I just read through your article about the home made mini logging tool. Instead of taping the wire, you could glue the wire to the pencil. It is easy to find a good water resistant glue. The next thing is the strength of the pencil, the point is the problem here. I think it's best to replace the pencil with a short iron or plastic rod.
Iron is better because of the strength.
A few weeks ago I sent you some improvements about the mini logging tool. Last weekend I tried to make the tool with these improvements. My suggestion was to glue the wires to the pencil but I noticed that this was a very messy method. Duck tape seems better to me. In their commercial they claim it to be water resistant so it should solve the problem of the tape falling of.