theodoropoulos - 7-2-2016 at 09:00 PM
i make my soundboards flat.But i have seen and read many luthiers make them like classic cuitars,with slight curves..
I dont know which is the normal for a traditional oud.
could someone tell me??
bulerias1981 - 7-8-2016 at 08:28 PM
Classical guitars are built slightly convex, some ouds are built concave. Both are stronger and help against deflection from years of string tension.
On the classical guitar it's function is to be able to go thinner on the soundboard. It's not really the same on the oud, the goal is not to be able
to thin out the soundboard more, but just as a preventative measure to prolong structural integrity of the soundboard.
mavrothis - 7-9-2016 at 05:29 AM
Manol ouds were typically convex as well, as far as I know.
bulerias1981 - 7-9-2016 at 07:44 PM
Yes, and most Turkish ouds are made that way. Not many Arab ouds. I make mainly Arabic ouds, and I build a convex curvature into the soundboard for
longevity.
theodoropoulos - 7-9-2016 at 10:58 PM
thank you guys!!!
Could you please inform me where is the highest point if i make my soundboad convex??
under the bridge??
Dr. Oud - 7-17-2016 at 08:03 AM
The bridge area of the face must be in alignment with the fingerboard. The lowest point of a concave face is the brace below the eyun (small
soundhole) or the 4th brace from the tail, at the widest part of the face. This is around 4-5mm (3/16 - 1/4inch) and is achieved by either trimming
the top edges of the body or shaping the braces in a concave curve.
The braces behind and in front of the bridge must be aligned with the neck and tail block surfaces so that the bridge is aligned with the fingerboard.
The purpose of the concave face is to prevent distortion of the face as a result of the twisting of the face around the bridge. This results in a "S"
shape distortion with a hump at the 4th and 5th braces, just below the shams (large sound hole). This hump can interfere with the strings vibration
amplitude, causing a loss in volume. Lowering the 3rd and 4th braces positions the face below the plane of the fingerboard-bridge, preventing the "S"
shape distortion. The 3rd, 5th and 6th braces are surfaces are located in a gradual arc so that the 6th brace at the top of the shams is aligned again
with the fingerboard.
Another solution is to use a long fingerboard on top of the face. This has the same affect as the concave face.
theodoropoulos - 7-18-2016 at 02:37 AM
Dr Oud thank you for your detailed description!!
As i understand from your description i find that the concave face makes sense in order to prevent all things you mention.
But why other luthiers prefer convex face?I find that itwould help ths "S'' shape of the top,so it would be wrong...
I think that in bridges that press the face from string tension (bouzouki,mandolin etc) the convex face helps the distortion and in instruments with
the strings beginning from bridge(classic guitar,oud,etc) need concave...
Thank you for your time!!
Dr. Oud - 7-18-2016 at 07:30 AM
A floating bridge instrument (mandolin, violin, arch top guitar, Bashir oud) puts a compression force on the face unlike the glued on fixed bridge.
The arch can counter this compression and/or it is used to align the bridge with the fingerboard. The resulting onvex shape allows more freedom for
strumming the strings as it lowers the sides of the face. The arch is also a better shape to counter the string pressure, even with a concave face.
The sides of the the face are then lowered by trimming down the top edge of the body more than the concave dimension.