Sealant from deck to teak railing ?

[TJM]

Last year I re-caulked the corner joint from my fiberglass painted deck to the teak toe railing. I just noticed that the joint has opened up between the caulk fillet and the toe railing ? Ugh, I think I used a white / purple tube from 3M that says "deck hardware" but I am not 100% positive.

What should I use ?

 

[Lepke]

You need a marine caulk that remains flexible so it will stretch. The wood and fiberglass contract and expand at different rates as the sun hits or the temperature changes. Rarely do house products work on boats. Most don't work well on houses either.

 

[Comodave]

We also have a teak toe rail on our President. Last year I was refinishing the toe rail and painting the deck. When we had the teak down to bare wood and before we painted the deck with Kiwigrip, I caulked the toe rail to deck joint with Sika 291. I primed the teak with their primer ($80.00 per can) and so far it has held up very well for the last 2 seasons. I did paint over the Sika with the Kiwigrip and that may help protect the caulk.

 

[Irish Rambler]

As Lepke says the household stuff is mostly unfit for purpose.
Personally I use Sikaflex adhesive/sealant which has worked well for me both in salt/fresh water cruising. Clean the joint well and use a drop of acetone to dispel any oil/moisture, once you apply the sealant let it dry for 20 minutes to form a slightly rubbery texture before fitting for a good joint.
Forget saving a few cents and concentrate on having a perfect job done, it saves you a lot of hassle in the long run.

 

[Larry M]

We use TDS SIS-440. I’ve tried all the 3M products except 5200 with poor results. TDS comes on white, grey or black. My only complaint is the white does get dirty over time.

 

[Westiculo]

SIS-440 is good, but it's not as tenacious as some of the 3M products.
I use 3m 4000, it has good UV resistance and is much stronger than SIS-440, it comes in black and white.

 

[DDW]

The 3M product in the white and purple tube that says "deck hardware" isn't a household product. There are 3 products from 3M that you might use:

5200 - as much an adhesive as a sealant, and quite a strong adhesive
4200 - a weaker version of 5200, used when the adhesive properties are less important and you may want to remove the fitting later
4000UV - weaker still than the 4200, but will not yellow and will crack less in the sun

The 5200 and 4200 are polyurethanes, very similar to equivalent products from Sika. The 4000 is a polyether. For anything topside, I use 4000UV. Under the waterline, I use 4200 for things I may someday want to remove, 5200 for anything permanently mounted.

 

[Westiculo]

5200 - as much an adhesive as a sealant, and quite a strong adhesive
4200 - a weaker version of 5200, used when the adhesive properties are less important and you may want to remove the fitting later
4000UV - weaker still than the 4200, but will not yellow and will crack less in the sun
\

Quick correction here:

4000 happens to be a bit stronger than 4200. It's shear strength is comparable across most substrate materials if not a bit higher, and it's tensile strength is double that of 4200.

 

[DDW]

From the 3M data sheets:

4200 tensile strength 300 PSI, 700% elongation
4000UV tensile strength 253 PSI, 790% elongation
5200 tensile strength 705 PSI, 762% elongation

All fast cure versions.

That is the material itself. The overlap shear strength of 4000 tends to be a little higher than 4200, but they are comparable in the real world. 5200 is considerably higher.

 

[Westiculo]

From the 3M data sheets:

4200 tensile strength 300 PSI, 700% elongation
4000UV tensile strength 253 PSI, 790% elongation
5200 tensile strength 705 PSI, 762% elongation

That's so weird - I feel like this is why there's always discrepancy when people are talking about 3m products. This data sheet says that 4000 is >400psi. https://3m.citrination.com/pif/000887?locale=en-US

 

[Westiculo]

Sorry to hijack your thread, by the way.
I just love 3m 4000.

 

[DDW]

Yeah that's funny. The sheet I have quotes the same test methodology too, though yours is dated more recent.

Anyway, I'd use the 400UV for this job