Friday, May 10, 2013

Replacing the Roof Skin – Part 4 & DONE!

Another solid week of progress is in the books and I am happy to report the new roof skin installation is complete!  With the interior surfaces primed and dry, work shifted immediately to the top side work.  The goal in this phase of the build is not to apply finish body filler, but to seal and generally level the roof seams and remove the EDP coating on the panel in preparation for a solid foundation of DP40LF epoxy primer.
We began with filling the formerly leaded roof seams with All-Metal repair compound from US Chemical.  All-Metal is a heavy-bodied, metalized polyester filler that is excellent for replacing lead in such applications.  Unlike lead, the surfaces prepared for All-Metal require no tinning or acidic preparations to condition the surfaces for filling.  Instead, standard body filler preparations (e.g., grinding to clean, bare metal with 80-grit abrasives and solvent cleaning) are all that is required to ensure a secure and waterproof bond to the parent metal and there are no concerns downstream of incompatibility with the finishing and paint system products to come.  Application is exactly like any standard body filler and All-Metal can be shaved with Surform (a.k.a. cheese grater) tools in the same way you would standard body filler as well.  However, once it sets, All-Metal is a pain to sand and loads up sandpaper like a beast.  That is a major reason that I use it as a bulk filler on seams, etc., and follow it up with Rage Gold for all finish work.
With the leaded seams filled to just below surface level, the process of removing the EDP coating from the roof skin was begun.  This was mostly accomplished with the DA sander and amounts to slow tedious work.  In the end, we ended up finishing the last half of the job with aircraft paint stripper sparingly applied and simply used a straight edge razor blade to peel the DP off in long ribbons.  Probably cut the process time by 75%.  When Ted saw me do this……..he was NOT impressed!  I told him he needed the DA practice.  Haven’t seen him in a week……(kidding).
With all of the EDP removed, the entire bare metal surface was sanded with 80-grit to provide proper “tooth” for the primer and the entire surface was then blow off with shop air and generously swabbed with wax and grease remover.  Then a thorough wipe down with a fresh tack rag, followed by a final cleaning with wax and grease remover and the roof skin was ready for primer.
After mixing up a fresh batch of PPG DP40LF epoxy primer in my 3oz touch-up gun, I started by cutting in the A-pillars, window flanges  and drip rail channels to ensure they were coated well and completely.  This also makes shooting the flatter surfaces much easier as you don’t have to worry about getting enough primer on any of these oddball surfaces at the same time you’re trying to cover the larger areas.
I applied two solid coats to the cut-in areas and let each coat flash off for a solid 20 minutes to avoid any issues with solvent pop, etc.  Then I switched over to the flat areas of the roof and applied two coats of DP to those surfaces as well, making sure to blend over into the cut-in flange areas well to avoid any separation lines in the final coat.  I tried to apply each coat slowly and deliberately to ensure it covered well and lay flat and smooth.  I admit to taking a few opportunities to tinker with air cap settings at the same time and was quite satisfied with the final coat as a result.
With that, the roof skin replacement is now complete and the next phase of work will once again take an interesting turn.  I am happy to say the entire tub is now rust free and solid in every way and the work on the horizon will soon transition to more construction than re-construction.  Next up is lining the bottom of the car with U-POL Raptor Liner and then into the engine bay for a lot of clean-up and smoothing work.  Should be fun!

All-Metal is used to fill the formerly lead-filled seams at each corner of the roof.  It is leveled to just below the surface contour to allow final finishing with Rage Gold.

Front A-pillar filled with All-Metal

Ted getting started on the removal of the EDP coating using the DA.

The sanding process proved to be painfully slow.  Soon after I shot this picture, I switched over to aircraft stripper and a razor blade and the process started flying.

After all of the EDP was removed, we swabbed everything down with wax and grease remover.

After tacking off and cleaning a second time with wax and grease remover, the new roof was ready for primer.

I started priming all of the window opening flanges and drip rail channels to ensure full coverage.

Cutting in the complex areas of the roof makes spraying the larger, flat surfaces much easier since you don't have to worry about missing spots in the more intricate areas.

Another shot of the rear window flange corner after cutting in with primer.

With the second coat still tacky, the new roof looks awesome!

After 24 hours of dry time, the new roof skin looks better than new and I am able to take in the full measure of satisfaction knowing that replacing the roof skin was absolutely the right thing to do.


  1. You da man, Sven! (Ted too for all his labors) That roof turned out perfectly! That All Metal is great stuff. I'm going to use a similar produce (Metal-to-Metal) on the exterior floors and firewall to seal and smooth things out before the Rage goes on. Excellent, excellent, excellent!!!

    1. Thanks Dennis! You will be very happy with Metal-to-Metal filler as well. It behave almost identically to All-Metal. Good stuff!

  2. That's a good finish for a good repair. It should be a help to me as I am now convinced that I will have to do my own roof at some point. Great work as always Sven.

    1. Much appreciated Grant! I agonized over replacing the roof skin for a LONG time and now that it's done, I am glad I decided to pull the trigger. If you decide to go down that road, I sure hope some of the stuff on the blog makes the job easier (and maybe the decision too!).

  3. Solid work Sven! Looking forward to the move towards the mechanical end of things!


    1. Thanks RJ and me TOO! We have lots of work to do in and around the engine bay, so it will be a mix of just about everything pretty shortly. I'm looking forward to the switch.