amateur soundboard replacemant

[eltopo]

I have an old Ventura V-17 12 string. The old top was really ruined. The rest is in pretty good shape so now I have a new spruce soundboard ready to install. My question is, when setting the neck angle with a straightedge on fingerboard in relation to the bridge, what dimension should I be looking for between the straightedge and the top of the bridge? The original top and bridge were too messed up to take any kind of measurement.
Thanks in advance. I really enjoy this forum and have learned a lot.
Eltopo

[B. Howard]

With frets about .030-.050" more than your bridge will be. You want the final string height to be about 7/16" above the sound board.

[AA&E]

Originally Posted by B. Howard

With frets about .030-.050" more than your bridge will be. You want the final string height to be about 7/16" above the sound board.

Are you accounting for the varying thickness of bridges? I've had bridges vary from 3/16" to nearly 1/2" in thickness. Neck set angle has to be in relation to the bridge, not the soundboard. Perhaps I have misunderstood something in your post? Clarification please?

[clintj]

I think he might be saying your straightedge should be 0.03 to 0.05" above the bridge when checked unstrung. Strung at pitch, it should be pretty close to right as the tension pulls the neck into position.

[Ned Milburn]

We've discussed this before in other threads.

The desired action for an acoustic guitar should be somewhat near (between) 2 and 3.5 mm.

If we take 2 and 3 (high e, low E) and work from there, we need to decide how much saddle protrusion do you want (ie: how high does the saddle protrude from the bridge).

The basic math is simple. Double the desired 12th fret height and add this to the height of the fret plane that runs through the bridge (ie: straight edge on frets to bridge, then add the double desired 12th fret action).

For saddle protrusion, you can't have too much, and you don't want too little. Anywhere from 3 to 5 mm is fine, but sometimes there are guitars with slightly higher or lower than this.

If you aim for 3 to 5 mm saddle protrusion at the bridge, you'd want the neck (fret plane) to cut through the bridge 1mm lower than its top surface.

As another poster pointed out, there are different bridge thicknesses, and often bridges are thicker on the bass side to keep saddle protrusion more similar on bass & treble sides. Also, once some bow is in the neck, the saddle will need to be lowered slightly, so you may wish to aim about a half mm higher than your final desired saddle height.

The above should help get you started.

[eltopo]

Thank you gentlemen-
This is the info I was looking for.
I should have mentioned I have enough of the original bridge to get a height measure which is .350" and that is what I will be working with. I'll duplicate that in a new bridge and go for a target of .03" to .05" above the bridge for the straightedge check.
Thank you all again for the good help.
Eltopo

[redir]

If your bridge is .35in then it's probably close to the original height. That being the case you will want a straight edge to lay about 1 - 2/32nd inch over and higher then the saddle slot with the bridge in the proper location and the straight edge running along the center line of the fretboard with the frets in place. In practice that generally gets you a saddle height of at least 1/8th inch with string tension and good action.

For the 12-string I'd probably push for a higher saddle since the octave strings are usually pinned further away from the saddle and could use a bit more string break. Plus a few years down the road you may need to file some saddle to get the action better.

[Tom West]

Originally Posted by AA&E

Are you accounting for the varying thickness of bridges? I've had bridges vary from 3/16" to nearly 1/2" in thickness. Neck set angle has to be in relation to the bridge, not the soundboard. Perhaps I have misunderstood something in your post? Clarification please?

For me, a bridge that is 1/2" thick is way too thick. I set the strings 1/2" over the top, this results in a bridge around 3/8" thick. An extra 1/8" of material adds unnecessary weight that takes away from responsiveness. I also like to have a small footprint for the same reason. But that is just my way of thinking.
Tom

[eltopo]

Many thanks for all the replies-
I'm on my way with this now. When I first started trying some 'amateur' guitar repairs I never dreamed that a seemingly simple instrument could be so complicated construction and repair-wise. It's a fascinating world all it's own.
Eltopo