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Old 08-07-2018, 20:14   #16
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Re: Dismasting: Deck or keel stepped outcomes?

Calculating loads on masts and rigging isn't rocket science. For cruising boats most reliable builders err on side of caution. But rigging is a "consumable" and does need replacement. And periodic inspection. Where cruisers get into trouble with masts/rigging is not doing periodic inspection and replacement of rigging as needed. To stay in "class" large yachts typically require complete rig removal and inspection every 5 years. A very major expense. Why go sailing if you have doubts about the rig ?
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Old 08-07-2018, 21:48   #17
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Re: Dismasting: Deck or keel stepped outcomes?

I have been on two boats when the stick fell down (both masthead rigs, keel stepped). The first was running downwind with kite, caught the wave ahead, backstay parted, mast failed at deck (it all seem to happen in slow motion) but no deck damage. Second time was when working uphill, windward lower parted at rigging screw swag, mast bowed and ripped a hole across deck before failing. It all seemed to happen quickly and the bang of the lower and the crash of the mast seem to happen together.
I think the wind direction/strength at time of failure has a great deal to due with extent of damage. With a deck stepped mast, there may have been less damage to the deck, but it all happened so quick I don’t know what would have happened.
Cutting loose the rigging is the dangerous part in the seaway. The downwind incident we were able to recover the mast and sails while the dismantling upwind everything was cut and let go as it was in danger of puncturing the hull.
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Old 09-07-2018, 07:57   #18
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Re: Dismasting: Deck or keel stepped outcomes?

I think this thread has a danger of becoming a "which anchor is better". But I will provide my thoughts. First, I must tell you that I have been through a dismasting. My boat is deck-stepped. Here's a brief account of what happened and the outcome.

In preparation for an offshore race, the rigging had been completely inspected and tuned several months prior to the race. The day before the race, the main halyard was replaced and the rig was visually inspected by an experienced rigger. No defects were identified.

Dismasting occurred about 100 miles offshore in winds 35-45kts winds. Conditions were rough with short-period waves (Gulf of Mexico). We were close hauled. At midnight, with no warning, the rig came backwards, bounced off our arch and went over the port side. Fortunately, and largely due to our arch, nobody was injured. After assessing the situation we set about cutting the shrouds and running rigging to free the rig and ditch it. For anyone interested, there's a more detailed account at: https://midnightsunii.blogspot.com/2...-and-ugly.html

Based on the way the rig fell, I am pretty sure that either the forestay broke, or something at or near the masthead. Being deck-stepped, there was no damage to the boat structure - just some bent stanchions, and a crushed bimini and dodger.

The lessons I learned from this are:
- Carry bolt cutters (we did), but now have 2 sets, conventional and hydraulic. SS cable is difficult to cut even with the adrenaline flowing!
- Don't rely on visual inspections - the cables and fittings have a lifespan and have to be changed, even if inspections show no defects. Having said that, I have concerns about the quality of presently available stainless, as I suspect a lot is being imported from China. This is a whole separate topic.
- The forestay is the "weak link" in the rig on many boats, i.e. there is no back-up/redundancy. When we replaced our mast, we had a removable inner forestay added to the new mast, together with a reinforced attachment point. Now, we never sail offshore without it being attached.

I hope this helps and gives food for thought....
Neil
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Old 09-07-2018, 08:42   #19
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Re: Dismasting: Deck or keel stepped outcomes?

Redundancy was a major object of my post above.

Fine for inshore work I guess.

B and R rig, which has no backstay, comes to mind quickly.

https://www.boats.com/reviews/boats/the-bampr-rig/

http://www.cruisersforum.com/forums/...r-rig-816.html
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Old 09-07-2018, 10:46   #20
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Re: Dismasting: Deck or keel stepped outcomes?

Wotname:

Comparing two boats of the same design and mast height, the keel stepped mast would be longer...mine is nine feet from step to cabin roof. If one assumes the force on the mast equally distributed at the center, the longer mast center would be lower. How significant is that, I can't say but assume lower is always better (think of changing the center of force when striking the genoa, keeping the staysail and reefing the main moving the wind force aft but also lower).

On another note, how a dismasting takes place is dependent on many factors, assuming it always happens at the base is na´ve. Most dismasting's I have seen have been at the spreaders or higher (watch YouTube dismasting's) with secondary damage following later. Dismasting's also occur most often during racing events when the crew pushes the boat beyond its limits...not as likely for a responsible cruiser with a destination in mind, but they do happen.

~ ~ _/) ~ ~ MJH
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