Originally Posted by pszy22
There is an "art form" (tongue in cheek) called - Chuck and Duck.
Chuck and duck, which has come up fairly often, is a fine example of to heavy. You can't fly cast it, hence the "chuck". The "Duck" is because getting hit in the head with a fistfull of lead hurts and is a warning. You can also do it on a spinning rod and in my opinion is not fly fishing, even if you use a fly rod to "chuck" a handful of lead. There is a dressed up form (Hahaha, not really, it's just the same thing where they were to lazy to make slinky weights) called the Provo bounce. Not fly fishing either and they even leave the fly line on. Many chuck and duckers are just running straight mono. They don't even try and pretend it's flyfishing.
The way to tell if it is to heavy is it will become to hard to get any distance with. The best thing to do is use the smallest amount of weight that you can get away with and still get down to where the fish are. You can make that depth a couple of ways. Heavier flies, sink tip lines, sinking lines or a combination of heavy fly and some line type.
Ard came up with a pretty slick idea also. He is making chunks of fast sinking line like T-17 or something, and putting loops on both ends and incorporating them in the leader. I stole his idea and it works really well.
You can make those and use them between the line and leader as well. That works also, but Ard's idea of putting it in the leader will get you a bit deeper because the leader butt does not float like your fly line.
Another thing you can do to get more depth if you have current, is to cast up river and let it drift and sink till it gets to where your fish are. The current will will start to pull your fly back up though as it gets below you on the swing. If you start off down stream, you can't get as deep.
One more trick, and the one I use the most, is to use a combination of a weighted fly (medium hour glass eyes), casting up current and counting down like you would a sinking crankbait and a longer leader. I hook bottom in really deep water that way with a fairly good current sometimes. In fact I hooked bottom once in what I know was every bit of 22', but I also added to the three I mentioned in this a sinking poly leader made by Trevor Morgan. It really gets you down there.
One last trick you can do is any of the above, but after the line hits the water, walk down river with it as it sinks to keep the line drag free. Drag will pull on the fly and slow or stop your drop. I have done this here when the current is really bad and still get the fly down where I need it.
One last thing I forgot to mention in the post before, when I was talking about what weight pulls what in the different forms of fishing, is that when you have the weight in the lure trying to carry the line, and the line is heavy, they fight each other. It will stop you from getting the distance you want.