SADDLE RADIUS QUESTION FROM A NOVICE

[Johnny]

Hi everyone, I'm still learning about acoustic guitar setups.
Hope it's ok for beginners to participate on this forum.
I was wondering with a fully compensated saddle and B stg compensated saddle, ifI shape a radius onto the top by sanding it lengthwise on a radius block,will I loose the compensation?

You see I have a guitar with a 16" fretboard and the saddle is more towards 12".
The 1st E st in particular is to low.

I have a compensated B stg saddle on it.
The measurments I'm getting at 12th fret are:
1st stg -3/64
2nd stg - 4/64 (slightly above the line)
3rd stg -4/64
4th stg - inbetween 4/64 & 5/64
5th stg 5/64
6h stg - 6/64
Thank you.
Johnny

[kiwigeo]

If the top of the saddle has been shaped into ridges under each string to fine tune intonation then if you sand the top of the saddle youre going to lose the ridges and intonation will be affected.

If you've got a micrometer or an accurate ruler then measure from front of saddle to break point for each string and refile break point at same distance after reshaping the top of the saddle.

Re beginners on the forum.....yes theyre welcome as much as the pros.

Cheers Martin

[Puff]

Wee bit confused here Johnny.
From your string height measurements and comment on the (I gather treble) E being too low that you actually want to raise the action? Sandpaper on the saddle will do the opposite.
If the neck relief is ok then you want a higher saddle. An overall raising can be done with slices from a phone/credit card put in the slot under the saddle (full length and width of the slot). This is a common and totally reversible operation often employed at slide guitar workshops when participants turn up with low action weapons.
Once you have achieved the action height you want you can superglue the slices together and onto the original saddle or buy a new saddle and sand it down - sanding the bottom-not the top - to the same height as your pattern.

[Johnny]

Thanks guys.
Ok. I understand about re doing the compensation.
Puff, probably didn't explain myself to well.
Yes, I do want to raise the action, as the 1st E stg is the main offender.
I realize I can shim.

At the same time I'm pondering whether the fretboard and saddle radius mismatch (or my perceived radius mismatch) is the reason the 1st string is so low,(more curve on a 12" saddle) and why the individual strings don't feel even underneath my fingers.

I'm used to setting up an electric guitar where you choose your height, say 4/64 1st string, and set each individual string 1 to 5 at that height.
Then 6th string a little higher.
This way the fretboard radius match is guaranteed and the guitar plays better.

How do you approach the saddle radius of an acoustic?
Is there much importance placed on matching the fretboard radius, or is it just done roughly?

Also, how much do you guys worry about compensation on an acoustic saddle?
Many thanks.
Johnny.

[Puff]

Never tighter radius than the fretboard and almost invariably starting at about two inches greater. What is being aimed for is not a true arc but a slightly flattened and deformed one as with the angle of the slot which caters for most of the compensation a true arc would be 'crowned' toward the centre. Think of looking at a cartwheel from side-on and then taking two paces to your left. Added to that is the greater amplitude of the vibration of the bass strings so the whole thing needs to be 'tilted' up a tad on the bass side.
The tuning and string gauges used also puts in differing twists.
With experience - read trial and error or suck it and see - you can usually pick out a section of a French Curve that will get you pretty well in the ball park for overall shape and then it's on to the intonation

[Johnny]

Hi, so you're saying if the fretboard is a a 16", the saddle radius should start at around 18"?
And the reason for having a flatter radius than the fretboard is because with less curve,this will allow more height on the bass strings?
Thanks

[kiwigeo]

Hi, so you're saying if the fretboard is a a 16", the saddle radius should start at around 18"?
And the reason for having a flatter radius than the fretboard is because with less curve,this will allow more height on the bass strings?
Thanks

I dont aim for a target radius on the saddle...just as long as its greater than the radius at the end of the fretboard, it's asthetically ok and playability is acceptable around soundhole area. Too much radius around the soundhole area may make picking hard for some people depending on picking style. I play classical mainly so I like a fairly low radius across the soundhole area.

Adjustment of bass string height is done by adjusting saddle height rather than adjusting saddle radius. I would normally determine sadle radius first and once thats done I would adjust action last.

[Puff]

[/quote]And the reason for having a flatter radius than the fretboard is because with less curve,this will allow more height on the bass strings?
Thanks[/quote]
Ah no Johnny that was not what I was trying to convey and I don't think what I wrote said quite that.

[liam_fnq]

I'll have a go at this.

What Puff's saying is that he shapes his saddles to a curve that is not a true radius.

This is because of the different needs of the different string gauges from string 1 to string 6.

And, also because the tilting of the saddle slot for intonation distorts the way the fretboard radius relates to the saddle "radius". His wagon wheel analogy makes sense to me. I think this might be an example of paralax error.

correct me if I'm wrong puff.

[Johnny]

Ok I understand what he is saying now.
Seems everyone's got their own way of doing things.
This guy here traces the fretboard radius onto the saddle.

http://www.youtube.com/watch?v=EWuA2aFw ... r_embedded

(forward to about 6:20)

[Puff]

Johnny that method is fine for a saddle set at right angles to the centre line of the neck. The more you move away from the 90 degrees the more you have to move away from a true arc and into sections of ellipses - being "developed" arcs.
To use that method cut yourself a taper corresponding to the compensation angle of your saddle slot. Set one side of the taper at right angles to the centre line and your saddle blank against the other before drawing. Don't forget to leave that tad of extra meat on the bottom to get the action right
Few things worse than doing it all only to find that the bass strings rattle when you move up the fretboard

[Johnny]

Gotcha.
Now I understand and can visualize it.
This is when it gets enjoyable.
Thanks very much for your time!

[Puff]

No worries. Bon Aventure. It can be a beautiful bastard of a ride.