Yumi Build
I decided to try my hand at building yumi since I've had an interest in how they are built for many years now.  The process of building a yumi is a labor intensive process that involves many different woodworking skills to accomplish.  Also, to get the proper shape for a yumi a method of tying and wedging was developed to hold the yumi into shape while the glue dries.  Here in I will describe the procedure I used to build a yumi.  Since there is very little information about the process is available (I tried to obtain Jaap Koppedrayer's video "All Tied Up in Bow Making" but the supplier was all out).  I did find an excellent write up on PrimitiveArcher.com's forum (http://www.primitivearcher.com/smf/index.php?topic=11083.0) and Paleoplanet69529.yuku.com's forum (http://paleoplanet69529.yuku.com/topic/22774/t/Yumi.html?page=1) that explains what is on Jaap's video.  I decided to add what the forum's leave out and added a couple of gauges (poster board/wood patterns) that can be used to help get the various curves close to being right.  I also used the yumi I bought a few years ago as my example, and guide, taking measurements of the thickness/width of the core, thickness/width of the bamboo, and traced its profile to get the proper curve needed.
	Materials and Tools Needed
	Two (2) Flat Bamboo strips, 8' long by 1" wide Core wood, I used Red Oak to practice with, but ended up using Cherry, 8' long by at least 1 1/4" wide (core can have anywhere from a single piece to five pieces glued together, I'll explain later) Two (2) Scrap pieces of the core material, 6" long by at least 1 1/4 " wide, used for the notch areas Binding Cane, used just above the grip Fine Cane, used at the ends near the string notches Hide glue, or a good woodworking glue (I used hide glue for the build) (last four items can be obtained at a craft store, or at a Woodcraft store) 1/4" twine or rope, used to tie up the glued bow blank Enough scrap wood, or more bamboo, to make approximately 100 wedges 6" long by 1" wide Small hammer to set the wedges Small hand plane (I used a small Japanese finishing plane), used to shape the finished yumi Large hand plane (I used a large Japanese plane), used to plane down flat bamboo prior to belt sanding (Japanese Planes can be obtained at Japan Woodworker) Belt Sander, used to flatten the flat bamboo and core
Building Procedure
The first thing that needs to be done is to cut out the core pieces.  The core for modern yumi are made up of (5) five pieces, (2) two being bamboo and the other (3) three out of wood.  The first yumi I built, I used a (2) two piece core just for practice.  The core ended up working just fine and after some research I found that the first core to be used was a single piece of wood, followed by a two piece core, followed by a three piece core (which was either three pieces of wood or tow pieces of wood with a piece of bamboo in between), followed by the modern way of using a five piece core. To cut out the core pieces (I will use the three piece all wood version for this build) first select wood that you'd like to use.  I decided to use red oak for my first attempt since it is readily available and relatively cheap to buy.  For the three piece core I used cherry.  When buying wood for the core, choose wood that have a fairly straight grain and seems heavy for it's size, typically a 1" x 1 1/2" x 8'  piece is needed.  You want to find wood that has wide growth rings.
References: www.primitivearcher.com www.bamboohabitat.com/index.htm www.woodcraft.com www.japanwoodworker.com