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Multi dual compound non radius FB question
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=28294		 Page 1 of 1
Author:  Robert Renick [ Tue Jul 20, 2010 11:13 pm ]
Post subject:  Multi dual compound non radius FB question
I am sure that this has been tried, so please talk me out of it if it is a bad idea. 12" radius as standard for frets 1-5, but then instead of transitioning to a flatter radius across, I would like to keep the treble side flat from about fret 7 up through the end, while the bass side would maintain the 12" radius through. My thought is ease of play on the treble, sometimes in a bar chord that first string is hard to fret up there.

Please tell me if this is a can of worms or potentially comfortable,
Thanks,
Rob
Author:  TonyKarol [ Wed Jul 21, 2010 10:55 am ]
Post subject:  Re: Multi dual compound non radius FB question
never tried this ... but .. I think your transition will take more than 2 frets ... you are planning to get from 12 to flat (on half the board) .. not easy in 3 inches, without affecting the action drastically .. it will need to be much more progressive .. which IMO will get you to about the same as doing a 12-20 over the whole board ...

Take a couple small samples .. one a full width 12 radius, the other two pieces glued up.. half 12 half flat .. and see the delta that you have to transition from/to .... then try to see in your mind how you are going to get there ....
Author:  Ian Cunningham [ Wed Jul 21, 2010 11:27 am ]
Post subject:  Re: Multi dual compound non radius FB question
To test a theory such as this, get about half a dozen pieces of fingerboard-sized hardwood and go for it! You might discover something new.....
Author:  Barry Daniels [ Wed Jul 21, 2010 12:06 pm ]
Post subject:  Re: Multi dual compound non radius FB question
You can't change the profile a some point on the fretboard without affecting the levelness of the frets. And having level frets along each string path is what its all about. This is a non-starter in my book.
Author:  Bob Garrish [ Wed Jul 21, 2010 12:34 pm ]
Post subject:  Re: Multi dual compound non radius FB question
As Tony and Barry sort of alluded, the path under each string needs to be nominally straight (because the string is straight). What that means in practical terms is that any transition in 'fretboard shape' needs to be smooth from end to end and so there can be no 'corners' and in fact no areas of 'constant radius' if you want it to change at all.

ie: if you want a 12" to flat then it needs to be 12" at one end, flat at the other, and in between in the middle. You could make it turn flat sooner than the end but then you'd be looking at a concave area on your fretboard to keep a proper string path...
Author:  Eric Reid [ Wed Jul 21, 2010 3:06 pm ]
Post subject:  Re: Multi dual compound non radius FB question
Bob has it exactly right. You can define the cross section of any two points on the fingerboard. You can have any shape you like at those two points. The straight line string paths will dictate the shape of the rest of the fingerboard, and dictate the saddle shape as well.
Author:  Robert Renick [ Wed Jul 21, 2010 3:13 pm ]
Post subject:  Re: Multi dual compound non radius FB question
TonyKarol wrote:
it will need to be much more progressive .

Sorry for the confusion, my fret locations were very approximate, I do have this done and the transition is very broad.

Bob Garrish wrote:
As Tony and Barry sort of alluded, the path under each string needs to be nominally straight (because the string is straight). What that means in practical terms is that any transition in 'fretboard shape' needs to be smooth from end to end and so there can be no 'corners' and in fact no areas of 'constant radius' if you want it to change at all.

I did do this slowly with the string paths in mind, and seemingly I have them all flat, I do not have frets in yet. I will try to take some pictures if I can get something that is visible.

TonyKarol wrote:
which IMO will get you to about the same as doing a 12-20 over the whole board ...

Sounds about right.

Thanks for the thoughts, fret work will be tomorrow, so any other red flags have until then, then we will see what happens, should only be a few weeks before it is strung.
Rob
Author:  alan stassforth [ Wed Jul 21, 2010 11:23 pm ]
Post subject:  Re: Multi dual compound non radius FB question
just shape it by hand.
i've never used a radius do-hickey thingey,
and never had a problem.
if it's straight, it works.
go with a flatter fretboard!
Author:  Robert Renick [ Wed Jul 21, 2010 11:53 pm ]
Post subject:  Re: Multi dual compound non radius FB question
alan stassforth wrote:
just shape it by hand.
i've never used a radius do-hickey thingey,
and never had a problem.
if it's straight, it works.
go with a flatter fretboard!

This is the thinking I am following, since I don't have a fancy way of doing it, I am just going to be careful by hand and keep good string paths, if I had a fancy way, I would be glad to try the 12-20.
Thanks,
Rob
Author:  the Padma [ Thu Jul 22, 2010 12:04 am ]
Post subject:  Re: Multi dual compound non radius FB question
Start the radius at the nut and progress to a flat on one half might work providing you could pull off the leveling, however I would suggest starting at the nut and changing to flat by about the 12th would probably make for easier leveling, and if it don't work then pull the frets and radius the whole thing.

Bass and or treble sides have been radiused and the other half left flat with great success by several builders over the years. And compound radiuses work. Seems you just wanna push the envelop or compound to a flat.

Easiest way to find out is to get an old beater and slap on a new fretboard or two or three till you work it out.

If you use a long table belt sander to shape the board, you are pretty well guaranteed an easy leveling job right from the beginning.


blessings
duh Padma
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