3M 5200 (IMHO)

[stevensc]

I once read that 5200 is so messy that if you order a tube of it by telephone it will get all over your ear!

Works for me though
Steve

[DeepFrz]

I once read that 5200 is so messy that if you order a tube of it by telephone it will get all over your ear!

That is funny.

It must be reasonably flexible if Dee Caffari is using it for sail repair. I believe her main is delaminating. And she did have it all over her hands in her video yesterday...LOL.

[Christian Van H]

Originally Posted by DeepFrz

That is funny.

It must be reasonably flexible if Dee Caffari is using it for sail repair. I believe her main is delaminating. And she did have it all over her hands in her video yesterday...LOL.

Dee used Sika-Flex and epoxy. No 5200 there either...

[DeepFrz]

Ooops, my bad.

[Christian Van H]

No problem, Frz! If it was 5200, she might wake up permanently stuck to her bunk!

[Maine Sail]

Why anyone would use a product who's bond to gelcoat is actually stronger than the gelcoats bond to the substrate is beyond me. While 5200 is flexible compared to some other polyurethanes, 700-800% elongation before break, it is the tenacious adhesion that is generally the problem.

One thing I never hear mentioned is that Polyurethanes do not like UV yet I see folks use it constantly in UV exposed settings. If your polyurethane bead is exposed it will and can eventually crack & fail.

Polyurethanes, according to a friend who is a chemist, generally continue to harden, though at a very, very slow rate, throughout it's life span. This curing or hardening of the product can reduce the elongation before break numbers over time and is a possible hypothesis as to why we see so many failures and leaks.

Polysulfides on the other hand are not as affected by UV as polyurethanes and while their initial rated elongation before break numbers are lower than that of 5200 or even 4200 they should not diminish over time as polyurethanes tend to. Polysulfides, even years later, are generally as flexible as the day they finished curing where polyurethanes are not.

Let's take a seacock for a example. Using 5200 for them is kind of like welding on your lug nuts. Think about it. Lug nuts go down the road at 70-80 mph for thousands of miles on end, take massive pot hole hits, deal with poor alignments, bent rims & tires out of balance. Between rim removals they rarely if ever get tightened, torqued or looked at and still nobody glues them to the studs or puts a glue between rim and hub? They don't even use blue Loctite!

A proper seacock is fastened with large main threads and proper torque, and then through bolted to the hull with multiple smaller bolts. A seacock does not spin, move or hit massive pot holes. Despite the shear lack of abuse they see, when compared to lug nuts & wheels, people still insist on "welding" them to the hull with 5200! All you really need is an underwater rated & capable sealant. Even 4200 is slightly over kill. Mechanically fastened hardware is MECHANICALLY FASTENED!! All the sealant has to do is be flexible and adhere to each surface enough to not part during any flexing.

My 30 year old boat is bedded, and was bedded from the factory, entirely with butyl tape. Buytl tape has about a 10 PSI adhesion but is MUCH, MUCH, MUCH more flexible than any polysulfide or polyurethane. Over 80% of the fittings on my deck, including the deck to hull joint, are still bedded with the original butyl from 30 years ago!! It's still flexible and still NOT leaking.

You do not need to glue mechanically fastened hardware to the deck but it does need to be flexible and seal out moisture butyl tape does this as do the lower adhesion polysulfides LifeCaulk & 3M 101.

You're looking at an elongation of well over 3000%. This butyl bedded cleat was removed at the 29 year mark, still BONE DRY and very, very flexible!

The Core Was Still Bone Dry:



Popular Marine Sealants

Polyurethanes =
3M 5200
3M 5200 Fast Cure
3M 4200

Boatlife Life-Seal (A Polyurethane / Silicone hybrid)

Sikaflex 295UV
Sikaflex 291
Sikaflex 291 LOT
Sikaflex 292
Sikaflex 252
Sikaflex 227 Fast Cure
Sikaflex 201US

Polysulfides =

3M 101
Boatlife Life-Calk

Polyether =
3M 4000UV

Here's a quick run down with specs:

3M UV 4000 is a one part polyether with UV inhibitors added. It has a elongation before break of 800% and a tensile strength of 300 PSI. Spec wise UV 4000 is very similar to 4200 but because it is a polyether, and not a polyurethane, it reduces ti's elongation before break slightly. This should not be a concern if you use proper bedding techniques.

3M 4200 is a one part polyurethane with NO UV inhibitors added. It has a elongation before break of 900% and a tensile strength of 300 PSI.

3M 101 is a one part polysulfide. Polysulfides have a natural UV resistance and are the premier product for use in teak decks. Polyurethanes do not do well with UV so UV inhibitors are added. 3M 101 has a tensile strength of 139 PSI and an elongation before break of 416%. Life-Calk is a polysulfide rated at about 80 PSI adhesion.

Sikaflex 291 is also a one part polyurethane (my personal favorite polyurethane) with lower adhesion than UV 4000 or 4200.. It offers an elongation at break of roughly 600% and is the easiest one part polyurethane sealant to get off in the future!

Here's one last photo. It shows a cutaway view of a section of deck core that has been potted with epoxy and then countersunk to create an o-ring effect.

In a mechanically fastened joint, genny track, stanchion, traveler, deck cleat etc. you will NEVER, EVER see movement like this and if you do you have way more trouble than a failed sealant!! Remember this is a Butyl tape bond strength of about 10 PSI, not 1000 PSI, not even 100 PSI, just 10, which is nowhere near the 502 PSI of 5200 bonding to gelcoat, or 362 PSI of 5200 bonding to stainless steel.


Please don't get me going on silicone as I hate to even use it for the very few things that it is actually a proper choice for..

[Christian Van H]

Wow! Maine Sail, I agree with absolutely everything you posted, with the possible exception of 5200's 700-800% elongation. Where did you get that figure? I'm havin' a hard time believing it... Thanks, Chris

[FrankZ]

You can find the technical specifications for 5200 at:


http://multimedia.3m.com/mws/mediawe...6EVs6E666666--

[s/v 'Faith']

Originally Posted by CSY Man

I have used silicone quite succesfully all over the boat, not for critical stuff, but window applications and such.

You must be talking about the Home Depot kind of silicone, not the 3M Marine Silicone, the difference is acid content or some such thing......

Nope. The 'good' stuff is just as bad as the cheap stuff. The problem with acidity has to do with metallic corrosion (in applications like bedding electronic components) you don't want to use RTV that smells like vinegar because it causes corrosion.

Silicone should never be used as a general purpose sealant on a boat. While it may work in strictly compressive applications (where no adhesive is required) it will still be slowly leaching oil into anything it is in contact with (wood, fiberglass, gellcoat, etc...).

You will eventually loose the ability to paint the adjoining surfaces. There is no known solvent (there are expensive de-bonding agents, but no solvents that work). The only 'cure' is to chisel out the contaminated surface... and some times you have to go very deep to get rid of it.

Christian, from your post, it appears you applied it along side a joint with two dissimalar materials. It is likely that the prep in this area was less than ideal. If used to bed two surfaces, it works great. If used the way you described, there are better options. I have had very good success ith 5200. I have also had failures, but they are usually when I have tried to use it to stop a leak by caulking along the outside of a joint.

[Therapy]

Originally Posted by Kai Nui

I have also had failures, but they are usually when I have tried to use it to stop a leak by caulking along the outside of a joint.

Can't blame the 5200 for that.

[RBEmerson]

Take a look at the number of boats built with 5200 used to caulk the hull/deck seam, for starters.

Also, how much flexibility are you looking for?

[GordMay]

From the 3M “5200" one-part Polyurethane Adhesive Sealant Application Information, at the previously-linked Technical Data Sheet:

Surface Preparation:

There are waxes, coatings, sealants, grease, oil and other contaminants used in the marine industry, making it very important to clean all surfaces to be bonded before applying 3M Marine Adhesive Sealant 5200.

Recommended procedures include cleaning with 3M General Purpose Adhesive Cleaner*, P. N. 08984.

Application of Adhesive Sealant:

Abrading the surfaces with a 180 grit to 220 grit abrasive, and subsequently wiping off residue, will enhance the bond strength.
Cut tip of the nozzle to desired bead size.
Puncture seal inside the threaded nozzle end and screw on nozzle.
If using a 10 fl. oz. cartridge, knock out the bottom seal with a hammer and place the cartridge in a caulk gun.
Apply 3M Marine Adhesive Sealant 5200 to the seam or part to be bonded. Position parts. Tool material to desired appearance.
Remove excess material with 3M General Purpose Adhesive Cleaner*, P. N. 08984.

Cleanup:

For cleaning 3M Marine Adhesive Sealant 5200 before it is cured, use a dry cloth to remove the majority of sealant, followed by a cloth damp with General Purpose Adhesive Cleaner*, P. N. 08984, toluene or acetone.
Cured 5200 can be removed mechanically with a knife, razor blade, or sanding.

Limitations:

- Alcohol should not be used in preparation for bonding as it will stop the curing process, causing the adhesive to fail..

- Heat resistance, due to the decreased value in bond strength at elevated temperatures, we do not recommend use of this product above 190̊F (88̊C).

- Do not apply at temperatures below 40̊F (4̊C) or on frost covered surfaces.
Do not apply at surface temperatures above 100̊F (38̊C).



- 3M Marine Adhesive Sealant 5200 is not recommended for use as a teak deck seam sealer.
Extended exposure to chemicals (teak cleaners, oxalic acid, gasoline, strong solvents and other harsh chemicals) may cause permanent softening of the sealant.

- 3M Marine Adhesive Sealant 5200 is not recommended for the installation of glass, polycarbonate or acrylic windows that are not also mechanically fastened with a system designed by the manufacturer.
Inconsistent adhesion of these unprimed substrates, specific design of the window, and movement due to thermal expansion and flexing, may cause application failure. It is strongly recommended that the customer contact the window/port light/hatch manufacturer for recommendations on proper sealing procedures.

- When using 3M Marine Adhesive Sealant 5200 with metals, it may be necessary to prime the surface to achieve adequate adhesion and durability of the bond. Scotch-Weld Structural Adhesive Primer EC-1945 B/A may be used for priming of most metals.

[42AFJ]

Generally I do not use 5200 on the boat. That being said it has done a wonderful job of repairing my Zodiac Transom. It has been holding and staying bone dry.

[sandy daugherty]

Here is an apocryphal story, attributed to a Marine Surveyor in Florida. He saw three boat yard workers laughing themselves silly, and asked to hear their story. Their job was to remove an aluminum dual outboard engine mount from the back of a sport fishing boat, and discovered it had been in use for two years hanging on the boat with three bolts and some 5200. Provide your own punch line.