Soundboard, Kerf Lining, & F-Holes

Friday, March 27, 2009.

Gonna be away for a few days, so this is my post for the week. I spent the vast majority of the week on carving out the interior of the back board, again with my wood carving tools followed up by using a scraper, the same way I did earlier on the sound board.

On Monday, I also glued my sides onto the tail block. Here are some photos.



I’m not particularly thrilled with the seam I ended up with once the glue set because of a small gap at the top of the joint between the two side pieces, but since some of it will go away due when I install the side bindings and the tail piece should cover most, if not all, of the rest of it, I’m not going to stress over it. In any case, I my plan is to try to fill the gap with a glue/sawdust combo before I attach the soundboard. Here is what the gap looks like (the quarter is for reference).

With the tail block glue setting, I got started with carving the back board.

As with the soundboard, I used Mr. Siminoff’s templates to gauge my depths as I cut.

For this first picture, I have placed each of the templates in their specific location on the back. Using my gouge, I then grooved out the wood to the approximate depth of each template and then cut out the material in between.

Progress at the end of Monday. It’s kind of hard to tell from this photo, but at this point I had cut two grooves and roughed the shape from the tail to the first groove.

Progress at the end of Tuesday.


And by the end of Wednesday, I had pretty much completed the major roughing.

Thursday evening was spent with the scraper getting the many of the humps and swales out with more yet to do. I didn’t post any more photos of it because I can’t see enough difference between those and the close-up shot above to see the value.

This morning (I have the day off today) I chose to take a break from scraping and go ahead and glue in the kerf lining for the soundboard. Using my hide glue once again, and the 40 clothes pins I purchased previously at the hobby store, here is how that looks.



From what I can see from the fact that the glue oozed out as I applied them, I am quite pleased with the strength of the clothes pins with out any additional rubber bands (a technique I read about that others have used to get a tighter grip). We’ll see once the glue sets if I am still pleased then.

Pretty soon, I will be to the point where I will be gluing the soundboard to the sides, but before I can do that, I will need to get the top edge of the sides leveled all the way around. To do this, I have made myself a sanding board from a scrap board (saved from when I made my truing board) with sandpaper glued to one side.

Now that I am ready to sand, all I have to do before I can start is to wait for the glue on the kerf to dry. According to Mr. Siminoff, I should wait at least 24 hours for that which means sanding will have to wait until I get back. So in the mean time, I got a couple of other items done today.

When we last saw the neck, I had glued the two pieces onto the sides of the peg head and then sanded it down. There is, however, a whole lot of work left to do on it before it is ready to be fitted to the body and I thought I would get started with some of it.

The next bit that needed to be done was to install a scroll reinforcement. This takes the form of a 1” diameter maple disk that is installed on the larger of the two peg head scrolls to help prevent it from cracking or breaking off. This is done by drilling out a 3/16” deep pocket with a forstner bit (a drill bit that cuts a flat-bottomed hole) and then gluing in a maple disk whose grain is oriented perpendicular to that of the peg head. This gives opposing wood grains in the area where the peg head scroll is the weakest and, because it is ultimately covered by the peg head veneer, it is hidden.

Like the kerf lining, this also needs to be clamped and allowed to dry for at least 24 hours. I left the disk a little long so that I could sand it down to the exact height of the peg head once the glue is dry.

The other thing I got accomplished was to mark the locations of my F-holes on the front of the soundboard,

and to then glue gauze onto the inside for support.

Since the F-holes are located in the thinnest part of the soundboard, the gauze helps prevent splitting especially while cutting the holes on the scroll saw. Like everything else I have done today, this needs to dry for at least 24 hours before I can cut.

Until next week. Tune in again - same Bat Time, same Bat Channel.

Back and Sides

Sunday, March 22, 2009.

This week was less productive than others, but as I get further and further into this, I guess that is to be expected occasionally. What I did get done was to bend all of my side wood, glue most of it together, and to get the maple for the back ready for shaping. Now that I look at it, maybe the week was more productive than I thought.

On Monday, I decided to dress the sides of my maple back wood and glue them together. I clamped each of the two halves into my truing board and squared them with my hand planer. Before I could glue, though, I had to be sure that the two edges were true and square. I did this by holding the two boards together up to the light and looking for a gap between them. The first time I did it, there was enough of a gap that I took one of the boards back to the truing board for rework. The second time, while there was still a really tiny gap, I decided to do a trial clamp-up, and the gap disappeared. Time to glue.

Here is the back glued and clamped together. Once again, I used hide glue for this and did my best to make the bottom side (opposite the clamps) as flat as possible for the sake for when I plane it later.

Tuesday, I began the process of attempting to bend my side wood. I had a lot of trouble with every bend I tried and would end up breaking the wood. After destroying one full 2-ft length, I gave up for the night and did a little research to try to find out what I was doing wrong. I went back “the source” (www.mandolincafe.com) and found an old post where several professional luthiers shared their techniques. What I found was that there were two things they do differently than I was doing. First, most of them work their unbent wood down to a thickness of 0.70” to 0.8” before bending. This, they explain, makes the bending process, especially when using the hot-pipe bending method as I am, much easier but still allows the finished sides to be strong. Second, most of them use a backing material held against the wood while bending. This backing material is typically a thin strip of metal.

So on Wednesday night, I was ready to try it again, only this time I decided to use my drum-sanding rig to thin my strips down first. This process, it turned out, took quite a while, so after I was done sanding down three strips of wood my night was pretty much used up and I was only able to bend one piece of wood, relatively successfully, before shutting down for the night.

Thursday, I was back at it again, bending and breaking my wood (dang it). The piece I was trying to bend this time was a small section that connects the head block to the first point. This piece, I had read, is thought to be one of the more difficult ones to bend and now I understand why. It is quite a short piece with opposing sharp curves at each end and, as I discovered way back as when I was attempting my first practice bends, bending the wood right at the edges is much more difficult than just about anywhere else along the strip. Consequently, I broke several of these pieces before finally getting one close. At the end of the evening, while attempting to finish bending the second to last piece I needed, I was getting pretty frustrated with my inability to get the sharper bends without cracking the edges. That was when it dawned on me that I needed to try using the backing material the professionals had recommended.

Now before you begin to question my intelligence too much, I had tried this before, but with no success. But that effort and experience was on wood that was too thick, too wide, and too early in my learning curve. Once I realized this was poor experience to base decisions on, it was time to try again.

As soon as I broke out the backing strip it was the difference between night and day. All of a sudden, no more edge cracking and quicker, sharper bends were mine for the asking. It was unreal. The piece I had been laboring over was quickly finished and, where I just knew it was going to crack, smooth. This is one lesson I will not quickly forget.

The last thing I did before closing down for the night was to glue the head block onto the scroll wood.


In these photos, it appears that I might also be gluing the upper point on, too. This is not the case. This is where I had clamped one of the side pieces onto the mold to allow it to dry to shape after bending.

Friday was movie and dinner night with my lovely wife, so no mandolin building.

Saturday I bought a surface planer. My back wood was about 1-1/8” thick at its thickest spot and about 7/8” at the thinnest. My goal, as per Mr. Siminoff’s book, is 5/8” (and flat). Not only did my wood vary in thickness, it was also quite cupped and warped. Fortunately my gluing efforts allowed it to be relatively flat on one side so putting it through the planer was no problem.


Its really hard see much from these pictures, but these are both sides before planing.

And here I am getting ready to make my first pass. I did nothing extra to attempt to hold the part flat or square.

I am really happy with the results of my planing. The board came out really nice.



Here it is as it came out of the planer and then as I marked it with my template. (It's really hard to see, but there is a penciled outline there!)

Finally, I made new mahogany point blocks and was able to glue most of the rest of my side pieces together. I chose to make new blocks when I found that the shapes that Mr. Siminoff supplies did not match well with what I needed to match the side wood and the mold. While I am comfortable that this is purely a result of inaccuracy on my part when I made my mold, making blocks that match it are now necessary. To do this, I traced the curves of my mold onto paper, offset the lines by the thickness of the side wood and then used those to make new templates.


In this picture (above), I clamped the wild end of the scroll piece back to mold simply for the photo. I intend to make a couple of minor bending adjustments to this piece before gluing it to the tail block.