Mark (TheCraftsmansPath.com) on March 30th, 2008

The next step in building of the guitar was to do some work on the back. Braces are needed across the back and down the center seam to arch and reinforce the back. As I mentioned in the previous post, the back is radiused from neck to tail and also from side to side so, some creative clamping solutions were in order.

Building the Go-Bar Deck

There are a few alternative methods that can be used to clamp the raduiused braces to the back. Though, most involve the use of a lot of deep throat cam-action clamps. I do not have any of these in the workshop and it would be a fair amount of work to make them so, I opted for an alternate route.

A very old method often used by luthiers to perform this clamping task is to use flexible sticks of wood or other material to brace the objects to be clamped between between two fixed parallel plates. The fixture to do this is called a Go-Bar Deck and usually makes use of flexible wood or fiberglass rods to clamp parts of the guitar during a glue-up.

Go_bar_Deck.JPGI made a very simple version of the Go-Bar Deck with some 24″ x 24″ particle board pieces and some threaded rod. As you can see in the picture (click for larger view) the threaded rod is used to stand off one particle board plate from the other. I did also glue on some reinforcing strips to the bottom of the lower plate as well. The threaded rod is screwed into T-nuts in the lower plate and secured with a washer and nut. In the upper plate, there is a washer and nut on both sides of the plate to lock it into position on a plane equidistant from the lower plate.

Preparing and Clamping the Back Braces and Center Reinforcing Strips

Cleaning_for_Back_Braces.JPGBecause Rosewood is a tropical wood it can sometimes have residual oils on it, the first step I took was to layout for the braces and then clean the areas for the braces with some Naptha. This step may not have been necessary but, because the radius on the braces will force the back into a fairly significant arch, I wanted to be sure that there was a good glue bond. However, even with the Go-Bar Deck for clamping, the braces could not be clamped to a flat back so, an alternative was necessary.

Back_Braces_Clamped_in_Go_bar_Deck.JPGMany luthiers will use a radiused dish for the purpose of backing the back plate to maintain the needed arches. Two of these dishes would be required (i.e. the back a top have different radii) and I do not have them in the workshop. They can be made by dishing out MDF with a router and a jig but, I was not too interested in the copious amounts of dust this would create. My alternate approach was fairly simple. I created some strips of hardboard to place under the edges of the back plate so that when the braces were clamped to the back the appropriate arches would be formed into it. In the picture, you can see the back with the four main braces clamped in the Go-Bar Deck. I used 5/16″ wood dowel rod with rubber screw protectors on the ends as the go-bars. You can also see the strips of hardboard under the edges of the back to maintain the necessary arches in the back.

Glued_Up_Back_Braces.JPGBack_Radius.JPGBecause this was my first attempt at this, I decided to clamp just the four main braces as a first attempt. It’s amazing how much even clamping force can be applied using this method. Because the wooden dowel rods were under a fair amount of pressure, I made sure to wear eye protection during this operation – I was concerned that one of the go-bars could shatter while I was working on this. In the picture you can see what the back looked like after the glue up of the four main braces was complete. In the second picture I attempted to show the arches that were forced into the back during this operation.

Center_Reinforcing_Strips_Clamped.JPGGlued_Back_Braces.JPGAfter the clamping of the four main braces was completed, I still needed to add the center reinforcing strips to the back. The process for this was the same as for the braces. Though, I did add some spring clamps for the two end strips because they tended to slide around a bit when the go-bars were applied to them. I think that my concern regarding the wooden go-bars was a valid one because when I returned to un-clamp the center strips in a few hours, I found two of the wooden go-bars broken and lying on the shop floor! Luckily, this must have happened after the glue had already set, so there was no issue. However, I think I will attempt to find some fiberglass alternatives for the clamping of braces to the top.

Shaping the Back Braces

Shaping_Back_Braces.JPGThe back braces were rough shaped prior to gluing them to the back plate. However, the idea behind bracing a guitar is to achieve a strong, stiff back without adding excess weight. The shape of the braces also affects the sound of the guitar and how it will project when played. These braces extend all the way to the ends of the back and will intersect the sides and kerfed linings. So, they needed to be trimmed down to about .100″ at their ends. I did this with a sharp chisel and a caliper, checking the thickness as I went. After that I did a quick sanding of the braces just to clean things up.

Next up will be the bracing of the top and assembling the back and top to the sides. That effort will also call into play some unique clamping requirements. I’ve already started gathering materials to accomplish that task. Until then, please feel free to contact me via e-mail at thecraftsmanspath@gmail.com or leave comments or questions here using the comments link at the end of the posts.

5 Responses to “Dreadnought Guitar: Adding the back braces”

  1. Terrific progress, Mark.

    As I may have already mentioned, I know *nothing* about making musical instruments. But I did not even have to look up the term Go-Bar Deck, as I learned it yesterday while reading a post at Lumberjocks. What a neat solution to a complicated glue-up!

    1) Are the go-bars are usually fiberglass? ‘

    2) Were they made of wood in the old days? And would laminated bars be better than rods?

    3) How do you clean glue squeeze-out under the braces? I wonder if you scrape it clean after it gels a little…

    Thanks, Mark!

  2. Hey Al,

    Yeah, the Go-Bar Deck is a pretty neat fixture – perfect for this kind of application.

    In the commercial versions of the Go-Bar Decks, the rods are usually fiberglass so they can bend and return to form without issue. In the old days, I would think that they were probably made from thin strips of a hardwood that has some elasticity (maybe Ash or something like that). I could have gone that route but, I tried the wooden dowel rods instead – a flat strip of wood actually may have been a better choice because it probably has less tendency to shatter. I did find a source of some fiberglass rods (salvaged from a different purpose) that you’ll see in the next post.

    The glue squeeze-out is a bit of a pain…I have been waiting until it gels and trying to get in there with a pointy piece of scrap and a wet cloth (no risk of finish issues here because the inside will not receive any). Of course doing this without moving any of the clamping rods is quite interesting, to say the least!

    –Mark

  3. hi mark fiddley work takes a lot of time looks good i am on my 2nd guitar got my plans from j kinkade he has a brillant book out check out the first guitar i made on my web site and here it played good site thanks robert

  4. Robert,

    Thanks for stopping by the site. I’ll have to check out Kinkade’s book. I had heard it was a good one. Your guitar is very nice and you play it well. I’m still working on this one as it is a project to fill in between other projects for me!

    –Mark

  5. very good reading and reference to newbees like me. good work

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