A few weeks back Mrs. Devil bought me a Make Your Own Cajon kit. A cajon is a simple box drum (though not simple to play). This style is a rectangular box with an off-center divider in it to make two tones (i.e. a bongo cajon).
It went together fairly easily. I wasn’t excessive with the glue (but not stingy), clamped the heck out of it where I needed to, used putty to fill in small gaps (none went through to the other side), and have sanded it so that it’s ready for staining. But one side sounds off.
In words, the good side has a nice, hollow, pleasant ring to it. The ‘bad’ side sounds as if there is a loose joint somewhere, or as if the face isn’t fully glued down. But I’ve looked at all sides and can’t see (even wearing magnifiers) any space between any surface. No light leaks through whether the source is inside or outside the resonating chamber. It looks and feels solid, but doesn’t sound solid. Here is a ten-second clip I uploaded to TinyPic.
Mentally divide the edges of the top surface into six segments, as shown below.
… _ _
“off” side I_ _I “solid” side
One at a time, tightly clamp each segment from top to bottom and see if that changes the tone. If it doesn’t, or if it changes it some but not enough, try clamping two or three segments at a time, especially on the “off” side.
If you get the desired tone this way then something – probably the top – isn’t solidly attached. If not, look elsewhere for the problem. Perhaps it’s related to the divider?
Once I find a segment/area where clamping makes a difference, what’s my next step? Is there any way to reinforce the joint? Injecting glue and reclamping? Adding a brace? Or am I looking at pulling the top off and starting over?
I am not a woodworker, so someone else may have better information or advice.
Since it doesn’t look likes screws would fit, or be desirable aesthetically, I’d be inclined to remove the top. I’d get the underside of it, AND the top perimeter of the four sides where it attaches, as perfectly flat as possible. Then I’d reglue with appropriate clamps or weights.
Is it just the snare or some other internal part rattling?
What kind of glue did you use? You may be able to get some part of a joint that’s not tight to stick by just clamping it for a while. Unless you can see the open void I don’t know how you can effectively add more glue.
Heh, I want to hit it—but I don’t want it to rattle!
Also, there are many cajons with snares or other bits inside to add flourish; this is not one of them.
Glue was Elmer’s yellow wood glue. It’s been dry for a long time now, so merely re-clamping won’t quite work.
I can’t think of a way to rip the top off without completely mucking it up. I could technically rip it off by putting it on the bandsaw, but that seems pretty Draconian.
There must be a joint that is not sufficiently bonded. If you can identify the joint your choices are to either carefully disassemble the joint in question and re-glue it, mechanically reinforce it, or to use a specialty glue that will flow into the gasp of the weak joint and fill it.
The latter has the least risk of damaging the project, the first has the most likely hood of success. For the latter I would try either a chair repair glue or a cyanoacrylic glue (crazy glue)that will be effectively drawn into any gaps.
Call Meinl and see if they can give you guidance, both for the sound problem and how to disassemble the glued joint if necessary.
My thought is to carefully insert a sturdy sharp blade that I can tap on with a hammer to try to cut through the glue. This type of utility knife blade is sharp enough, thin enough, and strong enough, though it’s a pain to work with in this way. A gasketscraper that resembles a putty knife is easy to work with if it’s thin enough, sharp enough, and strong enough, but these can be hard to find. The to-be-glued-again surfaces would need some serious sanding (or planing?) to be flat and level enough to go back together properly.
If you do decide to take it apart and re-glue, I’d recommend using Titebond (either II or III), rather than Elmer’s. Or you can use a two-part epoxy if the gluing surfaces are too small for a wood glue to be effective. Whether you use a five minute or a 20 minute depends on your confidence/competence level.
With most carpenter’s glue you can steam the glue loose,except Titebond 3. I’d try to isolate the problem using the above technique of clamping first though.
Dunno – my thoughts on watching the video was “It’s not supposed to sound like that?” First thing I’d do is check and make sure that’s not just how the drum is tuned.
Are the rubber feet on? Could one of the screws be hitting the surface of the table?
You may be able to disassemble the joints with heat (and possibly water, but that would stain the wood). You won’t see any noticeable difference between Elmer’s and Titebond – they’re both PVA glues and perfectly suitable for this application, although purists would probably use hide glue for musical instruments.
Titebond has an ANSI rating for water resistance, but yeah, it’s a matter of personal preference. Looking at the cajon website link, those thin edge joints just scream for a mechanical attachment like nails or screws, or perhaps some ‘L’ brackets inside the box. Most of your glue probably just got sucked into the porous edges of the ply. Even with screws, I’d be worried about them tearing out that material. I’d probably go with a 20 minute epoxy plus screws, although cleanup with epoxy can be a PITA.
I have tack hammers and pneumatic nail guns at my disposal, but my skills with either aren’t sufficient to drive a nail in thin, angled plywood without coming through one side of the walls. Of course, I haven’t tried yet, so maybe I should muck about with some test pieces to test that.
If I try the chair repair glue or crazy glue route, would I be making it harder or more risky (e.g. splintering the wood) to try and take it apart to redo?
Here’s what I think happened and why it only looks like it’s fully sealed. The top had a very slight bow to it when I was fitting things together, but I counted on the strength of the bond to hold it flush. Given Chefguy’s last comment about the glue seeping into the edge of the wood, my thought is that after I removed the clamps (+/- 20 hours), there wasn’t enough glue to fully hold the top down—the bow pulled up just enough so that the top is at an angle inside of the far side (crude imgur drawing).
Does that give me hope to inject/force glue from the inside to seal it up?
If it makes a difference, I’m shifting a bit finish-wise to make things a bit easier. Instead of one stain, I’m going to stain the top and body different colours, and use a decorative or complementary edge banding at the top. That should give me some tiny flexibility with glue stains on the wood.
Contacted Meinl, waiting to see if they have anything to add.
From your description, you may be SOL. The width of the glue joint may not be enough to withstand the spring tension of the bowed ply material. In any case, I wouldn’t use super glue for much of anything, let alone a wood joint. I’m not sure how you clamped this, but if there is a bow in the ply material, I’d lay a couple (or more) pieces of one-by or two-by sticks across the entire width to help flatten it, and then clamp the glued joint with four screw clamps (not those Irwin clamps you get at HD), and hope that it holds.
Would it affect the instrument if you put a permanent brace across the middle of the bowed piece? If you could screw a piece of 1x2 across that area, it might solve the bow problem.
You could also try to weigh down the piece on a flat surface (in a heated space), first dampening the concave side, and see if that flattens it out. When my cutting board gets a bow in it, I wet the concave side and heat up the other side with a hair dryer. It usually will straighten it out over the course of a few hours. If it’s really badly bowed, I’ll take it outside in hot weather, wet the grass and set the board on it. It’s like magic.
When viewing your video, which side has the snare? The snare is supposed to provide a slight rattle like a snare drum.
Assuming you followed the the instructions provided on their site, I doubt that you’d have much rattle even if you only used screws. You’re not hitting it that hard.
That is a good point. The website for the product says the material is Baltic Birch. Looking at the pictures it quite obviously is Baltic Birch Plywood which is a high grade plywood and typically has few if any voids. The cut edge of Baltic Birch is often bullnosed and used as a finished edge for things like drawer boxes because of the lack of voids. When I have found voids in it they are usually very small and I doubt would produce a rattle though.
I would still try the chair glue. The ‘crazy’ glue is of course not typically used for wood joints because it is so thin, however in this case its function is to be drawn in to fine gaps and bond them and that is where it shines. That is why it is used to fix stone chips in windshields. If the glue does not work, yes it will make disassembly even more difficult.
Part of my job is actually restoring cabinets and built-in woodwork. I often replace damaged components of woodwork where possible rather than replacing whole assemblies. A well glued joint can be very difficult to take apart, but I will at least try first. Carefully working the joint with a olfa cutter, putty knife and glazing bar to get it open is the basic approach. I would then re-mill the surfaces to get them to good bonding condition.
Looking at the pictures, the joints appear to be simple butt joints. If changing the dimensions of the object by 1/8 - 3/16" inch is not going to be a big problem I would simply cut the offending side off the box with a table saw. Set the table saw so the blade is just barely higher than the material thickness and cut through the joint. Eighteen gauge brad nails are not a problem but do not use your prize blade. Use a sheet of sacrificial hardboard of MDF underneath to minimize tear-out. You should be left with nice clean joint surfaces, if not reset the saw as necessary and run the pieces through again to clean them up.
On my way out—I’m not seeing ‘chair glue’ at either of the box stores or on the Ace page. Is it a particular brand or are there generic terms I can search/ask for?
