DarrylD's Porsche 912 Project Page - Phase 3: Left Longitudinal Channel Repair

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Entry: 2/19/06 - Repair strategy time... over the last couple days I've been pondering how best to attack the rockerpanels, longitudinal channels and floor replacement tasks. My first idea was to replace the rear floor first because I need to see the mating point of the floor and rear longitudinal flanges since they are currently rusted away and the new floor pressing would provide that measurement. Well, I've thought things through and now I think the floor replacement should be the last step. I think I need to concentrate on one side at a time and complete the rockerpanel plus their inner wall's extensions forward and back which form the longitudinal channels. The whole inner wall needs replacement to remove the severe rot under the rear torsion bar tube, so doing it in phases isn't possible. Since the drivers-side of the car is easily accessible on the 4-post lift, I decided that will be the side I start with. I also decided it would be best to cut away the entire lower section from wheelwell to wheelwell at once, leaving only the interior panel of the longitudinal section that provides the flanges to spotweld the new floor and rockerpanel sheetmetal pressings to. In order to do this without the longitudinal channel sagging, I needed to make a sturdy brace to hold the door opening in place. I fabricated brackets by using 1/8" angle iron stock, cut to size and welded together to form a "T" cross-section and then sized to utilize the upper door hinge and the door latch mounting bolts. Between these brackets is bolted a nice thick-walled piece of 1" metal electrical conduit with the ends crushed in my shop press and drilled precisely to size for zero slop. I think you could lift the car from that conduit bar!

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I also thought I had better make a wooden template of how the rockerpanel currently fits to insure the lower door gap can be maintained as closely as possible. I am planning to replace the rust-bubbling sheetmetal across the bottom of both doors so this gap can be "fixed" but I thought having a template would save time as I'm fitting the new sheetmetal rockerpanel pressings. Since the interior panel of the longitudinal channel will remain, I cut a 2x4, notched for the weatherstrip lip to lay along it. I used some aluminum foil and three good-sized blobs of BONDO (finally a good use for real "BONDO" brand filler!) and layed the 2x4 on top of it so it made a perfect "casting" of the inner panel surface. Once that was dry, I measured and cut the 1/16" plywood profile pieces at the front and back end of the door opening. The plywood pieces are glued into shallow channels cut across the 2x4 so they will remain secure... as long as I don't drop the fragile thing!

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I also wanted to remove the rear spring plate to get better access to the repair of the rotted longitudinal channel below it. Before doing so, I thought it would be a big re-installation time-saver to make a plywood gauge of the un-loaded angle of the spring plate, once it was unbolted from the rear "banana" arm. The torsion bar came out easily but from the center splined mount first and it seems to be rusted tight on the spring plate's splines. Normally, That would be a really bad thing because I would have to withdraw the torsion bar through that little access hole! No worries, I'm almost ready to cut the rear quarter panel section out (dashed black lines) and I can remove both the torsion bar and the spring plate as one piece and put it in my bench vise to hammer the spring plate off! I decided to leave the "banana" arm, rear hub and rear shock in place so I can reinstall the spring plate without the torsion bar and keep the car a "roller" so I can move the car and use the 4-post lift for my other cars. The rear corner will sag (perhaps I can make a wood block to hold it up?) like it would if the torsion bar broke, but it will still roll!

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Entry: 2/20/06 - Here she sits with the left outer rocker panel and rear quarter panel cut out, heck, the smoke hasn't even cleared yet! My cut across the rear quarter panel was straight but not quite horizontal... once the blade started cutting, my focus was on clean and straight and I didn't worry much about keeping it on the dotted line but rather how the weld would look when I put it back together. I also laid out all the new sheetmetal pressings that will be going into the repair. Some sheetmetal at the base of the door hinge pillar will be reclaimed from the donor clip to make that area solid again.

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Here's a reference picture I took of the donor clip's rocker panel showing how the various sheetmetal panels are spotwelded along the flanges. The interior longitudinal panel is the only original panel that will be left in my 912, all the other ones are new pressings. You can see from this picture that the door hinge pillar is in very good shape on the donor clip but the nose of the clip was rusted almost beyond use... go figure!

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Entry: 2/21/06 - After staring at that rear longitudinal channel for the last couple days and poking around inside of it, I realized a simple patch to the bottom edge wouldn't do the job because I need to cut away enough of the steel to replace the heater tube inside the channel. There are a lot of compound curves in the pressing and it would be very difficult to fabricate to match the original appearance. Instead of spending weeks trying to make the patch panels for both sides, I bit the bullet and ordered the complete replacement pressing kit (in the picture below) for both sides from Stoddard's website. I'll probably trim a good bit of the replacement pressing's steel away to graft in only what's necessary to fix the rot and access the heater tube, but bottom line is the car will be like new when I get done by taking this approach to the repair. While I was ordering from Stoddard's, I added new inner and outer rubber spring plate bushings to the order to replace the worn ones I noticed yesterday.

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Today's most time consuming task was to break out the "Sawz-all" and cut the remaining pieces I need off the donor clip and get it out of the shop to free-up space for work on the left side of the car. You can see the "chunks" of front ends of the rocker panels and door check strap brackets liberated from the clip. I also removed all the bolts, wiring harness, fuel lines, etc. from the donor clip, just to have the spares on hand. You'll also notice in the following picture, I used my favorite purple "SuperClean" biodegradable degreaser and scrubbed the left rear wheelwell with scalding hot water, it is amazing the original undercoat still has a shine to it!

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Once I got the wheelwell cleaned-up and dried out a bit, more rust prospecting was the last task of the day. As you can see in the following photo, all the undercoating has been scraped from the back side of the lockpost using a heat gun and wood chisel. I'm happy to see there are only a few deeply pitted areas and the majority of the steel is sound. I have replacement lockpost pressings for both sides but plan to only use the bottom 5 inches or so to preserve the unique early engine lid release handle recess. I will do a little spot sandblasting on those deeply pitted parts and weld in a patch if necessary. Even with being able to stand and work on the inside of the wheelwell with the lift, tonight will be a two pints of Guiness and three ibuprophen night as my neck and shoulders are killing me from twisting to get up into that lockpost. However I'll sleep great knowing that there's no place for rot to hide up there now!

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Entry: 2/22/06 - Most of today was spent visiting my buddy Jack Morris at his shop, Wolfsburg Motorwerks down in Ballard, to show him how the 912 is coming along and discuss how he handles replacement of the rusted-out heater tubes that run inside the longitudinal channels. His approach is to use flexible marine exhaust tubing, which is galvanized steel, and welding it into place so it cannot rattle. I'll start checking out the local marine supply houses to see what I can find. When I did get back to work this afternoon, my objective was liberating a usable patch panel for the rotted left lower front wheelwell and lower door hinge pillar. Cutting these pieces out of the clip is just plain nasty work involving lots of cutting and grinding to get to the pieces, removing spotwelds and then removing the undercoating with a torch and wood chisel before media-blasting them. As you can see in the following picture, The patch for the wheelwell is great and lines-up perfectly with the flange on the front of the inner longitudinal panel for an easy graft and it only needs to have a 3/4" hole filled before it is usable. The door hinge pillar on the otherhand was so rust pitted that after media-blasting is a piece of lace which will serve as little more than a pattern for one I'll have to fabricate from scratch. Considering this piece is about 80% hidden inside the rockerpanel, the objective will be strength over beauty. Fixing the front section of the left longitudinal channel should keep me plenty busy until the additional sheetmetal panels for under the rear torsion bar arrive from Stoddards.

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Entry: 2/23/06 - Today the inner rockerpanel from the front wheelwell to the jack post came under the knife. The inner longitudinal panel's flanges are the points I would like to perform my grafting welds at to join the "used" replacement panel I cut out of the front clip yesterday. I inspected for rust depth with my spot sandblaster and found the floor flange in the forward part of the interior longitudinal panel to be very solid with only surface rust. Rot will require some floor flange fabrication in the flange at the rear footwell area as it gets closer to the torsionbar tube which will be a relatively easy piece to make. A brace under the outer seat rail is almost completely rotted away but this is an easy sheetmetal brake job to fabricate. I'm in a holding pattern to proceed with any cutting on the rear of the longitudinal panel until I see the replacement pressing on order from Stoddards. I cut the drivers-side floor out all the way to the pedal cluster and then removed the pedal cluster to inspect the sheetmetal under it. Amazingly, the sheetmetal up in the front of the floor is rock solid so the graft into the new floor sheetmetal pressing should be a matter of fitting and welding with no new fabrication for rust repair.

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Entry: 2/24/06 - Today it was time to clean-up the flanges for the floor and rockerpanels mating points to the interior longitudinal panel. Cutting out the old sheetmetal that was spotwelded to the interior longitudinal panel is slow going; grinding the spotwelds and hammering the seam apart with a panel separating knife like opening a can of sardines. I was able to get the spotweld flange under the door threshold weather strip channel and where the floor meets the panel cleaned-up and ready to use without damaging the original flanges. Once that task was done, I took the wire brush on my drill to the surface rust on the heat tube and inside surface of the interior longitudinal panel to prep it for a couple brushed-on coats of SEM Rust Seal. Since the rust accumulated on these hidden bare metal surfaces was the effect of 40+ years of exposure to the moist Pacific NW air, I figured a couple good coats of Rust Seal would be all that was necessary to preserve them. As you can see in the following photo, the result of the Rust Seal is a nice uniform black finish that can be left as it is. The floor mating flanges have some rust pits but the steel is very strong and should form a very strong seam using the MIG welder to tack them to the new floor sheetmetal. I will be needing to fabricate new flanges at the rear most 6" of the rear passenger footwell area and a new brace for under the seat rail mount before installing the new rockerpanel sheetmetal.

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Entry: 2/25/06 - Today the patch panel I liberated from the donor front clip was trimmed to fit and welded into position at the front of the left longitudinal channel. I still need to do some minor fitting and rot patching on the seam at the bottom of the fender attachment lip but it is very close to welding too. Next I need to "sculpt" the bottom of the door hinge pillar using pieces and a pattern developed from the donor part from the clip which was "lace" after media blasting. Luckily almost all the sections that can be seen from the outside are solid enough to reclaim. The hidden sections will be a primitive "rendering" I'll "sculpt" myself out of 20-gauge steel sheet stock using the original as a pattern. Tonight the patch sits with a coat of 3M Weld-Thru primer showing welds needing just a bit more dressing. I was able to reach the entire seam from the inside so I "caulked" it with a strip of 3M Ultrapro Autobody Sealant. I vise-gripped the replacement rockerpanel pressing into position to determine how well the rocker / fender attachment flange mated-up, LOOKING GOOD!

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Entry: 2/27/06 - Today's task was fitting and finishing the weld on the fender attachment lip and weld the top patch panel seam between it and the door opening on the back side. I made a pattern showing how the bolt holes on the fender were spaced and found the bottom hole on the fender retaining lip was about 3/32" too low, which would have made the rockerpanel that much too low. Fixing it required cutting some material out of the yet-unwelded seam cut and lifting it with a jack to bend and form it into position. There was also a small amount of rot on the part of the original fender retaining lip just above the patch seam that needed a " x 1" patch grafted in. After dressing the welds with my grinder, I chemically stripped the paint off the majority of the door hinge pillar and then filled the grind marks with JB Kwik Weld epoxy, which still needs to be sanded-down. I like to use JB Kwik Weld to fill small areas that might be subject to damage from rocks or road hazards as it is flexible and will bend instead of crack like autobody filler will. Now I need to fabricate a patch panel (outlined in red in the following photo) to fill in the area under the A-pillar base. The following photo shows the gap between the patch panel and the new inner rockerpanel pressing, the floor panel pinch weld flanges lines-up pretty well already. The patch will include the missing pinch weld flange and fill the gap. I would have probably finished that patch panel today but my MIG welder's 75% argon/25% CO2 gas cylinder ran out so I had to stop and run off to the welding supply shop to get a refill about mid-day which cost me a couple hours.

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Entry: 2/28/06 - WOW! WHAT A WAY TO END FEBRUARY! The day started-out by making a paper pattern of the patch panel for under the A-pillar. A few hours later, a beautiful sight, a patch panel all snipped and flanged into a perfect fit and ready to weld in:

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The panel was a snap to MIG weld into position and after grinding and dressing the weld, a thin coat of JB Kwik Weld over the grind marks and to fill blasted rust pits and it's ready for sanding. The seam between the bottom of my homemade patch panel and the "store bought" inner rocker panel pressing is all that remains to be fitted and welded. I'm waiting to decide how best to graft it with a strange recess in the manufactured pressing at that point. Anyway the following photo shows inner rockerpanel pressing clamped in place for a test fitting:

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It was like my birthday, my order of shift bushings and new speedometer cable to install in the center tunnel while its floor is cut out came from Pelican Parts. But better still, the rear longitudinal sheetmetal pressings came from Stoddards today as well! The Stoddards order also included a set of new rubber bushings for the rear torsion bar spring plates. As you can see in the following photograph, the replacement pressing has quite a few stress wrinkles from the stamping process. I am pretty sure I can get by with using about 30% of the total replacement panel and most of that area is wrinkle-free. I'm really starting to feel like I'm getting some traction on this project and that I'll be out of this dirty "coal miner" rust repair phase before nice weather gets here! I look back over the last 2 months work and can really see I've made an impact but I try not to think about all the work ahead too much... UGH!

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Entry: 3/1/06 - Today it was time to patch up the nearly unusable bottom portion of the A-pillar pressing liberated from the donor 912. The piece was in marginally better condition than the one on the car so I blasted it and found most of the bottom side was rusted-thru. I carefully cut that portion off the piece and snipped it along the folds to press it out flat and make a pattern for a new piece from it.

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Things went relatively well with the fabrication, other than the fact it consumed the entire day! Here's what I ended-up with after hammer-forming the new part out of 20-gauge sheetmetal and welding it back onto the top part of the donor piece that was still usable. Considering that most of it is not visible after the rockerpanel sheetmetal pressing is welded over it, I think it will do just fine. I'll be setting it aside until I get the work on the back end of the longitudinal channel finished since welding the inner rockerpanel pressing into place permanently must take place before welding on the A-pillar bottom.

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Entry: 3/3/06 - The rotted left longitudinal channel under the rear torsion bar was put under the knife today. After removing the brake, "banana" arm and shock absorber, I cut away the rusted heater tube and prospected to see how high up the channel the rust went. I trimmed back much of the rotten sheetmetal where the new rear longitudinal pressing will be trimmed to fit. The lock post was trimmed up to the bottom of the latch recess so I could get access to the rusted rocker panel support pressing, which I cut and will replace with a new pressing. I used my yellow paint pen to mark where I hope to make the grafting seams with the new sheetmetal pressing based on the health of the steel at that point. The thing to note is the welds will be hidden behind the spring plate for the majority of the patch.

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I cut some dowels to fit in the spring plate mounting holes and test fit the new rear longitudinal pressing. As you can see in the following picture, a lot of forming work remains to make it fit the area. Luckily I'm only needing that lower section because forming the entire patch panel would be a very time consuming job! Grafting a piece of steel muffler tubing into the void where the old rusted heater tube was should be very easy using high-heat epoxy sold as muffler patch at most autoparts stores.

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Entry: 3/5/06 - A new outboard seat rail support was wrestled out of sheet steel today, to stub-on about 1" back onto the top half left after the rot "amputation" was performed. The original pressing was a rather complex one which provided a flange at the bottom to spot weld it to the floor pan. My less fancy one copied the vertical bends of the original panel, simply spotwelded to a plain 3/8" wide flange at the bottom. Not pretty but it will get the job done and keep the weight focused downward from the seat rail from flexing the inner longitudinal panel as intended by the designer. I gave the entire thing a thick coat of Eastwood's Rust Encapsulator to seal the raw edges and new welds on the sheet steel. I'm kind of in a holding pattern on fitting the replacement sheetmetal pressing around the bottom side of the rear torsion bar housing until the heater tube replacement flexible tubing arrives. I feel it would be wise to have the contents of the channel in place before making any cuts on that expensive pressing.

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Entry: 3/6/06 - The rotten area on the inner longitudinal panel in the rear passenger footwell area got the patch treatment today. I cut out the section and grafted in a patch crafted out of 20-gauge sheet stock. A small patch in the corner is temporarily clipped into position with a red clip in the photo. This small patch will be welded in permanently once the new sheetmetal panel behind and under the torsion bar tube is grafted in. I also cleaned-up the flange where the back of the floor meets the base of the rear seat panel (to the left of the red clip in the photo). I decided to leave the strip of original floor and have a double-thickness of sheetmetal at this flange since it was so solid. I am going to leave the double thickness flange on the center tunnel as well. Not stripping the spotwelded floor pressing sheetmetal off these flanges should save quite a bit of labor and provide more material to weld the floor sheetmetal pressing to. Removing it would really serve very little benefit, especially since this area is seam sealed and hidden under sound proof matting. From the outside of the car, there would be no difference either way. When I finished with the patching and welding for today, I media blasted the left rear suspension pieces and gave them a coat of semi-gloss black paint. The completed longitudinal repair should look very good with new undercoating covering the new sheetmetal and new rubber bushings on the freshly painted suspension pieces.

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Entry: 3/7/06 - I needed a little change of pace today, so I took on the worn-out drivers door check strap bracket. I needed to use my acetylene torch to gas-weld closed the top side of the retaining pin hole in the bracket, which created a challenge with that much heat so close to the Karmann paint code plate. I didn't want to remove the Karmann plate so my solution was to cover it with a coat of a heat absorbing clay sold as a product called "Heat Fence" by my welding supplier. I needed to heat the bracket red hot so I could melt the new welding rod steel into the existing sheetmetal and get a very solid and cosmetically "pretty" weld. On the bottom, I simply MIG welded in the hole shut, since it's almost completely hidden from view. After a significant investment in diamond and carbide-tipped Dremmel steel cutting tips, I was able to bore out a 5mm hole for the retaining pin. As you can see from the following photo, the repair turned-out very acceptable before most of it is hidden by the door checkstrap..

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I test-fit a new door checkstrap using an M5 bolt as a substitute for the correct original retaining pin, itself held in with a "C"-clip. My goal was to keep as much of the two layers of original steel visible from the "good side" or the side seen when you open the door, it doesn't look like it was ever repaired. The back and underside of the bracket tell a different story!

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Entry: 3/8/06 - Today's task was fabricating the replacement heater tube that runs under the rear torsion bar tube. I ran down to my local autoparts store and picked-up some 2" plain steel flexible exhaust tubing. It occurred to me that if I cut slices out of the flexible tubing, I could make tighter bends, that is if I could weld the slices back up. I was able to make the necessary slices to the tubing to get the tight bends and weld them back up with my MIG welder. I test fit the finished tube into the opening to make sure of the longitudinal panel clearance before I can cut out the remaining rotten panels. I will be able to weld the new flexible tubing on to the original tubing and then plug any gaps with high-temperature muffler patching epoxy. As you can see in the following picture, quite a few cuts and welds were required to make the 2" tubing work but I figured the important thing was keep the diameter as big as possible to maximize hot air flow.

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Entry: 3/9/06 - Today I did a little dressing of the welds on the 2" diameter replacement heater tube and a coat of weld-thru primer to seal the welds from flash rusting. I thought a photograph showing the side-view of all the "slices" taken out of the flexible tubing to make tighter bends would be a good thing to look back on when I do the other side. The last 3" of each end are still flexible, which is what allows me to position the tubing in place with a rubber mallet. Once I cut away the remaining rotten sheetmetal around the heater tube on the car, I will have nearly 360 access for tack welding the flexible tubing into place.

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As is normal around CV joints, the area around the transaxle was coated with a thick coating of caked grease and dirt. I thought I had better do a thorough de-greasing of the area with my favorite de-greaser and scalding hot water before doing any welding in there for fear of having a fire in break out around the wiring harness and fuel line. The redeeming quality of caked grease and dirt is how nicely it protects the underlying surface from rust. The orange heater control valve looks almost like new once it was cleaned-off. You can see the dotted yellow line where I plan to make the cut on the plate behind the heater tube area. I'm stepping back and considering all the options of where to make the cuts for the outer panel graft around the torsion bar tube. The dependency on having the heater tube welded into place before the outer skin is going to dictate much of where the seam will go.

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Entry: 3/10/06 - Now that the whole heater tube issue has been put to bed, time to cut away all the rotten sheetmetal back to nice meaty points suitable for solid welds to attach the replacement pressing. My first goal was to save as much of the original reinforced, double-thickness metal surrounding the torsion bar tube opening and anchoring the spring plate cover with the four 10M bolts. As it sits tonight, all the rusty metal has been cut away, the lowest torsion bar mounting bolt anchor is gone, the mating surfaces have been spot sand-blasted, wire brushed and in the most visible areas, a weld flange bent into the joining surface. Tabs have been welded onto the original heater tube mounting bracket to allow for the slightly smaller diameter flexible tubing. I'm also test fitting the jack tube that will need to be welded in several points before the floorpan is welded into place.

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On the back side, all the rotten metal has been removed and the mating surfaces wire brushed to prepare them for a patch panel graft. In the following photo, you can see the extra material left on the patch I made to the inner longitudinal panel a few days back, an ample amount, not knowing how much I would need to graft but knowing the flange for the floor pan weld extended beyond the rear footwell wall over an inch. I'm pondering how to make sure the floor panel mates with the longitudinal panel. Test mounting the floor pan as I fit that rear longitudinal panel might be the easiest way to insure everything lines-up before committing to welds. Cutting away the old floorpan on the passenger side might be necessary to fit the new floorpan pressing... in other words much more work.

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Entry: 3/11/06 - Yesterday I thought test fitting the rear floorpan pressing would require hours of work to cut away the remainder of the passenger side floorpan. This morning about 20 minutes of playing with the floorpan pressing and I've got it clamped into place so I can use it to fit the rear longitudinal pressing. I thought the floorpan looked great in the car and just had to take a photo to help imagine it all welded in!

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Cutting down that huge rear longitudinal pressing into the little bit I need to fix the rot in the bottom of the channel went relatively smoothly. I was able to flange the leading edge so it tucks under the inner rockerpanel pressing, holding the panel in place. Tonight all the flanges are clamped into place, including the floorpan! It will be time to start welding the heater tube and jack tube into final position and then weld the entire longitudinal panel from the hinge post back! I'm very happy with how this patch panel went into place, it should blend in and be another almost undetectable repair!

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Entry: 3/13/06 - Today the heater tube repair was welded permanently in place and the joining point with the original tubing was sealed with a strip of muffler patch. I gave the entire inner longitudinal panel (all the original steel), the heater tube and new tubing patch a thick coat of Eastwood's Rust Encapsulator as one extra layer of protection from moisture. Everything is ready for welding the rear longitudinal patch in place next.

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Entry: 3/14/06 - The rear longitudinal patch is welded-in, the welds dressed and grind marks blended-in with a thin coat of JB Kwik Weld. I left the weld bead that will be under the rocker panel support pressing since it will be covered with the sheetmetal pressing. A top-coat of 3M weld-thru primer and call it good enough until I'm ready to coat the whole area with the Wurth high-build undercoat. Next step is welding the patch panel under the torsion bar tube on the inside, which should be a very small piece of steel.

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Entry: 3/15/06 - Inner rocker panel pressing was welded into place today, the welds dressed and a coat of 3M weld-thru primer to see the welds better.

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