Topic: Standing Rigging Specs

Hello Everyone,

I'm wondering if anyone has the (manufacturer's) STANDING RIGGING SPECIFICATIONS for our Contessa sailboats that they could share (wire sizes and tensions)?

With a Loos Gauge and this info, getting the standing rigging tuned up should be a fairly common-sense affair.  I'm planning on just hoisting the old rig and tuning it to specs, and then adjusting the wire lengths a little here and there for where ever I want them to be on the turnbuckles when I make the new ones with Norseman fittings.

Thanks,

Brian

Re: Standing Rigging Specs

No sure about manufactures specs but the standing rigging on my boat was original until  last and this year. I am just finishing up replacing it all over the last two winters.
It was;
3/16 for upper shrouds and front/back stay.
5/32 for lower shrouds

replaced with;
3/16 for upper shrouds and front/back stay.
3/16 for lower shrouds

I use a loos tension tool to set tension on upper shrouds and stays. I can't recall what the tension should be. With that said the tension is not(in general sense) determined by the boat but rather by the dia of the rigging(IMHO). I just follow the guide that came with the loos tool.


I moved up a size on the lower shrouds not for strength but for simplicity as it made sense to keep them all the same dia. I ran this idea by my rigger and he agreed after I explained that the chain plates are all the same size and bolted onto the boat in the same fashion.  Meaning that the fibreglass mount for the lower shroud is of the same construction as the upper shroud chain plate mounts. Not that it matters too much as the lower shrouds have less tension to begin with.

John

Re: Standing Rigging Specs

John,

That is very interesting.  Thank you for your input on this posting.
That sounds like a great idea how you just beefed up the lowers so you could make everything out of the same wire.  I think I'll do the same.  It doesn't seem like it would be that much extra weight aloft either.  I also love the idea of simplifying the whole thing.

Brian

Re: Standing Rigging Specs

Hello All,

I just finished reading the chapter on standing rigging in Toss's Rigger's Apprentice book.  Here are some interesting things I learned that I wanted to share with everyone that are relevant to this thread.

First of all, I've become uneasy about replacing the lower 5/32" shrouds with 3/16".  Here is why:  Standing rigging wires are tensioned as a percentage of their breaking strength.  5/32" 1x19 stainless rigging wire has a breaking strength of 3300 lbs versus a breaking strength of 4700 lbs for 3/16" wire.  And when you use the charts that come with the Loos Rigging Tension Gauge (available at their website) this means that the lower shrouds would be tensioned to 500 lbs with 3/16" wire instead of the 350 lbs with the 5/32" wire.  With 4 lower shrouds, that is an extra 600 lbs of tension.  The mostly vertical component of this extra force would be about 500 lbs of extra compression load on the mast, and the other (horizontal component) of this extra tension would be more load on the shroud connections. 

The bottom line here is that their is some design stuff going on here that probably ought to be considered.  I know that "deck compression" is one of those "contessa issues," apparently on newer boats.  Do we really want more force on the deck?

Having said all this, the book says that it is a popular theme among blue water cruisers to try and make all the rigging wires the same size for the obvious reason of having to minimize the number and cost of spares for repairs. 

I've emailed Jeremy and Fiona to see if I can get a little "builder input" on this issue and I also asked them for the original rigging specs.  When I hear back, I'll make sure and post this stuff. 

Best wishes,

B

Re: Standing Rigging Specs

Brian

I am playing devils advocate with this post as I don't pretend to be overly knowledgeable on the subject. With that said;

I have always understood that the lower shrouds should be tensioned enough that they are tight on the windward side of the boat but just slightly slack on the leeward side of the boat. Meaning when on a port tack, reaching,  my starboard tack lower shrouds are just slightly loose. Not flapping around but loose enough that they have no pull or strain on the mast.
Point being if the starboard 5/32's lower shrouds in the above scenario where tensioned to 350 lbs, they would be too tight. Or if 3/16's in size, 500 pounds of tension would again be too tight. 

If the above is true then the tension on either 5/32 or 3/16's lower shrouds would be light enough to have little to no impact on mast/deck compression, as the upper shrouds would already be tensioned far more than the lowers.

Again, I stand corrected, but I suspect that 3/16's lower shrouds may require slightly more tension than 5/32's to reach the "just tight enough" scenario but given that the chain plates for both upper and lower are identical in size and bolted to the boat in identical fashion I suspect the extra tension is irreverent.

I would be interested in hearing what the designer has to say on the subject.

I hope I am no completely off base as I have a set of brand new shiny 3/16's lower shrouds sitting on my couch just waiting for the snow to melt smile 

John

Re: Standing Rigging Specs

Hi John,

Nothing like a devils advocate to help us find the right answer!  I'm no expert either....maybe the two of us will figure this stuff out.  Thanks for your ideas and input.

I think you are probably right about the tension not being that big of a deal if you are willing to go with a more slack rig than a lot of pro riggers (like B. Toss -- Rigger's Apprentice book) would recommend.  And, as it states in the manual that comes with the Loos Tension Gauge, a lot of people do sail with more slack in their rig than is recommended for fear of "breaking something."

However, they also state in that manual in the "additional information" section that:

"Contrary to popular thought, a slack rig is more punishing on a hull than a properly adjusted rig.  Insufficient tension will reduce the loads transmitted to the hull.  Slack rigging will punish the spar and rigging needlessly by allowing excessive movement, chafe and shock loading.  Modern fiberglass hulls should not be damaged by properly adjusted, tight rig.  (then some other stuff here, followed by)  For the properly tuned rig the leeward shrouds will not go slack under normal sailing conditions.  The lateral stiffness of the mast and the fore and aft stiffness of the spreaders is reduced by a factor of 2 when the leeward shrouds go slack.  This important structural characteristic is not generally recognized." 

They got my attention with this stuff.  To wrap up, you are right about how all the spreaders seem to attach to the hull in the same way structurally.  And it would be ideal to have all the same size wires and terminals for simplicity.  I think the only question is whether the mast and deck can take a little extra load, if you do want to tighten the 3/16" lowers to "proper tension" which is about 10.6%.  I think the designer might say that the boat and mast could take a little extra tension and it would be OK, but I just don't know, yet -- These are some pretty ridgid little boas.  They may have just used the 5/32" lower shrouds mainly for cost savings.

A little off the topic of this specific shroud debate (for those who are reading this and wonder about the tensioning of the other wires) the manual with the Loos gauge gave some pretty good info on this subject and was backed up by the info in the Toss book.  The 3/16" headstay is tensioned to about 16% of its breaking strength (750 lbs) and the backstay is tensioned so that the mast is straight with the headstay tensioned as mentioned (it will be a lower tension because of the larger angle in which it leaves the mast).  Then the shrouds are tensioned at 10.6% of their breaking strength (500 lbs for 3/16" wire and 350 lbs for 5/32" wire).  That's it. 

B

Re: Standing Rigging Specs

I wonder if the mast profile is relevant?  The Contessa mast (certainly for my 1976) is much more substantial than that of a similarly sized J-24.  Modern masts tend to resemble racing masts, hence are much more bendy, and would therefore benefit from more tension in the rig.

I also suppose that one could use 3/16" wire for both the upper and lower shrouds but tension to 500 and 350 as appropriate.  Stretch would mean a bit more play in the lowers when the mast is under load but I would consider this acceptable given that most of our boats are at the dock 99% of the time.  (Sadly!).

Anyway rig tension is another thing to play with in the spring!

Re: Standing Rigging Specs

Today, I got a response from a representative of jeremyrodgers.co.uk.  Here is what she said:

"Thank you for the email.  Iā€™m afraid it is difficult to advise on the JJ Taylor CO26 because the rig was usually a little taller than the rig on the Jeremy Rogers builds.   We recommend 5mm all round on our boats.  We also think the Norseman swageless fittings are very good. I am sorry that we cannot help with your tensioning question, but you may be able to get a local rigger to look at it and advise."

Looks like 5 mm is extremely close in size to 3/16"

Thought you all might like to know the conclusion on this correspondence.

I guess the right person to ask for the original "rigging specifications" would be Gary Bannister (the builder of the J.J. Taylor Contessas).  Does anyone have his email?

B

Re: Standing Rigging Specs

Hello Everyone,

There is this one other thing that I thought I might mention on this topic of standing rigging and it's proper tensioning and that was a discrepancy between Toss's book and the Loos instructions.

As mentioned above, the Loos Gauge says to tighten ALL shrouds to around 10.6%  The Toss book says that the tension is set relative to the length because of the increased stretch for longer wires and that the whole purpose is to keep the mast straight when under a load in all planes.  Seems to make a lot of sense to me.  The Toss book does not differentiate between stays and shrouds and simply says to set the lowers to 10-12% if there breaking strength, intermediates (if you have them, I'm interpreting) to 12-15%, and uppers to 15-20%. 

I think what I'm going to do is go ahead and set the rigging tension as I previously described with ALL shrouds set to about 11% like the Loos Instructions say to do.  Then, when I get the opportunity, I'm going to sight up the mast and check for straightness while sailing close hauled in a pretty good blow.  If I see the upper mast curving off to leeward some, then I'll start raising the upper shroud tension as needed (towards the Toss recommendations) until I see the "stick" able to maintain its straightness.

B

Re: Standing Rigging Specs

Hello Everyone,

I wanted to make one final appeal to anyone who may have been at the dinner party with Tania Aebi and Gary Bannister (and may have a way of getting in touch with Gary) to see if they could either provide me with an email address for Gary (or perhaps they could contact him privately, if they don't want to give out his contact info) and see if we could get him to "weigh in" on the standing rigging specs issue. 

I would like to increase the size of my lower shrouds (like John did) to 3/16" in an effort to add a little more strength as well as to simplify the rig, but before I do that, I'd VERY MUCH like to hear what the builder would say about the hulls ability to handle the extra strain when properly tuned as well as the extra mast compression forces.

Thanks much,

Brian

Re: Standing Rigging Specs

Hello John,

You said that you'd be interested in hearing what the builder had to say.

I just spoke with Gary Bannister on the phone and he said that he thought it was a good idea and that he saw no problems with upgrading the lower shrouds to 3/16" so that all stays and shrouds were standardized like you are doing.  He also said that this is what they started doing on the later boats anyway.

Thought you might like to know. 

This is what I've decided to do myself.  I'm going to drill out all the holes on the mast tangs, masthead and chain plates as well so that all wires are 3/16" and all clevis pins are 3/8".

B

Re: Standing Rigging Specs

Hi all,

Back on line so must be back at work.  Bummer.  Anyway, I went through similar thoughts re: do I change my rigging or leave it original.  Virago is an '85 and her standing rigging is uniform, and I decided to leave it as originally delivered for the same reasons as given several posts earlier - there's probably design stuff going on that I don't want to meddle with.  I did decide to replace my back stay due to it having quite a kink in it when not under load (mast down on the ground).  I took it to Klacko spars in Oakville, Ont. as they still support Cinkel spars (and pretty well any other spar too!).  Got it replaced to match the rest of the existing rigging (same fittings etc.) for under $200.00.  For anyone who doesn't want to D.I.Y. their rigging, Klacko is where many other marinas and boat shops send their work to anyway.  End fittings are European (Swedish or Danish methinks), wire from one of the Koreas.