Originally Posted by porkrind
ok when setting up your line etc. is it necessary to have backing? (why)
after you have your fly line on then you attach a leader. do you then need a tippet also?
if these questions seem simple remember i have never set up a modern fly set and i am just not sure.
thanx in advanc
Backing serves several purposes on a fly reel. First, if you land a good sized fish, it's apt to want to run on you; rather than simply letting you reel it in from the point where you hook it. In this case, when the fish runs, you can run out of fly line quickly (even though they're about 90' in length) and when you do, you don't want to slam on the breaks with the fish because with that strain you're apt to break off your tippet or leader and loose the fish. So, the backing, effectively, provides you with more line with which to play the fish. Backing is also a lot narrower than fly line, so you can get a much longer amount of backing on a reel than you can fly line for any given diameter since you will eventually fill up the spool and won't be able to add any more backing or fly line. One a per foot basis, backing is also a lot cheaper than fly line, so there's also an economical advantage to using backing. For example, for a 5 wt. line, the amount of backing can very, but should probably be 50 yards minimum and up to 150 can't hurt you. With the math, that gives you 90' + 150' = 240', up to 90' + 450' = 540'. Seems like a lot of effective line, but there will be days; hopefully many of them, when 90' just won't do the job for you.
Initially, before the advent of large arbor reels (reels where the diameter at the base of the spool is large; say greater than 3"), backing provided a means to effectively generate the physics of a large arbor reel. Simply, as you wind on backing the effective spool diameter increases. When you've finished putting on the backing on a standard arbor reel, the backed spool diameter has increased, usually to the point of what we would today call a mid-arbor reel. This becomes important for several reasons. The first is that it makes it easier to pick up your line if you have a larger effective diameter spool, since if you put the fish on the reel, then one turn of a larger diameter spool pulls in more line than one turn of a smaller diameter spool. Also, fly line doesn't like to be wound around a small diameter spool, because it has a certain degree of "memory"; meaning that it will want to stay in the shape of the spool and this "coiling" will have a negative effect on casting unless you stretch the line before you start fishing. So, a larger arbor spool doesn't induce as much memory into the line as a smaller arbor spool.
No, you don't need a tippet at the end of a leader; particularly if it's a new leader, as long as the end of the leader matches the fishing conditions that you plan to encounter at the stream. But, a lot of people (myself included) will tie on tippet so that they can both get a better presentation and prolong the life of their leader. Leaders are much more expensive than tippet on a per foot basis. Tippet also allows you to fine tune the presentation of your fly, so that it hits the water like a natural insect falling out of the sky. Say for instance that your'e fishing a 9 ft. tapered leader that ends in 4x material. That day, you plan to fish for relatively small fish on runs where ripples on the water would be noticed by the fish and might spook then. In this case, you can tie on 2-3 feet of 6x or 7x tippet, tie in your fly; which for the conditions that I'm describing would probably be a #16 or smaller dry, and be able to present the light fly and tippet gently on the water just like the natural insect.
There are additional rationales for using both backing and tippet. Hope this helps.