Panel Bond

[RICH MUISE]

I've a question for PAT FLEISHMAN.........I'm posting it here because the info may be of interest to a lot of members.
I'm getting close to repairing an expensive rookie mistake I made on my roof's driprail gutters. Way back when I first started working on the car, I started on the roof first.  I had used seam sealer over zinc phosphate coating prior to epoxy primer. Anyone who has stripped a '57 knows the factory laid down all the seam sealer on floorboards, etc prior to prime and paint, so that's why I did it that way.
First mistake was leaving the zinc phosphate coating under the seam sealer, second mistake was not epoxy priming before seam sealer. Both mistakes contributed to an adhesion problem and I now have bubbling all around the driprail

Pat, (suede57)who is a 3M rep, had told me a while back he epoxy primes first, then uses panel bond adhesive in place of the normal seam sealer we're all use to. My question for Pat is ...are there more than one 3m panel bond adhesives, and if so, which one do you use for what I've described. Also any hints or suggestions for application would be appreciated

[suede57ford]

The drip rail originally uses a sealer called "Drip Check " sealer.   it was designed to go in the channel and shrink as it dried creating a meniscus(concave shape).  The problem with that outdated product is it would continue to shrink and crack, and the product is a very old technology seam sealer that has a short life.

Seam Sealer has come a long ways in just the last few years.

3M offers several types of sealers for drip rail channels depending on what shape the factory applied sealer looked like.

I'm only going to discuss two-part seam sealers which work by squeezing through an applicator gun and mixing tip.   I do not recommend using any one-part seam sealers for the roof ditch because they can continue to shrink and crack and tooling to get a good appearance is difficult.  If it is  a seam sealer in an older style cartridge, it is an older technology product and I would not use it anywhere because of the shrinkage and cracking.

There are Flowable and Controlled flow seam sealers which work good for a deep trough on a fairly flat roof or channel.  These do not work good for our cars as the channel has to much slope and it will run out before drying. 

One important note that most people are not aware of is that nearly every seam sealer on the market are not designed to be put over bare metal, despite that many techs have been in the past.   Most modern seam sealers have no corrosion protection properties and must be used over catalyzed urethane or epoxy primers.   Never put seam sealer over any type of spray can or etch primer no matter how convenient it seems.  Any thing with an etch(acid) or 1K(spray can) will lead to failure of adhesion of the seam sealer.   I realize this seems like a huge pain but we must develop the habit of  priming all bare metal and seems before applying seam sealer!  The reason why these cars rusted out originally is that there was no corrosion protection and we are rebuilding these cars to survive.  We do offer a two-part Bare-Metal seam sealer, but it is too flexible and hard to tool out to the final shape.   It works really well on floor pans and body seams.   

One factor with seam sealers are they need to stay slightly pliable but be rigid enough when cured that the paint over it will not crack.

The sealer that I am going to recommend for roof ditches it the industry standard 3M 8115 Panel Bond Adhesive.  This product is epoxy based so that it sticks to all types of materials and cannot be re-wet or softened by solvents when cured.  It also  has a corrosion protection characteristic  so that it can be used on either bare-metal or scuffed primed(2k) surfaces.

I would recommend sealing the channel with epoxy primer and letting dry a minimum of over night.  Scuff the fully cure primer with a red scotchbrite.  You can apply panel bond over bare metal, which is a great advantage, but the epoxy primer can get in to the small seams an help with corrosion protection,

Dispense the Panel Bond into the trough with the applicator gun then take a formed spreader or possibly your finger with a rubber glove on and spread the adhesive to create the concave shape that fills the channel.   you can clean up any squeeze out or mess with some solvent while the adhesive is still wet.   It has a slight self leveling feature which lets any trigger marks or bumps smooth out as it dries.

Let the Panel Bond Adhesive dry overnight.   It the trough does not look really nice or perfect in every area, you can shape and feather the adhesive with 80 grit sandpaper and finish with 180. Also you can scuff the adhesive up and tool out another coat if it still doesn't look right.   The fact that you can sand it lets you shape it to perfection.  Since it is an epoxy you can touch-up any pinholes or scratches with a two-part glaze.

Once it is the shape you want, scuff it and prepare it for the quality urethane primer you are using on the rest of the car.

The Panel Bond Adhesive will never shrink or crack and once you get the touch on how to spread it nice it will have a really nice looking drip rail that will be sealed from corrosion in the future.

Occasionally I see some people over-fill the channel and they loose the concave shape, while other times it may take two applications to get the right depth in a rough channel. The great thing is if you make a mess you can sand some away and reapply until it looks perfect.

The panel bond works on other seams of the car as well.The firewall lip originally had a seam sealer that cracked and replacing it with panel bond can look really nice.

I realize that often my tech articles are "Long Reads",  but I train technicians everyday I want to cover as much detail as possible so you can have the best results and no failures.

[RICH MUISE]

I'm sure glad I asked, that was awesome, Pat. Thanks a ton, exactly what I needed and wish I knew 6 or 7 years ago when I did the driprails. I'm sure there are a bunch of guys on this forum that will make good use of the info. I for one can confirm what you said could happen with the old style sealers in the cartriges as it did exactly that on my car.
Rich
PS. saw your dad at Lowes back a few weeks ago

[RICH MUISE]

Pat, a question I forgot to ask: How many of the 2 part "kits" am I going to need for the Custom's driprails? will one do it?

[jvo]

Okay, thank you, as I am about to embark on a journey of roof and drip rail work.  I am not fully understanding this.  Are you talking about removing the drip rails and using this adhesive to bond them back on again?  I haven't even examined my drip rails that closely yet.  Are they a separate piece from the roof skin, or is the roof skin formed with the drip rail already on the edge?  If that were the case, we wouldn't need sealer?  Just paint? 
I will be cutting my drip rails and my roof approximately 9 to 10 inches back from the windshield header, on the Fairlane 500 donor, and welding the Ranchero roof on at that point.  Will I need to totally remove my drip rails to do it properly?  I just did some drip rails on a 37 Chevy truck, and drilling out the spot welds on that was very difficult, as some were below the top edge of the drip rail, and made drilling very difficult.
Also, if I screw the drip rails up, are there any suppliers that you can buy replacements from? 
I am thankful for this information, as I was only going to clean them up to bare metal, then let some por15 run down the crack ( as its as thin as water) and hopefully it would run down between the metal surfaces.  I am not at home till tonight so I can't have a really good look at mine yet.  Appreciate this info though.

[RICH MUISE]

I'm 98% surethe rails are separate pieces and thus the need for the seam sealer. In any case the discussion we were having was not about removal and reattachment of the driprails, just using a better product to seal and form the concave trough. Just a note, JVO, some model Fairlanes I believe only had the driprails on the sides, not over the windshield. Do not know if that affects your project. I think KYBlueoval had some pics posted of that in his build thread because he was considering putting the larger Fairlane stainless around his Ranchero's windshield. I can't remember which models it was that don't have the front driprail, I'm thinking the Victoria Town Sedans.

[gasman826]

The spot welds under the seam sealer hold three layers of metal together.  The first is the door opening/side structure of the body.  The second layer is sandwiched and is the drip rail and inner structure that supports the head liner.  The third layer is the roof skin.  Since the spot welds are NOT water tight, some sort of sealer is required.  If the layers were glued together with panel adhesive, a seam sealer might not be required. 

When I skinned the Custom roof, the drip rails were shaved.  With all the spot welds drilled out, all panels were media blasted and refastened with panel adhesive.  No drip rails...no problem.  The Raunch Wagon on the other hand will keep its drip rails and this information will gives  me some peace of mind that this area will not be a area of potential rework.  Thanks!

[Ford Blue blood]

Pat your explanations are well assembled and edited!  Too often instructions have several "holes" in them because the writer "assumes" a certain level of knowledge and are too close to the subject.  Having written a couple courses of instruction while an instructor in the Navy a good QA check was to hand the course papers to another instructor from a different area and get his level of understanding.  Many times the "holes" are obvious after being pointed out.  Good job!

[lalessi1]

Pat your explanations are well assembled and edited!  Too often instructions have several "holes" in them because the writer "assumes" a certain level of knowledge and are too close to the subject.  Having written a couple courses of instruction while an instructor in the Navy a good QA check was to hand the course papers to another instructor from a different area and get his level of understanding.  Many times the "holes" are obvious after being pointed out.  Good job!

X2!

[hiball3985]

X2 I copy and paste this type of info to a text file and save it in my tech folder so I don't have to go back and try to find it in the future  .