Decisions - scratch build 7 string, string spacing, scale length, pole-to-string and lots more..

[NickK-UK]

I'm designing my first scratch build through-neck 7 string, fixed bridge mono-scale and I have some questions as I pause for thought. This is a little convoluted as I'm showing my thinking but the TL;DR is about getting the best accuracy/articulation out of the pickups with a 26.5" scale. This is for rhythm guitar but I'm aware modern rock/metal covers more fretboard, and I'm used to playing a 25.5" scale with the strat for reference with the purpose of adding some lower register.

First is around the relationship between pickups, string width and bridge selection.

I want to use Seymour Duncan Sentient and Pegasus pickups - the datasheet on these state 2.412" (62.26mm) top pole to bottom pole with 0.402" (10.21mm) pole to pole string spacing.

Bridge	outer pole-to-pole (mm)	pole-to-pole (mm)	Difference outer to pickups (mm)
Schaller Hannes	75.6	10.8	13.34
Hipshot	73.5	10.5	11.24
Gotoh 510	63*	10.5

* this datasheet seems wrong - I would expect this to be 73.5 or given the same p-p dimensions and 7 strings. So let's say this is the same as the hipshot.

Now I know that wide hum bucker is 10.2 spacing and Floyd Rose is 10.8-10.75, so these have less spacing than an FR bridge. I also know that the strings will not be completely parallel as the nut will be an equivalent 6 string of 2.05 (52mm) or slightly wider (I have longer fingers/wider hands).

As the guitar pickups are positioned to get the best second (even) harmonic warmth for the neck with lower chords and an even spread for bridge position. A mono-scale pickup is going to be a compromise anyway. This would then given the best possible spot for the pick up vs fretboard.
I know that the distance to the magnetic field of the low string (most energy) and the highest string (most sensitive to human hearing) is likely to create a natural frequency response curve so it equalises through the distance of the string.

This would then lead to the strings fanning out - thus reducing the difference/error between the pole and the string position. I know the internet seems to not really care about this but for me this seems like a logical detail that make sense as less error means better sound and more accurate articulation. I know that the pickup coil itself spans the strings but to me the more even (and identical) spacing the string in the magnetic field, the more neutral/even tone it will have. However the humbucker design needs its strings close to parallel to ensure both sets of coils are getting a similar common mode signal.

Now to my point - a 52mm 6 string nut is a 10.4mm spacing which means basically over a 673.1mm (26.5") that's, well, peanuts 0.1mm deviatiom given a 10.5mm bridge spacing, thus the 10.21mm pole-pole spacing. Sure it will reduce the pole to string error an insignificant amount (ie 0.0x mm) but the outer edge strings will be still quite a distance from the outer pole.

Now I could go for the 10.8 spacing (ie FR spacing) but it's likely that this would have more sloping off of the highs and the lows with the same pickups. So I'm thinking a 10.5 would be reasonable, even with the larger string amplitude on the bottom end but I may move to a 27" scale to allow for thinner strings and better definition (without having too much mass banging around the fretboard). I suppose I could calculate the tension in the strings to check the 27" with higher fret positions and see how that would feel.

Decisions decisions.

I'm currently favouring a 10.5mm bridge spacing, a 10.4 nut spacing and a 27" scale length.

 

[MaxOfMetal]

Just have fun with it.

 

[Purelojik]

yea, i think youre definitely overthinking things here man.

Choose a bridge and use the site for E-e spacing and choose a typical E-e spacing for the nut
Choose scale length
use fretfind 2d to map out your fretboard. and add some space for the overhangs like 0.130 in or something on either side.

either print out the fretboard by hand and make a template for the FB and neck, or take it into software and make a 1:1 template either drawn out or digital. then proceed

 

[NickK-UK]

So I may as well make this a build log (if you excuse the wooden pun).

Hardware

Tuners	Schaller M6 Pin Locking - black	The concern I have with these are the 2mm (80-guage) maximum string gauge (possibly less with coating etc)
Nut	Bone	Standard spacings
Fretwire	Jercarr 57110 jumbo - stainless steel
Bridge	Hipshot 7 string fixed thick base - black	10.5mm spacing
Pickups	Seymour Duncan Pegasus-7 - Bridge Seymour Duncan Sentient-7 - Neck	I'm going to mount these on the Maple/Mahogany through neck.
Truss rod	Single Dual action	Headstock adjustment
Strap pins	Schaller locking
Pots	CTS

Construction (through neck)

Scale		27" (685.8mm)
Neck - centre	Hard Maple		For the balanced sound, I'm hoping to get some quarter sawn.
Neck - layer 1 (thin)	Ebony		Still thinking about this - the concept is that the ebony would bring some clearer upper registers
Neck - outer layer 1	Mahogany		For some fat warmth. Again hoping to get some quarter sawn.
Wings	Alder	Rear scalloped, arm relief
Front & headstock front	Maple	Carved
Binding	-	-	Tempted to try to put a binding on the guitar but I'm shaping the body so I think it may be better to not complicate further!
Fretboard	Rosewood	12" radius, 24 frets	Fender has 9.5" and I'm concerned with a large bottom gauge string that too rounded will buz, this is for chords mostly so some radius is going to be more comfortable.
Finish	Clear Shellac

So the concept is that the mounting points for the pickups will span the hard maple and mahogany as I believe that just as the string vibrates, the wood vibration of the pickup itself against the string also adds the tone to the sound.
In terms of look - a clean maple guitar with a dark neck and black hardware seems to be the design Note this is for the experience in making as well as the end product so if it takes longer, patience


I'm less worried about the electronics. I built my own 24 bit ADC with a -150dB noise floor for audio analysis and can work that out.

 

[NickK-UK]

Ordered:
* SD Pegasus & Sentient 7
* Schaller M6 135 locking 4 top 3 bottom
* Gotoh 510fx-7 bridge

May need to get a 41-42” inside length case built too, i have some ply baltic birch that i could use for this just need to check dimensions. Otherwise the local timber yard will happily cut up one of the large boards to dimensions. I could probably make one for the old strat at the same time.

 

[StringPluckery]

I'm digging the overly organized planning process /detail nitpicking on this as I go through the same thing with a lot of my builds. Though, I think were that detailed process really shines is recording measurements to get a repeatable excellent setup.

 

[NickK-UK]

I'm digging the overly organized planning process /detail nitpicking on this as I go through the same thing with a lot of my builds. Though, I think were that detailed process really shines is recording measurements to get a repeatable excellent setup.

I’ve learnt the 5Ps - planning prevents pish-poor performance

The next step is get a make a paper print out.

I have a couple of ideas - first being the neck is not parallel and thus the entire neck-thru follows. Second is focusing on the neck and how to tack that :
a) 15mm thickness for the tuners
b) 10-15deg sweepback as this is a fixed bridge will apply enough force on the nut
c) straight string for 4top, 3bottom
d) get grain to follow the angle by doing an angled cut - I don’t think not aligning the head out have enough strength with the relatively thin head.

If I want a binding then I would need to cut the instep by routing it before the front is carved whilst the block provides a flat surface for the router.

Also having seen the underside of the SD pickups they have screw threads for poles so I’ll need to get the calipers out to check the sizings.

 

[lost_horizon]

I’ve learnt the 5Ps - planning prevents pish-poor performance

The next step is get a make a paper print out.

I'm at that stage in my build...

Also having seen the underside of the SD pickups they have screw threads for poles so I’ll need to get the calipers out to check the sizings.

The screws are the same length as the legs so you end up with some mounting issues.... Didn't fit in my RG7420 route. Almost needs to be a reverse pickup route where the leg screw holes are higher than the pickup cutout.

Pre-Owned Seymour Duncan Pegasus/Sentient 7-String Set

Pegasus/Sentient 7-String Pickup Set The Pegasus/Sentient medium output humbucker pickup set offers progressive players the ultimate palette of modern metal tones. The Pegasus bridge was originally designed for extended range instruments. However, 6 string players immediately demanded we offer a...

www.fivestarguitars.com

 

[NickK-UK]

I was just looking around at headshocks and came across this photo of mid build of the music man. It basically shows precisely the through-neck design I was planning and using the neck wood to support the pickups. You can see that route in the centre is deeper vs the outer routes being higher. Interestingly it also shows how they fit the headstock onto the neck. I note here that they use the top decal wood but then when they carve the arm relief it's also carves through that into the wood below (hence why they use the paint job to remove that feature).
Lastly the bridge - that too is embedded in the neck wood - which is the reason I'm making a thru-neck (sorry for the smart spelling it make's repeating the term easier!). That bridge to neck wood means the string at both ends is operating on the neck wood. It's also why I will make the back of the neck block towards the rear strap point be wider than the nut. The lines of the sides follow the fretboard.

Source: https://www.music-man.com/instruments/guitars/the-majesty

Not sure I like the truss rod metal next to the pickup. It does mean that any vibration in the truss rod is picked up by the neck pickup but I don't think I want that.

Playability.
In a completely different piece of thinking - it's how the arm and hand falls when playing muted on the bridge. This means there's a natural position (not far back like a bass) when the bridge would be better sitting for comfort. This has a couple of side effects - the more left the bridge goes, the longer the neck. Also to balance that longer fulcrum of a neck, the more mass on the back to ensure that the strap sits balanced. There's no point having a guitar head heavy. The use of the thru-neck means some of the neck weight also appears across the guitar. However a heavy wood at the back also rebalances the guitar.
I can do a calculation that:
* take centre line of the front strap or the guitarist's body.
* we can make a thtu-neck ratio (how much neck is on either side of the strap point) - this will be the ratio of neck weight added to the head down, the more 1:1 this is the better and more neutral the feel. This is why it's good to have the thru-neck go right to the back of the guitar (strap point on the rear). We can add a weight and then scale that using the ratio to provide a rotational force.
* we can then measure the head stock weight and the weight of the tuners and approximate distance from the strap point - that gives a rotational force we can add to this.
* We can then calculate the rear weight of the guitar (the wings and front) and use that to calculate the opposing rotational force. Add the hardware weight and fretwork weight accordingly..
We then have a rough feeling how headstock heavy it will be.

If the design needs the front strap moved forwards then we will need the bodywork to support it but at the same time we want the hand-arm-bridge angles to not shift. This may mean adding some butt wood to the design to make the back heavier.

Lots to think about in this but I don't think it will need too much as we don't have an overly light guitar body bolted to a heavy neck.

 

[NickK-UK]

You know you start out with some ideas.. then you visit the local specialist timber yard and you come back with something different that you started out with..

Hard Maple, then on top purple heart and on that Indian rosewood (confusingly on a wood floor):

Not the full set of wood but a starting point.

 

[NickK-UK]

Sorry that's African rosewood

I'm going to get some mahogany for the neck too. If the rosewood doesn't sound right (or makes my eyes go nuts with the strings vs pattern) then I may strip that off and put a black ebony fretboard on.

I was looking for a larger hand plane for levelling. At 460mm long a No6 seems to be useable vs the No7 at 560mm. Looking around as they're not really made anymore - the option was either a) Chinese mass produced bad reviews cheapie, b) Lie Nielson (~£400) quality or find a second hand/restored but straight known brand such as Stanley/Irwin/Record. So I've also bought an old Record No6 fore plane. I can get a replacement iron (blade) for that easily enough in case there's any mishaps.

I'm also going to make a ply guitar case (I have some slightly warped ply that can be brought back into true by the edge joints of the case. I can then also test the plane at the same time. After that I'll trim the wood to approximately the right length and store it in the guitar case. This will allow me to maintain the humidity level better and if needed add some drying pouches. Leaving the wood for a month or two will then allow it adjust before it gets cut further. I'll then leave the guitar in there during the construction.

I'm still designing the right shape of the body but I've roughly drawn the guitar to scale on my home office board:

This gives me the option to try ideas at the cost of a pen stroke. At the moment it looks a little too much like an SG - I think the top piece could be longer and the back piece could be a wider curve to allow raised playing when seated. Also the head will need attention with the tuners. I'm thinking of a rear jack socket rather than on the face or edge. Controls will be rotary selector switch (pull push for coil separation), volume. I'm not sure about a tone stack - I'll leave that signal processing to off board.

What I may do is print out a full sized image and then stick it to the Strat to get a feel for size when being played.

I have to say I love the shape of the music man body. I think though I will not have a painted section but may try steam bending the wood .. just to make it more complicated.

 

[NickK-UK]

I found this explanation of cuts of wood and I thought it gives one of the best explanations:


In a separate piece of thinking I've been thinking about the body design and neck-headstock for the angled headstock.

So for the neck I'll use a 'type B' scarf joint but I'm thinking adding a volute and backstrap along with a front headstock. This adds strength to the joint and also allows the nut to sit on the neck wood directly without having the glue of the scarf joint in the way as the nut sits on the full neck.

I was thinking about sitting position playing - including on the 'classical leg' and the music man/fender jazz master bottom rear lobe offers a stabilising point whilst playing in this way. The carve then allows the weight to be pushed back, offsetting and balancing for horizontal sitting positions and strapped playing.

So the design has moved on a little more.

I'm thinking that the body would probably be a cross between a music man majesty and this - specifically the carves with the carved top:

Source: the-majesty

In fact the original idea was to have a light top, dark hardware and a black fretboard. I think this will change a little. Although I like the lack of clutter - however I would use a black metal volume and rotary selector switch that push-pulls. Now in the above design I don't like the rear behind the bridge and the upper rear lobe. However I am thinking of putting the fender strat style jack recessed on the back of the guitar to remove clutter.

I did think about separating the top at the carve, as below but I'm not entirely sure as it depends heavily on the wood exposed and I find it a little Meet the Jetsons:


I think for the headstock - the shape will end up relatively plain with the backstrap and front adding some interest. If I'm using 4 top and 3 bottom tuners, the shape will be relatively symmetrical anyway but curved suits the body shape - no Les Paul style blocks of wood.

 

[CanserDYI]

Wow that video was informative, I always knew the differences between quarter sawn/rift sawn/flat sawn wood, but I had no idea that flame maple and quilted maple were just different cuts of the same wood, I thought it was just a luck of the find when you opened up the wood, whether it was quilty or flamey. Cool.

 

[NickK-UK]

So I've been preparing a little as it's all coming together nicely.

I bought a No6 Fore Plane, dated to about late 1970s it's almost as ancient as myself but it really works nicely. Especially when given a little wax. The work bench is way flatter than this morning I have a set of replacement my hand-me-down bandsaw components (the rubber around the wheels had perished, so too had the drive belt). That's going to be with me by Tuesday. The late father in law would be proud being a bit of wood worker himself.

The backorder hardware should be with me by next weekend (tuners, bridge and pickups).

I'm still eyeing up some additional woods - mahogany for example but I can't get to the place during the week (grr) when they're open and I want to see it before buying..

I'm going to pop along to a local woodworking place and pickup a few things - sharpening stones, Japanese saw, some additional clamps, and then I'm about ready to start the basic neck gluing up.

 

[dmlinger]

Enjoy the process. You'll learn the most once you start making wood chips and mistakes.

 

[NickK-UK]

The case has been cut and is currently gluing up.. it should be large enough for a 43" x 16" x 4" thick guitar with padding. All out of 12mm baltic 9 ply. I'll use that in its raw form to store the wood once cut to rough sizes. There will be a couple of steps when I think I will wait for a week where the pieces can sit in the case safe and sound - specifically when cutting the laminates to rough size, then after a wait for any relaxation bends, that a final small amount of cutting should have a smaller change.

So I've been thinking through the steps, in which steps require previous steps:

I've found a possible place that has a thicknesses and router table etc that could help shape/square the longer pieces. Only thing is they have some limits in sizes, hence I need to work out the stock sizes - on the good side is that laminate necks mean smaller cross sections.

Also looking at finalising the sizings - I need these for the rough sizings (my replacement band saw tyres should arrive soon).

So, with a 7 string my thinking about the dimensions:

Nut width and bridge width.
So this one I'm considering a wider string spacing. I have large hands and as I get older getting fingers to hit strings will become harder hence a slightly wider spacing may be better. For reference I have 6 string strat with an ~43mm means I can bar with the top part of my index finger (intermediate phalanges and tip) across it and it feels a little like a kids toy.
Hence with the 7 string I'm thinking of increasing that to around 50mm. The music man is about 47mm so around this make sense.

Ohh... and this just arrived:

Gives me chance to measure some of the components for real - without the inaccurate data sheets (GOTOH!) and missing measurements (GOTOH and SD!).

 

[NickK-UK]

So my attention is now on the nut. It looks like I have two options:
* Graph Tech PT-5700-00 which is a 53mm wide 7 string but has the strat curve base.
* Graph Tech PT-4025-00 which is 63mm wide blank that will need slots cut.

Now just thinking a little on intonation, that should be relatively straight initially but another option is to find a 7 string compensated nut. Now I have access to a scope, signal generator and a -150dB ADC, so I could use that on the finished guitar to adjust the nut and bridge to get proper intonation. So I'm starting to think the better option is get a blank and use that with a set of files.

I think a string spacing of 7.9 or 8mm at the nut. Which gives an end string-string spacing of 47.9 and so a ~53mm nut seems about right with room for the fretboard.

The bridge end of the fretboard is likely to be ~66mm wide at f24. Which gives 1.5mm either side of the strings. Now here comes the fun bit - if I want the pickups to sit attached to the neck laminate (ie the screws go into the neck laminate itself and not the body wing) then I will need about 90mm width. One option is to splay the neck laminate(s) out which complicates things a little but could be doable. Another option is to parallel the neck but then use wider outer laminate that is cut back at the neck itself but leaves the extra width in the body.

Lastly 45mm body width seems normal and my strat is that too.. so that would probably be a 30mm body thickness with a 20mm decorative top carved in. Or a simple flat top of bare laminate at 45mm.

I've also measured the bridge, pickups and tuners. There's a number of missing measurements that you need such as 2.7mm for the minimum and maximum bridge elevation (note that the lowest would need shorter screws as the stock ones stick out of the top).. also there's 2mm under the pickup mounting point needed for the pole screws.

My intention is to hard mount the pickups. If lift is required after fitting I will use shims of hard maple etc to boost. No springs and no faceplates. That should fit in the 45mm...

Naturally the body carves at the front for the arm may be an issue but at the same time I'm not too worried to carve that a little thinner. The arm carve on a fender is only about 5/8th (1/2 in) in depth.. so that's basically 12.5mm. If the top is 20mm that's fine but I will need to be careful of chip out.

 

[Asdrael]

Regarding a router table: a hand held router with decent templates will do as good a job. You can buy a very good one that has up to 12mm collet size new for 200€ from Triton.

As for the nut, sanding a nut base flat and adding a (wood) shim is really easy so that should not deter you from buying a preslotted nut. Another option for a nut is the "Graphtec Schecter" https://graphtech.com/products/black-tusq-xl-schecter-7-str-nut-48-x-6-pt-6748-00 . It's 48mm wide though.

 

[NickK-UK]

Regarding a router table: a hand held router with decent templates will do as good a job. You can buy a very good one that has up to 12mm collet size new for 200€ from Triton.

I’m considering the print paper, master shape onto plastic then route.
I’ve made some calculations and the sizes may actually fit a router attached to a table - allowing router+fence to thickness. I’d prefer £200 on a table if this works.

My approach to wood joints is simple - if you can’t hold the joint together without gaps with fingers, then it needs more work.

As for the nut, sanding a nut base flat and adding a (wood) shim is really easy so that should not deter you from buying a preslotted nut. Another option for a nut is the "Graphtec Schecter" https://graphtech.com/products/black-tusq-xl-schecter-7-str-nut-48-x-6-pt-6748-00 . It's 48mm wide though.

Yup that would also save on the cost for a set of files.

 

[Asdrael]

Yup that would also save on the cost for a set of files.

Only if you have the same fretboard radius, which is I believe 16.

For plans: Where are you located? In Europe at least, getting a DXF laser cut for a template is easy and cheap. Head towards guitarsandwoods I got a complete guitar template on 8mm acrylic for 65€ there.