Most frustrating job over with...will they leak?

[tartan30cirrus]

I have multiple questions regarding peoples' techniques in rebedding ports. Would appreciate feedback, too.

Just finished rebedding two ports in my Tartan. These are alum. frames that sandwhich a polycarb plastic window and the fiberglass lining of the boat with barrel bolts holding it all together. This was by far the trickiest job I have done to date. There were a lot of words like *(*)^)%& and *^%) &^&*@Y& coming out from under the tarp, my wife told me. I masked the frames and dry mounted the window. I cut out around the inside of the frame and peeled off the plastic protective covering. I squeezed 3M silicone caulk into the space between the plastic window and the cabin top lining and then covered the space between the masking and smeared the caulk around. I had a hard time telling if I was using too much. I also squeezed a not too generous amount onto the frame and smeared it out. I mounted the frames, snugged up all the boltes, and waited 20-30 minutes and tightened up the bolts for good. I could not believe the mess...caulk squeezing out like crazy...some places too much other places barely any caulk squeezed out. What do others do to ensure the minimum amount of caulk but not too much? How do you keep the mess to a minimum? I can't imagine doing this with 4200 which the yard used on the previous rebedding. What else do people do to ensure a tight seal? What caulk do you use? (I liked the easy clean up of the silicone). Would like feedback to add to my own reflections so I can improve on this critical area of boat maintenance.

Cheers.

PS: Incidentally, the new polished alum frames look spectacular and the new plastic is crack free and shines. Makes the other crappy powder coated frames look aweful. Will they leak is the question. Worst case scenario is I rebed again and apply what I have learned and that will be a lot easier with silicone caulk than the iron grip 4200.

[Tim]

I had a hard time telling if I was using too much...

There's no such thing as too much sealant. Too much might be enough. Not quite enough is a guarantee of failure. Caulk must squeeze out everywhere, on anything you install; any voids signal a possible weak area that may begin to leak sooner than later. One should never try to use the minimum amount; only copious amounts of caulk in any installation will help you get a long-lasting and effective seal.

Proper bedding of any hardware is always a mess. Masking everything helps, and sometimes you can leave the bead of squeezeout to cure for a few days, after which you can more easily cut it away, minimizing cleanup. The picture below illustrates this.



All caulks are a pain to clean up, and require lots of paper towels, rags, and solvent. It's all part of the process, unfortunately; there's just no "neat" way to do it, at least not effectively.

Worst case scenario is I rebed again and apply what I have learned and that will be a lot easier with silicone caulk than the iron grip 4200.

While 4200 wasn't the right choice, don't be so sure that your silicone will be easier to replace, should you need to rebed. Silicone, if it hasn't completely failed, can be a bear to remove, and extremely tenacious and resistant to scraping, sanding, and everything else. It's weird in that silicone sticks like crazy where you don't want it to, yet often fails when you really need it. Silicone is pure evil. Plus, the residue, which is often close to impossible to remove, resists bonding with everything--new silicone, other caulks, paint, epoxy...everything.

I don't mean to be a downer! I used some silicone when I rebuilt Glissando--to secure the small ports forward, and to stupidly bed behind the coamings--and have lived to regret it. I can't think of an application on board where silicone is truly the right choice. While none of my ports have leaked, I dread the day when I need to remove them again. Removing my coamings after a year was simply ridiculous in its difficulty.

A good choice for bedding ports, particularly Lexan or plexiglass (both of which are adversely affected by polysulfide caulks which would otherwise be the best choice), is butyl caulk--either the commercial stuff available at glass shops and some auto parts stores, or the hardware store variety in a caulking tube. Butyl is good because it remains flexible and soft throughout its life; old butyl, even after 30 years, is usually still a sticky mess when removed, which is actually a good thing.

[tartan30cirrus]

I decided to go with Don Casey's recommendation of silicone in ports...I liked the concept of letting it cure and tightening down on the gasket it creates. Butyl sounds truly aweful to work with!

If I do need to rebed at some point this season -- I hope I don't; can live with repeating next year -- what DOES work for removing silicone from surfaces to be recaulked. Scraping and lots of acetone?

Cheers,
Clint

[tartan30cirrus]

Incidentally, just found this interesting info on BoatUS by Don Casey.

"For an adhesive seal of plastic components, select a silicone/polyurethane hybrid.

An adhesive sealant maintains its seal even when stresses pull or pry the bedded components apart. The sealant stretches like the bellows joining the two sides of an accordion. This accordion effect can be especially useful for plastic portlight installations where the portlights are captured between an inner and outer frame. Although silicone has amazing elasticity, its lack of adhesion means any expansion of the space between the frames is likely to cause the seal to fail.

Either polysulfide or polyurethane would provide a more dependable seal, but polysulfide is certain to attack the plastic, and polyurethane prohibits any future disassembly. The answer to this dilemma is a hybrid sealant--part silicone and part polyurethane. Marketed by BoatLife as Life Seal, this mixture promises a longer-lasting seal for portlights and other plastic fittings where compression of the sealant cannot be assured."

[dasein668]

If I do need to rebed at some point this season -- I hope I don't; can live with repeating next year -- what DOES work for removing silicone from surfaces to be recaulked. Scraping and lots of acetone?

I have yet to find anything that really works. Acetone doesn't touch the stuff. Scraping will get the bulk of it off but you will still be left with a nasty silicone film which is next to impossible to fully remove.

[tartan30cirrus]

I am REALLY dreading the next rebed now!

A Dremel will get it off. When in doubt pick "C" and Dremel.

Come on...this stuff is sounding like cryptonite...a dremel has got to do it.

Cheers.

[dasein668]

Come on...this stuff is sounding like cryptonite...a dremel has got to do it.

Maybe.

40-grit paper on the Porter-Cable couldn't get it all off my deck and hull.

[Figment]

Casey touches on an interesting aspect of the use of silicone sealants, when he mentions that their cohesive strengths far exceed their adhesive strengths (it'll pull away before it'll crack).

(I've heard the following schpiel from 3M reps, Dow-Corning reps, and GE Plastics reps. Amazingly they all agree.)

The primary advantage of a silicone product is its great elasticity. The ideal profile of a finished bead of silicone sealant (really any flexible sealant) is like that of an exaggerated concave lens: Really fat at the edges so it can get a good grip, but then really narrow at the middle so that it will stretch with movement rather than pull the edges away.
This is why we always finish a sealant application by running a fingertip along the joint to create that smooth concave face. The concave face behind is best formed by inserting a string/rope of foam (known as "backer rod" in the trades) prior to sealant application.

This runs counter to Tim's There's-No-Such-Thing-As-Too-Much approach, but since Tim also prohibits the use of silicones aboard his boat, he's unlikely to ever run afoul.

This also runs counter to Casey's practice of letting the sealant cure before putting full strength to the fasteners to create a compressed gasket. He's trying to compensate for the poor adhesive properties, but he's killing the elasticity in the process.

[Tim]

Scraping does work, but that is often impossible since it will also harm your paint or gelcoat. Getting this material off metal, assuming you can get tools in there, is less of an issue, since the metal will withstand more serious toolage without damage.

Believe me, though. We are not blowing smoke around here. Silicone, when bonded to fiberglass, is a true bear to remove completely. Sometimes the bead peels right off--but if it doesn't come right off, look forward to a long, frustrating road. Even if it peels away, beware of the potential surface contamination left behind, which you can spread over the entire boat with a sander if you're not careful.

Repeat after me, class: silicone is pure evil.

On boats, there is always a better choice. Really.

Caulking/bedding is a messy, miserable job, but is one of the necessary pains of boat maintenance.

[Tim]

(I've heard the following schpiel from 3M reps, Dow-Corning reps, and GE Plastics reps. Amazingly they all agree.)

The primary advantage of a silicone product is its great elasticity. The ideal profile of a finished bead of silicone sealant (really any flexible sealant) is like that of an exaggerated concave lens: Really fat at the edges so it can get a good grip, but then really narrow at the middle so that it will stretch with movement rather than pull the edges away.
This is why we always finish a sealant application by running a fingertip along the joint to create that smooth concave face. The concave face behind is best formed by inserting a string/rope of foam (known as "backer rod" in the trades) prior to sealant application.

This runs counter to Tim's There's-No-Such-Thing-As-Too-Much approach, but since Tim also prohibits the use of silicones aboard his boat, he's unlikely to ever run afoul.

This also runs counter to Casey's practice of letting the sealant cure before putting full strength to the fasteners to create a compressed gasket. He's trying to compensate for the poor adhesive properties, but he's killing the elasticity in the process.

There is no doubt that silicone has uses in the world...it is indeed wonderfully elastic, and good for a lot of things. But on boats I just think there are better choices. If you can install something permanently and effectively with silicone, I'm sure it's great. The main beef here is the difficulty in removing the residue when the inevitable time comes (usually sooner than later) when rebedding is required.

[Shark]

Silicone is pure evil!

I made the mistake of bedding a new plywood outboard motor pad on my transom using silicone. When I had to replace the pad, one year later, I couldn't remove it.

Using wooden wedges and many blows with a heavy hammer I was finally able to pry it off the boat. I thought it was going to take the gelcoat with it. Then came the virtually impossible task of peeling, scrapping, and cursing, @#$%^&, the residue off.

Silcone is pure evil!

Lyman

[tartan30cirrus]

I would think a polyurethane 42/5200 would be even stronger than silicone.

[dasein668]

I would think a polyurethane 42/5200 would be even stronger than silicone.

Polyurethane isn't really good for normal bedding. It's primarily an adhesive, which also works as a sealant, so yes, it is in fact stronger than silicone. The real problem with silicone is that it tends to leave a thin rubbery film which is very difficult if not impossible to remove.

[tartan30cirrus]

It seriously sounds like there is $ to be made by whoever invents the stuff that will remove silicone...is it just a coincidence by the way that the mineral quartz -- pure Si -- is the stablest, most resistent mineral on earth??? Things that make you go hmmmm.