I am in the process of re-rigging, I would like a one-string setup. I did some calcs and found that:
If I lengthen the forestay by 200mm, I need to shorten the shrouds by 70mm, and the lowers by 46mm.

Now, If the forestay is loaded at 1000N, then the shrouds will each be at 1460N, 2920N the pair. The math got too hectic to calculate the lowers as well. 

If my jib halyard is at 2:1, after the purchase the end moves by -400mm (200mm x 2) and is loaded at -500N (1000N/2).
If my shrouds are at 6:1, after the purchase the end moves by 420mm (70mm x 6) and is also loaded at 487N (2920N/6). 
If my lowers are at 8:1, after the purchase the end moves by 368mm, and is loaded at something fairly small after the 8:1 purchase.

So linking shrouds and lowers to the jib halyard should give me control of rake whilst maintaining rig tension approximately. 

I would propose to control rig tension by taking a bight of the jib haylard via a block which can be moved via a 6:1 purchase to shorten the length of the loop. I'm stuck for ideas on tensioning the lowers

Does this all sound sorta-kinda right? If anybody can offer some insight as to whether this setup will work as I think, or if there is a better way to do it I would be most grateful.

Many thanks in advance.

What boat will you be doing this on?

My advice is to copy a system that works.

If you're not going to link the kicker in then (Which I beleive is unecessary anyway) then you're better off doing the mod i described a couple of years ago and just linking the lowers into the jib halyard. Maintaing rig tension is unecessery because we don't use specific values anyway.

Hi Chris, 

Its my ancient Morrison designed September! Now totally rebuilt, deck-stepped with Chipstow rig and very much stiffened. I should have built a boat from scratch, the only original parts are the hull planks. I currently have no rigging, the world is my oyster, as it were.

I tried to follow your (excellent) article, but without a winder to hand I was missing some info. I havent thought much about the kicker, though if looks easy to link in as the design progresses I probably will.

My effort to maintain rig tension (or match it between shrouds and jib) was so that the "special block" position is not under tension, so that it can be moved without much purchase, i.e would ideally not move under static load with nothing holding it position.

What was the reasoning behind specifically linking the lowers rather than shrouds? I guess this is just the way it is on the standard winder fit-out.

Many thanks for responding to me.

The shrouds are not the critical control. It is the lowers that most often cause problems when raking because the adjustment is so fine and so critical. When you ease the jib halyard you are effectively are moving the rig forward control. When you pull on the shrouds you are effectively pulling the rig back control. obviously this works vice versa.

Hi, I've just completed the conversion according to the excellent article by Chris, and added the cascade 9:1 lowers each side(2:1 behind the kingpost, so 18:1 in total) and it seems to work.  I say that because its not been tried on the water yet, but the relative movements seem just right.  Its on a wooden boat so I could get some pictures for you at the weekend - involves more pulleys near the mast foot, but if you're about to re rig anyway, it may not be too difficult to incorporate.

I did the same as KM on Storm Cloud and it works well.

Thank you gents. Pictures would be great!

How about getting Dave Winder to do an article on one-stringing boats?

He'd probably rather put you in the queue and charge you for it.

Agree with the above, I one-stringed Enchantment with 2:1 on top of jib halyard to the top of the one-string block. Up and down controls are 4:1. Lowers at 9:1 and shrouds at 36:1 (I think).

Three points of note:

1. make sure all the leads, cleats, etc. all run very freely - it is a highly loaded system that needs everything to move in relation to eachother
2. use good quality blocks which make 1. easier to achieve
3. allow for stretch in the dyneema (I used D12) as after a few hours of full load rig tension, this will give a little!

Mags kindly put some pictures on this site of the arrangement we came up with which is basically the standard P&B set-up.

Andy, Thanks for you comments. All noted re lead and friction. 

Its interesting considering a 9:1 on the lowers, this takes the travel to 414mm at the special block, against 420mm on the shrouds, a much better match, I see exactly why this arrangement is preferred.

Its all starting to come together.

On second thoughts it is actually 18:1 as I missed the single block in front of the kingpost - sorry, not got the fine ship here to look at. Given the chance to relook at this, I would also review the strength and length of elastic on the take-aways under the side deck as the up doesn't flow freely when pulling on the down, etc.

We also have a bit of an issue when trying to move on full tension, which indicates that I haven't got it quite right. Then again, we don't really move it during racing anyway!!!

I think it should be 9:1 where it connects to the special block, then a further 2:1 back to the cockpit. 

I'm approaching having a full set of drawings for shrouds, lowers, kicker, rake fwd and back, all backed up with length adjustment and load calcs. Im such a geek. This link might work:
http://www.facebook.com/album.php?aid=150158&id=564343407&l=d1847451d5

Hadnt got to elastic takeaways yet. I think they may be a post test sail job.