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Acoustic #3: Walnut/wrc Jumbo

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Figured I'd start a place to dump some details on my latest (and greatest!) project.

Rundown of the specs:

- Jumbo body, 16.6" across the lower bout (nod to Kevin Ryan in terms of general dimensions)

- Black Walnut back/sides

- Western Red Cedar top (slight bearclaw, I think)

- Laminated neck (walnut/wenge/maple/wenge/walnut), scarfed, front and back veneers, floating supported fingerboard extension

- Ebony fingerboard, fancy schmancy vine inlay

- Spalt maple rosette with abalone trime, abalone purfling around the top

- Adirondack bracing, trad X on the top, doulbe X on the back, all X braces reinforced with CF (0.02" laminate)

- Adjustable neck joint, a la Doolin/Fleischman/Turner

- Flying buttress CF braces for the headblock to free upper bout

- Sound port, upper bout, bass side

- Wedged body (a la Manzer/Cumpiano)

I think that's about it. Progress so far:

Design: complete. Earlier sketch of the inlay design here:


Body: most remains to be done, but it'll be the faster bit once all the pieces are made. Wood selected, back and top jointed, top initally thinned (handplane). Strips for lining cut, need further processing, strips of spruce for bracing cut, need to be laminated with some CF and polyurethane glue (or maybe thick CA...). Waiting to see if I can find time to go use a thickness sander, since I haven't had the time to make my own yet. Have the parts, but no time, and I want/need to get this guitar done by October. Shot of back (before joining, is now cut to shape):


Neck: more work done here. Laminated up the blank, cut the scarf joint, glued said scarf joint, routed an initial 1.5 degree angle onto the face of the heel, glued in the extension, rough-carved the neck, routed for CF bars and truss rod, did the headstock veneer and backstrap, routed the headstock shape, routed for headstock binding (not glued yet), radiussed and slotted the ebony board and bound said board in flamed maple with a contrasting b/w/b line of purfling under the veneer. Pics:










...that was pretty much it. I'll update as I can/see fit/bother to take photographs, but I'm mostly concerned with getting things built a little sooner rather than later.

Edited by Setch
Fixing html tags which screwed with the PBcode.
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Thanks guys!

Rich: it's loosley modelled after a Ryan Cathedral (in case that wasn't clear), so I'm more or less sticking to his dimensions. Depth at tail will be 4.75", head 3.75", side to side taper of 1.5" (subtract 3/4" from the bass side, add to treble, same net volume, much 'smaller' feel), which, if I did my measuring right, means the widest point will be 3.75" deep at the bass side.

Preston: fingerboard binding is just glued on. Titebond for the side strips (superglue gets into slots much faster, and is more of a pain to clean out), thick superglue for the mitred end piece, because I've had failures gluing wood to ebony end-grain before. I pre-glued the purfling strip to the binding with a bit of titebond original, held in place with some masking tape (didn't feel like devising some complex jig to hold it together). Since the binding's so thin, and the bends are minimal (a few seconds on the 'pipe', ie rolling pin with heat blanket bent over it, dry, and it's bent), there's no risk of the purfling delaminating. This is the first time I add a contrasting purfling to the bottom, and it's a little more involved in terms of headstock binding (adding a fingerboard stop, etc. as described in Benedetto's archtop book), but not hugely so.

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Looks great so far!

Neck joint; butt joint, right? Are you going to butt up flush against the end of the body, or try to recess it?

Can you still tweek the neck angle with the fretboard extension already on?

Recessed butt, because it'll have to move. I figure it'll be fiddly, but as long as any gap's even all the way around, I'm OK with it. Have templates for the heel profile made (MDF) which I'll copy with the inlay router kit to get a perfect male/female set. I can actually still tweak the neck angle with a router with the extension already on (I have a frighteningly long 1/2" straight router bit. Oh yes. Shall be using it to glue a cross-grained fillet for the inserts, and have an alignment jig for routing this kind of nonsese built as well), but I'm not sure I'll bother routing more into the heel, precisely because it's recessed and will be tilting a little in some direction or other. That's sort of the point of a hardware adjustable neck joint :D

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  • 2 months later...

Brief update - pics to follow at some point this week - work is progressing, albeit a little slower than I'd like it to (the usual, in other words). Pesky internships! In the meantime, I got myself a thickness sander (worth every. single. penny) and a belt/disc combo (small, cheap, bigger would be better, but it's already paid for itself, all 90 bucks, as far as I'm concerned).

This weekend, I did the following: finally finished the bending form (7 plys of MDF, glued together with poly, flush trim after each layer), made a Doolin-style bender base, cut .4mm spring steel slats to length, folded over the end, riveted, applied springs, screwed them to the base. Still need to make the head end of the bender (spring mounting), and figure out an elegant way to mount the form to the base to make it easily interchangeable, but it took surprisingly little time. Spent about an hour making an accurate, properly fitting 'shoe' for the waist of the bender and shaped spreaders (waist, lower bout) for the building mold out of basswood (cheap, easy to carve, lying around doing not very much at all). Basic design is like this, although I'm being cheap/can't find the destaco clamps, so I made cutouts at the butt and head so I can use regular clamps to fix the two ends.


In more building-related activities, I built an adjustable router base for doing a rosette with some scrap swamp ash (didn't have and couldn't find the required 3/4" thick UHMW plastic, nobody here stocks the stuff, anywhere), following Sylvan Well's instructions. Took an hour or two of work in an evening, used brass rod for the straight bits, tapped the wood, hardened with CA, then re-tapped, works perfectly and allows carefully widening a rosette channel until everything just fits perfectly. All that's left to do for me is toe file and mitre the abalone pieces for the inner and outer rosette rings, pop it all into place, and glue with CA (sealed with shellac already, of course). pics when it's done.

Router base I'm talking about:


I also laminated 3 X-braces, Spruce/.02"CF/Spruce, total thickness 7mm, glued with hot hide. 2 for the back, one for the top, still need to sand the rest of the bracing stock down to size, but that's not going to take more than 10 minutes, really. Made a laminated end block (three layers of african mahogany, sort of a 'thick plywood', 3/4" total thickness, headblock with an angled, tilted spanish foot to deal with the lateral and lengthwise tapering of about the same thickness (I don't see the point of a 1"-1.5" thick large headblock if it's reinforced with CF flying buttresses and accomodates a butt-jointed neck, recessed more or less to the depth of the sides).

As said, pictures to follow later, probably once the sides are bent (plan: bend side 1 today, re-heat, cycle temp, let cool, side 2 tomorrow).

Edited by Mattia
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  • 3 weeks later...

Few pictures after a lovely, long week of vacation and a hellish week of taking on too much work at the side. Bender's slated for completion some time tomorrow afternoon, hopefully be doing a test bend then as well, and hopefully I'll get around to starting work on the binding routing jig setup over the course of the next week.

Anyway, some bad quality pics of the rosette cutter, cutting out the spalt maple rosette ring:


Next up, the actual rosette being assembled. It's spalted maple with inner and outer rings of b/w/b - abalone - b/w/b purfling, very fine line, thin purfling. It was surprisingly painless work, overall, although the inner ring required quite a bit of snapping of pieces to get it all to fit the curve. Beyond that, it's easy to hide joints in abalone, and any well-fitted 'cracks' look like natural lines. Took me about an hour or so to get all the pieces fitted (very, very snug), pushed down, and then flooded the lot (after having sealed with 3 coats of shellac a few days ago, I might add) with thin CA. Currently letting it all dry overnight, and I'll run it through the thickness sander tomorrow. The Abalone is pretty much flush with the top, but the maple's a little proud, ditto purflings. Once I'm close, I'll switch to hand sanding with a block (220 grit), then flip over the top and finish thickness-sand to thickness (3.2mm in the middle, an even 1/8"). I'll thin out wards towards the edges with a handplane at a later point in time.

Assembly of the rosette pieces:


Rosette post-flooding with CA. Sorry about the poor quality shots, I'll get the DSLR and the macro lens out tomorrow, honest.


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  • 8 months later...

Right. Testament to my 'stop and go' building, this one (along with 6 other projects, but two others in particular) has been fast tracked, and if all goes well shall be entering the finishing shed (ie, the covered bit next to the shed, if it's not raining) this weekend. Hopefully I should get the finish sanding and machining done on the body by the end of the week. The neck's getting a tru-oil and/or shellac finish, so doesn't need to be prepped quite as soon, which is a good thing since inlay is slated for next week (lots of fiddly bits).

Anyway, since last we checked in (and only from about two weeks ago or so) I've bent the sides in my shiny new Doolin-style bender (works GREAT), laminated glued on the braces, carved them down to shape, done a little bit of Chladni pattern tuning with tea leaves. That helped me realise that yes, I needed to remove MORE MASS once I already had what I thought was nice tap tone - ring and a half came in at around 245 hz for both top and back. Didn't take pictures of the finished free plate mode, sadly. Well, I did, but the memory card wasn't in the camera, which is, y'know, not so handy. Oops. I glued the top and back on yesterday, trimmed the overhang and did a little sanding today, and drilled the 30mm side port in the side. Really funny to hear, as the helmholtz resonance rises by about half a step (roughly from G to G# on the low E...low Helmholtz, that) by simply covering the hole with my hand. The whole body rings out wonderfully, and the top and back resonances are almost the same - which is where I want them before I glue on the bridge and have the resonance on the top drop. I have a good feeling about this one!

Anyway, some pics. Not of everything, as I am lazy that way, but more pics will come soon.

First up, the back, braced, braces rough sanded, and the shaping tools - nice Blue Spruce paring chisels, low angle block plane, finger planes, 2 cherries chisel to 'sacrifice' on the CF braces. Damn stuff put a dent in the blade, will have to re-grind the bevel.


The top, bracing in the rough. The bridge plate is laminated, EIR and Maple, mostly because I figured 'why not', and because the EIR headplate scrap I had was too thin otherwise. Comes in at about .080-.085. The spruce patch between the A brace bits is there for reinforcement once the floating extension bit gets fitted - glued cross-grain, I'm hoping it'll prevent any cracks that might feel inclined to form.


Posed shot - semi-carved bracing on both top and back, rough fitted to rims, posed against our shiny, shiny new paino. German made (in the 1950's), solid Walnut with bookmatched flamed euro walnut veneers all around. And it sounds even nicer than it looks.


Shot of the rims and the back. Few things to note: reverse kerfed lining, spruce side braces tucked into the lining (not butted), and of course larger sapele side braces with 1/4" CF tubes as 'flying buttresses', and a spanish foot. Angled to fit the wedged body shape:


...The aforementioned Wedge. This body's flippin' HUGE, by the by, about 5" deep at the lower bout, treble side. more manageble 4" at the bass side, which is the point of the exercise.


The top, braces close to done. When I was finished I'd taken off a good bit of width from the lower X brace legs, a little height off of the X and both tone bars (minimal, 1mm or less, mostly near the edges, feathering them out smoothly), tapered/feathered all of the upper bout brace ends to almost nothing (with the CF flying buttresses, I'm shooting for an 'active' upper bout which doesn't need to take up quite so much string strain), and made the fingers lower and narrower in cross-section.


...and that's all for now. Right now I'm fiddling about with the end graft, getting that to fit nice and snug. I really should build a jig for that eventually, I suppose, although given that it doesn't take that long to do by hand, I'm not sure I ever will...

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All looking great Mattia!

Do you have a picture of the top when you'd finished all your carving? In the picture posted it still looks a little weighty to me. What strings will you be using on this baby?

RE: end grafts. I was in the same boat as you when it comes to these, having done straight sided ones it takes so little time by hand I didn't see the point in jigging up! On my latest instrument I've done a curved sided one, and though it's still possible by hand of course I gave in and sorted a template for the router. Looks beautiful, and I won't be going back to the straight ones.

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All looking great Mattia!

Do you have a picture of the top when you'd finished all your carving? In the picture posted it still looks a little weighty to me. What strings will you be using on this baby?

RE: end grafts. I was in the same boat as you when it comes to these, having done straight sided ones it takes so little time by hand I didn't see the point in jigging up! On my latest instrument I've done a curved sided one, and though it's still possible by hand of course I gave in and sorted a template for the router. Looks beautiful, and I won't be going back to the straight ones.

Just checked the camera - I'm a moron, and don't have pics of the finalized bracing. Too excited about closing the darn box! I'll try to get some shots through the side sound hole sometime tomorrow.

The final product has more dramatic tapers on the lower X legs (more even/flatter down to the ends), deeper tapers/feathering, pretty much all the braces are narrower in cross section (the X is only 7mm wide, all the other braces 6mm, except for the upper transverse which is 7 again, and that pic has a lower bout width, with the overhang, of easily 18"!), the tone bars are lower (max height 11-12mm, more pronounced taper towards the ends), the fingers are lower, narrower and more profiled (at least half the mass they have in the pics up there). Probably could've gone with more, but I want the guitar to be able to bear at least 12s, possibly 13s, and it is Cedar, not Spruce, so I'm not going to push quite so hard.

As far as grafts go, I'm sticking to an even taper for this design; I sketched some curved grafts, but none looked quite 'right' in combination with the massive wedge going on - need to sit down and draw out some more options before deciding, and in part I'm on a tight schedule - this baby should be finished by early August. 2 more weeks. I do have that brass inlay kit (for PC style routers) which makes it dead easy to make nice matching parts for things with a single template. Will be using that.

Edited by Mattia
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Right, a few piccies! Closed the box a while back, installed the graft, and today I got around to finish sanding the entire box and giving it a coat of sealer (shellac for the top) and grain fill/sealer (Z-poxy on back and sides) before I route the binding channels tomorrow evening and spend some quality time with a file and a bag of paua purfling strips (for the top). The idea was to protect everything from superglue drips that may occur when gluing binding. Will need to scuff sand these surfaces anyway and re-apply sealer/second coat of z-poxy for pore filling anyway, so I figured I'd protect the wood from glue and grubby fingers and get a leg up on the finishing process, which I hope to complete this weekend. Will be shaping the heel and fitting the neck joint before the next coats go on. Neck's probably getting an epoxy seal coat (even colour) and tru-oil on top of that.

Anyway, enough yakking. Pictures!

Gratuitous shot through the side sound hole:


The guitar, avec side sound hole, in its pre-sealing stage, sanded to 220 grit with the festool ROS. Lovely smooth result:


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The top, shellaced (super blonde, will add a coat of blonde for colour, I think)


Gratuitous closeup of shellaced rosette. Shiny!


The back after a single coat of Z-poxy finishing resin. Really love this stuff, and acoustics are so much easier to finish than electrics. None of that annoying end grain to deal with!


Extra shot, guitar, indoors, perched on a glass, drying overnight. More work tomorrow, hope to spray on Saturday (weather permitting).

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So your going with no binding on this one? Thats interesting.

It's looking good, I like your "player" sound hole. :D

No no, re-read a post or two up - these seal coats need sanding and a reapplication in some areas anyway, so I figured I'd protect the wood now, then route for binding (maple with black/maple/black side and back purflings, black/maple/black - paua -black/maple/black top), glue it with CA (this helps prevent any small drips and runs from making the wood look nasty/making a mess), route the shallow pocket for the adjustable neck joint, then apply the final sealer/filler coats.

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