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I can't find any videos on how to go about doing this. I'm sure I can figure it out but I don't want to reinvent the wheel. Are there any videos?

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Hutch

Get the heck off the couch and go build a guitar!!!!

Not a video, but Messrs. Cumpiano and Natelson demonstrate a non-dish technique in their book 'Guitarmaking: Tradition and Technology' - it seems to work for those building in that style.

In terms of videos that might help you fabricate a shop-made fixture should you choose to do so, Mr. Chris Paulick has a video on fabricating a radius dish (we did a set here in house using a different jig that suggests Mr. Paulick's approach is to be preferred to the boss's somewhat over-engineered solution).

https://youtu.be/tvGemvizrz4

Also of interest is Ms. Gardner's very British approach to the job, as well as a number of other shop-made jigs, fixtures, and appliances. I do delight in her ability to avoid taking herself too seriously and her mix of craft and technology (e.g., given the sagitta and length of the runner rails, she calculates the distances from chord line to arc segment, versus plotting and printing out a radius template...very shop math-ey).

https://youtu.be/zwLh41THU1M

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For the times they are a changin'

- Bob Dylan

I can help you build your guitar but that isn't enough information.
What type of guitar?
What method?



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Ken

After some research, I came up with this:

https://www.flickr.com/photos/ruby1638/7998042643/in/album-72157631562735639/

Go through about 3-4 shots to the right to see the sequence. The washers on top of the 1/2" bolt hold the batten at the right height to line everything up without digging into one side or the other - just keep equal pressures on both ends of the batten. These shots are of treating the rim before the lining is installed - you do it again after lining.

I also use the 2 battens I made (top and back) for marking the arch on the braces, for sanding the arch into the bandsaw-cut braces, and for gluing the braces onto the plates - one at a time, but it goes quickly.

I have built 8 with the rig and it is easy enough and goes fast enough that I probably won't invest time or money into dishes - go slowly and sight across the body to keep things even.

Ed

Thanks, I've seen those videos and may try it sometime but for my first guitar I don't wish to use one. If I can make it work then I may never use one.

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Hutch

Get the heck off the couch and go build a guitar!!!!

Ken, this will be a D28 style. As for my method, a sharp plane wherever I can.

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Hutch

Get the heck off the couch and go build a guitar!!!!

I was setting up the bench for planing the sides, bought double stick tape and I'm ready to go. First I measured the thickness as they came from Martin 1833 shop. To my surprise, measuring with cheap calipers that only measure to .01, the sides are .07 to .08. I guess I don't get to play with my handplanes as they're already there. EIR by the way.

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Hutch

Get the heck off the couch and go build a guitar!!!!

Without a dish it can be tricky. When I was first started building I was following the Robbie O'Brien video and he had a template for cutting the sides. He then said "Now, how did I get this template? I built a few guitars!" I was like, what the heck, Robbie!

Anyway, the Georgia luthier supply online plans had a side profile in them. What plan are you using?

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I use an radiused 2x4 like Ed showed above and the only thing I would add is to constantly measure the side depth. It's easy to take off more material in one spot over another. So with a 6in ruler or something like that just measure at key points on both sides so that your depth is right. I never liked the Cumpiano and Natleson method because while it shapes the sides ok it leaves the linings flat. That's fine for the top but the back is arched.

There are at least four distinct methods that I know of to define upper body geometry and get a good fit on the extension and desired string height at the bridge, so having some idea of which one you plan to use helps with answering your question. Not every approach is mutually compatible with every type of tooling, and I believe Mr. McKay's question on your build method was intended to save you some head-scratching or at least some on-the-fly fixes to address potential neck fit issues.

I cannot speak for other build/repair shops, but we see enough first guitar builds come through the shop to know that - next to fretwork - neck geometry and fit on the extension is the biggest functional issue for new builders, so worth the time to understand which steps establish that geometry.

_________________
For the times they are a changin'

- Bob Dylan

I'm using the StewMac plan. No side profile.

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Hutch

Get the heck off the couch and go build a guitar!!!!

Burt, I don't know what method I'm going to use but I considered using a center post with the radius cut into a board to swing around to check the height.

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Hutch

Get the heck off the couch and go build a guitar!!!!

You need to get some new cheap calipers These do thousandths of inch/tenths of mm for under $6 (but doesn't include a battery... takes 357 size button cell) https://www.banggood.com/ANENG-150mm-6inch-LCD-Digital-Vernier-Caliper-Electronic-Micrometer-Carbon-Fiber-p-1224561.html

For box building, I glue the sides to soundboard with dentellones (creates a mostly flat perimeter). Then plane the sides to create the head to tail taper, and make it more or less flat for now (check against the bench and see where the low/high spots are). Then glue back linings and plane those down to the sides. Then tape 3 sheets of 60 or 80 grit sandpaper together, clamp one end to the bench, and drag the guitar on it to create a cylindrical back radius (straight from head to tail, but curved across the width) by tilting the box back and forth as I sand. Sand again with 150 grit before gluing the back on. Don't worry about getting the radius perfect. As long as you're not using a rigid dish as a caul when clamping the back on, it will conform to the rim shape. I use spool clamps.

If you have access to another dreadnought you could wrap a piece of paper around it and trace the side profile. That might get you close to what you need.

Clay

Another method of that is to put a piece of masking tape on the side from center at the heel to a known distance from the center under the neck - say 1-1/2". Then measure the side height in 2 inch increments, take the tape off and stick it to your side and reproduce the dimensions. The top is usually flat enough, even if dished, that it can be considered to be flat for these purposes.

Ed

duplicate

Ed

Hutch, the top is fairly simple since it is basically flat all the way across with a 25 or so foot radius to the dome. You should be able to sand it perfectly flat, then add the angle all the way around the rim with a 25 foot sanding beam.

The back is more problematic. For my first couple since it has a significant dome from side to side plus it drops off towards the neck. For my first couple of guitar I sanding the rim flat kind of following the Cumpiano method, then made a 15 foot radius sanding beam and tried to add the angle to the rim. It worked but I believe that it makes the area at the waist too shallow, when I glued the back on I had to apply a lot more clamping pressure than just closing the gap. The guitars are ten years old and haven't blown up yet, but I wasn't satisfied with this way of doing it.



I went out and bought radius dishes for the next one.

That's why I was thinking of attaching the sanding beam to a post in the middle with a height adjustment. Maybe I'll just make the dish and get on with it.

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Hutch

Get the heck off the couch and go build a guitar!!!!

I started down the road Freeman did and then when I got to the back it became such a pain I just stopped and made the dishes. Been using them ever since. If you're anywhere near Knoxville I've still got the jig to make the dishes and you're welcome to use it.

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Steve Smith
"Music is what feelings sound like"

Thanks Steve but we're a long distance apart. I'm in RI.

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Hutch

Get the heck off the couch and go build a guitar!!!!

A bit of a drive to be sure.

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Steve Smith
"Music is what feelings sound like"

I do recommend making or buying at least the back dish - you'll start using it when you make your braces and glue them on, and it will save a lot of trouble with sanding the rims. I believe that you can get by with a flat surface for the top and a sanding beam like my picture.





I heard somewhere of a guy hanging his router from a tree with a 15 foot piece of rope and swinging it back and forth over a hunk of MDF - seems like a sled would be better LOL

I'm convinced I should start with at least one dish. Problem is deciding on the size. Is it 15 or 20 for a D28? I'm going to buy rather than build now that I know I only need the back one.

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Hutch

Get the heck off the couch and go build a guitar!!!!

15'/28' for us, but those radii are based on what has worked well acoustically, gives the correct fretboard extension fit with the building system, and provides adequate range on handling RH changes. Back radius does have some impact on acoustics, but there's no real coupling between back radius and the neck/body geometry we need to establish...in other words, you might just pick something that has worked for others and go with it.

For top radius, it's really a question of the building system. If you'll be wedging the upper bout to establish the fretboard extension fit, those builders using that approach seem to build with anything between 20 and 30 foot radius. For those using a flat or nearly flat 60' UTB glued on a flat caul, 28' radius provides good extension geometry for 12 and 14 fret bodies from Size 5 to 12 fret dreadnaught.

Having both dishes allows the body to be braced up and closed in the go-bar deck, which eliminates a lot of clamps. With a deck and dishes, 48 bars (24" x 3/16" with vinyl caps from Goodwinds) will run $80 delivered...or about the cost of 4-5 good cam clamps, and will let you get by with far fewer cam and F-style clamps. Also an option to rip up some straight-grained hickory or ash to make up wood spring bars...$15 worth of 5/4 stock gets out a lot of wooden bars.

_________________
For the times they are a changin'

- Bob Dylan

I notice you don't have a large piece of sandpaper stuck on. Do you remove it after sanding the sides?

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Hutch

Get the heck off the couch and go build a guitar!!!!