ADDING LINING TO THE SIDES

I'm slowly beginning to realize that guitar building is a peculiar thing!

I was very nervous about bending the sides by hand on a hot pipe, but to my surprise it went quite smoothly. When it came to adding kerfed linings to the sides, I thought it was going to be a piece of cake. After all it's just gluing a little strip of wood onto another. How hard can that be? Wrong!!! It soon became apparent that they were next to impossible to manipulate without snapping them left, right and center even though I try to handle them very careful. Where did this come from?

Being at a loss of what to do I read through my books on guitar building, "Build Your Own Acoustic Guitar" by Jonathan Kinkade being one of them. In the section about kerfed linings he mentions that "the kerfing strips are easier to manage when they are cut into 6" strips". This little sentence suddenly got a whole new meaning. I also consulted several fellow builders just to find that they too had been caught off guard the first time they had a go.

Something had to be done and off I went:

BENDING:
Through a lot of research it became clear that the best way to avoid breaking the linings were to pre-bend them in some way. Some people suggested wetting them and clamping them on the outside of the sides and leaving them over night. Others suggested steaming them with wetted paper towel and a hot household iron. I experimented with a little jig to hold the linings in while heating them with a heat gun. In then end I resorted to bending them like the side, on my bending iron.

At this point the linings were already in a somewhat bad shape: One had broken in two places, one had a fracture while the last two were still intact.

I started by bending the 'three piece' lining since it was the most damaged. What the heck, why not break it a little more if it would come to that. It went quite well though, and stayed in three pieces after all. Second came the fractured lining. This proved to be a little more troublesome than the first one, as it was still in one long piece and therefor had to be handled with much more care. Despite this, I managed to turn that into a 'three piece' affair too. Now, two of the linings were broken in three pieces; At least there was some sort of consistency (I'm keeping a positive mind).

Learning from my mistakes I managed to bend the last two linings without breaking either of them, though I did have a few close calls.

I aimed at bending them into a C-shape with each bout slightly overbent to avoid having the yet-to-be-clamped part of the linings smearing glue on the sides. I did not worry too much about bending the waist area for the same reason.

INSTALLATION:
I decided to use the damaged linings against the soundboard, where the fractures would not be immediately visible, whereas the two intact ones would be used for the back where they could been seen through the soundhole.

I clamped the side into the lining jig and started with a dry run with the three-piece linings to see if some unforeseen issued would pop up, but to my surprise it went pretty smoothly. It seemed as if all my struggles disappeared once the linings had been pre-bent. I started clamping the linings on at the waist and moved my way outwards along the upper and lower bouts respectively.

I took the lining off again and applied a modest film of glue to it by dapping it on with a finger and glued it on the side with 3/4" plastic spring clamps, about 1mm proud of the edge. I butted the broken segments up against each other the best I could to disguise the fractures. Some ended up being barely noticeable while others sported a little gap. Oh well!

In retrospect I think the clamps, though they are very nice and have a good squeeze, were a little too wide for the job. As a result there are a couple of spots where the linings are not sitting tight against the sides. I tried to shave a couple of the swiveling clamp tips down but to little effect as the area where the jaws connect has a big 'knuckle' that prevents the clamps on closer together. Alternatively I could have made two long bent cauls to go on either side of the glue-up to even out the clamping pressure.

I did experiment by applying the glue on the first strip with a newly acquired roller - the kind you use for lino printing - but even though it did leave a thinner, more even translucent film of glue on the work that produced virtually no squeeze out, it wasn't a particularly well suited tool for the fragile linings. However, I think I'll be trying it out again later on other processes. It might have worked very well if the linings had not been pre-bent and could have been laid down flat of a bench for support.

As this build is progressing I'm slowly becoming aware of how little glue is actually needed when you want two pieces of wood to stick together. When I started out, I was pouring it on with a thick coat that left me a huge mess of squeezed out glue to clean up afterwards.

After about twenty minutes I cleaned up the excess glue with a sharp chisel. In Bogdanovich' book he recommends waiting only 8 minutes before doing this, but I find it to wet to work with. Maybe he works in a dryer and warmer environment, but for me fifteen to twenty minutes seems to work better.

The back linings were installed in a similar fashion, including a dry run before the real deal. I worried it would be difficult to have the linings follow the undulating edge of the side made to accommodate the domed back plate. This did not prove to be a big problem, as it was relatively easy to manipulate the linings to follow the edge as they went around the bouts. The back linings were also installed 1mm proud.

LAST THOUGHT:
I have come to believe that installing regular kerfing and reverse kerfing must be two quite different beasts. When installing reverse kerfing you have to bend the strips 'the other' way, making the bouts the tricky parts as the kerfing is opened up, making the thinner segments, the ones that have slightly deeper cuts, prone to breaking as they will take more of the bend than the thicker, less deep and stiffer cuts, while the waist, where the thinner sections only can bend so much before the 'kerf blocks' are butting against one another thus limiting how much each segment can bend, is a piece of cake. With normal kerfing I imagine the problem is quite the opposite and that the waist is where the breakage is likely to occur. And if it does, it is no big deal as the fracture will have little effect on the stiffness and cosmetically it is virtually hidden.

I also believe there is a great distinction in the properties of regular and reverse kerfing (and solid linings for that matter). Apart from looks, reverse kerfing will inherently create stiffer and stronger construction than regular kerfing due to the fact that the uncut, solid part is on the 'outside' and not glued to the side itself. Whether this is something desirable, something that will make the guitar hold up longer and make it sound better is another matter. But, if stiffness is what you are after, then it is not desirable to have the reverse kerfed lining broken or cut into sections. Whereas it is likely it would ease the process of installing them, it would also defeats the purpose of having them reversed in the first place.

BENDING LININGS

BROKEN LININGS SEGMENTS

DRY FITTING TOP LININGS

APPLYING GLUE

GLUE CLEAN-UP

SOUNDBOARD LININGS GLUED AND CLAMPED

THE SIDES WITH BACK LININGS INSTALLED

INTERIOR VIEW OF THE LOWER BOUT

FINISHED SIDES WITH LININGS

FINISHED SIDES WITH LININGS

FINISHED SIDES DETAIL

TRIMMING SIDES FOR BACK DOMING

My doubts about whether or not to add the sides to the neck first continues. However, yesterday I took yet another step towards doing just that by trimming the sides for the domed back, ready for the kerfed linings to be glued on.

Earlier I had fabricated some small shims that was to function as spacers to raise the sides equal to the thickness of the soundboard, about 2.2mm around the neck area, and attached them to the solera with double sided stickytape. Well, actually they were a little more than that including the stickytape, but when I squeezed my calipers a little they went down to 2.20mm. Then I put the sides back in the solera and marked the sides at the neck to 78.5mm, measuring from the bottom of the solera, roughly 2mm less than the final height, allowing for the thickness of the back. The same was done at the tail, though here to 84mm, roughly 1.5mm less than the final height. The reason for this was that the soundboard is about 0.5mm thinner around the lower bout than at the neck and the shims were at consistent thickness.

Next, the 15' radius disc was laid upon the whole assemble. In order to have the disc resting at an equal height above the marks at the neck and tail, two shims were added, one to each side around the bottom of the lower bout. I made a little 'marking device' from some scrap walnut by drilling a hole 21mm down from the top, matching the distance from the bottom of the radius disc to the marks on the sides.

I butted the little marker device up against the radiused disc, stuck a white pencil through the hole and traced a line all around the sides creating an undulating line following the radiused dome of the disc. Unfortunately the support blocks on the solera were so high that they got in the way, interrupting the line whenever I bumped into one. However, once the initial marking was done I took the sides out of the solera and finished the segmented line by using a piece of card as a ruler.

A couple of weeks ago I also made a clamping jig for the sides as an aid for gluing on the kerfed linings. This jig proved to be a very handy asset when it came to trimming the sides to final height. I first tried to plane them without clamping them to anything but it was virtually impossible to control, the jig however, provided a very nice and sturdy support. The sides were planed with my block plane using long even strokes, mostly starting from the waist area, the peak of the dome, and outwards following the bends of the bouts in order to plane with the grain. The plane was first set to a coarse setting but gradually adjusted to fine setting as I got closer to the marked line.

SOUNDBOARD SHIMS

MARKING SIDES FOR BACK DOME

MARKING THE MISSING LINES

TRIMMING SIDES

SIDE CLAMPING JIG

THE TRIMMED SIDES

FITTING THE SIDES

What to do; Fit the sides or add the soundboard to the neck first?

I have been over this in my head a million times and must confess that I have not been able to come up with a good reason to chose one over the other. It appear there are so many ways to go about this and they all have their strength and weaknesses.

However, In the end I decided on the less conventional of the two and start with the sides. The reason for this is that I hope it will be easier to bevel the edges of the sides to fit the domed top better, a practice that is not normally done on classical guitars.

I touched up the sides dry on the pipe. I find dry bending is a considerably slower process than bending with water and lends itself very well to make small corrections. More so, you will not have moisture leftover in the side and thus minimizing the chance of further movement. After the thouch up, I put them on top of the template and used it as a guide for marking the sides to proper length. Then I drew a line across the side with white pencil using the jointed edge, the one that is going to be attached to the soundboard, to rest the square against. Then the sides were clamped to the bench and the excess was cut off with a dovetail saw, slightly proud of the line leaving a little extra for final trimming with a block plane until they both fit perfectly within the plantilla created by the blocks on the solera.

Before going any further I had to flatten the bottom of the neck slots with a 1mm chisel. I had to get rid of a little hump in the center left from when they initially were cut with the saw. Once flat, I set my sliding bevel to match the taper. Next the distance from the center of the neck to the neck slot was measured and transferred to the sides and the sliding bevel was laid on top and the taper marked onto the side. I did this operation on each side individually as the taper of the two neck slots were slightly different. It was a little nerve wrecking to do as there was a lot to keep control off - which way to turn the sides, what taper went were etc. etc. Well, it wasn't really that complicated but I would have hated to cut the wrong bit of the wrong place. It could easily have lead to disaster!!

The sides where then cut and trimmed yet again in the same fashion as when they were fitted to the plantilla/solera-blocks. I also sanded the edge of the taper a little so the sides would enter the slots easier. One side was a bit tight in the slot and a little sanding should take care of that once they are ready for gluing.

TOUCHING UP THE BEND

MARKING THE SIDES

MARKING THE SIDES

CUTTING THE SIDES

TRIMMING SIDES

SIDES DRY FITTED ON SOLERA

TRIMMING NECK SLOT

SETTING SLIDING BEVEL TO NECK SLOT TAPER

MARKING THE NECK SLOT TAPER

CUTTING TAPER FOR NECK SLOTS

TRIMMING TAPER FOR NECK SLOTS

DRY FITTING THE SIDES TO THE NECK

BENDING THE SIDES.

I finally feel I'm getting the to core of the build. Last week it was the soundboard thickness and this week it's the side bending.

It was a process I was looking forward to with both enthusiasm and anxiety. It was completely new territory to me, as exciting as it was scary. To prepare for this I read up on as many books I could, most notably Cumpiano and Courtnall. I also posted a thread at Luthierforum and got many responses with helpful hints.

It all lead to the fact that, the best way to start bending was to practice on some scrap and so I did. For this I used some flat sawn walnut I had and a cut-off from the bubinga I'm building with. This gave me a chance to gain some experience with different bending techniques and setups.

I started with the walnut, sanded to 2mm thickness, and went at it haphazardly on purpose to see what mischief I would get myself into and then tried to get myself out of them again. All in all the walnut felt very leathery in it's elasticity and I had many problems controlling it. It was very difficult to manipulate one area while retaining the bend in another. I also ended up with some kinking, making it impossible to lay the bent side down on a flat surface without one of the bouts twisting upwards. I tried bending both dry and sprayed with distilled water and the wet was definitely the more responsive of the two.

Eventually, after lots of unruly bending and unbending, I kind of got it into a shape somewhat close to the template I was measuring it against, and left it as such. However, the next evening I noticed that it had curled up quite a bit, meaning an overbend had occurred in both bouts. I should mention that I only sprayed the walnut on the face that contacted the pipe, and my guess is that it could have been a result of moisture still being in wood that had evaporated overnight; Maybe a good argument for soaking or spraying both faces regardless of which way the side is being bent. After some dry touch-up I managed to get it back in shape again.

I also had a quick go at the bubinga. It felt considerably tougher than the walnut. Whether this was because of it's density or the quatersawn grain orientation I don't know but, it took considerable more force to manipulate and once bent, it seemed to hold it's shape much better. I tried bending it wet, both after 10 minutes of soaking and from spraying it on both sides but I didn't notice the wood behaving much differently between the two methods. However, like the walnut, it was considerably less manageable when bent dry. I really tried to push it and did manage to fracture it a little when bending it on the tightest spot on the iron, but only after using considerable force.

I also experimented with the bending iron in different positions - horizontally, vertically, with the flat side facing me, with the round end facing me, etc. I ended up with it clamped vertically to the bench with the tip of the egg shaped pipe to my right. I came to the conclusion that the great advantage with the vertical setup was that my eyes were in line with the pipe as I was looking down upon it, making it easier to check whether I was pressing the wood against the pipe with even force across the side or not. On the down side it is more difficult to see whether you are holding the side perpendicular to the pipe or nor. It also took more muscle to bend the wood compared to a horizontal setup where gravity would be working in your favor.

After these practice sessions I felt a little more confident and eventually took the plunge and started on the 'real' sides. I started by laying both sides on my bench in a bookmatch. After measuring my template with a sewing tape measure, I marked both sides with a line across the position of the the heel, waist and butt and named these accordingly, leaving about 5cm extra stock at each end. I also added arrows to each line indicating which edge was going to be glued the top. This way I was able to avoid bending both sides the 'same way' and thus ruining the bookmatch. However, when I was done bending both sides I realized that I had bent the sides so that the true bookmatch on the inside and that I should have bent them both the other way. It's not a big deal as the sides are perfectly quartersawn thus having a good match on both faces, but nevertheless a shame I didn't get the better of the two on the outside. We live and learn!

After the marking was done, I wetted one of the sides by spraying it with distilled water on each face, put it to the iron and started bending the waist. I used the flatter side of the iron to heat the wood and slowly fed it across with my right hand while pulling it towards me with my left. Soon the water started to sizzle and evaporate into steam and I felt the wood giving in under the pressure. Slowly the waist emerged and after a few goes it fit the template. After cooling it a little I went on to bend the upper bout. This was done in a similar way, though because the bend was more gentle, less force and a faster feed was needed. The upper bout was a little more tricky to match as it had to be done in a more free form fashion, whereas the waist fitted the bottom of the pipes oval quite well. But after a few goes and some areas of unbending and rebending, it eventually settled quite nicely. The lower bout was done likewise, though with even less pressure and faster feed.

After the whole shape was done a few problem areas became apparent - some where the bend had gone bumpy, a few overbends and some areas where the bend had gone off the template and back again. I had to respray the side to correct the more severe ones, while others could be dealt with by bending dry, either locally or by sliding the bend across the pipe applying pressure by wrapping my hand around the wood.

Eventually it was pretty much within the tolerance of ±0.5mm and I left it overnight to cool and dry ready for a final touched up the following evening to get it as close to dead on as I could. More touch-up might be needed once the sides are ready to be glued on.

MARKING THE SIDES

WETTING THE SIDES BY SPRAYING

BENDING THE WAIST

CHECKING WAIST BEND

BENDING THE UPPER BOUT

CORRECTING AN OVERBEND

CHECKING UPPER BOUT BEND

BENDING THE LOWER BOUT

CHECKING THE BEND AGAINST THE TEMPLATE

FINISHED SIDES

FINISHED SIDES

FINISHED SIDES

FINISHED SIDES

SIDES IN SOLERA