Association Forum - Butyl vs polysulfides vs Sika/3M

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Butyl vs polysulfides vs Sika/3M

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blanik
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Canada
210 Posts

Initially Posted - 12/14/2011 : 14:10:37

Hi, in the process of my mast overhaul, i plan to put the mast step halyard plate while the mast is down although i don't plan to bring the lines to the cockpit this year, it'll be a breeze to do when i want to if the plate is already there... sooo here's what i'm not sure about:

CD has two halyard mast plates, one advertised for Standard Rig (with no pictures) ans one advertised for Tall/Std Rig... what are the differences between both?

and second: how to properly seal the plate? (since the mast step is a place i don't want water to go in...), i used Sika for my companionway woodwork but as i was told here that polysulfide is better since it will allow removal down the line, (searching online turns out debates about butyl vs polysulfide, i thought they where the same) if i go the butyl or polysulfide way, should i cover the whole plate? will the weight of the mast squirt it all out?

1984 C25 FK/SR #4593
Lake Champlain

Edited by - blanik on 12/14/2011 15:58:26

dmpilc
Master Marine Consultant

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USA
4593 Posts

Response Posted - 12/14/2011 : 14:58:41

First, which rig do you have, std or tall? Also, what year is your boat? Many of us have that info in our signature as you will see below. sometimes that info affects how we answer a question. It would help to see a picture of your current mast step set-up, too.
The std/tall plate probably will have more holes drilled in it to minimize drilling a hole(s) to match your configuration. You could take your present mast step and mark the holes on a piece of paper, blacken them in, and fax it to CD and see which plate they recommend.

Edited by - dmpilc on 12/14/2011 15:07:54

blanik
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Canada
210 Posts

Response Posted - 12/14/2011 : 16:12:22

thanks, i updated my signature, the holes is probably the reason why they make two different plates but why not just make one that will fit both?
my main concern is how to seal such a large surface, do i put the mastic all the way or i just go around the bolts and the edge of the plate? would a more permanent seal like Sika be good for that plate?

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 12/14/2011 : 16:17:43

As for bedding, I might be becoming the polysulfide nazi. Butyl's advantage is easy replacement; its disadvantage is that is fluid and will eventually squeeze out. Polysulfide is stable when cured (3-5 days) and will seal and remain elastic for a very long time, easily a decade. It is the bedding compound of choice unless there is a specific reason not to use it, as in it will eat some plastics. Countersink and seal the holes in the deck, put the machine screws through the plate, put masking tape over the screw heads so you can turn it upside down, put a generous enough bead around each screw to overfill the countersink, position the plate and tabernacle assembly with the screws through the deck, and finally, put nuts on the screw just tight enough to keep everything in place while it cures. Later, when you tighten the nuts fully, the cured polysulfide will be compressed in the conical countersink and you can forget about a potential leak. I did mine about 6 years ago. You can also put a bead around the perimeter of the plate to prevent collecting water that will become discolored, I did, but it doesn't affect the watertightness.

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pastmember
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2402 Posts

Response Posted - 12/14/2011 : 16:47:09

I called Garhauer and bought a plate with no holes so I could drill my own to match my mast step. I sealed the bolts, not the plate.

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Stinkpotter
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Djibouti
9080 Posts

Response Posted - 12/14/2011 : 23:10:44

I pretty much agree with Dave's approach. The "countersink" can be tricky, because fiberglass can grab a drill bit and you can end up with a big hole instead of a countersink. A solution I learned was to use an oversized bit and put the drill in reverse--it will allow you to carve a nice conical groove around the hole.

I'm also a polysulfide (Life Caulk) fan... I like to bed the entire deck hardware piece so that water can't get under it (and freeze in the winter), so I apply it fairly liberally and then lightly tighten the nuts so that it barely squeezes out around the fitting. Then I let it set up for a few days. Then I crank down the nuts, holding the bolts from above so they don't turn, to put pressure on the "gasket" that has been formed. By keeping the bolts from turning, I'm maintaining the seal around them that prevents water migration down the bolts themselves. (Water is diabolical!) Afterward, any polysulfide that's leaked out around the edges can be easily trimmed away.

Regarding the choice of mast steps, my recollection is the standard and tall rigs have different mast extrusions--I think the TR might be common with the C-27. So different fixtures might be required.

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blanik
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Canada
210 Posts

Response Posted - 12/15/2011 : 13:11:32

i didn't know polysulfide was "life caulk" (spelled "Life-Calk" on their web site), it's a gun type product?! i expected a paste like butyl, if i'm going to go for a gun type i already have plenty of 5200 ans Sikaflex, and since a mast step plate is something i'm not supposed to take off sometime down the line, i don't mind the adhesive proprieties... i thought a pasty product like butyl would be easier to use since it wouldn't smear everywhere and get on the bolt treads :-/

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Dave5041
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USA
3758 Posts

Response Posted - 12/15/2011 : 13:44:37

Use what you want, but polyrethanes are adhesives, not bedding compounds. Nothing else will stay as flexible, which is what you want in bedding, as polysufide. Polysulfide is not really adhesive, so it cleans up really easily after it cures, unlike silicone, and it is available in smaller squeeze tubes.

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 12/21/2011 : 17:39:50

http://www.sailnet.com/forums/gear-maintenance/63554-bedding-deck-hardware-butyl-tape.html

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Stinkpotter
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Djibouti
9080 Posts

Response Posted - 12/21/2011 : 20:20:46

Getting back to your question about the weight of the mast (and the pressure induced by the stays pulling it downward), my concern about butyl caulk and tape would be that the considerable pressure of the rig might eventually squeeze too much of it out. Polysulfide sets up as a stable, non-flowing gasket, and should be allowed to do so before finally tightening the hardware and stepping the mast. As mentioned, it's a breeze to trim and clean up where it has squeezed out--just wait till it sets up.

5200, in my experience, is adequately resilient, but very adhesive. You say you will never remove the mast step... Well, maybe not--unless for some unexpected reason it leaks around a bolt that has been turned. If you ever have to remove the plate after bedding with 5200, expect to pull gelcoat off the fiberglass, which in turn might even pull up the top lamination of the fiberglass. It can get ugly. Don't ask how I know. (It was a builder's fault!)

IMHO, unless you're in construction, dispose of your 5200. It's for boat builders--not for boat owners, and some boat builders misuse it. West Marine, the Walmart of boating, shouldn't even offer it to unsuspecting owners. Proper mounting and bedding of deck hardware does not rely on adhesion.

Edited by - Stinkpotter on 12/21/2011 20:29:54

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 12/22/2011 : 15:45:39

I am pretty sure that my aluminum trimmed portlights were originally bedded with butyl, and the fact that it never hardens explains them leaking like a sieve over time. It will happen much sooner in a continuously, highly loaded application like under a mast.

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.