removing caulk, and recaulking with a two-finger method

[Bob Blarney]

Hello,

Maybe the notes of my recaulking the roof gutter may be of use to others. On this trailer, the entire left side had been replaced at a dealer, using pop-rivets with an occasonal Olympic rivet (left un-trimmed)

1, The old caulk (Vulkem? DiCor?) was slathered on thick and wiped roughly, forming ridges & dams for water to collect. The holes of the pop-rivets were open. Silicone caulk had been used under the rail.

2. I cut away as much of the thick caulk as possible, and noticed that where it had been thickly applied, that it had a tendency to crack. Where it was thin, it was still firmly adhered to the roof and rail. I used a crank-neck woodworking chisel to cut away the caulk and silicone, and scrubbed hard with a stiff brush. I blew away the debris with a compressed air jet to be sure it all loose dirt and tag-ends were gone.

3. I scrubbed the surfaces with a microfiber cloth and 50/50 water/isopropyl alcohol, and let it dry overnight.

4. The next morning, after blowing away any dirt again, and reinspecting the surface, I applied Sikaflex 221 into the roof-gutter groove and over the pop-rivets.

5. While wearing a vinyl glove, I dipped my fingers in naptha or mineral spirits, and feathered the Sikaflex smooth, using two fingers. The upper (middle finger) was just above the upper margin of the caulk bead, and forced the excess toward the forefinger, which also worked the caulk into the groove. (In the pic, i repeated the finger smoothing to eliminate the ridge under my forefinger.)

6. I discarded gloves as they became too gooey with caulk to feather the edge properly.

I think that I've feathered the edge well and covered the rivet holes, but I'll inspect it again tomorrow to see if any spots have been missed.

[Too tall]

Looks good

Is Sikaflex 221 the "go to" caulk for Airstreams?

[Bob Blarney]

Originally Posted by Too tall

Looks good

Is Sikaflex 221 the "go to" caulk for Airstreams?

That's a good question. It is one that is favored by many, and apparently it produces predictable results. Other caulks are Vulkem (sic?) and DiCor, and there are similar polyurethane formulations by other brand names. The choice may be a matter of following another person's experience, or it could just be a case of 'I know what I like, and I like what I know'.

I almost applied products by Sashco, called Lexel and its brushable form called 'Through the Roof', which is a thermoplastic suspended in solvents (primarily naphtha and toluene). It appears to be a good transparent elastic sealant that can be applied under adverse circumstances, but i didn't see any means to remove it if that should be necessary. On the other, the Sikaflex221 data sheet lists what chemicals it is, and is not, resistant to degradation.

[Too tall]

Originally Posted by Bob Blarney

That's a good question. It is one that is favored by many, and apparently it produces predictable results. Other caulks are Vulkem (sic?) and DiCor, and there are similar polyurethane formulations by other brand names. The choice may be a matter of following another person's experience, or it could just be a case of 'I know what I like, and I like what I know'.

I almost applied products by Sashco, called Lexel and its brushable form called 'Through the Roof', which is a thermoplastic suspended in solvents (primarily naphtha and toluene). It appears to be a good transparent elastic sealant that can be applied under adverse circumstances, but i didn't see any means to remove it if that should be necessary. On the other, the Sikaflex221 data sheet lists what chemicals it is, and is not, resistant to degradation.

Good read Bob thanks. I'll pencil in Sikaflex221 as leading the pack for now. I have a 2017 FC inbound and plan to do some preventive maintenance.I've never owned a trailer that did not need some re-caulking.

[SCOTTinNJ]

Originally Posted by Bob Blarney

3. I scrubbed the surfaces with a microfiber cloth and 50/50 water/isopropyl alcohol, and let it dry overnight.

4. The next morning, after blowing away any dirt again, and reinspecting the surface, I applied Sikaflex 221 into the roof-gutter groove and over the pop-rivets.

Lewster always says not to use alcohol prior to Sikaflex. See:

http://www.airforums.com/forums/f456...ml#post1549683

[Bob Blarney]

Originally Posted by SCOTTinNJ

Lewster always says not to use alcohol prior to Sikaflex. See:

http://www.airforums.com/forums/f456...ml#post1549683

I did read the Lewster advice, and I also read the Sika Datasheet, about the incompatibility of 221 with alcohols. (I actually considered that alcohol might be useful for removing the Sikaflex in the indefinite future.) Perhaps I should have been more explicit, but you will note above, that I cleaned with the 50/50 alcohol, and then waited overnight.

Alcohol evaporates much quicker than water, and so by the following morning, the alcohol had evaporated off, and also by the time that the dew had burned off in the late morning sunshine, the surfaces were quite dry and clean. Also, the materials involve were not absorbent and so they would not retain alcohol, and the compressed air jet also accelerated the displacement and evaporation of water/alcohol mixture.

You might also consider why I used 50/50 water/alcohol (which mix freely). It was because I thought that some of the surface contaminats were water soluble, and other contaminants would not dissolve in water and so the alcohol would solubilize them. If that didn't work, then I tried naphtha and mineral spirits. And also I knew that the isopropyl alcohol would evaporate quickly and leave no residue.

[SilverHouseDreams]

From the product data sheet:

Sikaflex Primer 260 promotes adhesion of urethane sealants to various metallic, non-metallic, and plastic substrates.

Sikaflex Primer 260: flammable; irritant; Poison - Contains methanol. May cause skin/eye/respiratory irritation. Avoid contact. Methanol is a poison and may cause blindness if ingested. Use only with adequate ventilation. Use of safety goggles and chemical resistant gloves is recommended. In case of exceedance of PELs, use an appropriate, properly tted NIOSH approved respirator. Remove contaminated clothing. Keep away from heat, sparks, and open flames.

[rmkrum]

To me, this looks like methanol instead of isopropyl alcohol would be a good idea...use with caution, as methanol is in fact poisonous.

[SCOTTinNJ]

Originally Posted by Bob Blarney

I did read the Lewster advice, and I also read the Sika Datasheet, about the incompatibility of 221 with alcohols. (I actually considered that alcohol might be useful for removing the Sikaflex in the indefinite future.) Perhaps I should have been more explicit, but you will note above, that I cleaned with the 50/50 alcohol, and then waited overnight.

Alcohol evaporates much quicker than water, and so by the following morning, the alcohol had evaporated off, and also by the time that the dew had burned off in the late morning sunshine, the surfaces were quite dry and clean. Also, the materials involve were not absorbent and so they would not retain alcohol, and the compressed air jet also accelerated the displacement and evaporation of water/alcohol mixture.

You might also consider why I used 50/50 water/alcohol (which mix freely). It was because I thought that some of the surface contaminats were water soluble, and other contaminants would not dissolve in water and so the alcohol would solubilize them. If that didn't work, then I tried naphtha and mineral spirits. And also I knew that the isopropyl alcohol would evaporate quickly and leave no residue.

Ok. Wasn't sure you knew. Obviously you thought it out.

[Bob Blarney]

Originally Posted by rmkrum

To me, this looks like methanol instead of isopropyl alcohol would be a good idea...use with caution, as methanol is in fact poisonous.

I think it depends upon what you wish to accomplish. I intended to clean the surface using a relatively safe method. Priming, on the other hand, is meant to promote adhesion by etching into an existing surface or providing a layer that is compatible with both the old surface and new.

It should be noted that while all alcohols are toxic, methanol is much more toxic than ethanol or isopropyl alcohol. The effects of isopropyl alcohol intoxication are similar to ethanol, and the use of gloves and good ventilation are recommended.

On a side note, to make up a 50/50 mixture, one can dilute either 70% (or 91%) drugstore alcohol in measuring cup. I thought of 10 oz. as 7 oz. alcohol and 3 oz. water, and so to make a 50% solution, I only needed to add 4 oz. of water.