Just realized that you aim at a total length of ca. 15 m. This should work with a variant of @HB9BCB ‘s 3-band design with traps (40-30-20, the 20m should also do okay for 10m) if you increase the inductances a bit and/or add a rather small loading inductor at some clever place. Or just build it for 30-20-10m and design a switchable matching circuit for 40m at the base. Not sure if saving ca. 3m of wire is worth the effort, but this should do the trick.
Edit: Basically, the current design should do the trick with ca. 16m total length.
