Hi to all,
I have an old, slightly knackered, Stagg jumbo acoustic six string guitar that I don't use, as I have other better acoustics. The thing is that I'd really quite like to have an acoustic Bass guitar also, so I was thinking of putting 4 bass strings on this old guitar instead of spending cash that I don't really have on a new acoustic bass.

Has anyone done this? Is this a good idea or not? If not then why not?
Dreamer

I am not a luthier but I am both a bass player and a guitar player. The scale length of a bass is quite different from that of a guitar (acoustic or electric, doesn't matter). Additionally, the tension of strings tuned to pitch will be different for a bass. The construction of a the typical acoustic guitar is just too delicate to simply change it for bass. Long story short, don't attempt this trick at home, kids.

Roger

No, definitely not! Several reasons: 1] The tension on bass strings can be enormous, so you will probably bow the neck, if you don't actually snap the headstock clean off; 2] the scale length on a standard acoustic will be too short to allow you to tune the bass strings to pitch; 3] the machine heads, nut, fret dressing, bridge and string pegs are all designed for guitar strings, and wont be able to accept bass strings without major modifications. Basically, it can't be done.

If you can't trade in your Stagg for a reasonably priced acoustic bass guitar, you might, perhaps, want to try setting it up as a baritone guitar (with the heaviest gauge acoustic string set you can find), but all the warnings above still apply, and I personally wouldn't want to attempt it.

Alternatively, why not set it up with an open tuning, such as DADGAD, which could be a fun and inspirational alternative instrument option to have to hand, even if it is not a bass. Easy to reverse if you change your mind!