attaching bridge

[Troles]

I will try to be brief with my issue. First time building using the Natelson & Cumpiano book. I am at the point that my top/neck/sides are all assembled, now I am supposed to glue on the back.

Here is the wrinkle. This is a 25" scale full size neck 6 string classical, BUT, I built a concert Ukulele body for it. (i know, weird, sorry) So, bridge will have force of a standard 6 string classical. So, the Cumpiano book wants to to finish assembly, even the laquer finish, then put bridge on last.

Issue, only a 2 1/8" soundhole. So I made a custom caul to fit over the bracing on the top where the bridge will go, but I don't know how to get it into place once the body is closed, let alone get 2 + clamps in that soundhole.

With full size you can reach hand in and get caul in place inside, then get clamps on it, etc.

I suspect with a true Uke, clamping the bridge well is less an issue with the 4 uke strings under less tension.

I kinda want to glue fret board on now, so i can measure and glue bridge on now, before the back is put on. But no one seems to do this
Thoughts?

[Ned Milburn]

Hmmmmm... A few things.

Most classical dimensions are in metric. Standard classical scale is 650mm. Long scale is 660 or 665. Short scale is 640. Your measurement of 25" comes up as 635mm, so already you are shorter than short scale.

I am guessing (but not convinced) that you are building with a Spanish heel...??

Why the Uke body classical guitar....???

Before you glue on the back, you could easily glue on the fingerboard, then bridge. You would just need to make sure you get the neck angle right when gluing on the back.

I recently built a steel string guitar (flat top) with F-holes and a custom bracing pattern. This guitar required the bridge to be glued before the back, so that is what I did. The main reason it is not regularly done in this order is likely to facilitate a reasonable building procedure, but also for repairing instruments, since access to the inside of the body is necessary, most guitars are built with soundholes big enough for hands to fit inside.

PS - WHOOPS!! I missed the part about the Uke body with a classical neck.

[charles Tauber]

Originally Posted by Troles

I kinda want to glue fret board on now, so i can measure and glue bridge on now, before the back is put on. But no one seems to do this.

If you have made templates and are accurately making components to those templates, there is no need to attach the fret board so that you can determine where the bridge goes. You already know exactly where the fret board will be and where the bridge needs to go. For example, if the neck joins the body at the 12th fret, if you know where the outside edge/surface of the body is at the neck, measure from that half your scale length (25"/2) and add suitable compensation length. Sand/plane the end of your top flat - or to suite your body shape - so that you know exactly where its extent is - that is the neck end of the body. Measure from that end using that edge as your reference. Plan what you use as references/datums (i.e. data, but in 'Merican English).

Lutes are an example of instruments with glued bridges and no access to the interior of the body. Lute bridges can be glued to the top prior to the top being attached to the body, or they can be (carefully) glued with clamps that traverse the exterior of the instrument, gently squeezing the bridge against the top. (Lute tops are often only 1mm thick.)

Regardless, my recommendation is to work accurately to accurate full size templates - or CNC machines. For one-off's and experimental designs, I use poster paper - easy to cut, sand and inexpensive, but holds up well and provides sufficient thickness to allow a pencil to be guided by its edge.

Lastly, have you planned for "failure" - the need for repair? One option is to leave the top and/or back without binding and glue with fish or hot hide glue, to allow relatively easy access to the interior in the event of repair. Lute tops are traditionally fitted with binding/purfling that extends only half of the thickness of the top, giving the appearance of being framed by binding while still leaving the top/body glue seam accessible.

[Troles]

thanks guys. i know it is odd to do uke size on 6 string classical, i did itpartly to have a small "backpack" guitar, and partly because i got some free Wendge and Spruce to build the body that was that size. its my first, so I know i will make mistakes, and this is largely a practice build (i already got my rosewood b/s and top for my full size which will be my next build.

I guess i will just put bridge on now. its true with my templates i should be able to locate exact placement. Also, with spanish neck already in place, angle is set, and with Cumpiano style build the exact neck angle is determined by planing an angle into the fretboard.
Only real negative I see is trying to laquer and sand all those coats with the bridge in the way.

Thanks for advice, and any others who may still want to chime in.

[Ned Milburn]

Originally Posted by Troles

Only real negative I see is trying to laquer and sand all those coats with the bridge in the way.

There are challenges to both finishing first then installing the bridge, and installing the bridge first then finishing. Either way works.