Monday, August 18, 2014

Left Front Fender - Part 5

At our last exciting episode, the work on the fender continues including the fitting and welding in of the headlight support structure from the original donor fender.  The plug welds were mostly complete and needed just a little dressing up.   That pretty much finished up the metal work on the front of the fender.   Next up was the lower rear section of the fender.   

But before I go on, I have to admit to a little blogging dyslexia.  I realized that the past 4 posts on the fender topic were about the "Right Front Fender" when in fact, I've been working on the LEFT front fender.   I'm surprised all you Mustang manic people didn't notice!   I thought about going back and retitling my previous posts, but decided to leave them the way they are just to mess with everyone.  LOL.   Anyway...

After doing the plug welds on the front face of the fender, I realized that I didn't do the three welds that are on the top front inside edge.  It's no big deal but the welds are necessary.   It didn't take much to do them and clean them up.

This is before the welds with the fender and headlight support structure clamped together.
This is after welding and cleaning up.  Sorry for the fuzzy picture.

With this part complete for the time being, the lower rear corner was next up for repair.  One of the challenges to this repair was to match the contour of the inner and outer structure so that there were no noticeable  changes  in the fender skin after welding in the patch.  To help make sure the fit would be as close as possible, I used the right front fender as my guide.  I used the contour gauge to determine the shape of the inner structural member.  That meant putting the gauge between the inner support and the flange for the outer skin.

 After the contour gauge was properly fitted to the fender, I transferred the form to micro-corrugated board.  I now had a template I could use as a mirror for the left fender repair.

After cutting out the template, I made a trial fit.  I needed to do some trimming to get it as close as possible, but it came out nicely.  The "step" on the left side is the alignment point of the bottom edge of the outer skin for reference.  Now that it fit the right fender, all I needed to do is "flip" the template and I was all set for part fitting on the left fender.

One issue with the fender repair was the amount of "spring" in the fender--that is the tension that was released between the outer skin and the support once the bottom welds were cut and the pieces separated.  I needed to get the support structure back in position before welding.  Since the right fender was my guide, I needed to make sure the inner support and the outer skin were parallel to each other.   Using a scrap piece of square tubing and a C clamp remedied the problem.

Next came the fitting of the support structure.  Again, using the right fender and the template, I trimmed both the fender support and the replacement piece until I had a good fit.  This was quite involved since it's a 3 dimension fit--one to the support structure, one to gain the proper contour, and one to the proper length so when the outer skin was put on the bottom of the support wouldn't extend below the outer skin.  This step took longer than the photo or description depicts.  The closer I got the part to the final dimension, the slower and lesser material needed to be removed.  After a number of trim-n-fit sessions, it was ready for welding.

It looked good in the contour position.  But I also needed it to be in position for the outer skin alignment.   So good.

It was time to put a couple of tack welds in place and then check the position again...

I needed to tweak the contour and bend the replacement support to match the contour template.  The fit was as close as I could get it...

The final position check was to make sure the part was not only parallel, but the bottom edge was an 1/8" inside what would be the outer skin of the right fender.  Everything looked good.

Now it was time to start the painstaking task of welding this in position.  I stopped every half dozen spot welds to check that the position remained the same.  What helped was this part was heavier gauge than the outer skin.

With the spot welding near completion, I had a nice strong joint, although it wasn't the most beautiful weld job.  (Make a note Dennis: Next time you do another restoration, if you do, buy a TIG welder.)

The outside surface of the support looked good with plenty of weld penetration. Also note above in the lower right side of the photo that I tried Sven's method of using heavy copper wire to get a better ground on bare metal.  It did make a difference.  Check it out here.  I used a different gauge of 12" long wire, but I would say the results are similar providing a bigger contact patch for the ground.  

I turned the fender over to check the penetration on the inside that would be hidden by the outer skin patch.  I dressed up the weld joint and it looked good as well.

The next step was to trim the outer skin patch to fit the fender.  I didn't show it on the top horizontal joint, but I had slipped it underneath the outer skin and used a fine Sharpie to give me a starting point on trimming the horizontal edge.   This was a little tricky since I also needed to make sure the overlapping flange of the patch would align with that edge of the fender and at the same time, align the bottom edge with the skin and the structural support.  Again, there were multiple fit issues that were all interconnected and simultaneous as a lot of metal replacement tends to be.

After getting the top joint close, I did the vertical joint.  To define it, I again pushed it under the skin and then sprayed guide coat over the joint.  When I disassembled it, I had a clean line to cut along with my rotary cut-off tool.  

After that cut was made, it came down to judiciously trimming the edges until I had a little less than a 1/16" gap.  This had the advantage of being able to adjust the fit as well as give good weld penetration.  Here is the patch clamped in place and ready for welding. Note how nicely the edge and contour are.  :- ) 

The bottom alignment with the fender outer skin and the support were almost dead-on.  Another :- )

After the fitting of the outer skin patch and the welding of the inner support, I gave each part a cleaning and a coat of Zero-rust with a foam brush.  No need to be fancy here...

I put a fan on the parts and left them to dry while I ran an errand.  With the higher humidity, it took a couple of hours for them to adequately dry.  

Then the process of welding the patch into place started.  I needed to be extra careful to make sure that the joint of patch was "even" with the fender so that one side wasn't higher or lower creating a step in the weld joint.  It probably took 4 dozen welds at least to completely fill the joint.

This edge of the fender where the patch and fender skin met was critical.  Fortunate, the edges lined up and the weld didn't blow through the end of the fender.

After some more spot welding and gentle body hammer/dolly work, the almost finished product wasn't so bad.  I'll end up with a little filler, but not much.

I flipped the fender over and dressed up the back side of the welds on the outer skin.  Not to bad for a day's work,

I was pleased that the overlap pinch flange came out OK.  That was tricky with the plug weld and the end of the joint with the edge. 

I'll go back and give the fender another once-over and hopefully be done with the metal work on this beast.  I'm going to hold off any of the filler work until I get it mounted to the body. and start working all the panels together.

The next project is the RIGHT fender that I discovered had a couple of rust pin holes in it.  It's not where near as invasive as this fender was, but nonetheless, tracking down the elusive rust demon seems like a never ending story on a restoration.

Until the next time...