Mandolin Neck Problems
Home Hospital Re-veneering Re-setting an Italian Neck Re-setting a German Neck

 

Bowed Neck

One of the first things obvious in many old mandolins, is that the neck appears warped. This is possible, but the problem is usually movement at the neck-body join. Unseasoned wood, excessive string pressure, or even exposure to high temperatures, can result in movement at the join, often resulting in the neck being pulled up, and/or the back being deformed or split, and sometimes the heel split. If this is more than slight, it will make the instrument unplayable.

Technically the neck is not bent, it has moved.

The most fundamental aspect, other than obvious damage which needs to be repaired, is to assess how playable the mandolin is going to be. Re-setting the neck is a difficult and time consuming exercise, and should not be undertaken lightly.

All other possibilities should be explored first.

Neck movement like this seems much prevalent in Italian instruments than German, and more in bowl backs than other styles.

 

 

Repairing a Snapped Neck
   Finally, if the neck-body join holds, occasionally the neck will be snapped as with these instruments above. Left, the two sections will be re-glued with a strong modern adhesive as the break was partial but clean, being held together by the f/b. With the second a similar solution, though the break is along the diagonal head-neck join found in many 2-piece Italian instruments and the f/b was completely shattered. The third and fourth have both split along the diagonal join as well.
 Most of the Italian mandolins had a 2 piece neck and head arrangement, as it was much more economical than to carve both together out of the same block of wood. The join that seems to be visible at the end of the neck, is only the end of the veneer that covers the join. The real join is not immediately evident because most of the necks are veneered, which hides the join nicely, but also strengthens it on the 'lamellar principle'.

When this join goes, often the fingerboard goes too, and you are lucky if you have all the pieces to re-assemble.

Here is a typical problem..... a neck that has split along the diagonal glue join, that has been repaired previously. A piece had been inserted

The first task when repairing a break is to assemble the pieces, or in this case, to remove the old failed repair and clean off all glue.
   You first need to decide whether you glue the neck and f/b together, or remove the latter first. I usually remove the f/b first for 2 reasons. 

  • One, if your join does not work too well, or looks fragile, it is possible to chisel a channel in the neck and insert a 'sleeper' across the crack. 

  • Second, until all is rebuilt, you won't perhaps know if you need to 'shim' the f/b or not...  best to remove it now, then you can shim more easily, and the shim will further strengthen the neck across the break.
First I carefully split apart the neck trying not to damage existing pieces. It looked like the extra piece had been glued in to hold a weak join, but perhaps the join itself was not made-good first. Next the failed insert was removed and glue cleaned off the surfaces to be rejoined. It is necessary to trial fit the pieces carefully before gluing to ensure a good fit.
In this case the re-gluing was in 2 parts, first the neck was re-glued, with cascamite, a strong modern glue. Titebond or hide glue will also do. Then part of the inserted piece was glued back to re-enforce the join and rebuild the neck shape. A separate piece was inserted in to the cavity in the head.
Afterwards, both the head back and the neck were re-veneered, to add extra lamellar strength to the repair, as well as to improve its cosmetic appearance.

Neck clamping block

 
   It is very difficult holding a neck under pressure when trying to re-glue parts of it, so you will need to build a simple neck clamping block to help.  The simplest way to do this, is to cut some blocks 70 x 40 x 15mm for the base, and 40 x 40 x 15mm for the shoulders.

Cut shoulders as above, glue and fit felt. Tapered at one end, and several different width gaps are useful as necks are not a uniform size or shape.

 

Neck-body Joins

Some problems like a very high action, can only be resolved by a complete neck reset.

  The task of re-setting a neck is quite difficult, and should not be undertaken lightly. It requires a lot of skill and care, both in the extraction, and more importantly, in setting up correctly before it can be re-glued. Before beginning the process, it will be useful to look at the two main types; a wedged join and an integral-heel neck.
Wedged Joins

This type of join is more usually found in German and more modern mandolins. Essentially a block is built into the body, with a wedge shape cut into it. The neck correspondingly has a wedge at its base which fits into this cavity. When it fits less snugly, small inserts will often be found down each side of the wedge to jam it in securely. The top may be cut around this wedge, so that the neck can be extracted without removing the top... but this is not always the case. German bowlback mandolins also often have this type of neck join, though again, not always.

 Integral-heel Joins

   This is the type of join normally found in old Italian bowlback mandolins, where the neck and heel wood is built into the form, around which the bowl is then built. After the bowl is built the neck and head are shaped. Because the bowl was built onto the heel itself, this makes altering its orientation to the neck very difficult. Fortunately, for reasons of economy of wood, the heel is usually not a single piece but two, and this fact makes it more feasible to split the heel, removing the neck section, and leaving the other as a stable base for re-gluing. Sadly it is almost always necessary to remove the top before working on Italian neck joins, because the top will normally cover the heel entirely.
Here a German wedge-join can be seen after extraction of the neck. It has not been necessary to remove the top. Here an Italian neck and heel can be seen to be one piece, almost like a horse's hoof in shape, though the heel is often made up of two pieces of wood.