How do I decide the scale length? Is it whatever I want or does it depend on the CGB (measurement)?
Currently building my first 3 string and don't want to mess up too badly!
yes...really, most builders start out build to a scale length that they are familiar with... Fender 25 1/2, Martin 24 3/4, etc....
And you can build to a scale length that is more or less proprotional to your CB... 25 1/2 on a 7 inch box is pretty ackward looking and neck heavy....
If you are playing slide you can get away with shortish scale lengths (down to 21") and still have if plenty playable. I've settled in on 24" as a good over all compromise, but still puzzle over each build to see what "feels" right...
good luck with your build... we want to see pictures,
im in the same possition you are im getting ready to build my first stick dulcimer and if all goes well ill be done in a week or two but good luck to you