Shrouds

GP14 Sailing Forums Forum Shrouds

This topic contains 7 replies, has 3 voices, and was last updated by  Oliver Shaw 3 weeks, 6 days ago.

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  • #16903

    Johng37
    Participant

    So I have just stepped my mast and I have found that my shrouds are quite slack, my forestay is tight and I’m struggling to get the shrouds any tighter, should I do the shrouds first then try to get the forestay on or is that normal? Also there are no spreaders it’s just attached to the mast if that helps?

     

  • #16904

    Oliver Shaw
    Moderator

    Since you have no spreaders my expectation is that you have either a wooden mast or one of the first generation metal masts (almost certainly in that case either IYE (gold anodised) or Proctor (silver anodised)).   This also ties in with your earlier post saying that you have inherited the boat,  and the implication that she is an elderly boat,  what some might call vintage:   indeed if she is old enough I myself might call her vintage,  and that would be with a great deal of respect!

    There are tuning guides available in the Members’ Library,  but they are all aimed at the modern rig,  with bendy spars,  and high rig tensions.   My purely personal view is that these are of limited use for your rig.

    What I myself would do is to set up the mast in the gate,  with the gate closed,  and then attach the shrouds.   If you are using rigging screws (which is quite likely on a boat of this age,  although that is not an invariable rule),  now set them up hand tight,  and lock them.   As a purely temporary arrangement,  use the locknuts provided,  but once you have done your experimenting (see later),  and are satisfied with the final adjustment,  secure them with monel seizing wire (readily available from all good yacht chandlers) in order to prevent them unscrewing.

    If you are using other types of adjuster,  set them JUST FRACTIONALLY too tight to engage without first easing the mast back a little (open the gate for this),  then secure the shrouds,  push the mast back into the gate,  and close the gate.

    Then,  and only then,  attach the forestay.

    The forestay serves very little purpose most of the time,  but it is a vitally important purpose nonetheless;  it is there to support the mast when you have no headsail set.   And in the original thinking for the rig,  in common with normal practice at the time (the boat was designed in 1949),  it also serves as a guide to the luff of the jib or genoa,  which is hanked onto the forestay;   it helps to keep the sail on the deck and out of the water while hoisting or lowering,  and it gives additional support to the luff when hoisted in order to prevent it sagging away to leeward.   With modern rig tensions this last is redundant,  because the luff tension is far greater than the forestay tension;   normally on a modern boat the headsail is not even hanked onto the forestay,  and the forestay goes slack when the sail is hoisted and the luff is tensioned.

    Once that is done,  at your convenience (and it is now getting a little late in the year for many of us) take her out for a sail and see how she handles.   In particular,  how is the helm balanced,  and how well does she go to windward?

    My guess is that this setting will be about right,  but if you start racing her you will find that you want to tweak the mast rake slightly.  Rake it just a little aft (i.e. tighten the shrouds) if you feel that (when sailed absolutely upright) she does not perform to windward quite as well as she should but goes well off the wind,  and has a natural tendency to turn away from the wind (i.e. she carries slight lee helm).   Conversely the reverse;   rake it just a little foreward (i.e. ease the shrouds) if you feel that (when sailed absolutely upright) she goes very well to windward but less well off the wind AND tends to turn into the wind (i.e. she carries weather helm).

    This final stage is all a matter of experimenting,  over an extended period;   and I know nothing about your sailing skills.   In order to do it effectively,  it is easiest if you have reasonable racing skills,  and if you hone her in race competition with other GP14s whose helmsmen have a comparable level of skill.    If that is not viable,  or if you don’t yet have that level of skill,  don’t hesitate to ask an experienced member of your club to take the boat out with you,  to evaluate the rig balance and advise you.

    One final point;  I have referred in passing to modern rig tensions.   Do not attempt to generate modern rig tensions on an older Series 1 boat unless she has been specifically adapted to handle them,  by having the approved mast step conversion fitted.   Otherwise you risk serious structural damage,  which at worst could  –  at least metaphorically  –  push the mast out of the bottom of the boat.   Modern tensions are vastly greater than the boat was designed to support,  because in 1949 no-one ever envisaged such rig tensions being applied.    If your boat is fitted with the original type of fittings,  or even such tensioning devices as a toothed rack (across the halliard) or a Highfield lever,  you will be fine;  you can safely apply as much tension as you can generate by hand.   But modern “muscle boxes”,  and powerful cascade tackles,  are a big no-no unless you first do the mast step conversion.

     

    Oliver

    • This reply was modified 4 weeks, 1 day ago by  Oliver Shaw.
    • This reply was modified 4 weeks, 1 day ago by  Oliver Shaw.
  • #16907

    Johng37
    Participant

    Wow oliver, your knowledge astounds me..you are right about the boat being vintage..you are correct about the gold mast as well, she is fiberglass with the built in buoyancy tanks..I think she’s 1970”s at least.

    Anyway she just has the basic shroud adjuster where you move the pin in the different holes, I will give the suggestion’s you have given and hopefully that will work

    Thanks for taking the time to reply I appreciate it.

    While I’m at it I’m thinking about painting the deck as there is a few stress cracks and a dent that needs filled…any suggestions on the type of paint I should use or avoid it all together

     

    Thanks again

    John

    • #16919

      Oliver Shaw
      Moderator

      Be aware that the early GRP boats had occasional issues of structural strength,  and there have been occasional cases of chain plates pulling out of the hull.   Although uncommon,  that is a risk to be aware of in the context of your stress cracks.   If the stress cracks are in that area,  reinforce it heavily.

      What I don’t know is whether on those boats the chain plates are screwed into hardwood (or even plywood) pads bonded into the fibreglass;    certainly that method of construction has been used on some GRP boats,  and not only GP14s,  and there have recently been some well publicised cases of failure in such construction on the Speed GP14s (much more recent than your one).   If it appears that that is the method of construction on your boat,  and others may well be able to shed light on this point,  it is a relatively straightforward repair to grind away the GRP until the wood is exposed,  then replace the wood (using marine hardwood,  nothing less),  and then laminate up again.    But if you are in luck you won’t need to do that!

       

      Oliver

  • #16917

    Oliver Shaw
    Moderator

    My oldest sailing friend did a stunning restoration on an early GRP GP14,  and he painted her with Toplac.    This is an International Paints product,  and is a top of the range conventional yacht enamel,  available from any good yacht or dinghy chandler.   I have used it myself on wooden boats,  and have also had superb results from it.

    The top of the range product,  provided you are painting direct onto bare GRP (with no previous paint of unknown type) is 2-pot,  most usually found in the form of 2-pot polyurethane.   But that is much more expensive,  and more troublesome to apply.

    On my trailer-sailer yacht I have used Epifanes Monourethane on the deck and cabin,  and am well pleased with both the way it went on and with the end result.   That is a sort of half-way house between Toplac and a two-pot paint,  and it seems to be more successful than the one-pot polyurethanes of 50 years ago,  which was the point at which I decided that the technology offered the limitations of both with the benefits of neither!   The technology seems to have advanced considerably in the last 50 years,  as one would hope it would have done.

    In either case you will need to prepare the surface,  and you may need to apply a primer and an undercoat.

    If you are right about the cracks being stress cracks they will have weakened the hull,  so they need proper repair.    The official dictum is to grind out the damage,  and laminate up new GRP,  using marine epoxy resin (NOT,  repeat not,  polyester,  even though that is what she was originally built with).   The big problem with polyester resin is adhesion;   it does not adhere well to most substrates,  even including cured polyester.   It is fine as a building material (although epoxy is both lighter and stronger),  provided it is always applied wet on wet,  completing the entire lamination in one go.

    However if the damage is only very local,  my own thinking is that an alternative might be  –  depending on the location  –  to first reinforce on the inside,  by laminating on additional layers of GRP,  here again using epoxy,  to provide the required strength and rigidity irrespective of the damage to the original laminate.   Then you can simply grind out the cracks,  and fill them.   That may well be the easier route.

    Good luck.

     

    Oliver

  • #16923

    Johng37
    Participant

    Oliver..thanks for your help

    John

  • #16928

    Arthur
    Participant

    I know on my wooden masted Series 1 (1964 vintage) I tend to keep the shrouds just tight enough to keep the leeward one from going slack.

  • #16929

    Oliver Shaw
    Moderator

    There are actually two separate parameters,  which it is sometimes easy to confuse because they can seem to be interrelated;   the length of the shrouds,  and the tension in them.   They are in fact largely independent,  although with the modern high load rig there is some degree of interaction between the two (but only because steel is an elastic material  –  albeit with an inordinately high Young modulus  –  so the wire stretches,  very slightly).

    The tension when ready for sailing,  but in zero wind,  is essentially the same as the tension in the headsail (jib or genoa) luff,  and is determined by the tension you apply to the headsail halliard.   (Because the angles aren’t identical those tensions are not quite equal,  but there is a fixed ratio between them;    so they vary in exact proportion,  and for our present purposes you can consider them as being essentially the same.)    That tension is then modified by wind loading when you are actually sailing.

    The length of the shrouds,  not the tension,  determines the amount of mast rake.   So in practice that needs to be set first;   with the modern rig (bendy spars and high rig tensions) it needs to be set with the desired amount of pre-bend,  but with vintage boats we don’t need to go quite there.    Then,  and only then,  is the tension applied,  by tensioning the headsail halliard.

    Having the shrouds (i.e. the entire rig) just tight enough to prevent the leeward shroud going slack is entirely a matter of how much tension you apply to the halliard,  and it has nothing to do with the adjustment of the length of the shrouds.

    Hope this helps,

     

    Oliver

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