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I got a macassar ebony fretboard from a local supplier that has a very slight cup in it... will it affect things if I put it on the neck? The cup seems small enough that it can be planed out but the fretboard is only 1/4" thick. I have placed it under a lot of weight and sticker hoping that it will improve...

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

hi tai.
i would sand or plane the bottom (concave) side, and glue it on quickly so it doesn't cup anymore.
pre-radiused fretboard!

I can't do that now... I don't even have a neck made up for it and it would be difficult to slot the fretboard if it's glued on. I placed it under a lot of weight to flatten it... hopefully it will.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I would say about .01"

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I think it would work, sanding/planing the bottom flat. You can still slot it before gluing it on. The bowed top side shouldn't cause any trouble in slotting after the cupped side is flattened out.

The fingerboard blank I wanted to use for my current guitar had a bit of a twist in it. I tried soaking it overnight and then clamping it flat, but it always returned to its same shape. I eventually just planed it flat (it had some extra thickness to work in) and now over a month later it's still nice and flat, and I haven't gotten to gluing it on yet.

But if you're not going to glue it right away after flattening the bottom, then let it sit loose for a day or two before you flatten it, to settle into its happy shape where it won't move again later.

Also, you might want to glue it on with epoxy or other non-water-based glue, for fear of it cupping its way out of a solid joint when it absorbs the water from the glue.

how do I plane the fingerboard blank flat? If I am using a safe t planer then I have no flat underside to rest on, if doing it by hand, I have no idea how to ensure a consistent thickness. Right now its clamped between a flat wooden shelf and a cement block with 3 cam clamps and a C clamp... it will hopefully force it flat after a few weeks. As for using epoxy to glue fingerboards, what if I need to remove the fingerboard later for repairs? epoxy doesn't release with heat unless its very hot (hot enough to burn the wood).

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Yeah, it would be a pain to plane flat with a hump on the other side. Probably better to sand it. Maybe draw all over it with a pencil and use that as a visual reference for where the sanding has gotten to.

And epoxy would be permanent. If you think you'll ever need to take it off, then something different would be better. You could try putting a little water on the glue side (after flattening it) and check if it warps, to see if it would even be a problem. I don't know any reversible non-water glues though, so I'm not sure what to do if it does warp badly.

Most epoxy will release just fine with heat and most at a lower temp than TB2, its just a bit slower tis all. I would not panic about the FB right now, given the climate in Taiwan its probably just an RH issue. Flip it concave down and let the other side dry out more while you get on with the neck. By the time ur done that FB may be flat again or even cupped the other way.

Cheers

Kim

Yea, that's one of the biggest issue in Taiwan... it's always over 90% at all times of the year. I really envy people who lives in a dry environment who doesn't have to pay a lot in electricity to keep the rh down. Its very hot and humid in the summer and pretty much anytime is a bad time to paint due to the extremely high RH. Consequently any wood I buy in Taiwan isn't "dry" because to them dry is a relative thing... but when the prices of wood component is a difference between about 60 dollars and 500 dollars (that is how much a LMI kit cost when you add shipping and custom) any work to season or dry wood properly is worth it. I pretty much assume that any wood I buy in Taiwan is green, even if they said it was kiln dried.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Even dry well seasoned wood is going to move around on you because at 80 or 90% RH, dry wood will absorb moisture and as soon as the RH lowers it will expel it again as it tries to come into equilibrium with the ambient conditions. This is what has probably caused you FB to cup. When you picked it up it may have been dry, but at the same time use to an ambient of say 70% RH. When you got it home the RH in your shop may have been lower, say 55% and if you set the FB flat on a bench it would have prevented moisture from escaping on the underside yet allowed moisture to escape from the top surface. This would caused temporary shrinkage of the top surface and result in cupping.

My guess is that if you flip it over it will become flat once again as moister escapes from the other side of the FB. Once it is flat again, if you sticker the FB so that air can get to 'both' side of the wood, it should be fine.

Cheers

Kim

right now, its stickered and under a lot of pressure to flatten the piece... the wood appears to have been this way when it arrived. I have my bedroom dehumidified at approximately 60-55% rh to keep the room comfortable during the hot summer months and also to keep mold out of my carpets. So I will also store those moisture sensitive wood and do any gluing operation in my bedroom. The place I do any bulk wood processing has no RH control because it would be too expensive.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I would unsticker it for now, place it on a flat bench concave down, and let the drier air get to the convex side, this will be quicker than trying to squash it flat. Once it flattens out, then just sticker as normal and it should be OK as long as the wood does not have too much cranky grain.

Cheers

Kim

Perhaps it was still a bit wet when it was cut to size at the suppliers.
If you want to use the safety planer to flatten the concave side, just use strips of masking tape layered along the sides of the other face to shim it to the same height as the centre, then it will be stable

Ok, I wet the concave side and placed the wet side face down on top of my flat table, and within 30 minutes it flattened out (in fact it looks like it was threatening to cup the other way) so now I just stickered the whole thing to prevent it from distorting again. The whole fretboard is also bowed lengthwise from the other side but this isn't as serious as a cupped fretboard... that can always be adjusted with a truss rod or by fretting...

But a comment about this fretboard... it's about 45 degrees off quarter... I guess I am not all that concerned because as far as I know most Gaboon ebony are flatsawn anyways, the bridge blank is quartersawn however. I do like the look of Macassar ebony better because it looks far more interesting and I would like to use it in future builds... it has all the strength of ebony and looks good to boot. I do like to be able to get Gaboon ebony in Taiwan though... incase I have to repair a guitar because most of them would use gaboon ebony. It's just weird that its easier to get Macassar in Taiwan because that kind of ebony is always seen as a premium ebony. I guess its due to the proximity to Indonesia...

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Haven't read all posts, so maybe I am repeating.

If you are gluing with a water based glue, some people deliberately make the contact side concave, to compensated for swelling when the glue is applied.

If you really want to flatten a fingerboard, you can heat it. What I did years ago was got a couple of 1/4" steel plates, heated them in the oven, clamped the wood in it, put it back it the oven for some hours, let it cool overnight, took it out and left it several days before unclamping. The result was dead flat and never warped again, even though I did not use it right away. What I did was overkill and I do not do it anymore.

Well, the cup was small but the bow was more like 1/16" which isn't an issue because that can always be fixed by fretting or truss rods. In any case I wet the fretboard on the concave side and now the cup is almost undetectable. I have it under heavy sticker and weight to make sure it doesn't do that in the future.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

belt sand, thickness sand or even hand sand the sucker flat if you don't feel good about planing it down.

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Audiences and dispensations on Thursdays ~ by appointment only.


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Side to side cupping is a judgment call, but I'd pencil the bottom and then lap it flat on sandpaper on a true surface. You can look at the bottom and adjust pressure to be sure you're coming in from both sides evenly.

Lengthwise bowing is generally a complete non-issue unless it's extreme, just another strawman in waiting. In nearly all cases, the lengthwise bow can be taken out with light finger pressure...which means that the most distorting force it can exert on the neck is equivalent to light finger pressure. If the rest of your neck can be distorted by a few grams of pressure then the fretboard isn't the problem, and you'd better keep that two hundred pounds of string tension away from it.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services