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J
Could you elaborate on your neck joint? How did you match the curve of the neck heal to the body?
Steve

What is a negative angle for a classical guitar? Is that the forward tilt of the neck relative to the body?

Gluing the binding onto the fretboard. I use this setup on my router table. The fretboard and binding are sandwiched between two pieces of wood with clamping pressure provided by the featherboards pushing everything against the fence. I wick thin CA into the joint between the binding and the fretboard. I made this setup years ago out of three pieces of scrap plywood and it works so I've never fancied it up.

Attachment:

Octave Mandolin 36.jpg

A very informative post and a lovely looking instrument. Can you advise what diameter strings you are using for your 21 inch scale length?

I finally got around to recording a demo of this octave mandolin. This is my friend Dean Snider playing an instrumental piece he wrote for his daughter's wedding called Madison's Procession.

For those who may be interested, this was recorded using two Shure PGA81 mics in ORTF configuration into an iRig Duo Pro and then into an iphone 13Pro. No audio processing was used.

https://youtu.be/Ihd9DnvxjSs

Author:	J De Rocher [ Tue Feb 15, 2022 3:27 pm ]
Post subject:	New octave mandolin
I finished up this octave mandolin two weeks ago. It’s the first one of a new design. The previous ones I’ve built have a small body about the size of a baritone ukulele with a 10.5” lower bout and 14” body length. For this one, the body is parlor guitar size with a 13” lower bout and an 18” body length. I was looking to get a fuller sound with more low end in particular and it does both. Adirondack spruce top Curly birdseye maple back, sides, rosette, and headstock plate Curly big leaf maple neck Cocobolo binding on body, fretboard, and sound hole Indian rosewood fretboard and bridge Tuned G D A E one full octave lower than on a standard mandolin. The open G for the lowest string course is the same as the third fret G on the low E string on a guitar in standard tuning. The open E course is the same as the open high E string on a guitar. The total string tension is about 170 lbs. Attachment: Octave Mandolin 01.jpg Left to right: Standard F-style mandolin, small body octave mandolin, the new octave mandolin, dreadnought. Attachment: Octave Mandolin 62.jpg I’ve settled on using a 21” scale length. Octave mandolin scale lengths I’ve seen and played range from 19” to 23” (which is a huge range compared to acoustic guitars). The shorter lengths are easier to play but the low string tension results in the low strings rattling against each other within courses with anything more than moderately hard picking. The longer lengths make it hard to impossible, for me at least, to play fast single note stuff particularly in first position because of the long stretches caused by the tuning in fifths. A 21” scale length is a good compromise between playability and enough string tension to minimize string rattle in the low string course. I’m going to post some photos of the building process followed by some photos of the finished instrument. Thanks for looking. Joined top and back plates. Attachment: Octave Mandolin 14.jpg Routing the rosette ring channel. Attachment: Octave Mandolin 15.jpg Ready to install sound hole binding and rosette purfling. Attachment: Octave Mandolin 16.jpg Completed rosette Attachment: Octave Mandolin 17.jpg Ready to install braces Attachment: Octave Mandolin 19.jpg Vacuum clamping the top braces Attachment: Octave Mandolin 20.jpg

Author:	J De Rocher [ Tue Feb 15, 2022 3:35 pm ]
Post subject:	Re: New octave mandolin
Carved top braces. I went with tapered lower x-brace arms. Attachment: Octave Mandolin 21.jpg Attachment: Octave Mandolin 22.jpg Top fitted to the sides Attachment: Octave Mandolin 23.jpg Back fitted to the sides Attachment: Octave Mandolin 24.jpg Closing up the box Attachment: Octave Mandolin 25.jpg Routing binding/purfling channels Attachment: Octave Mandolin 26.jpg I bend the bindings and side purflings on a hot pipe with the side purflings sandwiched tightly between the bindings. That keeps them from twisting while being bent. Attachment: Octave Mandolin 27.jpg Ready to install binding and purfling Attachment: Octave Mandolin 28.jpg

Author:	J De Rocher [ Tue Feb 15, 2022 3:49 pm ]
Post subject:	Re: New octave mandolin
Shop dog supervising work Attachment: Octave Mandolin 29.jpg Rough cut curly maple neck blank Attachment: Octave Mandolin 30.jpg Logo inlay cut out of pearl Attachment: Octave Mandolin 31.jpg Inlay recess done Attachment: Octave Mandolin 32.jpg Head plate glued to headstock Attachment: Octave Mandolin 33.jpg I rough cut the headstock shape on the bandsaw. The blocks double stick taped underneath raise the neck to give clearance for the neck shaft above the bandsaw table and keep the headstock level. Attachment: Octave Mandolin 34.jpg Final heastock shape done on the Robo-Sander using a template. Attachment: Octave Mandolin 35.jpg Gluing the binding onto the fretboard. I use this setup on my router table. The fretboard and binding are sandwiched between two pieces of wood with clamping pressure provided by the featherboards pushing everything against the fence. I wick thin CA into the joint between the binding and the fretboard. I made this setup years ago out of three pieces of scrap plywood and it works so I've never fancied it up. Attachment: Octave Mandolin 36.jpg

Author:	J De Rocher [ Tue Feb 15, 2022 4:04 pm ]
Post subject:	Re: New octave mandolin
Fretboard glued to neck Attachment: Octave Mandolin 37.jpg The heels on my necks have to flat faces above the curve. I cut them with a pull saw. Attachment: Octave Mandolin 38.jpg I use Dragon rasps to do most of the shaping of the heel curve. Attachment: Octave Mandolin 39.jpg I remove most of the wood from the neck shaft using a spokeshave. I've settled on this after using various rasps and chisels for that task. This works best for me. Attachment: Octave Mandolin 41.jpg After most of the material has been removed with the spokeshave, I switch to Dragon rasps for the rest of the shaping. Attachment: Octave Mandolin 42.jpg On to the finish application. I'm using Endurovar and I brush it on. To make the application faster and easier, I came up with a handle for the body that works as a rotisserie for easy access to all sides of the body. It's made from two pieces of scrap wood and an 8" lag bolt that I had sitting around. It gets bolted to the body using the same hardware for attaching the neck. The wood block furthest from the body gets clamped in the vice and then the body can be rotated to whatever position is convenient. The eye at the end of the lag bolt comes in handy for hanging the body while the finish cures. Attachment: Octave Mandolin 43.jpg Attachment: Octave Mandolin 44.jpg Attachment: Octave Mandolin 45.jpg

Author:	J De Rocher [ Tue Feb 15, 2022 4:15 pm ]
Post subject:	Re: New octave mandolin
This is what the finish looks like after the brushing is done. Attachment: Octave Mandolin 46.jpg Attachment: Octave Mandolin 47.jpg And after level sanding and buffing Attachment: Octave Mandolin 48.jpg Attachment: Octave Mandolin 49.jpg Final neck attachment to the body Attachment: Octave Mandolin 50.jpg Installing frets Attachment: Octave Mandolin 51.jpg This is the device I built about a month ago for removing the tangs from under the fret ends. It uses a cutting wheel in my Dremel and it's a huge improvement over the fret nipper I've been using all along. It never damages a fret end, it can be adjusted to give perfect removal of the tang, and it's way faster to do all the frets with this than with the nipper. Attachment: Octave Mandolin 52.jpg Jig for slotting the bridge. This is another example of a jig I made from scrap wood as a prototype and it worked so well that I never saw any reason to make it fancier. Attachment: Octave Mandolin 53.jpg

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Author:	J De Rocher [ Tue Feb 15, 2022 4:29 pm ]
Post subject:	Re: New octave mandolin
Routing the saddle slot Attachment: Octave Mandolin 54.jpg You may notice that this slot looks unusually wide and it's not angled. That's because the big differences in compensation points between string courses and having double string courses makes for a zig zag shape that's hard to fit onto a narrow angled saddle like we typically use for a guitar. Attachment: Octave Mandolin 55.jpg Finished bridge. I use two strings per bridge pin hole to maximize the gluing surface under the bridge. Attachment: Octave Mandolin 56.jpg Ready to scribe the bridge outline in the finish Attachment: Octave Mandolin 57.jpg Ready to remove the finish from the bridge footprint Attachment: Octave Mandolin 58.jpg Ready to glue the bridge on Attachment: Octave Mandolin 59.jpg Locating the compensation points on the saddle Attachment: Octave Mandolin 60.jpg Strings on for the first time Attachment: Octave Mandolin 61.jpg

Author:	J De Rocher [ Tue Feb 15, 2022 4:32 pm ]
Post subject:	Re: New octave mandolin
Attachment: Octave Mandolin 02.jpg Attachment: Octave Mandolin 03.jpg Attachment: Octave Mandolin 04.jpg Attachment: Octave Mandolin 05.jpg Attachment: Octave Mandolin 06.jpg Attachment: Octave Mandolin 07.jpg Attachment: Octave Mandolin 08.jpg Attachment: Octave Mandolin 09.jpg

Author:	J De Rocher [ Tue Feb 15, 2022 4:34 pm ]
Post subject:	Re: New octave mandolin
Attachment: Octave Mandolin 10.jpg Attachment: Octave Mandolin 11.jpg Attachment: Octave Mandolin 12.jpg

Author:	bcombs510 [ Tue Feb 15, 2022 7:07 pm ]
Post subject:	Re: New octave mandolin
That's a really beautiful instrument, Jay. Some questions: - How do you like the vacuum jig? Is that the LuthierTool one? - Is that a 13th fret attach? Is that common for these instruments? - With the tension being 170 did you have to make any special considerations with the bracing / bridge? Would love to hear it if you get a sample.

Author:	J De Rocher [ Tue Feb 15, 2022 7:43 pm ]
Post subject:	Re: New octave mandolin
Thanks, Brad. I built the vacuum frame based on the info on the Joe Woodworker website. https://www.joewoodworker.com/veneering/vacuum-frame-press.htm I like it a lot. It's straight forward to use and works fine. The version I built takes advantage of the fact that the top on my island bench is an old benchtop from a biology lab. The surface is smooth and I use it as the base for the vacuum frame when gluing braces. The frame seals well enough against that benchtop. My shop is small so I didn't want to have to have a dedicated vacuum clamping table taking up room. With this setup, I can store the frame out of the way against the wall on top of a cabinet when not in use. I use a small GAST electric vacuum pump I got off ebay to draw a vacuum. A minor disadvantage of my setup is that the seal against the benchtop isn't quite good enough to be able to turn the pump off once it has reached max vacuum. Almost, but not quite. I have to leave the pump on, but it's pretty quiet. I leave the braces under vacuum for one hour. The guy I learned to build guitars from had a dedicated vacuum clamping table with a hinged vacuum frame in his shop and using it was what sold me on the idea. His table had a good enough seal to be able to turn the pump off after reaching max vacuum. I don't know if you can tell from the photo, but the top is sitting on a radius dish that fits under the frame. There's no standard for which fret the neck joint happens at. For this OM, with the 21" scale, the body length/shape, and where I wanted the bridge to be, the 13th fret join was just how it worked out. 170 lbs string tension is in the range of string tensions for six string acoustic guitars so the bracing is based on what I've used for my parlor guitars. I'm working toward doing a sound sample. The scale length on this one is a bit longer than I've used before and it's enough of a difference that I'm having to adjust my technique a bit to play cleanly. Once I get there, I'll record something.

Author:	sjfoss [ Thu Dec 01, 2022 9:34 am ]
Post subject:	Re: New octave mandolin
Jay, A lovely build. I wiill probably "borrow" the rotisserie idea. I have a bicycle mechanic's stand that will hold a guitar for finishing just fine. The rotisserie will make it easier. Thanks! Could you elaborate on your neck joint? How did you match the curve of the neck heal to the body? Thanks, Steve

Author:	J De Rocher [ Fri Dec 02, 2022 11:55 pm ]
Post subject:	Re: New octave mandolin
sjfoss wrote: J Could you elaborate on your neck joint? How did you match the curve of the neck heal to the body? Steve There are two parts to it. One is cutting a radius in the end of the neck and the other is putting a radius on the heel cap. For the radius on the end of the neck, I use a jig to cut the radius on my bandsaw. In addition to cutting the radius, it also allows me to cut the correct angles to align the neck along the centerline and to give the correct neck angle for the desired clearance over the top at the saddle location. Here are some photos that show the basic steps. Here's a neck blank clamped to the jig. The jig is clamped to the fence and pivots around a vertical bolt. Sweeping the jig with the neck through the saw blade produces the radius cut. I originally made this jig from some random scrap pieces that were lying around as a prototype. It works so I've never made a prettied up version of it. Attachment: Making radiused neck joint 1.jpg The pivot bolt (yellow arrow) is centered on a line that runs perpendicular to the leading edge of the bandsaw blade. The neck blank is in position here for a first cut. I start with enough extra length on the neck end to be able to do up to four test cuts to get the neck angles correct. I've done this enough times now that it takes two or three cuts to get a final cut that puts the neck alignment right on the mark. The second line from the end of the neck marks the neck/body joint position and the final radius cut will go there. Attachment: Making radiused neck joint 2.jpg This next photo shows after the first cut. The distance from the center of the pivot bolt to the blade is the radius of the cut. The jig is clamped to the fence so the radius of the cut is adjustable. I cut the radius to be slightly smaller than the radius of the end of the body so that the neck will rest on the outside edges and not be "high centered" in the middle. After this first cut, I test the fit to the body for skew on the centerline and clearance above the top at the saddle. Any correction to skew is made by adjusting the side-to-side angle of the neck on the jig. The neck angle for clearance at the saddle is adjusted by moving a shim under the neck. I clamp the neck back into the jig and make a thin second cut and check the fit again. A third cut usually gets both angles right on the mark. Now is where the first line from the end of the neck comes in. I use a bolt-on neck with a mortise and tenon. I'm sure this neck joint could be done as a butt joint, but I like the idea of having the tenon in a mortise more. So, the problem was how to cut a radius in the neck end and have a tenon. I solved this by using a floating tenon that goes in after cutting the radius. After getting the neck alignment settings on the jig dialed in for both neck angles, I cut the neck end off square on that first line so I can rout a mortise for a tenon. Attachment: Making radiused neck joint 3.jpg Here's the neck after cutting the end square and routing the mortise for the tenon and routing the truss rod channel. Attachment: Making radiused neck joint 4.jpg The neck then goes back on the jig for the final radius cut at the neck/body joint position. The tenon is a three-layer laminate with the grain alternating by 90 degrees in each layer. Attachment: Making radiused neck joint 5.jpg This is what the neck end looks like after the final radius cut and the tenon glued in. One unexpected benefit of using this jig is that I can get the final radius exactly on target for neck skew along the centerline and neck angle for clearance at the saddle. I don't have to spend time flossing the neck joint to get the fit correct. Attachment: Making radiused neck joint 6.jpg Here is what the fit to the body looks like. Attachment: Making radiused neck joint 8.jpg For the heel cap, I draw the radius of the end of the body on the piece I'm going to use for the heel cap and cut it as accurately as I can on the bandsaw. I then sand out band saw imperfections with adhesive backed sandpaper on a dowel to get the fit pretty close. I fine tune the fit using the same approach we use to fit the bridge to the top. I bolt the neck onto the body with a piece of sandpaper in between the neck and the body with the sandpaper sticking up where the heel cap goes. I place the wood piece on the bottom end of the heel and slide it side to side against the sandpaper on the body to get a tight fit. Attachment: Making radiused neck joint 7.jpg I hope this all makes sense. If something's not clear, let me know.

Author:	sjfoss [ Sun Dec 04, 2022 11:03 am ]
Post subject:	Re: New octave mandolin
Jay, THanks! This is a very clever system. And very adapable, too. My interest was sparked both by your build as well as a video Isaw of Marshall Brune doing a classical build with Rob Scallon [url]https://www.youtube.com/watch?v=qmDAIlEGO_Q/url]. Brune uses a splined joint which he claims is superior to the Spanish heal. He makes it using a too-large-for-my-shop sanding machine that very quickly and accurately mates up the neck with the body. I saw your build and had to know. Your system appears like it could also do a 'negative' angle for a classical guitar. I'll try it out on some 'ukes that are next on grandpa's list of things to build. Thanks for posting, Steve

Author:	J De Rocher [ Sun Dec 04, 2022 4:52 pm ]
Post subject:	Re: New octave mandolin
That sanding machine in the video for making the neck/body joint is pretty slick. You'd definitely need a big shop for that though. What is a negative angle for a classical guitar? Is that the forward tilt of the neck relative to the body?

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Author:	Durero [ Mon Dec 05, 2022 8:24 pm ]
Post subject:	Re: New octave mandolin
J De Rocher wrote: What is a negative angle for a classical guitar? Is that the forward tilt of the neck relative to the body? I believe so.

Author:	sjfoss [ Tue Dec 06, 2022 9:28 am ]
Post subject:	Re: New octave mandolin
Jay, yes, the 'negative angel' is the forward tilt of the neck. The nylon strings are floppier and need more room at the 12 fret. THanks again, Steve

Author:	Bob_H [ Wed Sep 06, 2023 3:30 am ]
Post subject:	Re: New octave mandolin
A very informative post and a lovely looking instrument. Can you advise what diameter strings you are using for your 21 inch scale length?

Author:	Kbore [ Wed Sep 06, 2023 2:42 pm ]
Post subject:	Re: New octave mandolin
J De Rocher wrote: Gluing the binding onto the fretboard. I use this setup on my router table. The fretboard and binding are sandwiched between two pieces of wood with clamping pressure provided by the featherboards pushing everything against the fence. I wick thin CA into the joint between the binding and the fretboard. I made this setup years ago out of three pieces of scrap plywood and it works so I've never fancied it up. Attachment: Octave Mandolin 36.jpg Love your sequenced build pictures, very nice method of work. Im going to adapt my purfling-to-binding jig to my rout3r table- thanks for sharing!

Author:	J De Rocher [ Fri Sep 08, 2023 7:54 pm ]
Post subject:	Re: New octave mandolin
Bob_H wrote: A very informative post and a lovely looking instrument. Can you advise what diameter strings you are using for your 21 inch scale length? I'm using the Heavy octave mandolin string set (0.013, 0.024, 0.038, 0.054) from emando.com: http://www.emando.com/shop/strings_zouk.htm Emando recommends the Medium set for scale lengths of 21"-22" and the Heavy set for 19"-20" scales, but I find that the Heavy set works fine for a 21" scale. My reasoning for using the Heavy set is that I want higher tension on the G-course strings to avoid string-to-string clatter within that course while keeping the string spacing within the course reasonably narrow. The total string tension works out to be around 190 lbs depending on which string tension calculator you use, which isn't too much more than on a 6-string steel string guitar that's strung with a "medium" string set. The emando Medium string would give e total tension around 170 lbs for the 21" scale on an octave mandolin.

Author:	J De Rocher [ Sun Jun 30, 2024 8:18 pm ]
Post subject:	Re: New octave mandolin
I finally got around to recording a demo of this octave mandolin. This is my friend Dean Snider playing an instrumental piece he wrote for his daughter's wedding called Madison's Procession. For those who may be interested, this was recorded using two Shure PGA81 mics in ORTF configuration into an iRig Duo Pro and then into an iphone 13Pro. No audio processing was used. https://youtu.be/Ihd9DnvxjSs

Author:	Kbore [ Sat Jul 06, 2024 3:09 pm ]
Post subject:	Re: New octave mandolin
J De Rocher wrote: I finally got around to recording a demo of this octave mandolin. This is my friend Dean Snider playing an instrumental piece he wrote for his daughter's wedding called Madison's Procession. For those who may be interested, this was recorded using two Shure PGA81 mics in ORTF configuration into an iRig Duo Pro and then into an iphone 13Pro. No audio processing was used. https://youtu.be/Ihd9DnvxjSs Beautiful composition, and stunning instrument.....

Author:	Ken Nagy [ Thu Jul 11, 2024 8:31 am ]
Post subject:	Re: New octave mandolin
I saw the finished instrument, and heard this, and another piece on it. How did I never see this post on how it was done? Lots of great ideas there Jay.