Wave Form Resonance" & "To Mold or Not to Mold"

I haven't built my first oud yet but I am very close (time permitting.) so here is what I think for what its worth (and I have been doing a lot of thinking, what I do before I start any project and that is why it takes me so long to get started on any thing):

1. Purfling will change the mating angle between the ribs, the thicker the purfling the larger the mismatch. The solution might be to sand the rib's edge flat to mating angle, glue purfling then follow the sanding procedure for rib fitting but sanding the glued purfling.

2. I have read this so many times and makes a lot of sense to pay important attention "NOT" to push down on the rib while sanding the edges. The reason is you do not want to deform the rib and sand an edge which conforms to the deformed rib shape, the rib will bounce back to restore original shape but the edge will be stuck with a mating plane which conforms to the deformed shape.

3. It is better IMO to bend ribs, then cut the shape (like Jameel did.) I have started work on paper to build my first oud (will post something once I generate some saw dust) and the shape of the ribs can be calculated with the following trig formula which I derived: w= 2(h+t)tan(180°/number of ribs).
Where,

w: is the width of each rib except for the 2 top ones, changes down the length of the rib.

h: is the height from center line to curve of back profile taken at different points at on the center line; I plan to go in increments of 1 inch;

t: is the bending rib thickness;

CAD and a spread sheet such as MS Excel would be handy in doing this. I am using TurboCAD (more details to be posted in a separate project thread.)

4. I think the most important two marks would be one on the center of the tail block and one on the center of the neck block. The respective ends of the longitudinal center-line of the center rib must line up with each of these marks when the rib is put in place. This must happen, as Jameel noted, without any twisting of the rib to fit it, otherwise it must be re-bent and the edges re-sanded.

5. I do not like the idea of tying the ribs togother in stack after bending because I am affraid that the outer ones will get spread apart and may no longer have the same profile as the original.

Like I said take this for what its worth coming from someone who has not built an oud yet but has been exercising the old noodle.

Don't give up, with people like Doc O, Jameel, Dincer and other wonderfull experienced builders helping with their experience and knowledge we may ultimately build a Nahat or a Manolis or whatever your holy grail is!

Regards,
Elie

Wave Form Resonance" & "To Mold or Not to Mold"

Wave Form Resonance" & "To Mold or Not to Mold"

Well Doc,

Re 1: What about the compounding effect of some 23 seams?

Re 2: Must be careful not to twist the rib while sanding high spots.

Re 3: I do not see that the sanding table will do all, an extreme example is if you start with a rib blank made from a rectangular piece (not cut to shape), you can sand the edges on table all day and you will only make it a narrower bent rectangle, no?
The closer the rib is to the desired shape before sanding the more accurate the sanding will be and the better the fit. The sanding table gives the average profile based on the rough cut edge, so one would want the rough cut edge of rib to be as close as possible to the correct fitting profile, think about it.

My apologies if I am sounding argumentative against the practical wisdom of the great Doc, but will always pursue knowledge and improvement.

Wave Form Resonance" & "To Mold or Not to Mold"

Quote:

Originally posted by Elie Riachi Well Doc, Re 1: What about the compounding effect of some 23 seams? Re 2: Must be careful not to twist the rib while sanding high spots. Re 3: I do not see that the sanding table will do all, an extreme example is if you start with a rib blank made from a rectangular piece (not cut to shape), you can sand the edges on table all day and you will only make it a narrower bent rectangle, no? The closer the rib is to the desired shape before sanding the more accurate the sanding will be and the better the fit. The sanding table gives the average profile based on the rough cut edge, so one would want the rough cut edge of rib to be as close as possible to the correct fitting profile, think about it. My apologies if I am sounding argumentative against the practical wisdom of the great Doc, but will always pursue knowledge and improvement.

Wave Form Resonance" & "To Mold or Not to Mold"

Quote:

Originally posted by Elie Riachi Well Doc, Re 1: What about the compounding effect of some 23 seams? Re 2: Must be careful not to twist the rib while sanding high spots. Re 3: I do not see that the sanding table will do all, an extreme example is if you start with a rib blank made from a rectangular piece (not cut to shape), you can sand the edges on table all day and you will only make it a narrower bent rectangle, no? The closer the rib is to the desired shape before sanding the more accurate the sanding will be and the better the fit. The sanding table gives the average profile based on the rough cut edge, so one would want the rough cut edge of rib to be as close as possible to the correct fitting profile, think about it. My apologies if I am sounding argumentative against the practical wisdom of the great Doc, but will always pursue knowledge and improvement.

RE RE 1. The angle doesn't compound if each rib edge is sanded on the table. I thought we were talking about the angle on the sides of the purfling? Across the very narrow width of the purfling, the angle is so near parallel as to not matter. If you're talking about the width added by purfling, by all means, the width of all the purfling must be subtracted from the rib width.

RE RE 2. Well, yes, I don't mean you need to put your full weight on the rib edge. This is a matter of woodworking technique, not absolute do or don't do it.

RE RE 3. Believe me I have thought about this plenty, my friend. of course your extreme example is a little off the hook. I have for years rough cut the ribs while they were flat, leaving about 1/8 inch margin for adjustments and making a few extra in case I over sand or broke them bending, and I still do (but don't tell anyone-it's our dirty little secret). I have bent them square but had trouble controlling the bandsaw feed cutting them to the rough outline after they were bent. The table is for fine tuning the edge, not rough shaping, and doesn't necessarily follow tthe rought cut edge. You can sand spots by pushing (lightly and with finesse) on the edge opposite the aforementioned high spot. In point of fact, it's pretty difficult to sand the rib with equal pressure all along the entire edge, think about that. You can use the upside down plane to rough out the shape, indeed that's a common method in many Mid-east shops since I have not seen many bandsaws in the workshop pics. Arafati (my favorite builder besides myself) has only a long plane, a hand saw, a short plane, a few flat chisels and a drill motor. And he makes ouds as clean and precise as anything I've ever seen. He doesn't use a sanding table either, but he must be really good with the planes.

Hey, I like a good argument, it is a very constructive learning method. No need to bow down either, a little groveling now and then will do fine.

Wave Form Resonance" & "To Mold or Not to Mold"

Doc, I was just thinking about this right when you posted! Amongst other tools used in Iran to shape ribs: Large kitchen knives, and bowl carver's adze. Nariman built tanboors (3 string type saz) without any molds. He just bent the ribs and glued them.
Just keep at it Jonathan, that bowl is looking good

Wave Form Resonance" & "To Mold or Not to Mold"

Quote:

Originally posted by Dr. Oud No need to bow down either, a little groveling now and then will do fine.

Wave Form Resonance" & "To Mold or Not to Mold"

Wave Form Resonance" & "To Mold or Not to Mold"

Yes, but size doesn't matter (at least that's what my therapist tells me). I think the problems of shape and fit are the same, anyway. I have also seen some moldless fixtures used in a Morrocan oud shop and there is evidence by Robert Lundberg that some European luthiers made lutes without molds. Guitars were made by many Spanish masters without molds as well. While the mold makes the shape more consistant and symmetrical, the old masters didn't seem to be so obsessed with perfect shape. My wood supplier, Miles Gilmer has traveled the world searching for exotic woods and visits every museum he can during his trips. He has noted the lack of symmetry in many of the museum pieces, and believes (as I do) that the aspect of perfect shape has been influenced by our machine made environment. It certainly has no affect on the sound of an instrument.

Wave Form Resonance" & "To Mold or Not to Mold"

Okay Doc,
I got my waders. I am having a problem reasoning with certainty that symmetry and perfect shape have no effects on the sound of an instrument. Wave (sound) phenomenon such as resonance, standing waves and natural frequencies seem to be very much affected by symmetry an example would be the way bridges are designed to avoid the Tacoma bridge incident. Sometimes it is desirable to avoid symmetry and perfect shapes and other time it is the opposite. I am thinking that symmetry and perfect shape would favor resonance conditions. But I think I see what you are saying that in the case of the oud the asymmetry and the imperfection in the shape are so small that their effect on the sound is negligible.

Happy turkey day to the members in the US, and remember "you are what you eat"....

Wave Form Resonance" & "To Mold or Not to Mold"

Wave Form Resonance" & "To Mold or Not to Mold"

Wave Form Resonance" & "To Mold or Not to Mold"

Wave Form Resonance" & "To Mold or Not to Mold"

Inside a morrocan luthier:
http://www.luth.org/downloads/AL82extra.htm
Scroll down to bottom to see the oud maker. I don't see any molds.

Symmetrical instruments are asthetically pleasing. Actually to our perception, anything symmetrical seems to indicate beauty, a fact discovered and reiterated by the renaissance artists.
Tomorow, I'll plan to take a look at some aesthetically pleasing turkey (I bought the most symmetrical) and will enjoy it with some ouzo I discovered in a local liquor store. Then I'll take a nice nap as I try to stay awake to watch some football.

Wave Form Resonance" & "To Mold or Not to Mold"

That's exactly the article I was referring to, you beat me to it. I see a fixture very similar to the one I use in the book. Should I sue those guys for infringing on my design? How deep do you think their pockets are? What's a lawyer cost in Morocco anyway? Oh never mind, It's probably not worth it.

An interesting thing about this article was the comment that the author made about buying a "soprano" oud. I told him there are no "soprano" ouds - what he bought is a downsized oud made for little boys and fat ladies.)