SamirCanada
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new neck attachement method
I started experimenting with new ways to attach neck joint. Which can be difficult to get right with the various angles involved.
Please see some of the pictures attached. I am incorporating heavy duty bolts typically used in the construction of workbenches to secure the neck at
the correct angle. It will also be glued in place securely.
the brass nut will be epoxied in place and will be covered by the fingerboard, I have also pondered making the brass part to be exposed in the back of
the neck but I didn't want to interfere with the playability.
I have a few more ideas on how to enhance this neck attachment like adding 2 wooden or carbon fiber splints on each side of the bolt and into the neck
block to firmly secure the joint but I have yet to do these.
I am not sure yet if it will be necessary to go in and tighten the bolt from time to time. I am looking into ways to avoid loosening and I would be
open to suggestions.
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faggiuols
Oud Junkie
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Location: cagliari sardegna italia
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Samir hello
I might make a suggestion!
I have done the neck in one piece and I found myself very well.
this allows to not having to build the connection between the inner block and the neck.
After the end of the bowl I had to correct the imperfections due to the installation of the ribs, for slight misalignment of the neck lines.
I am very happy with the initial choice, perhaps a little risky!
bye
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SamirCanada
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I think 1 piece neck is great. I never made one like this but I have been thinking about it. You could even easily add a carbon fiber stiffener in the
neck like they do in violins.
in my case however, I was thinking of ways for repairs. where its too late to consider a solid neck.
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Brian Prunka
Oud Junkie
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Is it possible that the neck issues actually arise not from the neck or neck joint itself, but to some kind of compression/displacement of the
surrounding ribs? Intuitively, this seems much more likely than some kind of issue with the neck joint itself.
I've seen poorly made necks warp or bend, but that is somewhat rare (not among poorly-made necks, but in general).
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SamirCanada
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yeah, when the body doesn't have a face glued to it, it does indeed have quite a bit of give... so yes I think over time the string tension will
distort the body slightly and raise the action. This is not the main factor in my experience.
Typically, the neck itself is not warped but the neck joint itself fails. Its easy to test, when you apply backward pressure on the neck by pressing
near the nut can see and feel the joint moving where it meets the body. If the joint is solid, the joint doesn't feel loose and the neck doesn't have
much movement if at all.
Especially when using the wooden dowel method a gap develops overtime at the back of the neck join where it meets the body.
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Brian Prunka
Oud Junkie
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That just seems strange to me, as well-made joints in general seem to be quite stable in other circumstances. Guitars rarely have that problem,
despite typically having considerably more tension and torque. A big difference between guitars and ouds is the construction of the back.
I'm sure you're right, but it seems odd to me. On the other hand, a simple dowel joint doesn't have the reliability of a dovetail joint, which is
what I believe guitars typically use.
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jdowning
Oud Junkie
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Registered: 8-2-2006
Location: Ontario, Canada
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I am glad that faggiuols has succeeded in building a bowl with his one piece neck/neckblock arrangement. However this arrangement creates problems in
the precise fitting of the ribs over the neck block itself (the neck gets in the way) and so makes the construction of a bowl more difficult (and
slower) than it needs to be.
An oud bowl is structurally very stiff and resistant to bending under string tension. Its weakest point is at the neck joint itself where there is an
abrupt change in geometry that results in an amplification of the bending stresses focussed at that point (a 'stress raiser' in engineering
terminology). The bending stress is due to string tension acting at a distance from the neutral axis of the neck joint cross section. This bending
stress acts to open up the neck joint over time as it will do if say the glue (hide glue of course) becomes temporarily softened in high heat/high
humidity situations or if there is localised crushing of the wood fibres in the joint faces.
The other major force acting on a neck joint due to string tension is a compressive force that clamps the neck joint together - the applied force
being pretty much equal to the total string tension. The old luthiers (lute, guitar and violin makers) added to this stabilising compressive force by
using iron nails driven through the neck block into the neck (when the neck was being attached and glued to the neck block). Screws or bolts in place
of nails will have the same effect.
The other old method for guitar making - the one I prefer - is the so called Spanish method - where the neck and neck block are made in one piece and
the sides (or ribs) of the guitar are glued into vertical slots cut into each side of the neck block.
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Dr. Oud
Oud Junkie
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Location: Sacramento, CA, USA
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My experience of over 48 years of oud repairs is that the body will bend under the string tension, less if the ribs are thick, but most ouds have very
thin ribs. Comparison with guitar construction is irrelevant, they are very different designs, both in the neck attachment and the body structure.
Making a solid neck/block will require sawing and reconstruction of some type of glue joint including a spacer to recover the neck length lost in
order to adjust the action. A fingerboard on top of the face can reduce the bending affect if it is 1/8inch/5mm thick or more. Any bolt arrangement
should consider access to the bolt. If a rose is glued in it will have to be removed to adjust the neck. The best I've seen has adjustments outside
the body or neck.
The integrity of the neck glue joint is determined by the fit of the butt surfaces. If the butt joint is tight, the dowel method is fine and can last
as long as any other. A mortise/tenon is stronger, but difficult to fit precisely and still can loosen, and it takes very little gap to raise the
action. The mortise tenon is even more difficult to repair when necessary.
I experimented with a stringer through the neck and block. It was very strong, but still had an action problem after 10 years time due to body warp,
even with relatively thick ribs. The action was solved by adding a fingerboard on top that has held the action for the last 15 years.
btw, I don't believe the string tension compresses the glue joint, rather it tends to rotate the neck around the top seam. Even the slight angle of a
low action will cause a rotational force at the neck joint. The same torque affects the face and body to warp or bend the body upwards, raising the
action.
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jdowning
Oud Junkie
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There are three forces due to string tension acting on the neck joint of an oud - 1) a compression force acting normal to the joint face almost equal
to the total string tension 2) a small shear force acting along the plane of the joint and 3) a bending force acting around the neutral axis of the
joint section (tending close the joint at the top (at the fingerboard surface and open it at the bottom).
The resultant stresses (compression, shear and torsional) are amplified and concentrated at the neck joint due to the abrupt change in geometry at
that location.
The stiffness of the bowl - regardless of the thickness of the ribs beyond the neck block - is much greater than that of the neck due to the
significantly greater depth of the bowl geometrical cross section. Greater stiffness means greater resistance to bending.
How does one determine and confirm that it is the bowl that has distorted over time rather than distortions at or within the neck joint itself that
has caused a neck to raise? It takes very little movement of the neck joint to raise the action.
Yes guitar construction is very different from that of an oud but may otherwise be of general interest to luthiers and non luthiers.
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FAYSSAL
Oud Admirer
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Registered: 12-30-2016
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Hi everyone,
thank you to MIKE and all people for this opportunity to share with you my hobby for the oud I live in edmonton alberta cannada
thank you for your answer samir .
I will be back with some questions have great time for everyone
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