Parlour Guitar - first "contemporary" build

[JD3971]

Hi all,

Started a new build recently, my third acoustic guitar and 9th overall (I think... if you count a banjo). This will be my first time stepping away from following plans and templates and into the method outlined in the Gore/Gilet books. My background is in engineering so this approach excites me and I'm looking forward to the build process!

It'll be a 12 fret guitar with X bracing and a live back. Not going to include carbon fibre - just keeping the number of new things at a time down.

So far I've collected all of the data on materials and completed the planning stage (spreadsheets, calculations, etc.) To arrive at a design.

Below are the highlights of the details. Any feedback is always appreciated!

Body:
Length - 468mm
Width - 332mm
Scale length - 632mm (24.9")
Soundhole diameter - 89mm
Depth - 100mm

Top (sitka spruce):
E_L - 8.75 GPa
Sound rad coeff - 14.26
Resulting top thickness - 2.36mm
Resulting top mass - 102.81g

Back and sides (white oak):
E_L - 33.82GPa
Sound rad coeff - 6.48

Structure (with braces):
Flexural rigidity - 48.13 Nm2
Peak stress on braces - 31.36MPa

[TallDad71]

That sounds like a great project. Lots of photos would be appreciated.

Good luck

[JD3971]

Certainly! Will post some pictures soon. Almost done with back bracing.

[JD3971]

Progress so far. Have to finish shaping the back braces and then moving on momentarily. Sides bent last weekend (this oak bends so easily, btw). Will be doing laminated kerfing so that'll be next.

[kiwigeo]

Thanks for the update pics.

One question....you've glued in back braces with the back not trimmed to side outline? Is there a reason for this?

I ask because shaping bracing to fit the dish radius is a bit tricky without trimming to final back shape.

[JD3971]

I ask because shaping bracing to fit the dish radius is a bit tricky without trimming to final back shape.

I radiused all of the braces beforehand - I have a jig for this (I think similar to the one shown in the books, IIRC). Everything glued up in the radius dish with go-bar deck.

One question....you've glued in back braces with the back not trimmed to side outline? Is there a reason for this?

This is a good question - I wish I had a better answer than just that's the way I learned it

Am I missing something?
Braces cut to approximate length, then radiused, then glued to top in dish.

[Mark McLean]

I am like Martin and cut the back into a “guitar shape” before starting to do the bracing. However, I can’t see any problem with the way that you do it as long as it still conforms to the radius that you intend. White oak looks very pretty. Is it heavy?

[JD3971]

White oak looks very pretty. Is it heavy?

I think it should look nice too. I know the light sides/back isn't everyone's cup of tea but it'll be a good experiment at the very least.

It's definitely on the denser side. Measured at 930kg/m3 so a good ~20% more than Indian rosewood.

[JD3971]

Bit of progress made last weekend. Glued and carved the X-brace and made the rosette. Finger braces/tone bars/whathaveyou glued up.

[WJ Guitars]

Great to see progress on your parlor guitar build. Recently, I have been ask by a client to build a parlor guitar and I am looking at a range of parlor design's dimensions and specifications. In your original post:

Body:
Length - 468mm
Width - 332mm
Scale length - 632mm (24.9")
Soundhole diameter - 89mm
Depth - 100mm

In my investigations so far I have seen three soundhole sizes:

100mm diameter
97mm diameter
95mm diameter

I understand that parlor guitar's body are small in size and for a parlor guitar build aiming for the desirable Main low Resonance Frequencies may be difficult to achieve. Maybe reducing the size of the soundhole could slightly help to lower the first low resonance frequency? Are you able to advise what is the background behind choosing the soundhole diameter of 89mm? If the soundhole becomes too small hand access inside the guitar body could be an issue.

Wayne

[JD3971]

Are you able to advise what is the background behind choosing the soundhole diameter of 89mm?

Hi Wayne. Yeah it's in an effort to keep the helmholtz freq as low as practically possible. I was looking at other folks' parlour builds and seeing 115-125Hz. I've built one before myself and ended up with 123Hz (albeit, before I knew what I was doing). I think the rule of thumb from the books was every 2mm in diameter roughly translates into 2Hz but my goal was just "as small as possible".

It was actually another builder who had done a couple parlours and suggested I do 89mm. It's what I used on my first parlour build too. It's definitely tight getting in there; I anticipate some difficulty if I need to shave down the back brace or add side mass. But I have a lady with small hands that I trust enough to help.

[WJ Guitars]

Thanks John for the information and reasons relate to your decision to have 89mm diameter sound hole.

Its early days for me being my first Parlor Guitar build. The body size that I am using is slightly large than yours and the proposed depth is 112mm at the tail and 86mm at the neck. It will a few more months before I will commence building. I need to make a few more jigs to suit my Parlor guitar build. This will include making some falcate bracing jigs that will work for the Parlor guitar design, plus calculating and making side patterns. See photo below

I will keep an eye on your ongoing posts of your Parlor guitar build progress.

Wayne

[kiwigeo]

I have a falcate braced parlour guitar sitting on the bench awaiting re-finishing. I basically followed a plan for a Gibson parlour. I forget where the top and Helmoltz peaks were. I'll give it a tap test tomorrow and return with the data

[WJ Guitars]

I have a falcate braced parlour guitar sitting on the bench awaiting re-finishing. I basically followed a plan for a Gibson parlour. I forget where the top and Helmoltz peaks were. I'll give it a tap test tomorrow and return with the data

That would great Martin to have this data. I also have the Gibson L00 Plans for comparison with the Martin 00-12 Parlor dimensions

Wayne

[kiwigeo]

I got busy with domestics today....sorry.

Tap testing first job for tomorrow

[WJ Guitars]

See Photo attachment showing dimension comparison between Parlor Guitar 00-12 Martin and Parlor Guitar Gibson.

Wayne