Jump to content

Voting for May 2020's Guitar Of The Month is open - VOTE HERE!

mattharris75

First Acoustic. Not exactly a guitar...

Recommended Posts

After finishing the 2/3 scale guitar build for my daughters I took a little time off to work on other projects. Household carpentry, building a combat robot, etc. But for the past few years I've been wanting to build an acoustic instrument, as that's mostly what I play these days. I play primarily mandolin, and I have several of those as well as a guitar bodied octave mandolin. So I thought, why not fill in the gap and build a mandola!

I love the look of guitar bodied octave mandolins, which are becoming more popular. They're generally based on smaller bodied archtop jazz guitars. My octave has a 14" lower bout. And as they look so cool, and as this would be an incredibly rare bird, I thought I'd make the mandola with a sort of pseudo guitar body as well. So, it's 3/4 a shrunken down archtop guitar body with a mandolin style 'open hook' scroll ala the great luthier John Monteleone. 

Here's a rendering-

58d94268e15c6_MonteleoneStyleGuitarBodiedMandola-Renderingcopy-Small.thumb.jpg.1bc9f8e013974169674ff3df07cf18e7.jpg

 

Some specs on this -

Scale length: 17"

Body width: Just under 11.5"

Body Rib depth: 1.75"

Woods -

Top: Old Growth Redwood

Back & Sides (ribs): Lightly Curly  Local Black Cherry

Fretboard: Bocote

Neck: Laminate of Cherry/Walnut/Flamed Maple/Walnut/Cherry

Misc Appointments: Macassar Ebony

Here are a few pics of the various woods-

The top, freshly joined: 20170326_225218.thumb.jpg.f80f9a85e59405868e607419363d36b3.jpg

 

The neck blank, all glued up and cleaned up:

20170314_194820.thumb.jpg.a02704ed3328680e503a155ce03b6551.jpg

 

The rough cut back of local cherry. You can see a little wide curl in it:

20170321_224309.thumb.jpg.109589e23c85a9ee5e381479cb956662.jpg

 

Beyond that I've cut and thicknessed the sides down to 2mm, cut the headstock angle in the neck blank, and am working on the form to be used for side bending and top/back attachment.

Progress will be slow because, well, that's just who I am... :) And I make no apologies! :)

 

  • Like 2

Share this post


Link to post
Share on other sites

Woohoo! I have been waiting for this one to come up. I too will be watching closely. How thick is your top and back, Matt?

Share this post


Link to post
Share on other sites

Thanks guys.

Scott, the back plate is 24 mm and the top is 21 mm. Haven't settled on final thicknesses for them yet. My plan is to carve the back a bit deeper than the front, but I'm not settled on all that yet. There's as much voo doo with mandolin building as there is with guitars, so I'm just trying to absorb as much info as possible before I make those cuts. And also, this instrument is a bit of an odd ball, so I'm having to piece together ideas from various resources...

Share this post


Link to post
Share on other sites
3 hours ago, mattharris75 said:

And also, this instrument is a bit of an odd ball, so I'm having to piece together ideas from various resources...

I've had the tiniest germ of an idea along those lined fermenting in the back of my mind since I did that F-style kit. I'm not sure if it is going to germinate or not, but I have a feeling this build is going to shine a little light on it. I shall be watching avidly.

SR

Share this post


Link to post
Share on other sites

I'm still waiting for my laser cut templates to arrive so that I can finish the form and then bend the sides. So, most of my progress has been grunt work.

I glued up a laminate to cut the neck block and tail block out of. Mahogany, walnut, and mahogany. I turned the pieces in different grain directions to add a bit of stability. That seems to be popular among mandolin builders who laminate their blocks.

I'm not using a truss rod on this build, I'm just installing a graphite stiffening rod and counting on that and the fact that I'm using a laminated neck to give it quite a bit of strength and stability. I don't expect to need to add relief to the neck. It's still not all that uncommon on these shorter scale instruments to not use a truss rod. I have a 99 year old Gibson with no truss and a nice straight neck. So, I went ahead and cut the channel for the graphite rod. 

Here's a pic. I wish I could say that the 1mm offset to the treble side was done for some fancy luthier related reason, but the reality is that the fence slipped slightly when I was adjusting the cut depth after the test cut. Oops, but no harm no foul. Other than the fact that I'll always know it's there there won't be any long term impact.

20170402_223935.thumb.jpg.e1fbd77e6708c9f1528a0ab25c8f2e48.jpg

 

Other things visible in the picture: At the top left you can see my laminated block for the neck and tail blocks. And at the very top, a test bend of the cherry sides.

@ScottR, I've decided to go with 3/4" plate thicknesses, and got those planed down as well. A typical mandolin plate is about 5/8", and this instrument is a bit bigger. I also talked with a pro to get his ideas on working with redwood, and he gave me some good numbers to get me started on the top carving. In his experience the difference in spruce and redwood is fairly dramatic, as it turns out. 

Share this post


Link to post
Share on other sites
20 minutes ago, mattharris75 said:

I've decided to go with 3/4" plate thicknesses, and got those planed down as well. A typical mandolin plate is about 5/8", and this instrument is a bit bigger. I also talked with a pro to get his ideas on working with redwood, and he gave me some good numbers to get me started on the top carving. In his experience the difference in spruce and redwood is fairly dramatic, as it turns out. 

With redwood I would expect you are going to need a thicker top compared to spruce.

SR

Share this post


Link to post
Share on other sites
15 minutes ago, ScottR said:

With redwood I would expect you are going to need a thicker top compared to spruce.

SR

Yes, which is what I expected as well. I just didn't expect as great a difference as he said. The guy I talked to uses CNC to rough out his plates, but does all the final graduating by hand. After much trial and error his starting plate thickness is between 70% & 100% thicker, depending on the area of the top, than an equivalent sitka spruce top. And he's made some phenomenal sounding redwood topped mandolins, so I reckon I'll be giving his dimensions a shot.

  • Like 1

Share this post


Link to post
Share on other sites

I reckon it's time to post an obligatory 'all of the clamps' shot. In this case, a collage:

Clamps.thumb.jpg.e9899f83a8996f0a2fe0ae3bd338289e.jpg

 

'All the Clamps - Mandola Neck Edition'. On the bottom left, gluing the wings for the headstock. On the bottom right, gluing the headplate.

I've also epoxied in the graphite stiffening rod, rough cut the back profile of the neck, and cut the neck angle at the heel, 3 degrees for this one. 

I put in orders to StewMac & LMI last night to get the bulk of the rest of my building materials and hardware. Once that all arrives I'll be able to laminate the binding (never worked with multi-layer plastic binding before, only wood) and cut out the fretboard profile and bind it and fret it before gluing it to the neck. That's not my normal order of operations, I have typically glued the raw fretboard to the top of the neck and profiled the sides of the neck and fretboard together, then cut the binding channels and do the binding. But this order seems to be the common method for  mandolin builders. And, given that the fretboard will overhang the end of the neck I won't be able to use the neck profile to cut the entire length of the binding channel, so I suppose this order makes sense in that regard.

Speaking of the fretboard, I've made my first 'significant' design change from the rendering I posted. After seeing the bocote fretboard next to the macassar ebony headplate I felt like they competed with one another too much rather than complementing one another. Given that the mandola will have a generally reddish tone, with the redwood top and cherry back and sides, and given that I just happened to have the right sized bloodwood fretboard laying around, well, there you go:

20170405_164909.thumb.jpg.2ec5600ea631ca3bb1c7b74e1c16c2ff.jpg

 

Yeah, I think that'll work!

  • Like 1

Share this post


Link to post
Share on other sites

I'll be interested to see how you tackle the multi-layer plastic binding. It presented some first time challenges for me.

SR

Share this post


Link to post
Share on other sites

I'll be interested too. :)

A couple of things that make my task slightly easier than yours: 

1. I'm only doing two layers, .04 cream on the inside and .02 black on the out.

2. My scroll area is an open scroll and slightly larger than a regular mandolin too, so my curves won't have to be quite as tight and there's a bit more space to work.

I've still got a while before I get to the body, I don't expect the fretboard to produce too many challenges...

  • Like 1

Share this post


Link to post
Share on other sites

I spent a couple of hours last night getting the back of the headstock and neck to the correct thicknesses. Between the safety planer, oscillating spindle sander, belt sander, sanding block, and card scraper I finally have it close. This always seems to be fussier and more time consuming than I expect...

Here's a pic of where it stands:

20170406_234627.thumb.jpg.aae11ae6bbfbab726e75de35d5831d8f.jpg

 

A couple of things to note:

While sanding I uncovered a small pitch pocket in the cherry. You can see it a couple of inches from the neck heel on the right side of the neck. Not too surprising in cherry I suppose, and I don't really mind character as long as things are stable. I'm going to assume right now that I'll end up carving most of it out, and anything left I'll fill with epoxy.  

You can also see a mark that goes across the grain near the top of the headstock area. That's where I got a little wild with the safety planer. I have a tiny bit of margin left , so I'm going to continue with sanding and scraping until I hopefully get that last little bit knocked out. 

Also of note, if you look at the tail end of the headstock area you can see two little round dots in the corners. Those dots are actually bamboo skewers that I used as alignment pins when gluing the headstock overlay. They work really well, I've used them on my last several builds.

Tonight I plan to finish cleaning up the back of the neck, get the backstrap thicknessed down to about 1.5 mm, bend the end of it, and get it glued on. I'll start working on the fretboard if I have time.

  • Like 1

Share this post


Link to post
Share on other sites

Can't wait to see the detail photos of the "open scroll hook" upper cutaway.  Cutaways are so sexy on guitars, so I'm glad to see you do this in an "acanthus leavage" extent.  Maybe even inspire some wilder cutaways on someones guitar build (maybe one of my future ones).

Bent laminating seems tough on such a tight radius, so I assume you might endup cutting that curl from solid.  But then again, about six layers of veneer side grain would do it too, although you are more likely to make the whole horn from solid right?  

Looking forward to seeing progress on this.  

Maybe, or maybe not applicable for your project, but when I needed a tight radius in my boat armrests, I cut the teeth off of a 7-1/4" blade, then mounted it on my T-saw, then while spinning took a grinder to grind the toothless teeth into 4 degree "pie" shaped teeth in order to cut headless kerfs in the kerf bend.  Took about a half hour to grind the relief clearances behind each tooth, but it cut like a dream.  Would probably work great as a fret saw too.  

 

Bentmahog-lorez.JPG

V-blade-cross.JPG

Share this post


Link to post
Share on other sites
1 hour ago, ScottR said:

Dang, you're moving right along. You must have missed building.:)

SR

Heh, yeah. A couple of reasons for this. After building the combat robot it's fun to get back to working with wood rather than metal and plastic. Also, this is a good time of year for me in terms of free time in the evenings, and a great time of year to not be sweltering hot or freezing cold in the shop. Plus, I'm just really excited about the project. :) Lots of cool new ideas and techniques for me in this one.

 

15 minutes ago, StratsRdivine said:

 

Bent laminating seems tough on such a tight radius, so I assume you might endup cutting that curl from solid.  But then again, about six layers of veneer side grain would do it too, although you are more likely to make the whole horn from solid right?  

 

Cool idea how you did the kerfing of your bend. That could come in handy down the line. I don't think my bend will be quite that difficult for this project!

So, mandolins typically use bent sides (and not 'usually' of laminates), but the thickness of those ribs is generally down in the 2 mm range, which makes the bends possible. And sometimes they are thinned down even further in the tighter corners. My plan is to do it that way, and have the side ribs interface with the neck block in such a way that once you get into the inside portion of the scroll the headblock will function as the outside rather than the ribs. That doesn't sound too clear as I type it. But it's the common way that F style mandolins are built. Here's a picture of the headblock design , where you can see the ledges where the ribs will interface/end. 

Headblock.thumb.jpg.c3dd414bd3469919fc781e11d084c1ea.jpg

Share this post


Link to post
Share on other sites
24 minutes ago, mattharris75 said:

After building the combat robot

Oh man I forgot to ask about this. Did you just think it would be a cool project or was there hope of getting on Battle Bots?

SR

Share this post


Link to post
Share on other sites

Actually, I built a 'baby' bot, not one of the big boys. They have different weight classes at most robot combat events. Antweights - 1 pound, Beetleweights - 3 pounds, Hobbyweight - 12 pounds, Featherweight/Sportsman - 30 ounds. And on up it goes, all the way to the 250 pounders from Battlebots. The insect classes are the most popular, due to cost, and the Beetles are generally a lot more destructive than the ants, so that's what I went with.

So, one of my best friends was on Battlebots this past season. He was with The Chaos Corps who fought Bombshell. They made a great run and finished as runners up on the show. So, my family got really into watching the show, and my seven year old daughter decided she wanted to build a bot. So, I let her help me with the rough design, the color scheme, the name, etc. So, we came up with 'Rainbow Gash', the My Little Pony themed beetleweight undercutter. It was a really fun process, and a big time learning experience. Here's a pic of her:

15895537_10155588999884325_7660412790346980256_o.thumb.jpg.e92b106c2747ced4267a82ef7e0463ee.jpg

 

We fought her at Robot Battles 62 at Chattacon back in January. We took out the five time defending champion in the first round, and then lost to the winner and then the runner up in the next two rounds. It was a great experience.

So, a local tech education website wanted to do a video on robot combat and I volunteered, and they made a video of us from the event:

Our full fight videos are available on the Robot Battles YouTube channel as well.

 

I had a lot of fun with it, and so did my daughter. I already have a new robot design sketched out, I'm sure we'll do it again. :)

  • Like 2

Share this post


Link to post
Share on other sites

Wow, laminating binding makes a bit of a mess... Hopefully the gunk that I got on there by having a little acetone on my fingers when touching the binding will scrape off.

I got the backstrap taken care of yesterday. Glued down and cleaned up. 

Most of my work today was checking, double checking, and triple checking measurements. Got the fretboard rough cut and determined the placement of my tenon for the neck joint.

The neck is going to be a combination bolt on and mortise and tenon joint. I'm still debating the best way to cut the tenon. I don't really know what common practice is there. I think I have a way that will work, but I should probably do a bit more research. I need to execute this step before I can cut the neck profile.

Updated pictures, just because:

20170408_122610.thumb.jpg.ecbfbfefb99c6c5fe051c34a7f8e0f6d.jpg

20170408_223322.thumb.jpg.19094c28f103b1f8cb53eeae93cc7a28.jpg

  • Like 1

Share this post


Link to post
Share on other sites
On ‎07‎/‎04‎/‎2017 at 5:49 PM, mattharris75 said:

Actually, I built a 'baby' bot, not one of the big boys. They have different weight classes at most robot combat events. Antweights - 1 pound, Beetleweights - 3 pounds, Hobbyweight - 12 pounds, Featherweight/Sportsman - 30 ounds. And on up it goes, all the way to the 250 pounders from Battlebots. The insect classes are the most popular, due to cost, and the Beetles are generally a lot more destructive than the ants, so that's what I went with.

So, one of my best friends was on Battlebots this past season. He was with The Chaos Corps who fought Bombshell. They made a great run and finished as runners up on the show. So, my family got really into watching the show, and my seven year old daughter decided she wanted to build a bot. So, I let her help me with the rough design, the color scheme, the name, etc. So, we came up with 'Rainbow Gash', the My Little Pony themed beetleweight undercutter. It was a really fun process, and a big time learning experience. Here's a pic of her:

15895537_10155588999884325_7660412790346980256_o.thumb.jpg.e92b106c2747ced4267a82ef7e0463ee.jpg

 

We fought her at Robot Battles 62 at Chattacon back in January. We took out the five time defending champion in the first round, and then lost to the winner and then the runner up in the next two rounds. It was a great experience.

So, a local tech education website wanted to do a video on robot combat and I volunteered, and they made a video of us from the event:

Our full fight videos are available on the Robot Battles YouTube channel as well.

 

I had a lot of fun with it, and so did my daughter. I already have a new robot design sketched out, I'm sure we'll do it again. :)

That's cool,  one of my favourite TV shows in the UK at the moment is Robot Wars.

  • Like 1

Share this post


Link to post
Share on other sites
On 4/9/2017 at 0:30 AM, mattharris75 said:

 

Wow, laminating binding makes a bit of a mess...

 

Did you make some kind of jig for this?

SR

Share this post


Link to post
Share on other sites

I ordered the StewMac binding laminator. I saw several people say that it was worth springing for. It worked fine, but just managing everything, pulling the binding through, brushing it on, etc, ended up leaving a decent amount of gunk tranferring from my hands to the bindings. The acetone dissolves it remarkably quickly. Regardless, it scraped off quite easily.

I ended up routing the fretboard to width and gluing on the bindings last night. All except the end piece, which will be a bit more complex, with the miters and curves and whatnot. I'll scrape the board  tonight and see if I can figure that out. Then I'll see if I can't finish up my neck tenon. I rough cut it last night and will run it through the router this evening.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...