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Old 27-07-2012, 22:40   #31
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Re: Dismasting - why does it happen, how to prevent it

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Originally Posted by Stumble View Post
Sadly this is just a myth.

External chainplates are at least as susceptible to crevice corrosion as through deck ones are. Obviously the outside part of the chainplate will be fine, but the entire side pressed against the hull is in danger. It may however be easier to remove and inspect external chainplates, but unless this is done regularly it really won't matter.

I really did try guys, but the real solution is to just toss stainless steel overboard, and switch to titanium. Once installed, titanium is immune to corrosion in marine environments, and unlike stainless doesn't work harden. So they realistically should last forever, absent physical damage, since there isn't a form of corrosion that effects titanium until tempratures reach 180 degrees F.
Don't forget composite construction for chainplates. Will last the life of the vessel.
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Old 27-07-2012, 23:13   #32
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Re: Dismasting - why does it happen, how to prevent it

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Don't forget composite construction for chainplates. Will last the life of the vessel.
I don't think they are there yet, and there are some real long term concerns about fatigue life. But they are certainly looking like a possibility long term.

One of the big problems though is they have to be installed after the deck and the hull are joined. Not really a big deal for stripped out race boats, but it could cause all sorts of problems for cruising/mass market boats, since it makes the building process a lot harder. A number of builders currently install internal fittings and furniture before the deck is installed, this isn't possible with composite chainplates since they are attached to the hull after the deck is put on.
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Old 27-07-2012, 23:17   #33
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Re: Dismasting - why does it happen, how to prevent it

When talking about composite chain plates :
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Originally Posted by Stumble View Post
I don't think they are there yet, and there are some real long term concerns about fatigue life. But they are certainly looking like a possibility long term..
No probably not there for production builders, except where there is a specialist need - eg corsair, but certainly are there for custom builds, There are plenty of boats with plenty of hard fast ocean miles on them and indeed plenty of years that have composite fittings and are doing just fine. Indeed if if was talented enough to build my own boat I would be very keen to go composite fittings.
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Old 27-07-2012, 23:19   #34
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Re: Dismasting - why does it happen, how to prevent it

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Originally Posted by Rakuflames View Post
. I just can't think of a good reason for a cruiser to deliberately sail 1 - 2 knots slower than they can.

If the rigging is in good condition, sailing fast won't bring it down. Cruisers are destination sailors. Why take 4 hours longer than you should because you don't trust your rigging? Check it out and then go have fun!
4 days, not hours, anyway if you talk about cruising.. And there's a good reasons like chafe and wearing. Sails get double the life span if not driven too hard. Same goes with other gear in running rigging. That might not be a problem staying few days sailing away from good chandlery and sailmaker. Four months away you need a lot of trust when the better days of your gear was 10000nm away.
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Old 28-07-2012, 02:40   #35
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Re: Dismasting - why does it happen, how to prevent it

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Cruisers should be just as diligent about keeping their boat in good repair as racers, and then sail their boat as best they can. I just can't think of a good reason for a cruiser to deliberately sail 1 - 2 knots slower than they can.

If the rigging is in good condition, sailing fast won't bring it down. Cruisers are destination sailors. Why take 4 hours longer than you should because you don't trust your rigging? Check it out and then go have fun!
Most cruisers I have come across tend to be very cautious sailors (inc me). Reef early, don't stress the boat, be very nice to the sails, try to avoid sailing too close to the wind etc etc. A good passage is one where nothing breaks. Doesn't matter if it takes a few days more. Just don't break anything. Fixing things isn't fun.

As for the mast thing, I had a good hunt a while ago and completely failed to find any decent data from insurance companies, just a generic "dismasted", no more exact. Would be very interesting to see more precise info. Lucky for me I have mast steps so it's a five minute job to run up the mast and check all the pins etc.
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Old 28-07-2012, 11:45   #36
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Re: Dismasting - why does it happen, how to prevent it

Quote:
Originally Posted by Stumble View Post
Sadly this is just a myth.

External chainplates are at least as susceptible to crevice corrosion as through deck ones are. Obviously the outside part of the chainplate will be fine, but the entire side pressed against the hull is in danger. It may however be easier to remove and inspect external chainplates, but unless this is done regularly it really won't matter.
....
Think you missed my point. Yes, chain plates of the same type metal will have same susceptibility to crevice corrosion, but with externals they are a lot easier to inspect...I can loosen the rig and have mine off in a matter of minutes...and they don't have as many places to trap gunk as internal plates. As I posted early, agree with the regular removal and inspection regardless of how installed.
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Old 28-07-2012, 12:02   #37
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Re: Dismasting - why does it happen, how to prevent it

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Originally Posted by Factor View Post
When talking about composite chain plates :

No probably not there for production builders, except where there is a specialist need - eg corsair, but certainly are there for custom builds, There are plenty of boats with plenty of hard fast ocean miles on them and indeed plenty of years that have composite fittings and are doing just fine. Indeed if if was talented enough to build my own boat I would be very keen to go composite fittings.
No doubt about it. Composite chainplates are great, and they eliminate the water intrusion problem once and for all. The concern I have with them (other than construction issues) is that fiberglass has a very definite fatigue life. There are only so many cycles you can put into them before the fibers themselves start to break, and the laminate breaks down.

I don't know (there may be and I just haven't seen the data) that there have been any long term testing of composite chainplates that will indicate when this will occur. It may be 20 years from construction, 100,000 miles, ect, but it is there, and without a good way to determine when it might be, I am hesitant about them in cruising boats. Racing boats have a completely different expected life span, so no worries there.
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Old 28-07-2012, 13:47   #38
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Re: Dismasting - Why does it happen, how to prevent it

External chainplates are just as, if not more prone to crevice corrosion than through deck ones. On my old W32, had to get a survey for insurance purposes when the boat was about 5 years old. Surveyor reccomended replacing the 304 chain plates or at least pulling them and doing a dye check. I thought it was a stupid reccomendationv as they looked as good as new. Needed the insurance so had to bite the bullet and comply. Two of the six chain plates had pitting at the top of the hull where the cap rail was and were candidates for crevice corrosion. Didn't dye check them as the pitting was bad enough for me to lose confidence and feel I needed to change the whole lot. Talked with the surveyor later and he said he found that external chainplates are very prone to crevice corrosion possibly because they are regularly soaked in salt water. Put on new 316 chainplates which seem to be doing fine afer more than 25 years. Interestingly, welded tang fittings for boomkin that are just above the water line and the stainless gudgeons and pintles which also have some welds that people told me would fall apart from corrosion in no time, are still okay after nearly 40 years.

For most boats, pulling the chainplates isn't all that big a deal. The difficulty comes if they are embedded in fiberglass knees. Of course those are the ones that are most prone to crevice corrosion in the first place. Any leakage of water will introduce the electrolytes and the fiberglass will keep oxygen away which makes them prime breeding grounds for crevice corrosion.
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Old 28-07-2012, 13:53   #39
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Re: Dismasting - why does it happen, how to prevent it

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Originally Posted by TeddyDiver View Post
4 days, not hours, anyway if you talk about cruising.. And there's a good reasons like chafe and wearing. Sails get double the life span if not driven too hard. Same goes with other gear in running rigging. That might not be a problem staying few days sailing away from good chandlery and sailmaker. Four months away you need a lot of trust when the better days of your gear was 10000nm away.

If I were sailing such a long distance I would have spare sails. I don't know any long-distance cruisers who don't.

The longer you're at sea, the longer you are away from things like medical help if you need it. I bought a boat that goes fast, and I like to sail her fast. I'm not interested in twiddling along. I really don't think that 7 knots puts that much more wear and tear on my sails than six, and five is ... absurd if I can do seven.
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Old 28-07-2012, 13:53   #40
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Re: Dismasting - why does it happen, how to prevent it

Lagoons have polyester mastheads sheaves , and the design have lets say a large gap between the top and the sheave , allowing the mainsail halyard to jump from the sheave and stuck in the gap if you let the halyard flog when droping the main or with the halyard without tension, this happen to me 2 times in 2 diferents lagoons when making both deliverys.

Hmmm ... hasn't happened to me yet and the halyard often flogs when dropping the main ... will have to keep that in mind ... thanks
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Old 28-07-2012, 13:54   #41
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Re: Dismasting - Why does it happen, how to prevent it

When crossing the Indian Ocean lately on a 50' catamaran, we arrived in Cape Town only to find that a few more minutes out at sea would have cost us our mast. It was pure luck that we made it safely even after close inspection of the mast and rigging before leaving Australia. The problem was an error/laziness of the rigger who installed the stays (the boat was almost brand new). Instead of inserting a 6mm screw to keep the toggle from opening, he drilled and threaded a 4mm screw (it's much easier of course).
Close inspection of every detail of the mast and rigging is essential for safe sailing in any conditions. Strain signs and cracks/micro-cracks can be identified using a strong magnifying glass.
In addition, replacement of the stays at regular intervals or according to usage is a first step to keeping your mast up where it should be.
Keeping the right loads on the rigging is a definite step 2.
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Old 28-07-2012, 13:55   #42
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Re: Dismasting - why does it happen, how to prevent it

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Originally Posted by conachair View Post
Most cruisers I have come across tend to be very cautious sailors (inc me). Reef early, don't stress the boat, be very nice to the sails, try to avoid sailing too close to the wind etc etc. A good passage is one where nothing breaks. Doesn't matter if it takes a few days more. Just don't break anything. Fixing things isn't fun.

As for the mast thing, I had a good hunt a while ago and completely failed to find any decent data from insurance companies, just a generic "dismasted", no more exact. Would be very interesting to see more precise info. Lucky for me I have mast steps so it's a five minute job to run up the mast and check all the pins etc.

I certainly agree with reefing early. It makes all kinds of sense. but I sail on the point that will get me where I want to go the best. I don't expect my sails to last forever.
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Old 28-07-2012, 13:56   #43
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Re: Dismasting - why does it happen, how to prevent it

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Originally Posted by Rakuflames View Post
If I were sailing such a long distance I would have spare sails. I don't know any long-distance cruisers who don't.

The longer you're at sea, the longer you are away from things like medical help if you need it. I bought a boat that goes fast, and I like to sail her fast. I'm not interested in twiddling along. I really don't think that 7 knots puts that much more wear and tear on my sails than six, and five is ... absurd if I can do seven.
To the contrary, I feel my boat is 'lighter' at faster speeds and can feel the force come off the rigging ... of course a different scenario if the boat ever 'slams' or comes to an abrupt halt for some reason or other and for that reason we rather reef down to keep the 'power down' but the speed up as much as possible
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Old 28-07-2012, 14:35   #44
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Re: Dismasting - Why does it happen, how to prevent it

Is there anyone with experience of unstayed masts with something to share with regard to dismasting?

I'm planning on unstayed steel masts, and was considering instead of the deck penetration at deck level, to weld a standpipe to the deck so the top is about 4 feet off the deck. This would keep it out of most of the deck wash, provide a handy and solid attachment point for winches and blocks, and de-stress the mast both from attachments at the area of most stress, and also decrease the leverage between keel-step/collar. Since the unstayed mast experiences only bending moments from sails and wind, and depowers the sail by bending in strong gusts, I expect the only reason my masts will fail is if I get slack on maintenance, a material or construction defect, or a humdinger of a rollover/pitchpole. What say you?
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Old 28-07-2012, 14:56   #45
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Re: Dismasting - why does it happen, how to prevent it

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To the contrary, I feel my boat is 'lighter' at faster speeds and can feel the force come off the rigging ... of course a different scenario if the boat ever 'slams' or comes to an abrupt halt for some reason or other and for that reason we rather reef down to keep the 'power down' but the speed up as much as possible

"To the contrary?" The boat would slam or come to an abrupt stop in the open sea?

Yes, reefing when needed is faster than not reefing when needed. There will also be less sideslip or leeway, and the ride will be more comfortable.

I think you think we're disagreeing when we're not.
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