I've seen that some of the newer boats have a cascade instead of the previously conventional multi sheave blocks for lowers and shrouds.

What type of 'ratio' should I be looking for for the lowers shrouds and jib,(8:1 - 16:1 - 24:1 ?) and is this easier / neater /lighter with a cascade ?

The trouble with a cascade is building in sufficiant travel for the amount of rake we use. Multi purchases do suffer from more friction.

The shrouds normally run 6:1 a multi purchase under the gunwhale and another muliti purchase 6:1 up the kingpost. 6x6 is 36:1

Lowers always seem over purchased to me but too much is better than not enough. My boat as built had 4:1 under the side deck aith another 4:1 runing up and down between the kingposts. This gives 16:1 which is adequate. Pre one string Winders have an 8:1 cascase and a 4:1 between the posts. 4x8 is a rather excessive 32:1. One string boats have a complicated 9:1 arrangement under the side deck and a simple 2:1 between the posts giving 18:1. I've just done this to my boat and it's fine.

Summing up i don't think you'll get a cascade to work for the shrouds due to travel restrictions. Lowers should be OK though.

Thanks for the comprehensive explanation. 
If I wanted to combine lowers and jib adjustment (in the same way as the 1 string conversion article on the forum)can I assume the jib (6:1 as the article shows I think) would work in the right proportion of movement to the lowers at 18:1? Currently I'm using 4:1 on the jib.
Lastly - puller at 6:1 or 4:1 normally?

Already saved hours of trial and error thanks!

I did that article.

The purchase on the jib is irrelevant, it's the ratio that the jib is pulling the lowers with that's crucial. The rather complicated 9:1 purchase as used on the winder one string is ideal. The 8:1 purchase as posted in the article is adequate.

Having just done my boat with the proper 9:1 arrangement it is a fiddle but once done is better.

Is it expensive to convert this to one string i am tempted to try it on my thin ice but a bit worried that it might cost a fortune. Is there some kind of shopping list?

To do it properly will be expensive, require quite a lot of planning and be quite time consuming.

The partial conversion is very easy on a winder, with other builders it depends what fittings they used. On mine even the partial conversion didn't re use any of them.

Chris's article on one-stringing the jib and lowers is spot on. We did it to out Mk1 Winder and it works a treat. Follow the description to the letter and you will have something that works well for very little cost.

Yes, thanks, re reading the article now I see that the jib ratio doesn't matter. Is it possible that you could post a description of how the 9:1 is achieved - I suspect that many more people than just me would find it usefull, just as the article on the conversion - innovative and practical stuff.

It's not easy to describe, you need to either see it in the flesh or a picture.

I'll be sure to photograph some new 1 string merlins at the next opportunity. It's all been really helpfull

There are 3 new Winder boats photographed in detail in the gallery. This one is the most comprehensive.

Thanks for the link Mags.

From the picture I think I'm seeing a 3:1 on the lowers and I'm assuming on an older boat it needs a 3:1 at the kingpost to operate both 3:1 pulleys inside the decks.  Sounds like a plan.

As lowers mainly counteract bend caused by the kicker, you don't need much purchase on the lowers and you will never have enough purchase to adjust against 1 16:1 kicker full on, so if you are tighting the lowers whists sailing you will normally have to do that with the kicker eased.

Most advice I have had involves tweaking to lowers into position on shore (just snugged, bend looks about right) and unless something drastic (wind strenght wise) happens on the race course don't touch them.

A top flight sailor (I forget who, but at National Champ level) said they have set their lowers once and have never touched them all season.

p.s. that would be on a one-string. Obvioulsy if you rake the mast on a boat where the lowers are not linked to the shrouds then you will have to adjust the lowers, if you don't and have a carbon mast and a powerful kicker you may bend your mast to breaking point.

Sorry to disagree but that's not the case. As you apply more kicker the mast bends (we're ignoring the top section and focusing on gooseneck height for the moment). All the systems have stretch in them so when the kicker tension loads up the lowers (rope cascades mostly) also stretch, hence when it's really breezy and you put more kicker on you also need to put more lowers on. Vice-a-versa, if you let the kicker off you don't need so much lower tension to counter out it's effect and hence should ease them as well.

With regards to the one string effect, because the rig forward/back strings act as your coarse adjustment for the lowers you don't need the same level of adjustment as you used to, it is more a case of fine tuning and the system can be at a higher ratio. With this in mind their is a logic for the lower and kicker ratios to be the same, 16:1 or otherwise.

You're right about breaking carbon twigs with no lowers and too much kicker tension though, leeward mark at Lyme about 6 years ago, the last time Frank ever asked me to crew for him, oops.

So, I'm assuming that a 16:1 on the lowers would give enough extra mechanical advantage to easily pull against the kicker when its on full(without arms like a gorilla) but would be the wrong ratio of movement for the retro fit 1 string system. 
Otherwise, the 9:1 would be a benefit in all but extreme kicker conditions, at which time it would just need about twice as much effort to pull more tension on the lowers (16 vs 9 to 1)?

9:1 is where it links into the lowers. Actual adjustment doubles it to 18:1 (I think it is anyway, I may have to work it out again, but the 9:1 link is definate.). 18:1 is fine, 16:1 as i had mine before seemed stiff but this may have been a friction issue.