Want to see my Etching?

Sunday 30th December 2007 8 Hours

Etched elevator parts. Cleaned rudder parts except skin. Dimpled R902 spar and R918 attach strips. Drilled deburred and dimpled counterbalance weight and rib. Primed HS parts 1 side.

Quite a few bits got left behind in the first phase of parts preparation. In some cases, like the R-918 attach strips, it was just that I forgot a step. In others, like the rudder counterbalance weight and ribs, it was because I did not have the #10 drill required. However, I ordered that from Averys along with a few other bits and pieces and they had arrived a few days before the Christmas shut-down.

I finally got to try some spraying. First I set up the gun using a method I found on the internet. When I had a reasonable flat vertical spray pattern with a rate of flow that was neither too fast or too slow, I began to prepare the primer itself. First I had to dilute it to get the viscosity down to the 20 second mark recommended by Stewarts. Viscosity is measured by timing the stream of paint coming from a hole in the bottom of a special cup that is dipped in the paint and then withdrawn. You start timing when you raise the cup and you stop the clock when the constant stream breaks into drops. The thicker the liquid, the longer this takes. Getting to 20 sec seemed to take an awful lot of water. Incidentally, I could not find distilled water for sale anywhere (chemists [drugstores]paint shops both came up blank) I eventually found de-ionised battery top-up water in a motor accessories store and they assured me it was in fact distilled water. I had to stop at 25 second viscosity because I was approaching the maximum dilution of 33% allowed by the product instructions. Anyway, I thought is was no hard to have the paint a little bit too thick - better than having it too thin.

The spraying went well, I thought, but the paint took a lot longer to dry than I expected. The first lot looked as if it was not going to dry at all. However, after over an hour, it had finally dried. It is supposed to dry within about 20 minutes. I worried that the de-ionised water was chemically active in some way and was preventing the paint from drying.