Sunday, November 20, 2011

Hofner Colorama II restoration project (part 5) - filling and sanding the guitar body

In the last post (, we stripped down and scraped the paint off the body of our vintage Hofner Colorama II guitar. Before we even consider repainting it, there are quite a few issues that need our attention. These are mentioned in the previous post, so if you haven’t already read it, please feel free to do so now.

First of all, one of the screws holding the front tremolo/vibrato cover on was not gripping very well. This turned to be a result of the screw hole being too close to an edge, causing the hole to fall through that edge and making it impossible for the screw to get any sort of grip. We can’t just fill this hole, but rather, need to rebuild the surrounding wood so that it doesn’t happen again. Additionally, the lack of wooden support is the most likely explanation for the split in the tremolo cover, which was discussed here:

So first of all, we put the cover back on and mark the edge of it. This will give us an indication of what will still be hidden under the cover once the guitar is finished, and gives us some freedom to have a less-than-perfect finish underneath. The straight line being drawn here also shows us how far back we can build up the wood without it starting to interfere with the tremolo mechanism.

Once we’ve marked the limits, it’s time to remove some additional wood. This stops the join from being right where the screw hole will be, which would weaken the repair somewhat.

Once we’ve removed a suitable amount of wood, we shape a replacement piece of wood to fit in the gap.

Finally, we glue the replacement wood in place, as shown here (the hammer is just used as a wedge to hold it in place while the glue dries).

The next issue is that of the indentations cased by the pickup pole piece screws. These stick right out the back of the pickups and are actually causing the pickguard to rise up off the surface of the guitar and warp. I’ve decided to cut a little trough for each set of pickup screws to alleviate this. Since this is a hidden mod, I’m not too concerned about how it might look.

Marking out the edges of the trough.

Using a fine chisel to cut one of the troughs.

We also have a couple of broken screws to deal with. The best option here is to make a tool to bore a hole AROUND the broken screw. This is a simple matter of finding a piece of metal tubing about the right size and filing some teeth into it with a needle file.

We then fit the metal tube to a drill and drill a hole around the screw, as shown here. Note that it is extremely easy for this to skip across the guitar body while you are trying to drill, so take great care here, and if possible use a variable-speed drill set on very slow. To avoid the skipping problem, you can either use a drill press, or if that's not an option, drill a hole through a scrap piece of wood first that's the same size as the outer diameter of your boring tool, then clamp that to the top of the guitar so that the hole is right above the screw you want to drill out. Now drill down through that hole with your boring tool.

If the broken screw hasn’t disappeared up the inside of the little tool we just made, then you can remove it easily with a pair of needle-nose pliers, as shown here:

Now we’re left with quite a mess of missing wood, so the easiest option is to drill a normal hole that can then be filled with a piece of wood of the same diameter.

Here is the drilled hole, with our wooden rod of the same diameter.

Then we cut the wooden rod to length:

And stick it into the hole with glue:

You may remember we had one more issue with a screw hole too close to an edge. This was located at the bottom edge of the control cavity (under the pickguard). This one isn’t as bad as the one under the tremolo cover, so we are going to simply drill this out and plug it with some more of our wooden rod.

Drilling the hole:

Hole drilled:

Plugging the hole:

There are two sets of screw holes all around the pickguard, and so we will plug all of these using our superglue/toothpick trick, just like we did for the tuner screw holes on the neck here:

The screw holes that were used to secure the tremolo to the back of the guitar are so big now that I’ve had to plug them with kebab sticks instead of cocktail sticks.

And after being chiseled flat:

Finally we’re in a position to start filling any imperfections in the surface of the guitar for which we will apply some car filler (e.g. Bondo). Simply apply this to any areas with imperfections.

And then sand off:

We repeat this process for the other face of the guitar (and don’t forget the sides).

After repeating this process several times, we are more or less ready to think about painting the guitar.

1 comment:

Anonymous said...

Using a dowel that has its wood grain going opposite the body wood will create uneven expansion with humidity changes. This can make a raised or depressed spot in the finish. Best to make plugs that have the same wood grain direction.