Adapting the method to multiscale and 7-strings?

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Mark McLean
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Adapting the method to multiscale and 7-strings?

Post by Mark McLean » Sat Feb 09, 2019 7:38 am

OK - I have made one falcate guitar previously, so I have an elemental understanding of the principles and the methods. But my next project is going to add a few elements that complicate the planning. I want to make a 7-string (steel string, extra bass string tuned down to B) and also it will be fan-fret multiscale (27 inch on the lowest string, 24.7 on the highest). Furthermore, I am going to attempt a Laskin-style arm bevel. The body is drednaught size. I am still at the "thinking it through" stage, and will then go to a "draw lots of pictures to scale" stage.

My questions are about how to adapt the falcate plans from the book to accommodate these custom features. First - regarding fan fret. I have studied Martin's fan-fret build blog and appreciate the way he adapted the bracing to the asymmetry of the bridge, and particularly to the line of the pin holes not being perpendicular to the centre line. I think I can cope with that variation.

Second - the arm bevel means that the lower bout area of the soundboard is narrower on the bass side, compared to the treble side.

Thirdly - I need to arrange 7 pin holes around the braces. The book design for a six-string is 2/2/2, with them symmetrical around the centre line. The pin holes for strings 2,3,4,5 all sit pretty close to a brace. It would require a pretty big change to the spacing of the braces to make it 2/3/2, but that would keep it arranged in relation to the centre line (and the strings obviously need to be centred). The alternative is to give up having the braces symmetrical to the centre line. I could move everything a little towards the treble side (which is wider) and have the holes relating to the braces 3(bass side)/2/2(treble side). This would mean that the strings are centred, the bracing dimensions and spacing are preserved - but the braces are not relating normally to the centre line of the guitar. Would this be a problem, or OK because the arm bevel means the whole soundboard is effectively shifted off centre anyway?

Or does this recipe call for a pinless bridge?

All thoughts from the brains trust will be appreciated.

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Trevor Gore
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Re: Adapting the method to multiscale and 7-strings?

Post by Trevor Gore » Tue Feb 12, 2019 5:51 pm

I'm sure Martin will have more to say regarding your questions, Mark.

One thing though, I've found that arm bevels encourage your arm to damp the top, because the bevel brings the arm closer, whereas an arm rest moves it away. Bevels can look pretty cool, though, and offer an interesting build challenge, but don't seem to help much acoustically, whilst arm rests do. Something to think about when you consider the asymmetry issues.

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Mark McLean
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Re: Adapting the method to multiscale and 7-strings?

Post by Mark McLean » Tue Feb 12, 2019 7:17 pm

Thanks Trevor. Good point about the damping issue. I had thought about an armrest, but on a dreadnaught size my concern is the (dis)comfort of having your arm over the big body and I was worried that a rest just makes it wider still.

What about combining a Manzer wedge with a Gore rest, to reduce the overall width? Maybe that is my new plan. Another asymmetrical feature to add to this already crooked guitar.

Can I ask your thoughts about how to space 7 bridge pins with falcate bracing? Three between the braces (spreading them more than normal), or an extra one to one side?

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Trevor Gore
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Re: Adapting the method to multiscale and 7-strings?

Post by Trevor Gore » Wed Feb 13, 2019 3:54 pm

Mark McLean wrote:
Tue Feb 12, 2019 7:17 pm
What about combining a Manzer wedge with a Gore rest, to reduce the overall width?
You mean the Smith wedge :D ? I've done that. It seems to work fine. I got the impression from tap test results that the air resonance wasn't as strong, as the internal pressure wave didn't build as rapidly due to the back and top not being parallel. But I wouldn't have been able to tell that by listening to it. Maybe it just smoothed out the bass response a bit helping to avoid wolf tones. My wedge guitars have all been commissions which I've never had long enough to figure out properly what is going on. There's a challenge for you!
Mark McLean wrote:
Tue Feb 12, 2019 7:17 pm
Can I ask your thoughts about how to space 7 bridge pins with falcate bracing?
I'd put the extra one to one side, rather than spread the bracing. Probably not much in it either way, though. Other issues may force your hand when you tilt the bridge and bracing array.

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