Butyl for marelon/plastics

[Roc]

Hi All,
I know Butyl is the best way to seal stainless fittings, but is it also good for marelon or plastics (I'm not talking about below the waterline thru hull).  What I mean is a scupper thru hull that is above the waterline.

[KWKloeber]

Hi All,
I know Butyl is the best way to seal stainless fittings, but is it also good for marelon or plastics (I'm not talking about below the waterline thru hull).  What I mean is a scupper thru hull that is above the waterline.

Absolutely, with one caveat.

Depending on temp and amt used, you sometimes need to tighten down in stages over successive days so you don't deform something (e.g., C30 aluminum window frames.)

Personally I would have no issue using BWL were you aren't depending on the seal for adhesion.  We protect ourselves against the ocean on the other side with a rubber o-ring and/or teflon tape on thru hulls, etc.  Why not butyl rubber? (again, where providing an adhesive isn't the purpose.) Your mileage may vary.

KK

[Ron Hill]

Roc : On a scupper replacement -- I'd use plumber's putty as a scupper is just like a sink drain! 
There is no strain and the nut from the bottom keeps it compressed!
 
All you're looking for is a seal - silicone caulk or polysulfide will also work.

A thought

[Mike and Joanne Stimmler]

Be careful with the plumbers putty as some are not compatible with plastic.

Mike

[Phil Spicer]

     Check out the Forespar web site. They have the answers you are looking for and they are happy to talk with you.

[Stu Jackson]

Plumbers Putty would be last thing I would consider.  If you have Maine Sail's butyl tape, just use it.

[KWKloeber]

Be careful with the plumbers putty as some are not compatible with plastic.

Mike

The cockpit drains (at least on my C30) were not Marelon, but plain old PVC (Catalina's propensity for typically using Home Depot rather than marine products whenever practical.) 

Marleon is pretty stout and resistant to most everything, and PVC shouldn't be an issue with putty, but why consider it when you have butyl.  I would also consider butyl caulk over putty.

JTSO.

Ken

[KWKloeber]

Plumbers Putty would be last thing I would consider.  If you have Maine Sail's butyl tape, just use it.

I don't know, Stu.  There;s plenty of things I could rate below that!  Sillycone, bubble gum, liquid nails, 5200, 4200, 4000....... 

KK

[Stu Jackson]

Plumbers Putty would be last thing I would consider.  If you have Maine Sail's butyl tape, just use it.

I don't know, Stu.  There;s plenty of things I could rate below that!  Sillycone, bubble gum, liquid nails, 5200, 4200, 4000....... 

KK

Yup, well put.     The bubble gum got me hooting!   

[Roc]

I do have Mainesail's butyl tape.  Bought two rolls.   I'm just thinking for marelon, maybe I should use Life caulk or Life seal sealants instead?

[KWKloeber]

I do have Mainesail's butyl tape.  Bought two rolls.   I'm just thinking for marelon, maybe I should use Life caulk or Life seal sealants instead?

Share your reasoning?

KK

[Stu Jackson]

Good question, Ken.  The choice seems to be between a "sillycone" that might last a few years compared to butyl which could last almost forever.  Some choice...

[Roc]

My only thought is this...  butyl is not an adhesive.  Since the marelon fitting is just attached with a nut on the other side, the thought is maybe I needed something of an adhesive.  Deck fittings that are thru-bolted, where butyl is used, are secure with their hardware by default.  Just thinking that the nut holding the marelon fitting needed more help from an adhesive.  I'm a fan of butyl, just not sure if this was a proper application. 

[Stu Jackson]

Roc, the nut down below should be just fine to provide enough compression to keep the butyl tight.  I used two layers when I did my saloon hatch (yes, I know it's screwed down, but that's pretty much what the nut does).  I'd use the butyl.

[KWKloeber]

My only thought is this...  butyl is not an adhesive.  Since the marelon fitting is just attached with a nut on the other side, the thought is maybe I needed something of an adhesive.  Deck fittings that are thru-bolted, where butyl is used, are secure with their hardware by default.  Just thinking that the nut holding the marelon fitting needed more help from an adhesive.  I'm a fan of butyl, just not sure if this was a proper application. 

Ok fair enough question.

But first -- you're saying that both a deck fitting and a cockpit drain are "nutted."  So they are both both mechanically affixed, therefore adhesive is unnecessary.

Consider this - your plexi windows are held in place with a pretty stout adhesive -- Dow 795 -- which probably has more adhesion than what you might need for a mechanically-held cockpit drain.  Fair enough?

Dow 795 has an adhesion of about 45 psi.
Life Seal has an adhesion of 290 psi.

Do you think that, with the mechanical bond already provided, you need a sealant that holds more than 6 times better than what holds the windows on?

Life Caulk isn't compatible with many plastics, though I doubt it would attack Marleon (glass reinforced polypropylene.

Butyl rubber isn't primarily an adhesive, but that doesn't mean it has no adhesive properties.  Most car windshields used to be held by no mechanical fasteners -- only butyl rubber tape.  (More and more are being affixed at the factory with polyurethane.)

See RC's admittedly unscientific test of butyl tape's "holding power" ie- a deck cleat lifted above the surface or his "knife test."

However, as one very astute member says "Your boat, your choice!"


Ken K