The strings length are too short. This is the reason why the pegs cannot keep the tunning. Furthermore the piece where the pegs are fixed should be in a curve shape, like you can see on the harps or inside the piano. Different strings lenght and gauge combined with the curve shape make better to tunning the strings.
To tunning the strings, since you have 12 strings, you can use the diatonic or even the crromatic scale.
Congratulations for the nice instrument and very good idea.
Comments
The strings length are too short. This is the reason why the pegs cannot keep the tunning. Furthermore the piece where the pegs are fixed should be in a curve shape, like you can see on the harps or inside the piano. Different strings lenght and gauge combined with the curve shape make better to tunning the strings.
To tunning the strings, since you have 12 strings, you can use the diatonic or even the crromatic scale.
Congratulations for the nice instrument and very good idea.
Very nice, have you considered nylon strings?
Well done, great idea. It is a lyre right? No ideas about tuning.
No advice, really. I have seen some instruments of this scale on ebay called Mandolins - obviously not the usual mandolin.