need your advice, pal

[davidognomo]

hi, guys

skin popped.


- bearing edge is uneven. One side is higher than the other. And the edge is not flat, straight, has small irregularities.

How do I level it? Should I turn it upside down and twist it on concrete, as some guys mentioned on other threads?

- After the leveling, sand paper and create the inside curve, wich it hasn't. It's a guinea shell. the djembe came assembled directly from conakry. Is the inside curve that important?

- The shell has these scratches from the rings. I'm kind of worried. maybe the rings are too tight. I'm guessing there isn't much of a question here. I am not going to make new rings right now. But if you think I should, let me know, and I will consider that on the next reheading.

- To clean it nice, a wet cloth? Or is it not advised because of moisture? A dry cloth was not enough.

- Shea butter on the inside and coconut oil on the outside? Is that it?


Thank you in advance,
David

[michi]

A photo would be useful.

To level the bearing edge, you can do the concrete thing, use a rasp, or use a palm planer. To check that things are level, use a workbench or similar with a level surface and sit the shell upside down on it. Then peer along the surface to see whether there are any gaps. Try rocking the shell and mark the pivot points where you need to remove more wood.

I would put a bevel on the inside edge to allow for a clean take-off for the skin and avoid buzzing.

Shape the outside of the bearing edge to make a curve that takes in the entire width of the shell.

Cleaning with a moist cloth is fine. I've even scrubbed shells inside and out with soapy water and hosed them down with a garden hose afterwards. That can be necessary if you have a shell that's badly affected by mould or bacterial growth, or has lots of dirt on it. As long as you let the shell dry properly, there are no ill effects from the water. (The exposure time is too short to really cause a problem. Just work quickly and get the shell dry again quickly once you are done.)

I would avoid shea butter, especially on the inside. Eventually, you risk bacterial or mould growth on the residue. A better option is to is to use a penetrating oil that with anti-bacterial and anti-fungal additives. These oils are normally used to protect wood that is exposed to the weather, such as decks and garden furniture.

For the outside, I like to use a penetrating wax rather than an oil. It tends to last longer and also won't make the shell greasy.

We've had plenty of discussion on this in the past. Here are some links with more detail:

• Bearing edge profile
• Images of bearing edge
• Suitable oils and waxes
• Finishing the bearing edge

Cheers,

Michi.

[davidognomo]

hey, michi, thanks a lot.

so, wasn't shea butter supposed to be the traditional thing used on shell woods?

I will post a picture as soon as I manage to get some time to do that.

Another question is the fact that the bowl, or, the edge isn't a perfect circle. If you draw an imaginary cross on top of the shell, I got a difference of almost two centimeters between the two diameters (the largest and the shorter). Bummer.

Probably, in the future, I will get another djembe (the more, the better), but right now, this is my baby... And, you know, when you're truly in love, you love the qualities and the deffects. But I think the qualities, in this case, are the majority, by far.

On that post of the bearing edge profile, on the drawing, isn't the edge a bit sharp?
And, you mention rubbing the edge with shea butter. You have updated your opinion, is that it? Or the edge is ok with the shea butter?

Thanks again michi.

David

[michi]

so, wasn't shea butter supposed to be the traditional thing used on shell woods?

Shea butter is fairly popular. Despite that, I wouldn't use it (at least not on the inside). The shea butter is fairly thick and, with the rough interior, you'll end up with a layer of shea buyer on the inside that makes an ideal nourishing ground for bacteria and fungi. A penetrating oil will be more effective, penetrate better into the wood, won't leave a residue, and won't get attacked by bacteria or fungi (if you use one of the modern exterior decking oils).

For the outside (if it's fairly smooth), shea butter works well. However, I prefer a penetrating wax (possibly adding a finishing wax over the top on smooth shells) because wax is more hard-wearing.

Another question is the fact that the bowl, or, the edge isn't a perfect circle. If you draw an imaginary cross on top of the shell, I got a difference of almost two centimeters between the two diameters (the largest and the shorter). Bummer.

When you orient the spine, either have it run between the two widest points or between the two narrowest points. The idea is that the areas left and right of the spine should be symmetrical, so you get evenly-pitched tones.

Whether you put the spine along the long axis or along the short axis is a matter of taste. The idea of putting it along the long axis is that the tension on the skin will help to keep the bowl round because the skin stretches less along the spine than across the spine. The idea of putting it along the short axis is that you end up playing the drum at its widest point, so you don't cramp in your hands.

Personally, I prefer to mount the skin along the short axis (but many people disagree with me on that). I don't think it matters much in terms of reducing bowl distortion because the tension on the skin typically isn't strong enough to squash an oval bowl even flatter. But, by all means, if you are more comfortable putting the spine along the long axis, go for it. The most important thing is to have symmetrical areas either side of the spine.

On that post of the bearing edge profile, on the drawing, isn't the edge a bit sharp?

On the drawing, yes. That's just because it was easy to draw that way. Have a look at the photos I posted in the articles I linked to. In practice, the edge won't get as sharp as on the drawing. (But do keep it reasonably sharp--a rounded edge can cause buzzing.)

And, you mention rubbing the edge with shea butter. You have updated your opinion, is that it? Or the edge is ok with the shea butter?

For the bearing edge, shea butter is great. It helps seal the edge against moisture, reduces friction, and it won't damage the skin.

Cheers,

Michi.

[shortypalmer]

I use an electric hand plane to level the top and then check it with a piece of glass.i used to always use the concrete but you need to check the surface of the concrete first with a straight edge to make sure there is no unevenness to the concrete then onto a router to get the curve. i also round off the inside and it think this makes a difference, i believe it enhances the bass tones. I use boiled linseed oil (it comes already boiled from the store) mixed with mineral spirits. the mineral spirits is best if it is no odor or low odor, i mix two parts mineral spirits to one part boiled linseed oil.
On to the spine placement, i guess i disagree with Michi, I always put the spine on the long side of the oval, if you notice an oval drum it will always have the spine on the short side and to me this says the spine caused it to be out of round. by putting it back on the long side i believe the drum could over time lose of the oval.

[michi]

On to the spine placement, i guess i disagree with Michi, I always put the spine on the long side of the oval, if you notice an oval drum it will always have the spine on the short side and to me this says the spine caused it to be out of round. by putting it back on the long side i believe the drum could over time lose of the oval.

I suspect that it isn't the spine that causes the oval shape. Rather, the drum started life being oval in the first place. (At least, that's what I see on quite a few shells that are imported from the carvers. Few of them are perfectly round.) At least on such shells (I've skinned many of those), I've never noticed the oval getting more pronounced with the skin mounted along the short axis. I don't think the tension on the skin is strong enough to change the shape of a shell by more than a minuscule amount, and the shell will spring back once the tension is removed. (That's for proper traditional hardwood shells; I don't know about djembe's made of softer substitutes.)

But, as I said, there is no absolute hard and fast rule. I think it's a matter of personal preference and aesthetics (religion? ) more than anything else. A bit like the little- and big-endians in Gulliver's Travels

Cheers,

Michi.

[Dugafola]

On to the spine placement, i guess i disagree with Michi, I always put the spine on the long side of the oval, if you notice an oval drum it will always have the spine on the short side and to me this says the spine caused it to be out of round. by putting it back on the long side i believe the drum could over time lose of the oval.

I suspect that it isn't the spine that causes the oval shape. Rather, the drum started life being oval in the first place. (At least, that's what I see on quite a few shells that are imported from the carvers. Few of them are perfectly round.) At least on such shells (I've skinned many of those), I've never noticed the oval getting more pronounced with the skin mounted along the short axis. I don't think the tension on the skin is strong enough to change the shape of a shell by more than a minuscule amount, and the shell will spring back once the tension is removed. (That's for proper traditional hardwood shells; I don't know about djembe's made of softer substitutes.)

But, as I said, there is no absolute hard and fast rule. I think it's a matter of personal preference and aesthetics (religion? ) more than anything else. A bit like the little- and big-endians in Gulliver's Travels

Cheers,

Michi.

i agree with shorty on this one.

i've corrected out of true shells by mounting the next skin 90* in relation to other.

the skin is usually the most stout part of skin. if you apply the same amount of tension all around the drum to get a solo pitch, you're gonna find out real quick if the shell can handle a meaty skin at high tension.

it goes back to the discussion about mating the right skin for the shell. my oldest and prized drum is a 14"+ jalla piece carved for me in jan. 2005. this was way before the super chunko shells started coming out of guinea. i know that the heaviest skin this drum can handle is what i'd consider a 'thick' to 'med. thick' guinea skin. senegal, mali and IC skins will oval the shell if i tuned it up to solo pitch.

i pick skins based on consistent thickness top to bottom and side to side...not just up near neck or thickness of spine.

nowadays most of the 'boutique' import drums coming out of africa are thick and can handle thick goats and calfs with no issue.