Guest Posted June 28, 2013 Share Posted June 28, 2013 Interesting stuff IT. There's not any mention of the effects of the mast though. I don't see how stability in yachts can be seriously discussed leaving the mast out of the test. Link to post Share on other sites
Guest Posted June 28, 2013 Share Posted June 28, 2013 ANd what would you recommend for a cruiser not a racer i.e. longevity and reliability and price are more important, Link to post Share on other sites
Island Time 1,235 Posted June 28, 2013 Share Posted June 28, 2013 He does mention it - at the beginning he says they have left out inertia! I have test dat somewhere that goes into the stability in breaking waves, inertia etc - I'll try to find that. However, the basic fact is that by having additional weight aloft, you raise the CG, lessen the righting moment, and decrease the angle of vanishing stability. All bad. The only time the mass of the rig helps, is to add inertia, which must be overcome to allow a vessel to capsize.... I'll see it I can find that data. Link to post Share on other sites
Island Time 1,235 Posted June 28, 2013 Share Posted June 28, 2013 Sorry, forgot to say that all those calculations and diagrams do include the mast - it effects the position of the CG, even though it may (isn't) shown in the diagrams... The only bit he leaves out is the inertia...and he does say that. Link to post Share on other sites
gurge 0 Posted June 28, 2013 Share Posted June 28, 2013 On the Amsteel Blue - we sent (not where I work now) a line back to the factory for testing.It had minor chaff and had reached its allotted number of jobs. It broke at less than 40% of it's rated avg - it broke at one of the splices. KM do you have any data on fatigue cycling in dyneema Would that have been ONE of the reasons the ferry let go in the latest storm. Link to post Share on other sites
Guest Posted June 28, 2013 Share Posted June 28, 2013 On the Amsteel Blue - we sent (not where I work now) a line back to the factory for testing.It had minor chaff and had reached its allotted number of jobs. It broke at less than 40% of it's rated avg - it broke at one of the splices. KM do you have any data on fatigue cycling in dyneema That sounds right Rigger. Saw some testing on a Amsteel competitor recently and it also looked fine but was breaking between 38 and 47% of it's listed break load. Mind you it was made by a mob known to use load numbers only they seem to be able to achieve. I have a pile of dyneema and vectrans I've had on my boat for 5 years here and we are going to bust them. I have the numbers from brand new so it'll be interesting to see what we see. Fatigue, yes I do somewhere, I'll dig them out. One thing on those that does jump out big time is the heat treated lines have totally shite resistance compared to the non-heat treated. Colligo and some others base a lot of their stuff on the heat treated. On a cruising boat, all boats really, there are places using a fibre makes 100% sense but there are others it just doesn't. Again talking the usual way Kiwis make it as opposed to Team NZ for example. Also excluding Multis from that as they are good for fibre due to the angles. Like most things it's a horses for courses thing. Fibre is getting there but personally for most of us it's still got a little ways to go before we can get a 100% fibre system working well within a budget knot of ETNZ scale. Have a suss of this, it's real fibre rigging the racers and like use. You'll see it's very different that what you'll find in Westhaven. http://www.softrig.it/en/cavi-pbo.html Link to post Share on other sites
Guest Posted June 28, 2013 Share Posted June 28, 2013 Yes its a complicated subject to tackle in ones head on a friday night IT. The inertia must be important. I mean its better not to get knocked down than to have to recover from it. I wonder how much effect the weight difference would have in this regard between stainless rigging and Dyneema. the strength of stainless as used in most offshore yachts seems to me to be perfectly adequate. That is, not many seem to lose the mast from the rigging breaking but the mast will often break with the rigging intact, having to be cut away. I may be shouted down about that but I've already got my hands over my ears. Always happy to be corrected. So with dyneema at the same strength as stainless a lot of weight and windage could be done away with. Link to post Share on other sites
Chewing Gum 17 Posted June 28, 2013 Share Posted June 28, 2013 Our backstay is fibre for the bottom half running over a pulley (adjustable). Not sure what fibre it is but it is grey in colour and a fairly coarse braid about 12mm dia. It failed over the pulley after about five years I suspect from uv damage. The running backstays are also fibre and are a whiter colour with what looks like a fine weave braided sheath. They are 10years old and haven't failed yet. The rigging was all done by Bruce Elliot so will be good stuff. The upper lifelines are stainless with fibre braid about 4or 5 mm that looks the same as the backstay (dark grey). They are about 5 years old. Neither the backstay nor the runners are critical to the rig. I would be reluctant to use fibre on the side or forestays because of uv degradation. Mast is 7/8 rig and about 18m off the deck. Link to post Share on other sites
idlerboat 116 Posted June 28, 2013 Share Posted June 28, 2013 A very interesting and for me, a difficult subject. I think its probably easier to seperate the choice of non metal rigging away from stability. The reason is that when you add a radome and a sail up, along with a heavy mast section , what proportion will a change make ? To make it more difficult, on a vessel like mine, I have heavy everything, continuous stays, double back stays, inner fore stay (baby stay) and permenant aft intermediates. (In this last I have seen a huge trend towards dynema/spectra for running backstays even on the heaviest of cruising boats...this is mostly due to the much easier handling). My point is that in a differant boat with a swept back spreader setup and discontinuous rigging, (or even some hunters with no back stays) The rigging is minimal and therefore the change in weight aloft . Most old school cruising boats have a slower roll momentum than modern racing boats. Desingned for comfort, not for speed. Knockdown resitance and self righting are not nessesarily related. Let me give you an example. A broad beam boat has "form stability" and will resist a knockdown and perhaps help to slide side ways (Cats are the ultimate example) but conversly resist righting once turtle for the same reason. Sorry if I am going over old ground, but the purpose is to ask just how much , and to what differance the change in weight aloft makes ? A further point on inverse stability....flush decks are bad ! The vessel becomes a pontoon, with huge amounts of inverse stability. The very resason that pilot boats have large upper structures. They are simply uncomfortable upside down. A good reason for raised and rounded upper coachroof design. A difficult thing if you want to reduce "wave strike area" For me the question with non metal rigging is less about weight than, reliability. I am not worried so much about strength, or even longevity...I will take a punt on those.....BUT....I have NO faith in chafe resitance. I have seen how quickly a taugh dynema over dynema wears... I know there is some development in soft tube covers. That is an oversized polyester cover that rolls with crossed lines. As a final point, I would love this technology to come of age. It would mean that I could change stays on the go. Carying a full roll swage unit on board aint going to happen. Carrying a reel of wire and norseman or staylock fittings is expensive and hard to deal with. My "multi strand" opinion on this Link to post Share on other sites
Island Time 1,235 Posted June 28, 2013 Share Posted June 28, 2013 Pretty much agree IB. I've gone the norseman type solution at the moment. Similar rig to you, Masthead, twin straight spreader, intermediates, aft lowers, babystay. Single backstay though. Synthetics would be nice and I can see the day... It's not hard to work out the effect it would have, just basic loading calcs with the weights and distances from CG.... Link to post Share on other sites
idlerboat 116 Posted June 28, 2013 Share Posted June 28, 2013 Hi IT, It's not hard to work out the effect it would have, just basic loading calcs with the weights and distances from CG.... This is where it gets a bit hard for me. The design CG is not nessesarily where the real boat has it. As an example. If you have outboard tanks, that is at the water line and on the hull, like a lot of early *80s designs to slow the roll momentum, or ..inboard around the keel to make the self righting moment better. 300 kgs of water, and 300 kgs of diesel. And thats light. The CG is so differant. I have seen so few boats finished to the designers specs. In racing boats with a purpose of NO weight it is not so hard. In a cruising boat...just where is that weight put ? The CG in its pure form becomes hard to define. *I would like to know (without being stupid) how much differance does it make) (as an edit) I can only guess on the various mast sections and rigs. On a 45 footer with all the crap..five of us can carry it. so Im guessing 200 kg aloft. (or I am a strong bastard).. Link to post Share on other sites
Guest Posted June 28, 2013 Share Posted June 28, 2013 Certainly looks heaps more nautical. Link to post Share on other sites
idlerboat 116 Posted June 28, 2013 Share Posted June 28, 2013 Certainly looks heaps more nautical. Yeah I like my strings and wires My 2 banks of 7 jammers across the coach roof make me smile........a childhood dream...(I could never afford them) ,bash to the mast...nah..Im a crusing boat. Slow and strong. All too the cockpit. Link to post Share on other sites
Guest Posted June 28, 2013 Share Posted June 28, 2013 SS has its problems. You cannot see the fatigue. Usually need professionals to make it up. More difficult to carry spares. I believe the synthetic shows its fatigue and is very obvious and I think thats a definite plus. Link to post Share on other sites
Guest Posted June 28, 2013 Share Posted June 28, 2013 The reason I brough the whole subjec tup was tha tit was adiscussed a while back and the opinion was that it 'wasn't quite there yet". A pity as I'd love it for all the reasons IB mentions.I think in the meantime, SS with enough fibre on board to repair the longest stay?? Link to post Share on other sites
Island Time 1,235 Posted June 28, 2013 Share Posted June 28, 2013 IB here is an article and database program to help with your CG issue. It allows for all 3 CG's (Longitudinal, transverse, and Vertical), and lets you work them out for your loaded vessel... A bit of work, but not technically difficult. Link to post Share on other sites
Guest Posted June 29, 2013 Share Posted June 29, 2013 I don't think " failure" is the issue in either case Motorbike, seems any well looked after vessel will have her rigging changed at the right time. Link to post Share on other sites
Guest Posted June 29, 2013 Share Posted June 29, 2013 Actually, why not dump the rig and build some freestanding rotating wingmasts? Then you can have a shorter rig with the same power or the more height and more power. Rigs are ridiculous! Link to post Share on other sites
rigger 47 Posted June 29, 2013 Share Posted June 29, 2013 A few years ago I was involved in replacing the galv wire rigging on a small brig - the old wire was ~30years old. I believe that most of it could have gone for few more years. FWIIW - the boat had a 3-4 year period where zero maintenance was carried out. One option for cruisers could be to carry a coil of galv wire twice the length of the longest stay, have a splice and thimble put in each end, carry enough bull dog grips and a spare thimble or 2 - that way if a wire fails you can put a spliced eye up high and put bulldogs on the lower end - and you still have enough wire to replace another stay / shroud - or at the next port you could get a splice put into the other end of the remaining spare wire and refit it as a semi permanent replacement. I suggest Galv wire as you can more easily splice it than SS. BTW Chaff can be a cause of failure in wire rigging. Link to post Share on other sites
BNG 44 Posted June 29, 2013 Share Posted June 29, 2013 http://www.colligomarine.com/products/colligo-value/emergency-shroud-kits Link to post Share on other sites
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