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The Marmoset
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Author:  DennisK [ Thu Jan 19, 2012 10:12 pm ]
Post subject:  The Marmoset

All y'all are getting so far ahead of me while I finish up my previous projects, I'm jealous. Gotta get my thread opened at least :)

My plan is a steel string harp ukulele, in redwood and walnut.

Here is the current design, subject to change.

The design and name is based on my upcoming harp guitar build called "The Monkey", using redwood and monkeypod. This is the miniature version, for practice :)

The drawing is at 24 pixels per inch, so overall length is about 23 1/2", and lower bout width 9 1/4". Scale length on the 4 neck strings fans from 14 3/4" to 15 1/4", followed by 4 harp strings 16 1/2" to 19 3/4". Tuning will be, from low harp string to top neck string, C, D, E, F, G, B, E, A.

I'm debating between using the geared Grover tuners on StewMac, or wood friction pegs. I already bought the Grovers, but the gears are a little floppy, and they're a little heavy, and a little big, so I may return them. This thing is already doomed to being neck heavy, and another 150g out there versus 50g for the pegs might be too annoying. But even floppy gears work better than friction pegs, especially on steel strings. Plus I'm worried the pegs will slip, with the harp strings whipping on them directly. I suppose I could add something akin to a nut for the harp strings to vibrate against, to isolate the tuners, but I hate to take away some of their scale length. Also, I'm not sure exactly how much tension I need on steel strings this short... I'm thinking around 15-20lbs per string should be enough to feel nice and tight. May need to do some testing to see how different tensions feel.

Here are the main woods. I didn't fish out the sides from my wood tower, but they pretty much look like the back except longer and not as wide.



Redwood is of course a pretty long distance from a real back yard build, but this set seems well suited to it, and there aren't any really good top woods native to this area. I of course dabble in hardwood tops, but for coaxing deep and rich tones out of a tiny box, and to not be so monotone as if I used a walnut top too, I'd rather use my favorite softwood. Plus it matches the Monkey harp guitar.

Black walnut is one of the most common trees in the area, so no trouble there. I'm not sure where the tree of my back/side set grew, but the neck is likely to be actual local, as I bought it at a hardwood store in town. Might not be able to avoid that knot, but I got another similar piece with no knots that I can use if that's the case. Not bad at a couple bucks each :)

The bridge is pecan from Ernie, who I believe said it came from his neighbor's yard, so most certainly local :) Should look nice against the dark redwood.

Fingerboard will be osage orange if I can find a good piece and get it dry in time. Otherwise I might have to cheat and use Indian rosewood or something else that I have on hand. I know, I could use maple... I just don't like the look of maple fingerboards on acoustics, especially with dark tops. I'd rather be DQ'd than make an instrument I'm not completely happy with.

Binding will be black cherry, cut from that 1/4" thick plank in the neck wood shot.

Other materials will be black locust, quilted bigleaf maple, a bit of koa inlay, and green abalone headstock logo.

Author:  Chris Pile [ Fri Jan 20, 2012 12:14 am ]
Post subject:  Re: The Marmoset

I LOVE the name!
When it's all done, the player can say to an unsuspecting audience, "Hang on while I whip out my MARMOSET!".
And then lay down some dulcet toneage, thus mesmerizing them....

Author:  WudWerkr [ Fri Jan 20, 2012 10:13 am ]
Post subject:  Re: The Marmoset

Love the design Dennis , Looking forward to seeing this one finished.

Author:  DennisK [ Mon Jan 30, 2012 5:50 am ]
Post subject:  Re: The Marmoset

While waiting for the fingerboard to dry on my coral snake build, I decided to do a little work on this baby. Joined up the plates, and drew the full size template. Lots of measurements, then some freehanding the curves, and it looks pretty much just like the computer version. I added a tree inlay on the headstock, although I may change it. I was thinking green abalone leaves, but then it occurred to me that's what I was planning to use for the D, since it's from the US west coast, whereas my usual paua is from New Zealand... so the leaves and logo may clash, being so close together.



Author:  DennisK [ Sun Feb 05, 2012 8:07 am ]
Post subject:  Re: The Marmoset

Ok, into full production on this! Scraped the soundboard smooth on the face, and thinned it down some from the back. Now it's rosette time, before completing the thinning (this way I don't have to worry about denting up the back side of it while working on the rosette).

But first, I needed some cherry for the vines. I bought a 1/4" thick board from a local hardwood store for bindings and inlay. Fortunately it's not too hard, so ripping bindings by hand only takes a few minutes per strip (on the other hand harder would be better for when I inevitably bash it into something and dent the binding...). Cut those first, then cut a little rectangle for the inlays. Since I only need about 1/16" thick, I decided to slice it in half instead of just thinning it down... have a spare for later, and not that much more work than thinning it anyway.

Saw this side, saw the other side, and split the remaining bit in the center by chisel. Clean up the faces, draw all the vine segments on one, and get cutting.

My inlay method here is highly imprecise, just copying each piece visually from the original design, drawing onto the wood in pencil. But with simple designs like this, it works just fine.

While working on inlaying the vines, I also cut the two marmosets for this and the harp arm soundhole. First I doodled them on the woods (curly koa and curly hard maple), and then cut out little light colored faces for them from a bit of mulberry sapwood (maple would work just fine, but I don't have any pieces that are thin, white, and straight grained, and this is local cut so good for the challenge theme).

I could cut out the body shapes, inlay them into the soundboard, and then inlay the faces into that, but it works better to inlay the faces before cutting out the bodies so I can shape the heads around them.

When cutting the white monkey, I had to be very careful not to break the tail. Cut it by going about half an inch on one side of it, then half an inch on the other side, so I was always cutting near a good solid connection with no major leverage to break it.

Getting back to the vines, the first step is to score around all the pieces. This design uses a fair amount of layering, where I have to inlay the pieces in a certain order because they cut into eachother a bit to get tight seams without the effort of careful fitting :) Since the most critical piece is the one that fits in the corner of the soundhole and fingerboard, going slightly behind the fingerboard to complete the endgrain sealing role of the rosette, I stuck it down first. Also stuck down the first piece of the vine fluff above the monkey's head because it doesn't have to fit tightly against the other. There's a gap that will be covered by the monkey's arm in the end.

After scoring around those pieces, pull them up, glue down the next ones in order, score those, pull them, glue the next... can't be done quickly since the glue takes time to dry, but I was working on the monkeys at the same time so no downtime. Finally when all scored, start by routing for the back-most pieces in the layering order, as well as doing the all the pointy tips at once to avoid having to change bits on every piece.

Then glue those, level them, and route the next (cutting the corners off the previously inlaid ones). Leveling is done with a chisel to get close, and then super fine shavings with a little plane until flush.

And one more round, routed, glued, leveled, and marmosets in place:

Next up I'll do the leaves on the vines, eyes and ears on the marmosets, and then it's onto final thinning of all the plates :)

Author:  Chris Pile [ Sun Feb 05, 2012 8:52 am ]
Post subject:  Re: The Marmoset

Looking good!

Author:  truckjohn [ Sun Feb 05, 2012 9:01 am ]
Post subject:  Re: The Marmoset


I can't even inlay a square into a square hole without making a mess of it... Impressive!


Author:  alan stassforth [ Sun Feb 12, 2012 9:16 pm ]
Post subject:  Re: The Marmoset

I really like your animals as rosettes themes, Dennis!

Author:  alan stassforth [ Mon Feb 13, 2012 9:30 pm ]
Post subject:  Re: The Marmoset

It's not sick,
IT'S ALIVE!!!!!!!!!!!!!!!!!!
( "Young Frankenstein", quote).

Author:  DennisK [ Sun Mar 04, 2012 9:08 pm ]
Post subject:  Re: The Marmoset

It's been so long since I updated this, I'm almost down to page 2! The shame!

I've been working on other projects, but it's back to this one now. Clock's ticking on getting the box closed up before the humidity skyrockets for the summer. I should have another month or so, but the winter has been mild, and there have been some good thunderstorms already, so who knows.

Anyway, yesterday's task was to construct the neck blank. But in order to do that, I had to make up my mind on what tuners to use. I've decided to skip both of the previous options, and go with planetary gear pegs. They're only a tiny bit heavier than wood pegs, and should be much less annoying to deal with. This does put me well over the price limit ($140 for the tuners). Technically I could use wood pegs for the competition and then swap out afterward, but I figure why bother, especially when those pegs would be in violation of the rules too, since LMI only carries rosewood and ebony, and I definitely don't care enough to buy a mini-lathe to turn my own.

Unfortunately, the planetary pegs come in 2L/2R packs for violins, and with the harp head needing 4 lefts, that leaves 4 rights to use on the neck headstock... which in the current design is 2L/2R. Three directions to go here:
1) Use all the left pegs on the harp headstock and one set of Grovers on the neck
2) Use all the left Grovers on the harp headstock and one set of pegs on the neck
3) Redesign the neck headstock to use 4 right pegs

1 is no good, because that leaves me with 4 expensive pegs that have no future in mind. 2 is better, but it is still heavier than all pegs, and puts the weight up high where it would make the whole instrument more tippy and annoying to hold. However, it would provide a possibility of keeping in the price limit even with one set of planetary pegs. But I'd have to find a cheaper back/side set. So... I'm going with 3. Here's the new design:

It will have a fairly thick headplate (maybe 1/10") to allow for carving of the spiral. Edges will be heavily rounded, which will look awesome with the tree inlay getting right near the edge like that. No room for my abalone D logo, but who needs that when you've got something as unique as this :D Still debating on the color scheme with the woods I have available.

So, with the tuner issue dealt with, I went ahead with all the sawing and planing and gluing to make the neck blank. I wasn't in much of a thorough documenting mood, so I just went at it. Pretty typical stuff, except for a couple things:
1) I wasn't sure what normal neck thickness for an ukulele should be, so I decided about 3/4" total thickness including fingerboard at the nut, and about 1/16" more at the 10th fret ought to be reasonably comfortable and strong enough to handle 4 strings over such a short span. Considering adding a carbon fiber bar just to be safe though.
2) I've never done a fan fret before. I'm not sure how most people angle their headstocks for it, but how I did it was to cut and laminate the scarf joint square, but with the headstock a fair bit thicker than necessary, and then mark the angled nut line on it and chisel/plane until I "tilted" the surface to reach it. Here's how it ended up looking:


I'll have to carve at the back of it to complete the tilting operation, but currently you can see how much off level it is by the thickness difference at the end.

Then glue on the heel block. This is an integral neck, with tongue extending to the upper transverse brace (not very far, actually). I carved away some of the excess heel block before gluing it on, just cause it's easier to do when it's separate. Not the best photo... it's sort of rounded, and follows the angle of the sides in the neck joint area.

Next up, cutting the taper, and the slots for the sides to insert into, carving the heel, and all the headstock work.

EDIT: Oh, I almost forgot... here are the finished rosettes. I normally use black MOP for eyes like this, but since it's from Tahiti, and 2mm dots would be a little big anyway, I decided to try an experiment... drill 1/16" holes, paint them black inside, and then fill with hide glue and scrape flush. Worked pretty well, actually.
The white marmoset has one slightly buggy eye due to the drill bit wandering, despite my efforts to prevent that from happening... need a 1/16" brad point bit.


Author:  DennisK [ Sun Apr 08, 2012 2:46 am ]
Post subject:  Re: The Marmoset

Well I haven't been keeping this thing up to date, and I'm still far from done, but I have made a fair bit more progress.

First of all, cut out the top. This is one of the convenient things about working with redwood, it's soft enough to do this with an x-acto knife instead of the coping saw. Quick and easy.

Then getting back to the neck, and more specifically the headplate... I decided to go with bookmatched black locust, with a black walnut tree inlay with green abalone leaves. A bit of hand saw slicing to cut the headplate, and chiseling and scraping to thin it down and flatten it out, and then glue it on.

Drill and ream out the tuning peg holes.

Then the inlay. More manual slicing to get a piece of walnut off one of the neck offcuts, since I liked the color better than the back and side material. Also, I tried a fun techno-technique for transferring the design onto the wood for cutting. Doodle the inlay on the headstock itself, then hold it down to the printer-scanner and hit the copy button :) Then cut the paper pieces out with a knife and glue them on the walnut slice.

Not to self: Make a better inlay cutting table.

Then temporarily glue the pieces down to the headstock and score around them, starting with the base of the tree and working my way up to make sure they all line up with eachother and the bottom edge of the headplate. Then I'll route and inlay starting with the smallest branches and working my way down, layering the pieces to save the trouble of fitting them to eachother perfectly. One of the convenient things about wood inlays as opposed to shell.

Then cut the neck taper and headstock shape...

Then it seems I forgot to take pictures for a while again... did lots of measuring to figure where the slots in the neck/headblock for the sides to slide into should be, to point it toward the eventual bridge location. Unfortunately, due to poor comprehension of the 3 dimensional shape of the heel, I cut the slots starting from the correct locations, but at slightly wrong angles. In order to create the nice continuous curve from harp arm to cutway that I wanted, the slots needed to be angled identically, but following a different train of thought, I cut them at shallower angles. Probably would have been better to do a bolt-on neck for the design I had in mind anyway, but this situation just needed a minor design adjustment, making the heel cap wider so the angles don't progress as far inward there, and carving the heel to disguise the discontinuity. Hard to describe, but I'll post pictures later on. I think it'll look great.

Anyway, after getting the neck rotation established, and thus the angle of the upper transverse brace, I could lay out the top bracing pattern. Pretty standard X bracing, shifted and shimmied to fit the asymmetrical body shape and large fan fret bridge. I also decided to go with 3 fan braces in the lower bout, rather than the usual diagonal bars. Those things never have really made sense to me in terms of supporting the bridge. I thought about just adding a third diagonal bar going the opposite angle to form a sort of lattice, but there just isn't enough room between the bass end of the bridge and the perimeter for it to be ideal. The 3 fan arrangement is a bit risky though, as the braces run between bridge pins. I'll glue the bridge and drill the holes before I close up the box, just incase I messed anything up and hit one of the braces.

Took this picture before the X cap was fully dry, but rest assured it's carved nice and smooth now.

More two write, but I think that'll do for tonight.

Author:  WudWerkr [ Sun Apr 08, 2012 8:25 am ]
Post subject:  Re: The Marmoset

Great looking work Dennis , Win or Not you are going to have a build to be plenty proud of ! [:Y:]

Author:  DennisK [ Mon Apr 09, 2012 6:38 pm ]
Post subject:  Re: The Marmoset

WudWerkr wrote:
Great looking work Dennis , Win or Not you are going to have a build to be plenty proud of ! [:Y:]

Thanks Jim! That's the idea. I'm really quite curious what it will sound like :)

So, next thing I decided to do was make the fingerboard, just to be sure it fits the neck before I go gluing the neck to the top. No shots of the process, but it didn't look especially different than what I do for parallel frets, which is to make 3 sets of marks for maximum accuracy, then saw the slots one by one using a wood block clamped at the marks to guide the saw. Only difference this time is that each set of marks was spaced differently, and that the outer sets had to be made exactly along the paths of the outer strings, rather than right at the edge of the board or closer to the center or whatever. Then the center marks I did with 15" scale (half way between the 15.25" bass and 14.75" treble scales).

The board is Texas ebony, from Dave Newton. I was originally planning to use osage orange, but never ran across any. Glad for it, because this is even better :D I prefer when the fingerboard is darker than the top. Bindings are black cherry.

Also, here's a shot of the rosette after shellacking the top. The curly koa is gorgeous, very fur-like.

Then it was on to final neck carving, and making the harp arm headstock and the tailblock. Again, was too much "in the zone" and/or lazy to take pictures until things were finished. Here are some shots of everything done and shellacked and glued to the top.


Unfortunately, I forgot that I was supposed to cut and inlay the abalone tree leaves before gluing the neck to the top, because it would be a lot easier without the harp arm in the way. Oh well, I'll deal with that after I get the box closed up. Good humidity this week, so I shouldn't be spending time on little fiddly things like that anyway.

Then dentellon manufacturing. Saw, split, sand, saw, split, sand. Made from one of the top offcuts.

You can also see the unbent sides in that shot, which the next step was to bend... again without pictures. My bending iron is a 3" diameter scrap of exhaust pipe with a few holes drilled in it to mount to a piece of wood with L brackets, and electric charcoal starter for heat, which is run through a dimmer switch for temp control. I really need a smaller iron for things like this. Bending the treble side waist was tough, and didn't even get as tight as I wanted it. Bit of scorching too, but I think it will scrape out. The rest of the bending went very smoothly. Walnut is indeed bend friendly, especially since it's not interlocked grain, so it doesn't ripple up like mahogany and rosewoods tend to.

Also during the bending I was trimming the sides to length, which I do with a little razor saw. The harp arm ended up being a bit narrower than the plan, but it looks good and the soundhole in it is still centered, so I didn't bother adjusting the bend. Did carve the braces a bit more before gluing the sides to it though.

Assembly goes fairly slowly, gluing one side to the tail block at a time, and the other sides into the neck slots.

Then one side to the harp arm headstock, just cause I might as well. Other side stays loose for the moment. Gotta get its waist location set and glued down with a few dentellones before sticking it to the harp arm headstock.

Next time, gluing the cutaway tip... my miter came out great. I wasn't expecting to get both lines so perfectly vertical and well mated, and figured I'd end up having to bind it. But I think it looks better without binding on the tip, so I'm happy.

Author:  DennisK [ Wed Apr 11, 2012 7:48 pm ]
Post subject:  Re: The Marmoset

As promised, next step is to glue the cutaway. You may be wondering, how do you glue a cutaway from that state I had it in last time? I'm not sure if this qualifies for "doofus move of the month" since it was a complete success, but I'm pretty sure only a true doofus would attempt such a move in the first place :lol:

The technique is simple: hold it until it dries. Set up a 30 minute playlist, put on your headphones, slather the thing in hide glue, index fingers down the outside, thumbs holding the corner block in place, and try not to move. This involved flexing the sides a bit to get the tip together, so any slip and it would peel itself apart.

Around 25 minutes or so, I decided it felt good enough that I could let go of the short side, freeing one hand to start sticking some dentellones in. After another 10 minutes or so for those to dry, it was plenty sturdy to let go.


After a little warm water cleanup, and it looks great. There's a tiny gap in the miter where the sides meet the top where you can see some glue. No structural concern, but doesn't look absolutely perfect. I think it's good enough to leave unbound though.

Next time I think I'll do it the "right" way, gluing the tip before gluing the sides to the top. I did it this way because of the bends there being not quite as tight as the plan, so I wasn't confident that I had the meeting angle of the point just right. It would have taken at least just as much time to make a caul to glue it separately anyway (which I'm not sure I'd ever get the chance to reuse), and may have resulted in more tension and possibly the waist being farther out of position.

Then lots more dentellones:

And then leveling the rim. Normally I aim to get the whole thing level but a bit higher than the neck and tail blocks, then mark a line all the way around for reference, and plane it level with the blocks, but leave it high at the waist, as it would be if sanded in a radius dish. This time I ended up going all the way to the blocks before I got it flat. Oh well, the top is an arched plate stretched onto a flat perimeter, the back should be able to handle it too.

The way I do this is to lay the box on a flat surface, and shine a light inside to see where the high spots on the rim are.

Plane and check until there's only a small amount of light visible anywhere, and you have yourself a level rim.

Now as you can see, the harp arm headstock is quite a lot lower than the leveled sides. All according to plan. Just mark a pencil line along the sides at approximately the height of the harp headblock (for reference) and plane a gentle curve into it that the back should be able to flex onto:

And the final body taper, linear from 3" tail block to 2.5" neck block, curved from neck block to 1.75" harp arm headblock.

Next up: Side braces and back linings. I may do some more carving on the top braces too. It sounds much too stiff right now, although that may be necessary for it not to implode under 100+lbs of string tension.

Author:  DennisK [ Sun Apr 22, 2012 11:30 pm ]
Post subject:  Re: The Marmoset

Time for those side braces. Split, plane, chisel, sand, whatever to appropriate size, saw and sand to length. Most of them act as feet for the back braces (i.e. save me having to chisel notches, which I hate doing) so the lengths need to be fairly accurate. I'll shave down the brace ends to precise fit in the end. This is one area I'm not sure I'm happy with my methodology, as the back brace end heights make a pretty big difference to the back's resonant frequency, and I'm just guesstimating them rather than measuring in any way. I wish I could tap and shave them after closing the box. I suppose using consistent brace material would help. Maybe I should just devote the two big bracewood billets I got from Shane to back braces :) Might not be a lifetime supply, but many years at least.

Anyway, back to gluing side braces. I don't have anything other with deep enough reach other than cam clamps, but they're pretty heavy and twist the sides. So, I just stuck more cam clamps on top of them to balance the weight :P

There are also some little spring clamps holding the upper ends of the braces, but they're hidden behind the cam clamps in that picture.

Then make some linings. Take one of the top offcuts, plane the edge flat, slice a strip off, plane the new edge flat, stslice another strip off... then on each strip, use a knife to carve the rough edge to quarter-round, to be the non-glue edge, and then chisel kerfs in them.

Redwood is slightly iffy for linings since it splits easily, but it would still take a hard impact to damage them, and since I do linings in short strips between side braces, a split would never be able to travel very far. And redwood is really nice for this, because it's so soft you can slice the strips with an x-acto knife, and kerf with a chisel rather than a saw. Kerfing does take a lot of pressure, so a pad for the palm is a good idea, but it's fast.

Then glue all those in, trimming off short sections from those strips to fit each span between side braces.

I glue them slightly proud of the edge, and finger plane down to level.

Then on to making the back...
It seemed a waste to cut it out with a coping saw like I normally do, since it's so oversized that I'd have to do it in two passes due to the throat depth of the saw... which would mean 1) a lot of work, and 2) the offcuts being smaller than they otherwise could be. So I decided to try a new technique this time. Rout it out with my Dremel+router base, gradually increasing the depth until there's only a hair left to slice through by knife. Worked like a charm.

Not sure what I'm actually going to do with the offcut, but at least there's no chance that I'll think of something that it could have been used for if not cut this way or that :)
Then thinned it down, a little thinner than I meant to, about 1/16". Although the harp arm did need to be even a bit thinner than that, to be flexible enough to conform to the curve of the rim. It may end up being lower resonant frequency than the top, but then again that might not be a bad thing on a harp guitar that needs extra bass reinforcement for the low strings.

Unfortunately, it had gotten hot and humid outside at this point, and looked like it might be the end of good gluing conditions for the season. I decided to try an idea I've been thinking about... instead of building a heated cabinet to dry things out in the summer, just warm up the oven a bit, turn it off, and stick the back in there for a couple hours. Since it's so thin, I figured that would be enough time to acclimate. and it would stay warm enough that I wouldn't need to add any more heat beyond the initial warming. Then pull it out and slap the braces on ASAP. Worked quite well actually. Maybe even too well. It's slightly squiggly at the tail block area like I dried it a bit too much, although the RH in there was I think 35% when I took it out, so not way too dry at least. Also could be that just the end grain dried out too much. In any case, the squiggle isn't much and will flatten out easily when gluing to the box, and the outdoor humidity did go down again a few days later and it hasn't potato chipped, so it seems to have been a successful experiment.

Those harp arm braces were actually pretty tricky to glue. Since the plate gets stretched a bit to fit to the rim, gluing the braces on flat may make it flex unevenly when closing, not to mention getting the braces positioned perfectly would be difficult. I decided to fit the braces to the notches in the linings, and then press the plate onto them in place, being careful with how much glue I used so as not to squeeze out and attach anything to the box. I just held them by hand until mostly dry, and then set some weights on it to avoid stressing it until fully dry.

The positioning of the two cross braces below the upper transverse brace is actually somewhat unintentional. Normally I carefully position my side braces where I want the back braces, but I wasn't paying attention when I was gluing the top dentellones, and just put the side brace spaces at relatively equal spacing between the upper transverse brace and tail block. It worked out that by using 3 of those, and cutting one notch in the linings, I could make this pattern, sort of fanning out like the frets. Seemed like a fine idea, so I went with it.

The pattern for the harp arm braces is quite intentional, although I don't have the engineering chops to judge whether it really matters. My thought was, since the harp arm strings are pulling more from the outer side than from the inner side, the force will be trying to twist the harp arm. So how best to resist twisting? A helix seems pretty good... if it's going the right way. One way, twisting will collapse it in on itself. The other way, it will try to expand outward. When glued to a box, that ought to become a pretty rigid structure. So, I laid out the top and back braces to angle opposite directions, and side braces to connect them to eachother, forming a sort of connected spiral of bracing down the walls of the harp arm.

Oh, and the back center seam reinforcement... that's more top offcut material. I do it after the braces, trimming pieces to fit between them. Easier for me than cutting notches for the braces to go through, and no risk of scratching the plate in the process. Then chisel it down very thin.

And last but not least, the label. I do these in acrylic paint.

I may add another little guy in the harp arm soundhole area, even though you generally won't be able to see in there without a light. It would be really cool if I could make the eyes out of black MOP, so you can see just those in the dark if the light hits them right. But 2mm dots would be too big, and I've never tried making dots smaller than I can hold with my fingernails, so that would take some technique development time... not to mention my black MOP is from Tahiti.

Author:  DennisK [ Mon Apr 23, 2012 1:30 am ]
Post subject:  Re: The Marmoset

Next up, the bridge. I've decided to glue it on before closing the box. Unfortunately, I didn't get the neck glued to the top at precisely the right angle, so the bridge is maybe 1/10" off center. As a result, the bridge pins will cut into two of the fan braces a bit. Hopefully they'll have enough width left that I don't need to do anything drastic, just shave them away from the pins a bit. But I'm going to get that taken care of while the box is open, not to mention avoiding the troubles of gluing the bridge when I can't get my hand through the soundhole, or cam clamps either due to the shallow box. I'll have to be careful not to ding the top anywhere near the bridge since I won't be able to scrape the whole surface again, but I was planning to bridge before French polish anyway, and it shouldn't make leveling binding or anything particularly more difficult, so it seems the best option.

First of all, route the saddle slot and drill the pin holes (starting at 2mm since I have a brad point bit for that). Then cut out the shape with jeweler's saw. Two blades died in this process.

The saddle slot is slightly scruffy on the front edge, which hopefully won't have any significant effect on the sound... I may try to chisel it smoother. Dremel bearings aren't particularly stable, and the bit pulls off center when routing. I wish it had pulled off center toward the back of the slot instead of the front.

Then position it on the instrument, and drill through the holes to see where they end up. String 5 clips the brace just a touch, which means when enlarged to full size it will cut in pretty far. I decided to stop and think about it before drilling the last hole, since it's going to be about the same. The neck angle being off also means the bridge angle being off, and it seems I got the bridge plate angled a bit wrong even not accounting for that, so the holes almost went off the back edge of it. This does not make me happy, being off by so far and in so many ways all at once. I may have to resort to more strict methods to guarantee that everything lines up when I get to making a full size harp guitar.

After much soul searching, my decision is to go with it, but scoot the bridge 1-2mm toward the bass side to minimize the brace damage, and notch the holes (and possibly saddle) to push the strings back toward the treble side.

So with that decided, on to finishing up the bridge. First, drill the holes out to a good starting size for reaming. Then rasp and needle files to refine the outline, arch the surface across its width with block plane, finger plane and scraper, and then sand with 220 grit on a cork lined block to smooth out the ripples that scrapers tend to make. Then draw on the spirals in pencil.

Start the relief carving by scoring along the line with a knife.

Then chisel along the knife groove to widen it out and angle the surfaces. Repeat a few times, knife in the bottom of the groove, chisel to widen, and more chiseling to round over the spiral shapes.

Then sand everything smooth with 320 grit. I've run into an unexpected dilemma, that the fallen off grits from the sandpaper are quite colorful blue-gray against the light colored wood, and get stuck in the pores and bottom of the spiral groove.

After a round with 400 grit, and picking the grits out as best I could with a knife, I polished it up with various compounds on leather, and called it done.

Oh, and another thing I did somewhere in there was fitting to the top. First, scrape the soundboard smooth. There were some slight ripples shadowing the braces, due to the water expansion when gluing them. Also, there were some dings that needed steaming out. So I got all that done and the surface as much of a smooth and gradual curve as possible, and attempted to scrape a matching curve into the bridge. After over an hour of fiddling, it still wasn't perfect, so I decided to try the sandpaper method. I've had problems with it before, but that was because I was trying to remove a large amount of material. This is only the very final refinement, so I could gently sand with 220 grit, and it worked very well. Rub joint should be fine, although I may stick a couple of cam clamps on it for good measure.

Then get positioned at its adjusted location... so the holes drilled in the top are now slightly off center to the ones drilled in the bridge. Shellac the top up close to the bridge, as a sealer against the glue squeeze-out because this particular top gets nasty water stains. Stick bits of tape to mark the position, and it's all prepped for gluing... as soon as I work up the courage to do it.

Author:  alan stassforth [ Mon Apr 23, 2012 9:10 pm ]
Post subject:  Re: The Marmoset

Beautiful, Dennis.
Very creative work there!

Author:  DennisK [ Wed Apr 25, 2012 10:16 pm ]
Post subject:  Re: The Marmoset

Woohoo, the bridge scoot was enough, and the center fan brace survived with minimal damage:

Just lost a bit of width. The bass side fan didn't get hit at all. I decided to use the boxwood bridge pins instead of white plastic like I was considering. It's a violation of the local wood rule, but I could always swap them out until after judging if anybody cares :P

Then I tapped on it and it made some unimpressive sounds, spool clamped the back on and tapped some more and it still was more of a "pok" than a "toom". So I looked at it, thought about it, and shaved the braces some more. Took the ends of the bass X leg and bass side and center fans a bit father from the perimeter, and some height off of the lower X legs and the fans (including the center one, so the loss of width was definitely no problem).

I did do another painting for the harp arm soundhole. Pygmy marmoset to squeek at anyone who peeks in there :P

Then closed 'er up.

Tap is pretty good. Not a very long sustain, but does have that nice hollow box sound. Probably could have cut the braces even more, but I don't want to go overboard since I haven't even built a regular uke, much less the steel string harp variety.

I can't decide whether to do .080" x 3/16" bindings, possibly with .010/.010/.010 black/maple/black purfling on the top, or just .100" x 3/16" bindings and no purfling. I should have thought more about this earlier... it would have looked good with .080" binding and 1/16" cross-grain osage orange purfling bordered by .010" black, but the linings aren't quite wide enough for that. Oh well, would have been difficult to manufacture the cross grain strips anyway. Tempting to get one of those miniature table saws for that and bindings, but I'm too cheap, and a hand tool snob. Perhaps with more practice, I can cut consistent width strips with a hand saw.

Author:  Mike Lindstrom [ Wed Apr 25, 2012 10:27 pm ]
Post subject:  Re: The Marmoset

Sweet skills! I love the little hidden painting too.

Author:  DennisK [ Fri May 11, 2012 10:13 pm ]
Post subject:  Re: The Marmoset

Whew! Binding this thing was a female dog, but I did it.

But before that, I got impatient and put strings on it :twisted:

No fingerboard yet, so I couldn't really play much, but it definitely sounds good. A little weak on the lowest string or two, but especially up in the neck range it's really great. Reverby, chimey, 3-dimensional, those sorts of words.

Then back to work. Score the sides with a gramil:

Then score the plates. A fair amount of this had to be done freehand with a knife, including the heel/cutaway area on the back.

Then start the long and tricky process of chiseling it all out. First cut away the plate material to the score mark, then chip off the side material. Sometimes you can peel it in long strips, if the score line into the sides is deep enough. I got a really good one here.

I had the back come unglued from the linings in a couple spots. I was afraid that might happen, since it was pretty cold the day I glued the back on, and it took a little while to establish a pattern of removing spool clamps, squeezing in glue, and re-clamping quickly enough to keep the glue from cooling. Good thing about hide glue, just add some more and stick a few spool clamps on it and it's good as new.

Then chisel lining material to get the channel to its full width, which takes a long time to do accurately. The top binding ends at the harp headstock, the channel depth tapering down to the headstock thickness. More freehand scoring and carving, and difficulty later when it comes to bending and carving a strip to fit it.

I wussed out and used the dremel router on the notches into the neck/headblock. Especially that harp arm side, would have been near impossible to dig out with edge tools. Router makes quick work of it. Still some skill involved since there's no jig that can help you here, so it's just freehand routing to whatever looks right for the channel width.

Also did the tail inlay. I decided to do a simple squiggly line the same width as the rest of the binding, just to cover the gap where the sides meet. If I could get a seamless joint at the tail, I'd skip this. I chiseled the pocket out by hand instead of my usual method of dremel router, since I don't have a guitar body vise to hold it tail-up for the router. Easy enough to chisel while it's laying flat on the table.

Aaand, I'm maxed out on pictures for this post to show it glued in, but y'all can see that later.

Next time, bending and gluing bindings. Except I never remember to take pictures of bending, because I do it outside and don't think to take the camera, and it takes long enough without breaking my flow to photo anyway.

Author:  DennisK [ Wed May 30, 2012 10:58 pm ]
Post subject:  Re: The Marmoset

Ok, time to finish this thread. I've been mostly done since about a week ago, but still have a couple things to do before the final photoshoot.

Continuing from where I left off, here is the tail inlay glued.

Then glue the main bindings.

There were a few gaps despite my efforts at bending to a precise fit. Perhaps I should switch to rope instead of tape. But one of the nice things about hide glue is that you can lay a wet paper towel on the gap for a half hour or so to re-hydrate the glue, then heat it, and stick a clamp on to squeeze out the gap. Got rid of all the big ones this way.

Here was the most difficult piece to bend. Took me many tries, using the heating element of my charcoal starter directly, rather than the hot pipe. Tricky to get the temperature right, avoid touching the hot thing, and get the moisture and pressure right to keep the wood from peeling apart. Also tricky to get it trimmed to length and mitered to where it will fit in there just right when forced as best I can get it. Turned out I trimmed it a touch too short on the heel to harp arm corner.

Then glue it. The one clamp and a couple pieces of tape in the cutaway area are all I could really get on it. Fortunately the heel part was happy to stay in place without any clamping pressure, so I could just hold it by hand for a minute until the glue gelled, and then leave it. I also cut a little sliver of cherry to jab into that corner where I'd cut it too short, which you can see sticking out.

After trimming the filler bit and rounding over, it looks quite nice.

The end of the harp arm, however, was another story. Originally I'd planned on having a single strip of binding go all the way around the harp arm and down to the tail, but after losing a few strips, I decided to do the sides of the harp arm as separate strips, and then something else for around the end where the tight curves are.

First, I tried cutting a piece of wood to the shape of the curve, so I wouldn't have to bend it at all. But it was difficult to get it to fit, and I accidentally chiseled too much off of it when I was getting close, so I gave up on that. I probably could have bent a strip to fit around it, but I was so sick of messing with it by then, I decided to just do it in several short pieces, using some strips that broke during bending so they were curved to fit better than straight segments. Still took 4 pieces. It looks ok, but I feel like a wimp.

On the top side, the tapering down to harp headplate thickness turned out quite nice. I was expecting this to be more difficult, but it was just a matter of sticking it in place with a couple pieces of tape, looking at it, and then trimming a bit with a chisel until it fit. Here's a shot of it after I got the bindings all rounded over, shellacked, and strings on.

Author:  DennisK [ Wed May 30, 2012 10:58 pm ]
Post subject:  Re: The Marmoset

Part 2 of today's update...

One last thing to do before the fingerboard can be glued on: the leaves on the headplate tree inlay. Lots of cutting and sanding tiny bits of shell that are difficult to hold, then stick them in place with little dots of elmer's, scribe around them, and route using dremel with stewmac base and a 1/32" bit. Then glue in with hide glue, which I like for its translucent amber color. I also like the way it looks as a gap filler, where the majority of the depth is filled, but it does shrink when dry so it leaves a visible seam around the pieces.

Then level the leaves to the rounded headplate edge. Did you know you can chisel shell? Better control than sanding, and can work in concave areas like the spiral.

Then on to the fingerboard. I came up with a fun style of side markers. Dots just seemed too boring for this.

Step 1, clamp a piece of scrap along the side of the fingerboard, and drill holes, which are a little larger than the diameter of a toothpick, precisely centered on the line where the binding and scrap meet (please pretend you can't see that slot where I almost cut the fingerboard in half)

...thus creating half-holes in the binding.

Then cut little squares of .010" fiber, and short segments of toothpicks, and glue them into the half-holes.

Then chisel them flush, and you have markers that look like a vertical strip from the side, and half circle from the face, with a black outline all around :) Toothpicks are such handy things.

I've seen similar style position markers before, but always with squares rather than half-cylinders. If anyone wants to copy this style, feel free. Surely someone somewhere out there has done it before anyway.

Oh, and here's a shot of cutting the soundhole contour. Fortunately, I'd had the sense to pin the fingerboard onto the neck and mark from inside the soundhole, before I closed the box up. Then jeweler's saw to the line here, file away the saw marks, and it's a perfect fit.

Then glue the fingerboard to the neck...

As usual, it didn't want to stay 100% centered as soon as the glue was on, but it can only go so far when pinned in place. It only changed the projection at the bridge by about 1/64" at most, and toward the bass side which is the less troublesome direction to go after the scooting for the bridge pin hole and fan brace problem before. However, it did mean carving a little off the harp arm side of the neck, which was tricky to reach with a chisel and get smooth enough.

Author:  DennisK [ Wed May 30, 2012 10:59 pm ]
Post subject:  Re: The Marmoset

Deleted (accidentally posted part 4 out of order)

Author:  DennisK [ Wed May 30, 2012 11:06 pm ]
Post subject:  Re: The Marmoset

Part 3 of today's update,

On to French polishing the back and sides. I've been making sure to shellac all finalized surfaces throughout this build, so the initial wash coat is already done, and I just need to fill the pores and improve the smoothness of the surface.

I do pore filling with pumice and a scrap of cloth. Lots of alcohol and rubbing to sand up wood fibers, which conveniently replaces any final sanding step at the same time. The main surfaces haven't been sanded at all. Just scrape, shellac, pumice fill.

After the initial slurry making, I go over it with a bit less alcohol, but still enough to keep it wet, and push slowly and firmly to drag the slurry around the surface, mashing it into any pores along the way. All the alcohol used during this sometimes results in the filler shrinking into the pores some after it dries. I ended up doing a second pass of pumice slurry-making this time.

After filling, I rub quickly with a small and firm roll of cloth that has a single drop of alcohol on it, which gives it just enough friction and dissolving power to shine up the surface if there's enough shellac on it, but not enough to actually drag shellac around. The heel shined up some, but overall there's just not enough shellac yet.

I tried a new technique this time. Instead of applying more shellac with a pad, I just wiped on a couple more coats, and then repeated the rub-out procedure to stretch the shellac into a micro-thin film and compact it into the wood surface. I ended up with a gorgeous medium gloss surface where the pores are still visible, but not deep. It looks and feels more like polished ebony than a varnished surface. And the shellac is thin enough that it can't be chipped like a thicker, high gloss shellac layer. You can still end up with dull spots, but they're less bad looking because the film thickness is so small that there's no edge visible.




Author:  DennisK [ Wed May 30, 2012 11:07 pm ]
Post subject:  Re: The Marmoset

Final part of today's massive update: The Tragedy.

I was all prepped for fretting. Slots clean and lightly beveled with a couple passes of the needle file, new deadblow hammer from LMI that should make this easy, right?

Wrong. I thought using a StewMac saw and StewMac fretwire, it should be a perfect match. But apparently it is not. These frets really don't want to go in there. The rubber hammer face seems to just squish in helplessly around the immovable fret. It doesn't help that this Texas ebony fingerboard is hard as a rock, and that the binding prevents the slots from flexing open at all (although on the bright side, that prevents the neck from back bowing). However, being in a hurry to get it in playable condition for the St. Louis gathering, I tried placing a small wood block on the fret, and then hammering that, and that seems to help get them in, although it still takes a lot of hard impacts.

I started with the ones over the headblock since that's pretty much bullet proof, to get the feel of it. Then I continued up the neck, and with 3 to go, the beating was just too much for the little thing and the lamination between the neck shaft and headblock separated, with splits running along the sides from there, and the upper transverse brace split in half as well.


Depression sets in, and combined with a very busy day resulting in failure to make it to the car rental place before they closed, and failure to get to sleep early enough, I was just too tired to go to St. Louis. Over the next couple days, I managed to get those last 3 frets in by lightly tapping until they'd stay vertical in the slot, then sticking a cam clamp and caul to put a lot of pressure on it (nowhere near enough, though), and then squeezing the clamp between my palms to finally get the barbs into the slot. I still haven't done the partial frets that wrap around the soundhole, but they're not essential at least.

So, after some pondering of my options on the cracks, I decided to try the easiest one first: glue it, all in one go, just as it is. This is one of the reasons I love hide glue. If I can just get fresh glue worked into the heel lamination, and it should stick back together just fine.

I did some tests on scraps to get the viscosity of the glue right to suction into a large area with a little pushing and pulling. Then I went to the kitchen, turned on the oven, and opened it up to create a nice hot place to work where the glue wouldn't cool quickly. Heated the whole heel area nice and warm, and sucked in the glue just fine. Then mash some glue into the side cracks, and get a cam clamp on the heel and a couple little squeeze clamps for the sides before it can all dry up from the hot air, work some glue into the upper transverse brace, and just clamp that with my fingers for the next 15-20 minutes.
Resurrection successful bliss

Gave it another day to dry, put strings on, and it held together just fine. It's been almost a week now, and still no problems. It sounds wonderful. I ended up switching the tuning to CDEF GCGC (neck was originally going to be GCEA) since the harp strings pretty much make it a C instrument anyway, and it's easier to keep track of all the notes this way. Still some fret buzz to level out, but it plays surprisingly cleanly for the horror of the installation process. Action is currently at about 1/16", which is pretty comfortable already. After leveling I may even be able to push it to .040" on the high string.

I'm currently using rosewood friction pegs from LMI so I can take them in and out for further French polishing. Quite difficult to tune since steel strings are so inelastic. But it keeps the cost down for competition purposes too, so I'll wait until later to install the planetary gear pegs. Still, that makes two violations of the local wood rule, with the boxwood bridge pins... but they're all replaceable parts, at least.

I've been having a heck of a time getting a chance to record it without everyone else in the house making noise, but here's a quick one to last until I can get a video done.

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