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Questions about Cocobolo
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=42789		 Page 1 of 1
Author:  Mark L. [ Thu Feb 20, 2014 1:51 pm ]
Post subject:  Questions about Cocobolo
I am starting a Cocobolo/Lutz dreadnaught build and I have a few questions. What would be a good back and side thickness, and bending temperature, in order to avoid side cracking and undue weight. Any suggestions on bracing material, and nut and saddle material to avoid metallic tone. Since Cocobolo is so oily, any suggestions on glue type to use to insure strong joints. I'm thinking about using Target EM6000 instead of nitro because of it's fast cure time, but I'm wondering about adhesion problems with Cococolo. Can you use EM6000 on top of Zpoxy? I've never built with Cocobolo before, so your suggestions are truly appreciated.

Thanks,
Mark L.
Author:  Joe Beaver [ Thu Feb 20, 2014 2:09 pm ]
Post subject:  Re: Questions about Cocobolo
Cocobolo is a heavy but excellent tonewood in my opinion.

I do the sides at something like .085 to .09". The back is left at around .095 to maybe .10". After final sanding it is around .005" less.

I wipe the surfaces with DNA just before gluing with titebond. Seems to work ok

It bends pretty much like other rosewoods. I make up a sandwich with wet paper, heating blanket and tin foil and heat. I set my blanket for 305 degrees. When it gets to 250 and has started steaming I begin to bring the waist in. Then bend the lower bout and follow with the upper.
Author:  Rodger Knox [ Thu Feb 20, 2014 2:13 pm ]
Post subject:  Re: Questions about Cocobolo
Coco is a nice wood, but do take precautions when working it because it is a sensitizer, and many people develop a sensitivity to it (particularly the dust) very quickly. Of course it depends on the wood you have, but I wouldn't go any thicker than 0.08" for the back and sides, maybe as thin as 0.06". IIRC the coco that I bent needed quite a bit of heat, but not much moisture, and bent pretty easily.
Don't wipe with acetone or anything else prior to gluing, that actually brings more oils to the surface and makes gluing more difficult. Lightly scrap or sand the gluing surfaces just before gluing, and glue with HHG or Titebond I.
No advice on finishing, I brushed on the old Rockhard varnish.
Author:  Joe Beaver [ Thu Feb 20, 2014 3:37 pm ]
Post subject:  Re: Questions about Cocobolo
As far as finish, I use ktm-9 over epoxy. It works well. I have never used em 6000 but I'm guessing it will be fine. As with any water base just don't spray to heavy and let it dry adequately between coats. (Avoiding the dreaded blue cast]
Author:  johnparchem [ Thu Feb 20, 2014 3:48 pm ]
Post subject:  Re: Questions about Cocobolo
I have used zpoxy on cocobolo and EM6000. I usually put blond shellac between the zpoxy and the EM6000. I do for color reasons not for adhesion, but I do have experience with 6 instruments using zpoxy and em6000. I really like the combo.

I agree with Joe about thin coats. I use a mill gauge and keep the wet coats to 3-4 mills. I check every coat.
Author:  lactose [ Fri Feb 21, 2014 11:40 am ]
Post subject:  Re: Questions about Cocobolo
Last week I glued rosewood binding to a cocobolo fretboard. You know you get a lot of different opinions on how to deal with this wood on the forums and internet. So after reading a bit, I roughed up the cocobolo fretboard edge with some sandpaper, the wiped and re-wiped with raw acetone (the kind without the conditioners in it) until the amount of oil coming off onto my rag seemed to diminish. I glued the binding on with CA, so far so good. I supposed that a year or two from now I will see how successful I was.

I will need to do this again when I glue the fretboard to the bamboo neck.
Author:  sdsollod [ Fri Feb 21, 2014 11:53 am ]
Post subject:  Re: Questions about Cocobolo
I have used EM6000 with Zpoxy and haven't had any issues...
Author:  Rodger Knox [ Fri Feb 21, 2014 12:18 pm ]
Post subject:  Re: Questions about Cocobolo
lactose wrote:
Last week I glued rosewood binding to a cocobolo fretboard. You know you get a lot of different opinions on how to deal with this wood on the forums and internet. So after reading a bit, I roughed up the cocobolo fretboard edge with some sandpaper, the wiped and re-wiped with raw acetone (the kind without the conditioners in it) until the amount of oil coming off onto my rag seemed to diminish. I glued the binding on with CA, so far so good. I supposed that a year or two from now I will see how successful I was.

I will need to do this again when I glue the fretboard to the bamboo neck.


It won't take a year to find out, six weeks to three months will probably tell the tale. Binding has no real stress, and CA works pretty well on oily woods.If it makes it a year it'll be OK.
The acetone is a solvent, and will remove most of the oils from the surface. However, it also seeps into the pores and disolves some of the deeper oils, which rise to the surface to replace the oils that were removed. This happens after it is glued, and could be anywhere from a couple of hours to several months.

A freshly planed or scraped surface provides the best gluing surface for glues commonly used for instruments (HHG, Titebond, fish, not sure about CA). A freshly sanded surface is almost as good. That's probably one of the few things that experienced luthiers will agree on.

Epoxy and PVA are different, and may have some good application in instruments, but I don't use them.
Author:  JasonM [ Fri Feb 21, 2014 4:17 pm ]
Post subject:  Re: Questions about Cocobolo
Probably overkill, but I use West Systems epoxy, with some 80 grit roughing up, for any joinery with Cocobolo (except bindings- CA there). Had a coco guitar left in a hot trunk, to the point the case printed heavily into the finish, but none of the glue joints let go.
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