What is the best way to glue these cracks?

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What is the best way to glue these cracks?

Postby Kona » Sat Sep 17, 2011 10:39 pm

I've got lots of information on how to glue and what to use.

This large crack has old glue (left in the glued part near the bottom). Do I just leave well enough alone and add my new glue - or should I completely separate the staves, clean both sides and glue the drum back together with new glue the length of the staves?

UNGLUED STAVES1 (Custom).JPG

AFTER USING PAINT REMOVER3 (Custom).JPG
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Re: What is the best way to glue these cracks?

Postby Chupacabra » Sun Sep 18, 2011 12:43 am

Hm, that's a pretty big split. Looks like someone tried to fix it previously and gave up.
There's no easy fix to this problem. If you try cleaning out the old glue and clamping it, you will split or separate the shell somewhere else. The only way to permanently fix the shell is to separate all the staves after numbering them in sequence, clean out all the old crap, get a 1 litre bottle of Titebond 3 and apply an even and light coat of glue to all edges. You will have to plan your reassembly steps very carefully so you don't end up with a big, gluey mess on your hands!

Oh, the good news is that if it separated like this in one joint chances are good that many of the others will give up easily too. Just be careful not to split the staves! I've read that vinegar might help to soften the glue, you might want to research that.
Good luck!
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Re: What is the best way to glue these cracks?

Postby Kona » Sun Sep 18, 2011 3:10 am

Thanks Chupacabra
I thought about taking all the staves apart but I don't want to get into that big of a project.

I will probably just take the old glue off these two edges. There are some other small splits here and there and a very small 'bong-type" crack - looks like the drum came into contact with a small blunt object and the wood split/broke a bit. I'll do my best with the wood glue and wood dust I've collected and bind the drum together carefully - put everything back together and see how it sounds. If the drum does crack again I'll think about taking all the staves apart, numbering them and go that route. If I did do that I'd ship the wood off and get a Pro builder to put it back together for me.

Thank you for the input......lots to think about - it's all good,

Cheers,

Gary
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Re: What is the best way to glue these cracks?

Postby Kona » Sun Sep 18, 2011 5:15 am

Okay - I've got the glue cleaned from between the staves that had the large crack - I took all the glue out so the drum is separated now. However, the staves touch at the batter end and at the reso end - they meet as they should I guess, but in the middle of the drum the staves do not meet. Does this mean I should sand between the staves at the end - bringing the middle of the drum closer together so I can glue it? I did spend a bit of time with 100 grit sand paper in the tight areas to try to bring the staves closer together. It looks like that may work....and.......should I keep doing that and then use a filler to bring the drum tight together?

There was very little glue at the ends of the drum and a lot of it in the middle........that's why there's a gap in the middle part of the staves now. Maybe the drum was repaired at one time.
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Re: What is the best way to glue these cracks?

Postby Jerry Bembe » Sun Sep 18, 2011 6:13 am

Filler will be your safest bet. Use a filler that has a glue quality. If it shrinks then use epoxy to fill the fine cracks from shrinkage. Epoxy is the strongest glue to use but it can be messy. I like to use epoxy from the inside.
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Re: What is the best way to glue these cracks?

Postby Psych1 » Sun Sep 18, 2011 6:17 am

There is a great line, usually attributed to Voltaire, about the "best" being the enemy of the "good." That is probably true in this case. Also, in your first thread I mentioned what I thought was the best way and Jerry responded that there is no "best" way and that is probably true also. Also, I said repairing a split between staves is easy, which it is. But, repairing someone elses bad repair is not easy at all.

You asked for the "best" way and got "super-best", take it all apart and put it all back together. Others here have done that with great results. The pros will also do that for almost the cost of a new handmade drum. It is too much for me also.

I have an old GB just like yours with the same problem. Someone tried to fix a split with epoxy and it opened up again. I have a friend, who repairs some of the finest old string instruments in the world, look at it. He advised a shim. That is, first clean out all the old glue with a V shaped tool (hand-made from a screwdriver) and get a long V shaped thin strip of mahogany (make it or buy from a specialty wood shop) and glue (Titebond) it in place. One of these days - (somewhere over the rainbow) that is what I'm going to do.
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Re: What is the best way to glue these cracks?

Postby Jerry Bembe » Sun Sep 18, 2011 8:17 am

Psych's method will work fine as well. There are many different options documented here and elsewhere on the web. I recomend epoxy because of it's strength but this can cause stress on the shell and this can split elsewhere or the wood can split.

A shim or filler will not create additional stress. There are many good glues to use. A low foam glue will be less messy. Tom Alexander at Volcano has recomended the use of epoxy for this type of filler repair and I consider him to be a pro compared to me and the most of us.

Regardless what method that is used, be careful with the glue. It looks like Kona is doing a nice job and will have good results. There is no best way just different opnions and this is good.
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Re: What is the best way to glue these cracks?

Postby Anonimo » Sun Sep 18, 2011 11:11 am

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Re: What is the best way to glue these cracks?

Postby Joseph » Sun Sep 18, 2011 3:28 pm

MHO

Remove ALL old glue from that broken seam. That includes all the excess glue on the inside of the shell. That extra glue has a very brittle quality to it and it will pop off fairly easily with a small chisel. It adheres excellently to the wood fibers, as you may see it pull off surface fibers of the wood as you chisel it off. From the photos you can see that the old glue, on the inside of shell, spans across the broken seam on the outside of shell. This may be preventing you from closing up the seam totally when clamping.

Also you can see little bumps of old dried glue on edges of broken seam. Make an effort to clean that up totally with sandpaper. Again, all those little hard bumps can cumulatively make it difficult to close up the seam.

Get your clamping apparatus together and practice clamping with a "dry fit". This will give you a little foretaste of what to expect: how much pressure will be needed to close up seam (or if it is even possible), and whether or not your clamping set up is adequate for the job. All this without having the complication or urgency of having to deal with messy glue at the same time. The dry run will tell definitively how wide a glue line you will end up with, and help make a decision as to whether or not to use a spline.

For a wide (Re)glue line I prefer a spline or shim.
Jerry Bembe wrote:Filler will be your safest bet. Use a filler that has a glue quality. If it shrinks then use epoxy to fill the fine cracks from shrinkage. Epoxy is the strongest glue to use but it can be messy.

I beg to differ. Filler is filler, it is NOT glue.

Epoxy glue has a property other wood glues do not: it is "gap filling", that is, it can retain 100% of its glue strength across a gap, thereby enabling one to have a strong joint with a wide glue line. Wood glues (like TB3) don't have these properties, and rely on close wood to wood contact on the joints.
The problem with most commonly available epoxies is that they are thin and "runny", and gravity may cause it to run out of the joint, unless the glue is contained. There are thixotropic agents like cabosil which thicken the mix and actually make it stronger, but ususally color the resin translucent white (the color of the cabosil).

It all boils down to aesthetics. Would you mind a big fat glue line?

If not, a spline or shim may be an alternative, but in order to get aesthetically pleasing results would require additional steps. The wood for the shim should be of the same variety as the existing shell wood, which is Luan, also known as Philippine Mahogany...but not really Mahogany.
As you can see from the pic of your shell, Luan varies greatly in color, even showing through the stain on your shell. The best results for overall finish would be achieved by stripping stain from shell, then glueing / shimming / repairing crack / sanding shim to be fair with shell surface, and then re-staining. By doing all the above you could end up with a very un-obtrusive repair, that blends in with the overall tone and color of the stain on the wood.

The shimming is a matter of individual fitting. After you have "dry fit" clamped your shell, the idea is to make the shim as thick as the remaining visible gap. It may take some tedious sanding and fitting to get it right (a beltsander is a must), but is time well spent. The more actual real wood you can use to fill the gap, the less it will look like a fat glue line.

For all these repairs I favor standard wood glue like Titebond3. As long as you can get get close fitting joints, it is more than strong enough, and cleans up with water.
If you have never used epoxy, I would not recommend it for your first try on a conga shell clamp-up.
Try practicing with it to get use to it's messy characteristics.

Again it gets down to aesthetics, do you want to just get it back together and functional again, or do you want to do a "restoration". Restoration work is a more time consuming.
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Re: What is the best way to glue these cracks?

Postby Psych1 » Mon Sep 19, 2011 6:40 am

My friend, master repairman, recommended 3 glues to me. Titebond 3 for the wood to wood fix, a very thin penetrating Titebond super glue for hairline cracks (I used it on a bongo for a great fix) and T-88 epoxy when a wood epoxy is needed. But I have never used epoxy so ??
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Re: What is the best way to glue these cracks?

Postby Jerry Bembe » Mon Sep 19, 2011 7:12 am

I would like to stress the point that the Gon Bops "Mahogany" drums do mark very easily. Previously, I have closed a crack successfully on a similar Gon Bops conga but the straps created impression marks on the soft shell from the pressure. Because of this potential issue, I favor filling a crack with a wood filler. If you stain the shell afterwards, the filler will be difficult to see.

Oak shells do not have this issue with straps marking the shells.

Joseph, you give excellent advice and communicate down to the details effectively.

Thanks
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