Please can some one explain the benifits of a one string raking system and how it works used to own a Vintage Merlin, But went and got an N12, and was wondering if this system could be of use for a N12.
Cheers
James

Tom Stewart is your man, as he sails both Merlins and N12s. I believe he told me the "one string" system is not used on 12s as they like to control their shrouds seperately (they let the leeward one off much more?).

The benefits of the system are that a single string can be pulled to rake the rig back (or another can pull it forward) and this adjusts the jib tension, shrouds, lowers, puller and kicker all at once, to keep the same tensions as the mast moves.

Used to be called the Western Differential System on FDs. The line let off the jib halyard - dropping the mast aft and tightened shrounds via Soling kicker winches. This eased the genoa leech tension to a puff and if more was required the plate could be lifted. I can remember standing on the side of an FD when the enthustic owner hauled the lot down too hard and split the hog from the hull. Ex Hornet champ & insurance person. Alas won't help him now. 

Not strictly Merlin but it's all be done before.

RE:>>what are the benifits of a one string raking system 

It was explained to me as:
As the wind picks up and you feel yourself getting over-powered, then you:
 - let the puller off
 - let the jib halyard off (more than is required)
 - tghten up on the shrouds
 - tighten up on the lowers
 - tighten up the jib halyard to maintain the correct tension
 - tighten up on the kicker.
And you do that while controlling the boat in the race, over the waves, and before the wind drops again! You also have to do it around the windward mark, and reverse the process around the leeward mark - just when your crew is hoisting and dropping the kite.

Alternatively, you undo the rope saying "rig forward" and pull in on the rope saying "rig back" - and thats it.

And, as Andy our club chandler is looking over my shoulder, one other benefit for him is that you have to buy all that extra dyneema string!

At Minima Y C in the 50s there was some talk about altering mast rake during a race. At the time most masts were deck stepped so it should have been possible with a Merlin but I'm not aware of anyone who tried it. Nevertheless I sailed most of a Cadet Week at Burnham with the jib halyard loose enough for the leeward shroud to be flapping around when I pulled the mast back with the mainsheet on the beats. I raked the mast forward on the runs by twisting the halyard round one of the spinnaker boom eyes on the mast. The differences in early Cadet performances were probably due as much to variations in the hull shapes as anything else so it's impossible to assess whether my idea worked or not.

By the time I moved to Merlins most masts were hog stepped which would have made changing rake during a race difficult if not impossible.

Robert
I heard of but never saw Brian Saffery-Coopers "Buccaneer" that Brian fitted a winch on the foredeck with two sized drums for doing just that, The with keelsteped masts Robin Judah had highfield levers on his MR's that he let go downwing in the lighter stuff, I fitted am under-foredeck slide thing that the shrouds led to worked well untill the rig disapeared over the bow at Whitstable week. On Flowerchild I used to use the Proctor shroud levers to let the mast go fwd which is almost certainly why I broke so many masts in 1968 untill Tim Hockin came up with a solution of sleeving the mast a Proctor D with C section.

Robert, 

I think it's much easier to play games with a hog stepped mast. The whole thing is much more controllable and predictable and doesn't fall over the side if you get it wrong. 

Bearing in mind one objective of dropping the mast aft is to control foresail leech tension - a similar effect can be more cheaply achieved by moving the jib sheeting height - in classes where that's allowed. Tuning loops go round and round....

Jamie. Nice to hear from you.

When I wrote that I was unaware of anybody trying to alter mast rake with the early deck stepped masts I suggest that it could have been done by easing the jib halyard on the beat like I did in my Cadet. Despite what Jamie writes as far as I know few people tried variable mast raking with hog stepped masts and as Ancient Greek points out it can lead to lots of broken masts! 'Buccaneer' probably had a deck stepped mast but she'd been so extensively modified that I'm not certain, anyway I don't remember the winches, Mike Ligget might. I don't know about Robin Judah's efforts, I crewed him in 'Mint Julep' no. 599 which had a very bendy mast which rotated in a turntable at deck level. No chance of changing the rake with that contraption.

I've also been thinking about putting a one string raking system on my National 12 recently. I sail at a restricted venue where most races consist of beating and running legs with little in the way of reaching. A system that allows me to easily and rapidly move the rig from raked to upright at the windward mark and vice versa at the leeward mark might be beneficial. Does anyone have a schematic diagram of the one string rig used on a Merlin that they would be prepared to let me have a copy of? Thanks, Marcus

See my point #2 at the top. I assume you N12 guys like to have the leeward shroud really loose in order to square off the boom, so the exact way we thread the knitting on a MR won't be useful?

Thanks for the response. You're quite right that in the 12 the standard practice is to release the tension in the leeward shroud to enable the boom to be squared off more when sailing offwind. However, I've been thinking about a system that enables the rig to be moved from the upwind raked position to a more upright downwind position and then has a fine tune arrangement to release the leeward shroud as required. I'm assuming that in the Merlin one string system the special block somehow connects the jib luff tensioning purchase system to the shroud tensioning system and that rake alteration is then achieved by moving this special block around; one string to move the special block one way to increase rake and one string to move it the other way and reduce rake. I'm also assuming that in the Merlin both shroud purchase systems are connected together before the special block so that equal tension is maintained within them throughout rake adjustment. If, however, the shrouds can be connected independently to the special block then surely it should still be possible to adjust them independently? Also, if my assumption about the role of the special block is correct then the purchase ratios of the jib luff and shroud tensioning systems is quite critical; what are these, and what are the purchase ratios on the rig forward and rig back strings? Thanks again, Marcus

You got the principle right. The shrouds on a new boat system run 3:1 then 2:1. This latter purchase splits the shrouds to either the "one string" or a 6:1 fine tune. I guess that it could be possible to individually adjust the anchorage for the 3:1 or somewhere else.

I suppose you could rig the MR system, but incorporate a lever (so 1980s!) to cast off the leeward shroud on a run.

Here's a photo of the 'special block'. Hasn't anyone given it a better name yet?

Thanks again for the comments. I've had a look at the photos of the special blocks on both 3386 and 3683. From the photo of the block on 3386 in particular it appears that the static ends of the shroud purchases which would conventionally be attached to a fixed point in boat are actually lead to the lower part of the block while the static end of the jib halyard purchase is lead to the upper part of the block. Moving the block around therefore adjusts the jib halyard and shrouds simultaneously. However, are the purchase ratios on the shrouds and jib halyard irrelevant? Imagine a setup in which the shrouds and jib halyard are lead directly to the block with no intermediate purchases and assume that the setup can be tensioned to the required load. At the special block the force from the jib halyard would have to balance the combined forces from the shrouds; in other words the individual shroud tension would be half the jib halyard tension. Also, as the special block moves up one unit and the rig moves back the shrouds terminals would come down one unit at deck level. This doesn't seem quite right, is there some subtlety I'm missing? Is part of the overall purchase in the shroud tensioning system actually attached to a fixed point in the boat rather than the special block?

A few other thoughts that have occurred to me in adapting the system for a National 12:-
i) Presumably the static ends of each shroud purchase system can be lead to the special block independently of each other to enable the shrouds to be controlled separately. I guess the key to this is to ensure that the lines from the shrouds are concurrent and aligned with the line from the jib halyard so that the orientation of the block will remain unaltered if the tension in one of the shrouds is released.
ii) In my boat the mast is not deck stepped but neither is it hog stepped. It's actually stepped at centreboard capping height approximately midway between the hog and the shearline. Since the kicking strap attaches to the mast step I'm assuming that as the rake of the rig is altered the tension in it will remain approximately constant and therefore there's no need to incorporate the kicker into the one string system.
iii) As the rig is raked aft the spreader tips will move backwards relative to any fixed point in the boat. Thus the shrouds will be deflected backwards more and the compressive forces in the spreaders will increase. The forward component of these compressive forces will therefore tend to bend the mast more. This increase in mast bend with rake will occur no matter what the position of the mast foot is. Is this correct? I know there's been some discussion of this on the forum but there didn't seem to be a consensus.
iv) Finally, the photos of the special blocks suggest that the rig forward and rig back control lines are on a simple 2:1 purchase. Therefore I'm assuming that it doesn't take that much force to move the rig around. Could one of the control lines therefore be replaced with a bungee system that tends to pull the rig in one direction. For example, if such a system were connected to the bottom of the special block then the rig would automatically be pulled forward upon release of the rig back control line. To move the rig back again one would simply pull on the control line once more and the system would be genuinely one stringed. Would this work?

Sorry for asking all these questions on the MR forum but there doesn't appear to be any experience of one string systems in the 12 class so I appreciate the inter class collaboration! Thanks again, Marcus

Having put the system on 3386 and planning an adaption for 3626, I went through all this some time ago!!

There is a 2:1 block on the top of the jib prior to the hook on the halyard. The shrouds (and lowers) are attached at the bottom of the one string block. So if you move the one string block, this will have the effect of moving the jib luff at a ratio of 2:1, the shrouds by 6:1 and the lowers by 9:1. The dead ends of the lowers & shrouds are the led to the tensioning system. The ratios are critical so that the whole rig moves as one. Depending upon geometery, you may need to adjust the ratios. I tended to pre-tension the entire system so that I could JUST get the jib halyard on the hook. 3386 was quite shallow so I did not have a great deal of shroud travel to play with. 3626 should be better.

The one string block is 2:1 at the block itself, with a 4:1 down the side of the centrecase. This is effectively a 16:1 on the jib luff. You will need this. We also link in the puller (on 6:1 to the top of the one string block) and a part of the kicker (to the bottom of the one string block). 

I am planning to make the one string block an 8:1 (i.e. a quadruple) block on 3626 to remove the need for the doubles along the case sides. This is a slightly more complex solution, but for me with a stock of old wire blocks, is cheaper.

You will probably need the purchase to overcome the friction in the system. I would urge extreme caution about having any bungee in the system. We tend to move the mast aft in a series of increments so we would need control of the aft movement and then we need to "pull" the mast back upright. Give it a go with elastic, but you might not like the results.

From memory, the spreaders are less effective and important on a one string rig. We tend to set them up for the upright case and then ignore them after that. More rake & more bend in strong winds is generally what you are after. With the ratios above, you sometimes notice that the lowers slacken off as rake increases, also giving more bend.

I am not sure whether a hog or case stepped boat has been converted. We one stringed 3386 AFTER we deck stepped her.

Speaking to the man in the Essex shed, he complains that the one-string is actually 2-string (backwards and forwards). So Jacko has adapted his versoin to be one string - which pulls the rig back and when you let it off the whole rig moves forward on its own... 
I am sure he would be happy to talk about it, or sell you a mast to make it work!

RE N12 sailing. Kevin Bloor has a Final Chapter that has both systems.ie let both shrouds off together or just one.