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-   -   Bubinga and Sitka Spruce Acoustic Bass Guitar by Dickinson Portland Guitar (https://www.acousticguitarforum.com/forums/showthread.php?t=573380)

Portland Guitar 02-26-2020 03:23 PM

Bubinga and Sitka Spruce Acoustic Bass Guitar by Dickinson Portland Guitar
 
This is an acoustic bass guitar built for a gentleman in Chicago. In talking about the build a preference was made for a more modern design. It will feature all of our typical technology the cantilever neck and adjustable bridge with an artful and elegant design.

Bubinga or as some call it african rosewood was choosen becasuse it has a nice deep sound. We made a 16" guitar out of it which had incredible bass response. We're recreating a similar feeling in this build. Sitka spruce will be the top as to provide a clear tone throughout.

Here are pictures of the top, back, and sides.
https://www.dropbox.com/s/2dwyd4vwg3...5336.jpg?raw=1

https://www.dropbox.com/s/mat58p602x...5725.jpg?raw=1

We bought an 8 foot board of bubinga and re-sawed it. Here is Jay at work.
https://www.dropbox.com/s/462iceyem1...4557.jpg?raw=1

The first step taken is to bend the sides. Here is a side in the bendalator.
https://www.dropbox.com/s/h3b0hwq1n9...2417.jpg?raw=1

SJ VanSandt 02-26-2020 03:30 PM

I was just daydreaming about acoustic bass guitars this morning! Looking forward to seeing how this one comes out - thanks for posting.

Stan

Bill Kraus 02-27-2020 08:04 AM

I can't wait to see the bracing used throughout this bass, keep the photos coming.

Portland Guitar 02-27-2020 08:15 PM

I'm excited to see how it comes out too!


The bracing will be falcate. I'm worried they will be too light so I'm aiming for a little thicker.


Here's today's photos.*


The joined top.*
https://www.dropbox.com/s/702yce2dt8...5058.jpg?raw=1

The joined back
https://www.dropbox.com/s/lg3zmj12sh...4924.jpg?raw=1

Jay at work gluing
https://www.dropbox.com/s/1uktd4bhhj...5026.jpg?raw=1

https://www.dropbox.com/s/jdn4s6hq45...4725.jpg?raw=1

The curf glued onto the sides. Lots of clamps
https://www.dropbox.com/s/54ij3nal0s...0005.jpg?raw=1

GeoffStGermaine 03-01-2020 08:01 AM

Don't see a lot of basses on here. I'm looking forward to seeing more, particularly of the Falcate bracing!

Portland Guitar 03-14-2020 08:18 PM

Hello Acoustic Guitar Forum,

Today’s updates come in two parts. The first post shows wrapping up the preparation of the body with the top and back. The inner and outer rosette are added in here. The second post will be everything with braces
Here are the top and back after the join.
https://www.dropbox.com/s/04s6lfw4fk...4924.jpg?raw=1
https://www.dropbox.com/s/t63q385am3...5058.jpg?raw=1
We want those boards to be nice and even throughout, so they are sent through the drum sander a few times.
https://www.dropbox.com/s/6sskd0lbqf...4746.jpg?raw=1
We make the cut for the join on the cnc. This gives an incredible straight line for both the board to match up on. This gives us an even join throughout. It’s at the point where we can lose sight of the join line easily.
Here are those pieces cut into shape https://www.dropbox.com/s/q4yije0hni...Copy.jpg?raw=1
Before they go onto the body the back needs it’s inner rosette and the top needs the outer rosette. The theme for this guitar is based on the sun and the moon. A stylized eclipse was routed for the back.
https://www.dropbox.com/s/43ncql9tx2...Copy.jpg?raw=1
A signature wave design was used for the top.
https://www.dropbox.com/s/m1prdskgda...4113.jpg?raw=1
Those will be glued into the frame
https://www.dropbox.com/s/w1yolb137t...4807.jpg?raw=1

Portland Guitar 03-17-2020 02:13 PM

Everything Braces!
A few design decisions were made along the way. At first a five layer brace for the top was the plan. With the use of two layers of carbon fiber between three layers of mahogany. Instead to decrease the surface area to allow for more resonance a three layer brace was used with only two layers of two wood and one carbon fiber.
To provide the strength we need the center braces are extra tall. The strength of them grows proportional to the height. The main stress on the guitar is on the bridge and down the neck. So the structure of the braces reinforce that area the most
After the braces are glued onto the top, it is put through a process we like to call torque tuning. A weighted arm is put on and we measure the amount that the arm bend. By a simple calculation we know exactly how much deflection we need for a minimally braced top. The braces are sanded until we are satisfied it will be strong enough and responsive enough.
Here are the pictures documenting the process. Enjoy!
First are the materials used for the braces. Carbon fiber and mahogany
https://www.dropbox.com/s/e4hr5rik2i...4429.jpg?raw=1
The wood is bent while dry and kept in a form by clamps
https://www.dropbox.com/s/1d80y864i7...4406.jpg?raw=1
Lots of clamps are used to glue the layers together. We use a 2:1 epoxy for this.
https://www.dropbox.com/s/k40dyijlto...4322.jpg?raw=1
The braces are placed on the top and the best placement is considered.
https://www.dropbox.com/s/2f7gly5px2...4115.jpg?raw=1
Here’s Jay sketching out the brace position
https://www.dropbox.com/s/va2mcqp0pl...3904.jpg?raw=1
Then the extra brace is trimmed
https://www.dropbox.com/s/eubzaxtyi7...3842.jpg?raw=1
To glue them in a go-box is used with tension rods. Glue is slippery and sticky, so care is used when placing the rods.
https://www.dropbox.com/s/bfkrjh2anc...3819.jpg?raw=1
The height of the back braces is about a half-inch. Less brace is needed on the back because it doesn’t need structural support it only has to hold the shape in place
https://www.dropbox.com/s/wj7vr3s8fy...3759.jpg?raw=1
Onto the top, Lots of bracing going up the bridge to the fretboard. It must support about 160-200 lbs of tension from those strings.
https://www.dropbox.com/s/ccmuzi9u19...3737.jpg?raw=1
The brace height is higher.
https://www.dropbox.com/s/f4476cnnjz...3717.jpg?raw=1
The back braces are shaped to look pretty
https://www.dropbox.com/s/1ruskncdkn...3352.jpg?raw=1
This is the setup for our torque tuning. The top is clamped down simulating the stiffness of the sides. A lever arm is attached at the bridge and the weight is put on. We measure the bend.
https://www.dropbox.com/s/r8a27qrw5z...3126.jpg?raw=1
The braces are sanded to decrease the stiffness
https://www.dropbox.com/s/wqg5guqvyb...3047.jpg?raw=1
The amount of bend
https://www.dropbox.com/s/icus7t1etz...3024.jpg?raw=1
The finished top!
https://www.dropbox.com/s/3fi4vcneo3...2949.jpg?raw=1

Thank you for reading!

Portland Guitar 04-01-2020 11:32 PM

Hello!

I hope everyone is staying healthy and safe. It’s a strange time but we will get through it together. It’s helpful to us to focus on building guitars. We’re about halfway through this one. The next steps are to get the body together afterwards the neck and fretboard. Here its first sounds.

Here is Jay taping the top.
https://www.dropbox.com/s/1klgx1ejcq...4457.jpg?raw=1
This is the body once the top and back have been glued on .
https://www.dropbox.com/s/4dya5pokeq...4608.jpg?raw=1
The body needs to have the scratches removed so it is gently put in the vice and sanded.
https://www.dropbox.com/s/rbhjek24gk...2517.jpg?raw=1
The body is done and now it’s on to the neck. The table saw is used to make the board into a 3”x3” cube.
https://www.dropbox.com/s/urdzmszuhh...0541.jpg?raw=1
By tessellating the necks in our mahogany board two neck can be gotten out of one piece. The band saw has good flexibility to cut the outlines for the neck.
https://www.dropbox.com/s/o28jzyg4ur...1817.jpg?raw=1
The neck blank cutout is put in the CNC. The entire job is done over four sides. First the top, next the back then both sides. Here is the CNC working on the top.
https://www.dropbox.com/s/7gc1k5u7pz...4749.jpg?raw=1
The completed top of the neck base.
https://www.dropbox.com/s/ltotz4qqmp...5031.jpg?raw=1
The work on the side of the heel.
https://www.dropbox.com/s/g92cqrcqbt...3658.jpg?raw=1
The completed job.
https://www.dropbox.com/s/juduq6q3tn...1417.jpg?raw=1

Our attention now turns to the fretboard. Jay has been giving complete artistic license on this guitar, so he has decided to do ornate marquetry with a day and night theme.
I’ve been spending my quaran-time playing guitar and I hope it brings everyone a little stress relief.
Best, from Max and Jay.

Portland Guitar 04-04-2020 08:42 PM

Welcome back to our acoustic bass guitar build. We have the body together and the neck close to complete. We need a fretboard and a headstock plate to glue to the neck blank before the body is complete. The headstock, fretboard and bridge are all matching ebony. The theme of the guitar is to use our signature wave with a day and night theme.
The fretboard marker dots are replaced with medallions depicting the rise and fall of the moon and sun. A pocket will be routed in the fretboard and these will be placed in it.
https://www.dropbox.com/s/5daimoaz9n...4015.jpg?raw=1
https://www.dropbox.com/s/1ywor99b8z...4041.jpg?raw=1
https://www.dropbox.com/s/ppl35vaecs...4125.jpg?raw=1
https://www.dropbox.com/s/fi11j0jy29...4209.jpg?raw=1
https://www.dropbox.com/s/wtyxbd1zzj...4355.jpg?raw=1
https://www.dropbox.com/s/92sldyejlk...4413.jpg?raw=1
https://www.dropbox.com/s/8ziye2n7lq...4537.jpg?raw=1
https://www.dropbox.com/s/0wasr1iep3...4555.jpg?raw=1
Here is the CNC working on those routes on the fretboard.
https://www.dropbox.com/s/mmoezkvdxe...4626.jpg?raw=1
With that the fretboard can be glued onto the neck blank. Our neck and body is complete and the neck can be attached to the body.
These are the final pictures of the guitar in the white before it is finished.
https://www.dropbox.com/s/a7p9fo76ng...ll-5.jpg?raw=1
https://www.dropbox.com/s/xl9jfizyrc...ll-2.jpg?raw=1
https://www.dropbox.com/s/q6z3ckgong...ll-6.jpg?raw=1
https://www.dropbox.com/s/d5w6a5cmmx...ll-1.jpg?raw=1
https://www.dropbox.com/s/ibi2oj5mm3...ll-3.jpg?raw=1
https://www.dropbox.com/s/ka6n1rsopz...ll-7.jpg?raw=1
The scale length of the neck is short at 30” which is why it doesn’t look as large as a typical bass guitar. That’s all for now. The next step is to put the finish on.
Best wishes from Max and Jay

Portland Guitar 05-03-2020 08:01 PM

The bass guitar has had the finish put on and the final touches applied. We use a high gloss lacquer that is sprayed on. We try to keep the finish light so the top does not have too much extra mass on it. This helps the sustain and response. The nut is a straight nut made from ox bone. The bridge is our house design split saddle bridge adapted for a bass.
Here are the final pictures before it ships out.
https://www.dropbox.com/s/88uu8uy4zg...a-07.jpg?raw=1
https://www.dropbox.com/s/4i1c1xh6o7...a-01.jpg?raw=1
https://www.dropbox.com/s/d8z006itu4...a-08.jpg?raw=1
https://www.dropbox.com/s/8gx0598foc...a-02.jpg?raw=1
https://www.dropbox.com/s/3a5125mmmk...a-06.jpg?raw=1
https://www.dropbox.com/s/19cg6vdfa5...a-09.jpg?raw=1
https://www.dropbox.com/s/630w5fpcu6...a-03.jpg?raw=1
https://www.dropbox.com/s/eivg3m9140...a-04.jpg?raw=1
https://www.dropbox.com/s/llfln1kzsa...a-05.jpg?raw=1
https://www.dropbox.com/s/gurmiyu0vz...a-10.jpg?raw=1
https://www.dropbox.com/s/qb95orm5b3...a-11.jpg?raw=1
https://www.dropbox.com/s/yhycfo4tgi...inga.jpg?raw=1

Thank you everyone for following along!

Nemoman 05-04-2020 10:16 AM

Wow--such a unique guitar!

Thanks for sharing and taking us along on the ride.


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