Fixing a banana neck

Discussion in 'Setup & Repair [DB]' started by stevekendal, Oct 14, 2011.


  1. I have played electric bass for years :bassist: and I've just been given a double bass that has been stored in a cellar for ages. The neck has a massive forward bow to it that makes it almost impossible to play. I think this is a mediocre instrument to start with and probably not worth spending a lot of money on. I already slackened the strings off on the advice of a fiddling friend, but is there anything further I can do to coax it back into shape? I have some woodworking skills and hide glue, but if there is an easier way? :help: Steve.
     
  2. DC Bass

    DC Bass Supporting Member

    Mar 28, 2010
    Washington DC
    The scoop for the average upright can seem pretty drastic to an electric bassist used to very slight relief...

    At the very least I'd have an experienced upright bassist look at it, or better still a double bass luthier.

    Good luck, and welcome to the dark side! :)

    Joe

    PS- Don't slack the strings down too far or the sound post will drop- then it's a trip to the luthier for sure!
     
  3. ctregan

    ctregan

    Jun 25, 2007
    Syracuse N.Y.
    I repaired a badly curved neck on a bass, not too long ago. Here is what I did;

    Removed the fingerboard. If the neck is bending, there is a good chance the neck/fingerboard glue joint, has given out.

    Check the neck to see if it is straight. If it has a bend, it is possible to slowly bend it back straight by using heat, in the form of steam, and clamping the neck to a flat, ridged board. It may take a few days but, it can be done.

    Install a carbon fiber rod in the neck with epoxy and clamp it flat wile the glue dries

    Check tho make sure the fingerboard is flat. If it is not flat, and there is enough material on the board, join the underside of the fingerboard flat.

    Glue the now flat fingerboard, to the flat neck. This glue joint is what keeps the neck straight and ridged. Gluing a fingerboard on is a high skilled operation and critical to a successful repair.

    Good luck, I hope this helps.
     
  4. bssist

    bssist

    Jun 23, 2007
    St. Louis, MO USA
    I've heard this (or graphite) suggested but never heard the results. What effect will it have on the tone and/or sustain?
     
  5. powerbass

    powerbass

    Nov 2, 2006
    western MA
    You might want to have a pro luthier look it over. What may look like the neck is bowed could actually be the whole neck block/pocket is cracked or you may have serious rib/seam issues lower down causing a distortion or the fingerboard is too thin etc. This could be a major restoration time+materials+labor=$
     
  6. uprightben

    uprightben

    Nov 3, 2006
    Boone, NC
    The way to tell if the neck is warped is to hold a straight edge to the neck, FB joint. if the joint is not straight, the neck has probably warped.

    In the shop I work at we usually take the FB off, plane the neck flat, and if there is not enough wood left on the neck we glue a wedge on, flatten the underside of the FB with a plane and glue that back on. The flatness and fit of all of these joints are critical, as well as the alignment of the FB. Honestly, I would like to try the steaming approach that ctregan describes and avoid the wedge, but my boss won't hear of it.
     
  7. You can also tell if the neck is bent by sighting down the join of neck to fingerboard after stepping back behind the bass, leaning it back until you can see from the nut towards the bridge.

    Removing the old fingerboard can be tricky, depending on the sort of glue and how strongly it has held. Assuming hide glue, use a fairly sharp thin bladed old table knife lubricated with soap. The nut should come off easily with help from a light hammer blow. Start at the top of the neck and work the knife into the joint, only using very light hammer blows if really necessary. If the fingerboard is already loose it will be relatively easy to separate. Be careful not to turn the knife blade into the neck wood. You are trying to only break (wedge open) the glue line. If the glue is synthetic you may need help from a luthier, both to remove the board and to clean up the neck face with a tooth plane before straightening it and attaching the (new) fingerboard.

    With fingerboard off lay a wet cloth on the neck and create heat and steam by ironing it. If there are any traces of hide glue remaining they can be easily scraped off. Keep rewetting and ironing the cloth until you feel the warmth come right through to the back of the neck. Clamp a straight piece of 3x2 or 4x2 at each end of the neck but create a slight reverse bend over one or two thin pieces of wood in between (Match sticks or slightly thicker placed between the neck and flat wood) . Pad the clamp jaws to avoid denting the back of the neck. Allow to dry for several days, remove the clamps and allow the neck to settle back flat. Further plane only if necessary. Planing the neck without first straightening it will both weaken it and create a bulge in its thickness.

    If the removed fingerboard is bowed it should not be reused because it has already been weakened. A new board is cheap at the price.

    Yes, both the fingerboard and neck have to create a good flat dry fit. Before gluing them together clamp the fingerboard in position (after squaring up its top end for a good fir with the nut) and run a pencil line down each side. Plane most of the excess ebony off each side, leaving only a small amount to trim finally.

    There are more steps to go, obviously.THe main point I am trying to make so far is that a heated neck if only clamped flat to dry will come back to a slight banana. The reverse bend is necessary.

    I am going through this whole process right now.

    DP
     
  8. Cool Idea David will have to try this method.

    I have found in most (not all) occations the necks that do this are not great to start with either cheap timber or wrongly cut pieces some have been thined down so much that they can't hold the pressure of the strings anymore
    I have done the previously mentioned Graphite rod down the center which work fairly well, but in most cases I have had to do a graft.
     
  9. bssist

    bssist

    Jun 23, 2007
    St. Louis, MO USA
    What do you set the rod in with? Epoxy, as mentioned above, hide glue, or something else? What effect does it have on the tone?
     
  10. Very little other than epoxy will stick satisfactorily to carbon fiber. If you get it in glossy state, you also have to remove the separating agent from the surface and rough it up with sandpaper or something. I can't comment on the tone.
     
  11. Bssist I used west systems epoxy awesome stuff.

    Tonaly I noticed no real change maybe a slight clarity over before but it would have been so fractional, but even in electric necks I can't tell the difference between one with the rods and one without

    But I would have though that the point was strength not tone, I could be wrong maybe others have heard different.
     
  12. bssist

    bssist

    Jun 23, 2007
    St. Louis, MO USA
    The point is strength over tone. Tone is of utmost importance to me so I am curious about all the little nuances that different alterations create. We have a family friend who is a luthier and he frowns on anything being done to the instrument with materials other than wood.
     
  13. fraublugher

    fraublugher

    Nov 19, 2004
    ottawa, ontario, canada
    music school retailer
    To me , graphite/carbon fiber is a trade-off , it will give stability and possibly more note clarity , but it acts like a large clamp would act attached to the scroll , preventing/deadening some vibration of the instrument .

    Good luck with the repairs,
    John
     
  14. Jake deVilliers

    Jake deVilliers Commercial User

    May 24, 2006
    Crescent Beach, BC
    Owner of The Bass Spa, String Repairman at Long & McQuade Vancouver
    The CF bar adds no weight, so all you get is more stiffness. CF in the neck will add presence and power to the sound of the bass - more highs and more clarity. Double stops are noticeably better defined and sustain increases. Stiffening the neck keeps it from absorbing vibrations - they are conveyed more quickly and completely to the top.
     
  15. Quite the reverse; carbon fiber is a very 'live' material, because of its very high stiffness. The problem with carbon bows is damping them enough, rather than getting liveness.

    Carbon parts, particularly rod and tube sections, tend to 'ping' if you flick them. So I'd expect stiffening the neck to do as Jake suggests, brighten the instrument and add power.
     
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