What is the correct procedure to apply caulk

[Picflight]

I have boatlife life-calk at hand to bed hardware. What is the appropriate wait time to fully tighten the screws?

I had to remove the fuel fill fitting to replace the fuel fill hose, this is one piece that I have to caulk. The other is a replacement of a deck plate, I decided to use screws instead of the original pop rivets.

 

[thinwater]

Immediately. Tightening them later will only break the bond between sealant and fastener. Some have a theory that you should wait, to place the sealant in compression, but others (me included) find the logic and proof wanting.

 

[Anonymous 121765]

Pic,

There will be several opinions on what the best approach should be.

That being said, people in the boat service industry will tell you(example: a deck fitting) to apply the caulk liberally(up to 1/4" thk.) & set the mounting base onto this. Tighten the bolts/screws until the chalk begins to squeeze out (I leave the caulk thickness at about a 1/8"). Clean the squeezed-out caulk around the fitting & wait.

Different caulks have different setup times. Follow the manufacture's instructions before tightening the fitting down. When doing this you will have alittle more caulk squeeze out & just dress this. The caulk will not be setup fully underneath the base & this is what will squeeze out. I always use a flexible caulk (Dow Corning 795)for my shrouds, stanchions & other fittings which take stress. I'm looking forward to using Butyl next based on Mainsail's advice.

Now, you have a bedding with a substantially thicker gasket. Why apply caulk & tighten down while watching most of the caulk you just applied squeeze out. What you will be left with is a very thin seal. I know I'm gonna take some heat for this, but I can tell you that what I bed, I don't have to pull it up & re-bed it again.

I also don't use 5200 above the waterline on exterior surfaces. UV will harden and your bedding will show cracks. Plus, it's not flexible as other caulks & a ***** to remove. Then there's Butyl tape that works well with no messy caulk cleanup. The choice is yours my friend.

CR

 

[Brian D]

I have only applied caulk a few times so an expert this does not me make. However, I have read and read and read and come to the conclusion that the way captnron has described seems to be the consensus. Apply, tighten until the caulk starts to come out, wait awhile, then tighten and clean up.

I am working on my port lights and the above procedures are what I will be following. I too have been advised to use 795. I also have a few rolls of Butyl tape in my tool box for special applications.

 

[Brian S]

Further to Thinwater's response, countersink the holes for bolts. This will give a greater surface area for the sealant to seal between bolt and substrate, and less chance of that seal to break. Think about how thin the sealant line is between the bottom of the fitting and the smooth deck, what, a 32nd of an inch? With a countersunk fastener, you'll get maybe 1/8 inch of sealant.

You may wish to put masking tape down on the deck, and use and Xacto knife to cut out around the fitting. This helps cleanup and reduces messiness from caulk squeeze-out.

Immediately. Tightening them later will only break the bond between sealant and fastener. Some have a theory that you should wait, to place the sealant in compression, but others (me included) find the logic and proof wanting.

 

[thinwater]

Yes, camfer the holes, always.

Yes, I would use butyl, except for small fittings attach with screws. Butly does not harden and you will thank youself when removal time comes. Really. Never had it leak.

And some folks in the boat yard business feel differently; that's where I got my advise. I've seen many fittings that were bedded with sealants leak around the bolts, after the bolts were re-tightened. Suit yourself.

 

[sdstef]

Pic,

There will be several opinions on what the best approach should be.

That being said, people in the boat service industry will tell you(example: a deck fitting) to apply the caulk liberally(up to 1/4" thk.) & set the mounting base onto this. Tighten the bolts/screws until the chalk begins to squeeze out (I leave the caulk thickness at about a 1/8"). Clean the squeezed-out caulk around the fitting & wait.

Different caulks have different setup times. Follow the manufacture's instructions before tightening the fitting down. When doing this you will have alittle more caulk squeeze out & just dress this. The caulk will not be setup fully underneath the base & this is what will squeeze out. I always use a flexible caulk (Dow Corning 795)for my shrouds, stanchions & other fittings which take stress. I'm looking forward to using Butyl next based on Mainsail's advice.

Now, you have a bedding with a substantially thicker gasket. Why apply caulk & tighten down while watching most of the caulk you just applied squeeze out. What you will be left with is a very thin seal. I know I'm gonna take some heat for this, but I can tell you that what I bed, I don't have to pull it up & re-bed it again.

I also don't use 5200 above the waterline on exterior surfaces. UV will harden and your bedding will show cracks. Plus, it's not flexible as other caulks & a ***** to remove. Then there's Butyl tape that works well with no messy caulk cleanup. The choice is yours my friend.

CR

I wish I would have read this three hours ago. I just washed the caulk off my hands, boat life, what a mess! I installed a new thru-hull to install a wash down pump, and new knot meter, chain plate cap plates, re-bedded the lower gudgeon, had to tig weld a couple of cracks, but I put the caulk on thick and tightened it all down very tight. I will know next week how the seal is on the thru hulls. Oh well… I better double check my boat insurance!