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Go Back   SailNet Community > On Board > Gear & Maintenance > LifeCaulk vs. 3M 4200
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Thread: LifeCaulk vs. 3M 4200 Reply to Thread
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Topic Review (Newest First)
05-30-2013 10:33 AM
asdf38
Re: LifeCaulk vs. 3M 4200

Quote:
Originally Posted by gedaggett View Post
Dow Corning 795 is a great product. I have used it on everything from retrofit polycarbonate windows on Catalina 30 (no fasteners just the adhesive) to sealing the mast, chainplate, deck cleats. It is very versatile and unlike the 3M products doesn't require etching or scuffing on polycarbonate or acrylic materials. Great product. (disclaimer: I have no vested interest in Dow Corning)
I'm curious what other people say but I think the issue with Dow 795 is that it's silicon based and therefore has the contamination and other issues associated with that. This is what sailingdog said in his well known sealant post:

Quote:
Originally Posted by sailingdog View Post
Silicone-based sealants aren’t really sealants IMHO. They’re really gasket materials, and need to have a minimum thickness and be kept under compression to work properly. Silicone-based sealants should only be used in above-the-waterline applications.

The only structural silicone sealant that I generally recommend is Dow 795. This is a structural adhesive which is generally recommended for bedding ports. It is not your common silicone caulk. However, beyond the very specific use of bedding acrylic* ports, it should not be used on boats.

Aside from bedding acrylic and polycarbonate ports, and certain plastic parts, like Beckson ports, and covering the exposed ends of cotter pins—it really has no place on a boat—primarily due to the residual silicone contaminants silicone can leave behind. These contaminants are almost impossible to remove thoroughly, and will prevent other sealants and paints from adhering to the surface properly. Even strong adhesives, like epoxies, have trouble bonding if the surface has silicone contaminants on it.

One other use of silicone is for sealing potable water tanks. However, I highly recommend that you use only NSF approved silicone sealants for potable water tanks and systems. These will not have any toxic components, unlike some of the other marine-grade sealants which may contain isocyanates.

Some silicone sealants are acid-curing and should never be used on metal. These are generally easily detectable by the strong vinegar smell caused by the acetic acid that is contained in them.
http://www.sailnet.com/forums/gear-m...tml#post479453

That said, if Dow 795 is as strong as described, I'm not sure why exactly it's not suited for other tasks, assuming you don't care about the contamination issue. And I'm not sure why you would if you planned to use Dow 795 or other silicon going forward.
05-30-2013 09:49 AM
gedaggett
Re: LifeCaulk vs. 3M 4200

Dow Corning 795 is a great product. I have used it on everything from retrofit polycarbonate windows on Catalina 30 (no fasteners just the adhesive) to sealing the mast, chainplate, deck cleats. It is very versatile and unlike the 3M products doesn't require etching or scuffing on polycarbonate or acrylic materials. Great product. (disclaimer: I have no vested interest in Dow Corning)
05-28-2013 10:57 PM
Sabreman
Re: LifeCaulk vs. 3M 4200

I think that the answer to my question is:

Quote:
that the butyl is in compression, (really packed in)

Quote:
By the way, that diagram is GOLD!
I have an entire 1" thick book of diagrams and specs from Sabre. They have the best user's manual that I've ever seen. I scanned them and have them on the iPad for fast reference. I also have the one from our Sabre 28. If anyone wants it, PM me.
05-28-2013 08:54 PM
MastUndSchotbruch
Re: LifeCaulk vs. 3M 4200

Quote:
Originally Posted by asdf38 View Post
But you do have a deck core (I assume) and water can run inside that. So it's possible.

That said, chainplates are high on the list of things that leak on a boat given the geometry and the amount of flexing they do. So if you have a chainplate leak it probably really is the chainplate. But you never know.

Also, what about those screw holes? A leak in the screw hole could come out the chainplate inside.
In principle, it could be the deck. But what are the chances that it leaks JUST around the two chainplates?

The screws do not go through and they are potted in epoxy.
05-28-2013 06:35 PM
asdf38
Re: LifeCaulk vs. 3M 4200

Quote:
Originally Posted by MastUndSchotbruch View Post
Good point but there is no liner in my boat at this location, right at the toe rail. Just the bare deck...
But you do have a deck core (I assume) and water can run inside that. So it's possible.

That said, chainplates are high on the list of things that leak on a boat given the geometry and the amount of flexing they do. So if you have a chainplate leak it probably really is the chainplate. But you never know.

Also, what about those screw holes? A leak in the screw hole could come out the chainplate inside.
05-28-2013 06:13 PM
MastUndSchotbruch
Re: LifeCaulk vs. 3M 4200

Quote:
Originally Posted by Maine Sail View Post
I would be checking for "tracking leaks". These are leaks that track through the deck or between the deck and liner and come out at an area that is not at all where the water went in.
Good point but there is no liner in my boat at this location, right at the toe rail. Just the bare deck...

Quote:
Originally Posted by Maine Sail View Post
If the deck has been potted care must be taken to make sure there is minimal to no movement in the chain plate and that the butyl is in compression, (really packed in) if using butyl....
That is actually why I went to the Lifecaulk, because I thought that the puny screws holding down the cover plate would not really put anything in compression. I rebedded the cleats with the butyl tape, where the through-bolts put down a lot of force, and haven't had any issues there. I thought the slightly adhesive character of Lifecaulk might help in this case but, as I said, it did not really.

So I will definitely add the groove but am still not sure if I should use butyl or Lifecaulk.
05-28-2013 06:09 PM
asdf38
Re: LifeCaulk vs. 3M 4200

Quote:
Originally Posted by Maine Sail View Post
I would be checking for "tracking leaks". These are leaks that track through the deck or between the deck and liner and come out at an area that is not at all where the water went in.

I had a boat seven weeks ago that had a leak over the nav station. Owner re-bedded everything within a 5' radius of the nav desk. Still had a leak. I happened to notice a slight dampness behind a hanging locker around a screw and the leak was traced to the forward port light. Rebedded that port and the problem went away... Water was tracking all the way from the forward port light to the nav desk before it found a means of egress into the boat. Chainplates are a great area where tracking leaks occur if the deck has not been potted.

If the deck has been potted care must be taken to make sure there is minimal to no movement in the chain plate and that the butyl is in compression, (really packed in) if using butyl....
Thanks above.

I'm hoping I have a tracking leak right now from the chainplates to a stanchion base that I rebed last year. I'm hoping that rebedding the chainplates eliminates the leak.

Part of the reason I think that's the cause is that the PO sealed this chainplate from the inside, trapping the water inside the deck where it ran to the nearby stanchion hardware.

Never seal from the inside.
05-28-2013 05:59 PM
Maine Sail
Re: LifeCaulk vs. 3M 4200

Quote:
Originally Posted by MastUndSchotbruch View Post

I have rebedded them thrice, first with RV-style butyl tape, then with the one-and-only Mainsail tape, then (in desperation) with Lifecaulk. Each time somewhat chamfered at the top but still leaking. I will make a fourth effort after cutting the whole thing open again and this time leave a 3/8" groove around the chainplate.

Will wait for the outcome of this discussion to see what to actually put in the groove.

I would be checking for "tracking leaks". These are leaks that track through the deck or between the deck and liner and come out at an area that is not at all where the water went in.

I had a boat seven weeks ago that had a leak over the nav station. Owner re-bedded everything within a 5' radius of the nav desk. Still had a leak. I happened to notice a slight dampness behind a hanging locker around a screw and the leak was traced to the forward port light. Rebedded that port and the problem went away... Water was tracking all the way from the forward port light to the nav desk before it found a means of egress into the boat. Chainplates are a great area where tracking leaks occur if the deck has not been potted.

If the deck has been potted care must be taken to make sure there is minimal to no movement in the chain plate and that the butyl is in compression, (really packed in) if using butyl....
05-28-2013 05:53 PM
Maine Sail
Re: LifeCaulk vs. 3M 4200

Quote:
Originally Posted by asdf38 View Post
Maine, do you allow the butyl to be exposed on the deck? I'm rebedding my chain plates which also go through the deck in a similar fashion. I'm concerned about the portion of the butyl that will be exposed to UV and dirt/grime.
It won't hurt it at all... It might collect some grime over the years but you can wipe it with a rag slightly dampened with mineral spirits and clean it up...
05-28-2013 02:31 PM
FirstCandC
Re: LifeCaulk vs. 3M 4200

By the way, that diagram is GOLD!
This thread has more than 10 replies. Click here to review the whole thread.

 
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