Four string fretless acoustic/electric (chambered)

[Jisch]

I got some time in the shop today.

I routed out the truss rod pocket - I'm putting the adjusting nut at the base of the neck, I've never done that before, but it seems ok so far (apologies for the non-standard footwear):

I used a router to set the edges on the neck, just a board taped to the neck wood:

with the router cuts on both sides:

and finally I cut the pieces for the front so they match up. My thought here is to leave a gap between the individual pieces and fill it in with either a piece of anigre on edge or more likely with ebony dust mixed with glue. I have mixed feelings about how this came out, my thought was to match it up perfectly, but the grain between the pieces is not close enough to look like one piece of wood. My dad suggested that with a black filled gap it will look like a cracked piece of wood, which will contribute to the look.

Next I'll work on the neck dimensions - I need to think about it a bit before the next steps, but today was a great day in the shop, I felt like I made process.

 

[pnchad]

I had a fretless 6 string built by Ken Bebennsee - I think it was crotch walnut where he left 2 wandering holes upper & lower body areas -.it was NT though chambered above & below the stringers thru the body

 

[Jisch]

This is my first non-NT bass, it's a bit unnerving, but so far so good.

 

[daveman50]

I have mixed feelings about how this came out

No way. It's fantastic.

 

[Jisch]

I just tried out the anigre and it works great in the gap if I stand it on end. I'm going to use that, it will leave a nice even gap as a crack. hmmm just typing that - do I want an even gap, or should it be variable like a real crack? I'll sleep on it.

 

[Rôckhewer]

I vote for variable. If it is even...you have organic shaped lines doing a non organic thing.
If it were me I would tighten them up a little bit too.

And if you wouldn't mind another suggestion... It looks to me like you might want to bring the inside curve of the lower horn out a bit, because you might want a bit more clearance to reach the high end of the neck....??
just my opinion though.
That's going to be a cool top!

 

[Jisch]

Thanks. I know you can't tell from that picture, but they are pretty close to perfect if i push them together. Variable probably makes more sense.

The shape isn't at all final, I always cut everything as big as possible, then I'll cut it to accentuate the flow of the grain in the wood. I am trying to keep this body on the small side though, all my basses end up being huge.

 

[Jisch]

I got a little more time in the shop.

First up - cut off the bottom end of the neck and finished off the truss rod install:

I rough cut the fingerboard:

And I made a bunch of sawdust to fill in those cracks:

I need to think about how I am going to glue up that front, it's going to be tricky. I need to have wood underneath the joints, I'll need to do the fill in at the same time as the glue up and I have to keep it all flat. Something to think about next time I can't sleep.

 

[Will_White]

I got a little more time in the shop.

First up - cut off the bottom end of the neck and finished off the truss rod install:

I rough cut the fingerboard:

And I made a bunch of sawdust to fill in those cracks:

I need to think about how I am going to glue up that front, it's going to be tricky. I need to have wood underneath the joints, I'll need to do the fill in at the same time as the glue up and I have to keep it all flat. Something to think about next time I can't sleep.

If it is smooth enough, a veneer between the pieces would be easier.

 

[Jisch]

I think I need something more significant under the top than veneer. I have some black veneer, but I think that would be entirely too flexible. I cut some pieces of the end of the top wood and I think I'm going to glue those under the seam. The one bad thing here is I need the top to vibrate to some degree, so I don't want to add too much mass. The top wood is a bit over 1/8" now, and pretty dense.

This is what I'm thinking (comments welcomed and appreciated!)

 

[Jonny5bass]

Just spit ballin' here but what if you did a little more traditional acoustic bracing and used some dams to fill in the glue between the top pieces.

 

[Jisch]

Having never done anything like this I'm spit balling here too. I think I need to support that gap with something underneath to provide more surface for the glue. I think if I just put glue in between with a dam it wouldn't be very strong, and while the bridging would make it stronger, it's not going to support those gaps enough.

 

[wraub]

Veneer/glue to fill the cracks, and full width spars running across the seams?

 

[Jisch]

Hmm. I wonder if I could get away without anything under the seams. Maybe bracing all the way across would work. I suppose if I did the glue/veneer to fill the gap first, I could then add either bracing underneath the seam or just do regular acoustic bracing if that seemed like it would work. It's a good approach because I can just add as little extra mass as I need to.

 

[Will_White]

Hmm. I wonder if I could get away without anything under the seams. Maybe bracing all the way across would work. I suppose if I did the glue/veneer to fill the gap first, I could then add either bracing underneath the seam or just do regular acoustic bracing if that seemed like it would work. It's a good approach because I can just add as little extra mass as I need to.

An x brace could support a lot of the gap.

 

[Jisch]

I'm made a test piece today to see if just filling the gap with veneer, sawdust and glue will yield a joint strong enough to work with. I just need the joint to hold until I can get bracing behind it. I think it should work. After thinking about all the suggestions here, I think cross bracing should be enough. I just hope the joint doesn't crack or something down the road.

I don't think I used enough glue, but this is test case #1:

 

[Jisch]

A guy I know makes acoustic guitars and I was talking to him about this project - he has no experience with electrics.

He suggested making the joint between the two pieces of wood tight (i.e. you can't see light through it anywhere) then joining them directly. If I wanted to add an accent stripe I would do it as an inlay with a pin router bit in a dremel, then do standard X bracing underneath. This would yield the strongest joint. It will take a couple of hours to make the joint this tight, but I've done it before with another bass, it just takes a lot of patience. He said adding the pieces to the back (like in that picture up there) is a bad idea as it will add too much mass to the top.

This would probably mean I'd be going with a single stripe of black that has a consistent width.

 

[Jisch]

It seems like I'm doing a near stream of conscious kind of posting here, I apologize for wasting the electrons. I do appreciate all the comments so far and it really is helping with my decision process, even if it seems a bit schizophrenic right now.

So to continue on this waffling pattern: I pulled the wood I glued this morning out of the clamps and sanded it semi-flat. The glue is supposed to take 12 hours or whatever to dry, but I was impatient to see what it looked like sanded. It looks great and feels really strong. I'll let it cure overnight before trying to break it in half to test strength, but, despite what my acoustic building friend suggests, I think this is the way I am going to go (for the next five minutes, until I post again).

 

[Jisch]

This didn't work out as well as I had hoped, but I think it will be ok. I got some good glue squeeze out, but I was hoping for more. Oh well. I'll have to think sticky thoughts tonight.

 

[Jisch]

The glue up appears to have gone well. I block sanded it down to at least get a look at it, I'll hit it with the orbital sander later on and get rid of the rest of the glue/sawdust. It looks great and feels plenty strong enough. With the X-bracing underneath this will be fine as a top. I know the picture makes it look messy because of the glue and the stuck in sawdust, but it will be a clean line when I'm done. I'm pretty happy with it!

Now I can get on with the rest of the body work. I have two mahogany slabs, I picked out the best one for this shape and will start on that as soon as I get the chance. I think I can screw the top onto the mahogany while I work on shaping it by putting screws in where the strings will go through and into the neck pocket area.

I always use the grain of the wood as a guide for shaping the body. I start with a general idea of what the body will look like, but the end result is never what I start with. I know right away that the lower horn needs to be further out or thinner and the upper horn needs to be longer than this to prevent neck dive. I know this body will be super light, so it's really important that strap button is at the 12th fret, if possible. I have very little extra material to work with in this case, but I think it will work out.

My next concern is the placement of the transducers for the pickup, the instructions are pretty prescriptive about where exactly you place them - one between the 1st and 2nd string and one between the 3rd and 4th string right under the bridge, so before I glue the top onto the body, I have to have the bridge location figured out. I'm planning on having the strings go through the body using ferrules in the back, then building a bridge out of wood. I plan on setting the intonation by carving individual string saddles. Perhaps a bit ambitious. We shall see.