Thursday, April 17, 2014

Smoothing Up the Right Rear Quarter

As I mentioned in earlier posts, the right rear quarter panel on my car was the most in need of metal work and filling as any other panel on the car.  However, knowing this going in, and coupled with a good plan of action, this heavily iterative and time consuming project went quite smoothly and the results reflect the effort.

As outlined in my post covering this process on the left quarter, I start by sparingly applying the “heavy” filler in all of the areas that have welded seams or require more robust filler as the base to build on.  I use a product called All-Metal for these areas as it is as close to a metal (more specifically body solder) behavior as any polyester filler available.  It has excellent sealing characteristics over clean welds and although it is rather demanding to sand, it can be feathered and smoothed rather well and provides an excellent base for the primary filler I use.
Once the All-Metal is sanded to shape, the process of applying thin coats of Rage Gold body filler begins.  Generally speaking, the first base coat of filler I apply is the heaviest and every subsequent application gets thinner and thinner and over smaller areas until the panel is straight.  There is simply no possible way (other than pure luck) that the filling and smoothing process on a show-worth body will be achieved in a single pass.

After each layer of filler is applied, I knock down the ridges and rough shape the surface with a Surform tool.  One thing I take the time to do is smooth up the fender lips such that they are much more presentable than the often nasty surfaces presented by the factory work.  This also helps create nice, clean wheel opening lines that really look sharp when done.

I will often use my DA sander with 80-grit paper to shape the first layer or two of filler as this is often just a way to establish a base to work from and not the final finished surface that will be established by hand.  This also provides a very nice platform to apply powdered guide coat and block the panel by hand just to see the first indications of how and where I will need to work the most.  From this point on, every successive pass with filling and blocking will be done with guide coat and a very careful application of DA and hand sanding until the final shape is almost complete.  At that point, absolutely ALL of the final blocking is done by hand and with many coats of guide coat to indicate progress and panel accuracy.

Because I had a lot of area to cover that would need various levels of work, I split the quarter into 3 work sections and tackled one section at a time.  I started at the rear where the highest concentration of welded repairs were required and smoothed up the entire rear half of the quarter in the first phase.  Then, with that zone completed, I moved to the front half of the quarter and repeated the repair process until the results were as perfect as I could make them. 

This was an area that was particularly complicated in that the amount of filling that was required was very thin but in many spots that simply were impossible to detect with the naked eye or even by hand.  This is where the religious and generous use of guide coat is the only way to get this type of area straight and actually saves tremendous amounts of time in the process as well.

The final zone was the “top” of the quarter and involved essentially two areas of interest:  the trunk corner seam and the roof seam at the sail panel.  These are rather curvy locations that require very careful and slow sanding to get the contours perfected.  The roof seam area also represents the heaviest filler application anywhere on the car due to the recessed seam area once filled with factory applied body solder.  However, the technique is pretty much the same here as it is anywhere else, and the generous use of guide coat will pay huge dividends along the way.  In my opinion, this sail panel area is one of the sexiest areas of the 69-70 Mustang body with the long, deep curves running almost the full length of the quarter.  That’s hot!

So, now that the right quarter is smoothed up, the next steps will be to prep the panel and quarter end caps for masking and then shoot the works in a coat of trusty PPG DP40LF epoxy primer.  Once that is done, we’re off to the next panel!

First bit of filler than I apply is All-Metal and is used to seal any welded patch area or any area that required welded pins to pull damage.  This filler is very hard and works more like body solder than Rage Gold so I use it sparingly to provide a base to work from.

Shaped & sanded with 80 grit paper to rough out the shape and we are ready to apply standard body filler for the rest of the job.

Here, you can get an idea how thin the All-Metal filler is when dressed down.  Maximum thickness in any spot is only on the order of .050".

Both the rocker panel welded seam and the area where the crease was removed get a thin coating of All-Metal.  These areas have been sanded and are now ready for a very thin skim of Rage Gold to finish.

A thin skim of All-Metal filler is applied to the seam welded joint at the base of the rear windshield and sanded smooth with 80-grit.

The first coat of Rage Gold is rather heavy with the understanding and intent of seeing most of it deposited on the floor as dust, leaving behind a very solid foundation for subsequent filler application.

I regularly employ Surform tools to shave the filler to rough shape just after the filler kicks to the heavy gel phase.  This is a bit like hard cheese and shaves very easily with these tools.

In the early filling stages, I rough out the initial shape with 80 grit paper on my DA sander and then finish the job by hand with various sanding blocks.

I absolutely LOVE dry powder guide coat!  Not a single layer of filler avoids a generous application of guide coat to allow me to easily see the shape and accuracy of the panels before, during and after sanding.  While the camera flash makes the guide coat look very light, in practice, these filler areas are stained quite dark and provide huge contrast when sanding.

Finishing body filler by hand is the only way to get things dead flat.  In this shot, I am sanding in an "X" pattern, starting at the top right of the panel and moving down to the bottom left and then reversing the direction, beginning in the top left and ending at the bottom right.

Having started at the back of the panel, I finished the rear half first, before moving to the front of the panel.  This shot shows several iterative layers of filler were needed to get the shape I wanted in the early stages.

The bulk of filling work at the rear of the quarter has been completed in this shot.

The final bit of work on the rear of the panel was fitting the panel contours to the die cast fender end cap.  The fit of these panels can be all over the map and this one required a bit of extra work to get the contour just right.  The green masking tape prevents body filler from sticking to the end cap while I apply it to the quarter.

Once the filler reaches the gel phase, I use a razor knife to cut the filler along the thin gap between the quarter edge and the end cap to create a straight line that is much easier to finish.  Once this bit is fully cured, We sand the filler to the proper contour and get ready to tackle the front and top of the quarter.

Like the rear of the quarter, the front is prepared in the same iterative way as all of the other filler work I have shown.  Thin applications of filler and careful sanding with guide coat allow the panel to flatten out very nicely.

And there we are!  The front and back half of the right rear quarter are complete.  All that remains is the roof seam at the top of the sail panel and the rear trunk corner.

With the first application of filler on the sail panel, I start by shaving the contour to the rough shape I want using a Surform tool and sand to shape with 80-grit paper in the DA sander.  This first coat is just a bulk-filling application as this joint between the roof panel and quarter is quite deep by design and requires a good bit more filler than most any other place on the body.  Recall in an earlier post that this seam had already been filled with All-Metal to seal the weld seam and fill the body solder trough.

The second application of filler to the sail panel is much thinner than the first.  We are getting very close to the final surface.

Shaved with the Surform tool and ready to be carefully sanded to final shape.

About 4 passes with Rage Gold filler were required to get the sail panel joint perfected.


  1. Nice progress, Sven! As usual, I'm jealous of your body-working skills Your posts have been good tutorials on the process though. Thanks!

    1. Thanks Alex! I'm glad there is something there of instructional value (and maybe a little entertainment thrown in!).

  2. Great work Sven. I know that the blocking is going to be slow, but looking forward to seeing more!

    1. Grant, I gotta say that blocking MUST be combined with good 'ol Rock & Roll on the radio or it just ain't happening! LOL! More to come for sure!

    2. I agree with you there, I can't do anything on the car without my Ipod!

  3. Yes, the dog days of filling and sanding - but a great instructional process. Thanks Sven. It's really starting to shape up!!!

    1. Getting excited to start fitting individual panels very soon! Deck lid and rear valence will be next!

  4. OK. Now you've gone and done it...motivated me to get my butt back on my fastback. And how appropriate that it will be the same right rear quarter panel. After I get back from visiting my kids in west Iowa, I'm blocking out time to block out that quarter. Oh...excellent work usual.

    1. That's my job Dennis! To contribute to your extracurricular motivation to get into the "other" sanctuary and bond with your Mustang!