New Luthier Tips du Jour video - Top Bracing

Robbie O'Brien · Post by **Robbie O'Brien** » Tue Oct 21, 2008 2:25 am

The latest Luthier Tips du Jour video is on the air. The topic is acoustic guitar top bracing and my glueing sequence.
Comments and discussion are welcome.
Enjoy!

youtu.be/

kiwigeo · Post by **kiwigeo** » Tue Oct 21, 2008 1:33 pm

Good video Robbie. Nice uncomplicated method and everything clearly explained.

I havent preshaped my braces prior to glue up before now but will bhe giving it a go on the next build.

Cheers and thanks for posting

Martin

hilo_kawika · Post by **hilo_kawika** » Tue Oct 21, 2008 4:09 pm

The construction sequence is clear and uncomplicated - another job well done, Robbie.

But if you're as confused as I am about the shapes of the braces and the reasons for their shapes, here's a very nice Oz link to some information which might form the basis for a number of future discussions on the forum:

http://www.phys.unsw.edu.au/music/guita ... ladni.html

David

Lillian · Post by **Lillian** » Tue Oct 21, 2008 10:18 pm

Thank you Robbie. These tips are wonderful. I really appreciate you taking the time to do these and will be letting LMI know as well.

Robbie O'Brien · Post by **Robbie O'Brien** » Wed Oct 22, 2008 12:05 am

Lillian wrote:Thank you Robbie. These tips are wonderful. I really appreciate you taking the time to do these and will be letting LMI know as well.

Thank you very much Lilian! I am sure LMI would appreciate the feedback as well.

Kim · Post by **Kim** » Wed Oct 22, 2008 12:39 am

Yes Robbie, I am with Lillian 100%.

The time and effort you put into these submissions is very much appreciated, not by those of us on the forums alone who make a point of telling you so, but by many, many people entering this craft who, whilst remaining voiceless behind the anonymity of youtube, would be no less inspired.

I am certain that Chris and Co of LMI are truly counting their blessings for your affiliation with their company rather than their opposition.

Cheers and many thanks.

Kim

Mark McLean · Post by **Mark McLean** » Wed Oct 22, 2008 7:00 am

Another great lesson Robbie. The positioning of the nodes and the general measurements are very useful information. I wasn't sure what to do if I didn't have an explicit set of plans to follow - but this gives me a good rationale for planning my own bracing layout in the future.

BTW, I just posted some photos of my first guitar build, done with an LMI kit and your DVD as guidance. It works!

many thanks

Mark

Allen · Post by **Allen** » Wed Oct 22, 2008 7:14 am

Robbie, do you use scalloped braces on all your instruments?

I've only ever gone with parabolic bracing, as I couldn't come up with a rational for where to place the peaks on the braces. Your video answers that question though. Thanks.

kiwigeo · Post by **kiwigeo** » Wed Oct 22, 2008 8:50 am

Allen,

Ive always divided my braces into halves or thirds to determine scallop peak locations. This was how I was taught to do it by Paddy Burgin and Dave Freeman.

sebastiaan56 · Post by **sebastiaan56** » Wed Oct 22, 2008 9:13 am

Another classic Robbie,

Thanks

kiwigeo · Post by **kiwigeo** » Wed Oct 22, 2008 10:33 am

Robbie,

This probably a stupid question and maybe I dont understand something but I notice in the video the bottom of the braces are being profiled by rubbing the brace lengthways along the central area of the dished form. This would be ok for a brace that is going in at the top of the 30' arch on the top but for UTB's, tone bars, finger braces etc surely the arch on the guitar top where they sit is not 30'.

Up to now Ive marked out brace locations in pencil on a sand paper lined dish and then shaped braces by placing the brace on the appropriate pencil line and then rubbing it along imaginery axis of top.

Dominic · Post by **Dominic** » Wed Oct 22, 2008 9:59 pm

Martin, this one seems to come up every so often. Thankfully its answer is in maths. The radius anywhere in a 30ft radius dish is 30ft. It does not change. What you are thinking by keeping your braces vertical as you move away from centre is effectively changing the angle they meet the top as you move away from the centre. If you glue all the braces perpendicular to the top or back at every position (and this also implies keeping your quarter sawn brace wood at its most effective angle, 90 degrees to the top) it does not matter where you sand your braces.

Imagine you are in big beach ball 60 ft high (30ft radius). If you imagine a 500mm circle on the ground you will have the shape of your dish. If you stand there you are at 90 degrees to the floor. Just like a good quarter sawn brace but with a shiny noggin.
If you walked up the wall you would get to the point where you were parallel with the floor (now the wall). More like a flat sawn brace. This is what you are effectively doing to your braces if you sand them pointing straight up at the edge of your dish. Granted it is only marginal and you are likely not to notice. But there is no point going to all the trouble to effectively turn your perfectly quarter sawn brace wood ever so slightly off perfectly quartered. Just do em in the middle.
Cheers
Dom

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New Luthier Tips du Jour video - Top Bracing

New Luthier Tips du Jour video - Top Bracing

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