Saturday, August 12, 2017

How to replace the trunk drop-off panel using a butt-weld

It's easy! Just cut off the old panel and fit up the new one. Set the welder to 11 and go for it! No, not really. But it's fairly straightforward. There was plenty of evidence that there would be some rotten metal in this area from day one, so this was not a surprise to me at all.

Before the project began - this is inside the trunk looking into the passenger side trunk well.

I could better view of the trunk area once I cut out the quarter panel skin. I'd primed all this metal when I did the trunk, but I kinda figured I'd be in there again later on.

This is the trunk drop-off. It's actually part of the trunk floor panel on this side, but because it sits behind the wheel well and stuff tends to either accumulate in here or road salt eats it from the outside, the metal is subject to rot. Once it was fully exposed, I used a wire wheel on my grinder to see how much of the metal was bad. The outside, exposed to the elements was fine. But the interior-facing side shown here was pocked with rust and weak spots all over, especially at the edges where the new quarter needs to be welded on. So it has to be replaced.

I lined up the replacement panel on the old panel just to see how close it was to original specs and screwed it into the old panel, as some folks have suggested you line up panels that are going to be butt-welded. Because I'm considering a butt-weld for the quarter skin, this was a chance to try the technique. I scribed a line for my cut and clamped the ends to keep the thing stable while cutting.

Closeup of the cut-line.

I used a whiz wheel on a die grinder to cut through both pieces. I'm not convinced this was a better way to cut metal. If I were to do it again, I'd use a jigsaw.

Removing the panel exposes the open space behind the trunk crossmember. There are three spot welds back here to remove in order to get the trunk drop-off removed. This area gets nasty due to road grit getting kicked up here, thus the rust in between panels.

Cleaned up and ready for primer and welding.

The replacement is sold as a fit for 65-70 model year cars. But all that means is that everyone has to do some mods to make it fit their application. In my case for a 1967 car, the lower and rear edges are too long and there is an extra hole that will need to be filled or plugged. Also the forward drain hole isn't in place, so I'll have to add that. I won't trim it till the quarter is in place.

Lining up the new panel on the old. I used magnets and clamps, and kept the gap as tight as I could. In most places the gap was smaller than my weld wire diameter (0.030"). I've tried the little screw clamps everyone talks about and found that they leave too large a gap for my clumsy welding skills.

The backside of the trunk was stripped of primer as well - remember, 'surgically clean metal' is the rule here.

Many small tacks later, it's in. I only needed the copper spoon for a few of the tacks where my gap was too large. I tried planishing the welds as well. but the space it really tight, so that didn't work as well as I'd hoped.

Ground down the welds and scuffed the whole panel in prep for priming.

Admittedly, that does look better, and I like that the metal is fresh and solid. 

Here's the three plug welds on the crossmember that need to be redone. Clean, clamp, and burn.

Not the prettiest welds, but good penetration and no one will see these.

Two coats of SPI black epoxy primer were applied on both sides.

The gloss level is high since I had just sprayed this when I took the picture. It'll flatten out as the week goes on and look like the rest of the floor before long. But now we have new good metal for welding a new quarter panel skin onto.

On to the next step - installing the new outer wheel well.

Sunday, July 9, 2017

And...we're back! Cleaning up the edges and test fitting the rear wheelwell.

I got the garage back last week, so after a few months off I'm ready to get back at the Mustang again. I still don't know how to install a quarter panel, but it's time to keep plugging along anyway.

Now that the quarter panel is mostly gone, I can see and clean the mounting surfaces for the new quarter panel.

The leading edge of the panel covers the B-pillar. A light coating of surface rust covers everything. 

Just a wire wheel and some time cleans it up nicely. Don't grind here, there are factory reference points called Master Control Surfaces that you'll want to preserve to line up new panels. (I found that secret detail in the factory weld and sealant manual).

 This is the top of the rocker panel where the quarter panel was mounted. Again, surface rust and body caulk, but nothing serious. I'm pretty sure the rocker panels are galvanized, so they should hold up pretty well.

More wire-wheeling and it's clean enough for the next step. Notice where I got a little over-zealous with the spot-weld cutter - it left little circles and thinned the metal there. When I replace the panel, I'll need to place my new plug welds to the side so I don't blow through the thin meal.

The trunk drop-off panel on this side is in bad shape. After stripping it with the wire-wheel, I found a lot of weak and very thin meal over the entire bottom four inches as well as the edges. The top is fine. When I got the car from Brett, there was a lot of oily dirt and debris in here that had clearly been sitting for a long time. I'm not surprised, just disappointed :(  This will need to be replaced.

Now it's time to test fit my new outer wheelhouse. The inner wheelhouse is still in place. On coupes of this year, the inner brace is welded to the top of the outer wheelhouse, making replacement fairly easy. On fastbacks, the inner brace is welded to the wheelhouse assembly lip. so replacing the outer wheelhouse is more trouble.

My clever/lazy solution was to drill all the spot welds on the brace all the way through. When I slide the new outer wheelhouse in there, it'll fit it between the lip on the inner wheelhouse and the brace so it'll be easy to plug weld in. Of course, this means I'll have to weld both sides since the holes go all the way through, but whatever. That's future-me's problem.

The new wheelhouse fits in nicely. I had to clean up the inner wheelhouse mating surfaces pretty well, but now the new part just slides in there and is held in place with the tension from the inner brace on top.

Rear view - here you can see the fit at the trunk drop-off.

Front view. 

More to come. Next up is more metal cutting and replacement!

Friday, March 17, 2017

Quarter Panel Repairs - patching the rusty inner wheel well

Here's a quick and dirty post on a patch job in the wheel well area. 

When the outer wheel well was cut out, I discovered a weak and rotten area of metal that is a common place to find rust. The inner and outer wheel well pieces are overlapped a little bit at the forward part of the assembly inside the well. The overlapped area tends to trap dirt and water being run around in there and eventually rust forms. I figured this was worth posting since it's probably happening on a lot of these cars by this point. The rest of the metal around here is in pretty good shape, so it could have been worse.

Once the outer wheel well was gone, the rot is exposed. This shot shows the intersection of the inner well, the floor pan, and the rocker panel. 

The bad metal is cut out easy enough.

Here's more rotten metal in the pile. It's about 3 inches by 4, and is completely eaten through very thin in several places, so I'm happy to have it out.

 The area is cleaned up in preparation for welding. Those two holes in the upper flange of the rocker panel aren't supposed to be there - that was a result of overenthusiastically drilling out a couple of spot welds that were holding the outer wheel well in place. I'll need to fill those holes before I put the new wheel well in.

 New patch made from 20 gauge metal. 

 The patch was butt-welded in and plug welded where the original spot-welds were before.

Welds cleaned up and it's good as new. It's much smoother than it looks, and I'm pretty happy with it. I'll trim the bottom and outer edge to the right shape later.  But you'll never see all this once the quarter panel work is done, as this will be covered with the new outer well and then covered with new sound deadener.  

Now I just have to patch a couple other holes here...

Sunday, March 12, 2017

Quarter Panel repairs- cutting out the bad metal

I've been thinking/agonizing over this next step quite a while. I know some of metal is bad on the quarter, but it's mostly on a lot of curved surfaces like the wheel well arch and near the decorative vents. Curved sheet metal is harder to weld than flatter areas, and welds in the middle of broad swaths of metal are more likely to have distortion and warping issues than welds near panel edges. So, the amount of metal I cut out will have to be balanced against my admittedly beginner's welding skills.

When doing a job like this, you have a couple options: you can get a full replacement quarter panel, a reproduction of what Ford used to build the car 50 years ago, or you can get a "skin".

The quarter panel forms the trunk opening as well as the door opening and goes all the way up to to the roof line where it's leaded to the roof panel. That would be a lot of metal just thrown away to fix a hole in the wheel arch. And they're pretty expensive. But the edges are well-formed and it's the most accurate replacement part. Replacing this panel is a massive job, but requires less welding.

The skins are meant to just be used as patches, not full panel replacements. As such, they are much cheaper than a full quarter panel, but the edges of the skins are not well formed and not useful for actually installing on the car. This panel would be chopped up to fit and then butt-welded around most of its perimeter. If I were a better welder, I'd be using a skin and cutting a smaller piece out of the car.

After a long time thinking about this, I decided to cut out the majority of the quarter panel's vertical skin from door to tail and as high up to the body line as possible, and use a portion of a real quarter panel as replacement metal. This way I preserve as much factory metal as I can, and get to use good edges on the front, bottom, and rear for plug welding to the car. This will leave me, however, with a five-foot-long weld at the top of the panel that will have to be done so as not to cause a lot of distortion or need gallons of body filler to hide after the fact.

For replacement metal, I could buy a full quarter panel for a fastback, but as it happens the quarter panel for the coupe is basically the same piece up to the body line, but a lot cheaper. So I got full quarter panel for a '67 coupe and use it to create a sort of skin panel that has good edges that can fitted right on the car. I will trim off the coupe-specific metal at the top of the panel so I can fit it onto the remaining panel on the fastback.

New coupe quarter panel taking up space in the garage.

It has all the edges and details right, unlike a skin panel. 

The new quarter has an piece that ties the panel to the tail panel, but I'm keeping mine, so I cut this off the new part. Just a few spot welds hold it in place.

Cutting off the coupe-specific metal from the top of the quarter panel so it'll fit up on a fastback car.

Marking the first major cut. I made several to make sure I was cutting only what I wanted. 

Yeah, I just cut a huge hole in classic car. 

Here's the backside of the part I cut out. The rot is clearly visible here, and the entire wheel lip is toast, as well as the metal in front of the wheel well (at left in this pic). Cutting it out was the right move, but now I have to do something about it.

There's more to this part than just cut out the old and weld in the new. The next few posts will show a bunch of the 'other stuff' that's required along the way.

Sunday, February 26, 2017

How to assess rust damage on a quarter panel

No posts in a while, I know. I've been busy with a few non-Mustang projects lately, and this next fix is a biggie - so instead of doing it all in one post, I'll have to break it into a few. Hopefully, this means more frequent posts as well.

I could just as easily call this post "How to face your demons", as I've been dreading this work since I bought the car. Yep, that's right, I knew this car had visible rust on the body and I bought it anyway. I like to think that speaks to my optimism and ruthless persistence -but it could just as easily be a prime example of bad decision making. Either way, I'm about to find out.

Let me orient the reader for this topic. The quarter panel, above, is the expanse of metal that forms the back of the car from the tail panel to the door latch panel. It includes the decorative vent mountings, and forms the edges of the trunk, door, and wheel arch. On the fastbacks, it goes all the way up to the roof line and includes the 'sail' with the fresh air vent. It's huge.

The right side quarter panel had a little hole at the top of the wheel arch, and the half-inch hole went all the way through - not quite big enough to put a finger through. What may not be immediately obvious is that there's actually two pieces of metal here - the quarter panel and the (outer) wheelhouse. The wheelhouse is the big curved dome that the wheel rides in and keeps water and mud out of the car. The quarter panel is spot welded to the wheelhouse where the outer edges meet at the wheel opening.

So, as the title suggests, I'm going to show what I was looking at to figure out how bad the rust really is. I'm trying to avoid cutting more metal off the car than is required to make a good repair*. The quarter panel has lots of curved surfaces and those where the rust and curves are will actually dictate how I decide to patch this part.

*A more experienced person wouldn't have to do this. I'll remind you again I'm not that person.

The easiest area to look for damage is back in the trunk behind the wheel. In this shot, the back of the wheelwell is at the left, and the outer skin of the car is at top. When I went looking, I found nasty looking metal, but it passed the "stab it with something sharp" test, at least where I could reach. But the metal looks like it could be weak and pitted at the edges. Ick.

Next up, I can look behind the interior trim panels and see what the quarter skin looks like at the forward section. Here's the passenger side rear interior trim panel before I took it out (many moons ago...)

I found a monster of a mouse nest behind the trim panel. This is bad, as all this material would be really likely to hold moisture and cause rust from inside the car...

...which is exactly what seems to have happened here. The skin of the quarter is rusted at the wheel well and the rocker panel junctions. So that's a bummer.

When subjected to stabbing test, I found one actual hole an some weak metal that deformed quite a bit. Another bummer.

I then picked out and broke off all the rust nuggets I could by hand, and then hit the outside of the wheel arch with a stripping disc to see what would come off. That half-inch hole became a a 6" x 3" gash through the quarter skin an the outer wheel house. Yikes. Well, just remember, if you can see the rust, it's usually a lot worse under the surface.

Now let's look inside the wheel well. Sticking my head where the wheel usually goes and looking aft, I see outer wheel house is soaked in something oily and has rust at the bottom where it meets the trunk drop-off and the quarter panel. It takes a lot of light and some scraping, but it's there nonetheless.

Looking up at the top of the wheel opening (see the hole?) there is a rust stain that runs the entire length of the outer wheel house from front to back. That's likely a serious bummer as well, as it means that most of the outer wheel house is rusted and will need replacing as well as some part of the quarter panel.

Looking closely at the hole in the top of the wheel arch, the rust seems to extend a good inch up from the edge of the hole in at least two directions.

I decided to cut half of the outer wheelhouse away from the car so I could actually see the extent of the rust on the inside of the quarter panel. After drilling all the spot welds holding the quarter panel to the outer wheelhouse, I marked my line with tape and cut it out. There are also a couple spot welds at the wheelhouse/rocker panel junction.

Stupid sideways pics.

Here's a view from inside the trunk looking forward once the wheelhouse portion was cut out. What's left is just the quarter panel. Notice here the wheel lip on the quarter panel is rusty. It looks worse in person.

Here's one of the pieces of the wheelhouse I cut out. The edge that was connected to the quarter panel is totally shot - it's weak and perforated. Remember, all I could see before I cut this out was the stain in the wheel opening. This is the opposite side of that same piece of metal.

The other part of the wheelhouse was in just as bad a shape. No point in trying to weld to this mess.

Oh, and a bonus - another mouse nest, this time inside the rocker panel. I was going to clean this space out anyways, but now I have to do it while wearing a respirator.

Looking from the inside, the rest of the lip on the quarter panel is just as bad. Again, no point in welding on that mess.

Here's a great view of the rust that is on the quarter skin from the big mouse nest. That metal is weaker than it looks. It has to be replaced as well.

Remember the original half-inch rust hole that we started with? Look how bad it looks from the backside. "You're going to need a bigger patch."

So now that I know where all the rust and weak metal areas are, I marked them all out all the on the front of the panel to assess how much metal had to be replaced.

So, I have a good idea of what's bad and needs to be replaced. And I have a replacement part ready to go. That's actually a replacement panel for a coupe, not a fastback, and that's on purpose.

Stay tuned for the next step - cutting.