Why not Silicone?

[melissab]

Hello, I've been reading through threads and noticed a strong recomendation against Silicone but I have not been able to find out why? Could somebody enlighten us? When looking at trailers if we see Silicone we'd like to know what we could be in for in the way of problems etc.

Thanks!

[Raya]

Oh, this thread was made for me!

Well, for starters, silicone does not do the best job at sealing, in my opinion. But even if you feel it does, the negatives outweigh that, I feel, and there is always another sealant that will work at least as well, without the negatives.

The first big negative is that that when it does fail (and it will), it is nearly impossible to remove. Doubly annoying when it is no longer doing its job. When I say "nearly impossible," I really mean #/*%& difficult.

As it that were not bad enough, it is also a very powerful contaminant. Once you have silicone oil/residue on your fiberglass, it is extremely difficult to get anything else to stick to it. "Anything else" including any new sealant, or... worse... fiberglass, paint, or gelcoat. Even when you manage to get all the visible silicone off (and have fun with that), it leaves an invisible contaminant behind for "the gift that keeps on giving"

Just go to any body/paint shop and ask them if you can bring some silicone in....

And for the final insult, when you are sanding/scraping/hacking away at the silicone that no longer is doing its job (and which another sealant could have done better), you are very likely to spread the contaminant, and to dig it further into your gelcoat.

Contrast this with butyl, which seals effectively for decades, and also does not harm plastics; yet comes off like a breeze

Many other sealants can be used as well, depending on what you are sealing, and how you need to balance the sealant/adhesion equation (polyurethane, polysulfide, etc.)

Whew!

Raya

[Vickie B.]

Sure glad melissa asked this question, as I was going to pm Raya and ask her this very question before I take Bean in tomorrow for an estimate of possible work.

[Raya]

Moi?

[melissab]

Thank you for that very educational and entertaining explanation. I LOVE your Smileys for emphasis! Given this perfectly logical reason for not using Silicone, why on earth would Scamp use Silicone for KarenH's repairs at the factory referenced in her thread? Does that mean they are using Silicone on their new orders? If so, can you request something else be used other than Silicone?

[Raya]

You know, I have never figured out *why* silicone is so popular. It think it has something to do with how it's clear and kind of "knox blocks" jiggly. Maybe it seems less intimidatingly "caulk like" that way

I have to say, out of all the trailers I looked at, hardly a one did not have silicone globbed on around the edges of the windows or belly band (where it wouldn't do much good even if it were good caulk).

It just seems to *attract* people :dumbfounded:

It's the same way with boats, if that's any comfort.

As to why builder would use it. Well, I don't know. I guess being clear it is somewhat more "forgiving" if your application is not perfectly tidy; and of course they don't have to remove it or paint the trailer later.

On the other hand, what could be easier to use than butyl tape?

[Cam A]

The single worst, most hated, took-the-longest, task I ever undertook on my old trailer was removing the silicon that the former owner had liberally gooped on everything. I still spit when I hear the word. Yes, that bad.

[Mark J]

I purchased a trailer a couple of years ago that the previous owner caulked it up very nicely for the next buyer! At the time I wasn't totally aware of the problem silicone brings or I may have passed up the purchase.

I have been thinking about removing it, then I read reports about how difficult it is to remove and sit back and think some more...

The entire door seal is calked and much on the roof around the vent as well as several other places.

One question I've had is how do I know if the caulk used was silcone or had silcone in it? It seems like there are a 100 varieties of caulk out there. And should I remove it? <_<

[Raya]

Hi Mark,

I usually see people using the clear silicone on trailers. So clear caulk would be a major clue. I have seen it in white too, although of course there are many white caulks. It's very shiny and kind of "hard jelly" like. Very "rubbery." Kind of bouncy and Silly Putty-ish.

It will hold very tenaciously to aluminum, so if there is any on the belly band or window frames, you could try giving it a tug.

I know, that sounds like it would describe, say, a polyurethane caulk, too. Which it kind of does, but not really once you know the difference (in which case you would not be asking though!).

Raya

[mcbrew]

Polyurethane caulk is a little more frustrating to apply, in my opinion... but it cleans up really easily with mineral spirits. Silicone is a nightmare to clean up. I am just getting ready to install a new escape hatch/vent on my Scamp (as soon as it arrives) and I will be picking up the putty tape at the local RV shop during my lunch break today. I also picked up a pack of the plastic spacers and white snap caps like Scamp uses on the rivets. I hope to be able to use those on the vent instead of screws/rivets with gobs of caulk over them.

[Raya]

Another option is to use machine screws/nuts. Since there is then no hole through the middle, you don't need to caulk over them.

(As you can probably guess, big Dairy Queen dollops on the top of fastener heads drive me nuts too, even if they are not silicone. )

[Vickie B.]

Hey Raya,

Took Bean in to the Body Shop armed with a copy of your post about silicone!
Didn't even need it! Ben said his employees "run" out the back door when they see silicone!

[mcbrew]

I spent half the day today replacing the escape hatch/vent on my '84 Scamp. I was surprised to find that it was installed with silicone. What a mess! I spent a LOT of time scraping and scrubbing. I finally used sand paper to get down to the gelcoat. Well, at least the new vent is properly installed. I only have to trim the interior trim ring and the job will be finished.

Almost ready for my first "camping" trip next weekend. I will most likely be in my in-laws' driveway.

[Jon W]

My rig came with about 47lbs of white silicone stuck in every imaginable nook, cranny and crevice and, yes, under all of the rivets and remounted windows and top vent. The original owner of my trailer left it in his back yard for several years to weather, and his wife left it there for a few more after he died. I guess he would have wanted it that way...

The next owner, a neighbor, looked upon this trailer with great covetousness, with the elderly missus refusing his offers. She finally caved when she had to clean the place out to move. I'm sure he got a good deal. He thought he did a great job reviving it after it leaked and got moldy. Being new to this, I had no idea what I was getting into. It looked like he fixed the leaks and all it needed was a new rear floor panel, some wiring and new floor covering to replace that lovely mustard-yellow carpet.

WRONG!!! I'm not sure whether it was the leaking water or just sitting out in the sun without a cover, but the Ensolite liner started separating from the shell in lots of places where I started scrubbing it hard. I also had to replace the entire floor, even the patch under the fridge the last guy replaced because he botched it. At that point, I decided to remove the windows and clean them up. That was when I descended into the depths of silicone caulk purgatory.

Ah, but while working on a lab construction project where I work, I made a trip to Home Depot to buy building materials - including silicone caulk. In the caulking section, I stumbled upon a few different varieties of a product called Mötsenböcker's Liftoff, including this one: http://www.liftoffinc.com/product-sealant-remover.php
Some people give this product poor reviews, but I've found that you just have to give the stuff time to work. Since I plan to repaint anyway (now that it's this far apart, I might as well), I can live with the minor marring caused by the soft polypropylene scraper I used with the Liftoff. It didn't seem to hurt the gelcoat any, either. With a little elbow grease, the caulk comes off surprisingly cleanly. OTOH, their glue and bubblegum remover didn't work so well on my old decals and stickers. Gentle heat from a hair dryer (never got it so hot I couldn't keep my fingers under it) made the labels peel right off. Acetone got rid of the adhesive goop.

The thing I wasn't aware of is possible paint adhesion problems caused by silicone caulk migrating into the old gelcoat. If this is the case, I'm in deep trouble. I used black Herculiner as undercoating on my frame. Maybe I'll use it on the shell, too. Either that, or else I could maybe coat it with asphalt and throw some sand on it...

[Raya]

Jon,

Oh man, I feel your pain

Don't you wish we could put up a billboard? Sheesh!

One way you can test your gelcoat is by just putting water on it. If it sort of "runs away" then you have a contamination problem of some type. What you want is for it to just lie there in a big sheet (of water).

I don't know if the one big sheet of water means you are in the clear for sure, once it comes to paint (I am not a professional painter); but I do know that the "running away" (where the water doesn't sheet but separates into separate pools) means the surface is not "clean" enough.

That's interesting info about the product you used. I, too, wonder how it did against the silicone oil/contamination.

I'm sorry you have had to tackle this problem Lucky for your Scamp to have you though

Raya

[mcbrew]

Originally Posted by Jon W

or else I could maybe coat it with asphalt and throw some sand on it...

Better upgrade your axle first!

[mcbrew]

By the way... I love "targeted" advertising. On the right side of the screen there are four ads for silicone sealants. I guess Yahoo's system isn't smart enough to know that we are talking about how much we HATE silicone in this thread!

[Raya]

Yeah, where are the ads for easy silicone *remover*?

Oh wait, there isn't any.

/snark

PS: Melissa, thanks for starting this thread. In addition to information, it has given us a place to vent our frustrations