Re: Tenkara line + leader
Happy New Year!
Getting a tenkara line to turn over and casting in the wind are two different issues.
The 10.5' traditional line from Tenkara USA casts well on the 12' Iwana, so if you are having trouble when it isn't windy it is a question of technique. The tenkara cast is not quite the same as a cast with a Western fly rod.
Instead of the 10 to 2 taught for Western casting, limit your back cast so that your rod movement is from 10 to 12 (this assumes you are facing towards 9 o'clock). The second biggest difference is that in tenkara there is a lot of wrist movement. The cast starts with raising your forearm a little, then cocking your wrist (stopping with the rod straight up at 12 o'clock). Pause very briefly for the line to straighten out behind you. With the level line I'll recommend later for wind, you should be able to feel the line tug a bit when it has straightened. Your forward cast starts again with the forearm going back down and finishes by straightening your wrist. This last wrist motion is snappy and is what loads the rod.
Stop the forward cast abruptly at about 10 o'clock. Most people coming to tenkara from a fly fishing background do not end the cast early enough or abruptly enough. When you have stopped the rod at 10, then raise it back to about 10:30, which is about the angle you should hold it for most fishing. Raising the rod tip even slightly at the end of your cast will have a dramatic impact on how well the line and tippet turns over. Similarly, not stopping the cast abruptly at 10, but instead having a soft stop at about 9 will cause the line and leader to fall in a pile just beyond your rod tip.
Casting in the wind is a different issue. The essence of tenkara, besides the long rod, is using a light line. The light line allows you to keep your entire line, and even part of your tippet off the water and out of the reach of any tricky cross currents. This is what gives tenkara tremendous presentations. You want the line to be light enough that it just barely overcomes the wind resistance of the cast. If you are fishing on a windy day you will need to use a heavier line. Level line made from fluorocarbon is denser and is better able to overcome wind resistance than a furled line made from nylon mono.
Tenkara USA has recently made some changes in their traditional line, and I don't know which one you have. If it is green it is pretty light (nylon mono) and although capable of very delicate presentations on still days, will be very hard to cast into a breeze. They now have a line described as a "wind line" which you might already have if your line is yellow and you did not buy it very recently. (The most recent line is a third generation line, which is also yellow but not as heavy as the wind line.)
In any event, I prefer level lines to begin with, and for the 12' Iwana would recommend a size 4 line for most conditions with a size 5 held in reserve for when the wind won't let you use a size 4. When fishing in the wind, you may have to fish with the rod tip low and line in the water to keep it from being blown about by the wind. You will lose much of the advantage tenkara offers (from a presentation standpoint) but will still have the simplicity and the very direct connection you feel when fighting a fish without a reel.