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Repairing Cracks in Djembe
From email compilation, March 2003
Djembe-L elist
Djembe-L@yahoogroups.com
From Beverly Nadelman <PrismConcepts@yahoo.com>
There are two guys on this list from whom I have learned much in terms of working with wood. They are Shorty and Chris. Each of them knows a whale of a lot more than I, so wait until they check in as well, but for starters, your friend needs to find the very end of the crack, inspecting carefully because it will probably probably just look like a hairline. Drill a small hole at the end of the crack. That will keep the wood from splitting any further. Then take a small piece of wood, say a wooden match or a piece of wood whittled to fit, coat it with a good wood glue (I use Titebond II) and shove it in the hole, cutting it off even with the surface of the drum.
There are a couple of ways to go with the crack itself, depending on what it is like. I am assuming, from your description of the sound, that the lips of the crack have already split apart and are permitting air to escape. If that is true they may be able to be pulled together-or not.
To pull the lips together, if it is possible, the head will need to be removed and the rope and top ring either removed or pulled down. Wrap the drum with a strong piece of rope or web belting(my preference), tie a good knot in it, stick a very strong stick in it (I use an axe handle) and start twisting. (You might need two or three lengths of webbing at different points around the bowl of the drum, depending on its size and the location of the crack.) There is a name for the kind of vice this makes, but I forget it.) It will be easy to twist at first, but may take two people toward the end. On djembes it is sometimes difficult to keep the webbing from slipping, depending on the flare of the bowl. It is easiest on Senegalese style bowls, which tend to flare less. If the lips of the crack can be brought together this way, untwist the webbing until the crack opens, coat the lips with Titebond II or a good slow drying marine epoxy, twist the webbi! ng back until the lips of the crack meet tightly, tie the stick or whatever has been used to vice the lips together, and let it dry thoroughly in a warm but not hot place. Do not put it next to the wood stove or furnace to hasten the drying.
Alternatively, if the lips of the crack cannot be brought together, take sawdust, preferably from the same kind of wood, and mix it thoroughly into wood glue until it is maleable and putty like. Use that to fill the crack, letting each layer dry thoroughly before applying the next.
If the lips of the crack are not apart I cannot think why the sound would be affected, but should that be the case, and the crack not all the way through the wood, you need to chisel the crack a bit more open, preferably using a thin sculptor's even sided chisel rather than a chisel with only one beveled side, working from the surface of the crack into the solid wood. You would actually be making it larger. Side view it would have a triangular shape with the point of the triangle at the surface of the wood, the base on the inside. Fill with a combination of fine sawdust and wood glue as above, packing it in tightly. If you do a good job, when sanded down and touched up it should blend nicely into the surrounding area.
How'd I do, guys? If you have better suggestions, Chris and Shorty (or anyone else), I am still an avid learner.
Beverly
Wil-
Thanks so much of reminding us about Joe and all the websites he used to spread before our hungry eyes for us to feast on, and thanks for the one you sent along.
Beverly
On Wednesday, March 12, 2003, at 09:12 PM, djembe wrote:
Fixing cracks is not hard, I drill a hole at the end of the crack so it can go no further. then all you have to do is fill the crack. you have several choices to use to fill the crack. if the crack is small and does not go all the way through, you can use some form of wood filler that you can color match. if the crack is bigger and goes all the way through, which sounds like your has, you might want to consider using saw dust and glue. when done it will sound like new and more then likely never be a problem.
shorty
There's no point drilling a hole in wood to stop a crack - it's not metal!
The crack is happening to accommodate the changing size - usually shrinkage - of
the wood itself. So... it is very important to stabilize the wood, ie, feed it
some moisture and seal it in. I find Danish Oil works wonders.
Many times I've experienced 4mm internal cracks closing right up after just one
application of Danish Oil.
Once the cause has been treated, then fill the crack with expoxy resin, glue,
etc, mixed with saw dust.
Cheerz,
Lynzz
The only time when I have heard a really "flat" bass out
of a djembe was
when the skin was very loose. That seems to be not the problem here, so
sorry, no advice on this.
I am assuming the bass was OK before he took the drum in? Did your friend
actually hear and play the instrument before buying it and/or reheading it?
Nothing left inside the drum, is there?? Cloth, piece of skin?
Cracks can be filled with a mix of wood glue and sawdust. As far as I know,
narrow cracks don't affect the sound much (neither bass nor tone or slap)
but they don't look good and may affect the strength of the shell. And just
my own take: if a pro did the reheading, I would have expected this person
to see and mention the crack at the top and suggest filling it, which will
be easier to do when the skin is off.
Hope this helps!
Dennis
From Shorty:
djembe@prodigy.net
Steve Courtright <scourtright2000@yahoo.com>
In furniture making, often cracks are stabilized by
butterfly-shaped wood inserts which span the crack and prevent further
spreading of the crack. This solution works for furniture because there is
only appearance to be concerned with. It might not work for the drum unless
you can draw the edges of the crack together and glue with the butterflies in
place.
It sounds like the crack in the drum has degraded the physical integrity of
the drum shell and prevented proper rogation of the sound energy through the
drum material. In a guitar and other instruments, any boundaries which
prevent wave propagation of sound energy results in lessened sustain of the
notes and poor sound balance from the instrument. Same thing here; the crack
prevents the shell from resonating and prevents the sound energy from being
stored in, released from and transmitted through the drum.
If the edges can easily be drawn together, today's glues are stronger than the
wood and it may hold if clamped by a web clamp or an equivalent circular
clamp. You want the instrument to regain its original rigidity. It may be
very difficult, since the drum was under great stress during drying and
forming to cause the large crack in the first place (and small cracks seem to
be common for the same reason), to merely pull the drum back together. A
better, and of
course, more time consuming solution, would be to carefully prepare the crack
to receive a spline-shaped insert like a longitudinal shim and glue in place.
This depends on the crack. Is it possible to open the crack with a narrow
wood file so that the crack is a fixed width? Then prepare a narrow wood
spline and glue in place, maybe under some compression so that
the drum shell actually holds it in place during gluing. If the crack wanders
some, it may be possible to soak the shim in hot water or steam (like boat
building) so that the shim is more flexible and conforms easily to the crack.
Needless to say this sounds like a lot of work and may best done by a skilled
woodworker with the right tools...
from: "Walter Alter" <limejello@earthlink.net>
In order to repair the drum without removing the head,
I'd suggest using a
two part epoxy, working the epoxy into the crack with a putty knife from the
inside. It means reaching way up there and going by feel. work the epoxy
in until it comes out the front if the crack is wider than a playing card.
If it is narrower than this, you probably won't get it to pressure all the
way through. Fill it as best you can from the inside, let it cure for an
hour and fill it from the outside. The bass tone is suffering from the air
leak caused by the crack. A quick and dirty fix just to get the bass tone
back for a gig or a class would be to duct tape the inside of the crack.
Walter
From Ray Rhulen rlruhlen@earthlink.net <rlruhlen@earthlink.net>
Yes, pretty easily done. Take off all the hardware and ropes, head, etc. Get
some wood glue (white, yellow, or hide - any is fine) and a strap clamp
inexpensive at Roecklers, Woodworkers, or other woodworking supply or even
hardware stores. You might need some clamps or even little carpet tacks to
keep the strap from sliding down the shell, depending on where you need to
put the strap. Then put on the glue and tighten the strap until both
surfaces are tight against each other, wipe off the excess glue and let dry
for one to more days depending on the humidity and temperature. That's all
there is to it.
Getting a little more complex, if you are afraid of the crack spreading
later, you can drill a hole at the end of the crack and glue in a wood plug
(also available at woodworkers stores), sand off and finish. You cant match
the wood exactly but you should be able to get a close match (or you can
stain the plug after sanding, but before inserting in the hole), but it will
be so small as to be unnoticeable.
Ray
