November 3, 2023
Current project is my first guitar building project: to build a guitar in the style of a Martin Backpacker Guitar. Below will be a complete build-log of my progress as I build this guitar.
Here is a photo of a Martin Backpacker Guitar, upon which my guitar will be based. The photo from Martin.
First, here is a link to Martin's website and the page for the Martin Backpacker Guitar: https://www.martinguitar.com/guitars/backpacker-series/
Drawings for a guitar in the style of the Martin Backpacker Guitar:
I bought a full size set of drawings from ebay that say they were made by Jesus Raymond. It is an OK full size print, with metric and imperical calculations/dimensions shown for fret locations. I checked the overall dimensions, and they seem correct. That said, the internal construction details such as kerfing and bracing on Jesus Raymonds design are different than those on the Martin Backpacker; perhaps they are is improved recommendations. I will utilize the design elements from Martin, not from Mr.Raymond, as I think Martin must have thought their design through quite a bit and they build very many of these.
I found a youtube video showing the disassembly and repair of a Martin Backpacker, which shows the Martin design of internal braces and such. https://www.youtube.com/watch?v=IcMx2hm6y28. Thank you Dave Moore for this very helpful video. Here are some key photos from Dave Moore's video, showing the inside of a Martin Backpacker Guitar.
Martin Backpacker Guitar front, showing the inside braces. Inside of a Martin Backpacker Guitar.
Inside of a Martin Backpacker guitar. This photo shows the spruce bracing on the inside of the mahogony back of the guitar.
Very noticeable to me is the thick mahogany bracing/liner at the butt end of the Martin Backpacker. To me , this would add both needed counterweight, and also durability for when the guitar is set down. I will be using this very thick liner at the bottom of the interior of my guitar. Current Martin Backpackers are built with sides that are separate pieces of wood from the neck. I plan to build the neck and sides of my guitar from one solid piece of wood, as I think earlier backpackers were made.
My markups of the drawing are shown here, to bring the drawings I bought back to original Martin design. Red shows bracing that is not Martin's design, in blue and in green, you can see what I will build to build one closer to Martin's oem spec.
I thought the bridge on the drawing also looked far too thin, so I will make it 11/32" thick as shown in my sketch below.
Other items that I will not make according to Raymond Jesus' design are:
- The nut on his drawing looked narrow and short, I will make one 1/4" wide and 5/16" tall. NOTE that final dimensions will be determined when I finish the guitar and I will adjust the NUT height to achieve the correct spacing of the strings above the fretboard. Same story with the bridge and saddle, I will make final adjustments and dimensions may be different than my sketches/notes here.
- The fretboard on the drawing was 5/32" thick I will make mine 3/16" thick
Materials I Used For Building My Backpacker Guitar
Some ideas for places to look for these materials would be: Kettle Moraine Hardwoods, Stewmac, Ocooch Hardwoods, Bell Forest Products.
Large Mahogany post in the back, for the neck and body, Sitka Spruce for the braces, book-matched Sitka Spruce for the front, Mahogany for the back, Birdseye Maple for the fretboard, Indian Rosewood for the bridge, unbleached bone for the nut and saddle.
Unbleached bone for the nut and saddle
I went with medium jumbo precurved frets
Extra light guitar strings on this wee little guitar. I saw a recommendation for the Dean Markley Extra Light Signature Series Vintage Bronze Acoustic strings, so thats what I went with.
Guitar strap buttons
Wilkinson Tuner Posts
Tools: Straight edges, squares, sliding bevel, japanese pull saw, planes, xacto fine tooth saw, hammers, mallets, compass, awl, chisels, shinto rasp, spoke-shave, small and large files, files, drill bits and large forstner bits, clamps, measuring calipers, dremel, drill press, table saw, surface planer, band saw, random orbit sander, belt sander, miter saw, razor blades, bench vise....etc...
Now for some specialty fixtures and tools that I think will help me build this guitar:
Making a Saddle Routing Fixture
I ordered all of the wood for the guitar (learned these fine guitar-worthy woods are called "tonewood".). As I wait for it to arrive, I will build a little jjig to guide my dremel/router in order to make a properly oriented, and straight, and correct length groove in the bridge for the saddle to press into. A sketch of my design is below.
Gluing up the bottom plate and the middle layer that includes the recess for the bridge to fit snuggly into. I wil place the bridge blank in the recess, clamp of the top frame/router-guide frame, and then rout the slot. I drilled a couple holes through the bottom plate to allow me to pop out the bridge when I'm done.
Here are the completed upper and lower sections of the fixture.
The red piece is a piece of scrap wood where the bridge will fit.
And here is the fixture clamped up and ready to use.
Making a Fret Saw
Or more accurately; improving a fret saw. I bought a fret saw to ensure the width of the blade was correct, but saw some photos of other fret saws that had nice adjustable depth-fences built right in. I decided to make an adjustable brass depth gauge/fence for my fret saw.
As-purchased fret saw, plus the 1/8" x 3/4" brass bar I bought, along with brass machine screws, wing nuts, and washers.
Holes drilled in the saw blade , slots cut into the brass depth gauge/fence.
Completed fret saw with the addition of an adjustable depth fence.
Now, On With The Show! Building the Backpacker Guitar:
Making the nut and the saddle from unbleached bone
I cut the saddle to length with a fine-toothed x-acto saw, and used a file to shape it, then sanded with fine sandpaper.
Unbleached bone nut blank was oversized a bit, which was nice. I sanded it down to 1/4" thick on my bench top belt sander and then to 5/16" tall on my benchtop belt sander.
Sanding the blank to 1/4" wide, 5/16" tall. Then I cut it to length with a fine tooth x=acto hand saw.
I hand filed a slight arch into the nut, along with the front to back taper, and then marked out the string locations in pencil,
Using a radiused mini-file to file in the string grooves into the nut.
Finish filed, shaped, and sanded unbleached bone nut for my backpacker guitar. I will file the grooves to final width and depth later.
Photo of a Martin Backpacker nut, photo from Martin.
Cutting the saddle blank to length.
Using a file to shape the saddle.
Unbleached bone saddle
Making the Front and Back Pieces
I straightened and trued up the edges of the two bookmatched sheets of Sitka Spruce and the glued them up over a piece of plastic. I used two pieces of scrap plywood nailed along either side to compress the two thin sheets. I put some objects on top along the joint to keep it flat.
Bookmatched glued up front, made from Sitka Spruce.
Using my thickness planer to plane the front to 1/8" thick.
I will make the back from a single piece of solid Mahogany, 1/8" thick.
First I drew out the shape of the back on the mahogany, next I will use my bandsaw to cut this piece out by I will cut at about 3/16" oversize and trim it down to be flush with the body after gluing it up.
Here are the finished rough blanks for the front and back
Blanks cut from Sitka Spruce for the front and back bracing
I used a plane to make this nice curved / half-oval profile for the reinforcing braces. Planed to shape, then sanded.
Solid chunk of Mahogany, 1 5/8" thick, just like the body. I carefully traced out the shape of the bottom of the guitar from the plans on to the wood.
Here is the bottom reinforcing block for my Martin-style backpacker guitar.
From this photo of an actual Martin Backpacker Guitar, notice the taper in the stock at the end of the piece. The reinforcing piece is not perpendicular to the back and is not flush to the side or glued to the side; it is tapered back. I will do it that way.
Braces shaped and glued to the back.
Gluing the butt end block in place.
Laying out bracing and reinforcing pieces that will be glued to the underside of the front.
Precut under-front pieces ready to be glued in place.
Glueing up the bracing and reinforcements for the underside of the front.
Making the Fretboard
The fretboard will be made from birdseye hard maple. First I planed it to the correct thickness, then I cut it to the correct max width and length. Then before cutting the tapered shape of the neck, I marked out the fret locations and used a square to mark out nice perpendicular lines for the frets.
Using a square to draw cut locations for the fret saw.
Cutting the fretboard to length.
Cutting the fret slots with my fret saw.
All the fret slots are complete! That was fun.
Taper drawn out on fretboard now that the frets are cut
Here is the fretboard with fret slots cut and the neck taper roughed out. Next I will form a slight radius on the top face of the fretboard.
Radiused top of the fretboard
Making the Rosewood Bridge for My Backpacker Guitar
I practiced using scrap wood before making the Rosewood bridge. I needed to trial and error the slot cutting jig especially and try different router bits. I wound up buying some tiny metric slotting router bits that worked best as 1/8" bits made a slot to big. I also used scrap wood to get the depth of cut just right.
First , I planed it to .344" thick. Then I cut it to width and length.
Then I tapped the bridge blank sunggly into the saddle slotting jig I made.
I then clamped on the upper portion of the slotting fixture.
Using my Dremel as a router to cut the slot.
With the slot routed, I drew out the perimeter shape of the bridge and cut it out on a band saw.
3/16" holes drilled and now using a reamer to form a nice taper into the holes. I will use solid bone bridge pins.
I used this wee little saw to cut slots into the bridge that will allow me to to use solid bridge pins. I will clean up these slots.
I carefully marked the location and then glued the bridge to the front.
With the bridge mounted, I drilled the peg holes through the front piece and reamed the newly drilled holes lightly.
Making the Neck and Body for My Backpacker Guitar
It seems that the current version of the Martin Backpacker Guitar has body-sides that are glued to the neck. I have heard that older Backpackers had body sides that were made in one single piece along with the neck, and that is how I will make mine. I started with a 3"x3" piece of mahogany that is a bit longer than the overall guitar.
My piece of Mahogany was super straight along one edge, but had a minor curve in the other. I used a hand plane to create a straight edge of the imperfect one.
Using a stainless steel yardstick to check straightness of the previously curved edge. Now it is nice and straight and all is well with it.
With everything square and straight, I ripped my stock down to 1 5/8" x 2 7/8" on the table saw
I miss things from time to time, and here is an example; I checked the height of the sides of the body and it is 1 5/8" but up at the transition from the body to the neck the top side of the piece of wood needs to step up and 1/8" at the point where the top ends, so the total height of the single-piece neck/body/piece would need to be 1 3/4".
sooo....... I glued a piece of the mahogany left over from the original 3"x3" post to the neck to account for this step up. I measured the exact location where the top ends and this is where I began the glue-up of this piece to the neck.
Marking out the neck.
Cutting the neck profile on the bandsaw. I made the cuts with sides of the lumber on the bed of the bandsaw first. Second step will be to cut the taper into the neck looking down from the top. but do this cut first.
Still cutting the side-view profile.
I am pleased with the results so far. IT's all my little bandsaw has in it to make these cuts in approx 3" thick stock. She's gett'in it done.
With the side profile cut out, I layed out the drawings on the top surface of the body/neck. The small details of the lines/shapes I am using are not the lines on the drawing I bought, note the curves above vs the straight lines on the drawing where the body transitions to the neck.
Drawing the headstock
I am very pleased with the roughed-out neck.body piece.
Now it will be an army of spoke-shaves, chisels, knives, files and sandpaper to carve this neck to shape.
Using a chisel and mallet to rough carve the neck shape.
I used a spoke shave and chisels to shape the neck and the transition from the neck to the body
Further shaping with a Shinto rasp.
Rough shaped backpacker guitar neck.
Sanding.......
Setting up the big forstner bit
Hole is cut and now I will use the table-saw to cut the 1/8" thick body sides.
I used a bandsaw to complete the tablesaw cuts,
Here are the wooden backpacker guitar pieces ready for assembly.
Laid out locations for tuner posts and used an awl to set the locations for the holes.
Drilling the tuner post holes to 3/8" didn't go well. split the whole piece and needed to glue it back together and the I left the clamps in place to ensure no further splits occured. All told I think it survived this step, but I should have had higher speed drill rpm and better control of the drill to avoid all the splits and wood lifting seen in the photo. Luckily their are collars on the tuning post that will cover up my mistakes.....
Making the bending form for the body
To pre-bend the curved sides and the curved bottom wall of the body, I will be soaking the wood to be bent in hot water and then pressing it in a form. I have a few different sizes of stem boxes, but I do not want to steam the neck of this guitar so I will just soak the body portion and leave the neck above water. I made a form out of a 2 x 12 pine piece of lumber.
Transferring curve points from the drawing to the form by using an awl through the paper into the wood below. Next I will "connect the dots" with a pencil on the 2x12 beneath.
Form sketched in pencil and now being cut out on the bandsaw.
This hole doesn't need to be in the form, it won't hurt either and I wanted to test my 2.5" forstner bit so I did so on this 2x12. I don't normally change rpm of my drill press but this test showed me I need to slow this baby down for this 2.5" bit.
Completed backpacker guiter body forms. BE picky and make sure you get a straight and true 2 x 12, which is not easy.
Bending Pieces and Assembling the Body
Soaking the portions of the body that need to be bent in piping hot water. I left it to soak for 1.5 hrs.
Clamping the soaked wood into the forms.
I unclamped the bent bottom piece and clamped it to the guitar body / butt brace.
Then I trimmed the visible bottom piece to length to match the brace.
Painting a little design that will be visible on the inside of the back through the sound hole.
I love Crocus! Here is my little design painted on the inside of the guitar. Paint is still wet but it will dry to a consistent color.
Weaving a Guitar Strap
I set up my loom and will weave a guitar strap. I'll attach leather ends with the button holes.
