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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 10-27-2008
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Leaking Chainplate

Iíve removed a leaking chainplate and found as suspected some water incursion into the foam core of the deck. I plan on filling this void with thickened epoxy as I have done previously on other hardware. My problem is the somewhat rectangular hole through the deck cut by the manufacturer is a hack job. It is irregular in shape and on one side it is as much as ĺ of an inch away from the plate location. I want to make the hole smaller and cleaner. Iím not sure how tight I should make it to the plate and exactly how to fill in the voided area or fill it all in a cut a new hole. Any ideas would be appreciated.
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Old 10-27-2008
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We just had the chainplates rebedded and the core around them replaced w/ thickened epoxy on the club boat of which I am boat captain. Basically they cut out a rectangle that was covered by the flat plate that screws down over top of the chainplates, NOT going through the underside of the deck (or the cabin liner!) and filling it in. Then cutting out a new slot for the chainplate to fit up through.
I would make a template (out of masonite or mylar or whatever) that fits over or against your chainplate so you can mark its exact location, remove everthing, fill w/ High Density thickened epoxy and then mark the location for the slot.
You want it as snug as possible. 3/4" slop is unacceptable!
While 5200 is what is going to seal it up, and it does dry hard, you want as little "wiggle room" as possible. Kind of like doing trim work in your house; you want the wood to fit as tight as it can and NOT rely on caulk to make it look right. Make sure you bed everthing well, put a bead around the screw holes and a dab on the underside of the screw head.

Oh, as far as cutting the deck out around the chainplate, a tiny reciprocating circular saw is the thing to use! The blade just oscillates, doesn't spin. As far as cutting the slot, use an appropriate sized drill bit to drill a hole at each end of the slot, then a saber saw to connect the holes.

Any ?'s drop me a note.

Last edited by sailordave; 10-27-2008 at 10:15 AM. Reason: typo
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Old 10-27-2008
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Try putting plastic food wrap around the acual chainplate and inserting in place prior to filling with thickened epoxy. The epoxy will not adhere to the plastic wrap and afetrwar you should be able to remove the chainplate.

I wonder on teh advisavility of 5200 for this job as a sealant though. Firstly it is not very flexible when sealed and the chainplate constantly moves. Secondly 4200 is a better choice as it is easier to remove fittings if necessary afterward than 5200 - 5200 is a tad strong for this job. You might even consider butyl tape or something flexible. While I have always used 4200 for this job I am sure on this list you will get advice on a more suitable product for sealing.

Mike
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Old 10-27-2008
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Always use a polysulfide sealant for the chainplates, I use 3Mô Marine Sealant 101, but there are others. If you went with 5200 and for any reason needed to pull the chainplate and reseal, it would be much more difficult job.
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Thanks for all the advice. I WAS considering some sort of release material on or around the chainplate and leaving it installed as was suggested. As long as I can get the plate out again, this would seem to give the best fit. Mikehoyt, have you used the food wrap is this way and did it release ok?
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I cannot recall if I used plastic wrap on the chainplates or if I used something else. I do recall using Cling Wrap or similar on many occasions to prevent epoxy from adhering to other surfaces and it did work well.

Mike
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Old 10-27-2008
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Great! Then that's what I will do. Thanks again for the advice.
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Old 10-27-2008
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Be very careful with that advice!!!!

Quote:
Originally Posted by sailordave View Post
You want it as snug as possible. 3/4" slop is unacceptable!
While 5200 is what is going to seal it up, and it does dry hard, you want as little "wiggle room" as possible. Kind of like doing trim work in your house; you want the wood to fit as tight as it can and NOT rely on caulk to make it look right.

NO, NO, NO !!!!!! I'm very sorry but when I see advice that can cost you in the future I must address it.

#1 The bulkheads, deck and hull will move and flex at different rates to each other especially if you own a production boat with "screwed" bulkheads. This is very common, and known, and it's why builders leave a gap to begin with. Unfortunately the majority of these hole are poorly done, as noted in the OP, and can quite often be dramatically off center leaving one edge, or corner, fitting tightly against the deck with another side seeing a 1/4" or more gap. Guess where the leak failure will be? That's right, it will be at the "tight spot", not at the spot with a good thick bead. The harsh reality here is that you can not compare a sailboat, under extreme loads, in 30+ knots of wind & 10 to 12 foot seas, to the trim boards in your static & stationary house. Chain plates move independent of the deck on many, many boats. If they did not we would not have all the leaking problems we do.

#2 While 3/4" is way to much of a gap, and I fully agree with SailorDave on this, the last thing you want is a tight tolerance fit or "you want as little "wiggle room" as possible". Why? Well for starters read #1. Secondarily all marine sealants have what's called an elongation before break rating. Exceed this rating or allowble movement and it fails. The thinner the bead of sealant the less allowable flex you will be allowed before an elongation before break failure. Lets say the chain plates move 1/8th of an inch at their max movement under high stess load. Many times it's can actually more than that, especially with screwed in bulkheads. Now lets assume you have only a 1/32" inch gap around the chain plate. The allowable flex of the sealant will not hold up because your bead is too thin and you are flexing beyond the capabilities of the sealant for the applied thickness.

#3 You want at least an even 1/8", minimum, around your chain plate to avoid sealant elongation before break failure. Even a little more is better, especially with non-tabbed bulkheads, as it will be able to flex more. A 400% elongation before break of 1/32 is far less allowable movement than 400% of 1/8" or more..


Here are a few considerations and photos:

.

#1 Over bore the chain plate holes to at the very least 1/8" on all sides where it is "close" to the deck edge. If a sealant will flex 400%, and the chain plate is right up tight against the hole giving you only 1/32" your chain plate can flex double, tipple or quadruple the amount if you go with a bigger bead gap. The thicker the sealant you have, within reason, the more flex will be allowed. Again 3/4" or even 1/2" is far to much. Many times these holes are not lined up right from the factory, as noted above, and this leads to failure due to an insufficient flex gap. (See Photo)
In the photo bellow (This is NOT my photo and it is hot linked from the C-34 web site) the gap on the left side is sufficient but the gap on the right will fail earlier due to less allowable flex. The deck hole was made off center of the chain plate and this is not good. The sealant gap should be even and equal around the entire perimiter.



#2 After you're done potting the hole with epoxy and making an equal gap all the way around, use a laminate trimmer with a 45 degree bearing guided bevel bit, to chamfer the top of the hole slightly. This gives the stainless deck cap more of a o-ring effect and a thicker "gasket" at deck level around the chain plate. (See photos bellow)

#3 The easiest way to make an even gap all the way around the chain plate is to wrap the chain plate in 1/8" or more of duct tape. It works perfectly and builds up fast and evenly. Once you've wrapped the chain plate to a sufficient gap or bead thickness simply wax the duct tape with a carnuba wax, install the chain plate and tape off the cabin side to prevent epoxy dripping into the cabin. Now simply pour your thickened epoxy around the chain plate and let it cure. Next, remove the chain plate and un-wrap the duct tape and you'll have a perfectly centered chain plate with an even perimeter gap. Don't forget to chamfer the deck side in step 2 above.

45 Degree Bearing guided Bit:

Approx Depth of Bit:

A Beveled Fastener Hole:


#4 I strongly advise against sealing anything on the inside of the boat and I vary from a few of the so called experts, such as Vaitses, on this point & with good reason.

Why should you seal only from the top/deck side?

If you develop a leak on the deck side you WANT to know about it asap. If you purposely seal the backing plate side or bellow deck side of a fitting the water will inevitably get trapped in between the top and bottom if a leak develops at deck level. In all my years of boating I have yet to see a leak originate on the dry underside of the deck. Any water that can't drain out, and be seen to effect a repair, can lead to either crevice corrosion of the chain plates or further deck damage if you did not pot the holes with epoxy. By not sealing the backing plate side of a fitting it will allow any leak to be seen and not forced into the deck or left trapped there, starved of oxygen, creating unseen and un-safe crevice corrosion of the through bolts or the chain plate itself.. It is IMPORTANT that a leak on the top side be allowed to leak through so you can address it!!

P.S. Do yourself a favor and do not use 5200 or silicone for this job. 5200 bonds to fiberglass at a PSI that is actually stronger than the gelcoat bond. You don't need or want anything with more than 200-300 PSI bond strength and the 140 PSI of 3M 101 is more than adequate. Use a good polysulfide like 3M 101 or a lower bonding polyurethane such as Sikaflex 291 or 4200 if you must use a polyurethane. The benefit of polysulfides is that they are far more UV resistant and stay flexible longer when exposed to UV. Personally I use butyl tape in gray or off white but it's hard to find..
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Last edited by Maine Sail; 10-27-2008 at 04:48 PM.
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Old 10-27-2008
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While I have no doubt that Halekai's method would result in a dry boat, I did mine a little differently, and I too have a dry boat. The use of any method for sealing chainplates may be affected by the chainplate design and thickness of the chainplate itself. My chainplates are thinner steel than the ones pictured above, and I have one mounted on an odd bracket that attaches to the bulkhead about 6 inches away.

I don't have pictures so I'll do my best to describe them properly. I have 3 chainplates on each side of the mast. The forward one never leaks, so we don't need to talk about it. The aft chainplate is a flat piece stainless, it is bolted to the aft side of the center bulkhead and protrudes through the deck. The center chainplate is part of an odd bracket that bolts to the forward side of the bulkhead and shares the same bolts as the aft chainplate. Needless to say, this arrangement has a lot of leverage on the center chainplate and causes the whole mess to move a lot in relation to the deck.

I tried multiple times to seal this mess, with poor results. I will say that I used 4200 on the advice of people here and the owner of the one and only local sail shop. IMO 4200 is a poor choice. It doesn't flex enough. In fact, I would say it flexes less than 5200, but I wouldn't use that either.

The fix went as follows: I removed the offending chainplates on both sides. I used an air powered die grinder with a rotozip DC1 bit in it. The spiral cut rotozip bits will not do the job, get the DC1. I ground out the slots in the deck to remove any old sealant that was hiding in there, and opened up the core beneath the outer deck skin as much as I could. Be careful not to exceed the size of the cover plate. Then I coated the chainplates with Johnson's paste floor wax to act as a release for the epoxy. I temporarily reinstalled the chainplates. I taped off the bottom of the chainplates to prevent epoxy pushing through then I injected thickened epoxy into the chainplate slot.

When the epoxy dried I removed the chainplates. I used my DC1 bit to create a small "dish" in the epoxy around the chainplate hole.The chainplates were then reinstalled and bolted down tight. In the dish that I created, I packed butyl tape around the chainplate. Then I reinstalled the covers.

The butyl tape remains flexible, and even if it were sheared off the chainplate due to movement, it would reseal itself. It worked for me.
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Old 10-27-2008
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Quote:
Originally Posted by US27inKS View Post
I used my DC1 bit to create a small "dish" in the epoxy around the chainplate hole.The chainplates were then reinstalled and bolted down tight. In the dish that I created, I packed butyl tape around the chainplate. Then I reinstalled the covers.

The butyl tape remains flexible, and even if it were sheared off the chainplate due to movement, it would reseal itself. It worked for me.
No argument from me I use butyl almost 100% exclusively. The only way to get butyl to seal extremely though is with a chamfer as you described you did. The chamfer or bevel forces the butyl into the gap, and compresses it around the chain plate, as the cover plate is screwed down.

You can also create a bottom deck plate installed inside the boat with a bigger gap around the chain plate to allow for your movement. You then over fill the gap with butyl and then bolt the cover plate down onto it compressing the butyl to seal around the chain plate. Butyl is many, many times more flexible than any of the polyurethanes or polysulfides. I rarely mention it because so many are brainwashed into believing products like 5200, 4200 or Life Caulk are the only way to go.

Our boat was built in 1979 and everything, including the hull/deck joint/toe rail, was bedded with butyl. Nearly 80% of the boat remains un re-bedded and does not leak.

My chain plates are bedded with butyl too. You can get away with a smaller gap with butyl because it is sooooo much more flexible..

If you are going to use a polyurethane or polysulfide it's still best to both widen the gap and bevel the deck side..
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Last edited by Maine Sail; 10-27-2008 at 04:46 PM.
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