[jbu311]

Why is it tapered? Can i just replace the whole leader and tippet with some of the mono that I use for non fly fishing?

[caster]

The taper of the leader turns the fly over better. Basically the heavy butt section tapering down to the fine tip helps the fly and leader unroll.

[liv2fish]

Depending on the leader/tibbet and the type of fishing you're doing I would say you can replace the very end section (not the whole leader) with mono from a spinning rod. I actually use about 1-2 ft of 20lb test mono as a "bite tibbet" for pike. I wouldn't replace the entire thing with mono for the reason stated above by caster.

[FrankB2]

Do you mean using 4lb test for the whole length of the leader? If so, try it.
You can look at the leader in the same manner as the fly line itself. It's heavy
because the line's mass is needed to make a cast. If mono had enough mass,
we could skip fly line altogether, and just cast a long leader.

The fly cast system is an energy transfer system: the rod responds to your
arm movements, transferring energy to the line, which in turn transfers energy to the leader. If you had a 9' length of 4lb test at the end of a 5wt
line, the sudden transfer of energy from a heavy line to a very light line
probably wouldn't look pretty. I'd imagine the "leader" would fail to keep up
with the line, and would quickly collapse and wrap around the line.

You can get away with using a non-tapered mono leader in larger diameters,
as with bass bugs. I tie my own leaders, and use a 4 section leader for
0X size leaders. There's still a taper, but not much.

The rod itself is also tapered, for the very reason the line/leader are....

[Nooksack Mac]

In addition to being thin enough at the tippet end to go unnoticed by fish, the leader, like the line, is usually a part of a dynamic system. We want a leader, during the forward cast, to transmit a diminishing amount of energy, just enough so that the leader straightens out and drops -- not crashes -- the fly to the water. Trolling a fly doesn't require casting, so level mono works fine. When casting sinking flies and sinking lines or tips, it's ok if the leader piles up: the fly will sink that more readily. So leaders for sinking can be short and simple. My winter steelhead leaders are 4-5 feet long, and of three or four sections, at most. A 15-foot leader to drift down a small dry fly needs to be a sophisticated design, of many sections if it's knotted from butt to tippet. There are many published leader formulas in print.

[fishenrg]

I got a chance to go out a couple of days ago and I decided to do a little hike upstream from where I usually start. So after hiking for about 30 minutes I got to a part that looked promising and was farther upstream than I had ever been on this river before. Its a small river in this area with vegetated banks and many trees over and in the water. I see a couple of dark shapes lurking under one of these snags and sneak up for a couple of casts. One cast, two casts, three...wait, where the heck is my leader and fly? I have, or had, one of those woven loops on my fly line and, well, it had just come apart. It didn't unwind or anything, just one side of the loop detached...along with my leader. And to make matters worse I had no other leaders. But I did have tippet material so I figured I would just tie on 7-9' of tippet material and go from there. I learned very quickly why leaders are tapered, this idea simply did not work!