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My Math Isn't Working. Need Help With It.


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Ok, been planning my neck build and ran into some problems.

I bought this template for my first build

Jem Template

I also had bought a Floyd Rose Tremolo from allparts with the 1 5/8" locking nut. This tremolo has a 2 1/4 string spread.

Research I have done.

I have determined that the template is designed for the following:

648mm Scale length (25.5 in)

43 mm Nut (1 11/16) First Problem

57mm width at 24th Fret ( 2 1/4)

This is the basic Jem neck. Had to go to Jemsite for the different specs & compare to the template.

I have Both Melvyn Hiscock & Martin Koch books

Taking the equation from Martin Koch's book on determining length of the fretboard, I rearranged it to solve for bridge spread. I did this to determine if the bridge spread on my Floyd will work.

If this string spread will work, then I have 2 options....

1. buy a new 1 11/16" locking nut or

2. Skip using the template and build the neck according to the pieces I have.

Ok I rearranged the equation like this:

B = (X-a-2d)(S/L)-a

Where:

B= Bridge string spread

X= Fretboard width

a= Nut Width

d= Distance from outer strings to edge of fretboard

S=Scale Length

But using the following numbers, I end up with a negative string spread.

a=43mm (1 11/16)

S=648mm (25 1/2)

d=3.2mm (1/8)

X=57mm (at 24th fret) (2 1/4)

L=486mm (at 24th fret) (19 1/8)

I know I am missing something obvious but for the life of me I can't figure it out.

Well hopefully someone stayed awake through all of that and can help me out. Thank you in advance.

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Skip using the template and build the neck according to the pieces I have.

If you're going to go through the trouble of building your own neck, I would think that you should get the parts to make it like you want rather than let the parts dictate how your neck will be made. Just my 2 cents.

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I've decided to make this neck to fit the nut & tremolo I already have. It's brand new and not going to let it just sit.

Part of the reason I want to know about the string spread, is that next time I order one, I can order it with the right nut and will be able to use that template then. Will be less I have to calculate to make the neck then.

Also, the math thing is bugging me now. I'm still trying to figure out what I did wrong. I would think that simply rearranging the equation would have worked. I'm thinking it has to do with distance from the nut but haven't worked it all out yet.

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But using the following numbers, I end up with a negative string spread. 

a=43mm (1 11/16)

S=648mm (25 1/2)

d=3.2mm (1/8)

X=57mm (at 24th fret) (2 1/4)

L=486mm (at 24th fret) (19 1/8)

Helllo wolfcoast,

In Koch's book in the tables of fret distances, 24th fret (L in the equation) is 405.09 mm for 647.7mm (25.5") scale length. Plug that figure in and see what happens.

I'm not quite sure why it's that number. 24th fret should be half way between the 12 and the bridge, shouldn't it? Which would make it the 486mm you used?

Anyone got an explanation for the discrepancy?

brian d.

Edited by brian d
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But using the following numbers, I end up with a negative string spread. 

a=43mm (1 11/16)

S=648mm (25 1/2)

d=3.2mm (1/8)

X=57mm (at 24th fret) (2 1/4)

L=486mm (at 24th fret) (19 1/8)

Helllo wolfcoast,

In Koch's book in the tables of fret distances, 24th fret (L in the equation) is 405.09 mm for 647.7mm (25.5") scale length. Plug that figure in and see what happens.

I'm not quite sure why it's that number. 24th fret should be half way between the 12 and the bridge, shouldn't it? Which would make it the 486mm you used?

Anyone got an explanation for the discrepancy?

brian d.

Brian,

Take another look at the page. The numbers on the very left of the page are NOT the fret numbers. I looked it up after you said that and made the same mistake at first. Column A contains the correct fret numbers and they match with mine. hehe.

Guitarfrenzy,

Yes that helped a lot. I came out with needing a 2 1/8" (54 mm) bridge string spread to use that nut with my neck template. As my floyd has a spread of 2 1/4" (57 mm) I can't use the template.

Hmm another wierd question. Using Guitarfrenzy's equation with the 1 11/16" nut, I come out with needing a 2.11" string spread (basically the same as above). so that would mean even with the correct nut, I wouldn't be able to use this floyd as the spread is too big. I know Jem's normally use floyd rose style lowpros. Don't all floyd's have roughly the same string spread?

Shouldn't that be "+a"? I am a mechanic, not a math person. But I rock

OMG you are correct. Somehow I switched that around. I told you it was probably something simple. Funny thing is, I wrote it correct on the paper as I was rearranging it. At the end I made it negative for some unknown reason LOL. Thanx. gonna do some recalculations now.

Edited by wolfcoast
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well my first thought, were u getting a reasonable string spacing, just negative?, if so u havent followed basic algebra, if u take somthign across the = sign then u a swap the sign, eg: -a on one side would go to +a on the other,

thats todays maths lesson kiddies, tomorrows lesson will be on finding the equations for an elipse in parametric form B) (seriously i bet noone can tell me this)

luke

:D:D

edit: i can do maths but i sure as hell cant spell.

Edited by where's the beef???
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Here is a simple method that works really good. Give it a whirrel if you don't trust the math.

Draw it full scale on a 3.5" wide piece of MDF. Start by drawing a center line lengthwise. Then add a nut line at one end. Measure to you scale length and put another line. You know the nut and string centers at the bridge. Now mark lines on center at the nut end 1 5/8" apart which is your nut width. Then at the bridge end draw the center of the 2 E strings and mark. Add 1/8" to each side and mark, they should be 2 1/2" apart. Draw a straight line from the outside nut marks, to the outside bridge marks (2 1/2"). This will be your taper. Now put a perpendicular line where the last fret and end of fingerboard will be. Now you can cut out the template and it will have the correct taper.

Another thing, if the neck template you have already is for a Floyd Rose width heel already, you can just make the nut area narrower by 1/32" on each side. The resulting difference in taper is so insigificant that it means almost nothing overall.

Hope that helps some.

-Doug

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Well the template should be made for a floyd rose as it's a Jem template. IIRC most 777s came with a floyd rose lopro. I'm sure that the string spread from a lopro to a nomal one should be the same....

I would use MDF for the template except for one thing... I can't get MDF in guam. I went to ACE hardware lumber area and asked for it. I got some serious "deer in a headlight" looks. They had no clue what it even was. God I miss Home Depot.

I do have some 1/2" oak plywood I might be able to use. Will have to make sure the sides are cleaned up after I cut it.

I might take a stab at using the template. If it's only a difference of 1/32 on each side it should be usable. If not, I can just make another template.

Thank you for all your help guys.

BTW.. what does it take to get rid of the new member thing? LOL I've been here for over a year & a half. Granted I don't post that often but still hehe.

Edited by wolfcoast
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Alternatively you could make a 15" sanding block and carefully sand off the extra 1/32" because it won't take but a couple strokes with 100 grit abrasive. The reason for the long block is to keep the sides straight. Besides I found a 15" block to be good for a lot more uses than I ever though it would be.

That plywood is fine. Anything stiff should work.

-Doug

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or you can post more to become a forum regular :D

and wolfcoast by any chance is the floyd made by a company called Takeuchi? if it you would honestly be better to take it back get a refund or store credit, id spend the extra bit and get a decent floyd or a decent liscenced copy, assuming it is takeuchi as it is a pile of sh** i have one and i do not rate it to high but im stuck with it as i bought it along time ago, the bar got stuck in it, so i took it all apart, the nut that goes round the bar is all loose and wobbly- its like a sort of rivet, on the saddles the i noticed the underside bit which stops the hardened steel block from falling through is starting to snap of. maybe its just mine but if i were you and its made by takeuchi i would check it, bear in mind mine has never been put on a guitar.

sorry if ive gone slightly of topic. good luck with your guitar :D

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Whersthebeef, his negative answer was still wrong because it had the string-from-edge spacing subtracted as well. You learn a little of this exact stuf doing a four-wheel alignment on a car even with the stupid preprogrammed laser Bear systems. When a car has modified suspension or wheels you have to do it the old way or it will dogwalk left or right. Very hard on tires. New tires ROCK! :D

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Yes, the floyd I have is a Takeuchi model. I bought it from Allparts. Had a limited budget to work with when I bought the original materials/tools for building my guitar so had to go with a cheaper model. I bought it over 6 months ago so I doubt I could send it back anyways. I will use it at least for practice installing a Floyd.

I haven't actually built the neck yet so no errors to correct yet. Plan on doing the next over the next 3 or 4 days as I get time. I'm hoping this week to get the fretboard frets cut, fretboard inlay done, cut the neck & install the fretboard. We'll see how far I can get. Need to blow the dust off the digital camera and start taking some in progress pics.

Wheresthebeef: No the numbers came out wrong because I somehow reversed the sign of a. Strange because I wrote it down right on paper all the way to the end LOL.

Thanx for all the help guys. Hopefully will start a thread in the Work In Progress section here soon.

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