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PostPosted: Thu Oct 05, 2017 10:33 am 
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Looking at the Antes plans for a soprano Uke.
The scale length is called out at 13.625.
When I measure the print the front of the bridge is at 13.625 to the nut.
The front of the saddle is 13.753 to the nut.
I checked some other dimensions they all seemed to be very close.
What am I missing?

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PostPosted: Thu Oct 05, 2017 12:14 pm 
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The difference is the compensation, because the string stretches as you fret it and that increases its tension and thus raises the pitch of the note it sounds. If you could fret without stretching, both lengths would be the same.

If you measure the plans you will find that the length from nut face to 12th fret is 13.625/2, whilst the distance from 12th fret to saddle peak is a little longer (2 to 3mm, or a little under 1/8 inch). This extra is needed to compensate for the stretching.

The amount in the plans is broadly correct, but the precise amount of compensation needed varies depending on what strings you fit, because different string materials stretch differently.

Many builders do the final shaping of the saddle top after stringing up, so they can place the saddle peak at the right spot for that type of string. Some (me included) give differential amounts of compensation for individual strings - the C is the fattest, and requires its saddle peak furthest from the nut.


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PostPosted: Thu Oct 05, 2017 3:14 pm 
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And DO NOT measure off the plans directly to build an instrument. They are for a reference only as paper will expand, contract with changes to humidity, as well as the vagaries of printers.

Use the measurements that are specified for critical things like scale lenght.

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PostPosted: Thu Oct 05, 2017 3:25 pm 
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Allen McFarlen wrote:
And DO NOT measure off the plans directly to build an instrument. They are for a reference only as paper will expand, contract with changes to humidity, as well as the vagaries of printers.

Use the measurements that are specified for critical things like scale lenght.



That is always good advice and something that many may not know since it is not inherently obvious. That said, it would appear that in this case it led the OP to another (not inherently obvious) fact -- string compensation.

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These users thanked the author Bryan Bear for the post: Dave Rickard (Thu Oct 05, 2017 8:15 pm)
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PostPosted: Thu Oct 05, 2017 4:34 pm 
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I highly recommend compensating the saddle. Maybe even use a thicker one than recommended. 3 mm?


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PostPosted: Thu Oct 05, 2017 5:03 pm 
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profchris wrote:
The difference is the compensation.


Wow talk about a brain fart.
Can I plead old age?

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PostPosted: Fri Oct 06, 2017 4:58 am 
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Dave Rickard wrote:
profchris wrote:
The difference is the compensation.


Wow talk about a brain fart.
Can I plead old age?


I do, all the time. Very useful on occasions :D

I thought it was worth explaining compensation, because starting builders read these threads and it can be a complete mystery to them.

Looking back at your original post, the numbers there suggest the plans are allowing a bit too much compensation. I make it 0.128 ins, or 3.25 mm (I'm a mixed units builder, inches for big stuff, millimetres for small).

For Aquila Nylgut strings, which seem to me to need the most compensation (cheap nylon requires about the same, but don't use those!), I reckon you need around 2.5mm for the G and A strings, and somewhere between 3 and 3.5 for the E and C respectively. Fluorocarbon strings might be closer to 2mm-2.5. And if anyone is building tenors, longer strings need a bit less compensation, these numbers vary with scale length. Steel strings stretch less, and so require even less.

So I'd be tempted to modify the plans slightly and put the front of the saddle at scale length + 1.5mm to 2mm. A 2mm saddle is enough to compensate each string individually, 3mm (1/8) gives you a little more room.

In which case the front of the bridge needs to move forward, otherwise you don't have much wood in front of the saddle.

If you want to go for a straight saddle and accept that the C string will play a fraction sharp up the neck, I'd set the compensation so the G and A strings are right, as these are most likely to be played higher up the neck.


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PostPosted: Fri Oct 06, 2017 1:36 pm 
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Thanks Chris, lots of good info there.
This is my first Non steel string so I was trying to wrap my head around the plans showing the saddle being perpendicular to the center line of the neck.
I'm leaning towards a 3mm saddle unless someone steers me in another direction.

A side note when Reagan was president he wanted the US to move to the metric system. My employer at the time started to move in that direction so I have metric and imperial measuring tools. After I got use to metric it makes more sense. Always look to the title block of the drawing to see what it was designed in.

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PostPosted: Fri Oct 06, 2017 4:19 pm 
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The only reason not to use a 3mm saddle is aesthetic - the Martin Style 0 ukes these plans are based on had a narrow saddle (1.5mm?). 3mm looks fine, just not like a Martin.

I was at school when the UK was transitioning to metric (50 years later and we haven't quite finished the transition), and the effects are odd. I can mentally picture an inch/foot/yard very easily. I can also picture 1mm, 100 mm and 1 metre. But 375mm means nothing in my head until I translate it into 15 inches.

So I decide my scale length in inches (13 inches for a soprano, the original Hawaiian scale length) and then convert to mm for actual measuring and cutting. Go figure, as they say.


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PostPosted: Wed Nov 01, 2017 11:51 am 
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You can always use the tried and true method..... measure to the 12th fret and then multiply x2.


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