Elie Riachi
Oud Junkie
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Registered: 4-9-2004
Location: Kansas
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Mood: Gebran Tueni Lives For Ever, 12-12-05.
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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
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Dr. Oud
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Wave Form Resonance" & "To Mold or Not to Mold"
| Quote: | Originally posted by Elie Riachi....
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... |
1. -> The angle change over the width of the purfling is negligle and can be used out of the box. Don't get too obsessed with the angle.
2. -> There are instances where you will need to push doen on the rib at a spot opposite a high point mismatch of the rib edges. These are flexible
materials and are reacting to heat and moisture while you work them, so getting the plane exactly perfect is nearly impossible. Small adjustments of
the fit between tthe rib edges will require pushing on the rib while table sanding to knock down those high spots.
3. ->Well, Mr science, the flat sanding table will do all that calculating for you. The rib bent to the profile with the edges sanded flat on the
table will have the right dimensions. You only need to calculate the neck end (usually around 1/8 inch) and the max width at the widest point of the
bowel. The tail ends in a point. (1/2 circumferance/no of ribs (-purfling)). You can do the math if you want to. The top rib is made extra wide to
make up for discrepancies in width and fit at the neck and overall. Don't fotget that offset at the rear now....
4. -> You got this one right on.
5. -> I don't care if you tie them in a stack or not, you will still have to tweak the curve of each and every rib, count on it.
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Elie Riachi
Oud Junkie
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Registered: 4-9-2004
Location: Kansas
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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.
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Jameel
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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. |
I admire your hypotheticals and analysis, Elie. I can't tell you how many times I've built an oud from start to finish in my mind. Sometimes it hurts!
In my experience, one or two hours holding a rib blank in your hands and fitting it to a mould will teach you more than days analyzing how it might be
done. And to prove that point, I flunked high school algebra. And to make up for it in college, I skipped class and mastered the video game Mortal
Kombat and the pinball game Addams Family.
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Dr. Oud
Oud Junkie
Posts: 1370
Registered: 12-18-2002
Location: Sacramento, CA, USA
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Mood: better than before
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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.
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Peyman
Oud Junkie
Posts: 496
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Wave Form Resonance" & "To Mold or Not to Mold"
| Quote: | | 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. |
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 
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Elie Riachi
Oud Junkie
Posts: 582
Registered: 4-9-2004
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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.
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It is getting deep, better get my boots!
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Dr. Oud
Oud Junkie
Posts: 1370
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Location: Sacramento, CA, USA
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Wave Form Resonance" & "To Mold or Not to Mold"
| Quote: | | Originally posted by Peyman...Nariman built tanboors (3 string type saz) without any molds. He just bent the ribs and glued them. ..
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See! There, I told ya! There goes your "can't build an oud without a mold" rule. ..and they said it couldn't be done....
Hey Johnanthan, it looks like an oud to me, they're always filthy dirty until the final sanding step. then when you wipe on some spirits, ouila!
beauty! Welcome aboard, dude!
Oh, and Elie, you might need your waders before we're through.
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Peyman
Oud Junkie
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Jameel, what was your favorite MK character?
| Quote: |
See! There, I told ya! There goes your "can't build an oud without a mold" rule. ..and they said it couldn't be done....
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But Doc, the tanboor bowl is 2/3 the size of an oud.
Anyway, that bowl looks sweet. I think that end inlay idea is very practical too; there is a lot of potential for some great artisitic work. Good
luck.
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Dr. Oud
Oud Junkie
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Wave Form Resonance" & "To Mold or Not to Mold"
| Quote: | | Originally posted by Peyman...But Doc, the tanboor bowl is 2/3 the size of an oud. .. |
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.
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Elie Riachi
Oud Junkie
Posts: 582
Registered: 4-9-2004
Location: Kansas
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Wave Form Resonance" & "To Mold or Not to Mold"
| Quote: | Originally posted by Dr. Oud
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. |
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"....
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Dr. Oud
Oud Junkie
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Location: Sacramento, CA, USA
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Wave Form Resonance" & "To Mold or Not to Mold"
| Quote: | Originally posted by Elie Riachi...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.... |
Ok, Mr Science, I've got my waders on and I'm standing on stilts too! The problem I have with mathmatical analysis is that it assumes perfect
conditions. Even the most symmetric and smooth shaped oud is still far from perfect. If you look inside, you'll find irregularities in the inner
surface of the bowel, so the wave propagation is gonna be disrupted anyway, no? Wasn't the Tacoma bridge resonance caused by slightly out of phase
frequencies that increased the wave amplitude to the point of failure? I thought that perfect wave form propagation produces uniform waves, but
slightly out of phase frequencies are what cause resonance. huh? Like when the surf's up, the wind direction can affect the wave form drastically,
dude. So you have a happy turkey day too and don't worry, the bird flu isn't here yet - I think!
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Elie Riachi
Oud Junkie
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Wave Form Resonance" & "To Mold or Not to Mold"
Maximum energy transfer is achieved when the driving frequency matches one of the natural frequencies of the system being driven. This is resonance.
At resonance the conditions are such that the driving wave and the wave traveling through the system are completely in phase when they meet, causing
constructive interference and the system resonates. The more the waves are out of phase the sooner they will decay or die out by canceling each other
out due to the destructive interference. Check this fun site out: http://www.colorado.edu/physics/2000/microwaves/standing_wave2.html
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Elie Riachi
Oud Junkie
Posts: 582
Registered: 4-9-2004
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Wave Form Resonance" & "To Mold or Not to Mold"
Obviously in some musical instruments there is a deliberate deviation from symmetry to accommodate other features, an example would be acoustic
guitars with cutaway http://www.musiciansfriend.com/srs7/g=home/search/detail/base_pid/5...
Also the Kasha guitar, X-bracing and other types in a guitar and the sound post in violin which I understand are supposed to give the instrument a
certain desired voice.
My apologies if this is distracting from Jonathan's project which is shaping up to be a nice looking oud. Keep at it friend.
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Peyman
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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.
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Jameel
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Neat, Peyman. Richard will be thrilled to see these pics.
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Dr. Oud
Oud Junkie
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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. )
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coyootie
Oud Addict
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it's great to see all this generosity and collegiality among builders!
my 2 cents: hot hide glue is amazing stuff and if you get familiar enough with its idiosyncracies, there's virtually nothing else you'll ever want to
do! BUT:
my friend Dan Hachez, a master lute and string bass maker, has started using Lee Valley's fish glue in a bottle.It has a much longer open time than
hot glue and pretty much does all the magic stuff of hot glue:tremendously strong, totally reversible with a little heat or rarely steam.
Many of the expert Renaissance lute makers claim that the more crystalline structure of hide glue transmits vibration better than synthetic resiny
glues- I feel instinctively this is true, but it's all that was or is ever used on violins!
I've never tried building in the air but it certainly works fine for many builders that never use molds.
God Jameel, those marquetries you're making are beautiful. I saw your patient and painstaking site from your first oud and was mucho impressed with
your eye and craftsmanship! you don't need any encouragement or flattery, you're already there! best regados to all, alan in santa fe
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Mike
Super Administrator
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I was kindly asked (not by Jonathan) out of respect for Jonathan's oud project thread to move some of the posts from JV's thread to a new thread. So
carry on gentlemen. Great stuff here.
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Jonathan
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Didn't bother me. But, thanks for the thought.
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Dr. Oud
Oud Junkie
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Hey that is a fun site. I especially like what happens when I drag the slider to the left - it looks like the sound my wife makes when I tried to cure
glue by putting an oud part in the microwave!
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