3/4 Cello Broken Neck Repair Part 4: Reinforcement

Reinforcement Dowel

On The table saw I cut a piece of Jequitibá or Yesquero Blanco for turning the dowel. I trimmed it to 3 inches long. Once I found the center of the piece I placed it on the wood turning adapter of my drill press.


I round it with a wood rasp and then checked the diameter several times with the Caliper while sanding it to the final size.


The Dowel ended with the same diameter as the wood bit used for the job.



The dowel is positioned at 90 degrees relative to the surface of the neck.


I found the necks center and drill the hole.


The surface of the Cello’s neck should be positioned at 90 degrees relative to the wood drill bit



After drilling I checked the fit of the dowel in the hole. Here you can see that it doesn’t entirely fit in .



I checked the depth of the hole with the caliper.



I checked the depth of the hole and marked it in the dowel to make sure it reaches the bottom of the hole.



I put masking tape before applying the epoxy resin. In the photo you can see beside the dowel, another one wrapped in sandpaper. The dowel has 4 channels that connect from the center of the bottom of it. At the bottom is a small depression that allows the resin to accumulate. Upon entering the hole, air pressure causes the excess resin out through the channels. This usually causes the resin from the bottom out of the hole, running the risk that any other area in the dowel to do so as well, thus compromising the integrity of the joint. The depression allows a build-up of resin maximizing the amount of air expelled and minimizing the amount of resin that is expelled together with the air.



With the dowel wrapped in sandpaper I lower the wall until the dowel entered without applying pressure.



Here is the last dry test. The dowel goes all the way down to the mark that was made with the pencil.



Again, here’s the equipment to apply epoxy resin, gloves and nylon brush.



The epoxy resin is uniformly applied into the hole, I let some drops of it into the bottom. Also I soaked the dowel in resin. Then I slowly push it in with the hand letting the resin and the air trapped inside to go up the dowel channels. Finally I place the clam and leave it alone for 12 hours.
In the first minutes after clamping, the dowel should be monitored because the level of resin in the dowel channels can lower. This happens because the wood absorbs the resin. If this happens, place several drops of resin on those channels until the receding stops.




At the sixth hour of curing the tape is removed leaving the clamp in place. I cleaned all the remaining loose resin around the dowel.
After 12 hours the press is removed. Here you can see the plug, darkened by the absorption of resin.




I cut the remnant dowel with a Japanese saw and sanded it clean with a 220 sanding block taking care not to damage the surface.



This is the final result. The wood is free of resin and ready to receive the fingerboard, thus completing the assembly.

Now we just need to clean the fingerboard and prepare it to glue it back to the Cello.

End of Part 4