Sporkaster 2 rebuild

Sporky

I made Sporkaster 2 on a course; it's a 7-string JM style guitar with a Sustainiac. It has a few problems though.

1) the intonation is off - originally due to incorrect measurements from Hipshot
2) bodged repair attempt (not mine) means there's an ugly bit of plastic on the front by the bridge and the trem binds

So the plan is to make a new body for the existing neck, and move all the hardware and electronics over.

It will either be another JM style (less work and I can keep the scratch plate) or a Musiclander shape, as I've long had a hankering for one of those.

I have a few body blanks and tops knocking about that I bought from @Paul_C some years ago, so it'll likely be alder core with a spalt front and back. There may well be chambers.

Sporky

This is SP2, before the bodge.

http://www.monkeyfx.co.uk/pictures/sporkaster2/IMG_1837.jpg

Winny_Pooh

The original looked great, needs a matching headstock though. Does spalt mean you're aiming for a natural finish?

Sporky

If I do go spalt then it'll be either a trans finish or natural with a tight black burst around the edges.

Sporky

So far I've drawn up a load of candidate body shapes in CAD, including a near-trace of the Line6 Shuriken (as it occurred to me that that's not far off what I'm going for).

While I fail to make a decision on that I need to disassemble the existing body to measure the neck pocket - I'll do a mock up of it in a bit of scrap to check dimensions; in the original the neck pocket was routed using two straight edges, but that'll be hard to do now the back is carved. In the past I've managed a good fit by a bit of measurement and having the CNC machine rout it.

Sporky

I made minor progress today. Took SP2 apart, measured the neck pocket and pickup cavities. Next stage is to CAD the neck pocket and machine a test.

I think I'm going to go Jazzmaster style again so I can reuse the scratchplate - it's a lot more complex under there than I'd remembered.

Sporky

I made progress. CAD of the neck pocket checked again the original. Next I'll do a test machining on some scrap. 

Sporky

Blimey. It worked. Almost an exact match for the original. I'd like it a little tighter which is dead easy now. Then time to lay out all the cavities , and then choose a body shape.

Sporky

So. Body shape chosen - a bit like Sporkbasster1, but with a longer top horn. I've also played around and come up with what i think is a reasonably successful scratchplate design. Next I'll plot the cavities, then work out the elbow carve and tummy/thigh cuts, then it'll be time to throw a piece of timber into the CNC machine and see if it throws it back at me.

http://www.monkeyfx.co.uk/pictures/builds/sp2v2/sp2v2.JPG

Sporky

I was going to do all the cavity plotting but then Sprocket decided to have a nap behind my chair and I didn't like to disturb her, so I'll go and grab the current scratchplate in a mo so it is at least to hand next time. Also a new battery for my verniers.

I did tweak the scratchplate shape a bit - the bit where the volume/tone controls are looked a bit blobby/knobby to me. Rhino3D has an awful lot of useful tools but none of them are "make this look less like a knob" so please don't laugh at me when I say this took several hours. I finally realised that the right thing to do was to copy the curves, so the tip at the lower horn now has the same geometry as the tip at the controls, and the curve over the top.

I also need to measure the heel on the current neck to make sure it'll fit reasonably well into the pocket, but that's the work of a few seconds with a ruler.

http://www.monkeyfx.co.uk/pictures/builds/sp2v2/sp2v2-1.JPG

Sporky

I should probably run a spot-the-difference compo for those, looking back at them. 

UnclePsychosis

Looking good Sporks. Keep the updates coming! 

Sporky

85mm heel length. I forgot to write it down, but if I post it here I can find it later. 

Sporky

Right. Not a bad few hours; I'd only allowed 73mm of heel length so had to redraw the scratchplate again.

Next job is to lay the cavities out. I have a "standard" way of doing this; first take the scratchplate outline and offset it 6mm inwards, then draw a 12mm diameter circle around each scratchplate screw point (so there's plenty of wood supporting the screws and scratchplate.

You can see the result of that here in pink:

http://www.monkeyfx.co.uk/pictures/builds/sp2v2/cavity planning.JPG

Also drew the scratchplate holes for the pots and switch at the correct size, and drew circles around them large enough to accommodate the wiring and suchlike.

Below that are some sketches of the pickup coils (in white), the cavities they need (in pink), and the Sustainiac PCB (in aqua).

So next I move the pickup stuff and PCB outline onto the main plan so I can see if there'll be enough space.

http://www.monkeyfx.co.uk/pictures/builds/sp2v2/positioned.JPG

And then extract just the stuff that affects the cavity shape to a new layer:

http://www.monkeyfx.co.uk/pictures/builds/sp2v2/cavity geometry.JPG

Then by drawing lines between the bits I need and the bits I don't I come up with a combined shape for the cavity:

http://www.monkeyfx.co.uk/pictures/builds/sp2v2/cavity done.JPG

Overlay that back onto the body and you can see that there'll be plenty of room for wiring (the Sustainiac has a lot), but still plenty of wood left.

http://www.monkeyfx.co.uk/pictures/builds/sp2v2/overlaid.JPG

Next I'll work out the depth needed for each area - don't want to have this clash with the trem spring cavity - then plot the forearm and belly carves, then the jack socket and battery box. This might seem like a lot of faff, but it means that the body can be machined in just a few passes with a handful of tools.

Sporky

Having made a lovely combined cavity the next step is to split it into bits. So I did. And wrote on how deep each needs to be, ready for starting the toolpath calculation phase.

http://www.monkeyfx.co.uk/pictures/builds/sp2v2/cavities split.JPG

Also added the cavity for the battery box and the one for the jack socket, which will be a Strat style plate but on the back of the guitar.

Sporky

I've done the toland for everything but the belly carve and forearm contour. Mostly because I've forgotten how to do them. It'll probably come back to me.