There has been some questions about tying your own leaders. The following excerpt should give you a good start. Having some leaders tied ahead of time can really save the day. Keep in mind that there is no leader formula that will work in every condition and these formulas below are just good guidelines. You will want to adjust your leader to fit the conditions, often changing several times in the course of the day.
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A Beginner's Introduction to Leaders and Tippets
An excerpt from Fed Fly Fisher’s Booklet,
Introduction to fly fishing by Judy Lehmberg
So that the fly will land correctly on the water, it is necessary to attach it to the line with a tapered leader. The leader is generally composed of monofilament nylon that is tapered to a relatively small diameter tippet at the end. Leaders are an important aspect of the entire fly fishing system because they are relatively thin and thus vulnerable to breaking, they are relatively difficult to control, and they are the part of the system the fish is most likely to see other than the fly.
There is no such thing as a perfect leader but there have been quite a few improvements in the last few years.To function effectively a leader must keep the fly far enough from the line tip so as to not frighten the fish, have a tippet that is small enough in respect to the size of the fly and be designed so that the fly will land correctly on the water. As you might imagine, when you vary the flies you use, you must also vary the leader so that it corresponds to the size and weight of the fly. Because it is not practical to change leaders with each fly, a compromise leaner design that will work over a wide range of fly sizes is desirable.
Although there are still some fly fishers who prefer a hand-tied leader, one that is composed of five to seven pieces that get smaller as they approach the tip, most anglers are now using the newer one piece, tapered leaders. The hand- tied leaders do have the advantages that the taper can be changed at will and the material can be changed to get optimum fly delivery. Two hand-tied leaders are described below.. The Ritz formula, designed by Charles Ritz in the 1940's, is very accurate and lays out straight even in the wind. The Harvey formula, developed by George Harvey, lays out in soft IS" curves ensuring a long, drag-free float.
The leader length is determined by the tippet size; the finer the tippet, the longer the leader becomes. These leaders vary from nine to 12 feet. Even if you never build your own leader the Harvey and Ritz formulas can give you an idea of how leaders are designed.
THE GEORGE HARVEY FORMULA * 10"-.017: Maxima (Hard) * 20"-.015 :Maxima (Hard) * 20"-.013 : Maxima (Hard)20"-.011 : Maxima (Hard) * 12"-.009 : soft * 18"-.008 : soft * 22" TO 28"-.007: soft
THE RITZ FORMULA (All hard - Maxima - material)
• 40" - .018
• 36" - .016
• 6" - .014
• 6" - .010
• 6" - .009
• 6" - .008
• 25"- .007
Many fly fishers now use a one piece leader of about nine feet. The diameter of the leader end or tippet is determined by the size of the fly being used. As a general rule, tippet size is determined by dividing the fly size by four to get the tippet sit which is expressed in decreasing sizes as 0X, 1X, 2X, 3X, 4X, 5X, 6X, 7X and 8X. This is called the rule of 4. In other words, for a size 12 fly you would use a 3X tippet. For clear and smooth water conditions, it's best to go one size smaller in tippet diameter, therefore the most appropriate tippet for a size #12 fly would actually be 4X. You should carry tippet material in sizes 3X, 4X, SX and 6X.