fretboard/neck/bridge geometry question on first build

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kominak

Posts: 135
Joined: Apr. 20 2010

fretboard/neck/bridge geometry quest...

Hi,
I just glued on the fretboard on my 1st build (blanca). I'm about to flatten/final thickness the fretboard before hammering in the frets. I made 2 shims - one 1.25mm thick (fret+0.25mm clearance under string) and 3.75mm thick (fret + 2.75mm clearance) . Placed 1st shim at nut position and 2nd shim at 12th fret.
Then I placed a straightedge on those 2 shims to simulate strings and these are the numbers I got: 8mm between straightedge and top at saddle position, 11mm between straightedge and sound hole.
Am I way off or are those acceptable numbers? The fretboard is currently 6mm thick, I can still make it thinner or incorporate some taper into it. Also, how much neck relief should I expect when stringed (high tension strings, Spanish cedar neck)?
Thanks a lot!

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Martin Kominak
Slovakia

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 26 2010 19:54:50

Jeff Highland

Posts: 401
Joined: Mar. 5 2010
From: Caves Beach Australia

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

Sounds great to me Kominak (but then I gave you those suggestions on another forum)
A lot of the guys here seem to like to measure with cigarettes lol
cheers
Jeff

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 26 2010 21:08:20

diazf

Posts: 52
Joined: Jan. 2 2006
From: NYC

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

Martin--
From your measurements it seems you will have higher than 11 mm gap between strings and soundboard only because the low E string needs more than 2.75mm gap unless you do a really good job leveling the frets and adding relief.

I suggest you put a 2mm shim at the bridge location and run a straight edge down the fingerboard from the nut to the 2mm shim at the bridge. If you're unable to get a straight angle than taper the fingerboard until you can. This angle will give you a nice 8mm gap between strings and gap once set up with bridge, saddle and proper string clearance.

Also search neck angle in past Foro discussions, Aaron Greene does a really good explanation for proper Flamenco set up.

On the next guitar do this with shims before locking in the neck with the back and you'll be sure to get the right neck angle and set-up.
Best,
--Fabian

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 27 2010 3:59:00

Jeff Highland

Posts: 401
Joined: Mar. 5 2010
From: Caves Beach Australia

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

2.75 is a pretty good average between the 3 for low E and 2.5 for high e that most aim for.
If he is measuring 8mm at the bridge with that he is good to go.
The action will increase slightly from this as the neck pulls forward into relief and the top comes up slightly.
If you are keeping the fingerboard at uniform thickness and have 8mm at the centre with 2.75 12th fret clearance then you should have 8.5 with 3.0mm on the bass string and 7.5 with 2.5 clearance on the High e.
I would almost guarantee you will then lose around 0.5mm at the bridge under string tension

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 27 2010 5:09:09

kominak

Posts: 135
Joined: Apr. 20 2010

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

Hi Jeff - good to see you here, too :)
Thanks for the tip with the shims - it put things in so much better perspective for me!
Fabian, the plan I have uses straight neck setup - no angle between neck and top. I suppose the action is achieved by the soundboard's concave curve. But it makes sense to make measurements before gluing neck to the top and make adjustments before it's glued on...

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Martin Kominak
Slovakia

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 27 2010 6:13:15

kominak

Posts: 135
Joined: Apr. 20 2010

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

Does anybody know whose plan is this? I bough it off ebay a couple years ago. I realize this is a rather stupid question to ask when I've already built the guitar, but I'm still curious. Thanks!

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Martin Kominak
Slovakia

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 27 2010 11:25:30

Armando

Posts: 302
Joined: May 27 2005
From: Zürich, Switzerland

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

Hy

Yes i know it. I have the same plan too and it is a plan drawn after a Marcelo Barbero guitar. If i remember well it's the 1948 model. That's at least what the blueprint plan says. i have no proof though whether or not this it's true, neither do i know how accurate the plan is compared the original 1948 model guitars built by Marcelo Barbero.

The plan was drawn by Bill Lewis and it is sold through lmii.com

There is another Barbero flamenco guitar plan around and it's the 1951 model which i think was the most sucessful model built by Barbero. This plan is sold through luth.org and that's the plan i was building after.

regards

Armando

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REPORT THIS POST AS INAPPROPRIATE | Date Nov. 27 2010 12:36:49

diazf

Posts: 52
Joined: Jan. 2 2006
From: NYC

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

Martin--
That plan is by Bill Lewis based off a 1943 Marcelo Barbero Flamenco guitar with some modification. You can find it at LMI or Luth.org I believe. Whomever sold it to you erased some information under the 'Flamenco Guitar' header.
--Fabian

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 27 2010 12:38:11

jshelton5040

Posts: 1500
Joined: Jan. 17 2005

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

quote:

ORIGINAL: kominak

Fabian, the plan I have uses straight neck setup - no angle between neck and top. I suppose the action is achieved by the soundboard's concave curve.

This does not sound right to me. Unless you have an unusually high arch in the top you will need to taper the fingerboard to achieve a proper setup. We use 3mm arch in the top and still put around 1.5 - 2mm deflection in the neck.

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John Shelton - www.sheltonfarrettaguitars.com

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 27 2010 14:40:11

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

Kominak

Your meassurements sound ok. I personally think the 3mm difference that there is between your meassurements at the bridge and at the soundhole is to big. I prefer when the soundboard and the string is as close to parrallel as possible. It makes the right hand relax more.
Remember that most guitars "set" when you have strings on and you´ll most probably end up with 0,5 - 1mm lower setup

To me it sounds like you´ve build with a lot of doming of the soundboard and a lot of angle in the neck/case joint?

I know the plan and I´ve build from it. Its good. But as I´ve said thousand times before, its not the plan but the hands that build that matters.

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REPORT THIS POST AS INAPPROPRIATE | Date Nov. 27 2010 17:07:39

Jeff Highland

Posts: 401
Joined: Mar. 5 2010
From: Caves Beach Australia

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

Was the plan sold to you by "Saved by the love of Jesus"?
I had the misfortune of buying a non flamenco plan from him.

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 27 2010 18:07:02

jshelton5040

Posts: 1500
Joined: Jan. 17 2005

RE: fretboard/neck/bridge geometry q... (in reply to Anders Eliasson)

quote:

ORIGINAL: Anders Eliasson

To me it sounds like you´ve build with a lot of doming of the soundboard and a lot of angle in the neck/case joint?

Anders,

That's what sounds wrong to me. He is using no deflection in the neck and depending on the arching of the top to achieve proper setup angle. It won't work without some deflection or a tapered fingerboard.

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John Shelton - www.sheltonfarrettaguitars.com

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 27 2010 22:30:33

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

Yes, agree. With to much arching of the top you get this angle betwen the strings and the soundboard which I dont like.

I´ve braced my tops flat for a couple of years. This way they end up with a very nice little dome over the top. Some 2mm. You can also arch the lower harmonic bar like Romanillos and have a more or less parrallel soundboard/string relation.

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REPORT THIS POST AS INAPPROPRIATE | Date Nov. 28 2010 7:27:41

kominak

Posts: 135
Joined: Apr. 20 2010

RE: fretboard/neck/bridge geometry q... (in reply to diazf)

quote:

ORIGINAL: diazf

Martin--
That plan is by Bill Lewis based off a 1943 Marcelo Barbero Flamenco guitar with some modification. You can find it at LMI or Luth.org I believe. Whomever sold it to you erased some information under the 'Flamenco Guitar' header.
--Fabian

Thanks a lot - that's what I wanted to know. There's a little confusing sentence in the plan that made me thinks it's not a plan of a Barbero guitar: "The top curve shown here is one I and many famous flamenco builders use - it's conical in shape. The Barbero and many other flamenco guitars have used a compund curve..." as if talking about some other guitar. But I guess those are Bill Lewis's comments.

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Martin Kominak
Slovakia

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 28 2010 11:16:34

kominak

Posts: 135
Joined: Apr. 20 2010

RE: fretboard/neck/bridge geometry q... (in reply to Jeff Highland)

quote:

ORIGINAL: Jeff Highland

Was the plan sold to you by "Saved by the love of Jesus"?
I had the misfortune of buying a non flamenco plan from him.

Exactly :(
It looks like he's making unauthorized copies of guitar plans from LMI, GAL, etc. and selling them on ebay. I just found a warning at GAL site.

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Martin Kominak
Slovakia

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 28 2010 11:26:52

kominak

Posts: 135
Joined: Apr. 20 2010

RE: fretboard/neck/bridge geometry q... (in reply to Anders Eliasson)

quote:

ORIGINAL: Anders Eliasson

To me it sounds like you´ve build with a lot of doming of the soundboard and a lot of angle in the neck/case joint?

top is braced flat and the top curve is achieved by changing the width of the sides - they are 88mm wide between heel block and soundhole and then gradually widen until 98mm at the end block. So there's a 10mm front-to back curve.
Also, now I noticed that the top is not entirely flat left-to-right. There's about 2mm curve (top in the middle is 2mm higher then on the sides), which was not intended... maybe there's the reason for the rather big difference between bridge and soundhole measurements? Top at the soundhole is almost flat left-to-right.
Neck has a back angle to soundboard - when placing a straightedge flat on top, there's 3mm space between straightedge and neck at nut. This, again, was not intended, but I think it's a good think it happened in my situation? I don't see how could Barbero achieve better string to top angle with this design? Or were these old guitars not that flat in this regard?

I've found here on Foro that your guitars end up with 8mm at the bridge and 8,5mm at the soundhole? What neck angle and how much top doming are you using? How thick is your fretboard? Is there some taper or is it flat? If you don't mind sharing... I'll definitely work more on the geometry on my next build.
Thanks a lot!

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Martin Kominak
Slovakia

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 28 2010 15:38:37

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

Working geometry on a guitar has one serious problem. The guitar is made out of wood which is a very lively thing.
This means that even though you try to make everything exactly the same every build, the neck angle angle (and other things) always varies a little bit. Thats ok. You can final adjust with the thickness of the soundboard or even taper it slightly.
I have a solera setup which is trial and error based, so I dont know exactly the angle of it. I brace flat and get the same dome as you (1,5 - 2mm) on the soundboard. I like a fingerboard which is around 5,5mm thick.

I think you should finish your guitar instead of worrying about what you´ll build in the future. Concentrate on what you are doing now. According to meassurements, I´99% sure it´ll end up with a ok string height.Not bad for a first build.

Good luck with the rest of your build.

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REPORT THIS POST AS INAPPROPRIATE | Date Nov. 30 2010 7:42:32

kominak

Posts: 135
Joined: Apr. 20 2010

RE: fretboard/neck/bridge geometry q... (in reply to Anders Eliasson)

Thanks a lot Anders. One more question - as you have a slight dome to the top, do you make the bottom of the bridge curved to copy the dome or do you make the bridge flat and "force" the glue joint?

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Martin Kominak
Slovakia

REPORT THIS POST AS INAPPROPRIATE | Date Nov. 30 2010 9:43:33

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: fretboard/neck/bridge geometry q... (in reply to kominak)

I curve the bridge to suit the dome. I like a small dome on the lower bout of the guitar.

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REPORT THIS POST AS INAPPROPRIATE | Date Nov. 30 2010 16:00:18