Tagged: Thank you Oliver and Steve.
04/09/2014 at 2:28 pm #5005[email protected]Participant
I’m preparing a boat for the Southport 24 hour race, she’s a woody (6281), and still aft main.
I’m tempted to leave her as is but as most crews will be more used to centre main techniques, I ‘m considering converting.
There is a wire horse, approx. 24″ at present. I’m thinking it kinder on the centre board casing to use the horse and a block, running the sheet forward to another block then down to a main sheet block on the centre board case.
I’ve seen the split tailed main sheet, is that necessary?
If I stick with aft main, does a ratchet block help with heavy loads?
Any advice welcome, thank you.
09/09/2014 at 3:43 pm #5024Oliver ShawModerator
One of the key advantages of the split tail arrangement is that it effectively takes the sheeting load from the windward quarter; thus when close hauled the horizontal component of the sheeting angle is optimised, with the result that for a given boom position the load on the sheet (and thus the load that you have to hold in) is reduced. No other sheeting arrangement possess this benefit. Coupled with that, if you prefer the sheet led to the centre (and most racers do prefer that) the split tail arrangement is surely the one to go for. I personally happen to prefer transom sheeting for other reasons, but then I very rarely race; as I understand it, both as a sailor and as a physicist, the above is one of the key benefits of the split tail arrangement.
However that considers only the horizontal component of the sheeting angle, and there is also a vertical component. The modern rig, with modern spars and a massive purchase on the kicker, controls the vertical position of the boom entirely with the kicker. That is fine, and modern kickers on modern spars are fully capable of bending the spars (which are specifically designed to accept this), and the kicker can then do a very good job of flattening and depowering the sail in stronger winds.
That option may not be available with older spars such as you have, which were designed to remain straight, and which even when new were probably not as strong as today’s spars, and which are likely by now to have also suffered weakening due to corrosion, plus perhaps multiple holes having been drilled over the years, plus perhaps cracks. So if you apply modern kicker loads to 1970s spars there is a real risk that you may find that you end up breaking the boom, or (perhaps less likely) the mast.
Before the days of modern 16:1 or 18:1 kickers and bendy spars, kickers typically had just 2:1 or 3:1 purchase; 4:1 was unusual. Kickers were intended primarily to prevent the boom lifting when off the wind, rather than as a means of flattening the sail even when going to windward. Sails were flattened in stronger winds by (in part) applying mainsheet tension vertically downwards to the leeward quarter. The full width horse was developed to facilitate this; a traveller rode on the horse, with its travel being limited by (adjustable) control lines. In lighter winds the traveller was kept in the centre, but in a real blow it was allowed right out, so that the sheet could then pull down vertically and so help to flatten the sail even while spilling wind.
I suggest that you need to consider your sheeting arrangements and your kicker purchase together, and consider also the age of your spars. If I were preparing this particular boat for serious racing I think I would probably either go for modern spars (even if they are borrowed for the occasion) with modern kicker and split tail mainsheet, or alternatively go for your present spars, with a 3:1 or possibly 4:1 kicker, and transom sheeting with full width (rigid) horse and control lines. Avoid the rope horse; “neither fish nor foul nor good red herring”, and amongst its several shortcomings is that it allows the lower block to bash the deck.
Yes to a ratchet block.
Hope this helps,
09/09/2014 at 8:18 pm #5025steve13003Participant
Hi, I would echo Oliver’s warning about the strength of your spars, the boom in particular will not be strong enough if it is one of the old IYE gold round ones. If you add a bracket for a centre main block this will weaken the boom and if you have a windy race it will end up as a V. The main sheet needs to be a split tail with each side tied to an eye on each quarter. The main part then runs along the boom and down to a block and cleat mounted as high as is legal on the back of the centre board casing, make sure the mounting pillar is very strong, the swivel mounted block and jamb cleat will not be cheap unless you can find a used one for sale or gifted!.
re your previous post about the spinaker pole system , sounds a mesh that needs to be scrapped. A simple double ended pole with an eye on the front of the mast with an up haul to a turning block about half way up to the shroud plate then down to a cleat on the cockpit edge would work, with a down haul to a hole just in front of the mast to a cleat under the cockpit edge. I would use a hook at the join between the up and down parts with an eye on the pole, all the slack is in the down haul and being rigid the height of the pole is fixed when the spiny is up.
good luck. Steve Corbet
11/09/2014 at 9:37 pm #5038[email protected]Participant
Thank you Oliver and Steve,
All points duly noted, especially regarding the weak boom masquerading as a very tough looking spar!
We’ve set up the kite as designed now, so we’ll see how she performs. A dipping pole on a dinghy is novel to me!
I’ll update you after the event.
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