www.StringRepair.com - "Prescott" Double Bass, c. 1830

DOUBLE BASS REPAIR

 REPAIR #10


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"Prescott" Double Bass, c1830

Every pet owning bass players worst nightmare!  Dog hits bass A, knocking it over.  Bass A hits bass B.  Bass A's scroll ear smashes into bass B's upper ribs.  Bass A (German factory bass) is fine while bass B (1830's "Prescott") takes a ride to our Mystic, CT shop to repair the damage.

In repair page one we repaired a smaller rib hole/crack very successfully.  This is a much larger hole, but it will blend quite nicely.  All the pieces were there and went together without too much convincing.  A maple veneer along the inside will give all the support it needs.  Touchup was a bit of work mainly because we had to make our existing varnish opaque to match the surrounding varnish.

The real problem is the scroll.  Upon first inspection it was deemed by us to be unstable.  The owner bought this bass 18 years ago and noted the cracks and brass pins, so he put some pencil lines to see if the cracks would travel.  Eighteen years later, the pencil lines show the cracks have not traveled.  But when we took off the plate tuners, everything just started falling apart!  It is a miracle that 1) this scroll was not buzzing beyond belief in the owners ear and 2) the scroll has not just snapped off!  This neck and scroll though are what we call "Frankensteined" together.  The neck length was shortened by way of a lap joint and hardware.  The neck heel had been lengthened to ad more over stand.  The fingerboard had been reverse shimmed to decrease the projection.  The neck heel has been shoed twice in attempts to raise the projection.  The neck set mortise is very shallow and only lag bolts hold it into the block.

Obviously years of repairmen have brought this neck back and forth.  It is time for a new neck and scroll graft!

We x-rayed the scroll to see just what we were in for.  About 35 nails will need to be removed before we start to carve, if we go that route.  There are two possible repair route's to take:

#1)The scroll will need 8 bushings and cheek grafts.  The inner wood of the peg box walls will be replaced with the neck graft, and the outer portions of the peg box walls will be replaced with the cheek grafts.  Just a thin amount of original wood will remain in the middle (although most of this wood will be bushings).  In the end the scroll will have  maintained our goal of conservation of original material when allowable. 

#2)The volute will be grafted onto a new neck & pegbox.

Our goal is always the preservation of original material.  Even though this scroll shows much evidence of not being original to the maker, we decided to preserve the story it tells, and have elected to proceed with repair route #1.

The string length is currently set at 42.5" and we shortened it a bit to 42".  The projection is about 7 inches and that too will remain.  The over stand is currently 6.5mm (this is spec for a violin, not a bass) and that will be corrected to 25mm.  This will change the angle of the strings over the bridge and thus reduce some of the string tension on the top, as well as make for a more comfortable playing instrument.  A new neck block will allow us to set the neck deeper, thus adding the strength to the mortise that is needed so that the lag bolts can be abandoned.  Originally the pegbox walls were too thin at the base and were not load supported by the neck.  This caused the pegbox to crack along the floor.  The scroll graft will allow us to carve thicker pegbox walls that (inside edge) extend into the neck.  This will put the load of the pegbox walls onto the whole of the neck and help to prevent future failure.

At the last minute we decided not to install the original tuners back on the bass (they were brittle and had as many repairs and patches as the scroll had).  Not enough time (and money) were left, so standard German plate tuners were installed with an offset orientation to take some pressure off the scroll.

The bass finished out very well and was out to gig with the owner the first day it was picked up!


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  Amazing this was not causing MAJOR problems! Glueing up the crack. Close up of lap joint done by previous repairmen to shorted the neck length... OK.  Things start getting scary, and this scroll is alot worse than we thought! This piece just pulled off with finger tension.  No knife, water or alcohol needed. The entire scroll had been decapitated in the past and reglued.  It took only finger tension to pull things apart... This back piece, not original and made of mahogany, came off with very little effort... see...oh, so much more work than we would have ever thought. piecing it back together... All existing pieces back together.  There are some small pieces that are missing, so we will have to inlay new material... Inside view of the crack... Pieces inlaid, wood leveled...ready for touchup... close up of the inlay... Cutting out the neck.  We didn't want any more rib cracks or chipout... Past repair?  This little piece just popped out with the block... Notice the years of accumulated glues, not all of them hide! A couple of splits to help get it out... No idea what glue this was, but it killed my openning knife... rough fit, ready for chalk fitting... Neck measurements are carefully drawn as reffrence points to where the bass was.  The projection needs to stay the same, but the overstand will increase, thus changing the neck angle.  We also need to carve the new neck so that the throat of the heel is the same as it is now so that the owner does not need to "re-learn" his instrument. just working things out.  It's good to know where you are going, and why... Before carving away the exterior pegbox walls, we needed to know where all the nails were... With nearly 35 nails throughout, we need to dig them out so that we do not spend the next year resurfacing and sharpening our planes! big hunk o' maple.  We begin by planing the fingerboard surface... just visualizing the heel...not final layout... establishing the heel angle... wetting the end grain makes it cut like butter! yeah, we like big neck blocks! After cutting out so much wood, we are of the opinion this is not maple, but rather oak! Slowly carving things down... wetting the endgrain of the bushings helps to cut it well... layout, layout, layout... fitting by eye and feel first, follow up with chalk for a perfect fit... 100% fit, trim excess before setting in place (while you have easy access to it)! We just love clamp shots.  Looks like bass torture! normally we would begin to layout the pegbox walls and cut out material...but we have cheeks to fit first... Layout of the pegbox floor... drilling out material speeds things up with a chissel... getting close...

View of the bench

 

 

Upton Bass String Instrument Company 2005