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  #1  
Old 09-20-2008
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Rebeding Chain plate deck penetrations

Seeing how winter weather patterns are starting to stare down our necks here in the PNW. I thought it a good Idea to re-bead my deck penetrations starting with my standing rigging.
I have 8 total rigging chain plate penetrations at the toe rail so I started here, I have know idea if this had ever been done to my boat before as you can see in the first picture the caulking is shrunk and indented below the covers allowing water to at least pool if not leak. Several of the 8 were still fairly gooey upon lifting the covers but several were fairly dry and flaky but yet still sort of elastic . There is evidence of water marking in a couple locations below deck so this definitely needed done.

This project took about 3 1/2 hours is all, and two good beer breaks ie: back breaks, were in that time frame also so if you have been puting it off DONT! it is so simple to do.

Tools and Materials I used were ..Cordless drill, flat blade screwdriver, pocket knife, wire brush and some emery cloth, Life Caulk and a couple paper towels...( some of you anal types will wipe the area first with some sort of solvent but I didnt bother with that step as the wire brushing and emery cloth took care of any contaminants.

I had a small tube of Life caulk so I used that. I would have used 3M 101 if Id had an open tube but was not going to open a large tube @ 24.00 for such a small project, I have seen other 3M sealents in small tubes but not 101 which I can not under stand so if you know a source please post it.

Here is an Original, as you can see the caulking is shrunk below the cover allowing water to pool even if it cant or dosent leak.


After removing the 4 cover screws and prying up with the flat bladed screw driver you can see that this particular one was still fairly gooey and elastic which is a good thing..However several were not this way and the cover basically popped right up..on these ones several of the screw holes were compromised and wet due to poor sealing.


After removal of all old sealant and wire brushing and sanding the area we're ready to re-bead..I also took the opportunity to inspect for any crevice corrosion, stress cracking or other imperfections as best I could given the small window of inspection such as it is.



I applied a good slathering of life caulk making sure contact was made all way around the chain plate and a good dab on all screw holes. I had misplaced the hand dandy nossal the comes with each tube of Live caulk which would have helped direct the caulking placement better but got the job done anyway.



I then lowered the cover in place and hand set each screw to center everything up so as not to smear the stuff all over the place.



Tightened everything down and moved on to the next one...Now here again you perfectionist types are going to wipe off this apparent extra bead of caulking off to give it that fine finished look..but I feel this extra squish out is a benefit to be left in place as no way can water pool up and be trapped...who looks there anyway?


Last edited by Stillraining; 09-20-2008 at 05:38 PM.
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Old 09-20-2008
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I would prefer if those screws were thorough-bolts and that the surrounding glass was solid and not cored, which I hope is the case. Having an old C&C, I am paranoid about deck coring, and do the "drill and fill" at any opportunity, especially since I tore out the port genoa track due to core rot...

Other than that...good job! Now, tighten your chain plate bolts at the knees! I do this every year and I always get about a quarter-turn of play (4 bolts per plate...two ratchet wrenches make the job very quick!).
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Old 09-20-2008
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Argh! Great pictures of the #1 cause of death for Good Old Boats! This just makes me angry, that boat designers are so bad that they do this kind of crap.

Some years ago I did research on sealing aluminum tracks to concrete. What I found out is that Silicone is the sealant of choice for this task, hands down. A properly applied silicone seal will move + or - 100% in compression, tension, and shear! Note that this is 100% of the thickness of the sealant. That means that if the chainplate passes tightly through the deck then the sealant thickness will be minimal to nonexistant. It also means that ANY motion of the chainplate will break the seal! There are boats out there with chainplates that do not move I would guess, but not that most of us can afford.

If you can't keep the chainplate from moving then the obvious answer is to make the sealant thick enough to allow the motion without breaking. So simply opening up the deck all around the chainplate to 1/4" or 3/8" and filling the gap with silicone will allow the chainplate to move up, down or sideways 1/4" to 3/8", and never break the seal! To keep silicone from leaking below while it cures you simply stuff the bottom of the gap with the foam backer rod made for this purpose.

Oh, and that cover plate? What a STUPID idea! Lets add some screw holes to leak too. And while we are at it, let's SHEAR the sealant right off the chainplate as it moves!

Finally, you've done all this work. How do you KNOW you still don't have a leak? One way that is easy and pretty fool proof is to use Joy dish washing detergent in a spray bottle, and look for air bubbles on the outside of the boat. To generate air pressure inside the boat just close all the hatches and vents, and install a piece of plywood in the companion way with a hole for a big shop vac hose, or a better yet a leaf blower. You can check every fitting on your boat in about an hour.
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Old 09-20-2008
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Quote:
Originally Posted by GaryHLucas View Post

Finally, you've done all this work. How do you KNOW you still don't have a leak? One way that is easy and pretty fool proof is to use Joy dish washing detergent in a spray bottle, and look for air bubbles on the outside of the boat. To generate air pressure inside the boat just close all the hatches and vents, and install a piece of plywood in the companion way with a hole for a big shop vac hose, or a better yet a leaf blower. You can check every fitting on your boat in about an hour.
Good idea...
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Old 09-20-2008
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Whats the best way to go about this if there is no little plate around the chainplates? All 3 of mine are in lined up with the mast and all go through a big hole cut in the deck. Its a crappy way to do it, but thats how it was done long before i got the boat. Ive got to figure out a way to reseal them one ive got the bulkhead replaced. You can see how they enter the deck in the picture. The hole is all goobered up with 5200.

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Old 09-20-2008
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I have exactly the same chainplate setup on my boat. I actually was able to pull all (or most anyway) of sealant from around the chainplate going through the deck and even file the sides of the hole slightly wider - then seaed it back so that sealant went back into the deck and down below, as well as above.

The deck around is solid, of course - so no issues with core.

Here is what it looks like cleaned up:


Sealed (you can see where old gunk used to be all over the place)
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Originally Posted by SVDistantStar View Post
Whats the best way to go about this if there is no little plate around the chainplates? All 3 of mine are in lined up with the mast and all go through a big hole cut in the deck. Its a crappy way to do it, but thats how it was done long before i got the boat. Ive got to figure out a way to reseal them one ive got the bulkhead replaced. You can see how they enter the deck in the picture. The hole is all goobered up with 5200.

Bummer man...I think people should have to pass a test to buy 5200.. it is probably the most abused 3M product out there. OK stuff for the right application. Your probably gong to loose your gel coat trying to get that stuff off
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There is no gelcoat there. Thats grey paint for cement floors.

Yea the PO of my boat must have had stock in 3M since there are about 50 tubes onboard when i bought the boat. I spent at least 2 hours trying to remove the 5200 that was around the bottom of the mast where it comes through the deck. For some reason they tried to seal the hole around the mast from the bottom and not the top. Im lucky that the core isnt rotten.
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Old 09-20-2008
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Having dealt...

Quote:
Originally Posted by GaryHLucas View Post
Some years ago I did research on sealing aluminum tracks to concrete. What I found out is that Silicone is the sealant of choice for this task, hands down. A properly applied silicone seal will move + or - 100% in compression, tension, and shear! Note that this is 100% of the thickness of the sealant. That means that if the chainplate passes tightly through the deck then the sealant thickness will be minimal to nonexistant. It also means that ANY motion of the chainplate will break the seal! There are boats out there with chainplates that do not move I would guess, but not that most of us can afford.

If you can't keep the chainplate from moving then the obvious answer is to make the sealant thick enough to allow the motion without breaking. So simply opening up the deck all around the chainplate to 1/4" or 3/8" and filling the gap with silicone will allow the chainplate to move up, down or sideways 1/4" to 3/8", and never break the seal! To keep silicone from leaking below while it cures you simply stuff the bottom of the gap with the foam backer rod made for this purpose..
Feel free to sue silicone on your boat but having worked in boat yards and having owned over 20 boats of my own I can assure you silicone is exactly the worst product to use for chain plates for exactly some of the reasons you point out such as movement.

Silicone permeates the gelcoat and permanently pollutes & contaminates it so that nothing will stick to it in the future, not even 5200 successfully. Short of grinding and sanding the surface and silicone residue away there is virtually nothing you can do. It may look clean, and you've even washed it with acetone, but hmmmm it's still beading water??

There are also no commercially available chemicals to safely strip silicone from fiberglass or gelcoat without causing damage. If there was such a product someone would be very rich as my boat yard alone would buy two 55 gallon drums in a heart beat!! The ill effects and future problems associated with silicones use is documented in reports all over the sailing/web world and by those of use who have extensively worked on boats where owners used silicone.

There are very few good uses for silicone on boats due to it's profuse contamination of the surface and it's low adhesion properties. It also does not like to stick to stainless steel so in a chain plate it really is an overall poor choice.

Better choices for chain plates would include:

Sikaflex 291 = 220psi or 3M 4200/UV4000 = 300psi or 3M 101 or Life Caulk = Both about 140 PSI adhesion

I personally prefer 3M 101 due to it's natural UV resistance and ease of removal for future re-beddings. It also sticks to stainless steel very well when compared to silicone. My second choice, and one I've used many times, is Sikaflex 291. For a one part poly it has surprisingly good UV resistance and a good bond to stailnless.

Here's a quick run down:

3M UV 4000 is a one part polyurethane with UV inhibitors added. It has a elongation before break of 800% and a tensile strength of 300 PSI.

3M 4200 is a one part polyurethane with NO UV inhibitors added. It has a elongation before break of 900% and a tensile strength of 300 PSI.

3M UV 4000 is basically, spec wise, 4200 with UV inhibitors added which reduces is elongation before break slightly. This should NOT be a concern as 300 PSI is much more than necessary anyway.

3M 101 is a one part POLYSULFIDE! Polysulfides have a natural UV resistance and are the premier product for use in teak decks where UV rays bash them day in and day out. Polyurethanes do not do well with UV so UV inhibitors are added. 3M 101 has a tensile strength of 139 PSI and an elongation before break of 416%. Polysulfides are not compatible with some plastics.

Sikaflex 291 is also a one part polyurethane with a preferred lower adhesion than UV 4000 or 4200.. It offers an elongation at break of roughly 600% and is the easiest one part polyurethane sealant to get off in the future at roughly 221 PSI!

3M Marine Silicone offers the lowest adhesion of any 3M sealant and also the LOWEST elongation before break of any of the marine rated 3M sealants. 3M 4200 and 3M UV 4000 for example offer nearly double the flexibility before separation/break than does 3M Marine Silicone. 3M Silicone also has a very weak bond to metal and is only suggested for bedding or caulking metals by 3M not "adhering" to them as you actually need in a chain plate. 4200 and 4000 get an "H" rating on metal which mean they have a "High" strength bond to stainless. If the joint is moving, as chain plates do, you want a product that offers not only good elongation before break but also a decent level of adhesion to both the metal and the fiberglass. You also want one that won't have contaminated the surface for the next round of re-bedding to stick to.

So what's the bottom line? Both polysulfides & polyurethanes offer more elongation before break and adhere better to stainless than does silicone and they won't contaminate the surface for future re-beddings..

The advice about making the gap bigger around the chain plate is spot on! I bevel mine at about a 45 degree angle to get a nice thick gasket. If the deck is cored arond the chain plates remove them, dig out the core and back fill with thickened epoxy! On many production boat the chain plates are bolted to "screwed in" bulkheads, a poor & corner cutting design choice IMHO, and they WILL move!!

Again it's your boat and all I can do is present my findings & years and years of seeing silicone wreak havoc on boat decks and cores...


StillRaining,

The only thing I would add would be to slightly countersink or bevel those screw holes to create an o-ring effect of sealant. I would have also dug into the area around the chain plates and made them bigger and really cleaned the stainless chain plates al the way through the deck to get a good bond of the new 3M 101..

This hole has been countersunk and will create a nice thick o-ring of sealant around the machine screw head:
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Last edited by Maine Sail; 11-10-2008 at 09:47 PM.
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Old 09-20-2008
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Main...Do you use a dremel tool for this ? I mean you can see what kind of room I have to work in..Hind sight would have been to do this when rig was down.. I aint going there again for a VERY long time.

Oh shoot what am I thinking... I could always slack off , disconnect and do one at a time. That way getting everything out of the way....Next year maybe..Im getting close to SAILING...

Last edited by Stillraining; 09-20-2008 at 10:04 PM.
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