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32" Fully hollow Archtop Bass - build diary
- Thread starter honza992
- Start date
The neck joint of #3 was a hybrid of a normal archtop joint with an extension under the fretboard, and the bolt-on design of Gore. It used just a single bolt holding the fretboard extension down, and a single wood screw holding the neck to the sides. The sides are were only 5cm, which I thought was too shallow for a dovetail joint, so it's simply a butt. I don't if that makes sense. Let me know if you want any more details.
Edit to add a photo showing the T nut that goes under the fretboard:
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@Gilmourisgod I should say that I'm not using that neck joint again though! On this build I think I've decided to use more or less a standard electric style bolt-on neck joint. The one shown above is fun to make but it's complicated and frankly I think a simple fender style neck joint is just as strong (if not stronger) and should be easier to change the neck angle if necessary just using shims. Guitarists like a complicated dovetail neck extension thing because that's how pre-war Gibsons were made. Us bassists are much more open minded 
After @Gilmourisgod asked about the neck joint, I drew out what my current plan is. For some reason I just can't get my head round CAD. I've tried I don't know how many times, I've even had a few lessons. But my brain is too old and stubborn, so I've resigned myself to staying with paper and pencil. I do a full size drawing for each build. Here's the top and side view of the neck join:
Basically it's a block out of which I'll rout the neck pocked from above, and the access cavity from below.
I haven't quite decided what to make it out of. I've got some alder body blanks left over from when I used to make electrics, so a lump of that might work fine. Or for something more dimensionally stable, I may use plywood. One issue I need to think about is gluing surfaces. I don't want too much end-grain join. Any one with any thoughts?
I'll use @Bruce Johnson 's Bruce bars under the fretboard for the nuts, and m4 bolts.
I also need to think about stress risers around the neck block where it joins the top. I'll leave the top a litte bit thicker there, and may also put a bead of epoxy around the join, a bit like you put silicone round the bath.
(Credit to Iulius Guitars for the neck joint inspiration!)
Basically it's a block out of which I'll rout the neck pocked from above, and the access cavity from below.
I haven't quite decided what to make it out of. I've got some alder body blanks left over from when I used to make electrics, so a lump of that might work fine. Or for something more dimensionally stable, I may use plywood. One issue I need to think about is gluing surfaces. I don't want too much end-grain join. Any one with any thoughts?
I'll use @Bruce Johnson 's Bruce bars under the fretboard for the nuts, and m4 bolts.
I also need to think about stress risers around the neck block where it joins the top. I'll leave the top a litte bit thicker there, and may also put a bead of epoxy around the join, a bit like you put silicone round the bath.
(Credit to Iulius Guitars for the neck joint inspiration!)
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What type of piezo pickups do you have planned?Don't tell anyone, but this one will have magnetic and piezo pickups.....
Hi Matthew
The ones I've tried so far are the K&K on the soundboard which reproduces the acoustic very nicely but is too sensitive to feedback.
The Fishman infinity UST feeds back even more, and doesn't sound as nice as the K&K.
@EliasA Suggested the LR Baggs anthem, so I wrote to them to get their advice. Their support desk thought that the Anthem would feedback too much and suggested their UST. Which I thought was a bit odd because plenty of high end acoustic basses have got the LR Baggs Anthem installed, the Furch BC 61 for example.
I realise I'm just fighting physics. Low frequencies feedback more than high. Lightly braced guitars feedback more than heavily braced ones. But heavily braced bass guitars sound horrible.
So I'm almost certainly going to try the Ultra Tonic soundboard transducer from James May. It has a built in feedback inhibiter. By chance does anyone have it installed in a bass?
Hmm, that's curious. The Anthem is notably low-output, which is why I suggested it, along with the mic/piezo blend feature. I should look at these two options (UST and Ultra Tonic) you're talking about.
Many years ago, when I was developing Banjozilla, my giant upright bass banjo, I ran into horrible feedback problems trying to amplify it. That 24" diameter mylar head was a giant super-sensitive microphone, and it would detect any sound in the air and send it back through the strings and any pickup or mic or piezo element. Instant massive feedback.
The only thing that kind of worked was to mount a pair of Fishman disc pickups on the bridge. Not under the feet, but standing up vertically fastened on the back surface of the bridge. That reduced the feedback to a workable level. I think the reason is that it was picking up the forward-backward motion of the bridge rather than the up-and-down motion of the top, so it was partially out of phase with the movement of the top.
I offer this as an idea of something you could try. Mount the K&K or the Fishman on the bridge, in a vertical plane. Try to decouple it from the vertical movement of the top. Because that's where the feedback comes from; external sound waves pounding on the top.
OK, thanks Bruce, that's another option to mull. What was the effect on the amplified tone, in comparison to having it in the horizontal plane?
Quick question, which orientation do you prefer for the back?
Up, or down? Or is it down or up?
Up, or down? Or is it down or up?
The tone was okay, a good representation of the sound on the strings. However, it wasn't the boomy "acoustic" sound of the huge drum head. So, the Fishmans on the back of the bridge kind of worked. I could plug into a small amp or a channel of the PA and get a decent sound. But we would boost the low-mids of the EQ at the amp to get the boomy sound. And we would have to be really careful not to put much into the monitors or anything nearby. Any of that low-mid boom hitting Banjozilla's head was instant boom.
When we recorded Banjozilla in the studio, we tried different things. The Fishmans and mics in different places. We got the best recorded sound with a good studio mic placed about 3 feet in front of the head. A quiet studio room, no sound through the monitors. I was just listening to it acoustically as I played.
Later, playing Banjozilla on stage with my bluegrass band with a small PA system, I'd put a SM58 on a low stand about 3 feet in front of the head. Then carefully feed a small amount of it through my stage monitor, with the bottom end rolled off. To me, on stage, it sounded real twangy. But it sounded good out front.
This is an inherent big problem with any acoustic bass-range instrument. If that big surface-area top is able to pump out bass tones, then it is also a very sensitive microphone. It'll pick up any bass tones around it and feed them right back into the strings. It's a big problem with no easy solution.
I usually prefer the look of any "V" in the grain facing back. But in this case, the V might look nice facing forward, accenting the join with the neck.
^ +1 bottom picture.
Looks awesome.
I love playing my original ‘69 Fender Coronado II bass unamplified for solo practice too, esp outdoors on a nice day. Fully hollow carved front & back with f-holes.
The Rob Allen Mouse is great but definitely designed in a different direction.
Looks awesome.
I love playing my original ‘69 Fender Coronado II bass unamplified for solo practice too, esp outdoors on a nice day. Fully hollow carved front & back with f-holes.
The Rob Allen Mouse is great but definitely designed in a different direction.
I've made a bit of progress on this build, so here's a quick update.
The neck is made from a single piece of flame maple. I cut it into 3, jointed the gluing surfaces, and laid them out so the centre piece is pretty much quarter sawn, the the other two have the grain lines running in opposite directions. I'm a sucker for veneers, but this time I'm going for a slightly more subdued look, so it's only 2 black veneers making up the sandwich:
And glued!
I then cut the scarf joint on the bandsaw, thinned it down to 16mm then glued the two pieces together with another black veneer in the join. When the neck is carved these straight lines will be curved and meet up on the headstock. Clamped using West Systems epoxy. I use West Systems for pretty much all my structural joints. It has a long open time tight clamping pressure is much less important. Apologies for the blurred photo:
Next, the fretboard. For the first time ever, I'm using a pre-slotted fretboard. In the workshop I have a radial arm saw which I normally use for slotting. Here it is...
It's massive. And I have a 240 square foot workshop. And literally the only thing I use it for is fret slotting. And I would love to have a dedicated table for a go-deck. So.....I fear the saw has gotta go.
Here's the fretboard being bound. I love binding. I put it everywhere. The fretboard is ebony, with ebony binding and a pinstripe. I glue the veneer first, then the binding on top, just using CA glue. Here's the veneer glued on, and one piece of binding already attached.
I can't quite remember why they're not in the picture, but I alway use little teflon strips in the fretslots to stop the CA glue from making too much of a mess. Though it alway seems to end up looking pretty awful...
...until everything is scraped and sanded to 600 grit. THIS is why I love binding ebony fretboards. They look amazing, and when the white lines join seemlessly at the corners it's very satisfying.
Tomorrow, I'll do an update on the sides and back....
The neck is made from a single piece of flame maple. I cut it into 3, jointed the gluing surfaces, and laid them out so the centre piece is pretty much quarter sawn, the the other two have the grain lines running in opposite directions. I'm a sucker for veneers, but this time I'm going for a slightly more subdued look, so it's only 2 black veneers making up the sandwich:
And glued!
I then cut the scarf joint on the bandsaw, thinned it down to 16mm then glued the two pieces together with another black veneer in the join. When the neck is carved these straight lines will be curved and meet up on the headstock. Clamped using West Systems epoxy. I use West Systems for pretty much all my structural joints. It has a long open time tight clamping pressure is much less important. Apologies for the blurred photo:
Next, the fretboard. For the first time ever, I'm using a pre-slotted fretboard. In the workshop I have a radial arm saw which I normally use for slotting. Here it is...
It's massive. And I have a 240 square foot workshop. And literally the only thing I use it for is fret slotting. And I would love to have a dedicated table for a go-deck. So.....I fear the saw has gotta go.
Here's the fretboard being bound. I love binding. I put it everywhere. The fretboard is ebony, with ebony binding and a pinstripe. I glue the veneer first, then the binding on top, just using CA glue. Here's the veneer glued on, and one piece of binding already attached.
I can't quite remember why they're not in the picture, but I alway use little teflon strips in the fretslots to stop the CA glue from making too much of a mess. Though it alway seems to end up looking pretty awful...
...until everything is scraped and sanded to 600 grit. THIS is why I love binding ebony fretboards. They look amazing, and when the white lines join seemlessly at the corners it's very satisfying.
Tomorrow, I'll do an update on the sides and back....
For the first time I'm doing double sides on this build. I've used two layers of 1.5 mm walnut. A 3mm double side is more than 3 times stronger than a standard single side of 2mm,. I'm hoping the less energy get's absorbed by the sides. the more the top can vibrate.
Bending I do on a side bending iron. For some reason I didn't take any photos so here's one from a previous build.
Once bent I then glued the two sides together using West Systems epoxy in a vacuum bag using a simple plywood mold. I use a Roarocket vacuum bag which uses a wine-style vacuum pump, and it works brilliant. I've used these bags for years to glue electric tops and never had a failure. I really recommend them. No need for an expensive vacuum pump unless your making kitchens....
Here' one of the sides being glued:
One thing I've learned with epoxy is to always tape off parts that you don't want covered in squeeze out. It dries hard, really hard, and sanding it will drive you nuts. So I put packing tape (sellotape) on both sides that didn't get the glue. The outside just needed a bit of a wipe with alcohol to get off some of the residue from the tape. Here it is, no sanding or anything, and it's nearly perfect:
The inside had a little bit of squeeze out. But it took probably 3 minutes with a scraper to get rid of it.
One side waiting patiently for the cutaway side to emerge...
And the cutaway....
This was such a success I'm going to be using double sides from now on. Bending them is much easier at 1.5mm, glueing them was easy, and they are really sturdy.
Happy days!
One tip....rather than pumping away forever to get most of the air out of the bag you can suck most of it out with your shop vac by just putting the hose over the valve. The last 10% I do with the wine pump once I'm happy nothing has moved in the bag. Epoxy's great though, things don't seem to slide around nearly as much as with titebond.
Bending I do on a side bending iron. For some reason I didn't take any photos so here's one from a previous build.
Once bent I then glued the two sides together using West Systems epoxy in a vacuum bag using a simple plywood mold. I use a Roarocket vacuum bag which uses a wine-style vacuum pump, and it works brilliant. I've used these bags for years to glue electric tops and never had a failure. I really recommend them. No need for an expensive vacuum pump unless your making kitchens....
Here' one of the sides being glued:
One thing I've learned with epoxy is to always tape off parts that you don't want covered in squeeze out. It dries hard, really hard, and sanding it will drive you nuts. So I put packing tape (sellotape) on both sides that didn't get the glue. The outside just needed a bit of a wipe with alcohol to get off some of the residue from the tape. Here it is, no sanding or anything, and it's nearly perfect:
The inside had a little bit of squeeze out. But it took probably 3 minutes with a scraper to get rid of it.
One side waiting patiently for the cutaway side to emerge...
And the cutaway....
This was such a success I'm going to be using double sides from now on. Bending them is much easier at 1.5mm, glueing them was easy, and they are really sturdy.
Happy days!
One tip....rather than pumping away forever to get most of the air out of the bag you can suck most of it out with your shop vac by just putting the hose over the valve. The last 10% I do with the wine pump once I'm happy nothing has moved in the bag. Epoxy's great though, things don't seem to slide around nearly as much as with titebond.
I happen to have experimental verification that the VacuVin pumps pull a pretty good vacuum for a mechanical pump. Far removed from my days in labs with fancy gauges, but I used one to evacuate a "penny-feather" tube for demonstrating that the two will fall at the same speed without air resistance, and it worked like it should.