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Old 04-10-2010, 08:08   #1
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Chainplate Failure and Concerns

Recently found a crack in my chainplate for the aft main stay on my Morgan 416. Had two new ones made up and installed each. Opposite side was OK. I inspected all others and then went up the mast and looked at all the rigging hardware and took high definition pictures.

Some think I should pull every chainplate and this would pretty much end the season. I inspected every one and found no visible cracking like the one I found. Take a look at my link and the pix I included.

What say you ? Any expert advice or advice with experience would be appreciated. thank youMain Starboard Intermediate and Upper
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Old 04-10-2010, 08:46   #2
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I guess I would want to see what the bolts look like and what the back bedded side of those plates look like. Mine were through deck and there was crevice corrosion on 60% of the plates 1 was really bad. It was not obvious while looking at the exposed section. The damage was where the water sat trapped and unseen.
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Old 04-10-2010, 09:20   #3
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I used to be a pro.rigger. External chainplates like the ones you have rarely if ever have corrosion problems since they are exposed to the atmosphere where the properties of stainless steel keep it stainless. The one that cracked most likely had a flaw in the material itself and probably could not be detected without x-ray analisis. The factory doesn't do x-rays when they assemble the boat since this sort of thing is very rare (although I have seen it before). Chances are the rest of your ss fittings will outlive the rest of the boat,but it dosent hurt to take off the chainplates,stemhead fitting chocks etc.every 10 years or so and check them for corrosion on the backside (this is fairly common),the side that wasn't exposed to the air. When you put them back on don't forget to bed them properly. BTW
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Old 04-10-2010, 16:30   #4
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Is it OK to bed them with silicon ? Bar anything else available, I painted the backside of two new chainplate with silicon - with a heavy bead at the top to prevent moisture from running down. This OK for bedding - shoud I redo it ?
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Old 04-10-2010, 16:41   #5
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I had a similar scare from another Dragonfly owner who said he had cracks in his waterstay chainplates (diagonal SS cables under the crossbeams) emanating from the square cut holes which keep the Carriage bolt heads from turning.

I inspected all of mine by dutifully removing them (no easy feat), but all of them were just fine.
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Old 04-10-2010, 17:52   #6
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When I had my Westsail 32 surveyed after 5 years of cruising, the surveryor reccomended removing the external chain plates and inspecting them. According to him, there had been quite a few issues with crevice corrosion on the W32 external plates. I sold the boat without pulling the plates but noticed that the new owner replaced all the chain plates. Didn't talk with them to find out whether they'd done it because they'd found crevice corrosion or they were just anoraks. In any case. it seems that external chain plates are not immune from crevice corrosion.

Sillycone belongs in Boobs, not on boats. Silicone is a crappy sealant. It sticks only to what it feels like and that ain't very much. My first boat came from the factory with all the hardware bedded in Sillycone. It leaked like a sieve and spent a year R&R'ing the fittings, ports, etc. to stop the leaks. The PO on my current boat was a sillycone nut and bedded everything he did in Sillycone. Once again leaks in every fitting he touched. I've had to remove every fitting and rebed with Life Caulk, 5200, or Butyl. Unless you really don't like yourself, stay away from Sillycone.
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Old 04-10-2010, 20:04   #7
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As roverhi said, silicone is garbage! You now have a problem. The silicone leaves a residew that's almost impossible to remove. It prevents anything else (including paint and most other sealants) from adhering to the surface. Sand down the surface that has been siliconed and then wipe down very vigorously with acetone and maybe even some toluine. Take every precaution to keep these chemicals off your skin and especially your eyes, they are VERY toxic! Acetone should be the last chemicle you apply as it will remove most all others. Don't forget to clean the chainplates too since they have been affected also. Next, rebed using 5200 (or sicaflex). I don't recomend a poly-sulfide for this application. Home depot has 5200 for half the price the marine stores charge.
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Old 04-10-2010, 20:20   #8
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The key to stainless steel longevity is to be sure that the surface of the metal can "breathe", that is, it has access to the oxygen in the atmosphere. If you are going to attach it to a mated surface then you must be sure that the material you use to bed it makes total and complete contact and does not allow any water to get to the the metal in the absence of oxygen.
- - Stainless Steel does not rust like iron - it gets "intragranular corrosion" when exposed to water without oxygen. The granules/grains of the alloy loose cohesion and with advanced intragranular corrosion you can stab a screwdriver right through a 1/4" thick chain plate. I have done it when I removed one of my chainplates. And the wholesale rigging supplier I use showed me his "superman" routine by snapping a similar chainplate in half with his bare hands.
- - Keeping water away from "bedded" chainplates is a maximum priority. It is common for water to work its way into the threads buried inside a bolt/nut and then the bolt breaks with minimal force. The use of anhydrous lanolin - LanaCote or Tuffgel is important.
- - As capt.bobfm wrote cleanliness is critical prior to applying an adhesive caulk for bedding. Besides not wanting water inside the cabin or sidewalls of your boat, sealing the chain plates at the deck level is critically important to prevent intragranular corrosion and failure. Remember that the chain plates will be constantly moving/flexing when underway so whatever you use must adhere and be flexible enough to move with the plates without tearing loose.
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Old 04-10-2010, 20:27   #9
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On the original question. If you are thinking about the condition of the chainplates, or any structural part for that matter, you'd best schedule an inspection. Maybe not during "the season", but soon. For your mind if nothing else.
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Old 15-10-2010, 11:54   #10
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This is what could happen if you don't inspect all that rigging...

Anyway, here's a link Bash posted on the Forestay Failure - Chainplate Failed forum.

I found it very informative (after the fact, unfortunately!):
BoatUS.com - Seaworthy Magazine
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Old 15-10-2010, 12:18   #11
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Does not look like it was only the plate.

b.
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Old 15-10-2010, 12:27   #12
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I am always learning something here.
1-Bash can get scantily clad women onto his boat even when the rig has collapsed.
2-Sicaflex can be mistaken for explosive at the airport.
3-I need to look into Idora's chain plate fasteners.
4-Silicon belongs in computers and boobs!

Not a bad day's harvest from CF.

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Old 15-10-2010, 12:29   #13
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I pulled all my 30 yo external chain plates during my refit.
One was cracked and a third of the bolts were completely broken.
It was only due to being over built/bolted that I didn't loose a chain plate.
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Old 15-10-2010, 13:33   #14
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Yes it is a useful forum but one correction: Silicon does indeed go in computers but siliconE is what you too often find in boobs. Must admit I'm a bit old fashioned and prefer the natural product not something pumped up with additives.
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Old 15-10-2010, 15:11   #15
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love the look of her silicone seeping out her forehead. i will never forget that one.
comes into ER wondering what the bump on her forehead was. silicone.
stuff isnt even good in boob jobs.
5200 is not the substance of choice for bedding anything-is a glue not a bedding compound.. mebbe it is what we need on out leaky teakies for the chain plates, but i dunno-- i dont use the stuff. 4200is superior for bedding and so is silkaflex and lifecaulk. mebbe we need glue on our internal chainplates? please give me the pros and cons of usin gglue over bedding compound in this application??
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