Why not silicone? (Split from Forums 101)

[JHayter]

(Moderator's note: Originally posted in response to a comment on the "Forums 101" thread, this question been moved here where it might receive more and better responses.)

I have seen lots of people say don't use silicone on here, but I haven't seen anyone say why. Can someone tell me why silicone is a NO NO on Fiberglass? Does it damage the Fiberglass, does it just not hold up or is it the mess of cleaning it up when it is time to replace? I honestly don't know and would like the answer to pass on to my husband who believes silicone it Gods greatest gift next to Duct tape! I know Donna D. is cringing at the thought of it!
Thanks!


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[Franswa]

but I'm like your husband I guess and have used silicone lots...never had a problem with it....especially if you just tinghten the fasteners to "finger tight" first, leave it for a few hours, and then thighten fully (creates it's own gasket however uneven the surface is)

the main complaint about silicone is how hard the clean up /stripping is...but if you never have to replace/reseal the thing...where's the problem?....clean up right at application time is easy after all.....I dunno

I have it on my list to buy a tube of "Sikaflex" (?)....I heard from friends that it is the "cat's meow" in that department....seals like mad, stays flexible over time....yada yada.....costs about double but worth every penny apparently

silicone hurting fiberglass??? Naw.

[C&G in FL]

Originally Posted by Franswa

the main complaint about silicone is how hard the clean up /stripping is...but if you never have to replace/reseal the thing...where's the problem?

Like the title of the James Bond movie, Never say Never. If your husband ever has to resell a vent fan or other structure on the trailer, he will no longer think of silicon as God's greatest gift but a work of the devil.


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[C&G in FL]

Originally Posted by CPW

Like the title of the James Bond movie, Never say Never. If your husband ever has to resell a vent fan or other structure on the trailer, he will no longer think of silicon as God's greatest gift but a work of the devil.

And gaffer's tape is far superior to duct tape in that is does not leave a residue after it has been left in place for a period of time, yet is as versatile as duct tape.


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[papa-t]

Good answers

[Morganza]

I've never added silicone to my Scamp but I have removed it, when I added an outside plug for the power supply cord. Getting it off was pretty tedious as it was spread thin over about 1/2" or so away from where it was really needed. After wearing the skin off of my thumb, I found that I could get it off easily and safely using a scraper that I had for scraping grip wax from skis. It worked great and didn't damage the surface. The scraper is nothing more that a piece of 5mm thick plexiglass with a very clean, sharp edge. This was a very small area of silicone being removed. A large removal project could become tiresome.

[Bob Miller]

While removing traces of silicone sealer may be a pain, as many have learned the hard way, it just doesn't stay stuck to fiberglass/gelcoat very well. Many has been the time that I have peeled off 3' long strips of silicone used to seal around windows and side seams on molded fiberglass RV's of all shapes and sizes. Silicone will let a leak start in one place that will show up inside 24" away.


My basic rule, "If you want to know where the next leak will be, seal the old one with silicone.


BTW: Sikaflex RV products are entirely different and are designed to be used on RV's, including fiberglass surfaces. They cost more and are worth the cost because they work.....

[David Tilston]

Unlike calk, silicone will not self repair. It typically fails after about 3 years, then NOTHING will stick where it was.

[Ian G.]

One of the primary issues in my mind is that silicon is used to try to repair a leaks by caulking around the leaking item. A leak cannot be repaired in this manner, the window or whatever is leaking has to be removed and resealed properly using butyl tape.

The second issue with silicon is for it to stick properly the surface must be completely clean with no dust, dirt or residue, fiberglass gel coat forms an oxidation layer that looks like fine dust, this can be seen by rubbing your finger across the surface, wax, oil or other contaminates can also prevent it from sticking, if not cleaned completely the silicon will not stick, any area of silicon that has released from the surface will allow water to penetrate.

The third reason is if you get the silicon to stick and have to do any work or repairs in that area then removing it is a nightmare.

The easier solution is correct sealing with butyl tape which remains far more flexible than silicon for decades, although cleaning the surface is still important when installing, it remains sticky and will reseal itself, and although the cleanup of butyl tape is messy it can be completely removed

[Bob Miller]

To 2nd Ians advice:


You can also carry a small strip of Butyl tape in a baggie and, if you do get a leak, you can usually make a satisfactory temporary repair and stop the leak from the outside of the frame or where it is leaking, even if the surface is still wet.

[sarahspins]

Originally Posted by Ian G.

One of the primary issues in my mind is that silicon is used to try to repair a leaks by caulking around the leaking item. A leak cannot be repaired in this manner, the window or whatever is leaking has to be removed and resealed properly using butyl tape.

Exactly... and silicone doesn't stick to silicone, which makes it even more useless when people in the future try to "re-fix" some of those leaks. I just replaced the escape hatch on my scamp, and there was butyl putty (I think from the original install of this hatch, which may not be the original to the camper), butyl tape (likely the only prior owner attempting to re-seal the hatch correctly, which probably worked just fine for a while), and then at least 3 different kinds of silicone, some of which was even far underneath the plastic flange - I know this because they were different colors. There was also an assortment of rivet sizes used - I suspect that some may have fallen out over time and been replaced - or not replaced quickly, which accounts for some of the silicone underneath.

All of the silicone peeled off easily (as it has on other areas of my camper as well) - some of the butyl putty was more reluctant to come off, the butyl tape was really the only thing that required actual work to get off as I prepped the surface for new installing the new hatch.

[Elly G]

Sikaflex looks like great alternative. Does it come in any other form other than tubes for caulk guns?

[Thom Rowland]

I worked as a maintenance technician for a major airline for over 30 years. We used silicon as a sealant all the time. The only time I saw any failure of the silicone was when it was IMPROPERLY applied (failure to properly prep the surfaces to be sealed). We used it on fiberglass, plastic, aluminum, rubber and many other materials and did not have a problem with it. Preparing the surfaces that were previously sealed with silicone was not as difficult as everyone here seems to think. As Morganza stated using a plastic scraper will remove the majority of the silicone, rubbing with your fingers will remove the rest, then cleaning the surfaces with acetone will remove the remaining residue. If you are very careful, you can use a single edge razor blade instead of the plastic scraper. Yes, the silicone takes some work to remove when resealing a window but that's what makes it work so good as a sealer. Excellent bonding and adhesion makes a good seal but also makes it difficult to remove later.

[JHayter]

Thank you for all of your advise and information! I bought a 1980 Scamp in KY 2 weekends ago. It was listed as Excellent condition and NO Leaks! All this camper has done is leak. The roof vent has been taken care of with SILICONE!!! Crud, now we know that is not the best idea. Next on our list is the side window that is leaking and the Lg rear window that is leaking. We will use B. tape on the side window, but the rear has me perplexed. I have watched videos and feel fairly confident, but actually not so much! Lol.... I can't find the Lock strip tool here in town and I don't want to take the time to order one as this needs taken care of ASAP. There is a constant river flowing in when it rains even the slightest bit. Any suggestions on the rear window would be much appreciated! Maybe one day I will be able to help instead of needing help??? Thanks again for all of your response!

[JHayter]

Thanks! I needed to hear that and my husband will be equally happy to know I am not going to go into panic mode over a little silicon.

[sarahspins]

Originally Posted by JHayter

the rear has me perplexed. I have watched videos and feel fairly confident, but actually not so much! Lol.... I can't find the Lock strip tool here in town and I don't want to take the time to order one as this needs taken care of ASAP.

I got mine from amazon - http://www.amazon.com/Lisle-47000-Wi...dp/B000COA1CQ/

If you have prime you get it in 2 days, or you can pay an extra $4 and get it overnight.

You don't mention if you have the replacement seal already for the rear window, but the lockstrip tool won't do you much good without it - and my seal took about a week to get to me when I ordered it from scamp, I had the tool itself MUCH faster

The rear window is also the easier of the two to install - the front is trickier because it has more of a curve to it.

[Jack L]

Originally Posted by global2edg

Sikaflex looks like great alternative. Does it come in any other form other than tubes for caulk guns?

I've used it many times on boats and it's great. I've only seen it in small squeeze tubes or caulk gun cartridges. After it's opened, it should be used quickly. Bu that, I mean if you go back a month later the remainder of the product may be unusable. Also it is very difficult to take something apart later. It does a wonderful job if properly used but should also be considered permanent. If you think silicone is hard to remove, this is lots more difficult to remove.

[Bob Miller]

CLIP-----"[QUOTE=Thom Rowland;512358]I worked as a maintenance technician for a major airline for over 30 years. We used silicon as a sealant all the time."

I am just repeating the observations I have made working on molded fiberglass RV's for a number of years.

Besides the technicians being well paid and trained to do proper prep first, one would hope that the silicone sealant used in aircraft applications isn't the same stuff as RV peeps are buying at their local Home Depot.

Once, when I was in Germany, I was given a roll of repair tape. It was intended for emergency military aircraft repair and it was labeled "Sub Sonic use only" Although it looks the same, I think that it too was somewhat different than the Duct Tape we know, use and love.

Let me guess: Aircraft grade silicone sealant = $50 a tube?

[David Tilston]

It should also be noted that if you have a propane detector in your trailer, you should turn it off if using silicone. The gas that comes off as the silicone dries KILLS the sensor.

[Byron Kinnaman]

The anti silicone sealants is based on nonsense and lack of knowledge. There's many many types of silicon sealant out there. A person needs to do a bit of research to know which one to use. There is NO one size fits all. Some clean up with a bit more effort than others. That may be the one that works the best.
It's not much different than other types of adhesives, some work good under one condition and not well under other conditions.
Go to your local home depot or Lowes and see how many different tubes of silicone sealants are on the shelf.