Acoustic bass - carved top

[honza992]

Phew!  I'm running as my 7 year old is due back from dance class in 14 minutes at which point she purloins the laptop😟 I've tried explaining to her that Basschat is WAAYYYY cooler than The Worst Witch, but her powers of negotiation a lightyears beyond mine🙄

 

So, I've started work on the top. My design is largely based on Benedetto's published shapes.  I've stretched and squeezed it somewhat to fit my needs, but that was it's origin.  I want to rout contours into the top to help with the carving.  I'm not good enough to do freehand carving so I want as much help as possible.  So....the incredible, the wonderful, the extraordinarily good looking @Wookiebass did some CAD jiggery to do a contour map for me.  I've added a few more contours to it so it looks like this:

 

 

I then cut out each of the contours and stuck them to 4mm MDF, cut them out and sanded them to shape.  I now have a stack of contour templates, ready for the real fun to start!

 

 

Or maybe I'll just stick a bridge onto the top of that and call it done. 🙂

[Richard R]

I love these build threads.

I am both envious of the talent and jealous of the tools. Or possibly the other way round. 

[Si600]

2 hours ago, honza992 said:

Phew!  I'm running as my 7 year old is due back from dance class in 14 minutes at which point she purloins the laptop😟 I've tried explaining to her that Basschat is WAAYYYY cooler than The Worst Witch, but her powers of negotiation a lightyears beyond mine🙄

Presumably because you are no longer prepared to scream and scream until you are sick?

[Si600]

2 hours ago, honza992 said:

 

 

 

Or maybe I'll just stick a bridge onto the top of that and call it done. 🙂

I've heard worse ideas 🤣

 

How does the template work?  Presumably there's some sort of scale reduction because that looks a very big dish, more like one of those medieval spoon shaped instruments than a carved top.

[honza992]

17 minutes ago, Si600 said:

Presumably because you are no longer prepared to scream and scream until you are sick?

Correct.  The screaming makes my tinitus go haywire. 

[honza992]

15 minutes ago, Si600 said:

I've heard worse ideas 🤣

 

How does the template work?  Presumably there's some sort of scale reduction because that looks a very big dish, more like one of those medieval spoon shaped instruments than a carved top.

Yep.  The total thickness of the top is 16mm.  The dome will be 12mm.  So dividing 12 mm by 9 templates, means each template will be used to only take off 1.3mm.  Archtop guitars I think have a much bigger dome - 16-18mm, but my complete finger-in-the-air guess is that that's too much for a bass.   I've never done this before though, so it will be a voyage of discovery for all of us!

[alittlebitrobot]

22 hours ago, honza992 said:

 Ho hum. Will I never learn....@alittlebitrobot don't answer that)

🤐

 

Love the progress. What's going on here, though? It's intriguing

[honza992]

16 hours ago, alittlebitrobot said:

🤐

 

Love the progress. What's going on here, though? It's intriguing

 

It's basically a moxon clamp adapted to hold guitar bodies.  Two outer pieces of 18mm MDF, then two inner pieces of 4mm MDF held in a curve.  It means the clamping pressure is applied to the edges not the top/back of the guitar.  Other than the MDF it's two 1 inch diameter pieces of pipe, two flanges which I've just screwed into the table, then pipe clamps.  Like all my jigs it's ugly, but works really well.  

 

Here it is holding the last build:

[honza992]

Contours done, upside down on the router table. Next, carving..

 

[alittlebitrobot]

1 hour ago, honza992 said:

 

It's basically a moxon clamp adapted to hold guitar bodies.  Two outer pieces of 18mm MDF, then two inner pieces of 4mm MDF held in a curve.

Oh, that's brilliant. I'm very much a slab body guy so this not my area but that's a great jig.

[AndyTravis]

Love these basses 😍

[honza992]

Does anyone have any views on what piezo pickups I should use with this one?

 

The last one has a K&K glued on the inside of the soundboard.  I want to try something different to contrast.  The obvious options are:

Fishman Matrix piezo element under the saddle:

https://www.thomann.de/it/fishman_matrix_infinity_vt_narrow.htm

or 

 

https://graphtech.com/collections/ghost-pickup-systems-kits/products/ghost-bass-acousti-phonic-kit

coupled with these elements which I could fit into a handmade bridge:

 

Any one with any thoughts?  I know Rob Allen uses a version of the Fishman matrix....The Ghost, I've no experience of....

 

[Andyjr1515]

I haven't used Ghost stuff for bass guitars but I've used both Acoustiphonic and Hexpander units and piezo elements on a number of my own solid and semi 6 string guitars.  Pricey but very competent - other than the 'collector block' that the connectors for each of the piezo wires plug into.  Shockingly bad bit of tat that can (and does) stop the show.  If they've changed that design/supplier then fine - it makes a good but flawed system great.  If they are still supplying it, then shame on them.

 

[Daz39]

On 14/03/2024 at 17:25, honza992 said:

Phew!  I'm running as my 7 year old is due back from dance class in 14 minutes at which point she purloins the laptop😟 I've tried explaining to her that Basschat is WAAYYYY cooler than The Worst Witch, but her powers of negotiation a lightyears beyond mine🙄

 

So, I've started work on the top. My design is largely based on Benedetto's published shapes.  I've stretched and squeezed it somewhat to fit my needs, but that was it's origin.  I want to rout contours into the top to help with the carving.  I'm not good enough to do freehand carving so I want as much help as possible.  So....the incredible, the wonderful, the extraordinarily good looking @Wookiebass did some CAD jiggery to do a contour map for me.  I've added a few more contours to it so it looks like this:

 

 

I then cut out each of the contours and stuck them to 4mm MDF, cut them out and sanded them to shape.  I now have a stack of contour templates, ready for the real fun to start!

 

 

Or maybe I'll just stick a bridge onto the top of that and call it done. 🙂

Ooh - looks like a hill feature for a gaming table. Quick - someone roll for initiative.

[Si600]

1 hour ago, Daz39 said:

Quick - someone roll for initiative.

Natural 20, booyah!

[honza992]

Carving in progress. I'm not sure how it's going. It's definitely going to take some practice...

 

 

😬

Edited March 20 by honza992

[alittlebitrobot]

God, I'm never doing an archtop 😆

[honza992]

22 hours ago, Andyjr1515 said:

I haven't used Ghost stuff for bass guitars but I've used both Acoustiphonic and Hexpander units and piezo elements on a number of my own solid and semi 6 string guitars.  Pricey but very competent - other than the 'collector block' that the connectors for each of the piezo wires plug into.  Shockingly bad bit of tat that can (and does) stop the show.  If they've changed that design/supplier then fine - it makes a good but flawed system great.  If they are still supplying it, then shame on them.

 

Ok thanks Andy, good to know. Any instinct as to whether the Ghost saddle units are less susceptible to feedback than the more normal piezo strip that goes under the saddle?

[Hellzero]

The best and very expensive piezos are the RMC's with their dedicated preamp: you'll get all the low end lacking usual piezos.

 

I also have the Fishman BP-100 twin piezo on my Leduc U-Basses: it's glued under the soundboard at two strategic places.

 

If you add the Fishman PowerChip buffer-preamp to the BP-100, you'll get an amazing full sounding system.

[honza992]

3 hours ago, Hellzero said:

The best and very expensive piezos are the RMC's with their dedicated preamp: you'll get all the low end lacking usual piezos.

 

I also have the Fishman BP-100 twin piezo on my Leduc U-Basses: it's glued under the soundboard at two strategic places.

 

If you add the Fishman PowerChip buffer-preamp to the BP-100, you'll get an amazing full sounding system.

Thanks Hellzero for those suggestions.  I wondered if anyone had put the BP100s into a bass rather than double bass, there's my answer.   I may well come back to you to explore this a bit more.  But it's a non-permanent install, is that right?  The trouble with the K&K is that it's permanent - they're superglued to the inside of the top.  These are prototypes I'm building so it would be good to know I can chop and change the electronics around. 

 

Also, I may drop RMC a line and see what they would recommend for an archtop bass.  Cheers!

[Hellzero]

1 hour ago, honza992 said:

But it's a non-permanent install, is that right?

The piezo under the bass part is glued under the top and treble part is positioned around the treble post area.

[Hellzero]

On 16/03/2024 at 09:26, honza992 said:

Contours done, upside down on the router table. Next, carving..

 

But I'm sure you could modify this bridge to accommodate the twin piezo on each side of it.

[honza992]

OK round one of the carving is complete.  I left it 1mm thicker everywhere on purpose in order to give me a chance to see how the carving was going without risking it getting too thin.  Time to get serious.  I routed the perimeter down to 4mm, it's final thickness.

 

 

 

Time to crack out the gouge and mini plane again.  I'm not finding it easy planing it without getting tearout.  Wood is like cats fur, it want's to go in one direction.  Get it it wrong and the blade can get out under the fibres and pull out a chunk.  Carving it is like butter, till suddenly it isn't.  It's also a second grade piece of wood, so there's lot's of grain runout, making tearout even more difficult.  So far so good though....

 

 

 

Edited March 25 by honza992

[honza992]

OK, the carving of the top I'm calling finished.  There's still a bit of refining to do, particularly on the cutaway, but I'll do that with sandpaper once the top is on.  

 

 

Turning over I use the drill press to mark a 4.25mm depth everywhere (4mm mdf and a 0.25mm feeler gauge).  I use a simple wood dowel with a thin piece of cork on top.  Without that the top will get dented from the force of the top being pushed against the dowel. 

 

 

 

I then drill several million holes to within 25mm of the side (note to self, template #8).  Several million more to go tomorrow.   I'm exhausted.....

 

[honza992]

I'm working on the inside carve.  At the moment I'm doing it all with a gouge.  It's probably a bit small (Sweep 5, 18mm in case anyone is interested), but it's an utter utter joy.  

 

 

The grain is tricky.  The middle section (marked in pencil) runs opposite to the areas either side.  I wake up sweating in the middle of the night just thinking about tearout.....