Standing rigging replacement. Synthetic rigging

Discussion in 'Boat Design' started by bulk-head, Jul 25, 2009.

  1. bulk-head
    Joined: Dec 2007
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    Location: Antigua

    bulk-head Junior Member

    Hi, sorry if I post on the wrong thread, and its possible that a thread is already in progress concerning this. Does anyone have any input on composite rigging. Its becoming time to replace the rod on the yacht and the rigging companies are all pushing composite rigging. Its expensive. What is it service life ? When Im struck by lightning with the charge travel down the carbon mast tube rather than the steel rigging ? UV and chafe damage ? How is it controlled ? Do you inspect the rigging or discard it at service interval ? Any input...Thanks Oh this is an 25 meter ocean going sailing yacht...50 tons, 20, 000 miles per year...carbon 4 spreader rig
     
  2. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    Just some assumptions:

    Rig height of 100'
    Jumpers at each spreader
    -30 Nitrox rod rigging .511lbs/foot $16.58/foot
    Dynex Dux 11mm .0797lbs.foot $9.08/foot
    450 foot of rigging
    Average height above sealevel for rigging - 50 foot

    Putting something like 450 foot of rod aloft with an average height above sealevel of 50'. The rod weighs .511lbs per foot, or 230 pounds aloft, at the assumed height you are generating 11,500 foot pounds of torque (at a 90 degree heel). Yes this is an extreme angle, but it keeps the math simple. Compare this to composite rigging with a weight of .0797 pounds per foot for 11mm Dynex Dux. At the assumed height of 50' you are now generating only 1,793 foot pounds of torque (at the same 90 degree heel).

    This is probably the biggest advantage to switching to composit rigging versus rod. If you had wire the difference would be even greater. Since you have gotten a HUGE amount of righting moment back by doing nothing more than lightning the rigging weight.



    As for the rest of your questions:

    Expense - Normal installations are price competative for the initial installation, the ones I have seen are within 10% either way. However for replacements down the rode the price actually drops for composite rigging since most of the end fittings can be easily replaced.

    The service life on modern line Dux is going to be less than rod or wire. Something around 5 years is the current wisdom, but long term studies are still continuing. Compare this to 10 years which is the service life of nitrox and it can get scarry. However remember that the price for the initial installation is a LOT more than the price for the replacement, since the fittings are reused. You are only replacing the line itself (plus a couple of splices)

    If you are hit by lightning it won't matter what your rig is made of, just hope the keel bolts don't blow off, or the through hull fittings don't explode, or the batterie lead melt. No boat can realistically survive a direct strike from lightning, rigging won't matter.

    UV issues - Well UV is the biggest factor in the 5 year replacement cycle. All of the lines sold for rigging are UV stabalized, covered, have chaff protection ect... But all of this can only slow down the inevitable process of the degredation not stop it. So far my experience is that so long as reasonable chaff protection is put in place it is the UV that is the problem. One of the differences in the Dux vs Amsteel Blue is that every fiber of the Dux is coated to prevent UV as compared to just the finished line for Amsteel. This goes a long way to preventing all but the very surface layer of the line from being damaged by UV.

    Chaff issues - This is the same line that loggers use unprotected to drag trees out of the forest with, and tug boats are using to replace thier towing bridles. Not that Chaff isn't an issue, but this stuff is very, very hard to cut even when you are trying too, let alone a little chaff issues.

    Other issues:

    It is easy to buy a spare shroud and keep then it coiled away in the event of a failure. Pretty cheap insurance and effectively impossible with rod.

    With Dux on the market I wouldn't really look at PBO, it is great for some applications, but the UV resistance on it is crap, plus Dux is 1/3 the price.

    Since this stuff can be spliced easily, there is no need to have a rigger do the work, assuming you are comfortable doing 12-strand braided splices.

    There is almost no elasticity in rope, if it does fail instead of exploding and whipping like wire it just falls to the deck preventing secondary injuried.




    As you may be able to tell I am a huge fan of Dux, and would at this point never recommend anyone put rod or wire back on a boat. There is just no good justification for it anymore, and the weight penalty is huge.
     
  3. bulk-head
    Joined: Dec 2007
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    Location: Antigua

    bulk-head Junior Member

    Thanks for the reply Stubble, The mast currently has a rod package using Riggarna end fittings and OS rod. I can understand that significant weight reduction aloft and greater righting moment will be achieved.
    I'm assuming that the mast tube is engineered to take the addition compression load as a result of this greater righting moment ? Must I contact a naval architect for approval before increasing the righting moment ?
    As far as Lightning strikes, and after 278 thousand miles with this yacht Ive had a few, the original design spec on the mast were to completely isolate the rod from the carbon tube . This was achieved with layers of nonconsecutive e/glass laminated to the mast walls at all rigging and spreader attachment point. This is a very elegant, spirally wound carbon tube constructed in 1992 engineered for durability and low maitence, its not light.. 4 spreaders, cutter rigged with jumpers. The logic was that the electrical charge would avoid the carbon tube and travel down the rod and dissipate into the aluminum hull and surrounding sea water. this logic seems to have been effective although each time Ive been blasted, my knuckles were white and unfortunately my eyes were closed so I haven't actually witnessed the lightnings intensity nor path. I have seen damaged carbon mast tubes in which the charge traveled down the tube and then tried to escape, arc thru the mast wall at the mast partners...naturally blowing a hole thru the side of the tube..
    Which brand end fitting are being used ? I assume these end fittings mimic the fittings on my fabric running backstays ?
    Some years ago on the yacht I had pultruded kevlar diagonals. Beautifull stuff, expensive and unfortunately after 25 thousand miles the riggers condemned them. UV damage and chafe. 25 thousand miles is way to short for my usage. Hauling the rig every year is a nightmare. I prefer to step the rig every 4 or 5 years. Will this be achievable with fabric rigging.
    Do you inspect fabric rigging at service intervals or do you simply replace it ?
    What is the position of the insurance company ?
    We carry an overlapping sailplan...ie a 130 percent genoa. I assume that the available chafe protection is very robust ? What I have observed on the gran prix race boats is a carbon kevlar tube slide over the rigging before the end fittings are installed. I assume that once this chafe protection has expired you will no longer be able to renew it and will replace the shroud ??
    Price ? 6 years ago the rod package...not end fittings ....was replace 22 thousand euro at the time. Cheap. Will a fabric package be in the same region ?
    At present I only have some boat show literature from Future Fibres, Hall Spars and Navtec. Since I am presently sailing is there any more handy information on the net ? Cheers Mike....Oh and 25knts broad reaching today..not bad, not bad at all.
     
  4. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    Bulk,

    To take your concerns in order:

    1) I couldn't really say if you need to get a NA to approve of the additional loads. Though the other option is to shorten sail a little sooner in terms of heel. I have never heard of anyone having a problem with this, but I couldn't rule it out either.

    2) Are we talking about a firsct lightning strike, or just something nearby? The only boat I have ever been a part of that had a direct hit was totaled immediatly, every piece of electronics was fried, the grounding strap melted, battery plates melted, the through hull fittings blew out of the boat ect. This was with a heavily reinforced ground system that had seen us through a number of near strikes, and even hitting a power line with little to no damage.

    3) There are a few different brands in the market, but Colligo seems to be the best. I haven't used them personally but that is the word I have heard. http://www.colligomarine.com/Colligo-Synthetic-Systems . The end fittings are specially designed for the application, including keeping a large enough radious bend on the line to keep it from being pinched.

    4) Because the line degrades as a factor of sun exposure not really chaff I doubt that the miles sailed would really effect the life expectancy. I would imagine that a normal annual aloft inspection of fittings would be reasonable, but I like to look at things more often than that personally. I normally go up the rig every quarter just to look for loose wires, blown bulbs, ect. I do a visual inspection of the whole system at the same time.

    5) Right now there is no standard replacement interval for rope. The current best wisdom is that it has a service life of 5 years, but accellerated UV tests are still going on. Personally I think this is just something that you need to inspect reqularly and use your best guess on. But it has been proven to be incredibly durrable compared to the old composite stuff like PBO, spectra, Kevlar, ect.

    6) My insurance company didn't care. Nor have I heard of any that do. But it might be worth checking first.

    7) Dux normally is installed with no chaff protection at all, at least not for the line. Though the turn buckles or end fittings may get some to protect the sails. Like I said the reality is that logging companies are using this unprotected to drag trees through the forest with no problems. I just can't see the type of incidental chaff experienced for rigging being a problem.

    8) The Carbon/Kevlar sheath you are talking about is used for PBO not Dux. Mostly because PBO degrades so fast in UV you can almost see the dollar bills flying off the material as it is exposed to sunlight. This stuff is a whole different animal.

    9) I couldn't begin to actually put a price on a new system. Not that I wouldn't try, but because it would be to dependant on the actual leingth of the shrouds involved. You could head over to Colligo and price out the components yourself if you know the leingth of each stay. But from what I have seen doing a Dynex Dux rig including the one time investment for fittings normally comes out about 10-15% less than rod. The second time around it is significantly cheaper since you can reuse the fittings.

    10) For more information... I will link some websites, but definatly head over to Brion Toss' page. It is an incredible resource for all things rigging.

    http://www.colligomarine.com/
    http://www.briontoss.com/spartalk/
    http://www.strongrope.com/fibre-rigging.htm
    http://www.osha.oregon.gov/grants/osuforest/osuoverview.html

    And no 25kn reaching is not bad at all :D
     

  5. bulk-head
    Joined: Dec 2007
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    Location: Antigua

    bulk-head Junior Member

    Ya , that lightning is funny stuff and like I said, I'm normally on my hands and knees holding on to the steering wheel, wishing I had a pair of industrail rubber gloves on, saying my prayers with my eyes shut when it strikes, so I really couldn't tell you if its a direct hit or simply a major nearby discharge. I do see the damage with dangling VHF ants and B and G wands. At present half the reason for pulling the mast is burnt up VHF cable. Direct blast ? I just don't know. Although several years ago I was alongside in the harbor of Brioni. A major thunderstorm was in progress, I was holding out down below with a coffee and the owner and guests were in a restaurant overlooking the harbour, watching things unfold. KAABOOM !!!! a massive blast and next thing I know the owner and the harbor master are standing in the driving rain next to the boat shouting ARE YOU OK ? evidently while they were enjoying the show , sipping a drink, they witnessed a full on lightning strike to the yacht. Again it turned out that the only damage was VHF aerial, masthead strobe light and a completely toasted brain on the fly by wire MicroCommander , engine controll system . and once again perhaps the lightning struck close, but not direct...mysterious stuff...and thanks for the reading material, Ill have a look when I get more bandwidth on this internet con... Bulk head
     
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