Why I Don't Like Silicone

[Maine Sail]

Those who know me know that I use some pretty strong cautions when discussing the use of silicone on boats. There are places where it is certainly necessary, Beckson products for example, but beyond those few instances it can be one of the most contaminating substances on a boat.

I rebedded this chain plate recently and found it to the a perfect example of just why silicone, can be such a bad choice of product for some applications.

The owner of this boat potted all his chain plates sealing the surrounding core from moisture, a real +1 !! He then proceeded to bed them with silicone a -100......Doh'...... They then leaked pretty quickly. He then judiciously cleaned the surfaces of what he assumed was all the silicone, using multiple chemicals such as Acetone, MEK and Toluene, and re-bedded but......

This is how the cover plate came off after being bedded with a "polyurethane marine sealant"... One small area of adhesion and the rest was stuck like an egg in a non-stick frying pan.

And how the cover plate came off... The brownish color is mold & mildew from water sitting in there. The new sealant stuck to NOTHING due to the contamination from the previous bedding job.. Trust me, if you THINK you got all the silicone, think again....

Just this one chain plate took nearly an hour with grinders, ScotchBrite, sand paper, a Dremel and lots of Acetone to get it clean enough to re-bed.

Please think of these photo BEFORE you bed stuff on your boat...

 

[Allan12210]

Not a bad product, a bad choice. Everything has its ideal application. Crossing that line leads to trouble.

I do note in the photos that the stainless to silicone bond is much better than the bond to the fiberglass. Makes me think that the mold release or wax layer was not properly removed. This will effect the adhesion ability of any sealant (even the right one).

 

[Maine Sail]

Not a bad product, a bad choice. Everything has its ideal application. Crossing that line leads to trouble.

I do note in the photos that the stainless to silicone bond is much better than the bond to the fiberglass. Makes me think that the mold release or wax layer was not properly removed. This will effect the adhesion ability of any sealant (even the right one).

That bit of clear silicone was added after it leaked, as a Band-Aid. It was added above the cover plate in a last ditch attempt to try and minimize the leak. This was done after he had re-bedded it and cleaned it after the first leaking silicone job which had been a white silicone, not clear. The original install was de-waxed and cleaned before sealing as confirmed by the owner.. I clean amine blush all the time and never have an issue with it. This contamination was much more severe.

 

[Stu Jackson]

KISS.

I have learned a great deal from Maine Sail over the years.

Silicone is good for Beckson ports. That's about all.

Use butyl tape for bedding hardware and for chainplates.

What else is there?

Really...

 

[caguy]

KISS.

I have learned a great deal from Maine Sail over the years.

Silicone is good for Beckson ports. That's about all.

Use butyl tape for bedding hardware and for chainplates.

What else is there?

Really...

Why Beckson ports? I had planned on using butyl sealer on my Beckson ports. Is that a bad idea?

 

[Charlie13958]

Silicone is for boobs!

 

[Merlin Clark]

Why Beckson ports? I had planned on using butyl sealer on my Beckson ports. Is that a bad idea?

I like using butyl for everything I can but used silicone because Beckson calls for it in bedding their ports. http://www.beckson.com/installport.html
Also, I made a polycarbonate dead light to fill the hole left by removing a dead solar vent in my fwd hatch and the manufacturer called for silicone sealant. I read later (and in the boatus article) that acrylic also requires silicone. I followed the "complete the install, let bedding dry, then tighten" method and it's worked fine.

Don Casey on silicone (http://www.boatus.com/boattech/casey/sealant.asp)
Calling silicone a sealant is something of a misrepresentation. It is more accurate to characterize it as a gasket material. If you accept silicone's adhesive abilities as temporary, you will find it is the best product for a number of sealing requirements. It is the only one of the marine sealant trio than can be safely used to bed plastic. It is an excellent insulator between dissimilar metals--use it when mounting stainless hardware to an aluminum spar. It is the perfect gasket material between components that must be periodically dismantled--beneath hatch slides, for example.

I'll stick with butyl for anything I can use it on. It's just too easy, clean and handy.

 

[Graycruiser]

When I bought my PVC dinghy, the dealer told me to never use a silicone based product on the PVC as it is impossible to remove and makes repair also impossible.

 

[Stu Jackson]

Why Beckson ports? I had planned on using butyl sealer on my Beckson ports. Is that a bad idea?

Frank, it's because what Beckson says to use.

 

[cs27ravat]

Interesting... I'm installing a 8" Beckson port in the top of a typical plastic waste holding tank, and the vendor told me to bed that port in butyl.

 

[caguy]

I just got a call back from Beckson and he said that the Butyl will not harm the ports but they still recommend the Silicone because if flows better into the nooks and crannies better than Butyl. I explained to him that I was partial to Butyl and he explained that many people are but they still feel that Silicone is more suitable their needs. I told him that they were unused older gray ports. He explained that Silicone comes in gray. I didn't want to be rude so I did not mention that all of the Butyl tape I have on hand is gray.
I will be mounting the windows this week.

Any thoughts?

 

[Maine Sail]

I just got a call back from Beckson and he said that the Butyl will not harm the ports but they still recommend the Silicone because if flows better into the nooks and crannies better than Butyl. I explained to him that I was partial to Butyl and he explained that many people are but they still feel that Silicone is more suitable their needs. I told him that they were unused older gray ports. He explained that Silicone comes in gray. I didn't want to be rude so I did not mention that all of the Butyl tape I have on hand is gray.
I will be mounting the windows this week.

Any thoughts?

You can mount the ports from inside and seal them to the hull with butyl but the trim rings do work best with Silicone holding them on, if not through bolting. They are too flimsy to compress the butyl well if you use the bolt through method. If gluing them on as decorative trim rings then I still vote for silicone for that application. There is no problem mixing butyl & silicone so you could do ports/butyl and trim rings/silicone. .

 

[caguy]

There is also a butyl sealant that comes in a tube that has the same consistency as silicone. It skins out better and is tougher than silicone.

 

[SailingHarry]

So I've spent the last few days on my hands and knees working on my chainplates. Removed the chainplates, cleaned, dye-penetrant tested, routed out and filled the core, the works. I've become quite "intimate" with this part of my boat. And, based upon nothing more than that 6" square photograph, I'm wiling to bet a beer (maybe even some rum!) that this is a picture of a Sabre. Mine is a '79 S34.

Harry
Rantum Scoot
'79 S34-I #063
Mill Creek, Annapolis

 

[Maine Sail]

So I've spent the last few days on my hands and knees working on my chainplates. Removed the chainplates, cleaned, dye-penetrant tested, routed out and filled the core, the works. I've become quite "intimate" with this part of my boat. And, based upon nothing more than that 6" square photograph, I'm wiling to bet a beer (maybe even some rum!) that this is a picture of a Sabre. Mine is a '79 S34.

Harry
Rantum Scoot
'79 S34-I #063
Mill Creek, Annapolis

Bingo..!

 

[SailingHarry]

The fact that I guessed right is a poor reflection on my social life....

Harry

 

[malyea]

A few months ago r/r all 9 Gray portlights on my '82 H30 and (per manf rec) used silicon. Quite pleased with the outcome,except....around the exterior of the trim ring where a fine line of silicon is exposed to the elements (rain, dirt, pollen, bs, etc) it appears that dirt/mildew/grunge is adhearing/growing/homesteading to the silicon - rather unsightly....remedy? It doesn't come off with regular wash/rinse cycle using basic 'boat soap' and elbow grease....