Topic : shroud tension

I currently have a smokeres satisfaction with a set of leavers on the shroud to change the tension. I'm thinking of changing this to a fully adjustable system with the use of pulleys. any one have a tried and tested method of improvement. Is it worth making the change?

Posted: 19/02/2005 13:34:56
By: Mike Casey
Hi i've got an NSM1 again fitted with quadrent levers whilst they work ok they don't allow for easy adjustment when sailing and I'm just about to change them. luckily I've got a pair of 15" harken 8-1 mussle boxes (not sold any more) Nowadays as your probably aware boats are rigged with good quality Harken/ronstan bb blocks take a look at Full Force boats webb sight if you can't get near a modern boat. to oppose these you have to fit a similar multiblock system on the jib halliard, I'm leading these back to cleats each side the C/B case just astern of the main thwart. this is the basic system we used on 505's & works well .
Might be worth a call to Winders who have a single line system, but might be a touch more complicated.
I assume you also still have a mast strut which is fine if you have enough adjusment. Using harken quad blocks I priced it all up at around £240.00 inc cleats. Hope that hasn't put you off, regards Barry.

Posted: 19/02/2005 16:57:31
By: Barry Watkin
I think you guys should be careful.
I remember sailing boats with quadrant levers - I always set them one notch down from the top in case we put too much tension on and broke something.
On special occasions we would wind it up to the 'top notch'. Nothing ever broke but we always went upwind with the leeward shroud slack. I guess the hulls just are'nt stiff enough.
The real big plus was to let the leeward one go on the run in light/moderate weather - then you could really square the boom away.
If we wanted to change the rig tension the crew would go down to leeward just before we tacked so the new windward shroud was set - it only took a couple of seconds.

Posted: 19/02/2005 17:46:47
By: Pat Blake
thanks for your help. will keep this system till the eend of this season and then have a look when i have some more ideas together.

Posted: 19/02/2005 19:40:26
By: Mike Casey
Thanks Pat point taken, I don't intend to inflict the kind of tension that you guys are puting on your newer machines, carbon decks,bulkheads et all. Thanks again Barry.

Posted: 21/02/2005 07:18:45
By: Barry Watkin

I had an NSM1 Omega (3227) until last year and that had quadrant levers plus a muscle box on the jib. As she had a low bow tank, you could tension up the shrouds by using a combination of the levers (set first) and then the muscle box: did not encounter problems with lee shroud slackening off.

In our early days, we tried Pat's method of making crew tighten up leeward lever on a tack but as we tack a lot at Banbury, this was not practical. Usually, we simply set up the shroud tension and rake before we launched and did not change on the water.

If your boat does not have a low bow tank, then I would be very cautious about putting tension on.

Posted: 24/02/2005 10:40:51
By: RichardT
OK dumb question.

After reading this and other threads regarding masts, stiffnes etc, can somebody now tell me what the difference is between a high and low bow tank?


Posted: 24/02/2005 12:19:57
By: Willing to Learn
one is high and one is low

Posted: 24/02/2005 12:26:19
By: joker
The high tank was just that, pretty high but quite far forward in the front of the boat. If using a bigger spinnaker, it is virtually impossible to get the spinnaker down through the chute. The low tank comes more into the boat on the same level as the plate case. I THINK that it also helped to stiffen up the boat a bit near the shrouds.

Posted: 24/02/2005 13:06:48
By: Oldie
Old 'high' tanks were quite short, and there was a significant gap in front of the mast heel. New 'low' tanks (after 32xx?) come almost all the way back to the mast foot, and are only 10 inches high(?) or so. This acts as a brace to stiffen the hull at this point.

Posted: 24/02/2005 13:34:09
By: Mags
Heres a high tank!

Posted: 24/02/2005 15:56:13
By: Mags
The low tank was approved at the same time as the neccessary rule changes to allow building hulls in sandwich GRP construction, which I believe to be 1980, about no. 3230.  Because the angled aft faces of the tank run roughly along the line from shroud attachment to mast base they assist greatly in resisting the forces from the rig, stiffening the hull under rig tension

Posted: 24/02/2005 16:38:28
By: Anorak
Mags picture also shows quadrant levers when they were introduced -1966- We were able to adjust even the windward one in a blow but rigs have got a lot more powerful. PB is right about care they are powerful we used to let both windward and leewrd off down wind in up to force 3 after that sense prevailed.

Posted: 24/02/2005 19:15:22
By: Harold G Twincy
How easy is it to incorporate a tank into a boat  which currently only has a bag

Posted: 24/02/2005 19:27:09
By: Rousey
Easy; as long as you can glass it in and don't suffer from resin fumes and claustrophobia the top is tricky but doable.

Posted: 24/02/2005 19:41:09
By: Been there and did it in 1966

Do you have any other links or photo's of older boats, especially running rigging, It would help when I come to rig mine.


Posted: 24/02/2005 21:40:55
By: Steve
Richard T, Thanks my 3236 is I suspect identical to you old Rowsell omega (funny that) and I agree I've not had any problem keeping that leeward shroud tight, I'am in the process of building a carbon rig and am therefore taking the opertunity of modernising the shroud/forestay control which work fine but lack enough tolerance/finesse to really crank the rig back, plus I like fiddling!

Posted: 24/02/2005 23:13:59
By: Barry Watkin
Just in the process of doing up 3165 "panatella", I'm interested in Oldie's comment that a high tank makes it impossible to have a modern size kite. Is this correct in everyone's opinion, or not? If so, I may have to modify the boat, but would like to keep her as original as poss, i.e. I don't want to deck step her etc.

Posted: 25/02/2005 09:00:15
By: BmaxRog
I very much doubt the scale of the changes in kite size has made it impossible to get the kite above a high tank.  After all, look at the size of the hole in the foredeck you are pulling it through

Posted: 25/02/2005 09:29:53
By: AndrewM
That stirred up a lot of activity!

On 3227, the low bow tank came right back to just in front where the mast was stepped which was on an extension to the front of the centreboard case and this was built in to the end of the tank if that makes sense. Made the hull structurally very strong and able to take quite a lot of rig tension.

If the crew cannot get the kite through the hole, change the crew - cheaper than changing the kite!

Posted: 25/02/2005 10:31:58
By: RichardT
You sir are in danger of causing a crews STRIKE
crews are 50% of the effort you can't race without them and a bad crew is a poor excuse! Some are very pretty too.
Instead line the hole with a very thin skin of PTFE or spray on "Fluroglide" a dry lunbricant of PTFE powder.
By the way isn't it amazing how subjects ramble along, my Tutor at Cambridge would have approved. This is an informative and funny forum, if only my own class did the same. It also lets people get things off their chest, I used to race M/R's but grew out of them, I wonder if I should build another or buy one, if so, what boat should I get? It would be new money not a problem but time is, fast delivery would be required, MR regattas seem to fit well with my proper boats programme this year, 15 stones helm I'd need to find a fit young crew though and 3 wives down I don't think she'd better be a girl! The present one would NOT understand the inevitable intimacy (No man or woman has secrets from their crews.)To paraphrase Dr Johnson.

Posted: 25/02/2005 10:49:20
By: Convener Crews Union but an owner driver
I suspect not such an issue for Smokers and NSMs. However, definately a problem for high bow tanks in the late Proctor designs. I know of one boat (a 9b)which can only use an old,old type spinnaker because there isn't enough of a gap. I have suggested that the owner takes out the bow tank and replaces with a bow bag. Quite reasonably, he's a bit worried that removing the bow tank might affect the stiffness.

Posted: 25/02/2005 11:25:45
By: Oldie
I suspect not such an issue for Smokers and NSMs. However, definately a problem for high bow tanks in the late Proctor designs. I know of one boat (a 9b)which can only use an old,old type spinnaker because there isn't enough of a gap. I have suggested that the owner takes out the bow tank and replaces with a bow bag. Quite reasonably, he's a bit worried that removing the bow tank might affect the stiffness.

Posted: 25/02/2005 11:27:02
By: Oldie
Ooops! Sorry for the double post.

Posted: 25/02/2005 11:28:18
By: Oldie
Bmax Rog', If all else fails whats to stop you using bags to store & hoist from like a 420 or 470. I having checked the rules but on an elderly boat it would hardly be the end of the world, Barry.

Posted: 25/02/2005 12:52:20
By: Barry Watkin
Well, nothing really, but it did seem a bit unlikely to me-it's not as though you're trying to fit a 505 kite through it! As someone above has said, a bit of lubricant goes a long way(ooh, matron!)and the rather rope worn and varnishless chute mouth is going to be restored in full. I can see how a very old narrow bowed boat could have probs...

Posted: 25/02/2005 13:48:00
By: BmaxRog
If you can fit a Pahimina scarf through a wedding ring then......................

Posted: 25/02/2005 13:59:05
By: Raj from Bombay
new rules scarf though?

Posted: 25/02/2005 15:18:23
By: just a thought
I don't know whether or not you can get a new rules kite through the gap, but if it is as difficult as some of you are suggesting then it can't be very good for them.  Kites get the finish scraped off and creased frighteningly quickly on new boats with larger chutes and a low tank.  I wouldn't have any hesitation for moving to bags on both sides - we considered it for our new boat, but then got scared...

Posted: 01/03/2005 13:14:44
By: Chris D
What are you making spinnakers out of Boiler plate YT Cloth?

Posted: 01/03/2005 18:07:58
I think the differance with a low tank is the angle of drop is much less sharp.

Some of the high tanks are seriously high and the kite will be turning through 90 degrees over about 6 or 8 inches. This is not really very good!

Chutes are unkind to spinnakers at the best of times, but i wouldn't fancy a bag launch in a merlin !


1) Are you handicap racing at the club with no ambitions of opens? If so why bother buying a full size spinny?? Provided the club will use the PY adjustments the boat will be just as competetive with the old sizes. I think the longer poles are essential equipment though.

Obtaining a decent old size should be easy - people have probbaly got them stuffed in garages, and sailmakers will almost certainly still have the patterns.

2) You are allowed a double downhaul patch on a merlin spinny, but part of me says this might help and part of me says it won't. I suspect if anything it will add to the friction, but it will come down faster with King Kong crewing.

Cant really thing of anything else

Posted: 01/03/2005 19:22:36
By: Chris M
Bag launching was and is easy! 
I wouldn't want to go back to it though.
However spinnaker don't last very long for any number of reasons not least they are very thin!

Posted: 01/03/2005 20:01:48
X sailmaker part of me just shuddered don't try twin downaul loops, think of it the sail bunches around this system bringing twice as much cloth into the mouth, This only works on dinghies with large chutes 505's etc. The bigger new sail wont give any differance again think logically all you will be doing is pulling in for a second or two longer as the measurment from patch to corners is greater. the friction you gain through the mouth is constant.Your best bet is to order a new sail made from a 'silicon' coated cloth, Dynalite being the current favorite. Barry

Posted: 01/03/2005 20:34:18
By: Barry Watkin
Barry's right buy new buy silicone coated buy often.

Posted: 02/03/2005 07:43:32


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