Proseal vs automotive seam sealer

[Weefle]

I know some folks are using proseal to bridge the overlap seams prior to paint. Question is has anyone used automotive seam sealer for the same purpose? Any experience with either method appreciated. Also do you apply the seam sealer after Alodine and prior to prime or after prime?

thanks

Keith

 

[Jim F]

Better check with your painter! The guy who did mine wanted nothing that would be under the paint.
A friend had gone from a polished airframe to paint and the residue in the seams caused huge problems

 

[PaulvS]

I wonder which seams they are sealing and what is the intent? Generally the skins will overlap tightly and it won't be easy to get much sealant in there after construction.

 

[noahhl]

I didn't use it on overlap seams, but did use some seam sealer on the gear leg and step penetrations (and maybe a few other places that aren't coming to mind -- I used less than a half tube on the whole plane). After interior priming, before exterior paint. No compatibility issues with Stewart Systems on my DIY paint job.

 

[fixnflyguy]

At my day job working heavy jet overhaul, we use Proseal and derivatives for pretty much everything that needs sealed, for pressurization, fuel tanks, and water incursion. In the large aircraft world, every piece of skin is installed "wet' with fay surface sealant, and the finished edges are wiped smooth and clean. Afterwards, some are edge sealed as you are describing. In GA/Experimental, that edge is extremely thin, thus the fillet edge seal is very minimal. Sealant is usually applied to PROPERLY primed skin surfaces. Final external paint preparation requires a gentle hand and Scotchbrite scuff prior to paint. I also work as an APIA in the GA world, and built my -4. I fay/seam sealed only 1 seam on my plane, and that was the belly seam down the centerline. I am not a fan of trying to seam seal light aircraft, as there is minimal sealant retention area, and a good paint job over good sheetmetal work will leave a filled joint. Bigger gaps as noahhl mentioned are best filled with Proseal type material as it is compatible with topcoats and resistant to oils and such. if you lived close by, Id give you all the tubes of Proseal you want.

 

[Weefle]

Hey guys,

I will answer my own question.
After trying the automotive seam sealer then proseal….its hand down proseal. The auto stuff sets up way too fast to get a nice bead, impossible to work it in place. Yes proseal is messy but it took me about 3.5 hours to tape and proseal then remove the tape. Just wear some Tyvek and gloves and your good.

keith

 

[rockyfatcat]

Hey guys,

I will answer my own question.
After trying the automotive seam sealer then proseal….its hand down proseal. The auto stuff sets up way too fast to get a nice bead, impossible to work it in place. Yes proseal is messy but it took me about 3.5 hours to tape and proseal then remove the tape. Just wear some Tyvek and gloves and your good.

keith

It's all about the prep work. As fixnflyguy said, the big boy jets get everything sealed with some flavor of B-1/2 polysulfide sealant. There is an art to laying out the tape. Not too close, and not too far from the edge of the panel. If you do it right you can pull off the tape as a single continuous piece and straight into the trash without getting any sealant on your fingers.

The other trick is how much sealant to apply. The perfect amount will smoosh into the panel gap and push a small continuous blob ahead of a popsicle stick to fill in any voids. You don't want any gaps or air bubbles.

The airlines aren't too particular about pretty, but they do not want any voids. Owners of private jet and the repair stations will have you hand painting the screw heads and the sealant with a tiny art paint brush.