21/04/2019 at 6:25 pm #17948
The forestay on my GP14 (series 2, wood, 1993) needs to be replaced – it’s 2.5 mm wire and has started to fray.
Looking around our boat park it seems that GP14s usually have wire forestays, which are strong, but they are attached to the prow by loops of cord or bungee, which are not so strong. If the forestay’s job is to support the mast when onshore does it need to be wire? But if it’s to ensure the mast stays up when sailing without a jib/genoa doesn’t it need more than just cord or bungee at the prow?
The Pinnell and Bax website has both a wire forestay and a ‘rope forestay with elastic’. I haven’t asked them but the rope forestay looks like it might be Dyneema.
Has anyone got views on this?
21/04/2019 at 9:35 pm #17949
The design of both the GP14 and of sailing dinghies more generally has evolved over the 70 years since the boat was designed (designed, and protopype produced, late 1949). Historically, the forestay supported the luff of the jib when sailing, and the jib was hanked onto the forestay in order to allow it to do so, as was normal at that period; but with the advent of greater rig tensions (from about the sixties onwards) that role became redundant.
You are absolutely right in thinking that with today’s evolved rigging practices two requirements still remain; to support the mast in the dinghy park (with no sails set), and also to support the mast when sailing if for any reason the headsail is no longer set. The second, in particular, requires adequate strength.
At least some GP14s have a (wire) forestay of much smaller diameter than the shrouds, and although in strict seamanship terms that may cause raised eyebrows I have never heard of one actually breaking under normal load.
The most usual modern practice seems to be to secure the forestay to the stemhead fitting by a length of line, but I at least have always used several turns of the line, so that there are at least six parts of the line sharing the load. I think that using just a single part is probably not strong enough. If elastic is used, I suggest that this should be additional to the several turns of (non-stretch) line; the purpose the elastic is only to pull the forestay taut when the full rig tension is on, not to be part of the securing system when no headsail is set.
In principle I cannot see any clear reason for necessarily choosing wire over dyneema, provided the ends of the dyneema can be properly terminated, but I am not sure how one could best achieve those terminations. Certainly not by tieing knots in the rope; a couple of years ago the RYA put out a safety advisory bulletin about the use of such ropes, and in essence it seems that the strength is vastly reduced by forcing the rope into tight curves, as is almost inevitable when tieing knots. Professionally made hard eyesplices at each end of the dyneema might be strong enough, but it might turn out to be simpler and perhaps cheaper to use wire.
The class Rules do not appear to specify the material, so they leave that to the owner’s choice.
Hope this helps,
- This reply was modified 1 month ago by Oliver Shaw.
22/04/2019 at 7:15 am #17951
Mine is very thin dyneema 1.5mm ish, certainly thinner than the more usual 2mm. Its terminated at each end with an eye splice, the spice at the lower end is adjustable and it has elastic sewn through it to take up the slack under tension.
The crux of this is what is the forestay actually for? In the somewhat unlikely event of a jib halyard failure the mast is going nowhere due to the gate. On a racing boat it seems that the sole purpose is to support the mast in the dinghy park. Wire is over the top for this load wise, thin dyneema is both lighter and gives less windage over the Genoa.
On a cruising boat where weight and windage are of less significance and the boat might be used under mainsail only something with more meat is probably advisable.
22/04/2019 at 11:10 am #17953
Chris makes a very valid point about the distinction between cruising needs and racing needs.
Agreed that jib/genoa halliard failure is somewhat unlikely, but one may feel that sound seamanship requires the boat to nonetheless be able to withstand that event if it does in fact happen; that is a personal decision.
I am less sure about “the mast is going nowhere due to the gate”; it may indeed stay in the boat, but the forces involved are potentially very large, and I can see the potential for irreversible damage should the forestay be not strong enough to handle the load in the event of genoa halliard failure. However modern masts are specifically designed to be able to bend, which does mitigate that risk to some degree.
23/04/2019 at 10:47 am #17959
My 2p worth – most GP have a wire forestay with rope at the bottom end to attach to the bow plate. More than one turn as Oliver says. In addition they have a bungee. When the boat is in the park, the gate is usually opened to relax tension on both the gate and the spreaders. When racing, the bungee stops the forestay being too loose as it can (depending on lengths/tightness of the rope) sag backwards and foul the genoa tallies (woolies).
When racing, should the genoa wire break (or shackle “come undone”) The load would be shared (unevenly) between the bungee/rope and gate. It _might_ prevent the gate getting ripped out of the boat or the mast crashing backwards. I have never seen that happen, so it is speculation! I HAVE seen that the gate can open if it is knocked when racing – again the rig tension on the genoa means this is not a big deal, but the gate should be closed when sailing.
26/04/2019 at 12:49 pm #17974
I fitted 3mm, 12 strand dyneema.
You can bury, with a 4mm fid, some elastic through centre of the dyneema to take up the slack. The ends of the elastic could be stitched or dead ended with an overhand knot.
Given a breaking strain of a metric ton, it should be fine.
This idea was nicked from various other people’s boats. It’s a pretty common sight.
16/05/2019 at 9:45 pm #18141
I used a length of very thin cord (string) on Confusion, and no-one ever complained that that was not in line with the rules. However, I made sure that the Genoa tack attachment was ultra secure, with oversize epoxied screws to secure the stem head fitting’ and I used both the pins, not one for the forestry and one for the Genoa, a halliard shackle that was a bit oversize, with a captive pin, and a very substantial wire Genoa halliard. If anything broke, even a wire forestay would not have survived.
Having said that, for a cruising boat (not something I ever did) a substantial wire forestay (same gauge as the shrouds) would be essential, allowing the jib/Genoa to be lowered leaving the mast totally secure. And in any case make sure that all the shackles, links, pins, adjuster strips, rigging screws and the hound plate are all in good order!
You must be logged in to reply to this topic.