Which way to move the bridge ?

[jimbob]

My bridge position seems to be a little off because if I hit a harmonic on the 12th fret, then fret a note on the 12th fret, the harmonic is slightly sharp. I would expect them to be the same. If the harmonic is sharp, does that indicate which direction I need to move the bridge ? It is the same on all strings. I hope this makes sense...

[sunburst]

If the harmonic is sharp there's something wrong with the laws of physics!
Do you mean the fretted note is flat so that the harmonic is sharp relative to it? I think that's what you mean from what you've said, but the 12th fret harmonic (chimed at the 12th fret) must be one octave higher than the open string (unless the string itself is severely messed up) so it is the fretted note that is flat not the harmonic note that is sharp if I read you correctly.

If the fretted note is flat, move the bridge toward the neck.

[mandroid]

Measure 0-12 fret that should be the 12 to bridge on the E.

and others would be that distance + intonation offsets

physics of harmonic chime happens at 1/2, 1/3, 1/4, of the string

fretted 12 should be compared with chime at 1/2 the string.

[jramsey]

I'll usually take a little tension off the strings except the highest E and the lowest G, make sure both of those are really on the mark, and then actually fret the 12th fret on the respective string and do as follows:

If the 12th is sharp-move bridge towards the tail piece.
If the 12th is flat- move towards finger board.

The compensated bridge should cover the rest if everything is put together properly. Hope this helps.

[AlanN]

All have said it right. I use the '3 Fs' as a mnemonic:

Fret Flat Forward

[Fretbear]

I remember it using FLAT;
Fretted (note) low, away from tailpiece.

[bobby bill]

I remember it by figuring if the fretted note is flat it needs to be raised by shortening the sounding portion of the string between the fret and the bridge. Because the fret can't move toward the bridge, the bridge must move towards the fret. Frankly, this is easier for me to remember than which direction is forward on a mandolin.

[jimbob]

That was my guess...towards the headstock.
For clarification, yes, the fretted note is flat relative to the harmonic.
Thanks for the feed back !

[Mike Bromley]

If you mandolin is properly fretted, that is, of reasonable quality, the 19th fret harmonic works nicely as well. Like the 12th fret, the harmonic and the fretted note should be the same.