The top is braced

This weekend I had some time to brace the top.  Here are a couple of shots:

this is a small deviation from how I normally brace the tops, namely that I added a cross grain brace to help support the dome in the top. That brace is capped with carbon fiber to give it additional strength because it's so short.  The height of the brace is such because there are additional structural braces inside the bandura that run vertically to resist the pull of the strings.  A tall brace will interfere with these braces.  I recently posted some questions to the OLF regarding some bracing ideas and that discussion can be found here.

Some specs from this top:

Weight before bracing: 278g

Weight after bracing (not final): 368g

Thickness: ~0.128"

Guitar makers will notice that this top is almost double what a guitar top weighs.  Considering the additional load that a bandura top takes it's not surprising.  Tapping produces a decent tone but nothing like what you hear when tapping a guitar top.  Unfortunately, I'm not sure that anything can be done about this because of the huge load on the bridge from all of the strings.  The good news is that this won't necessarily mean that the sound will be bad.  My prior instruments have bracing that's just as heavy or heavier than this one and sound pretty good.

A busy day in Banduristan

It's been a while since I've posted because I haven't had a chance to work on anything for quite a while.  Fortunately, this weekend I managed to get a lot done.

Rosette

Doing the rosette was basically holding up the rest of the build.  The pattern is rather complicated to do and took me almost all day Saturday.  There are a few flubs in the fine lines around the abalone but the materials are so expensive I decided to try and fix it as best I could and move on.  As it is, the mistakes are visible under close inspection but it looks fine from two or three feet away.

I used a precision adjustable router base to cut the ring-slots. 

The wood ring is a piece of koa I brought back from Hawaii back in 2000.  A tip I got from the OLF was to inlay the wooden ring first, then cut the slots for the purfling and abalone.  For the abalone, I used a new product called Zip-Flex which made life much easier.

As it was, inlaying the black-white-black was very difficult and is where the flubs are.  I tried to use a scarf joint:

to make it look seamless but it didn't work out so well.  The problem was that I only cut the angle on one end and tried to bend the other end up along the angle but it didn't follow closely enough.  Next time I'll do a true scarf joint which should work better - it worked perfectly on the abalone strips!

Braces

With the rosette done, I could move on to the braces.  Here you can see the four almost finished braces.  Because the braces are so big, I cut out the centers to form sort of an 'I' beam to lighten them up a bit.  I dropped the weight by about 25% by doing so.  You can also see the 'secret weapon' which is the small brace with the black top.  The black stuff is a strip of carbon fiber glued to the brace to help strengthen it. This short brace will be glued at 90 degrees to the grain of the wood and I'm hoping that this will hold the dome and keep the string tension from collapsing the top.  I'm a little concerned that this brace will make the top too stiff but I'm hoping that the top not collapsing will make up for the extra weight.  When checking tap tones of guitar tops vs. bandura tops, the guitar top has a much higher pitch which implies that guitar tops are much stiffer than bandura tops yet guitars have a much better bass response.

In this shot, you can see the dome shaped into the braces.  

Here you can see the layout of the braces.  The 'I' beam braces go up and down and the carbon capped brace goes diagonally.

Finally, I also managed to complete most of the body and glued up the шемсток or 'upper bridge'.

Finishing, lessons from my first guitar

(Click on any picture for a larger version)

To help expand my knowledge of instrument building, I decided to build a guitar (as I've mentioned in a previous post here).   The guitar is almost finished and I'll now go into some details on my finishing schedule.  The type of finish is up to the maker and I wanted the "so glossy it looks like it's wet" look.  Many builders feel that whoever decided that guitars should have that high gloss finish should be dug up from his grave and shot....again.  This is because that glossy look is really time consuming to achieve.  Taylor guitars have done a great job of re-popularizing the matt finish in high end guitars.  They did that because it's way less labor intense to do a matt finish vs. a gloss finish.

Finishing starts with a good preparation of the surface.  I generally sand the bare wood to 320grit.  Next because the back and sides are made of a porous wood (East Indian Rosewood) we need to do a pore fill otherwise there will be tons of little pits in the finish under each pore.  I used Z-poxy finishing resin. The  Z-poxy is a bit messy but does a really good job of filling all the little pores.  It takes almost nothing, much less than one ounce to put a coat on the guitar.  It's applied by pouring a few drops on the guitar and spreading it in with a credit card. Here's a good tutorial on how to do it.  

I used two coats of Z-poxy, sanding back to bare wood after the fist coat and trying to leave a thin coat after the second session.  The Z-poxy really "pops" the grain of the EIR.  The one rub is that when sanding the second coat on the neck, there were a couple spots where I sanded back to bare wood. They are visible as faint light spots on the heel of the neck.  Normally one would re-coat the neck but it wasn't too bad and I wanted to finish the guitar so I could get back to bandura building!  After a light coat of shellac, it was time to spray on the final finish.

The finish I'm using now is the Stew Mac branded Target Oxford USL. They're both the same thing I just ordered from Stew Mac because I had a couple other things to order from them as well.  Nitrocellulose lacquer is the "gold standard" of guitar finishes but it's also quite toxic and quite explosive (nitrocellulose is also gun cotton) and I'm just not interested in spraying it in my basement.  It can be done but you need some pretty elaborate venting systems which I don't have.  Polyester finishes are becoming quite popular with builders now too because they are very durable and because they're catalyzed, you can spray one day and buff out the next.  These finishes also have a very steep learning curve and if you screw up, you might end up having the finish harden in the spray gun which doesn't interest me either.  The waterborne finish I'm using is relatively benign, it doesn't stink up the house, and is safe to spray at home so long as you use a respirator.

For my spray gun, I just recently picked up this gun to replace my old school high pressure gun.  The HVLP systems have much lower over spray which means less dust floating around the shop.

Finally, even thought Stew-mac recommends building coats using their sanding sealer, I chose to use all USL this time around so I wouldn't have to buy two products.  Now to the finishing schedule itself.

The settings I used on the gun were the following:

1.2mm tip, 27psi at the handle

Air Screw - 1.25 turns out

Fan Screw - 1.5 turns out

Fluid Screw - 2 turns out (tried 1.75 but didn't like it.

Applied 9 coats over two days and did a quick level sand

Applied 4 more coats and measured the film thickness by peeling off some masking tape. Thickeness was .005" (13 coats so far).

Applied 5 more coats and measured, .007" on tape and .009" in the soundhole cover.

The guitar now had to hang for a month to allow the finish to fully shrink and harden.   After all this work, the finish looks like the photo to the left.  A far cry from the glossy look we're after.  To get from there to glossy is where the work really starts.  Level sanding and buffing.

Level sanding is where you use sandpaper and sanding blocks to knock down the orange peel to make a perfectly smooth surface. I started with 400g which is a bit risky: it levels fast but there is a risk of sanding too much and the 400g scratches are really large.  I had a hell of a time getting the surface scratch free and think that next time I'll start with 600g.  It's also essential to use good sandpaper.  I prefer the 3M free cut gold because they can be used dry and don't load up.  I do brush off any sanded finish and the paper after about 10 to 15 strokes.  For a sanding block I use either a small rubber eraser or a black board eraser for curved surfaces.  I went from 400g to 600g to 800g dry, then switched to an Abralon 2000g pad on my random orbit sander (my thumbs were hurting pretty bad at this point from holding the little sanding blocks).  I then took it to the buffer (you can see it in the background on the picture on top).  The results were disappointing.

Apparently I didn't spend enough time with the higher grits after the 400 because there were still a lot of scratches that could be seen at certain angles.  I had to go back to 600g, 800g then the 2000g.  I had to go back and re-do areas of the guitar several times because of this problem. I also used some 1000g wet paper in some areas to get rid of 800g scratches. I think this could be avoided with the following schedule:

Start with 600g, it might take longer to level but there will almost certainly be no deep scratches.

800g dry

1000g abralon pad wet (I didn't have one this time but I found some on line)

2000g abralon pad

Buffer.

By the way I also have a 4000g abralon pad but found that you can go from 2000g to the buffer and not have any scratches.  (on the other hand, a buddy, Mark Swanson, says that on nitro he can go from either 400g or 600g, don't remember, straight to the buffer with no scratches!!! what the hell am I doing wrong?).

Once all the sanding was done, it was off to the buffer for about a two hours on the medium wheel followed by about a half our on the fine wheel.  I suspect had I done a better job level sanding I could have spent less time on the buffer.  

At the end of the day (about 7 hours total level sanding and buffing), I ended up with the finish in the shot to the left.  It came out pretty nice I think.  I suspect that as I get better at this I'll be able to get it done in less than half that time.

After finishing the neck the same way I attached the neck to the body.  All I have left is to glue on the Bridge, make the nut and saddle and final setup.   

Phew! What a long post.  Hopefully someone will find it useful.

Neck to Rim gluing, Scroll Carving, doming

I haven't written much lately because I haven't done too much in the shop lately.  I'll be in Chicago most of this week so I decided to post some stuff at least.

Scroll Carving -  A few weeks ago I carved the scroll for the top of the neck.  To fanc

y things up a bit this time I also carved a scroll on the back as well.  The maple isn't too hard to carve except that it splits at the drop of a hat.  I bought a few sharpening accessories for my sharpening gizmo which allowed me to really sharpen up my gouges and that helped a lot. 

After doing a few more things to the neck, rough shaping, chambering to lower weight, I was almost ready to glue the neck to the rim.  First, the rim had to be profiled to the dome shape (see last post).  I used my shop made motorized sanding dish to do the work and it went very quickly.  Surprisingly, the motor is only 1/6hp but it's just strong enough.  I think for this tool it's better to not have too much power so you don't wreck anything too quickly.

What I forgot to do was to glue the pinblock on and profile it before I glued the rim to the neck.  Oh well, that shouldn't be too bad because I should be able to get it really close by hand and then do a final quick sanding of the rim and pinblock already attached to the neck.  Below are a few more picks of what I've done in the last few weeks.  Remember that the final shapes on the neck will be done once it's glued to the rim and further along.  You can also see the jointed (but not sanded) top in the background of one of the shots.   I also included a picture of my first guitar which is just about ready to be level sanded, buffed out, and set up to go.  

I'm off to the airport, hopefully I'll have some time to get some stuff done next weekend.

Domed Tops

For a long time now, guitar makers have been doming the tops of their instruments using various methods.  The top is domed for several reasons:

A domed top, like an arch, is stronger than a purely flat top with the same dimensions.

Wood expands and contracts due to relative humidity.  If a top is domed and glued at about the lowest level of relative humidity the instrument will see (usually, we don't like to see instruments get any drier than at 40%RH) a domed top can move much more easily than a flat top. That is, as humidity increases and the top increases in width across the grain, the radius of the dome will simply decrease rather than breaking the sides.  If the RH goes down, the top will sink rather than crack. For these reasons, I started to dome my tops with my second bandura but basically, I failed.  

I tried to dome my top by making a dished work board with an arbitrary dish to it.  I basically assumed that the rim of the bandura (the frame) would be level and gouged out a little dome into the workboard, less than an 1/8" at the deepest point.  I then profiled the braces so that they matched the dish of my workboard.

By the time I got everything glued up the little bit of dome I had worked into the design was almost gone because of forcing a dome onto a flat rim and the rest was gone once the instrument was strung up.  The other problem I had was that because the dome was arbitrary, it was very difficult to get the bridge to match up exactly to the top so I used epoxy when gluing to fill the gaps.  Here's the plan for the next instrument.

Hanging out on a lot of guitar maker's forums over the last several years, I learned that many "flat top" guitar makers used a spherically dished workboard to build the dome into their tops.  They use that same workboard to "profile the sides" or shape the sides of the guitar so that they match the 3D aspect of a sphere.  My first two tries at doming had flat rims (i.e. they didn't match the 3D profile of the dome) for this next one, I've purchased a dished work board with a 25' radius.

You can see how guitar makers profile the sides here I used a very similar method when I built my first guitar to learn how to do it except I used a motorized table to make the sanding go faster.  The rims are much thicker on a bandura so I wanted it to be motorized to make the job easier.   I profiled the sides a few days ago and it worked fine.

Next steps:  The next steps coming up will be to glue the neck to the rim, the rim to the back and begin bracing the top.  In my next post, I'll have some pictures of all of the components and how they go together. 

Latest Activities

For a while, I was maintaining a website with my bandura activities but for me, the standard html thing was just a little too cumbersome to deal with.  Eventually I'll put some updates there and add some historical info here but for now, to see information about my first two banduras, check the old website here.

Since my last update on that site, I've re-topped bandura number one because the soundboard was too weak and collapsed, completed bandura #3 and almost finished a 000 sized acoustic guitar from a stew-mac kit. I'll cover the details of those in other posts as time permits.  The guitar has been completed and finished (i.e. I've sprayed the lacquer) and the finish now needs to cure for about three weeks before everything is level sanded and buffed to a high gloss shine.  Then the neck is attached to the guitar for finial setup.  While it's curing, I've started work on bandura #4.

After I completed bandura # 1, I decided that I was going to make three banduras in parallel but about 1/4 of the way into the build I changed my mind.  Although it seemed like a good idea at the time, the problem is that you can't use the experience from one instrument to make design changes to the next.  I had made three sets of the main frame parts for the three instruments and as I was going along, I had an idea for a much better way to join the "rim" to the "poly frame" but I had already made the cut on all three parts. At that point I decided that until I get a decent design down, I would work serially instead of in parallel.

Bandura # 4

Bandura #4 starts it's life as the second rim, poly frame and

 neck from that batch of three that I started many years ago.  I changed the design to eliminate that "bad cut" from the original design. This instrument will have one major innovation I'll get to in a minute. The main design elements of this one are:

• Sitka Spruce Top
• Sitka Bracing
• Curly maple Back
• soft maple poly frame and neck.

The big innovation for me will be that this one wil

l have a spherically domed top using the same tools used by flat top acoustic guitar makers.  I'll go into this more in another post.  As far as I can tell, the Лвівянки (Lviv banduras) have been using this method for a while but this could be the first time that it's been done on a North American Bandura.  I've actually tried to put a dome on my last two banduras and the re-top of bandura #1 but my attempts basically failed.  

I've about had it for writing for tonight and to continue about the doming will take an entire post so to conclude this post, here's a picture I took last night after profiling the sides as a little teaser:

Kickoff

After years of not updating my Bandura Making homepage because I'm just too lazy to learn any of the basic web authoring tools, I've decided to start this Bandura Making blog to document my bandura making progress.  I'll also be using it to voice my thoughts on the state of the bandura community in North America and to a lesser degree, in Ukraine.  Hopefully you'll all find this stuff interesting.