Winter Build-Off 2022: Bamboo EUB

[RichterScale]

That's awesome

 

[Beej]

The bad news is that it now bottoms out on the end of the neck tenon and needs a stupid number of shims to make contact on the shoulders as it should.
View attachment 4834878
But the good news is that there are an equal number of shims all around, so it's pretty square. I don't really want to cut the mortise any deeper or cut the tenon any shorter, so I think the solution is the end of the body is going to get a veneer equal in thickness to the shims. That will also hide the end of the body plywood. I'm kind of tempted to bind the edges all around, but at this point I'd also kind of like to just be done with it.

If you hadn't said anything, I'd have assumed it was an intentional gap to fit a cap veneer in there to hide the plywood. This build totally would have killed in the build off.

That's awesome

Quoted for emphasis.

 

[Max Bogosity]

If you hadn't said anything, I'd have assumed it was an intentional gap to fit a cap veneer in there to hide the plywood. This build totally would have killed in the build off.

I'm going to leave doing one last thing, like cutting the slots in the nut, until this year's WBO. Then I'll submit it as a partial build on the second day and clean up.

 

[Crawforde]

Veneering the end sounds like a great idea.
You had planned to do that anyway didn’t you?
Nice little plane. I had one for a long time, polished and sharpened it and then stuck it in a drawer. Amazingly useful once I decided to play with it.

 

[Reedt2000]

Yeah man, it looks great

I especially like the offset cuts of the tailpiece and end of the fingerboard

 

[Max Bogosity]

Veneering the end sounds like a great idea.
You had planned to do that anyway didn’t you?
Nice little plane. I had one for a long time, polished and sharpened it and then stuck it in a drawer. Amazingly useful once I decided to play with it.

Well I planned it all along NOW. That little plane is a bit tricky to adjust and hard to hold because it's so small, but it can do things other planes can't.

I especially like the offset cuts of the tailpiece and end of the fingerboard

Thanks! That didn't occur to me until late. I had used a cardboard template to mark the curve on the tailpiece, so I just flipped it over and traced the same curve on the fingerboard.

 

[Crawforde]

On my current build I cut an undersized mortise into the block before glue up. I did this on the guitar I’m building and it made the final fitting easier as instead of trying to remove a lot of material I was just opening it up and setting the angle as I cut to fit the tenon.
it seemed like it made the job easier on the violin sized body to trial and error and fine tune a tight fit. I hope it works on the bigger bass as well.

 

[Max Bogosity]

On my current build I cut an undersized mortise into the block before glue up. I did this on the guitar I’m building and it made the final fitting easier as instead of trying to remove a lot of material I was just opening it up and setting the angle as I cut to fit the tenon.
it seemed like it made the job easier on the violin sized body to trial and error and fine tune a tight fit. I hope it works on the bigger bass as well.

That's smart. I considered deepening the mortise instead of building up the shoulders, but at this point I've lost track of how thick the neck block is and don't want to remove too much material where the bolts go through.

If I were to do it again, I might assemble the body first, then route the mortise. I see acoustic guitar guys doing that, and I was resisting building the jig to do it, but it does make sense.

 

[Crawforde]

I think routing (or carving) the block on the assembled or partially assembled body and then fitting to the neck is probably the best way to go given how much things can move and angles can change slightly during bending, and gluing, but that requires forethought and the construction of a good jig, the first is one of my weaknesses, and the second assumes the forethought.

 

[Max Bogosity]

20 months later update:

I fitted some shims to the neck joint, bolted it together, strung it up, and it was pretty playable right off the bat without even levelling the fingerboard. Unfortunately, it was also immediately pretty clear that it failed the original goal to be smaller and more convenient than a full-sized double bass. It's not as wide, but it takes up basically the same space and is just about as delicate. So I parked it in the corner of the room and never finished it.

After a year and a half under tension, some of the glue joints in the neck are now very obvious to the touch. I think the offenders are the factory joints in the bamboo flooring, rather than my own joints. It's not 100% clear because there are dozens of longitudinal joints, but the glue line on either side of the walnut veneer is definitely mine, and that seems OK. I suspect it's creeping under the load from string tension because there's no sign of any ridges/mismatch once you get up into the scroll area where there's no tension.

Overall, not really a useful instrument, but I could still put a bulb in it and turn it into a lamp.

Lessons learned:

• The three-layer construction technique for the neck was basically successful and made the pegbox a lot easier than it would have been if I'd had to dig it out with a chisel.
• Carving a scroll is fun and not as hard as it looks.
• Don't build anything out of bamboo. It's splintery and nasty.
• Don't trust the unknown glue in composite flooring. Resistance to creep isn't a requirement for flooring; it is for a neck.
• The eBay fingerboard was surprisingly good, and cheaper than buying an ebony blank would have been.
• Barrel nuts from the box store made for a pretty successful bolt-on neck joint.
• It's hard to keep the neck block straight while gluing up the body, so either it needs a jig for alignment during assembly or cut the mortise afterwards.
• My sandpaper 'reamer' for the tailpin hole succeeded in producing the right taper, but the hole came out crooked. I could have made another attempt, or else reamed the hole first and then cut the faces to be square to the hole rather than vice versa.
  
• The fairly gentle bends in the plywood of the body were not a big deal. Ratchet straps were very useful to pull everything into place.
• Ferric acetate applied to walnut makes a fairly convincing substitute for ebony, at least on a cosmetic level.
• A full sized mockup would have made the ergonomic issues obvious at an earlier stage.

 

[NKBassman]

Overall, not really a useful instrument, but I could still put a bulb in it and turn it into a lamp.