[CAUT] Duplex angle

[Alan McCoy]

Hi Mark,

Yes you are making sense. I like it!

So how did you arrive at your 15-22 degree parameters? If the angle is less
you get more unwanted noise and if too steep, it is less tunable and the
string digs into the capo more?

Thanks!

Alan


> From: Mark Cramer <Cramer at BrandonU.ca>
> Reply-To: "College and University Technicians <caut at ptg.org>" <caut at ptg.org>
> Date: Wed, 08 Nov 2006 17:06:13 -0600
> To: "College and University Technicians <caut at ptg.org>" <caut at ptg.org>
> Subject: Re: [CAUT] Duplex angle
> 
> Hi Alan,
> 
> I'm actually looking for 15 degrees as a "minimum" and about 22 as a max.
> 
> This angle measured, at the capo, as an upward deviation from the plane of
> the speaking length of the string.
> 
> Glue some card-stock onto the side of a small but square peice of wood (size
> of a key-dip block, but only the width of a unison). The card should
> protrude about 1/4" above the surface of the block.
> 
> Cut a generous "V" from the card to allow for the capo.
> 
> Starting at the capo "V" trace a line 15 degrees upward (or whatever your
> parameters are) from the surface of the block onto the portion of card that
> will stick up between the strings in the front duplex. (is this making sense
> Alan?)
> 
> Any case, you will have a defelction guage you can reach into the action
> cavity with, and press up against any unison to observe front-length
> deflection.
> 
> i.e.: viewed from the side, the string will be parallel with your line, or
> perhaps a little steeper.
> 
> I always find it interesting, no matter how it appears by eye, how nice a
> job the staggered duplex bars do of keeping deflection fairly even from note
> to note... as if by design. ;>)
> 
> best regards,
> Mark Cramer,
> Brandon University
> 
> PS Don't throw the block away just yet. My "permanent" one actually has a
> plastic key-top (rather than card) as a  side "fence," and I use it to
> ensure treble strings travel a straight line across the capo. With strings
> de-tensioned, do a preliminary string-spacing by pushing the string sideways
> til both string segments contact the fence parallel.
> 
> 
> 
> -----Original Message-----
> From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org]On Behalf Of
> Alan McCoy
> Sent: Wednesday, November 08, 2006 3:21 PM
> To: College and University Technicians <caut at ptg.org>
> Subject: [CAUT] Duplex angle
> 
> 
> Hello,
> 
> Point of clarification regarding "counterbearing angle."  I want to check
> out an assumption of mine about this. When there has been discussion about
> this on either list, some angle, for example 10-15 degree, is said to be in
> the ballpark of what we are looking for. The question is which angle are we
> referring to? The angle formed by the capo at the vertex, or the angle
> formed by the counterbearing bar as the vertex?
> 
> These would be equal only if the speaking length and the length from tuning
> pin to counterbearing are exactly parallel.
> 
> Of these it seems that the angle formed by the capo would control in part
> the effectiveness of the string termination, i.e. preventing loss of string
> energy into the duplex. Whereas, the angle formed by the counterbearing bar
> would have more to do with tunability & tuning stability and also the tuning
> or detuning of the duplex segment.
> 
> In a fully-strung instrument, how would I measure these different angles?
> 
> Thanks for you thoughts.
> 
> Alan
> 
> -- Alan McCoy, RPT
> Eastern Washington University
> amccoy at mail.ewu.edu
> 509-359-4627
> 
> 
> 
>