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Hi folks,

I have to make a 7 steel strings acoustic with multi scale and I need your advices/thoughts. Any one have made some or just multi scale or 7 strings?
65cm treble scale and 72cm bass scale - break angle at the 7th frets (the one perpendicular to neck) - normal tunning (E A D G B E)
shorter trebles? longer bass? other break angle?
what about bridge plate? bracing? other ??

thanks in advance

Cédric

Hi Cedric. I'm in the process of designing a multi-scale guitar too and I wanted to let you know that there are a couple online tools I've discovered that may be helpful.

The first is Fretfind-2D
http://www.fretfind.ekips.org
and it will do the fret calculations for your multi-scale fretboard, for as many strings as you want (up to 12). You can specify which fret is the perpendicular one, too. It will also create a graphic picture in various formats (be aware that the only format that I could actually get to print to scale is the CAD format .DXF). The picture is really nice because you specify the string spacing both at the nut and the bridge, as well as the fretboard width. I printed it out, taped it together, cut it out and taped it over my hand-drawn fretboard on my full-size scale drawing. Since it provides a table with the individual scale lengths for each string, you can then do preliminary string tension estimates - which is what I really wanted to do.

I used Graham McDonald's MPUSTC tension calculator http://www.mcdonaldstrings.com/stringxxiii.html.

As an example, I found that the tension for a 25.4" scale guitar with medium gauge strings (.013 -.056) is approximately 175 lbs while using the same strings on a multi-scale (24.9" - 26.125") would be about 178 lbs. I was more interested in the relative difference rather than the absolute numbers to see if I had to alter the bracing in any way. In this example, I don't think I'd worry too much about a 3 lb difference.

Both tools are very flexible and allow a lot of customization of specifications.

Best,
Loren

Hi Cedric. I'm in the process of designing a multi-scale guitar too and I wanted to let you know that there are a couple online tools I've discovered that may be helpful.

The first is Fretfind-2D
http://www.fretfind.ekips.org
and it will do the fret calculations for your multi-scale fretboard, for as many strings as you want (up to 12). You can specify which fret is the perpendicular one, too. It will also create a graphic picture in various formats (be aware that the only format that I could actually get to print to scale is the CAD format .DXF). The picture is really nice because you specify the string spacing both at the nut and the bridge, as well as the fretboard width. I printed it out, taped it together, cut it out and taped it over my hand-drawn fretboard on my full-size scale drawing. Since it provides a table with the individual scale lengths for each string, you can then do preliminary string tension estimates - which is what I really wanted to do.

I used Graham McDonald's MPUSTC tension calculator http://www.mcdonaldstrings.com/stringxxiii.html.

As an example, I found that the tension for a 25.4" scale guitar with medium gauge strings (.013 -.056) is approximately 175 lbs while using the same strings on a multi-scale (24.9" - 26.125") would be about 178 lbs. I was more interested in the relative difference rather than the absolute numbers to see if I had to alter the bracing in any way. In this example, I don't think I'd worry too much about a 3 lb difference.

Both tools are very flexible and allow a lot of customization of specifications.

Best,
Loren

Here's mine....



it fans from 25.5inch to 29inch, which I personally feel was a bit too big of a range! Next time round I would also use either 7th or 5th as a perpendicular fret. Other than that, it was a great challenge to build!
Re: bracing.
Draw your body outline and get the bridge in the right place. You then have to work round this to get everything well supported.
Here's the inside of that one very early on in the voicing (and missing some bracing, of course)... As you can see, it's got a large bridge plate, and off-kilter bracing.

Thanks Loren for fret tool! I known about graham Calculator and I used it for some HarpGuitars.

I'm a lucky guy Jammy! Exactly what I have to do.
Can you tell me more on how it plays? such angle on firsts frets doesn't make it too hard to play? is it much more for jazz position (one finger one note) or 'conventional' positions such as bar chords?
What are the major differences in the making? not symetrical X brace? neck? head angle? ????

and what about the sound?

enought questions for today

thanks again,

Cédric

Gosh, no wonder guitar building is a lifetime hobby! So many things to build...

Jammy, I never saw your completed guitar, I remember following the thread sometime last year and thinking that it was innovative in design elements. I'm really glad I have got to see finished article, its fabulous, I'll just go and look at it some more.

The guitar plays really well, though it could use a setup at the moment actually!
The fret angle is a tricky one, it involves some re-learning of shapes, but that doesn't take very long. Within a couple of hours you're used to it and playing away. Barre chords are still possible, but sometimes can be a little awkward.
I would recommend using a less extreme range than I did, and pick a lower perpendicular fret. Say 25.5 to 28, and a 7th or 5th perp. That's what I'd do if I were to make another
RE making the thing:
The bracing was drawn out once I knew the bridge position, and I just had to wing it really - seemed to work out well.
You've got a couple of options when it comes to the neck. Either have a nice perpendicular break at the nut end, and a weird triangle behind the nut before the break (if that makes sense ) Like in this picture...

I decided, however, to "twist" the headstock to bring the break point round to meet the nut, much neater, but you'll need to pay attention to this when choosing your neck blank.

Thanks Jammy,

I have few things to plan and Let's go !!