The 50-50 Rule

[Rob]

After waiting a long time was able to get my hands on a PB elephant ivory blank nut and saddle to match the 16inch radius on my fret board from a lad who runs a company in Dover Ohio.Had it brought by hand over the boader to make things legal. Getting a  Godin thin pick-up wire to replace the round brutal Fishman piezzo which has given me all kinds of lost volume trouble due I think from poor perfect contact below the strings. The pick-up has all kind of volume on its entire length on a pencil tap test.

 To sand new saddle to perfect height the 50-50 rule comes into play and this is how read the drift of the theory.Tell me If Iam correct.

 

With the new thinline wire in the slot and the top of it now becoming the new depth of the slot ,you don't want more than 50 % of the saddle height at its highest point (between D&G strings) in the slot.

Have marked perfect intonation beteen the D&G strings using Gary's previous  25-5/8"total scale length calulation which is just a tab to the front of center down the saddle.

 My other question is since the saddle slot has exact intonation angle in the bridge from specs Martin gave me should I also sand to that same distace on low-E and high -E for touch points on the saddle? Have it marked right now but waiting for the correct answer from a Martin player who has a strobe tunner and can verify his settings-Thanks -Rob.

[Jeff Highland]

Please don't be offended, but I don't think anything you have said is correct unfortunately.
Your saddle height is going to be where you need it to get the right string height at the 12th fret and what percentage is in the slot is irrelevant.
Same thing with the nut, the slots have to be the right depth relative to the frets, the very top surface of the nut is then cut down so that about half the E string is exposed and a all the e string is embedded.
You cannot get perfect innotation by measurement, it is affected by string type and action height.
You need to get your action right first then check and adjust the innotation by setting the break point on the saddle appropriately

[Rob]

Not afended at all Jeff. All my info comes from a artical adapted from artical by Ken Parker for Fishman called "The Finer Points Of Pick-Up Installation. My strings are sitting are 50% on the bass strings and imbedded on the B and high -E strings.Have read that 50-50 rule before Jeff. In Ken's artical his 50-50 rule with diagram included shows a cutaway side view of installed pizzo in the slot width.It tells not to deepen slot too deep to achieve only 50% in the slot as it will greatly affect volume. It said to remove material from bottom of saddle. It also shows to add a 5% backtilt on the bottom of the slot which he said reduces D-shape bowing of the slot under full string pressure and states it helps get the best possible ( wire - bottom saddle ) contact. Its shows touch pointjust slightly forward from middle of saddle and recommends ramping the pin holes which my pin holes are.
I know this old clunker will never have low action at the 12th because the the top has a unfixable warp under the bridge causing a eye visable forward tilt.The neck is straight but my guess not quite the correct drop off angle from the body when comparing it to my prized Guild.Before Itore it apart to add all three new parts Idid have the clearance under the 12th on the low -E to just under 3/32nds .I know this should be livable causing a tiny bit of sharpness when you get down to the sixth or seveth fret but not too noticiable for most ears. Thats my goal to have it down that low when back together.
cheers -Rob

[Eugen C]

I am a novice in these things but regarding your "unfixable warp" I think that this can help: http://fretsnet.ning.com/forum/topics/12-string-sigma-with-bellied

[Rob]

Thanks for the pics . My local liuther said because of all the cosmetic build-up to feather out bad drop-off angle from the back of the bridge to the back corners thats as good as it gets but is still playable.The whole mess was all caused by a broken sound rib that was left unattended in a damp basement for years.Mother nature wasn't kind.
Out of curiosity in a Granda with a inside the neck stock in front of sound hole,with a serial # 51.1.23 does that mean 1951 Jan.23rd or just a bad assumption? Tried to find a date chart on the net but struck out.
I know its not a 1969 Martin N-20 but still call it my Willie Nelson (Trigger) guitar -Rob