SailNet Community banner
1 - 13 of 13 Posts

·
Registered
Joined
·
128 Posts
Discussion Starter · #1 ·
I have read several differing opinions of bedding thru-hull fittings. Should I use 3M 4200 or a polysulfide like 3M 101?
 

·
Telstar 28
Joined
·
993 Posts
Either would work. :) What kind of thru-hull fitting are you putting in.
 

·
Registered
Joined
·
128 Posts
Discussion Starter · #3 ·
Either would work. :) What kind of thru-hull fitting are you putting in.
It is a bronze thru-hull which is the outlet for the sink drain. There is a backing plate that is glassed to the inside of the hull at the penetration.
 

·
Telstar 28
Joined
·
993 Posts
For what? The depth or speed transducers??? Either should work as the through-hull is Marelon...

Dog...How about for tacktick?
 

·
Registered
Joined
·
1,274 Posts
If you have a solid mechanical connection, consider using 101. 101 is a sealant, 4200 is an adhesive. If you need to get it apart in the future it will be easier to do if you use 101. If you want a little extra security, the 4200 will add an adhesive component that might help prevent it from coming loose.
 

·
Super Moderator
Joined
·
6,819 Posts
I have read several differing opinions of bedding thru-hull fittings. Should I use 3M 4200 or a polysulfide like 3M 101?
This is entirely dependent upon your choice of seacock installation. Are you using a true & proper flanged seacock with through bolts that hold the flange to the hull or are you using a ball valve simply threaded onto a thru-hull fitting directly?

If you are threading a ball valve directly to a thru-hull you really have NO mechanical seal strength and might even opt for 5200. I hate 5200 but I dislike ball valves threaded directly to a thru-hull even more..;)

So it all depends on whet your definition of "seacock" is. With proper flanged seacocks that are bolted to the hull 101 is great stuff as is Sikaflex 291. Sika 291 is a lower adhesion polyurethane 220 PSI vs. 300 PSI for 4200 vs. 700 PSI for 5200. 3M 101 is about 140 PSI..
 

·
Telstar 28
Joined
·
993 Posts
One reason to use 4200 is cure time. 4200 cures in a 24-48 hours... 101 takes two to three weeks to cure.
 

·
Super Moderator
Joined
·
6,819 Posts
as long as we're into it...where does 4000 fit in to the product line?
It's neither a polyurethane nor a polysulfide but rather a polyether. It's supposedly more UV resistant but in my own experience it does yellow.

It has a similar general rated bond strength to 4200 at 300 PSI.. However it bonds to gelcoat at about 424 PSI. At 500 hours it has an elongation before break of 804% but at 1000 hours it drops back to 723 which tends to mirror polyurethane products losing flexibility over time..

It would not be my first choice for below water use..
 

·
Telstar 28
Joined
·
993 Posts
Probably, but if you go with 4200, you can wait until it is mostly or fully cured.. :)
Can the boat be splashed before the 2-3 week cure time?
 

·
Registered
Joined
·
1,274 Posts
It's neither a polyurethane nor a polysulfide but rather a polyether. It's supposedly more UV resistant but in my own experience it does yellow.
It says on the packing that it is safe for "most plastics." I suppose the only way to know for a particular plastic is to try it?

Also, when it bonds to gel coat at 500 psi, does this mean its stronger than the gel and should be considered permanent?
 
1 - 13 of 13 Posts
Top