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

  • This topic is empty.
Viewing 15 posts - 16 through 30 (of 42 total)
  • AUTHOR
    POSTS
  • #9222
    Algol
    Member

    @Colin Parkstone wrote:

    Yes Algol, the pivet pin holes in the tabernacle. They have a measurment postion and if they happen to be to far forward, that may not help your prebend.

    C P

    Just measured it and all seems well.

    Transom to mast pivot is dead on what it should be. Transom to shroud is about 20mm less than the max allowed.

    #9223
    BluTak
    Participant

    Hi Swiebertje your advice makes good sense. I only cruise and reef rather than flattening the main over much. After what you’ve suggested I propose to get the sleeve welded around the edge to the mast. What do you think? I know a very good welder who will do it for me (my welding would no doubt melt the mast!). I’m afraid I am a very impecunious Wayfarer sailor and can’t afford a new mast. I’d value your advice. Robert

    #9228
    Colin Parkstone
    Participant

    It maybe an insult to your welding friend but find him a bit of mast too play with first to see if its an Ok job to do.
    I have in the past spoken to welders about doing this same thing and they were all advising caution when doing this job on mast metals.
    It can be done but you only have this mast and it works at the moment, your insurer may also bulk at a modified mast if it fails at a later date.
    Caution, but Goodluck,

    C P 😐

    #9229
    Colin Parkstone
    Participant

    Algol, What size pin are you using,maybe it does not have much movment if its a large one.

    I would take it out and play about without it till you have some prebend,then try to fit it back after!
    As for your block to block pointing in light airs, was the kicker off and the leach open with the mainsheet in the centre of the boat but with no downward pull on the boom.

    If not, i would say you were not set as well as you could have been and may have only over ridden the lack of prebend with mainsheet tention and have been lucky to have had enough wind to have over riden the hard leach tention a hard mainsheet would have given you.

    Light, f1to f2 winds, the kicker light and the boom near the centreline is good as this gives an open leach to the main and allows the wind to exit the main without having to fight a hard leach.

    C P

    #9231
    Swiebertje
    Participant

    @BluTak wrote:

    Hi Swiebertje your advice makes good sense. I only cruise and reef rather than flattening the main over much. After what you’ve suggested I propose to get the sleeve welded around the edge to the mast. What do you think? I know a very good welder who will do it for me (my welding would no doubt melt the mast!). I’m afraid I am a very impecunious Wayfarer sailor and can’t afford a new mast. I’d value your advice. Robert

    Welding aluminium can be done with specialised welding equipment. Also you need someone experienced in aluminium welding. Welding aluminium is much more difficult then welding steel. On top of that, the mast walls are rather thin. The average “friend who lives around the corner” welder can’t do it IMHO. But it has been done several times.

    Be aware that a repaired mast cannot be used while racing and the characteristics will be different.

    Not so long ago an US Wayfarer sailor fixed a broken mast by inserting a piece of ‘aluminum’ inside the mast to support it. His story is here: http://www.wayfarer-international.org/WIT/maint.repair.ref/mast.repair/mast.repair.html

    #9232
    Colin Parkstone
    Participant

    Think your find that a repaired mast, but not improved would be looked at with sympathy in the racing world,I would !

    A sleeved mast would not be as it would have been stiffened over and above the standard mast!

    C P

    #9233
    Algol
    Member

    @Colin Parkstone wrote:

    Algol, What size pin are you using,maybe it does not have much movment if its a large one.

    It’s 6mm. I’m going to go through the whole setup process again this week as soon as I borrow a rig tension gauge.

    @Colin Parkstone wrote:

    If not, i would say you were not set as well as you could have been and may have only over ridden the lack of prebend with mainsheet tention and have been lucky to have had enough wind to have over riden the hard leach tention a hard mainsheet would have given you.

    I’d say you were about spot on there, Colin. The conditions were between sitting in, out for a bit, back in almost straight away, slide out a bit etc etc

    #9238
    BluTak
    Participant

    Hi Swiebertje / Colin – My welder friend has a commercial welding shop and is Asme certified etc so no problems there. He’s welded cast iron, bronze castings etc for me in the past as well. Has anyone welded around the sleeve before (ie a fillet weld all round) and should this help?
    Don’t worry about racing – I’ve sailed for 45 years now and never won a race though I did pick up a prize for”good attendance” in my Laser dinghy!! Robert

    #9246
    Algol
    Member

    So, I got a new spreader bottle screw and started mast setup this afternoon.

    I went through all the steps 3 or 4 times. By the time I finished rake and rig tension were within tolerance and the pivot pin is loose, but I only have about 8-10mm of pre-bend.

    I’ve been cranking back the spreaders to try and get the required 25mm-38mm of pre-bend on. They really are way beyond where they should be in an effort to induce bend (see pic below).

    The next step? I could keep moving the spreaders back, but really I think I have to take ‘that mast chock thing’ (see pic post 2) out and support the mast from the sides only to allow the mast some room to bend forwards.

    #9247
    Colin Parkstone
    Participant

    Do we take it that the mast with all you have done hits the front of ” The Thing “?

    How much is the front of “The Thing ” behind the front of the mast gate front below ?

    Is it glued or screwed in ?

    Maybe you could just cut out the front of ” The Thing ” and leave the sides to help side chock the mast?

    C P 😕

    #9248
    Algol
    Member

    @Colin Parkstone wrote:

    Do we take it that the mast with all you have done hits the front of ” The Thing “?

    How much is the front of “The Thing ” behind the front of the mast gate front below ?

    Is it glued or screwed in ?

    Maybe you could just cut out the front of ” The Thing ” and leave the sides to help side chock the mast?

    C P 😕

    Yes, the mast butts up against ‘the thing’. It’s screwed in with a single screw that goes in towards the bow. I’ll take it out tomorrow and see what difference that makes. If it solves the problem I’ll have to think about making some side spacers for the mast.

    #9251
    Algol
    Member

    *lunchbreak report*

    Without ‘the thing’ in place I can achieve the required pre-bend. (The front of the mast is hard to forward of the slot it sits in.) But, I cannot get the pivot pin in – it fouls the rear edge of the hole in the mast . The mast foot pin needs to move backwards by 2-3mm, but there’s no more movement to aft available.

    Is it a total no-no to make the kingpost hole a bit bigger?

    (I’m wondering if another type of adjustment can make that unnecessary, however. At present the rake is at its maximum — 7190mm. If I decrease the rake I think I will possibly achieve two favourable outcomes: pulling the mast backwards a) from the front of its slot b) towards the hole in the kingpost)

    #9252
    Algol
    Member

    The new side spacers. A temporary arrangement to get me sailing this weekend (hopefully)

    I want to find a more durable material to make them from. Anyone worked with PTFE?

    #9253
    W10143
    Member

    Algol

    I want to find a more durable material to make them from. Anyone worked with PTFE?

    I have striven to have an entirely plastic boat 🙄 …. and as such have used those PTFE chopping boards both as washers and spacers. They are easy to cut and come in various thickness’ but I have found that the pieces do split under compression – so probably not what you want in that position unless glued in place. Why not epoxy those nicely chamfered spacers in place?

    David

    #9254
    Swiebertje
    Participant

    @Algol wrote:

    Without ‘the thing’ in place I can achieve the required pre-bend. (The front of the mast is hard to forward of the slot it sits in.)

    …..

    Now you know why we insert removable chocks in light winds. They allow us to put some tension on the rig without bending the mast (much).

    @Algol wrote:

    But, I cannot get the pivot pin in – it fouls the rear edge of the hole in the mast . The mast foot pin needs to move backwards by 2-3mm, but there’s no more movement to aft available.

    If you can’t move the pin further aft, perhaps you need to reposition the mast step? BTW, the mast step pin is a course adjustment, a penny (or two) between the pin and the mast foot can be used for fine tuning. If you decide to re-position the mast step, check if the mast hole lines up with the tabernacle holes vertically. If not you could put a small plastic riser below the mast step. I have used some Formica for this.

    @Algol wrote:

    Is it a total no-no to make the kingpost hole a bit bigger?

    That is indeed a big NO-NO
    The holes in the mast and in the tabernacle, with the mast pin inserted, limit the amount of play and ensures we all have the same amount to play with. It is one of the things a measurer looks at while scrutinizing a boat before a major racing event. Basically the mast pin seems to have no function (it just rattles around) but it is used as a means to limit the amount of mast trim.

    Note: a test has shown that a woody in capable hands runs significantly better when the entire mast is moved back an inch or so. But at the same time the boat becomes much harder to handle by a less experienced sailor. Anyway, the discussion is moot because the rules simply don’t allow it. The hole rules have two purposes, to make it a safe boat and to create a level playground.

    @Algol wrote:

    (I’m wondering if another type of adjustment can make that unnecessary, however. At present the rake is at its maximum — 7190mm. If I decrease the rake I think I will possibly achieve two favourable outcomes: pulling the mast backwards a) from the front of its slot b) towards the hole in the kingpost)

    Answered above.

    BTW, your new side chocks look exactly like the ones I had on my old boat, a MK2. Ply is perfect and may turn out more durable then plastics. Remember that there is a lot of force and friction going on while sailing. The mast is not static but moves all the time. You may find that plastics are either too soft or too brittle to last. Maybe POM is strong enough?
    I simply varnished the ply chocks. If you rather have plastic, paint those ply chocks with yellow polyester paint…..

Viewing 15 posts - 16 through 30 (of 42 total)
  • You must be logged in to reply to this topic.