Rig Tension, A word of caution.

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a little slack in the leewards at F4ish.

[/ QUOTE ] That is suggested in the Selden guide also. They mention an angle of heel at which the leeward shrouds to go slack. If they dont then they are too tight.
 
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Fairpoint...however, isn't this more down to poor design or weak yacht build? Rather than Cruiser or racer set-up.

Ie. Jeanneau should make stronger bulkheads.

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Any boat literally can be overstressed by rigging such that dorrs and ports get stuck, compression of cabin roofs etc. It is not poor design - it is purewly overstressing the structure by too much tension.

My 75' built Motor Sailer - built like proverbial sh**house tank ... I can seize my bog door easily by overzealous rig tension. I don't use gauges now - I go by feel, using main halyard to check mast is true vertical and then sail the boat and watch the stays / shrouds on each direction of sailing. Adjust as necessary.
 
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Why is it so bad to have lee shrouds slack when driving hard on the wind?

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Because the lee shrouds (and spreaders) locate the mast laterally. If there is no restraint on the mast, it is more easily pushed out of column if the boat slams into a wave or whatever. This does not really apply on a rig with fore and aft lowers though. Or a mast that is designed to exist happily without such support.
Rigs can look very similar but actually be designed quite differently I suspect! As an extreme case, the 505 dinghy can have stiff or bendy rigs set up extremely differently, within one design rules, (at least) two distinct schools of thought!

Why do we get so little information with our boats?
 
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I used to sail with a man who wrote a book about this. He never used a tension gauge, but we'd spend hours at the start of each season beating, tacking, beating, tacking while he looked at the mast, and tweaked bottle screws. His priority was to get the mast the shape he wanted, and it was that which determined the tension in the standing rigging, not some gizmo. We won plenty of races, so I guess he knew what he was talking about. Either that, or it was my trimming.

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I'm with you on this. I had a series of articles from I think Hood via YM from years back that explained the principles of rig set up and have applied this ever since, in my case always on masthead rigged boats. We re-rigged our current Jeanneau Sun Legende and again I set it up initially using the same method, followed by fine tuning on the water. Our sailmaker, also our rigger in this instance, did the final on board under sail check for us to confirm all was correct. Our boat is very similar to the OP's and we too have 10mm caps, fore and back stays and lowers, with 8mm intermediates. We also have a powerful backstay adjuster. However we do not have slack lee shrouds waving around nor do we have trouble with doors opening below! What the tension figures are I have no idea, but they were set up using normal hand tools and not by a candidate for Britain's strongest man!

I too see no reason to over specify rig wire sizes as to achieve the desired tension the loads will be much higher. As someone else has mentioned the wire itself is not the weakest point because that is the terminations, so no advantage to going up a size unnecessarily
 
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Any boat literally can be overstressed by rigging such that dorrs and ports get stuck, compression of cabin roofs etc. It is not poor design - it is purewly overstressing the structure by too much tension.



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There are well designed continental boats which dont put the rig load through the hull but into a steel frame so you can crank the tightness up properly. And it does matter that the lee shrouds dont go slack because that means excessive mast bending which in turn means alterations to the sail shapes and the angle of attack at different heights up the forestay. In effect, thats the reason why boats with unbstayed masts dont go so well to windward.

If Normans 10% is right for his 45 footer then that suggests the boat could have been rigged with 8mm wire at some saving to weight aloft and cost. No doubt this comes about from a short mast / low sail area combined with a degree of tenderness. The Selden design for my mast takes the GZ curve and sail area as starting points for the rig size calculations.
 
Fine if you have keel-stepped and the framing to take it. But even then your fittings are often to hull and not to any metalwork to absorb the tension ....

A deck-stepped mast as I have and many others ... my race boat was deck-stepped even ... that is a different proposition altogether and rarely do you have such framework to absorb over-tension.

The thread is a little misleading because there is no indication of deck-stepped or keel-stepped other than odd references to a particular boat marque. And like many threads on these fora - too many generalisations without specific boat detail.
 
This is where we have a conflict between the practical clan and theoretical clan as this point can be reached under different conditions on different boats although they may all have received the same pretension! Each hull/superstructure will have differing amounts of deformation.

I have seen the cabin top plus a mast prop deformed on a Centaur due to excessive tension and similar on an older Nauticat. Beware the theoretical figures they could harm your boat.
 
I have seen no mention in this thread of the danger (on a mast head rig) of slack lowers. I understand that many lowers failures are due to the pumping action between loose and tight, which rapidy causes failure on this type of rig. The correct tension is that in a head sea and heeling, you see no obvious take up of slack in the lowers.

According to Westerly Owners association - this has been one of the major causes of mast failure, and (surprisingly) not because of the failure of the uppers. Westerly do have one or 2 sillies in their design of the lower attachements using ubolts which are not in line with their stress point. - I have to attend to mine at the end of this season as a precaution.
 
We have both fore and aft lowers on our Jeanneau and no pumping is ever noticeable, again the lee side lowers don't go floppy at sea under load. In addition we have if we wish an additional removeable inner forestay to the upper spreaders backed up by running backstays. This extra stay is for either storm jib or staysail but is non standard but in practice the masthead rig has proven very stable as standard supply.
 
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We have both fore and aft lowers on our Jeanneau and no pumping is ever noticeable, again the lee side lowers don't go floppy at sea under load. In addition we have if we wish an additional removeable inner forestay to the upper spreaders backed up by running backstays. This extra stay is for either storm jib or staysail but is non standard but in practice the masthead rig has proven very stable as standard supply.

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Robin - we have a baby stay and this is a weak point, as the deck fitting is NOT attached to the bulkhead. This will be a candidate for change to foreward lowers.

Enjoy you Cruise - we leave on 3rd July - 3 weeks so might see you - look out for us CARINA on the dodgers.
 
Our extra forestay goes to the anchor locker bulkhead and is very substantial but as I say we have twin lowers anyway. I think the main thing that helps stop the mast from 'pumping' is that we have some pre-bend set in the mast to start with so that any loads tend to try to straighten that rather than do other things. Pre-bend set like ours was always the way to go, don't know if the racers agree now or not, but it sure beats it bending the other way!

We leave after 24/7 for 5 weeks so might see you. Boat name is Heartbeat, on the transom but not the dodgers. This is our last season and last Brittany cruise so she is up for sale on our return /forums/images/graemlins/frown.gif We are moving to the USA to liveaboard and cruise from the Chesapeake /forums/images/graemlins/smile.gif but on a displacement trawler yacht so still afloat but not wind powered /forums/images/graemlins/frown.gif
 
I have a Bavaria 42 and had nothing but trouble, Doors not working, slack forstay when beeting, bannana mast when tightening up the back stay etc, etc.

Followed Selden's words to the letter, (using very large spanners) and everyone says mine is one of the stiffest boats arround., Doors work sails work and for the first time she sails well on both Port and Starboard!! The mast nolonger does a belly dance when beating into a sea, Very litlle forestay sag and only use backstay downwind for reassurance.

It was frightening though, watching the shrouds stretch allong side the 2 meter measure. Pluss hard work.

Capt'n D
 
As someone who regularly posts a link to the Selden Advice file I am pleased to hear that their instructions have worked well for you.

Selden are one of the well known spar makers and they should know what they are talking about. Although of course the file is essentially instructions for a Selden mast rigged, presumably, to Selden's specifications.

The file actually goes back along time to before their appearance in the present form on the internet. I have printed books that are earlier versions that were published by Kemp Masts. Given away as part of talks to the club I belonged to in the 1970s and 80s
 
I think you're right, Will, for cruising yachts anyway; I know nothing about racers. Cap'n Cook didn't have steel cables, eh?
 
Quite right CapnD, particularly since yours (and my B44) are fractional rigs and rely on full shroud tension to achieve good forestay tension. The backstay is only for adding a bit of mast bend to flatten the sail.

Unfortunately most comments on this thread applied to masthead rigs where fore-aft tension is determined by the backstay so shroud tension has less importance on tuning but still important to ensure the mast stays in column.

There are many boats around now using aft swept spreaders and fractional rigs and Seldon supplies a high percentage of them so they should know. For my money, I follow the mast manufacturer's recommendations for the specific style of rig.

For the record, I have never had jamming doors under any sailing conditions when rigged as recommended but I agree it does take a bit of effort to crank on the tension and plenty of checks to ensure you are right. Frankly, I think it would be hard for one person to over tension the shrouds on my boat with regular length spanners/shifters.
 
That is exactly what Selden said when I phoned them. Do Not worry you cant over tighten your size rig unless you get silly and use spanners 3 feet long. One thing worth mentioning was that they were very carefull to point out that the rigging screws MUST be clean and well oiled. They told me to back them off, wash and clean the threads, then oil well (3-in-one) then go to work.

Capt'n D
 
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