How to set up a centre main
10/07/2019 at 2:03 pm #18491
Hello all. I’d be very grateful indeed for any advice the members could give me regarding the best set up of a centre mainsheet on a GP14. My friend and I have bought a 1993 Duffin-built wooden GP14, sail number 13225. She is in good condition after some minor repairs over the winter. When looking into how to set up the centre main, almost all the examples and guidance online appear to show the mainsheet running up from a block fastened to the centre of the deck (which is present on our GP) to a single block fastened at the centre of the boom, and then running out to another single block at the aft end of the boom, from where it extends down until it meets a block fastened to a rope traveller extending over the width of the transom and then back up to an anchoring point. My question is this. Is this set up simply due to convention i.e. it’s done this way because it’s always been done this way, or is it seen as being the best set up for a dinghy of the GP14’s design? The reason for the question is that we are considering whether there is any merit in setting up the centre main so that it takes a couple of runs from a double sheave block up to another double sheave block under the centre of the boom and back down again, with no extension out to a transom traveller and aft anchor point. It’s a set up similar to one which you would see on, for example, a Laser Bahai. Is this is a good idea? Are there any arguments against it? Many thanks in advance for any advice.</p>
10/07/2019 at 2:22 pm #18492
the normal way to rig centre main is to use rope which has 2 tails sewn into the rear to form 2 hawses which run to opposite sides of the transom and are tied to the retaining brackets at the rear corners. There is no traveller as such and this system is particularly good since the leeward side hawse is an indicator which indicates the maximum amount the sail may be pulled in when sailing upwind —-should be a bit of slack as a minimum, otherwise it will overcome any kicker setting you have.
The hawse arrangement is shown in a photograph in the ‘beginner’s guide to rigging a GP14’ on the website .
10/07/2019 at 2:22 pm #18493
My understanding is that the usual method, which is almost but not quite what you describe, has a split-tail mainsheet rather than a rope horse.
This arrangement has the practical advantage, which I think is probably unique to this arrangement, that the boom is always sheeted to the windward side of the transom, while at the same time ensuring that (if the twin tails are set up symmetrically) it can never be pulled above centre. One result of sheeting to the windward side is that for any given position of the boom when beating to windward the sheet load is very much reduced, as compared with sheeting to the centre, because the working part of the sheet is less vertical.
The system does of course rely on having a powerful kicker, so that the kicker alone can control the shape of the sail, and the sole duty of the sheet is to control how far in or out the boom is set. With early, less powerful, kickers the sheet had to also help control twist in the sail, and for that duty a more vertical pull was helpful – but a consequence was that sheet loads were higher.
This is of course a hybrid system, but it is mechanically a highly efficient system. The alternative system which you describe is a true centre sheeting system, which does not seem anything like so popular on GP14s (I cannot comment on other dinghy classes), although it is common enough on yachts; but there the primary function of the mainsheet is to control twist in the sail (a function performed on the GP14 by the kicker), and the lower block is on a traveller, with the traveller control lines being primarily responsible for sheeting the boom in or out.
Hope this helps,
11/07/2019 at 7:50 pm #18518
Gentlemen, thank you very much for your helpful replies. It’s much appreciated. One issue which I’m not clear about is how one goes about achieving a split-tail mainsheet as you’ve both described. Does one achieve this by splicing or can one obtain a ready-made split-tail mainsheet? Apologies if this is a daft-laddie question.
11/07/2019 at 8:31 pm #18519
The short answer is “either, at your choice”.
If your splicing is up to it, and I am sure mine is not, you can make your own.
Alternatively I am sure that any dinghy chandler familiar with GP14s could supply one, quite probably off the shelf. However you may have to actually ask them; a quick search online just now has turned up only one: https://www.tridentuk.com/gb/8mm-split-tail-main-sheet-cut-to-suit-gp14-mirror-wayfarer-osprey-flying-15.html
Since the illustration for this one is red, and most that I have seen have been white, there are presumably many others readily available.
Hope this is helpful,
12/07/2019 at 6:19 pm #18529
Many thanks again for the excellent advice. We have decided to attempt to splice a split-tail main sheet (or at least my friend is…I have no skill in that regard). My one remaining question relates to the length of the twin tails. They obviously need to be of equivalent length. However, should they be spliced so that the junction between the tails and the mainsheet proper meets at the aft end of the boom when it is centred? Or should the junction between the mainsheet proper and the tails rest at some point along the boom when it is centred? Is there are an ideal length?
Many thanks in advance for any guidance you can give us.
12/07/2019 at 8:36 pm #18530
The splice should at all times remain clear of the boom, but ideally only just clear when sheeted hard in. The splice will be thicker than the rest of the rope, so if you allow it to run into the block it may jam.
That said, I think there is a considerable degree of latitude, but for greatest efficiency in terms of minimising the sheet loads the splice should be as close to the boom as possible when centred and sheeted hard in (with the sail set, of course), as long as it remains outside the block.
One method that I inherited on the only boat of mine which had this system (as a cruising man I prefer transom sheeting, although I concede the benefit of the other system for racing) had the tails left very long, and led through bushes in the deck and then forward to a pair of clam cleats in the cockpit. That way you can readily adjust it, although once you have got it right you may well never need to alter it again.
13/07/2019 at 4:09 pm #18531
Thank you very much indeed. That’s extremely helpful.
We shall press on!
You must be logged in to reply to this topic.