Neck Grain Orientation

Discussion in 'Luthier's Corner' started by LightGroove, Mar 3, 2014.


  1. LightGroove

    LightGroove

    Joined:
    Oct 24, 2006
    Messages:
    2,177
    Location:
    Happy Bottom, VA
    Greetings,

    Im putting together a neck for an upcoming build and would like some advice. For the neck Im going with a 5 piece Hard maple, cherry accent, White Wenge center, cherry, maple. For the maple I purchased a 4/4 board and ripped it down into 2 pieces. Now Im wondering which way to orient the pieces to be structurly the best. After ripping the Maple it did develop some bow that I think/hoping will cancel itself off with the lams.

    Here are 2 pics I snapped. Which is the correct way for the Maple?

    Pic 1: The grain run toward the center.
    Pic 2: The grain runs away.

    It seemed like the bow was all but reduced when set up with option 2. Not sure if that makes sense.
     

    Attached Files:

  2. mrz2u

    mrz2u

    Joined:
    May 10, 2012
    Messages:
    73
    I vote #2. That wenge is not going to move much if at all on its own. The strings will pull on things a bit and I think that back bow will be best negated with the grains running towards the center but then again, thats why you have a truss rod :)
     
  3. Lonnybass

    Lonnybass

    Joined:
    Jul 19, 2000
    Messages:
    2,289
    Location:
    Minneapolis by way of Chicago
    Disclosures:
    Endorsing Artist: Pedulla Basses
    Which way is going to be "up," fingerboard side?

    Lonnybass
     
  4. Hopkins

    Hopkins Supporting Member

    Joined:
    Nov 17, 2010
    Messages:
    7,557
    Location:
    Houston Tx
    I think either way would be fine stability wise. I think option two would make for a more interesting grain pattern after carving.
     
  5. Register to disable this ad
  6. LightGroove

    LightGroove

    Joined:
    Oct 24, 2006
    Messages:
    2,177
    Location:
    Happy Bottom, VA
    I was thinking as they sit..so fingerboard would be on top of each of these looking straight ahead
     
  7. Bruce Johnson

    Bruce Johnson Supporting Member

    Joined:
    Feb 4, 2011
    Messages:
    1,170
    Location:
    Fillmore, CA
    Disclosures:
    Professional Luthier
    It's not a big difference between the two orientations that you have shown, but I always build my necks as you have shown in image #1.

    When you are looking at the end of the strips like that, you are seeing the growth rings of the log. They are portions of a group of concentric circles, so imagine what the full circles would look like.

    Picture:
    1.) Where the center of these circles would be. That would be the center of the log that the strip was cut from.
    2.) How large these circles would be; how close to the center of the log are these strips.
    3.) Look at the spacing of the rings; how much difference there is in the spacing of the rings from one side of the strip to the other.

    Here's what it means:
    As the wood dries out over time, it will slowly contract. If it gains moisture suddenly, it will expand. This contraction/expansion mostly happens along the length of the strip.

    Where the spacing of the rings is widest, that's where most contraction/expansion will happen. That is, the wood closest to the center of the log is the driest and most stable, and will move the least. The wood at the outer diameter of the log is the wettest and will change length the most.

    So, looking at the rings on the end of the strip, the more difference there is in the spacing of the rings from one side of the strip to the other, the more difference there will be in the amount of contraction/expansion along the length, and therefore, the more the strip will bend as it dries out.

    The bending will happen along a radial line. If you draw a line from the imaginary center of the log out across the end of the strip, that is the direction it will bend.

    For example, looking at the left strip in your picture #1, as it dries out, the far end of the strip will move to the lower left, in relation to the near end. That's how it will bend.

    The right strip is the opposite; the far end will move to the lower right.

    How much each strip bends will be related to the difference between the spacing of the rings across the strip. If the rings are equally spaced, it won't bend much at all. If the spacing is wide at one side and tight on the other side, it will bend the most.

    The critical thing is balance and symmetry. You want any long term movement of the wood to be balanced by opposite movement on the other side. As they are positioned in picture #1 and picture #2, they are balanced. The movement of the left strip will oppose and counteract the movement of the right strip. Both of those orientations are fine.

    What you don't want to do is orient the strips so that the movement is helping each other. For example, if you took the right strip in picture #1 and rotated it 180 degrees, the center of its rings would now be off to the lower right side of the neck. While the left strip's center would be up and inboard. That would be a disaster in the making. A neck built like that is almost guaranteed to twist badly.

    The ring orientations in pictures #1 and #2 are both okay, but #1 is preferable. The reason why is that the movement in #1 will be in the backbow direction. So the movement will be resisted and counteracted by the tension of the strings. #2 will tend to bow forward, so the string load will be helping it. #2 will need a little more truss rod cranking as it ages.

    It's hard to describe all this without drawings and arrows, but I hopes this helps. Wood dies slowly, and it all moves. Building bass necks that stay straight is all about understanding and balancing that movement.
     
  8. Jensby design

    Jensby design

    Joined:
    May 22, 2008
    Messages:
    839
    Location:
    Hastings, NE
    1 will be more stable.
    2 will look better.
    You also need to consider the grain direction on the sides and which way it slopes.
     
  9. LightGroove

    LightGroove

    Joined:
    Oct 24, 2006
    Messages:
    2,177
    Location:
    Happy Bottom, VA
    WOW! Thanks Bruce. Wood is so fascinating I have to say.

    I have some understanding with this process as I harvest and dry my own lumber. Im an avid bowl turner but a lot of that is turned in the green state and then left to dry. I was not clear on the particulars but this REALLY helps. I may have to read and reread your post a few times :D

    I was a little hesitant as the maple I bought was kiln dried to 6%. Im already seeing it move after having it sit for a few days in my work room. Now its moving again that I cut it (which I expected.)

    Should I let it finish moving/adjusting to my workroom before gluing it up?
     
  10. Bruce Johnson

    Bruce Johnson Supporting Member

    Joined:
    Feb 4, 2011
    Messages:
    1,170
    Location:
    Fillmore, CA
    Disclosures:
    Professional Luthier
    When I build my necks, I start with kiln-dried maple boards, which are normally around 6-8% moisture. I immediately cut them into 1 1/4" square strips, watching carefully to get the rings oriented in matched sets, and keeping the rings and grain lines straight down the length of the strips. These strips are all matched and dated, and then I store them in a rack here in my shop for about a year.

    During that year, some will bend, some won't. That's where I've gotten my knowledge about how much and which direction they will bend. If they bend more than 1/8", they get discarded or used for some less critical purpose.

    The strips now get cut to flat in a special routing fixture, not in a planer. This is important. The routing fixture holds the strips in whatever curved condition they've ended up in, and the router trims away wood to make them flat. A planer will push the strip flat as it cuts it to equal thickness, but then it springs back into a curve when it comes out the other end. When I set up to do the glue up of the strips, they should all lay up flat and true against each other. I never push bowed strips together with the clamps.

    If you haven't seen it before, here's a series of web pages of mine from around 2008, showing the whole process that I go through building my Scroll Bass necks. On the first two pages you can see how I cut and orient the strips, rout them flat, glue them up, etc.

    http://www.xstrange.com/Building/Buildingneck1.html

    I've improved and upgraded some of the fixtures over the years, but most of the process is still the same. Yeah, all those little details are a lot of extra work, but these necks go into $4500 basses, and I'm building them to last at least 50 years. I've been building these basses for 18 years now, and I haven't yet had one twist, bow or split.
     
  11. StuartV

    StuartV Out of GAS!! Supporting Member

    Joined:
    Jul 27, 2006
    Messages:
    5,106
    Location:
    Bristow, VA
    OT question from a woodworking newb: Isn't that exactly what a jointer is for?

    I understand that it's probably a lot less expensive to make up a fixture and use a router, than to buy a jointer. I'm not trying to knock the way you're doing it. I'm just trying to confirm my understanding of the various tools of the trade and how you use them.
     
  12. HaMMerHeD

    HaMMerHeD

    Joined:
    May 20, 2005
    Messages:
    3,208
    Location:
    Norman, OK
    Sort-of. A jointer would work well for what is being described if the board is very large and heavy. Stock must be pushed down and fed across the cutter with consistent pressure for a jointer to be most effective. When doing so with smallish stock (such as the 1.25" squares that Bruce uses), the pushing/feeding action itself would bend the stock straight, which would defeat what you are trying to accomplish.
     
  13. Bruce Johnson

    Bruce Johnson Supporting Member

    Joined:
    Feb 4, 2011
    Messages:
    1,170
    Location:
    Fillmore, CA
    Disclosures:
    Professional Luthier
    HaMMerHeD answered it for me, thanks!

    Yes, I have a nice jointer and a planer in my shop, and I use them for flattening out larger boards. But for neck lamination strips, the strip will spring too much going through either a jointer or a planer, so it defeats the purpose. The router fixture holds the strips still, with their natural curve, while they are cut flat. You could build a similar sliding holding fixture that could be used on a jointer or a planer, to do the same thing. I like the router fixture because it's fast and reliable.
     
  14. LightGroove

    LightGroove

    Joined:
    Oct 24, 2006
    Messages:
    2,177
    Location:
    Happy Bottom, VA
    Thanks for the info and the link. Can you expand on the router fixture as Im not totally understanding it? Do you have all 3 pieces in there sandwiched together and then "route" them as one unit? What type of bit do you recommend? Could you provide details of components? (perhaps through pm if necessary).
     
  15. StuartV

    StuartV Out of GAS!! Supporting Member

    Joined:
    Jul 27, 2006
    Messages:
    5,106
    Location:
    Bristow, VA
    Got it. Thanks, HaMMerHeD and Bruce.
     

Share This Page