Lattice Braced Concert Uke

[Allen]

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As build alongs seem to be fairly entertaining for everyone, and this is one that is certainly not your run of the mill uke, I'd thought that I'd take some pictures, add some commentary and take you along for the ride.It's been something that I've been kicking around in my head for a year now, and didn't really know how to get started on it. But the pieces have fallen into place over the last few months. I also thought that if this turns out to be as good as I'm hoping, then this will be the uke that I will put up for the Festival.

The idea for this first stemmed from building my first uke for the Playmakers 2009 in Albany last year. I was very fortunate to sit in on a session with Greg Smallman where he discussed his lattice braced guitars, and I was fairly blown away with the volume, and quality of the sound.

Then there was David Hurds session and further instruction at the TAFE for those who could stay for a couple more days.

And finally a very long motorcycle ride home from Bob Connors, down in Geelong, back up to Cairns, where I had days on end to mull these things over in my head with out too many distractions.

Bit by bit over the last year I've got closer to figuring out how I was going to tackle this project. The first design hurdle came about by a bit of misfortune after my uke class recently, I broke the last spiral downcut bit that I had and didn't want to wait for another to show up, so tried a bit of a radical bracing pattern on a Banksia concert uke, taking inspiration from Matt Blacka's gorgeous Kasha style uke.

The bracing pattern seemed to work really well, and that uke has really found a voice, that surprises me every time I pick it up. It also has a look that I quite enjoy, and it sparks interest in people who want to hear it, and peak inside the sound port.

Then the second part of the puzzle for me was solved I hope when I followed a link that Martin put up to a Classical guitar builder that uses lattice tops, but in a somewhat different manner than I had ever seen previously. I thought that this would be just what I was looking for, as a ukes top needs to be so thin with standard type of finger bracing, that to make the entire top even thinner in order to use a lattice bracing pattern would be unrealistic and destined to failure.

So, I started out with some Sitka Spruce with some nice and subtle bear claw and ran it through the drum sander down to .080. The top at this point is still very stiff across the grain and weights in at 46.0 grams.

I then set my laminate trimmer to route around the perimeter of the area that I'm going to apply the lattice. I took this area down to .035. and it dropped the weight of the top to 38.5 grams.

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I then blended the centre section into the perimeter, being very careful not to take that area down any more, and ended up with a top that now weights in at 35.0 grams.

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It is also fairly flexible across the grain but only on the perimeter, My thought is that I want the entire lower bout and part of the upper to act like a piston. At least this in theory.

Next I made up some lattice on 30 mm centres out of 2.8 mm x 6 mm tall Red Spruce. These were just some off cuts that I had in the scrap box that I felt would be useful for something, and turns out they are.

I made them 2.8 wide because that was the width of my thickest table saw blade, and I could cut all the lap joints and have a nice snug fit quite easily. I then put a dab of hide glue into each joint and pressed them together on a granite slab, so that they were nice and flat.

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I dressed the bottom of the lattice on a flat board with 100 grit paper on it after it was dry, then pressed the lattice onto the top with a bit of a radius built into the work board in the lower bout. All glued in with hide glue as well.

The lattice weights in at 13.3 grams prior to voicing the top. I also glued on the UTB today, and the entire top now weights in at 52.3 grams.

More photos to come tomorrow.

[Joe Sustaire]

Wow Allen, you've really ventured into some interesting territory here! Must have been a great bike ride for all that percolation!

That backlit shot of the thinned top is great, can't wait to hear how this works out.

Thanks,
Joe

[Localele]

My first thought Allen is that the lattice pieces could be half that thickness.All that timber will certainly stiffen up the top again.From memory Smallman's lattice was made of 3mm thick timber for a full size guitar.Keep up the good work.

[Nick]

Thanks for deciding to post this build Allen. I know it's not a real guitar (*Ducks to avoid the barage of rotten tomatoes*) but it will certainly be an interesting follow along. Always a bit scary posting an experiment because you're never to sure if things will work out but with your talent I'm sure it's going to be a cracker.

[Allen]

You're spot on with the hight being too much Micheal. I half expected it to be, but it was a lot easier to handle pieces that size rather than toothpicks, and easy to take the hight down, rather than try and stiffen it up after.

Anyway overnight everything firmed up enough to work on it this morning. It was so stiff I reckon I could have stood on the top and not damaged it.

So I took the Festool sander with some 80 grit to the top of the lattice and took it all down to 3 mm tall. This is where I just started to see the lap joints appearing. Then I started to taper the entire lattice down around the perimeter. Flexing and tapping as I went.

I finally ended up with the sides of the lower bout down fairly thin, as well as up by the UTB, whilst keeping the end of the lower bout just a bit taller. I didn't want to have the top too loose along it's length.

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The lattice in the centre of the bridge area ended up at 2.4 mm tall, The top is moderately stiff across the grain with it being far less stiff on the edges of the lower bout. My very best sounding uke with a cedar top is far less stiff than this once across the entire top, but similar to the way this one is at the perimeter.

Now to the numbers.

Original top was 46 grams without the thinning in the centre or any braces. This top now weights in at 43 grams total with all the bracing. So it is 6.5% less in weight.

Got to make a neck now and bend some sides.

[Dominic]

Allen, thanks for the post.

I am curious. With the blending of the routed channel, what shape do you end up pressing your braces into. Once in the dish, I am assuming you have a radius on the inside with a flat/er section in the middle. Does this sound correct.

Whats the thinking behind it? I get that you end up with a thin perimeter but does it complicate the final shape of the top. Does the outside of the top retain its shape after gluing etc?

Cheers
Dom

[Allen]

I have a solera of sorts that I build the ukes on Dom. They use a Spanish Heel, and I've dished out the work board in the lower bout up to the area that the lower transverse brace would go just below the soundhole on a conventional top. I don't know what the radius would be, I just scooped it out with a small violin makers plane and sander.

I've kept the area on the solera were the sides and linings will sit flat. That is the dishing out doesn't go all the way to the perimeterl, so as to make attaching the top much easier.

I wanted to keep the area of the top under the bridge thicker in the idea of it being somewhat like a bridge patch, but having a nice smooth graduation in the stiffness. I've seen some tops that were very thin all over, and showed mapping of bridge patch and bracing. Something I hope to avoid.

From the show side of the top, there is a small amount of doming in the area of the bridge, On the underside the top itself and the bracing are thicker than at the perimeter. It even has a nice ring to it when tapped, which is something hard to get in these small tops.

[Dominic]

Thanks Allen, I also looked a the classical link you put in the post. Seems that with this method you end up with an edge a bit like an archtop with a thinned kind of re-curve around the edge.

Interesting build, are you thinking of giving it a go on something larger?

Dom

[Allen]

In a way I guess there may end up being a bit of a recurve to the top building like this. It may be so subtle as to be hard to spot by eye, but being such a small instrument, little things can make a huge difference.

I've got a Soprano all lined up for the next one Dom. Then I suppose if things progress in the right direction I'll try it on a Tenor. I don't have plans after that. Depends on what the coming year brings in the way of commissions, or things that grab my attention.

[John Steele]

Cool thread Allen. It will be fun following along. Those soundholes look great BTW. Same as the last one it looks like. Has a better look to me than a single port up there. I'm curious what your top thickness was after you routed?
I listened to the Smallman interview a while back, so I kinda understand.
Thx for posting
J

[Allen]

Top thickness around the perimeter ended up at .035 inch or a touch less. The rest of the top is .080 inch. The area in the middle of the lower bout was blended out, and at the highest point under the bridge for a 12 fret to the body is .070 inch.

[John Steele]

Allen wrote:
Top thickness around the perimeter ended up at .035 inch or a touch less. The rest of the top is .080 inch. .

Wow, that is thin .

[Localele]

Quote:
made up some lattice on 30 mm centres out of 2.8 mm x 6 mm tall Red Spruce

My thought was for the thickness Allen. I know you cut them for the kerf of your tablesaw but I was thinking that a smaller dimension like 1.4mm thick for the grid parts but keep the height to maintain stiffness.Maybe cut the joints with the bandsaw.I have a theory about it being easier to sneak up on a tap tone if you start with taller but thinner braces and then tune from there.

[Allen]

Yes it is thin, at about 0.88 mm.

Greg Smallman said that his tops on his Concert Line are 1 mm think and that is on his full size classical s, so I figured that going a bit thinner on a uke should be doable. The tension on uke strings for a concert sized instrument are going to be quite a bit less than a full size classical guitar.

Some of the ukes with spurce tops I've been looking at are certainly down in the 1.2 to 1.5 range without lattice bracing.

I get were you coming from with that Micheal, but I have a concern about enough glueing footprint if I went that thin on the lattice. I'd need to change the way I did it to one where I spread out something like epoxy onto a flat surface, then laid the lattice on it to "wet it's feet". Then I suppose the best bet would be to vacuum press them in. All things to consider as "Improvements" should this turn out to be a viable idea.

Anyway, the Qld maple I'm going to use for a couple of necks has been laminated and waiting for glue to dry. Tomorrow will see a bit more progress on that front hopefully. Also making some headway on a Weissenborn where linings will go in tomorrow as well. Then there is a bridge to make for a Tiger Myrtle uke that has had it's last coat of clear applied today.

Karen has the day off, and has a burning desire to buy a new lounge suite, so I might have part of my day hijacked.

[liam_fnq]

well done allen. i've been tossing around the idea of attempting a lattice braced uke in the coming months so this thread will be mandatory reading for me.

my question is regarding the use of an offset soundhole combined with lattice bracing. did you go this way for a particular reason? is it just to increase the area of the vibrating footprint? or is it for structural reasons?

[Allen]

It was mostly to do with getting as much soundboard real estate as I could Liam. And I really like the look of the top on the Banksia one, so thought I might as well expand on what I learnt from that one. And on top of that, I really don't like doing rosettes that small. Very fiddly work. Much easier drilling a bunch of different sized holes.

This one is going to have Brazilian Mahogany back and sides. Off cuts from the Weissenborn set I got from Micheal. Good value in that where I not only got the Weis set, but a concert and soprano uke set as well. Both with 1 piece backs.

[Hesh1956]

Allen bro you could probably open up the sound even more by getting rid of some mass and carving every piece of the lattice bracing into a triangular cross section.....

Just kidding...

Outstanding work M8, very innovative and it's great to see the CF use here too.

[Lillian]

Allen wrote:
I'd need to change the way I did it to one where I spread out something like epoxy onto a flat surface, then laid the lattice on it to "wet it's feet".

I like this whole design package Allen. The multi soundhole looks contemporary so people will naturally expect to 'hear' a difference or an improvement in projection over a traditional uke. Although 'functional', the visual 'suggestion' that this aspect offers will probably help deliver upon that expectation somewhat, but psychology aside, i feel the thin lattice braced top will certainly deliver truly measurable improvements.

I also agree with Michael and feel that the lattice could benefit from being taller but narrower in keeping with the idea of reducing over all mass in the real estate of the top that counts. As you say, all things to consider as you progress. In regards to your above quote, I was thinking you may be able to stay with hide glue if you experiment with a plate warmer, the kind used for keeping ones dinner warm on a cold night. If these warmers are indeed hot enough, you could cover the platter with foil and then HHG wetting the footprint in hot hide glue in this way.

Just thought i would mention this as it is something i have toyed with myself when investigating Nomex sandwich double tops and lattice bracing since my issue with epoxy came to be.

Cheers

Kim

[Allen]

I do have one of those sort of warmers. Actually I think it is for making crapes, but would do something similar. I'll look at doing this on the Soprano Uke.

I was also wondering how long it would take to comment on the black capping on the UTB. It's actually Ebony, not CF as I don't have any that thin, but felt for ascetics and perhaps a little extra strength it should go on there.

[Lillian]

An electric heating pad would work as well, especially if you put a sheet of glass over it to compress it and rest the wood on the glass.

[schrammguitars]

You can make it even lighter if you use light density balsa (6-14lbs/cu.ft) Red Spruce is probably around 23-27lbs/cu.ft. Epoxy a layer of cf tow between the lattice and the top then shape the lattice. After that add another layer of 6k tow on top. You remove about 40%+ of the lattice prior to adding the top layer of cf tow.

img~

In this photo I'm vacuum clamping the top layer of cf tow to the lattice.
The top mold is scooped out more in front of the bridge so that when the strings are on it will flatten out.

[Kim]

Thanks for that David. What is the bagging material you are using??

Cheers

Kim

[schrammguitars]

I get all my vacuum clamp and pump materials from http://www.veneersupplies.com

I made my own pump from one of his kits. They are the pest I have seen. The motor goes on for about 20 seconds and shuts off. About 30 minutes to an hour later it turns on again for about 5 seconds.
This is the pump I use and HIGHLY recommend. I've used mine for several years now.
http://www.veneersupplies.com/product_i ... ts_id=2795


I use this bag http://www.veneersupplies.com/product_i ... ts_id=2710

The reason I use the big bag is so I can vacuum clamp several projects at the same time. I fold it in half when I'm only gluing up one small project. Best bags in the world!!! I've made 50+ guitars with the above equipment. One of the best tool investment I have ever made.

Tell Joe I sent you. Smile

[Kim]

Thanks David,

I have dealt with Joe from Veneer Supplies.com in the past and he certainly seems to be the most tuned in for the needs of the DIY guy.

The polyurethane bags look good but Xie, i guess with his 24hr sale, right now is the time to jump in.

Cheers

Kim

[Lillian]

David, what pump did you use for the heart of your system? One from Joe Woodworker?