Sealing a large beech log for a drum + dealing with mould

[howlingbaboon]

Hi everyone,

I'm new to woodwork and the site. Although my question is not really wood turning (although I'm interested in getting into that too), I figured that you would be the people to know. I have fairy large, a recently cut beech log (maybe 13" diameter) which I'd one day like to carve a drum out of (like an African djembe hand drum).  It's been stored in a well ventilated outhouse since the tree was felled a few weeks back. I'm not even really sure if beech is suitable but I'm a drummer and quite sentimental about that tree so would love to make something special from it. I've got 3 questions really:

1. I've heard that the ends should be sealed to avoid cracking. What should I use to do that?
2 . I looked at it today and it had a little white mould growing from the top end. Is that going to be a problem? What would you suggest?
3. How long do you think it will need to season?

Any advice you can give will be most appreciated, cheers!

[seventhdevil]

it will need to be hollowed out immediately to let it dry without cracking.

i seal my timber with pva.

you won't dry a bit of wood like that in one piece anyway. i think you would need to leave it for about 200 years to get it dry enough at 13" wide.

to prevent mould it needs to be kept inside in the dry. you could try spraying it with dettol.

[Les Symonds]

The biggest issue is the imbalance in stresses within the log. When the log is still a part of a growing tree, those stresses are held in equilibrium, but as soon as the tree dies and moisture stars to evaporate, its cell structure shrinks a little and stresses move into imbalance.
Consider the growth rings....a growth ring close to the pith may be only a couple of centimeters in perimeter, so 10% shrinkage while it dries could result in a couple of millimeters of shrinkage. However a growth ring close to the bark of a 13" diameter log, is about 100cm, so shrinkage could be as high as 10cm. In reality that's going to result in one or more cracks running down the length of the log, and there's not a lot that you can do about it.
Slowing down the rate of moisture loss helps the stresses to be relieved more slowly, and thus causes less cracking, but does not eliminate cracking. Coating the ends of the log will achieve that, but there is no guarantee (in fact, it's unlikely) that a log this size will not crack. The ancient wisdom in this matter tells us that air drying wood takes about one year per inch of thickness - in our climate - but that's a long time to wait to discover the cracks in your log!
As Steve says, getting it hollowed as soon as possible is one solution. By removing much of the excess timber, the drying process will be much quicker and there will be less imbalance left in the log for its internal stresses to cause the cracks.

There is, however, one important issue that has not been mentioned.....the African Djembe is a traditional design native to West Africa, where the cell structure of the trees is different to that of English beech, and where the climate is very different to ours. That's why bongo and djembe makers in UK tend to start with flat planks and make up the drum bodies out of segments. I'm not saying that making a djembe in the traditional way is not going to be possible, and I applaud you for having a go, but it's going to need a skill-set and knowledge-base that you may not yet have considered.

I wish you well in your venture....Les

[howlingbaboon]

Thanks for the advice guys. I was counting on a long wait before hollowing it out as I've been quite ill for a while and am too weak to do it at the moment. Whereas I'd like to think I'll be strong enough in the future, I'm not sure I'll make it to 200! Although I'd envisaged doing it all by hand with axe and chisel, I may now have to cheat and get the drill and hole saw involved a bit. Once hollowed, should I then seal it? Just the ends or the inside?

[howlingbaboon]

How much do you think I should hollow out? In the end, It's basically got to be bowl shaped at the top half and cone shaped at the bottom with a fairly small hole joining the two. Should I also take some wood off from round the middle on the outside? It's going to be kind of hourglass shaped in the end. I just not quite sure how much to do initially and how much to wait for.

[Les Symonds]

It will help if you can hollow it out to a fairly even thickness throughout, and the thinner you go, the more of the stresses you relieve. Also, when you make the hole through from the drum to the base, it will help if you can remove the pith, as that's the centrepoint (epi-centre) of many of the stresses.

Les

[seventhdevil]

How much do you think I should hollow out? In the end, It's basically got to be bowl shaped at the top half and cone shaped at the bottom with a fairly small hole joining the two. Should I also take some wood off from round the middle on the outside? It's going to be kind of hourglass shaped in the end. I just not quite sure how much to do initially and how much to wait for.

hollow it out to about 1 1/2" thickness for this sort of drum and literally cover it in pva or paint to seal it. in effect you just want to make a chunky shell that you can refine when it's done some drying.


do not wait at all as in my opinion you will only be waiting for it to split. i have a bit of experience with this as i use a similar process for my skittle blanks. all my wood starts out at 5 1/4"- 5 1/2" square and 7-8' long. once it's had about 10-12 months to season i cut it into the lengths i need for my blanks (range from 11-16") and turn it into cylinders. this releases some of the stress and should reduce drying time.

all ends are sealed in a thick layer of thick pva. i then weigh all cylinders so i can keep track of how much weight they have lost and once they stop loosing weight they are dry enough to use.

once you seal your freshly carved djembe drum blank weigh it and write it on the drum. keep it out of sunlight and the wind but make sure you keep it in a humid enough environment. if you store it in too dry a location then you run the risk of it splitting. 65-70% humidity would be ok but buy a hygrometer to make sure you know what the humidity is in the area you wish to store it as with summer approaching you need to monitor it.

[howlingbaboon]

Thanks for all the advice, I've sealed it with PVA for the time being and will set to hollowing it out in the next few days if I'm up to it. I'm glad I sought advice as I've spotted a crack radiating out from the centre but it's not got far yet so hopefully it will stop once I hollow it out beyond that point. Any advice on the best way to hollow it in the absence of a massive lathe?

[seventhdevil]

if you want to hollow in a hurry then get an angle grinder and attach one of those arbotech cutters that wood carvers use.

[fuzzyturns]

if you want to hollow in a hurry then get an angle grinder and attach one of those arbotech cutters that wood carvers use.

And please, please, please be very careful when using the arbotech (or anything similar), it is a vicious tool. It can remove large amounts of wood in very little time, but the same goes for your fingers or any other body parts. I would recommend wearing a reinforced glove on the hand holding the wood for an absolute minimum, and I am sure John BHT has a word or two to say as well.

[Dave Atkinson]

Never hold a piece of wood in one hand and use an Arbotech in the other.  That's asking for trouble.  Always hold an Arbortech with two hands (as the manufacturer suggests).  The wood should be firmly held in some sort of vice or clamp.  Make sure it is secure and won;t move before you bring the Arbotech into play.

Cheers Dave

[Mark Sanger]

Yes take care, as this chap will testify http://warriorsmark.blogspot.co.uk/2015/10/a-wood-shop-accident.html (contains blood)

[The Bowler Hatted Turner]

I don't think I need to add much to this conversation, like the chap in Mark's example I would explore other ways and means of hoolowing it out.