Silicone

[hellosailor]

Jack, that's definitely not 5200, which sets up fairly solid in short order. Six month old 5200 will sit there just like a good synthetic o-ring, no gummy quality to it at all. Sounds more like one of the Boatlife products (polysulfone? based) which is *intended* to remain pliable and soft for its life.

3m "101" might be closer to what you are thinking of, it stays gummy for a long time, much more flex than 5200 but lower adhesion. Somewhere online, if you search for it, 3M has a nice brochure showing all their marine sealants and cross-comparing features and strengths of them side by side to make selecting the most appropriate one easier.

Or call 3M Product Info 1-800-364-3577 they can connect you to the source for any 3M product from any division.

[Stevens 47]

Thanks hellosailor I will look into that. Jack

[Alan Wheeler]

Jack, that sounds like a mastic. It is good at sealing and was common to be used as such. But it has no ability at helping adhere the item to the boat. If it was 5200 or similar, you would not be able to easily remove the item. Although 5200 has some movement, it will adhere an item better than screws will.

As for the windows discussion. I peronaly don't like screws. Screws AND adhesive sealant is good, or sealant on it's own is good, but not JUST screws. If you think about it a cubic metre of water weighs in at 1tonne. Now throw that at the side of the boat. Even a small hatch gets a lot of force thrown at it. I would not want all the stress coming on screws at varying intervals of attachment around my window. I want the stress to be taken over as evenly as possible.
A large charter boat down in Fiordland (breaksea girl, and she is a seriouse boat design for southern ocean trips) had it's side Pilot house window blown in on one ruff trip. So side windows can take as much hammering as deck hatches and the like.

Originally Posted by Stevens 47

As I remove various bits from my boat. Like the toe rails and other types of hardware. I have noticed that it has been bedded in a white ply-able and very sticky compound. This stuff holds together really well. My boat was built in 1981 and the bits being removed are original. So this stuff which I assume to be 5200 is still elastic ply-able and sealing well. If I leave any of it laying around and step on it, it will stick really well to my shoes. Now it does require being careful as not to damage the parts being removed because it sticks to well. I am impressed and will use it again for bedding in hardware such as port light, hatches (new SS) and toe rails etc. All of these items will also be attached with mechanical fasteners. Does anybody have a comment on 5200 from what I have seen it does not harden or become brittle it's just really sticky or maybe this is another material?

Originally Posted by Stevens 47

Jack

Jack,

Is is not 5200. Cured 5200 is not sticky. Also, if it was 5200 it would be almost impossible, not merely difficult, to remove. 5200 does not become brittle or hard, but then neither do any of the other modern sealents.

For toerails 5200 would likely be an excellent choice. For other hardware, anything that MIGHT need to come apart in the future, DON'T DO IT. Learn the right way to install hardware, don't use 5200 except where is is the appropriate choice.

[FrankZ]

Originally Posted by GreatKetch

Jack,

Is is not 5200. Cured 5200 is not sticky. Also, if it was 5200 it would be almost impossible, not merely difficult, to remove. 5200 does not become brittle or hard, but then neither do any of the other modern sealents.

For toerails 5200 would likely be an excellent choice. For other hardware, anything that MIGHT need to come apart in the future, DON'T DO IT. Learn the right way to install hardware, don't use 5200 except where is is the appropriate choice.

And as an added bonus.. 5200 can be applied below the waterline while there is water above the water line and will still cure. I wouldn't say it would be a good choice if you get holed, but a slow leak could be rectified or at lease put at bay with it.

There is a lot of mis-information (IMHO) in this thread about the appropriate sealant to use for bedding hardware. Forget windows for the moment, they are a very specialized topic and the individual mecanical design and material really needs to be considered.

Lets talk about about bedding hardware. Things that are bolted down to the deck of a boat. Things where there are bolt holes and possible other holes as well, through the deck. This is NOT a place to use 5200 or any of the other adhesive sealents! If you have ever had to remove such hardware you will understand why I say that. With good practice is possible to use silicone or other sealant and make a permenant seal that can still be removed in the future.

When you use silicone you are making a gasket. Silicone will stick to some materials, but for most things you would be bedding adhesion is limited. You need a thick enough layer of cured silicone that you can compress it AFTER it cures.

Good practice looks like this: Clean everything. Old sealant, dust and dirt is the enemy. When it is clean, clean it again. Vacumn or use compressed air to make sure you have all lose material removed. Apply a thick layer of sealant EVENLY to the entire surface. Assemble everything without pulling it tight. You want between 1/8" and 1/4" ( 2 to 5 mm) of sealant left in the gap. Use spacers if needed. Allow the sealant to cure COMPLETELY (maybe a week!) Then and only then do you crank down on the bolts to full torque.

If you do it this way you will have a permenant seal with a non-adhesive sealant. You will also not have a FO (Future Owner) hunting you down plotting your slow and painful death! It really does work. I use silicone all the time for this kind of application. NOT because it is cheap, but because it is the right tool for the job. Bedding compounds do not need to be glue and 5200 is the best glue around.

5200 is for thru-hulls, hull-deck joints, toerails, keel joints, etc. Permenent structural joints. It is SUPER at such things.

Bill

[ssullivan]

Originally Posted by GreatKetch

With good practice is possible to use silicone or other sealant and make a permenant seal that can still be removed in the future.

When you use silicone you are making a gasket. Silicone will stick to some materials, but for most things you would be bedding adhesion is limited. You need a thick enough layer of cured silicone that you can compress it AFTER it cures.

Good practice looks like this: Clean everything. Old sealant, dust and dirt is the enemy. When it is clean, clean it again. Vacumn or use compressed air to make sure you have all lose material removed. Apply a thick layer of sealant EVENLY to the entire surface. Assemble everything without pulling it tight. You want between 1/8" and 1/4" ( 2 to 5 mm) of sealant left in the gap. Use spacers if needed. Allow the sealant to cure COMPLETELY (maybe a week!) Then and only then do you crank down on the bolts to full torque.

If you do it this way you will have a permenant seal with a non-adhesive sealant.

Bill

Bill, this is *exactly* how I was taught to do this type of work. I did this on all my ports (and one hatch) and they are all leak proof. I think that's the idea people are missing that I'm trying to explain. Silicone is simply a gasket to keep water out. It's not a adhesive, cure all sealant, etc.... The screws and bolts keep hardware in place. The "goop" is just to fill gaps. This is, to my understanding, the proper way to use it.

Especially important is leaving the gap, letting it dry and then re-torquing down the hardware. This is what I did on all my ports and I have no water leakage at all. Also consider that my boat has freezing water and snow on it in the winter. Even that didn't pry open any leaks. It's all working perfectly.

[GordMay]

What Bill & Sean said about Silicone as a gasket, and what Alan said about not using Acetoxy Silicones on Al., Galv. or SS

[irwinsailor]

I bought a Fein multimaster tool for removing my hatches that were installed with 5200. It worked quiet well but took time. 5200 is tough stuff to get loose.

[cat man do]

Originally Posted by GordMay

GLAZING:
C&C Yachts featured very elegant, flush mounted, frameless, sidelights with no mechanical fastenings.
I believe the structural adhesive was a methacrylate.
Over the 17 years we knew her, “Southbound” (1984 C&C29) never leaked a drop through the glazing.

Just of to one side, and not intended as thread drift, but this is how a lot of windows are done these day's, and how i've done the last few .

No srew's , no leak's

From Bob Norson at the Coastal Passage

install windows

Dave

[irwinsailor]

I did not use screws when we replaced our windows. I called sikaflex and they convinced me that their products would do the job. It made for a nice clean look and all the leaks are gone.

[ssullivan]

My boat has these long ports that need to be re-bedded soon. The PO did a horrible job and now one is starting to leak (see photo of ports running fore and aft). I would like to use the new screwless technique as well, purely for asthetic reasons. Is everyone happy with the results? Still pretty seaworthy?

[cat man do]

Originally Posted by irwinsailor

I did not use screws when we replaced our windows. I called sikaflex and they convinced me that their products would do the job. It made for a nice clean look and all the leaks are gone.

How did you stop the windows moving while the sika set??

Sean , the double sided tape option is the way to go IMHO, as long as you use the stuff meant for the job.

The windows in my last cat were around 1 metre x 600 mm and had some big waves into them with no prob's. We did use 10mm shinkolite though. Don't use cheap acrylic, wasting your time and money

Dave

[s/v 'Faith']

Sean, it was my rant on silicone on the other thread... I am teased about being a bit over expressive on the subject. It is the result of some presonal suffering based on silicone and DPO's...

Silicone is an inexpensive sealant that works well as a compression gasket (as has been mentioned in this thread already). I Like silicone for mechanical gaskets, where metal on metal (or metal on plastic) sealing where slightly (very slight) imperfections in surfaces may cause leaks. Something like waterpump (with care not to allow any globs to fall into the cooling stream for fear of causing clogs).

I am sure that the port mfg cited likes silicone, as it does not harm the ports, and allows some flex between the metal port frame, and plastic (plexi) or glass ports.


Having said that, I believe that there ought to be a law banning silicone on docks, in marina's or anywhere within 10 miles of any boat that is not designed to be scrapped before it is 10 years old....

.... Ok, maybe a LITTLE bit harsh... but just a little.

Why>?

Silicone oil (present in silicone caulk) is made up of VERY small molecules. It bleeds from the caulk into any porous or semiprous medium. While the silicone comes off easily, the oil remains.

Silicone is impervious to water, alcohol, acetone, or any petroleum-based solvent. There are some 'release agents' marketed for silicone, they are expensive and only work to remove the silicone caulk, not the oil. There are 'silicone solvents' marketed, they can wash silicone off the surface but not out of the underlying material (in my experience). They are also pricey, so you are not going to want to use any real quantity of them.

Surfaces that have had contact with silicone not only will not hold paint, they do not prime well (primer does not bond) nor will epoxy bond to these surfaces.

Auto painters will tell you that silicone wax makes their job difficult. The silicone causes 'fish eye' which they can add an additive that increases the surface tension of the paint, but can promote chipping. THe problems with auto paint are not as serious since sanding can remove the paint which is where the silicone is carried.

Fiberglass, and wood 'wick' silicone oil deep below the surface. Sanding does not remove the oil, and can actually make the problem worse by spreading it around.

In my experience, I have painted, and had the paint lift. I then sanded and washed repeatedly with different products... to no avail.

I even went so far as to conduct 'pull tests' where I epoxied a block of scrap wood to the fiberglass I had tried to clean and prepare..... I was able to knock the block of wood off the epoxied (west, unthickened) surface with a tap from a screw driver handle.....

After several attempts to address these problems I took to using a sharp chisel to carve out the top 3/16 or so of the contaminated glass, and built up new glass to cover it...... much more work then it should have been.
Admittedly I am a bit anal about some things, but watching paint chip off of a newly painted surface can really ruin your day. Even taking such extreme steps, I found an area the other day where I did not get it all.. and there is a small crack in the apint where it failed to bond (like you get if you paint over the waxy blush west leaves.)

Everyone does what they think is best for their own boat. I won't even use silicone on the window frames, as I might want to repaint the fiberglass that surrounds it. My hull was laid in 1964, and she is a 'good old boat', maybe that is why I think about the maintenance I do with a longer range view. I plan to keep her for some time, and want whatever I do to her to be good work, or at least something that leaves the boat better then I found it.

OBTW, I think it was last year Good Old Boat did an article on caulks and sealants and they only recommended silicone for windows, and cautioned against getting it on fiberglass and wood…. so it is not just me.

[s/v 'Faith']

Here is a link to a discussion of silicone on the Ariel owners association.

It has some comments from others with similar experiences.

also,

This comment was from research I did on the suject, I can't attest to the basis for the problem in the molecular chemistry, but posted it since it made sense to me in explaining what I observed.

Silicone oil (present in silicone caulk) is made up of VERY small molecules. It bleeds from the caulk into any porous or semiprous medium. While the silicone comes off easily, the oil remains.

Silicone is impervious to water, alcohol, acetone, or any petroleum-based solvent.