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suz_i_dil
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You're most welcome.
I understood " bois dessus" as quarter sawn. They don't precise for the deformation, but I guess it's like this, more deformation in the center.
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jdowning
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If the translation is 'quarter sawn' then this is useful information as it supports one of the conclusions of the phase1 bending tests - although as
far as I know 16th C ribs (at least of lutes) were usually cut on the quarter as the wood cut this way is more stable (i.e. less prone to movement due
to humidity fluctuations).
Out of curiosity, I examined the end grain cell structure of three of the samples from the phase1 tests but could not detect any obvious cell
deformation between the centre and the edges of each sample (under about 10X magnification). However, to properly check this, a bent sample would need
to be examined, perhaps at greater magnification, before and after bending. So, I am not sure exactly what the investigators in Paris may have
observed that led them to the conclusion that the fluting was formed by exerting pressure on the rib blank using a two part mold (if that is the type
of mold that they meant).
Examination of the scorch marks noted by Joel Dugot might provide a further clue - by trying to determine how they were made and by what kind of tool.
Is the scorching uniform or does it occur in localised areas?
Perhaps the uniform high temperature, necessary for successful bending, may have been originally achieved by simply laying the rib blank, on a grill,
over a bed of charcoal until scorching temperature (about 400 C?) was reached (i.e. like 'barbecuing' a steak - marinated or not!). The heated blank
may then have been quickly clamped to a suitable mold (which could be pre-heated to avoid chilling the blank too quickly). A two part mold - where a
heated blank is 'sandwiched' in between the two halves - would be an obvious possibility - perhaps with the upper part of the mold being made in
articulated sections in order to apply a less abrupt, gradual bending load.
This procedure may well have some potential so will be tested and the results posted later.
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jdowning
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An update.
While searching for some pieces of Persian boxwood in my stock of woods, I came across the Brazilian rosewood that I was looking for last November
but was unable to find. So here - for information - is a better image of the cell structure than the one posted 0n 11-20-2008. The scratches running
across the image were made by the knife blade used to prepare the section - my methods are still pretty rough and ready!.
On another more recent thread Peyman noted that an early Persian text recommended soaking instrument (carved) bowl blanks in milk to make the wood
easier to carve. Moistening wood with water is a technique used by wood carvers to soften wood prior to carving so milk presumably is a better
solution than just plain water - although milk is mostly comprised of water. Perhaps the solids or fats in the milk make a difference? No mention of
the animal the milk comes from so perhaps that is not important.
Milk as a potential marinating fluid will, therefore, be added to the list for future testing. Thanks Peyman.
The next phase of testing will be to bend a full sized fluted rib in preparation for making a replica of the Diaz guitar. I know now that this can
easily be accomplished using Black Walnut so will run some tests on the more difficult to bend Indian Rosewood. As is apparent, from previous trials,
a brief marinating period in Ammonia solution (or Ammonia/Methanol) may provide some marginal advantage in softening Indian Rosewood but use of higher
temperatures (100 C to 400C) will be more significant. Also previous trials indicate that the rib blanks should be 'cut on the quarter' with
longitudinal grain 'run out' to reduce the tendency to split in the longitudinal direction. The grain run out introduces a potential longitudinal
structural weakness that should, however, be more than compensated for by the stiffening effect of the rib fluting.
Use of higher bending temperatures will introduce a handling difficulty so the mold will have to be designed to facilitate a speedy, two stage,
bending procedure.
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WFBustard
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HI JD
I am currently finishing up a similar sized instrument based on the so-called "Dias guitar"and would be interested in your results.
This is my first using the double-bent ribs. I used flamed western maple, easy to bend.
I hope construct a copy closer to the original next time when I eliminate some of my technical problems of assembly. At which time I hope to try
cocobolo or possibly "kingwood"(I dont know what kingwood is but was at the wood store, labled that way...
any updates on the sucess of your Dias project?
thanks
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jdowning
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I do not plan to start building a version of the Dias guitar until I have completed the bending trials for fluting ribs as reported on this thread.
Once I start the guitar project, progress will likely be posted on the forum - as a new topic and thread - for the information of all who might be
interested.
The original Dias guitar is made from the true rosewood variety "Dalbergia cearensis" otherwise commonly known as 'king wood'. Best to always use the
botanical designation to avoid confusion.
BTW, There is no question about who made the guitar which is in the instrument collection of the Royal College of Music, London, England. A hand
written label inside carries the legend "BELCHIOR DIAS A FEZ EM LXa NOMES DEZro 1581". As well, there is an engraved panel on the front face of the
pegbox which says "BCHIOR DIAS LXA" (LXA is Lisbon, Portugal). So the guitar was made by Belchior Dias in 1581.
A set of full size drawings of the instrument with detailed notes - drawn by Stephen Barber - can be purchased from the College.
Why don't you post images of your project to date - as a separate topic on the Forum - giving details of your methods for bending the ribs, assembly
of the body, problems encountered and how you overcame them etc. etc. I am sure it would be of interest to many.
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WFBustard
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Thanks for the reply.
Yes used Barbers plan from RCM. Its not an Oud so I didnt think this forum would be appropriate.
This first one is more of a working model to get the bugs out. The plan I made from the drawings had mistakes such as depth of sides and waist issues
which caused me to flatten the "dome" enough to spread some of the rib joints. You can see that the ribs are indeed quite deep initially on each end
but flatten out in the middle. I may fix the joints with purfling however I hope to keep the next to a minimum.
If you really think some may be interested--I will be starting another next fall at which time I will start a thread since you think its okay and this
forum would like to see it.
I have decided to work on my Oud design for a little while although I am experimenting with the fluted ribs for it as well..perhaps a integration of
the dias and oud
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jdowning
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I was only suggesting that you provide information about your experiences with the instrument that you are currently finishing - not to start a new
project. No matter that your work in hand is a development model and there are some errors in the construction - it is the details of your rib bending
procedure and the fitting of the ribs (to each other) that would be of primary interest. A lot may also be learned by your analysis of any failures
and difficulties encountered - for example you might consider providing information about how you plan to solve the problem of the ribs flattening out
in the middle next time around?
Some images of the construction detail might also be of interest.
The final stage of my bending trials - subject of this thread - as previously indicated, will be to try to bend fluted oud ribs using techniques that
are still undergoing development experimentally. This objective - which will be more difficult to achieve than the bending of relatively shallow
curved fluted guitar/vihuela ribs - if successful, will likely be of more interest to modern oud makers.
The procedure for precisely jointing the fluted oud ribs is also likely to be a challenge - but first things first!
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WFBustard
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Time is the primary factor.
I am positive that bending good fluted ribs for an Oud is possible.
I look forward to Seeing your work so far, Im sure you will make a great instrument.
Good Luck.
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jdowning
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Why are you so confident that bending good fluted ribs for an oud is possible?
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WFBustard
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I managed to make parallell"Ribs" 360degres as a test for some drums I am designing so I figure if that can be done, well most anything can. It all
has to with wood thickness.
Every species has different stretching characteristics as Im sure you are aware. Testing and testing untill that thickness is determined.
My Maple which I am presently involved with, for example, the optimum is 1.2mm that is not to say that all maple is the same.
2mm may be difficult or even impossible I dont know, but there is no law saying that an Ouds ribs can be thinner.
You have to find out for each different stock.
At least thats what Ive discovered.
Kinda like like frying baloney of different thicknesses its all gonna curl different. :-)
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jdowning
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Not sure that I understand what 360 degree parallel drum ribs look like. Could you post an image of the ribs you have made for information?
Thanks
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WFBustard
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360 degree I mean a circle, with the rib side parrallel, not tapered like an Oud.
My idea was to stack them into a cylinder to make a drum, which I will eventually
Decided to learn to play an Oud a wee bit before I build one.
So I cancelled that project for awhile.
But heres some ribs...I could use for an Oud.
I had them left from the Dias, they are rough 1.2mm thick.
I beleive I can get more bending out of them by reworking. Hand bending over a hot pipe takes practice.
For this the wood must be completely dry. The rib is held under the tap just until it is covered with water, then laid flat for severel minutes until
it starts to bend on its own.
If it doesnt do this right away it may be placed under a heat lamp or...wht I use...the sun.
After this is seen it is merely helped on its way with heat.
In order to do this only certain cuts can be used easily.
The thickness to use will vary amongst the different woods and even different stock of the same species but not too much.
Around 1.2 is a good ballpark.
For example honduras would possibley have to be 1.1.
Using too much water or soaking the wood could cause it to crack.
The use of a steambox I have not tried.
I do not use a mold but sometimes "pinch" shape with a clamp for some of the more stubborn stuff.
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jdowning
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Thank you for posting the images and description of your bending method AFBustard. Interesting that we are in agreement over the wood thickness (or
rather thinness) to be used.
You do not explain what you mean by "certain cuts" that you indicate are necessary for success?
When I first opened this thread in November 2008, I mentioned that - when bending thin lute ribs (lute ribs are generally thin, - under 1.5 mm) - a
natural fluting occurs due to the balancing of the longitudinal and transverse stresses in the rib. This natural curvature across the width of a hot
bent rib may be slight or quite pronounced, dependant upon a number of factors.
The attached image is an example of this natural fluting in a rib blank hot bent (dry) in the conventional way on a propane heated bending iron to a
lute rib profile. The rib material is figured maple, quarter sawn. No clamps or other devices were used to locally enhance the fluting diameter.
For comparison, the second image is of Walnut test sample #7, previously mentioned on this thread, - after marinating and forming on a mold to the
longitudinal curvature and fluting diameter of the Dias guitar rib. After several months, this sample is stable having maintained its longitudinal
curve and a uniform fluting diameter along its entire length.
The final objective of the experiments of this thread, is to try to produce oud ribs that have at least the same fluting curvature as the Dias guitar
ribs - not the more shallow fluting that is the natural result of hot bending. Not an easy objective I would reckon. To be of practical use in making
an oud bowl, the formed ribs will have to be precise and consistent in their geometry so will need to be formed using some kind of mold rather than
being made 'free hand'.
Precise jointing of these fluted, 'extreme' curvature oud ribs will likely be a challenge in itself for the luthier.
Nobody said it was going to be easy!
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WFBustard
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It is a curious thing this concept, Ive often wondered how BD ever came up with it.
I will certainly keep experimenting.
Just for kicks last night I tried hot bending a 2mm peices to the usual diametre and it work worked okay but was more difficult, time consuming and I
had more incidence of failure.
They were 6 cm wide and as you suggest in a previous post this does add to the difficulty
As far as the different cuts I am too ignorant to tell the difference, I just know some work and others dont or rather are more difficult and subject
to failure more often than not.
To be honest I commend you on your persistance of this noteworthy goal and wish you success in attaining it.
And now you have given me another one.:-))
Are there actually any extant instruments with this concept, giving its dimensions? I measuring up 35mm to night to see how small that is.
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jdowning
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I do not know of any surviving ouds or lutes - ancient or modern - that have hot bent fluted ribs of the kind under examination. However, the topic of
carved v.s. bent ribs was discussed at the outset on this thread.
Historically, this kind of bent - rather than carved - rib survives to my knowledge in only two, vaulted back, 16th C instruments - the Dias guitar in
London and a vihuela (?) cat. E.0748 in the Cite de la Musique, Paris - both possibly from the hand or workshop of the same luthier.
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WFBustard
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It is a very challanging concept to "... try to produce oud ribs that have at least the same fluting curvature as the Dias guitar ribs ..."
I think that if one were to persist on the pipe it might be possible for most of the length of the rib, but the very bottom where it turns radically
it flattens.
Good luck with the trials-
cheers
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jdowning
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With respect AFBustard, if you wish to carry out a series of experiments to investigate the possibilities of forming fluted oud ribs then I would
appreciate it if you would start a new topic on the Forum to report on details of your experiments, methods and the results. This will avoid confusing
the sequence of experiments and objectives that I have already planned for this thread. Thank you.
I for one look forward to following your progress. Good luck!
The next planned experimental step on this thread will be to form full size fluted ribs of the Dias guitar geometry - as well as to proceed further in
my investigation of the effect of marinating fluids on wood samples. Only then do I plan to apply the combined results of these tests to attempt the
more challenging (perhaps impossible) task of producing heavily fluted oud ribs to a consistent, repeatable geometry.
As previously indicated, it could take quite some time for me to reach that stage. In the meantime, if other investigators are able to - independently
- demonstrate a successful solution to bending fluted oud ribs then there may be no further need for me to proceed with my planned trials in that
direction.
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jdowning
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AFBustard why do you persist in editing your responses shortly after posting them? In your last post you first indicated that you were about to
conduct some experiments over the next week with some bending tests of your own and I have responded accordingly. Now that part of your response has
been deleted! You also asked advice on oud rib curvature - also now deleted. Very confusing for everyone.
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WFBustard
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Well I was hoping you hadnt read it yet. After readinhg it through I figured it was apparant I was posting too much.
I didnt want to hijack your thread.
I guess it didnt matter anyways since you didnt answer and requested I dont post anymore so alls well that ends well.
tootaloo
sorry for any confusion.
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jdowning
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This might be a good time to review the Dias rib geometry prior to constructing the experimental rib mold.
The RCM drawings are on paper - drawn to an accuracy of
0.5 mm. Each drawing has a reference scale of 1000mm along the length of the paper but not across. Paper expands and contracts along the 'grain' with
changing humidity so, today, the paper has expanded to 1002.5 mm. This is such a small dimensional change that it can be ignored. Note, however, that
the original instrument has suffered some distortion over time as represented by the drawing.
The drawings show three cross sections of the ribs at the top bout, sound hole centre and lower bout locations. From this it can be seen that the five
fluted ribs not only all taper towards the neck but also reduce in the radius of their fluting. This radius reduction is consistent along the length
of each rib - that is, the ribs do not flatten out in the centre.
The image shows a sketch, to scale, of the central rib measured at the bottom bout (with ivory purfling between each rib). The central rib has a
longitudinal curve of 8370 mm (34 inches) and a length - measured along the length of the curve - of 365 mm (14.4 inches). The rib width W1 is about
30 mm at the lower bout and about 25 mm at the upper bout. The inner radius of the fluting at the lower bout is about 18 mm reducing to 16.5 mm at the
upper bout.
In contrast, the outer ribs of the group of five have a fluting radius of about 18 mm at the lower bout reducing to 11 mm at the upper.
So the ribs should be formed on cone shaped mold(s) or mandrel(s) in order to maintain the consistent geometry necessary for accurately constructing
the vaulted back. There will, of course, be some variations as each rib has to be individually fitted to its neighbour.
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jdowning
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For the next stage of this investigation, full sized ribs of the Dias guitar geometry will be made (or attempted to be made!). The first trial will be
to form a rib using a marinated blank heated to 100 C. This will first be tried with a Walnut blank followed by the more difficult to bend Indian
rosewood at higher temperatures using a heated iron.
The first step is to make a mold to the geometry of the central Dias rib using the dimensions taken the RCM drawings.
The mold is made from Ash wood.
The longitudinal curve of the mold has been accurately transferred from the drawings using draughting curves. The curve of the mold has been cut to a
radius of 30 inches (760 mm) ,rather than the original 32 inches (internal radius), to allow for some anticipated slight 'spring back' of the formed
blank when released from the mold.
The mold is tapered from front to back to conform to the original guitar rib geometry.
At this point the mold has been roughly contoured using a half rounding bit in a router to remove most of the waste. The final fluting profile will be
achieved by hand using files etc. with card templates to check the fluting radius at the three positions given by the museum drawings.
A wooden mold will be satisfactory for the higher bending temperatures using this procedure.
Note that the fluted ribs of the so called Chambure vihuela in Paris (also made by Dias?) have scorch marks on the surfaces of the ribs (i.e. the
convex surfaces facing inside the instrument).
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fledelis
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I wonder if this project is abandoned? I wouldn't be surprised that it is, with the other two that you are carrying on at the moment ...
By the way, I was just reading through Joel Dugot's description of the E.0748 (fluted back) vihuela in the Cite de la Musique and I could not see any
mentioning that the back ribs have (as you put it) any scorch marks from the inside. It's the sides(!) of the instrument that have such marks which
is, in a way, hardly surprising - hot iron method is still the mosty preferred way of bending flat pieces of wood today.
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jdowning
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Thanks for your interest fledelis. No, the project is not abandoned as I plan to be building a fluted back vihuela as one of my next projects - time
and life permitting!
It is quite likely that I have mis-translated Joel Dugot's description of the E.0748 vihuela as my grasp of the French language was never fluent and
is now very much out of practice.
So, if there are no scorch marks in evidence on the insides of the fluted ribs this, interestingly, opens up the question about how the ribs were
formed.
More food for thought!
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jdowning
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Looking again at Joel Dugot's paper "Un nouvel exemplaire de vihuela au musee de la musique?" I have to agree that it is not clearly stated that the
inside surfaces of the fluted ribs have traces of burn marks.
What Dugot says - in the context of 'l'eclisse' (the modern technical term for sides - of a guitar) - is that "La mise en form a ete realise par
pliage a chaud. On note nombreuses traces de brulure du bois sur les faces internes". That is "the shape (or form) of the instrument has been
accomplished by hot bending. One notes numerous scorch marks on the internal faces of the wood".
Further on Dugot states that "Le fond est constitue de sept cotes debitees dans une pieces unique, du meme bois que les eclisses ..... Chacune de ces
cotes est formee en gouttiere ...". That is " the back is comprised of seven ribs cut from the same wood as the sides. ...... Each rib is fluted (i.e
formed like a gutter)".
I guess that my confusion in translation comes from the early meaning of
'l'eclisse' which means a lute rib (ref. Marin Mersenne "Harmonie Universelle", Paris, 1636).
So if Dugot's comment on the internal burn marks is unambiguous and applies only to the sides and not the ribs, then this may be important
information.
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fledelis
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Well, Joel Dugot's description is totally unambiguous (so no "ifs" here I'm afraid), according to which the internal burn marks appear ONLY on the
sides (La couronne d’éclisses) and have nothing to do with the back ribs.
Anyway, stretching it a bit further ... it would be rather unusual (if not to say counterintuitive) to expect some kind of hot iron / burn marks to be
found on the inside of a fluted rib shape but rather on the outside. Just a thought ...
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