Which way does the natural bow of the wood go when neck making?

[Nick Sorenson]

Something I've long wondered, do I want the bow of the wood to face the back of the neck or towards the fingerboard when I'm blanking out a neck from raw wood?

My guess is that the bow of the wood would face the back of the neck since the string tension will pull it that way naturally. But I don't know. So I figured I'd ask!

thanks,
Nick

[Michael Lewis]

I really try to eliminate any bow in a neck until after the fingerboard is glued in place. If you referring to a natural bow in the wood, I would plane it flat and proceed with the process of making the guitar. You need only a few thousandths of an inch relief (forward bow) in the finished neck and that is with string tension.

[Nick Sorenson]

I do the same in getting it flat (jointer and planer). But more of what I'm wondering is the wood's "natural" curvature. Wood will always move a certain way due to the way it grew etc. It will have a 'tendency' built into itself from the way it grew. That's more of what I'm wondering... which way should that go?

[Mark Swanson]

In my experience you can't always tell just which way that is, and guesses are unreliable. I just build the best neck I can out of the best wood I can get and call it good.

[Michael Lewis]

The wood should be stable with no internal stress by the time it gets used. If the neck is changing shape it has not seasoned sufficiently or it was cut from unsuitable wood. Making guitars is not like building a house where you always put the crown up to help counteract the effects of gravity. In making guitars we always try for straight and true and should not need to plan for the effects of gravity. If it is not straight and true then make it so.

[Greg Robinson]

Nick, I take it you mean curve in the grain of the wood, not in the outside dimensions? Wood like this, when machined flat, will have run-out. I think you are focusing on the wrong aspect of this property, you shouldn't be considering which way it will bow, so much as whether it is useable at all. This will depend on the degree of run out, and the application, and it is a judgement call.

It's always a good idea to machine close to final dimensions, and allow the part to sit a while and settle into it's new shape.
Removing some parts of the wood will allow internal stresses to be relieved and it may change shape, to a greater or lesser degree, or not at all with well-seasoned wood. If you find that it's changed shape too much, you know you have bum wood, and it should be discarded. If after a while it is still close to the shape you cut, you can proceed with relative confidence.

Of course, you should always use well seasoned wood, but even with that, you will sometimes come across pieces containing large amounts of reaction wood and internal stresses, that just don't want to stay flat. It's the risk we take.

[Nick Sorenson]

Micheal, I'm not referring to wood changing shape. I'm talking when it's rough sawn there's usually a little bit of a tendency of bow in each piece of wood. It's something you'd need to measure with a straight edge and feeler gauges on anything I'd consider using for a neck but it's almost always there. It's rare that before I joint a rough sawn board, it's absolutely dead straight. This is what I'm talking about.

Greg, I probably should get my parts to closer to final dimensions. I've been planing the sawmill marks off and letting it sit in my shop for a few months. I suppose I should actually let blanks sit in the shop already jointed. That'd be a better bet.

[John Hamlett]

From my experience milling logs with a sawmill that I've owned since 1986, from my carpentry experience, from my cabinet building experience, and from my lutherie experience, my impression is that different species of wood have different behaviors when sawn from the log, when dried, when milled after drying, when milled after seasoning, and when built into final products. Add to that variation among pieces within a species, variations in drying procedures, differences in storage, differences in gluing, and so forth, there are few absolutes. We know how wood will react to changes in relative humidity, and to some extent we know how wood will respond to constant strain, but we must be specific (literally, each species must be considered individually) and we're talking averages then.
It's like others have said, try for a good quality piece of wood, well dried and well seasoned, make it straight, and don't worry about how it was positioned in the tree other than the traditions of grain orientation and lack of run out (there are good reasons for certain traditions).