Casting from a drift boat is different from casting while wading. First of all, in a moving boat you do not have the luxury of taking your time to size things up. You need to quickly pick your target and get that cast in there, right away.
One of the toughest things to adjust to is to limit your back casts. Better yet, train yourself to pick up your line, make one false cast and get your flies back on the water. After all, that is where the fish are.
In a drift boat it is possible to get very long, drag free drifts. To achieve this a few things need to happen. The first one is that you make your cast towards the front of the boat. The second is that you make a reach cast so that your fly, leader and flyline all land in the same line of current. (See diagram) If you do not make a reach cast, then you need to mend your line as soon as possible.
Mending. This word is said more times a day by guides than any other! Mending is critical while fly fishing for trout whether you are in a boat or not. If you are dry fly fishing and not mending your drifts will be very short and the number of strikes you get will be drastically reduced. Mending can make the difference between lots of fish and no fish when dry fly fishing.
A mend is necessary when your fly line developes a "belly". This is simply the curve in your fly line that is created when the line lies accross different current speeds. The faster current causes the belly. The belly causes your fly line to speed up and become taunt. This is when your fly begins to drag and the fish that would have eaten the fly gets spooked and swims away.
In the diagram above the current is represented by the blue arrows, the longer the arrow the faster the current. The orange line has not been mended and the faster current is now dragging the line, leader and the fly. A mend is made by simply lowering the rod tip and gently flipping the belly upstream. (There are times when a downstream mend is needed. Basically you mend to get the belly out of your fly line.) This will put a little bit of slack back in the line and enable the fly to drift drag free longer. Remember though, you need to get your first mend in before the fly (or strike indicator) begins to drag.
Keep this in mind: If you want to hear your guide yell, "STRIKE!" more often, remember to mend so you do not hear, "mend". The less often you hear "mend", the more often you will hear, "STRIKE!".
To make a reach cast you need to develop a slightly higher line speed, meaning get your rod tip moving faster, then abruptly stop the rod tip with the line still in the air. Just as your leader straightens out, reach outwards and upstream with your rod tip while letting some slack line out. Your rod should be about seventy to ninety degrees to your fly line. When done correctly the end of your fly line and your leader should land in a much more parallel angle to the bank than perpendicular. This really is much more easy to do than it seems here. Hey, you could someday have to double haul, even triple haul, before you throw the reach cast in at the end.
What the reach cast accomplishes is to make your fly line and leader land in basically the same current line. There will be much less of a belly formed in your fly line, resulting in a longer drift. Longer, drag free drifts mean more strikes, which means more fish. One false cast, reach then mend. Easy!
