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Multiscale guitar questions


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Hi.

I have a design in the works for an 8 string multiscale guitar and lots of questions. I think I'll keep posting them here as they come around. Some are multiscale guitar related, others are generally for guitar building...

So, question #1:

How to measure scale lengths on a multiscale guitar? Parallel to neck axis or parallel to strings? I know the difference will be minimum, but this is a bug in my central processing.

Question #2:

How to decide where the perpendicular fret will be? Lets say for a 25.5 - 27 fan as an example...

Question #3:

How to choose the truss rod's length for this kind of fans? Is ther a rule off thumb for scale length versus truss rod's one? 2 truss rods, one alone or one reinforced with graphite (or other material?) bars...

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So, question #1:

How to measure scale lengths on a multiscale guitar? Parallel to neck axis or parallel to strings? I know the difference will be minimum, but this is a bug in my central processing.

Same way you'd measure scale length on a regular guitar. Only difference is that the scale length on the outermost strings will be different to accommodate your chosen fan difference.

Question #2:

How to decide where the perpendicular fret will be? Lets say for a 25.5 - 27 fan as an example..

Largely a question of ergonomics. Perpendicular fret closer to the nut will make lower frets easier to use for chordal work, but make the angle on the upper frets more extreme, which may be uncomfortable/visually off-putting if you play in the upper registers a lot. Perpendicular closer to the body will make upper frets easier to work with, but make chord playing near the nut more difficult as the angle becomes more steep. Perpendicular fret locations around the 5th - 9th frets seem common.

Easiest way to plan and visualise the fanned frets is to visit this site and try playing with some of the variables that go into your design. You'll soon get a feel for what looks "right" and is practical to the player.

Question #3:

How to choose the truss rod's length for this kind of fans? Is ther a rule off thumb for scale length versus truss rod's one? 2 truss rods, one alone or one reinforced with graphite (or other material?) bars...

Standard 17" - 18" guitar trussrod will probably work fine for the kinds of scale lengths you're considering. Two rods is probably overkill and would involve more work in building and setting up than it gains in stability.

Based on my limited building experience I personally wouldn't worry about graphite reinforcement unless the timber I was making the neck out of risked being unstable (eg, one-piece figured wood), or I was making an unusually thin/long neck. Other more-experienced members may have a better idea about this than me.

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Andrews suggestion to use the on line fret finder is excellent, that is actually what I use for fan fret instruments, export it as DWG-files and import it into my CAD SW. But IIRC the tool can also export printable formats (PDF?)

I have become a big fan (no pun intended) of a perpendicular fifth fret as it still keeps the left hand in a reasonable comfortable angle when playing cords and the higher positions are all still very natural.

None of the eigth string fan fret guitars I have built have double truss rods. However I use graphite reinforcements on all my necks. Have a look at this:

http://peternaglitschluthier.com/eng_index.htm

and you will find some pictures of one of the instruments. The black stringers you see at the back of the neck is actually thin layers of graphite. I have tested this method and compared it to inlaying graphite in the middle of the neck side by side with the truss rod and this method is way superior as it also fight any twisting tendensies in the neck.

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Thank you very much for your kind replies.

I am sorry for not having explained myself correctly and previously. I have an AutoCAD block with bridge, nut and up to 26(?) frets placement. I just have to scale this block to the desired scale length (nut to bridge length) and that's it. I can also adapt it to scale for an existent neck and design the correspondent body and so on. Quite a handful block I must say...

For a multiscale guitar, I'll use 2 of these blocks so the job is only to align them on the perpendicular fret, link all the others and voilá, a fanned fret design. As stated in the first post, the question is just a bug in my mind for the difference will be minimum. In a 25.5 to 27 fan, do you measure the top (low strings) and bottom (high strings) scale lengths parallel to the strings or parallel to neck axis?

My design aims for a smaller fan, I guess (it's been done for quite some time and haven't rechecked yet), so I was also aiming the perpendicular at 12th fret. This will have to be revised. The design is yet to be finalized so this measures aren't final yet and they're metric, so I'll have to make the conversion for imperial in order to have a decent evaluation of sizes.

I want to reuse some doors as wood supplies. I have available 2 solid wood doors (mahogany I guess) and some other large scraps that will be used for this and more guitar projects. These woods are over 40 years old, so I guess they're worth the try. Just have to slice them to proper dimensions.

@SwedishLuthier - could you please link to a direct photo of that graphite reinforcement you spoke of? I searched your website and only found front sided guitar photos... sorry, major noob here.

Once again, thank you for your kind reply.

Some more questions will follow in a few days...

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I don't know if you saw that the on line fret finder have a "multiple" scale function. Punch in the two scale lengths and the fret number you want to be perpendicular and export a DXF-file that you can import to Auto-CAD. And you are ready to go. If that is to simple, I made my first multi scale by step by step starting with two standard scale drawings, isolating one single string on each with included smal fret "snibbits", placing the single strings side by side, aligning the perpendicular fret, extending the fret snibbits, adjusting the string spread, angling the bridge and nut, drawing the outline of the neck, drawing new frets by connecting the points were the fret snibbits cross the neck outline and you are good to go. Or simply use the dxf from the on line fret finder. ;)

Seriously, doing it the manual way is extremely time consuming, compared to getting the job done by the online tool. And the difference between the two ways to measure a fan fret scale will be minimal. You can also discuss if a fan fret scale should be measured from nut to bridge or from fret board edge to "bridge" (theoretical bridge placement that is...) as those measurements will differ slightly too. In the end the differences are minimal and personally I just use the tool and don't spend more time worrying about that part...

That link i pasted lived its own life...

Heres a picture:

neckbodyjointrensad_zpsc49485d6.jpg?923

The neck in case is a nice wood called Spanish Cedar or Brazilian Cedar, actually a wood within the mahogany family. It is extremely light weight, but I wouldn't trust it to hold for a 8-stringer without the reinforcement. So the neck is Cedar, maple veneer, graphite, maple veneer, graphite, maple veneer, cedar and so on. Very effective way to spread the graphite our and closer to the surface of the neck as the stiffness of the neck is greatly increased if the reinforcement is closer to the surface compared to buried deep inside the neck close to the center.

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In a 25.5 to 27 fan, do you measure the top (low strings) and bottom (high strings) scale lengths parallel to the strings or parallel to neck axis?

Nominal scale length is measured along the trajectory of the string, ignoring the intonation adjustments required to set up the guitar. FretFind 2D uses the same measurement when it draws a fretboard (have a look at the String Endpoints table it prints to the right of the graphical representation).

My design aims for a smaller fan, I guess (it's been done for quite some time and haven't rechecked yet), so I was also aiming the perpendicular at 12th fret. This will have to be revised. The design is yet to be finalized so this measures aren't final yet and they're metric, so I'll have to make the conversion for imperial in order to have a decent evaluation of sizes.

You'll probably find that having the perp at the 12th will make the angle at the nut too steep to be comfortable given the 1.5" fan difference. Perp at the 9th is (roughly) the midpoint of the fretboard, whereas perp at the 12th is the midpoint of the strings' length. Your fretting hand only moves about 2/3 the length of the strings while playing so it makes sense to make the fan equal either side of the fretboards' midpoint. This is probably why most fan fret instruments you see put the perpendicular fret around the 7th-9th frets.

I agree with Swedish Luthier - FretFind is probably the easiest way to make a fretboard/instrument template for multiscale and takes all the scaling calculations out of any AutoCAD block insertion system. Unless you have access to a CNC machine to cut the fret slots directly from the CAD file and are making a big run of instruments, most people just take a 1:1 print of the FretFind image, stick it to the fretboard blank and cut the slots by hand following each printed fret line.

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Back again

First things first, thank you very much for your replies. As suspected, and referenced before, the measuring thing parallel to neck axis versus parallel to outer strings was just a bug in my brain, cause the difference is almost none, but your answers cleared any doubts that I had on the subject.

Regarding the block thing in AutoCAD, well, I sorry again for thinking everyone knows AutoCAD... in AutoCAD, a BLOCK is a container of things, it can have lots of different uses, and lots of different properties. In this situation, this is a static block with the drawing of the bridge, nut and 26 (I think, could be more) frets, correctly positioned for the original scale length (can't remember, but that doesn't matter). Because it is a block, when one scales it, everything inside scales in the same proportion, so If the original scale length is, lets say, 25 inches from nut to bridge and I need a 28 inches scale length, all I have to do is to scale the length of this block and all the frets will be precisely positioned. So with this one block I can do any scale length without the need to use ever again a fret calculator spreadsheet or that link above mentioned. Scaling a block in AutoCAD is as simple as change its properties or use the scale command with numerical input or previously drawn reference for click input. No need to import anything from any file. I can do Mandolin or Bass guitar scale lengths with the simplicity of a few clicks, just need the scale length drawn. Drawing the frets is another task that will require to draw or copy each line to each place, but that is peanuts... I use AutoCAD because I know how to use it properly, I've been an Civil Engineering Draftsman for quite some time now, working on Dams, Bridges and some roads. From there to guitar drawing/design is just pure joy... If anyone needs some AutoCAD boost, ring me a bell...

@SwedishLuthier, that photo cleared all my thougths. How is it to sand the graphite to the final neck shape compared to sanding wood? I once sanded down some metal fillings done to a defretted guitar (to replace the removed frets), and that was weird. Very interesting and nice approach there.

Regarding the perpendicular fret, curtisa, this last reply is GOLD, thank you very much, so precious and detailed info there that I have never thought about and makes so much sense... again, thank you very very much.

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Regarding the block thing in AutoCAD, well, I sorry again for thinking everyone knows AutoCAD... in AutoCAD, a BLOCK is a container of things, it can have lots of different uses, and lots of different properties. In this situation, this is a static block with the drawing of the bridge, nut and 26 (I think, could be more) frets, correctly positioned for the original scale length (can't remember, but that doesn't matter). Because it is a block, when one scales it, everything inside scales in the same proportion, so If the original scale length is, lets say, 25 inches from nut to bridge and I need a 28 inches scale length, all I have to do is to scale the length of this block and all the frets will be precisely positioned. So with this one block I can do any scale length without the need to use ever again a fret calculator spreadsheet or that link above mentioned. Scaling a block in AutoCAD is as simple as change its properties or use the scale command with numerical input or previously drawn reference for click input. No need to import anything from any file. I can do Mandolin or Bass guitar scale lengths with the simplicity of a few clicks, just need the scale length drawn. Drawing the frets is another task that will require to draw or copy each line to each place, but that is peanuts... I use AutoCAD because I know how to use it properly, I've been an Civil Engineering Draftsman for quite some time now, working on Dams, Bridges and some roads. From there to guitar drawing/design is just pure joy... If anyone needs some AutoCAD boost, ring me a bell...

As a former CAD junkie in previous jobs I'm familiar with AutoCAD blocks and how they can be scaled, but I still think FretFind is an easier way to map out a multiscale layout. For a "normal" 6-string guitar build I can see that blocks could be advantageous, but for something a little more involved (non-standard numbers of strings, variable scale lengths, variable perp fret etc) I think FretFind makes the whole process a lot easier and quicker.

Assuming you start with a standard 25" scale frets/nut/bridge block, you'd need to insert it into your drawing, calculate your new scaling factor to go from 25" to 28" and then apply this scaling factor in the X-axis. If you then wanted to convert it to a mutliscale board you'd have to explode the block, thus losing any object grouping that the block inherently had, determine your string spacings at the nut and bridge for the given number of strings you want, draw in your outer strings to determine the boundaries of your scale lengths, calculate a new scaling factor to go from 28" to 25.5" for the treble strings, scale the treble side fret lines to this factor using the treble string as the axis of scale, apply a skew to the frets to accommodate your nominal perpendicular fret, add the fretboard overhang either side of the outer strings...You could have plugged all the necessary data into FretFind and exported the DXF to AutoCAD by now without having to do all the mental juggling to make the block work for you.

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Hello again

Latest AutoCAD versions allow for geometry constrains on drawing objects and Dynamic blocks can do a lot of work. I am not that familiar in creating dynamic blocks, but it is possible to build up a block just like what fretfind does, with variable number of strings, frets and so on. Huuummm I think I'll dive on that subject sooner or later...

I also think that your suggestions on the use of the block is way more complicated than what I really do. You see, the block only has a scale with fret positions marked. Scaling one of these blocks will not require me to do math work. I use the Scale command with the Reference option, which means I only need a distance and the block positioned in one of its ends. For me, it is way quicker than to use the FretFind tool but if it works for you, cool.

Have I thanked you already for your detailed info on deciding the perpendicular fret position? Truly awesome post... thank you.

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They way you propose to do it is totally fine. It will work. I think what the others are saying is that in FretFind2D, it is insanely quick and painless, which is best especially for those without access to a full CAD package or the know-how. Either way will get you there. For the multiscales I have done, I've used FretFind2D and quite like it, but that is because, though I know how to use AutoCAD, I prefer to spend as little time on a computer once I get home as possible.

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I Use TurboCAD so the Block funktion is not entirely different from the block funktion in TC. If you are fine with the scaling part, just go ahead and do it. The main thing; if you should care about that tiny difference, the anser is "not really".

@SwedishLuthier, that photo cleared all my thougths. How is it to sand the graphite to the final neck shape compared to sanding wood? I once sanded down some metal fillings done to a defretted guitar (to replace the removed frets), and that was weird. Very interesting and nice approach there.

Cutting graphite with sharp tools is a nightmare. I tried to plane a neck blank on my planer and one single run made small groves in the planer blades. Yikes! It dulls my spokes shave quite quickly, I have to sharpen it halfway through a neck carve compared to after/before a complete carve without the graphite. Sanding is OK, almost as sanding wood. However the dust will be even worse than ebony dust in that it blackens maple and other light woods. Be careful, blast away all dust with compressed air, clean your paper after every second/third stroke or so when you are approaching the final sanding grits and you should be fine. Wear a dust mask and long sleeves, the dust is not pleasant on your skin and I can only imagine what it will do if inhaled.

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Thank you very much, you all have been very helpful.

@Ripthorn -thank you for coming by. I dig that fretfind site/application. It's really interesting and usefull, however, I kind of get confused with nut and bridge widths for lack of experience. For me, this AutoCAD way is almost direct, I can start with the number of strings and their spacing's at nut and bridge and then experiment with scale lengths until I am satisfied.

@SwedishLuthier - Graphite dust is surely toxic for the lungs and general health. I will not delve on this level of details or graphite sandwich. I am not that experienced nor have the proper tools for that kind of work. One step at a time. It looks awesome, but too risky for me and I do not know where to get those thin layers of Graphite. Does the Graphite glues well with the wood?

OK, on to the next question

Question #4:

I am aiming at traditional 2 passive humbuckers for this guitar, namely DiMarzio's (don't ask why, I'm a DiMarzio guy). Should I leave the pickups perpendicular to Neck/guitar central axis, should I angle them or should I hack them up and slant the coils with a new base? 1st option will have coils poles aligned with strings, 2nd will not and 3rd might have a little. Ok, this is a matter of taste and aesthetics, but what are you common choices, PROS and CONS?

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Question #4:

I am aiming at traditional 2 passive humbuckers for this guitar, namely DiMarzio's (don't ask why, I'm a DiMarzio guy). Should I leave the pickups perpendicular to Neck/guitar central axis, should I angle them or should I hack them up and slant the coils with a new base? 1st option will have coils poles aligned with strings, 2nd will not and 3rd might have a little. Ok, this is a matter of taste and aesthetics, but what are you common choices, PROS and CONS?

Option 1:

http://strandbergguitars.com/wp-content/uploads/2014/04/IMG_1734.jpg

Pros - cheaper to buy than a custom slanted humbucker, more choices available to purchase from, can use readily available routing templates

Cons - some people feel if the angle at the bridge is too steep it may impact the output tone of the guitar in a negative way, particulaly the bridge pickup. Effectively you're doing a similar thing to a Fender Strat bridge pickup and rotating the bass-side of the pickup around further towards the neck, which makes the bass strings output of the bridge pickup more like a middle pickup.

Option 2 (and 3):

http://strandbergguitars.com/46-armand-hindrichs/img_2980/

Pros - as for option 1

Cons - visual aesthetics. Can be circumvented somewhat if you choose pickups with fully-encapsulated bobbins (eg EMG81), or blade-style pole pieces (eg Hot Rails). Some people don't like the look of a rectangular pickup twisted around on an angle. I don't really know if angling the pickup a few degrees with misaligned polepieces has a general effect on the tone. My gut says it would be minor, but I don't think I've seen any real tests by anyone to indicate otherwise.

Hacking up a standard pickup is something I've considered myself, but never had the opportunity to try. Other than the mechanical component of doing such a mod, the other important thing to consider is that as the bobbin is rotated around away from perpendicular the pole pieces need to be spaced further apart to maintain their alignment to the strings. This would limit the amount of rotation you could make on a standard pickup before the pole pieces start being too far away from the strings to be effective (or look any good!), particularly on the outside strings.

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curtisa answered it really well. I have used hot rails rotated at an angle and I have left them standard. Both ways work fine. Change in tone I can't comment on because I never A/B'd the pickup positioning. There are some guys who will custom make a pickup for you, but that gets pricey. What I might try on my next one is going with a narrower string spacing and getting a humbucker with wider spacing and hacking it up as proposed, but my next multiscale build is quite a ways down the road, as I am just finishing one now.

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@SwedishLuthier - Graphite dust is surely toxic for the lungs and general health. I will not delve on this level of details or graphite sandwich. I am not that experienced nor have the proper tools for that kind of work. One step at a time. It looks awesome, but too risky for me and I do not know where to get those thin layers of Graphite. Does the Graphite glues well with the wood?

Thanks! A bit off topic but the graphite can be found in any on line RC shop. Use epoxy as the solid graphite pars, sheets etc are essentially graphite fibers in an epoxy matrix. As long as you have an epoxy that bond well to wood (and possibly scuff sand the graphite to dull it slightly) you should be fine.

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