Simon,

(For others reading this correspondence,  I should mention that I have met Simon and I know his boat,  after a fashion,  and know that it is one of the early GRP boats;   Mk 2 I think,  from memory.)

On your boat,  provided she is in sound condition (as indeed I believe she is) you should be able to safely install a Highfield lever.

One word of caution;   it is highly likely that the lengths of your halliards will be different from the modern standard lengths,  which are designed around a different mast and a different rigging system.  So a ready-made wire halliard is very likely not to fit,  and in all probability you would need to get one made to fit your boat.

I would expect that you could also use 6mm polyester,  either three-strand or braided,  provided it is the pre-stretched type;   and on Strait Laced I am fairly sure that I successfully used 5mm,  with my reefing gear.   Certainly that was fairly standard when the boat was new (then of course as 3/4-inch pre-stretched terylene),  although that was not in the context of reefing equipment.

(The old standard was to size ropes by circumference,  whereas the modern standard is to do it by diameter;   conversion factor is p,  which is slightly more than 3.    3/4 inch circumference on the old system therefore corresponds to 6.1 mm diameter on the new system,  so the corresponding standard size is 6 mm;   but modern sheaves designed for either wire or dyneema halliards tend to be narrower,  so on a modern boat 6 mm may be too fat for the sheaves;   I found that problem on A Capella,  although it was borderline and I managed to live with it.)

However modern high modulus polyethelene ropes (e.g. dynema or spectra) would be even better that pre-stretched polyester,  and the stretch of those is very similar to that of wire,  i.e. minimal   Using rope rather than wire does have some advantages for the average layman owner/skipper,  in that you can tailor the length to your own boat,  and can then make the splices yourself in the right places.

Most owners,  if using wire,  need to get it professionally spliced  –  although I do know one “lay” owner who has his own Talurit press,  and who did the wire splicing for me on my vintage boat.

Hope this helps,

Oliver

Having played with Dynema on my big boat.  That is what I would use over wire.  It not only is very resistant to stretching, but it is nicer on the hands and pulleys than wire.  If also will not release “fishhooks” if a strand should break.

After years of looking and not finding the information and motivation, 2022 may be the year I act on my unsatisfactory original forestay for my unknown make mid 70’s model.  I picked up a Highfield lever in a job lot of goodies and have concluded that a dyneema halyard is a winner at every level, as outlined above (and is cheaper too -sk75 can be had for ca £2/m in the smaller but very adequate diameters – 4mm can be ca 2000kg break load depending on brand. Plus you can do the work with minimum investment in tools and fully DIY it – YouTube provides.  This is an attractive price (I have no connection, just looking for a wallet-friendly source myself) https://www.accessropes.com/product/uhmwpe-stealth-rope/.  If anyone with experience of this could tell me if I’m adrift here, I’d appreciate it as I’d like to get this done this coming spring.

One correction to my earlier post:    I wondered just now whether I had been mistaken,  so have looked up a photo taken in 2005,  from which I see clearly that the genoa halliard on Strait Laced was wire;   it was the main halliard that was pre-stretched polyester,  of (I think) 5 mm diameter.   Apologies for the confusion,  but blame failing memory;   I sold that boat around 13 years ago.

However that does not invalidate the rest of the advice,  nor that of Arthur or Warsashod;   there is a lot to be said for going for dyneema.   You would probably get away with pre-stretched polyester,  with a Highfield lever,  as I did in the seventies with my earlier GP14,  Tantrum,  (although that was without reefing equipment),  but dyneema will have even less stretch.

One important detail is to terminate the ends in splices,  not knots;   dyneema (and other HMPE ropes) will not tolerate the tight turns involved in knots,  which weaken the rope very considerably.   RYA did a report on that a few years ago;   Link here.

Oliver

Hi,  Having used HyField leavers on a number of older GPs and had a few near misses with fingers when releasing the tension I would suggest that using a muscle box rather than the Hyfield is safer and is jus as easy to set up the tail from the muscle box can be cleated off on the mast.  If planning to use a wire halyard it is normal to exit from the back of the mast above the leaver, if you use a low stretch (Dynema or Spectra) rope this can be lead up to the leaver or muscle box from the normal sheave at the bottom of the mast.  The problem with this will be how to have a loop that will pass through the sheave box.

Preference use a wire halyard, muscle box with hook at top, exit for wire halyard and rope tail from hole in back of mast (if an internal halyard Super Spars or Proctor mast) or if an old IYE gold mast with the halyard in the sail track – open up the track so that the halyard can exit above the hook, take the tensioning rope to a Clamcleat fixed to the mast below the muscle box.

I use a hand swaging tool, two pieces of steel with bolts to clamp the ferule around the wire,  it has 3 or 4 different size holes for the normal wire / ferule sizes.  End results are not as neat as the professionally swaged wire but never had one fail and as it is portable has been useful for running repairs when travelling to Open Mtgs etc.  Copper ferules and hard eyes available on eBay.

Thanks,  Steve;   and I absolutely see where you are coming from,  but for other reasons I nonetheless beg to disagree.

A muscle box is potentially much too powerful for the strength of the early hulls,  which were never designed to cope with the tension which a muscle box can provide.   Remember that the design dates from 1949,  when tension was normally applied by little more than sweating up on a horn cleat,  perhaps aided by the crew pulling the middle of the forestay forward.   Come to that,  the hulls weren’t designed for the loads generated by Highfield levers either,  but that is less extreme,  and long experience (not mine,  but that of the Class as a whole) has demonstrated that the hull can safely handle that;   there is enough safety margin in the design.

But long experience (again by the many members of the class) has also demonstrated that using a muscle box,  or a powerful cascade tackle,  can cause serious damage to the early hulls.  That,  indeed,  is why the official mast step conversion was developed;   to adequately strengthen early hulls,  by spreading the load,  in order to enable modern rig tensions to be used.   There is no official equivalent for the early GRP boats,  but they are certainly not immune from the problem,  and I have just once seen a well-engineered DIY mast step conversion on such a boat (at Neyland YC,  in (I think) 2007,  when we were there for the UK National Cruising Week).

Of course,  if one installs a muscle box there is no need to tension it to its maximum potential;   but even if you fit a marker it is still fatally easy to do it inadvertently.

Yes,  one can cleat off a muscle box on the mast,  and not use a 2:1 inside the boat,  which is exactly the arrangement I had in A Capella,  but that still gives a mechanical advantage of 8:1,  which is rather a lot for the early boats.   Working out the M.A. of a Highfield is more complex,  but the headline ratio is that which applies when the lever is perpendicular to the mast;   I happen to have a dinghy Highfield on my desk as I write,  and the crucial measurements there are 35 mm operating radius for the point where the load is taken,  and 100 mm for the centre of the pad for the operating hand.   That gives a mechanical advantage of just under 3.   Alright,  the ratio increases as the lever is closed,  because the operating radius for the load decreases but that for the hand at the end of the lever does not,  which is what makes it complex to calculate,  but it is also the case that very little additional movement of the halliard takes place during that phase;   it cannot possibly be more than the 35 mm operating radius of the load attachment point,  so the tension will increase by only a modest amount in the final quadrant of closing the lever  –  although it is complex to calculate how much,  and one would need details of the halliard length and elastic modulus to calculate it.   Overall I feel that a little over 3:1,  perhaps 4:1 is fair for a Highfield,  which is about half what a muscle box will give even if you do not further boost the latter by a 2:1 inside the boat.

There is however a safe way to use Highfield levers.   When loading up the system  –  i.e.  applying the tension  –  you should use the ball of the hand to close the lever,  keeping fingers well out of the way.   When unloading  –  i.e. opening it  –  use one hand to initially pull it open,  with the ball of the other hand (and,  again,  fingers well out of the way) to act as a backstop to prevent it taking charge and opening with a slam;   once it is about half-way or perhaps two-thirds open there will be little load on it,  and the danger is past.   Simon will (I hope) remember me demonstrating this during the cruiser training course.

Like a lot of tools and fittings which can potentially cause injury,  it is important to develop safe techniques for using them.

Oliver