is applied (everything seems fine when the mast and jib are hoisted with lower halyard tension). Then it is not firmly pressed against the mast step pin, the pivot pin is not loose any more, and all this must not be very good since the mast probably continaully ‘works’ (slides a tiny bit forward/backward) when the boat sails in the waves. I should also note that my jib halyard tensioning device is mounted on the mast, rather than on the centerboard case.

    Perhaps chocks help around this problem a bit. Also, probably jib halyard tension – if a tensioning device is installed on the c/b case – keeps the heel pulled back against the mast step pin firmly enough.

    But in future I intend to look into the possibilty of modifying the mast step so that the mast heel is locked into position there in both forward and backward direction regardless of other devices. The mast heel seems to be designed with this idea in mind since it has a ‘cut out’ in the middle as to sit on top of a large pin. It should be a ‘cleaner’ solution for a non racing purpose.

    Best regards,

    Mato

    #7220
    John1162
    Member

    Mato,
    I have a highfield lever on the mast for tensioning the rig. When correctly set up as in the guide I have never noticed the mast foot moving. It could move if the pin was not free to move when the pin could act as a pivot. With the pin free and mast chocked you should not have any movement at all.

    #7221
    matoi
    Member

    Thanks John!

    I will put chocks in there next time I go sailing. They are already prepared somewhere in my gear jungle.

    Best wishes!

    Mato

    #7228
    Swiebertje
    Participant

    @matoi wrote:

    Perhaps chocks help around this problem a bit.

    The purpose of chocks is to prevent the mast from bending in light winds. They allow (some) Genoa halyard tension without bending the mast.

    Mechanically the following happens:

    By tensioning the Genoa halyard the hounds move slightly forward but more important, they are pulled downward. The hounds can only go down if something gives, in our case the mast gives by bending.

    So, the hounds are one fixed point (sort of) the other fixed point is the pivot pin (rules require it). If don’t want the pivot pin holes to move, something else has to be allowed to move, in our case the mast foot (backwards). Hence it would be a bad idea to fix the mast foot to the mast step and also we should be careful with applying halyard tension when the chocks are in.

    If you are a cruiser you could fix the mast foot to the mast step I suppose. But then you need to take the pivot pin out. If the mast is fixed by the hounds and by the foot it must be allowed to bend in all other places. But, as a cruiser, I want my mast pin in because in my case it is an extended mast pin that doubles as the anchor roll axle.

    #7231
    matoi
    Member

    XXXXXX

    Thanks for warning about applying tension with the mast chocked. But there are some points in your post that aren’t clear to me.

    By tensioning the Genoa halyard the hounds move slightly forward but more important, they are pulled downward. The hounds can only go down if something gives, in our case the mast gives by bending.

    Have you ever tried this:
    Tension the genoa halyard to the low setting (following the table in the W Book), walk away from the boat and take a good look at the shape of the mast. Then tension the halyard to the high setting, and go take a look again.

    I did this, and I can tell you that the mast stays just as straight at the high tension, as it is at low tension. It bends only after applying kicking strap tension. And it’s no wonder since the resultant force from the tension in the genoa halyard draws at only about 7 degrees from the mast itself. So, you can’t bend the mast by genoa halyard only, at least not to a significant amount.

    If don’t want the pivot pin holes to move, something else has to be allowed to move, in our case the mast foot (backwards).

    How can the mast foot move backward if there is a blocking pin in the mast step track?

    …you could fix the mast foot to the mast step I suppose. But then you need to take the pivot pin out.

    The mast bend is so small in the region of the pivot pin, that the pivot pin could stay where it is. I don’t use the anchor roll axle, but I don’t want to get rid of the pivot pin because it makes hoisting and lowering of the mast easier.

    Best regards,

    Mato

    #7242
    Bob Harland
    Participant

    It is normal to apply some pre-bend when tensioning the genoa halyard. If you are using a highfield lever one hand against the mast, the other pulling the lever will do this.
    Hence the hounds move forward and downward.
    if you dont apply pre-bend then you will not have the correct tension in the stays when you put the kicker on and the mast does bend.

    bob

    #7243
    Swiebertje
    Participant

    Deleted

    #7244
    matoi
    Member

    Deleted.

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