Multiscale Chambered 8-string Hybrid Singlecut - build thread

[Erik Hauri]

BH-8 chambered singlecut multiscale 8-stringer

OK so this is a collaboration with Ben to build a chambered singlecut 8-string bass/guitar hybrid instrument – and a multiscale on top of it (why not, right?). The design borrows from some obvious influences, but also benefits from some improvements to the body design, neck joint and layout of the multiple scales. There are some cool features to the build that will be good to document.

Here’s the menu:
Walnut chambered body core
Figured claro walnut top, back & headstock lam with wenge accent layers
5-piece maple-walnut neck with CF reinforcement
Tru Oil finish
29.5” to 25.5” scale, 7th fret perp
Bartolini humbuckers and paired P-bass pickups (passive)
Master Vol (push-pull coil tap) & Tone, 3-way switch for humbuckers
Stacked Vol-Tone for bass pickups
Separate outputs for bass & guitar pickups

Ben will be using this for pursuing some new directions in jazz guitar – I am almost as anxious as he is to hear what he can do on this thing.

Here are some shots of the claro top with the body outline superimposed – the knots in the center will be mostly routed out in the pickup routs by angling the bookmatch seam.

Gotta have a template:

Neck lams are individually milled in the drum sander.

This might be the first photo I’ve shown of my glue press – pretty simple, a set of 2” high aluminum angles to keep everything dead straight and distribute the pressure from 8-10 bar clamps. Trigger clamps at the ends and in the middle (through a hole in the table) keep all the lams firmly down against the table. Wax paper underneath so I don't glue the neck to the bench....

Carbon fiber bars routed and installed. I like the System 3 epoxy adhesive for all my epoxy gluing tasks (resin 105 and slow hardener) – it is very forgiving in the mix ratio, so that you can use pumps instead of measuring with a scale.

 

[hufschmid]

wow, awesome so far, keep us updated please

 

[Empryrean]

Yes

 

[vansinn]

This will be very interesting to follow. Beatyful walnut you have there..
I have a problem understanding the fairly small cavities; are those based on calculations or practical experience? Or mainly for weight reduction?

 

[Erik Hauri]

Those cavities are the cutouts for the sound holes in the top - the chamber underneath will be much larger. We will also chamber the treble side, still trying to decide how much.

This week I am in Oregon for a conference, but had a free day to drop by Gilmer Hardwoods in Portland to pick up the Madagascar ebony for Ben's fretboard. Gilmer has been in Portland for ~25 years, and Jim MacDermott at the warehouse was very helpful in guiding me to exactly what I needed - a solid straight quartersawn piece that is black as night.

 

[Fred]

Sweet jeebus this is going to be a good looking guitar, looking forward to more updates!

 

[Apophis]

Cool project

 

[MF_Kitten]

this is going to be cool, and that is some black ebony!

 

[Mundas]

Nice looking project

 

[hairychris]

That walnut top =

 

[TheSixthWheel]

Looks fantastic. Is it just the photo or is that Gilmer building far from straight and level...in a fantastically skewed way. I'm a fan of observing the effect gravity has on things over the years.

 

[Erik Hauri]

Yeah the Gilmer building has clearly been there awhile, at least 22 years in that location they say. It is funny, the white sign points you to the front door, and on the front door is a sign that says "<---- Use other door"

The place is stacked floor to ceiling and 2 pallets deep with every kind of wood imaginable, and another stash stored outside wrapped in tarps. In one way it is very disorganized since they do not sort their wood by species - but everything they have for sale has been trimmed, planed and/or sanded S2S, then sealed in a thin layer of shellac - then each piece has a unique ID number like they list on the website and is stuck on a shelf. So if you're looking for a specific kind of wood, you have to pick through the shelves to find it.

I think it would be tough to buy stuff in the rough like I usually do - and I think this is why you pay a little bit more at Gilmer, because of the work already put into each piece.

 

[Elysian]

Yeah the Gilmer building has clearly been there awhile, at least 22 years in that location they say. It is funny, the white sign points you to the front door, and on the front door is a sign that says "<---- Use other door"

The place is stacked floor to ceiling and 2 pallets deep with every kind of wood imaginable, and another stash stored outside wrapped in tarps. In one way it is very disorganized since they do not sort their wood by species - but everything they have for sale has been trimmed, planed and/or sanded S2S, then sealed in a thin layer of shellac - then each piece has a unique ID number like they list on the website and is stuck on a shelf. So if you're looking for a specific kind of wood, you have to pick through the shelves to find it.

I think it would be tough to buy stuff in the rough like I usually do - and I think this is why you pay a little bit more at Gilmer, because of the work already put into each piece.

I <3 Gilmer Woods. Marc Culbertson is the guy I always go through when I call in an order there, he's just a cool guy all around, even has a UV777BK now, getting into 7's. I'd love to be able to go to the shop some day, maybe if I go visit my sister in WA I will.

 

[Erik Hauri]

Lots of progress today - routed for the truss rod (Allied), I like to rout after installing the CF bars so that I don't have to have 3 open routs side-by-side with thin walls between (increasing chances for blow-out).

I cut the scarf joint, then brandsawed the neck taper (just outside the line) and routed the final taper using my trusty neck-taper template. If the neck I'm working on doesn't fit an existing template, then I will make a new one from 3/4" (which I did for this build). I double-stick the neck onto the top of the neck-taper template then rout the edges using a pattern-following bit with shaft bearing.

I glued the scarf with the joint within the headstock rather than underneath the fretboard - tape front & back to hold the piece in place, then clamp with a flat caul on the front. The clamps help to keep the tape from slipping on both sides and effectively squeeze the joint tightly. Once I add the side-ears, headstock lam and backstrap the joint will be invisible.

The Madagascar ebony fretboard will have "integral binding" which is binding of the same wood made from off-cuts of the board sliced off after cutting the taper.

I cut the taper - and trued up the edges on the jointer - so that the cut is directly underneath the outermost strings (so that the scale is accurate when I slot the board). The edges of the offcuts were trued up by sanding on a flat marble door threshold (c/o Home Depot).

I print the fret layout from CAD (using "hairline" mode so the fret lines are very narrow), stick it to the fretboard, and cut the slots on the radial arm saw.

After all the slots are cut, I'll go back and enlarge the nut slot.

Then the offcuts are glued back onto the board and clamped - I'm using epoxy (West System) in this case, apply to the offcuts, let it sit for 30 minutes to tack up, then clamp. I like it better than Titebond for ebony.

Another 30 minutes later, I go back and clean out the slots while the epoxy is still soft.

Today I also started laminating the walnut top & back to the underlying wenge accent - I started with a 1"+ thick piece about 12" wide, resawed it into two 1/2" thick pieces, planed them flat, then glued a top (or back) panel to both sides, and clamped the whole works in the press with a big piece of limba as a caul.

Once the sandwiches are dry, I will trim them and resaw them again to yield a thin veneer of wenge underneath the walnut top & back plates.

 

[Empryrean]

looks to be coming together quite well

 

[Hollowway]

Very nice! It is a shame you don't have any tools though.
I'ma break in there and build myself something when you're asleep!

 

[Andrew_B]

where did that bench mounted clamp (in the last pic) come from?
i wouldnt mind getting my hands on one of them lol...

the integral binding idea is sweet, takamine uses it on some of their acoustics...

its coming along nice, keep the updates coming

 

[Erik Hauri]

I'ma break in there and build myself something when you're asleep!

Well the bedroom is right above the garage/shop, so as long as you don't fire up the compressor or the dust collector, you should be good to go!

Yeah, that press clamp is true - I got it here:
H5510 Shop Fox® Deluxe Press Clamp

 

[thinkpad20]

Awesome, dude... your hand-made multi-scale bridge has convinced me to get one on the one I've got planned... major props, you've got skills and creativity out the wazoo!

 

[HighGain510]

That is shaping up nicely, love the walnut top too!