Can anyone help me with an idea of how much the shrouds move when raking a deck-stepped mast? I'm nearing completion of the redecking and restoration of my NSM 2 (3285) and wish to assess where to run the various sections of the purchase systems within the various spaces I have available. For instance, if the shrouds only move 60mm I have enough height in the kingpost; if they move more I shall have to arrange a cascade along the centreboard case, etc. etc! I shall have the same dilemma with the lowers but would guess that they move less? Any help gratefully appreciated.
Posted: 05/07/2006 09:50:51
They don't move very far, although did you mean 60 mm or 60cm, as I don't think 60 mm is enough for the shrouds, I would guess closer to 15-20cm. Most boats have the shroud/lowers pulleys on the frame that runs up in front of the tank and then up/down the king post.
Posted: 05/07/2006 12:22:26
By: Alan F
Thanks Alan - Yes I did mean 60mm (2.3 inches?). 20cm is about 8 inches in old money - do the shrouds really get shortened by that much? My problem is the space up/down the kingpost as, although the layout of the boat is very similar to your linked photo with the centreboard case running full-height up to the tank bulkhead, my kingpost seems much shorter than the one in the photo. This means I have only about 180mm (7 inches) travel at the kingpost. This in turn means I need to be careful about the amount of purchase I use where the shrouds come through the side deck. My thinking was this: if the shrouds only needed to move 60mm, I could put a 3:1 along the tank frame, a 6:1 up the king post and a 2:1 along the centreboard case, making 36:1 in total (but it all depends on the throw of the shrouds or I shall run out of movement at the kingpost - sigh!!)
Posted: 05/07/2006 13:07:33
I am sure they don't move a whole 8 inches, but 2.3 doesn't sound enough. Put it this way, with 4 to 1 and a full height king post can only just get the tension on when fully raked. Some basic school boy maths could approximate but invloves tans and cosine and stuff that I have long forgotten
Posted: 05/07/2006 13:48:44
By: Alan F
I was going to post something here but realised that what you actually need is the true figure from someone who has gone and measured his/her boat and a guess isn't good enough. My guess FWIW is about 3 inches in old money, will measure at weekend if you have no better answers
Posted: 05/07/2006 16:19:12
By: Andrew M
I think he means the actual shroud itself moving 60mm before any pullies.
Posted: 05/07/2006 16:22:56
You're absolutely correct. I would be very grateful if someone could measure next time they rig their boat, and yes I DO mean how much the shroud moves before any pulleys (in other words how much of the shroud disappears down through the side deck!). This information would enable me to design the pulley system to fit the space and still have about 36:1 which is what I see on most boats.
Posted: 05/07/2006 18:25:16
Not sure if this helps but on my Tales (3489), I have a coarse adjustment and a separate fine adjustment that both work on the same set of purchases. If you look at this link (and ignore the fact that it is talking about spinnaker setup), you can see the fine adjustment as white stringed Y running down kingpost and then to purchases under shrouds while the coarse adjustment can just be seen running from these purchases horizontally along tank top (just above thwart in pic) - they then go around a pulley on tank top and back along centreboard casing.
Posted: 05/07/2006 18:25:37
Movement at the shrouds equates to rake.
Posted: 07/07/2006 08:29:08
By: The Old Trout
While I think about it, Lowers:
Posted: 07/07/2006 08:35:37
By: The Old Trout
Thanks Old Trout! Some useful thoughts there.
Posted: 07/07/2006 10:43:59