I keep trying to come up with the least expensive but very practical "practice Kora" 
Something easily made with just basic tools (electric or not) & commonly available materials, 
in a few evenings.  I recently posted a DIY article on making an inexpensive practice Kora 
using goatskin for the head. As easy as it is to mount such a goatskin, this plywood 
head is considerably easier - no skin mounting, stretching or tacking down etc, just 
cut a plywood circle & glue it onto the bowl. I held it tightly for drying by using 
lengths of duct tape.

Traditional African Koras have heads made of stretched animal skin. This simple Kora 
instead uses a thin 3/16 inch thick circle of plywood for the head, the big 
advantage being that a wooden head is not nearly as weather/humidity sensitive as 
animal skin and stays in tune far longer (once the initial week or two "settling-in" 
process is finished) - very helpful when dealing with a 21 string instrument. 
I can just pick it and play it - for weeks at a time without having to tune anything.
In addition, the sound quality and volume is truly not that much different from a skin head.  

Here's what I've got into this thing:
- I used a strudy Ikea wooden (actually pieced bamboo) bowl - altho any old wooden 
bowl or gourd from about ten to fifteen inches diameter will work fine. Just today found 
a nice, quite suitable bowl for $1.99 at a local Goodwill store. Generally, the larger
the bowl, the louder the instrument.

- A small circle of 3/16 or 7/32 inch thick plywood "handi-panel" - I saw a 2'x2' piece 
  today at Home Depot for $6 recently.
- $12 worth (4) of Lowe's 1.5 x 1/4 x 48 inch long solid Oak "trim" strips  
  glued together to make a very sturdy 1" wide neck. Like with my last Kora project, 
  I cheated a bit & used only two pieces of this oak trim, substituting some black walnut 
  wood I already had on hand.
- A few lengths of various thickness inexpensive fishing line & weed whip cord.
- $8.40 for 21 "zither tuning pins" from elderly.com to tune the strings.
- one $2 oak 1/2" diameter dowel rod (I now suggest using a dowel one size larger)
- few small scraps of wood
- one eye-bolt
- a few minor odds and ends

Procedure (the included photo talks better than my words): All dimensions are on the photo.
- Titebond glue the four oak trim strips together carefully - using as many clamps as you can.
- Cut a sound hole in the side of the bowl where shown. Size is not too important.
- Very carefully cut out the two rectangular holes in the bowl that the neck goes through.  
- Sand the neck before installing the zither pin tuners & brad "nuts". Insert neck into bowl holes.
- Install the big eyebolt.
- Cut the soundboard plywood circle. 
- Flatten the bottom of the two dowel rod handles a bit (except the part held by hands when playing), 
  then glue & screw the rods to the top of the plywood.
- Make the bridge & bridge "guy wire"
- String the thing. Bowline and/or fisherman's "clinch/cinch" knots work fine.
- I prefer to cut the additional sound holes in the plywood after the instrument is up and running.

A few notes (largely from my other Kora articles but applicable here):

To ensure that the zither pins do not slip,I ignored the recommended pilot-hole gauge --- You're 
supposed to use a #13 "number drill bit" for zither pins but I used a #16 bit for the thickest string, 
a #15 bit for the next thickest string and a #14 bit for all the other 19 strings. This worked out great. 
Number drills can be found online. Nineteen of the Kora's nylon strings fit through the holes in the 
metal zither pins nicely as-is but the the holes in the pins for the two thickest strings have to 
be drilled-out a bit larger to have the strings fit. Easy.

I sometimes use small holes in the bridge for the strings to pass through 
instead of slots - but slots are easier when stringing. Angle the slots 
slightly downwards towards the center of the bridge to keep the strings 
in place. 

A "guy-wire" or cord is necessary to keep the bridge vertical and keep it 
from tipping over. Wire or nylon cord works equally well. The photo show 
this guy-wire.
 
String information:
In west Africa, there is really no "standard" pitch that Koras are
tuned to. Some of the ones I make are tuned to an "F" pitch (lowest
strings on the left and right side tuned to "F") but I rather like 
this one tuned in the fairly common pitch of "D" - with the lowest
strings on the left and right side tuned to "D". 

  STRING GAUGES AND  TUNING:
                                                  HIGH-PITCHED END

    30 LB (.022 inch) fishing line    C#-| |
    30 LB (.022 inch) fishing line    A--| |--F#   20 LB (.018 inch) fishing line
    50 LB (.029 inch) fishing line    F#-| |--E    25 LB (.020 inch) fishing line
    50 LB (.029 inch) fishing line    D--| |--D    25 LB (.020 inch) fishing line
    60 LB (.031 inch) fishing line    B--| |--B    40 LB (.024 inch) fishing line
    60 LB (.031 inch) fishing line    G--| |--G    50 LB (.029 inch) fishing line
    60 LB (.031 inch) fishing line    E--| |--E    50 LB (.029 inch) fishing line
   .050 inch weed-whip line           C#-| |--C#   60 LB (.031 inch) fishing line
   .050 inch weed-whip line           B--| |--A    60 LB (.031 inch) fishing line
   .065 inch weed-whip line           A--| |--F#   60 LB (.031 inch) fishing line
   .095 inch weed-whip line           D--| |--D   .040 inch weed-whip line (or
                                                   100 LB fishing line)

                                                  LOW-PITCHED END

Regular monofilament fishing line is used for the higher-pitched strings.
Weed-whip (aka weed-whacker) line is used for the lower pitched strings.
Use ROUND, un-serrated weed-whip line. Lately ridged or square line
is being sold - avoid it.
 
NOTE: IF ANYONE ABSOLUTELY CANNOT FIND A PARTICULAR GAUGE OR TWO,
LET ME KNOW AND I'D BE HAPPY TO MAIL TO YOU.

 
A NOTE ABOUT STRING STRETCHING:

Monofilament nylon line stretches a lot at first - Not just 
on a Kora, but on any instrument.This is an unavoidable but 
fortunately short-lived situation. It takes about two weeks or so 
before the things completely settle down.  
 
My procedure is to tune up the instrument right after it's made. 
Then keep retuning it a couple of times daily (it will drop in 
pitch regularly). After a day or two it's playable, so long as 
you realize that strings will have to be retouched quite often, 
until it's completely settled (in a couple of weeks).

Pulling on the strings after they're just put on can speed the 
stretch-in process.

During this process, remember to not just tune the instrument 
to itself, but tune it up to pitch. Day by day the thing will 
hold it's tune better.  

A tip - when using zither pins, try your best not to ever crank 
a pin into the wood so far that the non-threaded part of the pin 
enters the neck hole lest the threads in the wood get messed up. 
It's a great idea to periodically (for the first couple of weeks) 
take off the strings one by one (keeping full tension on all the 
other strings) & back the pin out until about 3/16" of thread is 
showing, insert the string back in the hole in the pin & then pull 
the string 3/4 of an inch or so further thru the pin hole before 
re-tightening. This trick is most useful on the four thickest strings, 
which seem to stretch more than the higher pitched strings.

I have grown quite fond of using zither pins for Koras -- they work great.
Never had one slip. The downside is that you have to use a tuning wrench
--- not too expensive at music stores. I attach the wrench with velcro
on the back side of the neck - out of the way, but grabbable in a second.

Dennis Havlena - W8MI
dhavlena@gmail.com
August 2, 2013
northern Michigan
dhavlena@gmail.com
DennisHavlena.com