My mandocello/OM conversion project

[James1223]

This is my first big project ever. I've repaired some small things on my own instruments before but this is a bit different.

This project started six years ago when I bought a Harmony 950 solid birch body on eBay. It had a few cracks in the top and back and pretty bad one on the side that went horizontally through the neck block. It also had a loose brace on the bass side. The back was coming off at the heel block so I removed it to allow myself better access to the braces and make it easier to fix the cracks.

I've repaired the cracks and sanded smooth the back and the linings so I'll have a solid joint when I reattach the back.

Im waiting on my neck and fretboard to arrive so I can get them put together with the trussrod I bought from Stewmac. I'm still working on a peg head design. This is complicated because the finished instrument will have five double courses tuned CDGAE. The scale is 25.75" which should be long enough to give the low C some oomph.

My next decision is whether to reposition the braces more like a mandolin or leave them as they are. One brace, on the bass side, I already removed because it was loose. The braces were originally positioned parallel to each other running from the neck block to the heel block. Any suggestions on whether I should just leave them like they were or should I try a different placement?

I'll get some pictures up as soon as I can.

Thanks,
James

[James1223]

[James1223]

Okay, I've glued all the cracks and contoured and reglued the brace. Now I have to wait for my neck and neck block to arrive. I don't know yet if I can use the existing neck block or if I'll have to replace it. I've also sanded the top and back in preparation for sealer and finishing. I'm going to use flat black lacquer and matte lacquer clear coat. Hopefully the flat black will hide any flaws I leave behind.

[dschonbrun]

Really nice work.

Looking forward to seeing the true grain after the sanding. Please share pics before you stain.

[colorado_al]

Top has a really nice grain to it. Makes me wonder why they always did the fake patterning on them?

[James1223]

Really nice work.

Looking forward to seeing the true grain after the sanding. Please share pics before you stain.

Thanks for the compliment. I hadn't really gave any thought to sanding all of the old finish off. I always had it in my head that I'd spray this in black lacquer. Now I'm not so sure thanks to you. I've already got the back finished but I think I'm going to do to the top in a transparent color so the grain shows through. I think I'll stick with the all black theme but I'll make the translucent.

[James1223]

Okay, I had to finish sanding. Rick Penta of Pentaguitar Works is making a neck and neck block for me. It should be here in a week or two. And I've got a fretboard and frets coming from Allen Guitars & Luthier Supplies. The scale is 25.75 inches. I'm still undecided about whether to radius the fretboard or leave it flat. Anyone have any thoughts on that?

[James1223]

Here are a couple of pics.

[Bernie Daniel]

Okay, I had to finish sanding. Rick Penta of Pentaguitar Works is making a neck and neck block for me. It should be here in a week or two. And I've got a fretboard and frets coming from Allen Guitars & Luthier Supplies. The scale is 25.75 inches. I'm still undecided about whether to radius the fretboard or leave it flat. Anyone have any thoughts on that?

I've converted four arch top and one flat top guitar to 4-course mandocellos and one arch to a 5-course (like you are doing). For all of the 4-course projects i narrowed the nut to 1.5" and tapered the fret board and neck to match. For the 5-course I left the guitar neck width alone -- like you are apparently doing? I would recommend a gentle 16" radius over a flat board for playability. On one mandocello I sanded in an 8' radius and that is kind of too radical for such a wide neck. That said I did adapt to playing it over time and it did play with very little buzzing which is often so annoying on mandocellos. Good luck!

Here is a pic of one of my conversions this started life as a 1940 C-66 Vega arch top guitar.

[James1223]

That's a beautiful m'cello. The neck I have coming has a nut width of 1 3/4". I had planned on leaving that alone. I need to sit down and figure out my string spacing. That will give me a better idea of what the nutbwidth should be. I figured a radiused fretboard would be easier to play although I don't imagine I'll be doing many chords in the first position. My scale length is 25.75" and my fingers aren't all that long. I hoping to have the neck here next week sometime. Then I can start fitting the neck block and getting this body back together.

What did you use for tuners, bridge and tailpiece on your 5 course?

[Kerry Krishna]

James, I know I am not on here anymore, so you don't know me or my history.
I don't mean to be too forward in my suggestion here either, but in my opinion, that 1 3/4 neck is going to be too wide for this project. I have done at least 4 of these conversions, and that neck width for 5 course ( this axe would be called a cittern over in UK) is too wide.
1 5/8 inches should be a good measurement, though one of the conversions I did was only 1.5 at the nut like Bernie's measurement. It is totally playable, but a bit crowded for 5 courses.,

This is such a big project, and you have done a great job on it so far. Staying with the 1 3/4 neck will, I am pretty sure, make for vera difficult playing experience.
Taking a bit of wood off of each side of the neck is fairly straightforward if it is too late change your Luthier's neck dimensions, or if it has already been mailed to you. Several folks here can talk you through taking the wood off if you choose to do what I am suggesting.

[James1223]

I don't know how far along the luthier is with the neck. He started on it Thursday so I'd guess the rough shape is done at least. I have been doing some research on what a reasonable nut width should be and like you said 1 5/8 comes up quite often. I don't have any problems taking a little time to trim down the neck after I receive it. Thanks for the insight. Any advice from those who have done this before is welcome. That's why I love this place. It's full of people with a depth of knowledge.

[Bernie Daniel]

I don't know how far along the luthier is with the neck. He started on it Thursday so I'd guess the rough shape is done at least. I have been doing some research on what a reasonable nut width should be and like you said 1 5/8 comes up quite often. I don't have any problems taking a little time to trim down the neck after I receive it. Thanks for the insight. Any advice from those who have done this before is welcome. That's why I love this place. It's full of people with a depth of knowledge.

I would tend to agree with Kerry that even with 5 courses you might what to have a nut width of something like 1 9/16" (1.562") rather than the 1.625" that you are planning. Small differences in neck/nut width make big differences in playability.

For the 5-course I left the guitar neck/nutwith alone (1 9/16") and that string/course spacing was then about the same as the spacing on a standard 4-course mandocello with a 1 1/2" nut. I recall taking the completed instrument (I called it a cittern for lack of a better name) over to Will Kimble's shop and he liked how it played and sounded so I felt I was probably on "safe ground" with it. I sold it to a guy in Idaho and he seems to like it. Pic of the five course included.

One thing. There is a fret marker at the 9th fret (guitar) and that was moved the the 10th fret a few days after this picture was take. Also, this conversion was done on a new The Loar guitar and I wanted to retain that logo in the head stock and still cover over the guitar holes so that was fun!

On your last questions. I bought the 5-course tuners from All Parts as I recall, the bridge is an ebony arch top guitar bridge with a new saddle that I carved and compensated from an ebony block, and the tail piece is the original guitar trapeze that I "re-engineered" to handle the 5 courses. You might be able to purchase a 5-course TP perhaps if you did a search?

[James1223]

Real nice Bernie. Last night if found at Allen Guitar and Luthier supply a ten string tailpiece called the MR10. That's what I'll be getting for mine. I saw those tuners at All Parts that you mentioned but was hesitant because of the unknown quality. Did they feel okay to you? If so they seem like just the thing for this project.

Im going to take the advice given to me here and slim the neck down to 1 9/16. I don't have large hands and playability is always a concern.

Here's a link to the tailpiece.
http://www.allenguitar.com/tpcs_mr-10.htm

[Bernie Daniel]

Real nice Bernie. Last night if found at Allen Guitar and Luthier supply a ten string tailpiece called the MR10. That's what I'll be getting for mine. I saw those tuners at All Parts that you mentioned but was hesitant because of the unknown quality. Did they feel okay to you? If so they seem like just the thing for this project.

Im going to take the advice given to me here and slim the neck down to 1 9/16. I don't have large hands and playability is always a concern.

Here's a link to the tailpiece.
http://www.allenguitar.com/tpcs_mr-10.htm

Thanks I'll take a look at that tail piece. On the tuners yes they will do fine -- they are not Grover or Schaller etc., quality by any means. I expect they are made in China and are kind of equivalent to Ping tuners in quality. But they work fine and you are starting with an old Harmony so I think they will be a very good match. Later if you build a second 5 course starting from a higher end arch top you could consider using 10 individual mini-tuners -- that is a more expensive approach but gives you a lot of flexibility for the placement. Attached is pic of some of the mandocellos that I made over the 3 years I was doing conversions.

[David Houchens]

Bernie, What string gauge did you end up liking the most at those scale lengths? Thanks.

[David Houchens]

I have a late 30's (I'm Told) archtop. Maybe a Harmony, but the serial # has a SR in it rather than an H. I think Harmony did at one time build for Sears Roebuck. I'm a bit torn because it's a pretty nice 6 string as well. But have been wanting to try a mandocello.

[James1223]

That's much nicer than what I started with, David. I'd be hesitant to but I've seen so many nice donor guitars on eBay that you could always get another one and keep what you've got there original.

[Bernie Daniel]

That's much nicer than what I started with, David. I'd be hesitant to but I've seen so many nice donor guitars on eBay that you could always get another one and keep what you've got there original.

The question of which guitar to start with on a conversion is always one that requires consideration. First I think it is true that the better the donor guitar perhaps the better the resulting mandocello. Some have suggest that it is wrong to destroy a good arch top guitar to make a mandocello. I think that view is wrong. A mandocello is as worthy and useful as a guitar and the loss of the guitar is balanced off by the gain of a mandocello! People should have the instrument they want.

One thing to consider how sure are you of your skills? If you've done luthier or repair work before and know what you are in for then get the best arch top you can afford and do your conversion. If you are not certain on might start with a cheaper guitar for the first conversion and then go for a better instrument on the next try.

I did several arch top conversion before I converted a 1942 Gibson L-50 to an K-5 style mandocello - so now I have my ultimate Gibson mandocello -- even though it was not made in 1924 and signed by LL

[James1223]

The neck and neck block came in. �� I've got the neck block glued in and the neck is pretty well fit. One question though, I've laid a straight edge along the neck and measured the height above the top where the bridge will sit. I've got 0.75". Does that sound about right? You can see that in the first photo.

I still have to glue the fingerboard extension to the neck and tomorrow I'm going to lay out the headstock design and the tuner holes.

[James1223]

Got the back glued up tight.

[fox]

Hi James, you are doing a great job.
I did a lot of work on a similar guitar but it only has four strings!
I don't know if you plan on using any electronics but I found that... although the flat sawn birch wood, looks fantastic, it does not perform very well as a soundboard.
I reshaped the tone bars and even reduced the overall thickness of the top and back in an attempt to get a better sound out of the wood. I had the back off three times!
Birch just does not perform like spruce or cedar and it sounds pretty dead in comparison, of course with 10 strings and 180lb of tension, yours will be very different however I would suggest looking at some form of pickup.

[Bernie Daniel]

Hi James, you are doing a great job.
I did a lot of work on a similar guitar but it only has four strings!
I don't know if you plan on using any electronics but I found that... although the flat sawn birch wood, looks fantastic, it does not perform very well as a soundboard.
I reshaped the tone bars and even reduced the overall thickness of the top and back in an attempt to get a better sound out of the wood. I had the back off three times!
Birch just does not perform like spruce or cedar and it sounds pretty dead in comparison, of course with 10 strings and 180lb of tension, yours will be very different however I would suggest looking at some form of pickup.

I've often wondered how those birch tops would perform as tone wood for a top. I expect they used birch because it was strong and because they actually wanted that sound from those old arch tops? Birch works well as a back board wood though and Gibson used it in most of the lower A-model mandolins and even in the, H-1s and F-2s and many of the K-1 and K-2 mandocellos.

The total string tension on that 10 course will be much closer to 300 pounds than 180!

Your project is looking great James. You asked earlier about string gauges. On 4 course mandocellos I always use D'Addario J78's. On the Cittern I do not recall exactly the string custom gauge set I used but I know that the C course was 0.070" and then I used the string gauge and pitch on the mandocello and guitar to estimate the gauges I wanted for the other courses. My goal was to keep the tension on each course about the same across the bridge. I could probably look up what I ordered from Just Strings although it was a couple of years ago at least.

[James1223]

Just a couple of pics today. A dry fit of the neck and fingerboard extension.

[David Houchens]

Steaming out the neck on mine today. Gonna make a new one with 27" scale. I guess these have a string height similar to guitar due to string gauges.