How to make an Alpaca guitar

This Wednesday began early. The kids were up and I could feel Tucker bounding from spot to spot as his morning eagerness tested the sturdiness of the hilltop ranch house and rattled the spring box of my cozy twin bed.

Chris had met Bill and me at the bus depot in Lebanon, New Hampshire. Our longest delay in today's journey had been for two hours at the end, in Boston's Logan Airport. The next Dartmouth Coach would leave terminal C at 6:55pm. A Reuben sandwich, fries, and a $6.95 pint of IPA at the Ale and Eatery pacified my intolerance for idle waits.

Ernie appeared to be a well seasoned and mellowed coachman. His 40 foot behemoth MCI Dartmouth bus had no foes on the highways north towards our homes for the next few weeks in Barnard, Vermont. I had loaded a version of casino craps onto my iPad and I was soon to discover that for the combined graces of the craps game, the impenetrable view through the glazed windows onto the unlighted scenes outside, and my middle of the coach seat, I was kept non-witness to the hazards being presented as we were hurled through a severe northeastern blizzard on snow packed roads.

Sara had been sound asleep when we dropped Bill off at the Fan House, Sara's B&B in Barnard. For the first few minutes Sara thought we were guests scheduled to arrive at the weekend. Once fully alert, we had a nice, albeit short, visit.  Chris then forged his jeep over the snow and ice packed road to his half mile driveway, tucked into the hillside half way between Barnard and Bethel. It was a good feeling to be safely inside his generously wood-warmed front room.

We waited until late morning to leave for the short drive to Bethel. Over the years refuse from the kitchen garbage disposal had slowly built up a blockage in the cast steel sewage byways suspended beneath the sprawling ranch style home. A plumber's assistant, and his employer had been called in to locate, and destroy the hidden obstruction site.  Chris and I got to avoid the visit.

Chris has rented a couple thousand feet of street frontage space, which is soon to become the factory for Alpaca guitars. The building at 216 Main Street was last occupied by a grocery store. There is only one through street in Bethel, Vermont.  There are no stop signs on Main Street. A sidewalk separates the old store's aluminum clad wall, with two protruding windows, from the occasionally trafficked roadway. As Chris crunched the Jeep's wheels into the packed snow at the curb's edge he noticed that a snow blower had worked the street since his last visit. The aluminum siding and windows were blotched with the melt of recently hurled snow. 

 

My introduction to the inside of the new shops was visually toxic. I had no trouble picturing many ways I could help Chris get set up and running. Yesterday evening the city board approved a code variance which would permit Alpaca Guitar to manufacture within the city limits. There had been only one objection voiced by the audience of four and Chris had comfortably addressed her concerns. Up to this time, what Chris had done for improvements had been limited to furnishings which could be easily relocated should the council not approve his request.

Today our initial job is to build a wall to divide the entry area, which is going to serve as office, public reception and finished product display, from a larger space to be used for finished tooling and assembly. The finishing room will be noisy and interruptive to other business activities.

 

The Alpaca guitar will be molded, using plant derived epoxy resins and fabrics made from plant fibers. A lot of thought and research has gone into manufacturing a very eco-conscious musical instrument. The same spirit guided the design of the new wall.

Two by four studs were used for the framing of the wall. From that point on, it was all recycled. I held an image in my head about all of the magnificent multistoried red barns populating the fields and farm yards on the road from Chris' home to downtown Bethel. They aren't, however, all used for the betterment of livestock. Some are used to hide treasure troves of no longer needed or wanted building products. In one barn Chris found a dozen old double hung windows. In another, he found a stack of doors; some solid core, and some hollow core. We needed some of both kinds. Where the new wall didn't hold windows, it needed siding. A pile of 15 foot long edge trim planks was found on a refuse pile at a nearby sawmill.

 

In two day's time, we had the wall completed. All of the windows have scruffy, peeling white paint. The doors are battered a bit and trimmed to fit. The plank siding gives the wall a very colonial cabin motif. The wall will serve its design purposes: isolate the noise and small mess involved with the guitar's assembly, permit an easy public viewing of the building process, and portray the owner's personal interests in not wasting nature's resources.

 

The former grocer had large cooler. Outfitted with several self-closing glass doors, this room can be used as a quasi clean room where the Alpaca guitar molds can be laid up and vacuum cured. Precut fabric will be carted in from the finishing room and cured product will be carted back for final trimming and assembly. The room has two glass end doors which need to be removed and replaced with a set of wooden doors for cart access. Removing the old doors was quickly done.

 Once the room had been opened up, we moved three of the 4x8 tables Chris had made into the cooler. The tables sat well and there will be ample room to move about. We located where the vacuum pump could be located in the upstairs of the adjoining section of the old store. It is a short and direct run for vacuum lines to the layup room, and there will be little noise heard from the pump.

 Parts for the CNC machine were starting to dribble in via UPS. Now that we had three less tables to work around in the finishing room, we could dig out the plans and assemble the MDF plywood needed to construct the very large torsion table which would hold the CNC milling hardware.

The closest source for the MDF is Home Depot, in Lebanon. We spent the rest of the day driving there and back. Six of the large sheets were required. We were able to have them all cut to their largest single dimensions while at the store. This made handling the pieces much easier. A full sheet of 3/4" MDF weighs over 90 pounds. Chris also picked up a finishing nail gun and a gallon of Tightbond II wood glue. We would go through over 3 pints of glue on this single table. All of the cut pieces fit on the jeep's roof rack and we were back and unloaded just before the phone rang for dinner.

 The three sheets of 3/4" and three sheets of 1/2" MDF had to be further cut to exacting dimensions for the honey combed inside of the 5-1/2" thick table top. Chris, Bill and I set up a cutting assembly line. By the end of the day we were all coated in sawdust, but the icky part of the project was finished. Tomorrow Chris and I would put the 120 some pieces together. After dusting off and vacuuming the room, we all headed home.

 The CNC router's movable gantry mounts to the torsion top table. The computer controlled router moves left and right, and up and down. It does this in micro stepping movements controlled by chain driven servo motors. Because of the rapid changes in motion of the heavy router, the table cannot have any ability to rock. The gantry assembly requires a table width of 52", exactly. The length of the table is to be 126". This will permit the cutting of a 4x8' sheet of plywood.

 We built the table upside down, beginning from the 3/4" top layer. We took about a half hour gluing up a single course of the honey comb interior. We would then clamp it and set the timer for half an hour, the minimum clamp time for the Tightbond glue. There are seven courses of honey comb inside the table. The final task was to run a glue line on the top of the entire honey comb structure and then clamp on the two pieces of 1/2" MDF that form the bottom of the table top. 

I finished the day by mounting triangulation braces on the table to be used for the base. The base can't wiggle, either. Tomorrow the glue will be fully set and we can mount the top to the base. The torsion top weighs in at just under 400 pounds. It will take four of us to turn it right side up and to position it on the base.

 Chris's middle son, Elliot, is a budding construction engineer. Tonight Chris swayed Jennifer into letting Elliot skip school tomorrow so he could put his native talents to use while helping his dad assemble the gantry system. The gantry is a real life Lego-maniac’s dream come true.

Chris and I quickly cut out and assembled one more finishing table. Having moved three tables to the molding room, Chris felt he would need one more table in the finishing room. Bill came over just before lunch time. He and Chris got stuck into mounting rails on the torsion box for the gantry to roll on. Like a narrow gauge railroad, the gantry rails needed to be precisely parallel. The measurements came out perfectly.

The gantry holds the spindle, a router without handles, and it holds the servo-motors which will guide the gantry up and down the length of the table, the spindle back and forth across the gantry, and the spindle up and down on the gantry as it is traveling the length and width of the torsion table. The spindle itself is mounted on a miniature gantry gliding on rails mounted on top of the main gantry. The smaller gantry permits movement of the spindle across the table. But wait, on the side of the small gantry the spindle mounting block can move up and down on its own set of rails. As a result, the spindle's cutting bit can traverse the whole surface of a 4x8 foot plane and do it while moving up and down a 9" height. The X, Y and Z axis movement of the spindle in done with fine chains and sprockets which can control the bit's position to within 0.001mm, or 1 micro.

 The description just presented is to illustrate the complexity of this erector set. Because it needs to be constructed in a very a, b, c manner only one person can effectively be involved; the task is left to Chris. The assembly process has its own built-in agitators: holes for the bolts had been drilled at the factory at such a close tolerance they required each bolt to be screwed through the wood before it could then be screwed into the nut; the on-line instruction manual contained several typo errors, and the coup de grace was that the precut brackets for the spindle didn't fit the spindle motor size Chris had ordered.

While Chris labored on the CNC machine, I set up the upstairs vacuum pump, vacuum tank and 1/2" pvc vacuum lines to the mold room. I mounted the 1/2" pipe about 20" above the two curing tables. At 18" intervals, I cut the pipe and installed a T-junction, 10 of them altogether. On each T-junction I mounted a tube bib to connect to 1/8" i.d. vacuum hoses. Each vacuum tube can be opened, or closed, with a pinch clamp. The tube then connects to a polyvinyl bag holding a fresh mold. The vacuum process evacuates any laid up air trapped in the fabric.

Chris decoded the CNC computer and had the gantry gently moving about the torsion table in the X and Y axis directions. It may be a couple of days yet before the Z axis replacement pieces arrive. When they do, he will be able to calibrate the spindle, router, over its whole range of motion. On top of the torsion table will be a 4x 8 foot of 1/4" to 1/2" plywood, or MDF. This sheet will provide over shot protection for the torsion table top. When the scab sheet is attached, Chris will program the spindle to skim over the new layer and shave where needed to achieve a perfectly flat surface for the spindles reference.

Matt and Andrew were coming to the shop today to begin construction of the tote bags which go with each guitar. The bags are to be made out of organic cotton canvas. Chris has received the 67" long, 80 pound roll of canvas. The roll has been hoisted onto the rack behind the fabric cutting table.

 Each bag will use a piece of cotton that is 51" long and 14-1/2" wide. From the large off cuts of MDF, I laid out lines to run the skill saw down. Grooves about 1/4" deep will permit scissors to be guided accurately for the cuts.

 

Chris worked with Andrew on the most economical way to cut the large strips. Chris used one of Jennifer's sewing machines and quickly stitched the first bag and verified the Alpaca guitar fit snugly. The first time is a winner. Matt was given a quick lesson on machine stitching 101 and turned loose with the strips Andrew was making. Alpaca Guitar, Inc. has its first assembly line up and running.

Andrew felt the front area need some sparking up. He and Matt teamed up to achieve what may have seemed to them as the impossible. Matt cleaned the deck over the mold room, made mounts to hang the Wi-Fi and telephone equipment in the phone hallway, and worked atop the ladder and removed all of the display peg board which once surrounded the inside of the old grocery store. Andrew visited the hardware store and returned with a quart of brown paint to dress up the window trim. He foraged in the back recesses and came out with a gallon of white paint to be used on the walls. Things quickly began to take on a fresher look.

Chris has worked up programming which commands the CNC machine to carve out words. The spindle is still not mounted, so only the X and Y axis are functioning. In lieu of a spindle, Chris taped a pencil to the gantry. He taped paper to the top of the torsion table. Instead of a carved piece, Chris' result was a very accurately drawn banner, which read, "Chris"; a small step for mankind, but a huge leap for Alpaca Guitar. It was exciting to see the output of this complicated piece of equipment.

The Z-axis spindle brackets finally came in. Chris had gone to bed last night with a stuffed up head. He slept in and stayed home today. Bill joined me at the shop and together we muddled through this last part of the erector set. The final hook up will be left for Chris.

I visited the hardware store across the street and bought some 4" flexible dryer duct, a few angle junctions and some large straps. My next job was to run the ducting and hook up the CNC vacuum system. This task took the best part of a day. The final thing needed for the vacuum system was to install a ground strap from the metal duct to a nearby electrical spot. A huge amount of static voltage can build up on this system and if it is not well grounded, it could seriously shock, or worse, ruin the computer.

 

The CNC was finally working. Chris began experimenting with simple word etchings. He needed to spend time filtering through the many computer commands and options. While Chris learned the machine, I cutout, planed and laminated 2x4s into stock which he would use to make the several guitar forming mold plugs. Together, we created several boxes of sawdust, which would soon be used to cover the floor of Chris' chicken coop. No wasted wood here.

 

I did a lot of laminating. The learning curve on the machine was very steep and unforgiving. We will have watched the machine carve for four to five hours and then a Y axis sprocket would spin loose. This caused an erratic movement of the spindle ruining the work.

One day we planned to do no more carving until we resolved failing parts on the CNC. It turned out the sprockets and attached bearings had been made in China. Glue had been used to hold the sprockets to their bearings. Under load, the glue broke and the sprockets spun freely, causing no movement. We took the machine apart and used a punch to peen all of the sprockets. At the end of the day we were ready, and confident we had improved the machine.

 Over the next two days we carved a successful plug. What a good moment that was. The guitar's body had a shape. Now, we needed to turn attention to creating a plug for the soundboard, or top. I was back to laminating more wood while Chris prepared the programming.

 

The body plug was far from finished. The machine did two complete carves on the same block of wood. Each carving took a full day. The first carving created a rough cut. The rough cut took wide and deep passes over the block. This left a terraced appearance to the plug. The second carving session is called the finishing cut. This cut is at right angles to the rough one and removes all of the terraced steps. After the finishing cut is complete the plug is ready for hand work on the bench.

 It took several days of sanding to remove all of the residual imperfections on the plug. We needed to make sure I didn't over sand the bottom of the plug because its shape was critical to properly mate with an extension piece. To help avoid this problem we bought a couple of pieces of sheet metal and Chris set the program to just cut out the shape of the bottom of the plug. We then screwed the metal to the bottom of the plug. My mission was now to sand until I was hitting metal on all spots. The metal shape was then transferred to the extension piece and I got to do it all again.

A week and half later I was ready to apply lacquer to the assembled plug. The plug was made up of three separate layers. Each layer created a line which required multiple applications of wood putty. In the wait times while the CNC was cutting and while the later coats of lacquer were drying, I was kept busy with infrastructure jobs.

One sunny day I spent spray painting a new white cover on the weathered outside vinyl lath.  The building has seen a couple of decades since cosmetic attention has been paid to it. Another day I scraped and painted the eave. I installed a knob and lock on an inner door and found the pieces of a threefold door which I made into a one piece door. More scrubbing, and then some paint was applied to the inside of the front door. I refinished a bench on the sidewalk near the front door. The list of fix ups was long.

After each lacquer coat dried, I sanded imperfections and discovered new spots where spackle could be used. Finally, I had a plug that shined in all places; was smooth to the touch and ready for the next step.

 

Before a plug can be used to make a mold it has to have a mold release applied. In the old days, the mold release was commonly several coats of wax. Wax didn't generally adequately fill in small, micro blemishes, however, and its use has been replaced with polyvinyl alcohol (pva). Several coats of pva are sprayed onto the mold until a colored surface is obtained. Pva forms a barrier between the plug and the resin used to make the mold. No resin touches the plug. When cured, the mold and plug are then washed with water.

The secret to applying pva is to do so without creating runs or other spray blemishes. Since the pva becomes the plug, as the resin sees it, blemishes will show in the result. I had set up an outback spray table so pva could be applied without the need for venting. At the end of the day Chris applied a coat to the plug. We brought it inside for the night and went home.

At noon today Rebecca is going to pick me up at the office and drive me to Lebanon to catch the bus to Boston's Logan airport. I got up early and drove the boys to the bus stop, where we said quick goodbyes. That was sad. After breakfast I said goodbye to Jennifer, and Chris and I loaded bags into his jeep. I still had four hours I could use to help at the shop.

We discovered that the pva applied to the plug last night had run. I washed it down, dried it off, and got it ready for a series of re-sprays. I used a heat gun to speed the drying steps. We put on five coats of pva before we called it good. The end result was a satin-like surface. We both thought this would be more user friendly that a mirror finish. If it doesn't look and feel good, it can be changed on the next mold cast.

Rebecca pulled up outside on schedule. It was hard for me to say goodbye to Chris. We had spent six weeks, working each day, and I was leaving on the eve of the result. Chris is a great team leader and Alpaca Guitar Company will do well. I look forward to a return, with Anne, in our new coach to see how the production line is working. Go get 'em Chris.