Parlor Guitar bracing

[Paul Eisenbrey]

Hi folks,

I'm working on a parlor guitar for my Grandson, and it is nearing the point where I'll close the box. Pretty exciting, I know . But something is bugging me about the bracing. I used the bracing measurements from Cumpiano's book, which has worked well for me in the past. But that was on a OOO sized guitar. The darn things look incredibly massive on this tiny little soundboard.

They may be the right dimensions: the strain on the guitar's top won't be smaller just because the box is (the scale length and tuning will be standard (24.5")). So it may be I should leave the braces the way they are. But I have this nearly uncontrollable urge to get in there with a chisel and really carve down on their height before I close the box and they become difficult to get to.

From those of you with experience making smaller bodied instruments, should I leave the braces tall, or should I shave them down some?

--Paul

[woodrat]

Hi Paul...I think you will find its definitely overbraced...the OOO in the Cumpiano book is overbraced too....I built 3 of them before I realised that, ...though they were my first 3 guitars and I built them together and I didnt know anything at the time

.....I have just ripped the top off my 5th guitar that I built almost 5 years ago and put a much thinner one on and lighter bracing as well. The original one had massive bracing and that made it sound thin, metallic and boxy although it was plenty loud enough. It was bought by a friend who loved it but each time I brought a new guitar around for him to hear his didn't sound as good...my progress as a builder had made his guitar sound worse...so I brought it home and proceeded with major surgery..If you have the back off nows the time to do it.

John

[Allen]

Keep in mind that the cube rule applies to a beams length as well and it's hight. So if you have 2 beams of a given dimension and one is 1/2 the length of the other. The shorter one is 8 times as stiff ( those engineering folks out there please forgive if my terminology is off ).

The long and short of it is that if you have a smaller body, you will be able to go with a thinner top and lighter bracing.

[auscab]

.....I have just ripped the top off my 5th guitar that I built almost 5 years ago and put a much thinner one on and lighter bracing as well. The original one had massive bracing and that made it sound thin, metallic and boxy although it was plenty loud enough. It was bought by a friend who loved it but each time I brought a new guitar around for him to hear his didn't sound as good...my progress as a builder had made his guitar sound worse...so I brought it home and proceeded with major surgery..If you have the back off nows the time to do it.

John

I'm envious of your hard earned knowledge there John and Allen

Paul,
I don't know if this could help, it's a link to Frank Fords web site with some good pictures inside a Martin 1-26 parlor, it's for gut strings ,so for steel strings on a guitar this size the braces should be taller than these, but by how much I do not know ? At a guess I would think 2 mm. John or Allen ?

check out just under day 5
http://www.frets.com/FRETSPages/Blogs/1 ... 126_1.html

This size 1 is 12 7/8 lower bout 9 1/4 upper bout,sizes taken from the 1/18 gal plans by Ted Davis
on Teds plan height at the X intersection is about 13 mm and under the bridge it's 6.5mm [ for gut ]

What size is the parlor or parlor you are doing ? any pictures ?

And size 1 is within parlor dimensions ,isn't it ?

[woodrat]

Hi Paul, here is a link to a pertinent picture in the FRETS link that Rob supplied....http://www.frets.com/FRETSPages/Blogs/1 ... 26_050.jpg

Conveniently he has a metric set of calipers and the top is about 2.3mm although this is an 1867 guitar so may have only ever been strung with gut although it looks like its a steel stringer to me. I dont know much about the history side but I thought that steel was adopted in the 20th century...

Hope this helps

John

[Paul Eisenbrey]

Hi Guys:

Here is a picture with the braces rough carved:

Bracing_Small.jpg (81.97 KiB) Viewed 12304 times

The Frets.com pictures make it very clear that I am substantially over braced. I am going to pull about 1/3 the height off of the x-braces, and thin the top down some. Currently it is around 2.9 - 3.2 mm, depending on where I measure it.

Thanks for the advice -- I'll post more as I progress. If I thin it too much and it implodes, I'll post the disaster, too.

--Paul

[woodrat]

Hi Paul, here are a couple of pics of my Parlor that I mentioned earlier in this thread. It was my 4th instrument after finishing my first 3 from the Cumpiano Book. I thought I knew everything when I finished them and to prove that I would "design" my own guitar...I came up with a pretty horribly proportioned parlor that I was never happy with really. I lent it to a friend to play and he wanted to buy it from me, which he did...but as I mentioned every new guitar I made and showed him his guitar sounded worse and worse so I said a couple of weeks ago that I would take it home and rip the top of and put another one on that would make it sound much better. I ended up using a top that got too thin for a larger guitar and that had also got damaged by having about 1 1/2 inches split off the edge...So I reglued the piece back on the edge and decided to use that on the project. The top is some Sitka that I got from Gilets about 3 years ago and it had "8 years air dried" penciled on it so it is well "aged" I suppose.
With regard to the braces I used old tight Douglas fir that are 6mm wide and about 13mmhigh at the intersection of the x. The original bridge plate was about 3.2 mm thick blackwood (way too thick) and on the new top I have used 2.5mm Forest Oak which I find makes great bridge plates.
I also got to address the issue of neck balance. I originally made the neck from Blackwood that was very dense and that made it very neck heavy. I thought about it for a bit and said to myself "if I can pull the truss rod back out of its slot then I can saw the fingerboard off and the headplate with the inlay in it off and reuse them on a new neck of lighter timber. The truss rod came out easily after I took the tension off it. I then sawed the fingerboard and headplate off and scraped the old glue and sliver of neck timber off and made up a new neck from Aussie Red Cedar which will be much lighter and should be strong enough as its a short scale and has a truss rod.
So I am glad that I have done it (squirted some lacquer on it yesterday) and I know that its owner will appreciate the sonic upgrade. I will post some of it when I finish.
I thought that I would post and tell the tale as your situation was pretty much the same with your parlor and its bracing.


...anyway here are a few pics...

[Paul Eisenbrey]

Hey John,

I'm ahead of you in one (and only one) respect: I got the 'new design' issue out of my system on my first build. Ugliest guitar in the solar system.

Ripping the top off your guitar, regardless of how much you've improved since you built it has gotta hurt. I am curious about how you plan to take the remaining top off of the lining without over-softening the glue holding the lining to the ribs. But you've probably got that sussed out.

Anyway, I finished carving the bracing down. Doing it at the awkward angle imposed by the attached ribs was a new kind of exciting. And I did it without gouging the top, too!

Here are some pics -- the neck is still just rough carved (obviously).

DSCN0126.JPG (158.56 KiB) Viewed 12158 times

I had my grandson sign the soundboard -- I figure if he keeps it long enough, his kids can have a laugh at his expense. Assuming they think to get a mirror and have a peek inside...

DSCN0125.JPG (147.31 KiB) Viewed 12158 times

[woodrat]

Hi Paul, It is not too difficult if you have the right kit! I used a laminate trimmer set to just shy of the top thickness and skipped that around the edge after I sawed the top off. Then I sanded the bindings and what was left of the top from the linings on my radius dish sander that a friend helped me make from an old lathe headstock and faceplate. So I aim to sand the old glue just off and there I am back to being ready to glue a new top on it. I will post a few picks when I am finished. Actually I made the original instrument before I had radius dishes to I lost a bit of body depth. About 1/4 of an inch.

Your parlor looks good...I haven't done a sound port yet so thats something I have to try!

Also were your braces 8mm (5/16 in) or 6mm (1/4 in)? Mine are 6mm on the new top...it makes a difference too.

Regards

John aka WoodRat

[Paul Eisenbrey]

Hey John,

Sanding... there's a new concept

The braces are 8mm -- I couldn't think of a way to thin them laterally without gouging the top, so 8mm they will stay. I'm making another Parlor after this one, for my granddaughter. It will have 6mm braces, at the right height, *before* I glue them in. That might be easier all around.

Thanks again for the advice!

--Paul