Best bonding sealant

[Byrnerc]

Are there any strong opinions, based on experience, on what is the best bonding sealant to use for attaching a teak toe-rail and teak bumper rail to a fiberglass hull (assume gel coated)? I’ve researched the most common ones available: 3M 5200, 4200, 4000UV, and BoatLIFE caulk and sealant but still not sure. I want strength to hold the foresail rigging and a good seal to keep water from the screw holes. I think it needs a little flexibility for hull movement and I want it to last 20 years. I can’t seem to get all in one package; polyurethanes are strong but less flexible and supposedly only last 10 years, polysulfides are flexible and last 20 years but not as strong. Any solid opinions based on experience would be appreciated.

[billknny]

First, any toe rail that will be subjected to "foresail rigging loads"must be mechanical fastened, and not rely an adhesive bond.

Second, your information is suspect. 5200 does not have a "10 year life."

It also has a specified elongation under load on the order of 700 or 800 percent. Do you really think that is not flexible enough for you???

All of the products you describe are good sealants and if you know how to use them will keep water out. None of them are designed as structural adhesive that is the means to take significant long term load without mechanical fasteners.

[miamizx]

IMO 5200 will be about the strongest both with some flexibility and it lasts forever.

[steve77]

This is the first I have heard that 5200 is only good for ten years. I believe an awful lot of it has been used over the years in boat construction.

I assume these components are also to be through-bolted since you mention screw holes. I also assume you never plan on removing these so would use 5200.

Cheers!


Steve

[Byrnerc]

Thank you, all solid advise. Yes it is fastened with wood screws, no space for nuts and washers, so I feel the importance of bonding. The 10 year life of 5200 came from a good article in Good Old Boat and I couldn't find contradiction on 3M site. I work with polyurethane connectors and they are hard, inflexible so 5200 must be different. Thanks again.

[rbk]

I believe 5200 only has a lifespan when exposed to UV.

[Terra Nova]

Originally Posted by Byrnerc

...I want strength to hold the foresail rigging...

You need mechanical fastening, not adhesive, for these loads.
3M 5200 makes an excellent adhesive for wood-to-fiberglass interface.

[randomrun]

I used quarter twenties drilled and taped every 6” and 5200 to fasten my teak rub rail which had a triple twist some 30 years ago. No problems to this day. Made the scarfs in the shop for a rail 35’ long. This is a big job so take your time. Covered teak with a 3/4” stainless rub strake.

[Simi 60]

Originally Posted by miamizx

IMO 5200 will be about the strongest both with some flexibility and it lasts forever.

How long is forever these days?

[Byrnerc]

So 5200 it is and I'll switch from wood screws to bolts where ever possible. You can't beat the wisdom from experience.

[a64pilot]

Originally Posted by rbk

I believe 5200 only has a lifespan when exposed to UV.

I believe that is likely true.
My boat is thirty years old and the hull to deck joint is put together with 5200 and thru bolted, the 5200 doesn’t seem to have suffered any degradation from what I can tell, it’s still as tough and flexible as new.

[Delfin]

Originally Posted by Byrnerc

Thank you, all solid advise. Yes it is fastened with wood screws, no space for nuts and washers, so I feel the importance of bonding. The 10 year life of 5200 came from a good article in Good Old Boat and I couldn't find contradiction on 3M site. I work with polyurethane connectors and they are hard, inflexible so 5200 must be different. Thanks again.

The 10 year life is baloney. I glued soap holders to tile in my showers with 5200 in 1992 and if you tried to pull them off, you would have to pull off the tile with them.

[Byrnerc]

The 30 y.o. deck to hull and shower soap holder is proof enough. I thought 10 year life was unusual. Thanks.

[Suijin]

Originally Posted by Byrnerc

Thank you, all solid advise. Yes it is fastened with wood screws, no space for nuts and washers, so I feel the importance of bonding. The 10 year life of 5200 came from a good article in Good Old Boat and I couldn't find contradiction on 3M site. I work with polyurethane connectors and they are hard, inflexible so 5200 must be different. Thanks again.

Stripping all the hardware off the deck of my boat last year was an exercise in learning the lifespan of 5200. All the hardware had been put down with 5200 32 years ago. Anywhere that it had not been exposed to UV it looked and was performing as though it had been installed the week before. No leaks anywhere. I had to use a car jack to get some of the bigger hardware off. That said it does not have stellar UV resistance.

4000uv has about 25% less tensile strength but increased flexibility/elongation vs 5200, and is much more UV resistant. It's what I put all the hardware back down with, except some stuff that went on with butyl. I honestly would have put everything back down with 5200 but decided not to to avoid scowls and remonstrations from my cruiser friends. It's amazing stuff, and anyone who goes on about how hard it is to disassemble stuff put together with it a) does not know how to work with it and b) is kinda missing the point; you want that sort of performance when it comes to bedding stuff if it pushes out the rebedding chore to every 30+ years.

My teak caprail and rub rail were both installed at the factory with 5200. Other than some slight deterioration of exposed calk on the inside underside of the caprail, it's performing fine.

If I were you I would install it with 5200. You'll be pushing up flower before it needs to be rebedded.

[Byrnerc]

Again, all this proof that 5200 lasts much longer then 10 yrs. has given me the confidence that I'll only have to do this job once. The edge may see UV but the majority should be covered. Thanks.