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I'm adding a stern rail to my little boat this weekend, and the install kit from Catalina Direct came with a tube of 3M 4000.
I'm probably not going to use it. I have some of Maine Sail's butyl tape that I've used before and had good luck with, so I'm thinking I'll go with that.
I'm just curious what's the difference between 3M 4000 and 4200?
What would you use for bedding a stanchion / rail?
Sounds like 4000 would work great for bedding, probably better than 4200.
I still haven't decided butyl vs. 3M product.
I will countersink the holes I drill, so I'm not really worried about all the sealant oozing out. My primary purpose for the stern rail is as an additional handhold for boarding from the swim ladder or for mobility impaired people getting on and off the boat, so I expect it to be frequently flexed. It seems like butyl would be better for that.
I've converted to bedding everything on deck with Butyl tape. So far it is mostly working. Where I still have a leak, I think when the stanchion is jarred it deforms the deck just a little and lifts up breaking the seal with the tape.
I've never had good luck with bedding with butyl for stanchions or deck hardware. The fact that it stays flexible means it oozed out over time, and starts to leak.
I spent a month this last winter rebedding everything on deck of my boat, and redoing the headliner, due to leaks. The ones that had been bedded with butyl leaked.
None of the ones bedded with 4200 leaked. I redid all of them, leaking or not, with 4200. I also find 4200 easier to remove than old butyl.
I'm with lazer brain. I've used both, and I really like butyl for many things, but not stanchions.
However, 3M products are not my first choice, since they do not bond as well to metals. Locktite PL Marine is better with stainless and aluminum. However, of the 3M products, 4000 UV is the best for metals. They sent the right stuff. Use it. Smart folks.
FWIW - I countersink whether I'm applying butyl or 4200. It still eventually leaks. 4200 and similar actually bond to the screws when bedding, and flex with them. Butyl doesn't bond, so it eventually wallows the seal around each screw when the fitting flexes.
Try this experiment - drill two holes in a piece of 2x4 and set a screw in each one (make the holes slightly larger than the screws). Set one screw in 4200 and one in butyl. When the 4200 is cured, slightly move the screws back and forth. What you will see is that the 4200 flexes with the screw, and stays bonded in a seal. The Butyl will wallow out a larger and larger hole.
Did I mention that old 4200 is also easier to remove than old butyl?
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