Relative Humidity

Fine custom Ukulele luthiers, particularly those in Hawaii, like to brag about their humidity controlled workshops.

Wood is designed to carry water from the ground and air to all parts of the tree. Cutting down the tree does not change that behavior. Meaning that water does horrible things to wood.

This week in Los Angeles weather, freakish thunder storms and June showers have sent the relative humidity through the roof. And I have a half-finished ukulele body for that atmospheric moisture to play tricks on.

Once the heel and neck blocks and linings were installed in the sides, I sanded the top and bottom edges nice and flat, with the quarter inch taper.

The jig has ends that (in theory) match the taper of the body, which is helpful when gluing the blocks, but not so much for clamping when gluing the top to the sides. The kit instructions recommended shimming the neck end by the amount of the taper before clamping – that way the base of the jig and the clamping caul are parallel.

So, imagine my surprise when I tried to dry clamp the back to the body and nothing was fitting. Comparing the body to a piece of plywood showed the body was warped across the body horizontally. The top braces (both running horizontally – a design flaw?) appear to have done their job, preventing warping one way, but doing nothing to prevent it the other.

Ukulele building activities have been on hold for a few days. The humidity appears to have returned to an El Lay nominal 50 percent.

This morning, I clamped the body between two sheets of plywood and applied moderate clamping pressure. This worked with the top when it began to curl after adding the rosette, and on the fretboard after inserting the fret wire. I will leave it clamped overnight, and hopefully tomorrow brings more (relatively) dry weather — and a flat ukulele body.

2 Comments

  1. Posted 9 October 2015 at 8:43 am | Permalink

    Thanks :)So does that mean that with the Capo all of the chords stay the same but the snceod fret now becomes the first fret, and read these chords as normal?Also for the A it shows barring the bottom three strings, this is on the thrid (forth) fret correct?I apologize for being such a newbie, I just can’t get this to sound right, and i’m not sure if it’s my ear that’s off, or my chords.

  2. Posted 9 October 2015 at 1:03 pm | Permalink

    It’s probably the location of the bridge, which needs to be a small distance farther away from the nut than ideal or else intonation will be off, meaning strings will be slightly out of tune with each other when fretted. Or a capo is used.

    I have not been able to find reliable information online about how to calculate the distance to correct. Everyone has slightly different recommendations :) My guess is that it will vary based on the height of the action and is impossible to calculate accurately.

Post a Comment

Your email is never shared. Required fields are marked *

*
*