Trussed up

The purpose of the truss rod is to keep the neck from bending forwards excessively once the strings are pulling on it. The neck profile and width are not constant and being able to predict how much it bends along its length is not something easily worked out (well not by me, anyway).

Perhaps I'll just have to fit something and hope. It shall therefore be known as a Trust Rod system. Rickenbacker use two (Rod and Jane?) and I am sure somebody out there has tried three (Rod, Jane and Freddy). Maybe not...

I've had guitars before that have a mysterious rattle from inside the neck on a particular note. It doesn't seem to get to the pickups directly, but it makes the note quieter or lose sustain quicker. To avoid this, I am shying away from a double action Trust Rod and instead going for the traditional bar in a curved channel version. This gives me the option of fine tuning its response to some extent and no other metallic parts for Rod to clang against.

The worst case scenario I can think of is a neck that bows forward with one curve, and a truss rod system that compensates for a different curve. The difference between these could result in a neck that cannot be adjusted flat, it will always have some sort of buckle in the middle.




To get around this I managed to get Chris at work to assist me with a simple finite element stress analysis model of a typical neck profile. String tension was added to see what happens in use. I don't know how to use mechanical CAD systems so I just directed from afar.



Measurements of deformation were taken at 20mm intervals and entered into a spreadsheet which could then be analysed to see if any sense could be made from it all.

With my approximate Jazz bass neck profile, the deformation was remarkably similar to a square law. This meant to me that for every 20mm step along its length it had curved by the same amount as the previous 20mm. A quick surf brought up the Engineering Fundamentals site which shows that for a constant cross section (ie a plank) the deformation is a cube law.

Hmm - been dazed and confused for so long its not true, wanted a straight neck, never bargained for you.

I'm still thinking there's a lot more to truss roddage than meets the allen key, but for now I think a single radius channel is the place to start. Over a 600mm ish length I am going for a peak curve of 6mm, which is a radius of around 7.5m.

I don't know why, but I feel that if I can put a mild downwards slope with this curved channel as it heads towards the body, it can only help negate the effect of the strings.

Trust Rod! Don't trust Jane or Freddy.

Plane Sailing

The neck laminates are all stuck together so it is time to clean them up a bit and see how it looks. I used a smallish (10") plane which is good for getting the surface smooth. I also splashed out on a longer plane (22") which is better at keeping the surface as flat as is possible.

Being hardwood, it all takes more work than I would like. One of the side effects of planing is that the edges form really good sharp corners. Rubbing hands down the freshly planed surface to is not recommended, I managed to get an evil splinter from the wenge. It hasn't come out yet - it seems to have barbs on it! Be warned...

I chose the most suitable side for the front and set about cutting the head angle at one end. This was also planed smooth and allows me to easily tell which way round the neck is. I used a fairly modest angle of 8deg.

During this time I also offered to repair a bass with a snapped truss rod. My mate Chewie used to play bass back in the days of Head Cleaner and after several years the trusty old Ibanez 2354LB went "boink" and the neck turned into a banana. For some time the bass has been no more than an ornament, but now, if all goes to plan, can possibly enter a new phase of debananarisation.

The repair work had to be carried out on a realistic budget as in good fettle the bass is probably not worth a great deal. The googleit approach gave a few different options to try: heat, acetone, water, powertools.

The acetone method was favoured as it loosened the nut successfully and promised the least amount of actual work. We stood the neck up and kept pouring acetone into the truss rod slot at the top, but after an hour there was still no sign of the fingerboard releasing. The paint finish was responding unfortunately...

A small amount of the adhesive was scraped off and soaked in water. Nothing. It was then dried out and put into an oven at 150degC. Nothing. The glue must be the same as the wallpaper paste

NASA used inside the shuttle!

Out came the Dremel with a mini circular saw cutting between the edge of the fingerboard and the neck. This was then finished off with a hacksaw and then I was in like Flynn.

Sure enough the truss rod had gone due to a combination of shearing and rust. I expect Newcastle Brown Ale was to blame for both.

Stick With It

The laminates are ready to be stuck together. I have cut some veneer strips to rough size and have drilled holes at the extreme ends so that all the parts should go together properly without slipping about like a really slippery thing wearing slippers and coated in slippery stuff. There are several different layers, but I don't think I can glue, assemble and clamp all of them in one hit, so I will separate them out. Here's the first lot - notice all the clamps that I managed to borrow!

I am using titebond - a sort of PVA based glue. I gave it 6-8hrs to dry before I took the clamps off and sandwiched another layer on. It does get a bit messy - but thats part of the fun...

Fat Neck, Thin Neck

The centre neck laminate is an inch thick. In the body that's great, but as the neck tapers towards the head, there won't be much of any other wood, losing any advantage that laminating may have had. My plan is to taper this centre plank down in sympathy with the neck taper so that I get more wenge where my left hand is going to be! Keeping a taper constant over 4ft sounds like craftsmanship, so I need to find a way of cheating.

Fortunately I had a few steel box sections loafing about in the garage of the right sort of length so I managed to bolt them together to create a bed for the wood to sit on. The sides were angled and all I had to do then was plane the wood level with the steel box sections on either side.

I made a lot of sawdust! The finished article seemed to have a pretty constant taper - the job's a good'un. The blade in the plane got a bit chipped on the corner as I got down to the steel. I might have to fix that one day.

Moon Bass Alpha - Planning The Mission

Moon Bass Alpha - I know its a silly name, and I'm unlikely to play bass on the moon, but I could have spent months thinking of something else instead of actually getting down to the, er, wood and two nails. Some people have heard my playing and think that the moon is probably not such a bad idea.

Sticking My Neck Out

I believe that the neck wood must contribute more to the overall sound than the body wood, as the neck is flimsy and will vibrate and bend when a note is played, whereas the body will barely move at all. The neck also covers more than half the scale length so I think that choosing the wood for the neck will dictate how the 'wood' part of it sounds.

Most guitars I have seen seem to have maple necks. My own guitars have maple necks, or at least maple and something. Having said that, I am pretty sure my Peavey Cirrus BXP is made from Obeche. It is as light as a feather (in comparison to the Vigier). But anyway, I wanted something to sound different so I have made my first bad decision and ruled that maple is not going to be used on Moon Bass Alpha.

Great! Out goes maple, in comes, um, balsa?

Paper. Books and libraries and t'internet. I have invested in "Make Your Own Electric Guitar" by Melvyn Hiscock and it seems very helpful. Other books on 'What has wood ever done for me' etc have been dribbled on in the pusuit of knowledge. I noticed that some guitars (particularly Warwick) have used Wenge necks in the past. The local timber merchant seemed to think it was the sort of wood you would use in a dockyard, but it appealed for a number of reasons: 1 - it isn't maple; 2 - it is a very dark brown colour unlike maple; and 3 - it has a coarse grain structure which ought to help create a fuller, more mellow tone and growl.

Unfortunately I like laminated necks. The stripey-through-the-body look does it for me. I need another wood type for the neck. After contacting craft-supplies.co.uk (who do wenge laminates) the choice narrowed down to Bubinga and Padauk. I have gone for the Padauk because: 1 - Padauk is a really nice red colour; 2 - It is reasonably good to work with; and 3 - I am not quite sure how to say Bubinga without it sounding stupid.

A few layers of contrasting white oak veneer from valeveneers.co.uk (keeping to the no maple rule) and the neck layer build up is as follows:

WOPWOPOWPOW

It reminds me of watching Batman on a Saturday morning, but what it meant was W = Wenge (1/2"), O = Oak (0.6mm) and P = Padauk (1/4", except centre which is 1")

Here's the wood as it turned up. W x4, P x3 and an ebony fingerboard. Ebony is about as non-maple as you can get! Don't get me wrong about maple - I like the syrup, but I just want something a bit different in the neck department.

New Year 2008.






Last year I decided to make an analogue synth. A bit of research into how it used to be done before the world went horribly digital and the circuits were formed. It is great for sound effects and has nicely drifting oscillators that beat, filters that squeal, modulator with breakthrough... fantastic!

It was reasonably straightforward to build, as it just had to sound OK, and looks were way down the list. Thanks to Bob Moog for a heavily borrowed VCO and VCF, but the ADSR circuit was all my own work, and the remainder was fairly standard circuitry.

I sold my old Hohner Arbor Bass Guitar recently. I sold it to a guitarist in a local band who had built his own guitar. It got me thinking about its replacement. I thought short and soft about what I want from a bass. It isn't out there (not in my price range) so I think I'll just have to follow his footsteps and do it myself. Woodwork is quite a different ball game from electronics though...