Shrinking shells and loose bands

[Mike]

What can you do if the wood of a conga shell has shrunk
to the degree that the top band is already starting to rattle
if you tap on it?
It has happened with my Gon Bops conga from the 3000 series
and I wonder what I can do about it:

- taking the band off and trying to push it further down?

- or even epoxying the shell so that the band will fit better?

- or taking it off at all?

Any experience or tips to share are appreciated!

[windhorse]

The top band on all of mine is loose, and I'll be taking them off next time I remove the heads.
I also have a bottom pressure fitted protection bands which I'll tighten with a tiny amount of gorilla glue.
common problem in dry climates. Cosmetic bands IMO are useless.

[jorge]

This is a problem in climates with cold winters and warm summers caused by heated dry winter air alternating with humid summer air. When cold air is heated in the winter, the indoor relative humidity drops way below the outside relative humidity. This dries out the wood slowly over the winter, causing it to shrink. In summer, the humidity slowly restores the moisture in the wood and it re-expands. Some woods expand / contract more than others. Jay Bereck told me that he chose cherry because it had the lowest coefficient of expansion with moisture of any of the woods he was considering. Coefficient of expansion, or stability, measures the amount of shrinkage/expansion of wood given a certain change in relative humidity. This is different from coefficient of expansion for temperature changes, a negligible factor for congas. The main factors that affect wood expansion are extremes in relative humidity beyond 35%-65% range, species (see chart http://www.planethardwood.com/documents/WoodStabilityChart.pdf), grain orientation (flat sawn more expansion along the length and width of the stave than quarter sawn), and how well the finish seals the wood.

In my personal experience in New Jersey (humid summers, cold dry winters), I had two quarter sawn oak Skin on Skin drums finished only with Watco oil both crack in multiple places during their first several winter/summer cycles. One ash SOS with polyurethane finish cracked in the winter as the wood shrank around the alma. Two quarter sawn oak SOS drums finished with polyurethane on the outside have never cracked. My cherry SOS with polyurethane has never cracked. Most of the cracks form in the glue line between the staves. Once fixed and refinished with polyurethane, the oak drums never cracked again. This is the first winter for the ash drum after I fixed the cracks and moved the alma to make a less tight fit in winter. Humidity in my studio ranges between 70-80% in summer and 35-45% in winter.

In mid winter, I have taken the screws off the loose bands, moved the bands down or up the drum to a larger circumference area until they are moderately tight, drilled new screw pilot holes (partial thickness) and replaced the screws. I have not yet had a SOS band pop in summer, but this can happen, especially with the thin aluminum bands like some Gon Bops drums. I did this with a Gon Bops drum many years ago and several of the rivets popped in the summer.
Oak The bands don't shrink and expand, so the relative circumference of the shell and the bands changes with the seasons, leaving loose bands in the winter and tight bands in the summer. Some of the drums still have bands a bit loose in the winter that can rattle, others stay tight. On most makes of drums, the bands are mostly for aesthetics and loose bands will not affect the integrity of the shell.

Ways to reduce the expand / shrink process in the cold climates include:
1) Use a dehumidifier or AC 24/7 in the summer and a humidifier in the winter to reduce the seasonal variation in humidity. Expensive and fossil fuel dependent, but comfortable. Fresh air ventilation of damp basements may help.
2) If your drums have oil finish only on the outside, seal the outside with polyurethane. Do not seal the inside. Polyurethane inside the drum would reduce expansion/contraction but would make most drums ring and sound much worse. Partially effective.
3) Fix existing cracks before sealing the wood.
4) Cherry probably is better than oak (even quarter sawn) and ash. Not sure about mahogany. Anyone with mahogany drums who can report on your experience?
5) Never heat your home in the winter. This can be bad for your hands, not to mention marriages, kids, dinner guests, etc.
6) Move to Cuba or other Caribbean island or take your drums there every winter and never miss a year. You may have difficulty leaving every spring. Risk of jail, large fines or losing some of your Cuban friends if you live in the US.

[Psych1]

Agree with Jorge - especially point #6 - I'm really considering it. Also agree with Windhorse about decorative bands. My El Piernas bongos had bands that were strictly decorative and the rattle drove me nuts so I just took them off - problem solved. But, the GB 3000 series mahogany congas are a different story. I have a few of them now and have had many over the years. The bands are always loose in the winter and tight in the summer and when tight they do serve a structural purpose. If the rattle bothers me I just stick something behind the band - same as I do with a table leg when a table gets wobbly. I say - leave them alone and enjoy the seasons. Glue the cracks and keep on going.

[Mike]

Jorge, well, no. 5 + no. 6 is not really an option for me, and I just cant stop the fact that is is
winter here
And there have not been any cracks yet in my Gon Bops Philippine mahogany shell either as I do take
care of temperature and humidity the best I can.
The bands on my Gon Bops are more or less decorative I reckon, but I have heard that some
of those older drums tend to crack even if those thin, cosmetic bands are removed.
The only option for me in the long run seems to be epoxying the shell, but that can wait a little.

Until then I might live with it - just wanted to know what you guys do except moving to Cuba

[burke]

This may be simplistic, but when I've had drums with loose bands all I did was take out the tacks holding them in, tap them gentlely with a hammer and nail set till they were snug and put the tacks back in.

Seems to work.

Darrell

[Mike]

This may be simplistic, but when I've had drums with loose bands all I did was take out the tacks holding them in, tap them gentlely with a hammer and nail set till they were snug and put the tacks back in.

Seems to work.

Darrell

Now that´s what I call a tip, Darrell I have just not dared so far because I am not too familiar with bands, so seriously, thank you for this tip.
The only question still clinging to my mind is: Can I stop possible future warping of the shell by inserting a fiberglass layer
INSiDE the shell? Or/and outside too?
Apart from potential sound alterations, the question is also how long such a drum "lives" - or rather, if I will outlive the drum or vice versa

[bongosnotbombs]

This may be simplistic, but when I've had drums with loose bands all I did was take out the tacks holding them in, tap them gentlely with a hammer and nail set till they were snug and put the tacks back in.

Seems to work.

Darrell

The only question still clinging to my mind is: Can I stop possible future warping of the shell by inserting a fiberglass layer
INSiDE the shell? Or/and outside too?
Apart from potential sound alterations, the question is also how long such a drum "lives" - or rather, if I will outlive the drum or vice versa

I reckon if you fiberglass the inside of a wooden drum shell, you might as well be playing a fiberglass drum. I don't see the fiberglass really helping, structurally fiberglass works in tension, but could not resist a shell pulling away from it all that well. It's best application is on the exterior. Unless the idea is simply to seal the drum. I sympathize with all you guys in places where the weather causes problems with your drums. I would think keeping them inside cases and bags might go a long way towards maintaining your drums. I wonder how guitarists and bassists maintain their instruments against weather extremes.

[Mike]

I reckon if you fiberglass the inside of a wooden drum shell, you might as well be playing a fiberglass drum. I don't see the fiberglass really helping, structurally fiberglass works in tension, but could not resist a shell pulling away from it all that well. It's best application is on the exterior. Unless the idea is simply to seal the drum. I sympathize with all you guys in places where the weather causes problems with your drums. I would think keeping them inside cases and bags might go a long way towards maintaining your drums.

The latter one being difficult because I like my Gon Bops ready to go in my study room as soon as I have done my duties..
But you are right, Geordie, fiberglassing inside really alters the sound, and that is something I particularly do not want with this Gon Bops.
I have tried my best to keep the GB conga from going out of round, and perhaps one or two layers of fiberglass outside the shell might prevent further out-of-round-going. BTW I have done the re-mounting of the skin in clockwise fashion every 3 months or so for the last year, and the drum is more or less fine now.
So I am seriously pondering the option of fiberglassing (not only epoxying) the outside. It´s just not the weather now to engage in an open-air fiberglass mess with 5 degrees below celsius...

[Bongobilly]

Mike : I just brought some Epoxy today, Just waiting for the sun to warm up my sun room so i can try it out. Will post when this happens.

[roberthelpus]

Some guitarists use case humidifiers and the like for acoustic guitars. For solid body electrics it's not really a problem other than some tweaking of the truss rod and that's not too often. Maybe a little bit of intonation adjustment along with the truss rod adjustment. I've never really had any problems.

[BMac]

Somebody needs to state the obvious here.
The heart of the problem being discussed here lies in the bands and the almas ... not in the wood.
Wood and steel have different thermal properties so they expand and contract differently under thermal fluctuations.
The same goes for their behavior under humidity and moisture content fluctuations, with the caveat that steel's only moisture behavior is rust if things go too far.
But the Don Quixote's of the conga world will perhaps always chase those windmills ... insisting that congas MUST HAVE ALMAS ... the old "spirit in the drum" thing ... and the beat goes on.

I've said it before. I'll say it again.
Almas have cracked more drums than they've saved.

Cheers!
BMac

[bongosnotbombs]

Well I'm familiar with Mike's model of Gon Bops. The bands are mainly cosmetic on those and they are not made with almas. So the trouble here seems to be the expansion and contraction due to moisture, particularly at the seams, as the movement overcomes the adhesion of the glue. I like Charlie's method of sealing the interior with an oil that does not harden, like tung oil. However I don't do anything like that as I'm fortunate to live in temperate San Francisco.

[Herbal]

You can cut thick plastic squares a bit bigger than the bottom of your drums, put a wet sponge in the middle, then sit your drum over tip the sponge. You can buy an acoustic guitar humidity reader at most music stores. I ran into problems with a 1970 Martin when I moved over here and while I was there talked about an older drum splitting and my luthier/drum mechanic educated me about old wood. The guy is a master luthier who Martin hooked me up with, he knows his shit.

I live in an extremely hot humid area, lotsa mold problems in the summer, and then we have cold winters. Going from extreme humidity to the dry heaters of the winters and a lot of modern air conditioners suck moisture from the air - all of that is hell on wood.

Plastic and a wet sponge can keep your wood from constricting and expanding.

[Ernesto Pediangco]

KEEP the bands on ! simply remove the tacks that hold the bands in place, tap them down as tight as posible w/o scratching the shell in the process , check its level fit position & replace the tacks ( dont hammer them to hard ) The bands have a purpose ! The drums loose value it the orig bands are not on the drum. The aluminium bands some times stretch as the drum expands & contracts durring the years. Newer Gon Bops from the Molinari era ( mid to late 90's ) and Timba brand also upgraded to steel bands. I would not glue them into position on the shell though !