2 string to 1 string a couple of questions

05/06/2011 18:11:41
Miles
Just about to change 3646 to one string.

Questions

1. What purchase is generally used to move the 'special block' or equivalent?

2. What purchase for the rig tension and where is the popular place to access it from: either side or middle?

Thanks in advance

Miles

05/06/2011 21:08:33
Chris Martin
The control car for the rake runs off 8:1. 2:1 up and down the posts, 4:1 along the case. This is the same for all boats running one strings. 

Shroud tension is - and always was - 42:1

05/06/2011 21:46:34
Andy Hay - 3626 Business as Usual
Don't forget that there is a 2:1 on the top of the jib, so it works out at 16:1 ratio. There are a couple of non-Winders running with an 8:1 control car (I like that term Chris!), which eliminates the blocks and returns down the side of the case. Think two quadruple blocks linked together.

We had 36:1 on the shrouds on Enchantment when I converted her - 3:1 first purchase, then a 2:1 to the control car with the other tail to a 6:1 along the kingpost. 3 x 2 x 6 = 36. THis seemed to be more than adequate, at the end of the day, this is the same purchase we have on the non-one-string BAU.

http://www.merlinrocket.co.uk/gallery/view_photo.asp?folder=gallery/building_and_repairs/one_string_3386&file=3386_purchases.jpg
06/06/2011 06:59:20
Chris Martin
correct it is 36:1, sorry!

06/06/2011 09:47:42
Miles
Many thanks

Miles

06/06/2011 13:38:41
..
"Since as we increase our rake we need to tighten the lowers the logical strings to link are the jib and lowers." Quote from Library broadsheet re converting to one string.
Whilst I do not doubt this is true, can someone please explain re tightening lowers on increasing rake? Thanks.

06/06/2011 14:41:59
Chris m
Because if you maintain the lowers tension it removes one variable from the procedure. I think they tighten slightly as you rake actually but its very marginal.

07/06/2011 09:30:55
Miles
one last question, how much travel is there in tensioning rig, from no tension to full? I am thinking of using a lever system.

07/06/2011 09:47:26
Andy Hay - 3626 Business as Usual
I bet it won't be your last question .....

I set up our system so that the forestay *just* hooked on - it was a real effort to start with. As the system takes up and stretches a little as the splices bedded in, this became easier, so the stops were adjusted. This then gives you the length of the fine tune travel to achieve your rig tension. In reality, it worked out that when the rig was tensioned up, the fine tune was about half way between the deck and keel. We had the rig tension running up the king post. Since Enchantment was a shallower boat than more modern boats, the fine tune may not need to travel that far.

07/06/2011 11:00:11
ChrisI
Re tightening the lowers when increasing the rake,
Perhpas it's more important to think about slackening the lowers when moving the mast upright? If you didn't let the lowers off you would bend the mast into inversion.
Likewise the puller when raking.
I'm looking at sorting out 'Armed Forces' (3442), but the current purchases have way too much friction. Changing from triple blocks to a cascade system is quite a few pulleys to buy!

07/06/2011 19:13:43
..
Re :"Tightening lowers as you increase rake".
Thanks to those who have replied. Clearly, as you increase rake, the lowers tighten at least a bit, but the quote was the NEED to tighten, implying that having increased the rake, you then tighten the lowers. Why? If you reduce rake, lowers slacken obviously, presumably you then tighten lowers consistent with desired amount of pre-bend, or holding atraight mast if desired. If you increase rake on the other hand, presumably because it is windy, wouldn't you want some looseness in the lowers to allow mast bend, to open the mainsail leech to depower? Or have I got it wrong?

07/06/2011 19:48:07
Andy Hay - 3626 Business as Usual
I cannot recall exactly, but I have the feeling that on Enchantment, the geometry slackened the lowers as the rake was increased. This did give some interesting issues on the full upright setting.

The thing to remember is that the rake control is quite a course adjuster, the ratios are geared towards something near, but not necessarily eactly the right one. After all that is why we still end up with a fine tune for each control.

You can move the mast back and fro rapidly, then you may have to tweak one other string - lowers, say. This is still much better than letting off the forestay, pulling on the coarse rig, lowers, fine rig, kicker, etc. all at the same time, whilst trying to steer. Jeepers, I have enough trouble with the mainsheet and the tiller!

07/06/2011 21:11:21
Chris Martin
Having the lowers tighten as you rake automatically means you have accurate calibration of where they are set. X lowers at 6 inches rake is still X lowers at 40 inches. If you want to ease them, let the string off a bit. the previous setting is easily repeatable if you think it isn't working.

It avoids needing marks for every rake setting, and you know precisely where you are at a glance. Before the one string conversion on my boat(s) the lowers just lived on the calibration mark for a given rake and were never really adjusted. Now I use them quite a lot, albeit in very small increments.

This has in some ways de-skilled the boats, but interestingly all the guys at the front use a one string whether they need one or not. As has been said already it's not so much raking that it makes easier, but pulling the mast back up you needed to uncleat shrouds, lowers and kicker and haul on the jib before setting everything else to suit. Now, just uncleat RB, haul on RF and then let the kicker off a bit.

10/06/2011 18:27:02
Miles
Well, I'll be .... It actually works, and less string than I had before!

Rig tension increases slightly as you rake back.

That last question.

The rig tension, where is best place to have it cleated? Just one on c/b case or either side with rest of controls?

10/06/2011 19:46:03
JC
I have had both.  My first one string boat "Snorter" 3627 had one rig tension cleat on the c/b case.  My current boat has it led to both sides.  Not much to choose, although on balance I would have the latter as you can tweak the rig tension while sitting out.

10/06/2011 21:21:27
Ben 3634
Gotta be out to each side.

10/06/2011 21:22:48
Chris Martin
It's less critical with a one string, but one control in the centre means twice as much rope in the middle of thr boat.

10/06/2011 21:39:37
Miles
sides it is.

REPLY

Your Name
YouTube Clip
Paste the link provided by youtube under the "Share" button, looks like this "http://www.youtube.com/embed/XEsrho3jqbo"
REPLY
Type a Number under 43: