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Old 29-09-2012, 20:17   #226
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Re: Dismasting - Why Does it Happen - How to Prevent it

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Originally Posted by Lagoon4us View Post
1971? That's quite a recent experience, you'd hope engineering/design has changed a little in 40+ years.
Would have thought the headsail may have tightened somewhat.....

Even earlier around 1969 we were sailing a 25' plywood catamaran across Moreton Bay at 20+knots, BANG the rig came crashing down whilst we were on trapeze (that's a bunch of fun). Stick neatly laid and lashed on deck we proceeded to paddle by hand the 6 miles of sandbars dodging Flathead spikes and Tiger Sharks along the way...

Reason? The ply was rotten, totally rotten! The chainplate on the windward side pulled out of the deck with a 6inch square piece still attached.....

Lesson then was, "Be suspicious of any 25' catamaran for sale with trailer for $40!!!!

Was fun......

Hahahahahahahahahahahahahahahahaha.
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Old 30-09-2012, 01:49   #227
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Re: Dismasting - Why Does it Happen - How to Prevent it

I went up the stick yesterday for a look around..

Found an emerging problem that would result in the rig falling down some time in the future...

It is very simple to fix here in our home port. Only a matter of changing a retaining pin (the big one that the cap shrouds are attached to)... I am going to drop the mast as it will be easier to do the pin without any load on it and also have a very good look round..
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Old 30-09-2012, 08:04   #228
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Re: Dismasting - Why Does it Happen - How to Prevent it

Straight after a boat show recently a rig on a new (imported) cat came down. The issue clearly wasn't age - well you wouldn't think so, - new boat and all that, so either engineering or workmanship was probable cause.
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Old 30-09-2012, 10:08   #229
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Re: Dismasting - Why Does it Happen - How to Prevent it

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I am talking with John Franta at Colligo Marine re Dynex Dux rig. He tells me they are on the point of selling a range of titanium turnbuckles so there is an option to ss.

BRONZE BABY BRONZE
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Old 01-12-2012, 01:27   #230
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Re: Dismasting - Why Does it Happen - How to Prevent it

Using the best design................

Sail-World.com : Vendee Globe - The fixable, the un-fixable and the avoidable

Cheers
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Old 11-01-2013, 11:50   #231
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Re: Dismasting - Why Does it Happen - How to Prevent it

you mentioned a catamaran, I chartered a cat in the BVI's a few years ago and I was impressed with the diameter on the shrouds, It then hit me that the rigging must take one hell of a load when the wind picks up because of lack of heel. I would then assume that the hull, chainplates, fasteners and such must follow suit. I would also assume the builders must have engineered this. let's hope they did their job!
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Old 11-01-2013, 12:01   #232
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Re: Dismasting - Why Does it Happen - How to Prevent it

as regard to stainless steel rigging, 10 years for salt water, 15 years for fresh water are whats recommended. most boats designed in or for fresh water are built using 314 stainless, standing rigging. 316 SS for salt water. wonder how many fresh water built boats are sailing oceans. there has also been an influx of inferior stainless coming in from china and elsewhere. one supplier said there is no american source for stainless anymore. we all know 316 is much more expensive then 314.
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Old 11-01-2013, 16:50   #233
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Re: Dismasting - Why Does it Happen - How to Prevent it

Cable made in the US.
Marine Wire Rope & Cable, Yacht Rigging, Life Line - Loos & Co., Inc.
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Old 12-01-2013, 08:20   #234
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Re: Dismasting - Why Does it Happen - How to Prevent it

The loads on the cat are tremendous since no air is spilled by heeling. Reefing at the designated wind speeds is paramount to keeping the rig safe. I crossed the Atl. on my FP east to west northern route, lots of wind, on the nose, reefed accordingly and had a safe passage. FP did their engineering correctly.
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Old 13-01-2013, 12:04   #235
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Re: Dismasting - Why Does it Happen - How to Prevent it

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you mentioned a catamaran, I chartered a cat in the BVI's a few years ago and I was impressed with the diameter on the shrouds, It then hit me that the rigging must take one hell of a load when the wind picks up because of lack of heel. I would then assume that the hull, chainplates, fasteners and such must follow suit. I would also assume the builders must have engineered this. let's hope they did their job!
Yes, you are right. I have designed or engineered lots of sailboat rigs, including those for multihulls. All sailboat rig design and engineering uses loads based on the righting moment for the boat, whether monohull or multihull, and whether stayed or free-standing. Multihulls have extremely high righting moments, so the loads in their rigs are quite high, and the diameters of the wires are necessarily and correspondingly large. Professional boatbuilders are careful about both engineering and materials, and they are generally quick to respond if some fault in either is identified. Most production boats are designed for salt water, so that's a given that the materieals are properly chosen for sea duty. It is then incumbent upon the owner to properly inspect the rig at regular intervals, and to replace worn, damaged, or corroded parts as necessary. Nothing lasts forever, and you have to have the budget to do the maintenance.

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Old 14-01-2013, 08:46   #236
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Re: Dismasting - Why Does it Happen - How to Prevent it

Dismasting occurs usually from failure of the rigging or buckling of the mast. Rigging failures are more common in old boats. Stainless steel, once thought to last forever, is now known to have a short life in the saltwater environment. Older boats are especially vulnerable with type 304 stainless alloy which exhibits pitting corrosion at normal temps. Most newer fittings are made from type 316 which has more chromium and better corrosion resistance. If any rigging component is over 10 years old, it should be closely inspected for cracks and other signs of corrosion. Welded pieces are known to suffer faster corrosion rates than plain pieces. Remove chainplates and inspect, especially if they go through slots in the deck. The hidden portion is more liable for corrosion. Cracked tangs on the mast are common. Remove the mast and inspect all the components closely, on the ground, where you can take your time and take things apart. Cable assemblies rarely fail, although cracks in swages and mechanical terminals are common. All that rigging is there to keep the mast in column - straight, while under maximum load in a good breeze with all sail up. When sailing to windward, sight up the mast, from the base, and look for bending. Some bending is acceptable, but more than a mast section-width should be corrected. Make adjustments to shroud tension in small increments from the lee side. Do not over tighten the upper shrouds, loosen the ones below to correct bending to leeward at the top. Consult a rigger and learn about your rig. Question everything and if you think there might be something wrong, ask a qualified technician. Most dismasting are avoidable. Forensics frequently show that the impending failure was visible long before it actually broke. Cheers, John Marples, Searunner Design Office
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Old 14-01-2013, 08:59   #237
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Re: Dismasting - Why Does it Happen - How to Prevent it

Dismasting is totally preventable. On a modern fiberglass production catamaran, I would guess the fault is improper tuning. Rigging cables are designed to keep the mast straight under full load (max sail in a breeze to windward). Looking up the mast occasionally can save you the embarrassment of the rig going over the side. It should be straight and not pump or viberate. If it does, reduce sail and consult a rigger. Also, periodically inspect all the rigging components for cracks. Anything stainless steel that is 10 years or older should be closely inspected by a qualified rigger. A little care goes a long way to safer sailing. John Marples, Searunner Design Office
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