August 25, 2009
Cut out and shaped all the braces for both 905 and 906. Shaping is an approximation of the final shape of the braces, which will be planed and chiselled to their final shape after they are attached to the plates.
Finished gluing bracing for top and back for 906.
X-bracing goes in first.
Only time enough today to get the back bracing for 905 installed.
August 24, 2009
My brother in law Bim’s sister Lisi sent me a mandolin for repair and it arrived today. It’s very similar to the Romanian mandolin (Repair 9001) given to me by Joel Tepp.
Lisi’s mandolin is 50ish years old, with a gourd shaped back and some serious issues. It sat in an attic for multiple decades, probably going through sever temperature variations and with the strings fully tensioned the whole time. It essentially compressed itself over the decades.
This is a view of the butt end from the top showing how the tailpiece pushed against the top, compressed against the heel block and binding and shoved a center piece of spruce toward the soundhole.
The above shows the cracks in the spruce top. The soundboard dipped, once there were cracks and nothing to keep it from dipping. Another side effect was that the soundhole bowed up in response to the pressure from the cracked top.
Finally, the decorative back pieces have come loose and will need reglueing.
I think the best, and least intrusitve solution will be to remove the center panel on the top where it is cracked on both sides, get in and flatten the soundhole and add new bracing, reinstall the cracked piece and craft a new bridge.
August 23, 2009
The rosette is in and the soundhole is open. I’m ready to install braces.
Rosette is a bit dull and not fully down to the spruce surface. It will all come clean with fine sanding after the bracing and install to the sides.
August 22, 2009
Went back down into the man cave and finished sanding the top after it came out of the joining jig.
Such a fine piece of spruce. The joint is wonderful.
Located the center hole, drilled the 3/16″ pilot hole and mounted on the workboard.
Routed the channels for the rosette.
Started with installing the inner and outer ring. After they set and I can scrape them down, I need to widen the center channel just a tad to accept the bwb/teflon/bwb. I’ll pull the teflon then insert the paua.
August 22, 2009
Thickness sanded the walnut back in the drum sander.
Used a plane to joint the sides, then applied glue in preparation for the joining jig.
Aligned the back grain and clamped into the joining jig.
Also jointed the top, after planing down in the planer. Used a shooting plane to create seamless joint.
Later this afternoon, I’ll remove the back from the joining jig and join the top. Tomorrow I should be able to install the rosette.
August 22, 2009
Earlier today John emailed and asked how I bent the sides for his walnut OM. I responded with a quick description, but thought it might be interesting to you, my dear readers, to demonstrate with a little storyboard.
I use a side bending machine which I constructed, modelled after the Fox Side Bending Machine devised by Charles Fox. I have various forms for the different body sizes I build. First step is to insert the proper form into the bending frame and clamp down to the workbench. Next I lay out the beginnings of the sandwich, which is (from the bottom up) stainless steel, heating blanket, wood, stainless steel.
The magic silicon heating blanket (developed by rocket scientists as NASA) is the same dimension as the stainless steel plates. It’s layered onto the first stainless steel plate.
The side plates have been thicknessed down to at least .110″, and the outside, waist location, and neck end have been marked.
One side is bent at a time. This side is the “left” side, and the waist mark will be at the back of the bender as you face it from the workbench side. I spritz it lightly with distilled water and wrap in foil.
The wrapped plate is then placed on top of the heating blanket. This is very important, as regulating the temperature is very tricky, and if the wood were to burn slightly, it would do so only on the inside, protecting the outside from telltale burn markings.
To complete the sandwich, the second stainless steel plate is placed on top. I mark the top piece of stainless with the waist location for alignment with the waist clamp.
An aluminum bar under the sandwich is spring loaded against the waist clamp, and the sandwich is held together with simple spring clamps. I use an electronic meat thermometer to measure the temperature of the heating blanket.
Once the sandwich is in place, and the waist clamp is brought down to where the sandwich is just touching the upper and lower bout edges, the blanket is plugged in to a timer/variable set switch and turned on.
I watch the temperature gauge, and when it gets to 300 degrees, I begin advancing the screw press on the waist clamp slowly until it is within 1/16″ of being fully screwed down.
By the time the waist clamp is fully screwed down, the temperature will have risen to 350 degrees. (These temps work for me, and are relative to this setup. The actual temps may be higher or lower, I really don’t know). I ramp back the adjuster on the timer slightly then pull the spring loaded presser bars over the top of the side. I use an automotive brake spring tool to pull the springs over the posts.
The spring loaded presser bars are drawn slowly over the sandwich toward the ends. I pull the lower bout pressers first, followed by the upper bout to allow the tighter bends to sit under heat longer.
I wear heat resistant gloves during the process as the thing is damn hot.
There are two bars on the lower bout end to help keep bulges from arising.
The upper bout bend must be taken very slowly, as this tight bend is prone to cracking.
Once the bends are complete, the timer is unplugged and the side can sit in the bender overnight.
Once the side is removed from the bender, it should be placed immediately in a mold. If a mold is not available, the side can be taped to prevent the bend from self straightening, which is what it really wants to do. The pictures below show the progress of removing and taping. Note the slight burn discolorations on the inside of the side. This is minor (AND on the inside), and can be sanded off.
August 21, 2009
I started construction in earnest today on guitar 905. This is the walnut OM for John. I’ve got the drum sander working to perfection and it is cranking out some very nice thickness sanded side plates. After sanding the side plates down to around .110″ I set up the bender for the OM shape and put the first side in. It is now sitting until tomorrow when I’ll bend side 2.
The back will go into the thickness sander tomorrow. It’s a really nice piece of claro walnut with lots of flame.
The top is a very impressive sitka spruce with straight tight grain. Even before planing, it has a rich tone. I’ll run it through the planer to bring it down to thickness.
It already has a nice amber color, so may not need much if any tinting to give it that warm old look.
John is still deciding on the fret markers and is tending toward simple. From simplest to less simple, here are some options:
Using 3mm paua dots only:
3mm paua dots only, doubled up on frets 5 and 12:
Doubled up dots replaced with paua notched diamonds:
Each photo also shows the ivroid strip which will bind the fretboard. Note that this fretboard has not been tapered yet.
August 21, 2009
Installed new sandpaper on the drum sander and thicknessed the back down to .115″. Orbital sanded the back down a few more thousandths, redrew profile and installed the back reinforcement strip using the go bar clamp. Finished kerfing the sides and used the radius dishes to fine sand the top and back edges of the sides.
August 20, 2009
Got the sides bent and inserted into mold. First step is to install neck block.
Then end (butt) block.
After sufficient drying time, it looks like this.
The sides are just at the limit in size, so I did a little bit of radius sanding with the 30′ dish, and installed the top kerf with a large amount of proud at the waist.
Neglected to show the soundhole removal end result yesterday.
Tomorrow, I’ll radius sand the top again with the kerf in place to get it fully aligned, then tackle removing side material from the back side in preparation for the 15′ radius sanding of the back, followed by installing the back kerf.
I procured a new roll of sandpaper for the drum sander and should be able to bring the walnut sides down to thickness for the bender. I should be able to bend the walnut for 905 and get it into the mold. As well I can thickness the spruce top and walnut back and prep the bracing for both 905 and 906. If there’s time, I’ll join the top and back plates for 905.
August 19, 2009
As 901, 902 and 904 cure (due date, August 30) I have started building guitars 905 and 906. Today, concentrated on 906 after drum sanding the side plates. Carl chose to change the top from Engelman Spruce to Sinker Redwood. I already had the redwood plates joined and thicknessed down to around .130″. I routed the channels for the rosette, installed, scraped down, then cut out the sound hole.
The following picture shows the Dremel tool and circle jig I use to route the channels and cut out the soundhole.
Koa bends very nicely. I thickness sanded down to around .100″ then bent side one, let it stand in the bender overnight, then placed in the mold.
Side 2 is bent and sitting in the bender until tomorrow morning, when I’ll remove it, cut the ends and place in the mold next to its’ brother and glue in the neck and heel blocks.
I have two opportunities for headstock veneers in Koa. I’ll let Carl decide which he likes best.
Also, Carl was looking for fretboard inlay with a vine design. Sent him some examples:
