[Antz_Marchin]

Hey acoustic guys, I just have a quick question about bracing. My first guitar is basically a learning experience for me, both for learning how to use the tools and the actual construction so I'm having fun with just loosely following plans and trying some different things with the bracing.

One thing that I didn't look for closely enough at pictures before I started carving is the X bracing. I got it mostly right but I scalloped the top arms as well, which I realized later are just usually tapered in a gradual slope from lap joint to end. Now my X-brace is about 15mm high and down to 6-7mm in the scallop. My top is rock solid with very little flex and although I have no experience with tap tone, it rings and sustains very loud all around the top like a thick skin on a bong drum.

All that I want to know before moving on is, will scalloping the top arms cause a structural issue for my top? If I flex it by hand pretty strongly and it doesn't move/flex at all, is this a decent indication that I should be ok once the strings are on? There's a picture below, everything is pretty close to a conventional bracing pattern other than my little mix up on the top arms and my "perforation" of the finger braces and tone bars to lighten things up a little.

http://www.flickr.com/photos/[email protected]/1479712718/

Any advice would be great. Thanks

 

[Soupbone]

Looks like a guitar top-cool shape!

Just my opinions below.
The two peices on the bass side look too heavy epecially in the centre. Dont tapper them to the main brace, just keep the tops even if you musst reduce dont go below half. Thats where you need the strenght. Tapering them too much where they meet might renders them structurally useless.

The joints where all the peices must come to gether and fit tightly and as perfect as possible.

The top brace above the soundhole looks too light.

The use of lighting holes is a nice idea but being your first guitar I would not bother with them, it could cause problems you dont want at this stage.

The most important aspect is the grain direction. Use only sticks split from good spruce stock. Keep the grain standing up. Like plywood on its edge.
Scalloping ???Another nice idea but why bother?

I would just use the standard size as far as height and width. Just measure pretty near anything will work.
The top should be an 1/8th thick before hand sanding or 2mm will work too.
Dont sand too much when finishing it up, and mask the outside of the top with paper untill the box is totally constructed. Otherwise youll have mars and possibly scratches.
NEVER sand in the wrong direction on spruce even a little bit or youll be cussin'.
Personally I always capped the lap joint with a small square of the bridge plate stock rather than use that cloth shit. If you have a perfect fitted joint you dont need anything.

Good luck and keep us posted.

 

[Antz_Marchin]

Hey Soupbone, thanks very much, I really appreticate the reply. I'll try and touch on everything you mentioned.

Based on your advice, I will be trimming be sanding those bass side bumps down a little still (you meant on the X right??). The top was thickness sanded to about 2.2 - 2.3 mm and I only use 360 grit on it in the correct grain direction when sanding (if at all). Grain was definitely carefully checked and rechecked before cutting/radiusing each piece of bracing. Only vertical grain anywhere on the guitar.

I know I didn't need to scallop or do the holes and in hindsight, they may be a little much but to be honest I did lots of reading on construction and not too much on bracing until I started carving. I was excited to get into things :smile: I have read through it now and will be better prepared for my second guitar, at the same time I don't think I have made any critical errors with this soundboard and am excited to hear how it will sound (very unique I'm hoping).

What looks to be a very light transverse piece above the soundhole is actually a go-bar shadow. I didn't have my upper transverse bracing done yet in this shot but it was the only one i currently had on my computer with my X-bracing that I wanted to ask specifically about. I have a nice chunky transverse brace above my soundhole with a thin transverse graft above that yet with a truss clearance notch chiseled into it. Lastly I will be adding the bridge-plate this weekend (osage orange) and funny you mention the cap, nice little piece of osage orange is currently sitting under a couple of gobars as we speak cover the lap joint.

As long as nothing on my X looks to thin I am happy :banana: Sides are bent, top and back are braced.....next stop head and tail blocks and their many crazy angles everywhere I'll post a pic of the completed top/back soon and if you could let me know what you think, that would be great.

 

[Soupbone]

it will be fine-

HI Antz'-Just to clarify some of my muddleness-:

"just keep the tops even if you must reduce dont go below half. Thats where you need the strenght. Tapering them too much where they meet might render them structurally useless."

I was just pointing out that althought the smaller braces are tapered where they meet the mains they should only taper the length like to the top.

I usually used to just take a knife and cut the end where the go to the other big braces-on a 45 more than this will make them too thin-IMO

Ive built over 40 guitars in my life, I quit 10 years ago ,acoustics ,only electrics now. I sell an average of 1 a week.

- I can tell by looking yours will be great-It looks a hell of a lot better than my first one built from a pallet back in 81!
Good luck. thanks It will be interesting to see.

SoupBone

 

[Antz_Marchin]

Thanks very much Soup, again I really appreciate it. I understand what you mean with the braces now. I think (hope) I have the concepts well enough to make the first guitar "good" but from what I have already figured out where to improve, I think my learning curve here will be very steep and the the second guitar will be great. I already have the wood and oooohhh, it's sweet. :food-smiley-004: Thanks again. -BJ

 

[Lab123]

Antz....I'm wondering how much progress is being made with the new build....Looks good so far....The first acoustic is a vast learning experience. If you do your homework and ask a lot of guestions you'll do fine...
My X braces are 3/4" high and 3/8" wide and tapered. (Pyramid Shape).The upper bout is scalloped down to about 1/8" and the lower bout is tapered down paper thin. My tone bars are 1/4" wide and tapered down paper thin on the end. the traverse brace ends are scalloped at the ends....I find that scalloping helps loosen up a stiff top when you tap tune....just my opinion......Lab

 

[ronmac]

For your next build you may want to consider "T" bracing, as done by Simon Fay I just received one of his guitars and it is very lively.

You may also want to investigate some of Mario Proulx's work. He uses a layer of carbon fiber sandwiched between two spruce strips to construct his braces. They are amazingly stiff and light.

 

[Lab123]

Ronmac.....First time that I've seen T bracing....Interesting concept....Might give that one a try....Lab

 

[WarrenG]

T-bracing "looks" interesting. Structurally, there doesn't seem to be any advantage over "pyramiding" the brace stock. They may be even a little heavier...

BTW, what compelled you drill holes in the tonebars? Kevin Ryan? Interesting concept, however the strength is seriously compromised. i.e. the brace is effectively only strong between the soundboard and the hole's edge. The height of the brace is no longer consequential as the fibers are disconnected. These are not like homogeneous steel beams (probably the inspiration).

Keep in mind, the strength issue is logarithmic: shaving the height of a brace by 1/4 reduces its strength by 1/2 over that point.