After a winter break from my Corvette restoration project (Maine winters can make the garage a pretty cold place) I’m picking up from where the last update left off. In this update the rear deck is test fit, aligned, and then bonded back in place on the rear deck. It’s about time, too – this car needs to start looking like a Corvette again!
So, to kick off the installation the rear deck was dry fit to make sure everything fit properly. If you recall, the original rear deck is being replaced with a donor piece so test fitting is especially important. If this were a reproduction rear deck some trimming would certainly be in order. However, I was unsure what to expect with this donor piece. As I started out I was a bit worried that some portions of the deck may have been trimmed back too far when it was fit to the original car it came from. Luckily, the fit turned out quite good.
Because I was working alone the rear deck was lowered onto the rear clip using a chain fall but two people could easily lift the rear deck into place. It’s quite light.
Once in place an initial alignment check was made before lightly clamping the rear deck in place using two vice grips with some wooden blocks to protect the fiberglass from damage. Once in clamped in place a more detailed alignment check was made. Specifically, the fit of the panel in the front to back and side to side directions was checked as well as the alignment (rotation) of the panel. To adjust the fit the rear deck can be lightly tapped with a rubber mallet and, as long as the clamps aren’t too tight, the deck will slide into alignment. Lastly, you also need to be aware of the relative thickness of the panels. If your matching two pieces of different thicknesses together you won’t be able to create a flush seam. In these cases you may find that you need to grind down the thickness of one of the panels to achieve a proper fit (this is especially true in the case of hand laid replacement panels).
During the alignment process I quickly realized I had created something of a challenge for myself by removing the tail lamp panel and passenger size quarter panels. Although removing these panels before removing the rear deck was necessary to preserve the bonding strips for re-use, removing these panels left me with very little in the way of reference points to use while aligning the rear deck. As mentioned earlier, if the original rear deck was going back on the car this effort would be straightforward – you could simply align the front edge of the rear deck along the roofline and be fairly certain the alignment would be very near original. However, when using a donor or replacement part this approach yields less certain results due to variations in panel size. Despite the uncertainties noted above this appeared to be the best approach for my fit up so the front of the panel was aligned with the front edge of the roofline.
Once the donor panel was aligned to the front of the roof line I then checked alignment at the tail end of the panel. Obviously this is difficult with out the tail-lamp in place, but I could at least tell if the fit was “in the right the ballpark”.
With the rear deck positioned front to back the side to side and rotational alignment was then checked. Again, I didn’t have many reference points to go by, so the fit was mainly checked along the roofline and door lines. In the end the alignment along these points was most important in my case. After all, I’ll be able to install the tail lamp panel and drivers side quarter to match into the final location of rear deck.
Now, for what it’s worth, I spent quite a bit of time mocking up the rear deck prior to bonding it into place. Much of this time was spent adjusting the fit at one point and then examining how that change affected the rest of the fit-up. In addition to these obvious positioning checks you also need to consider any future panels you’ll be installing and how those will fit up. In my case I actually mocked up the tail lamp and rear quarter panels to ensure the final alignment of the rear deck was reasonable.
I highly recommend taking your time during fit up and really checking the fit of all panels before bonding them in place. After all, once they’re bonded it’s a real challenge to get them apart again!
So, after fitting and checking the position of the rear deck, several alignment marks were made between the rear deck and the rear clip with a permanent marker to facilitate realignment later. Once marked the rear deck was removed and the bonding surfaces were roughened with 20 grit sandpaper. Next, after a thorough cleaning with lacquer thinner, I set to work applying the adhesive.
To start, a thick bead of exterior grade silicone was applied along the metal crossbar (not the bonding surface) that forms the roofline. Although this area was not originally bonded a bead of silicone here seemed like a good idea. In this area the crossbar and fiberglass panel are in very close proximity which could lead to ‘mystery noises’ if the panel vibrated at highway speeds or while driving over rough roads. Sure, it probably would have been fine without the silicone, but it seemed like really cheap insurance.
With the silicone in place a bead of epoxy adhesive was applied along the bonding surfaces at the roofline and along the back of the passenger compartment. Once again, Fusor 127EZ was used as a bonding agent (see the Tail Lamp and Rear Quarter Panel Removal update for additional information on this adhesive).
To make bonding the panel in place a bit more manageable, and because I didn’t have an unlimited number of clamps, I decided to bond the rear deck to the body in phases. In the photos below notice that I didn’t apply bonding adhesive below the door lines, along the rear quarter panels, or along the tail lamp panel. I elected to bond these areas in separate second and third phases, but you could certainly bond them all at once if desired. Just remember not to take on more than you can accomplish before the bonding adhesive sets up.
Once the adhesive was applied I lowered the rear deck into place, aligned it using the alignment marks made previously, and then set to work securing the panel in place using a series of clamps. In the photo below you’ll notice a steel straight edge is being used between the clamps and the fiberglass panel. During the test fitting of the panel I noticed the fiberglass was not laying as flat and even as I wanted it to – at each clamp location the panel was squeezed down ‘tighter’ than the surrounding areas which would have resulted in an uneven, wavy surface. Eventually I found that using a straightedge evenly distributed the clamping force and eliminated the waviness of the panel. In addition, during the test fit it become evident that using lots of clamps spaced closely together was key to ensuring a smooth, flat surface. And lastly, it’s important to realize that you don’t need to clamp the pieces together as tightly as possible, just tighten them enough to hold the two pieces in place.
While tightening the hand clamps watch for adhesive oozing out along the full length of the seam – this is what you want. An even line of adhesive oozing out of the seam provides you with assurance that you have good adhesive coverage while also letting you know your clamping pressure is fairly uniform (assuming you applied a straight, even bead of adhesive).
With the rear deck clamped along the roofline I double checked alignment one last time and then checked out the bonding area along the rear of the passenger compartment. Here clamping wasn’t possible so a series of 1 gallon containers was placed along the top of the rear deck over the bonding surface. Although this is a very low-tech solution, the added weight provided much needed downward pressure and ensured good contact between the two surfaces.
After allowing the adhesive to cure for a day the rear deck installation was continued by bonding the rear deck to the quarter panels.
As I started this process I went out of my way to buy long reach vice grip clamps to use while bonding the rear deck and rear quarter panel. However, during the test fit process it became obvious that I simply didn’t have enough clamps to provide a smooth, even surface (I would have needed way more clamps than I was willing to buy). So, instead of using clamps, I elected to use some #10 metal screws and washers to temporarily clamp the pieces together. Although this technique will require me to patch the holes later, it provides a significant number of ‘clamping’ points which will ultimately result in a better product.
So, with the screws and washers on hand, work was started by first drilling pilot holes at about 4 to 6 inches on center along the full length of the panels (be sure the diameter of the pilot holes are slightly smaller than the diameter of the screws). These pilot holes should be drilled through both the top panel and the bonding strip.
After drilling the pilot holes I then came through and drilled a hole in ONLY the top panel (this hole needs to be slightly bigger than the #10 screw). I suggest pulling the top panel out and away from the underlying bonding strip, placing a piece of sheet metal between the two parts, or somehow preventing yourself from accidentally drilling through both the top panel and the bonding strip – it’s quite easy to do and I learned this lesson the hard way. If you drill the large hole through both pieces you’ll need to abandon the hole location and create a new one.
Once you have the pilot hole drilled in the bonding strip, and the oversized hole drilled in the top panel, you’re all set to go. The great thing about this configuration is that it leaves the top panel free to move relative to the screw which allows you easily adjust the clamping force by simply tightening and loosening each screw.
With the screw holes completed, and all of bonding surfaces cleaned one more time with lacquer thinner, I again set to work applying a bead of Fusor 127 along the door jambs and along the tops of the rear quarter panels. Getting adhesive in along the door jambs was a chore, but I found spreading the panels using a screwdriver helped quite a bit.
Once the adhesive was applied the screws and washers were given a quick spray with WD-40 (to prevent the adhesive from gluing them in place) and then installed and tightened. It doesn’t take a lot of pressure to pull the panels together so be sure to work carefully. Although you can relax the pressure on the panels if you over tighten them, you want to avoid this if possible. After all, when you tighten the screws the adhesive is squeezed out from between the panels and, when you loosen the screw, the panels will separate and there may not be enough adhesive left in the seam to fill the void between the two panels. Since my goal was to create a solid seam free from any voids I worked carefully during the tightening process to avoid having to significantly loosen any of the screws.
After initially tightening the screws I came back through with a straight edge to check the fit of the rear deck relative to the rear quarter panel. The goal is to have a smooth, even, seam between the two panels that will require as little body work as possible. During this process the screws were tightened and loosened as needed to provide the desired fit and alignment.
As expected the clamping process created a bit of a mess with excess adhesive oozing out along the bonding seams. To minimize the amount effort that would be required to remove this material later, a putty knife and paper towels were used to remove as much excess adhesive as possible before it cured.
And finally, here’s the final bonded seam between the rear deck and the driver’s quarter panel. Overall I was quite pleased with the outcome.
With the driver side complete, I next jumped to the passenger side. Here the rear quarter panel is being replaced so my chore first included bonding the rear deck and bonding strip to the body tub itself (recall that the bonding strip was removed from the rear tub and then bonded back to the rear deck in a previous update). As shown in the photo below, lots of clamps were necessary to provide an even and uniform surface. Once clamped in place the panels were left to cure for 24 hours. < center> And lastly, the bonding strip for the tail lamp panel was cleaned and prepped for installation, and then bonded to the rear deck. Once again, lots of clamps were used.
In the end, fitting the rear deck turned out to require a fair bit more thought than I originally anticipated. Certainly my case was complicated by the fact that I was replacing my rear deck with a piece from a donor car (as opposed to reinstalling the original), as well as the fact that removing both the passenger side quarter panel and tail lamp panel left me with few reference points. However, despite this I was happy with the final fit and am confident that, once complete, the rehabilitated rear clip will look great.
So that does it for this update! With my winter break behind me my goal is to start developing more frequent (monthly) updates so be sure to check back from time to time. And lastly, be sure to stop by the new Corvette Restoration Forum to discuss the project and touch base with other Corvette enthusiasts!