How to Tie John Gribb’s “SB” Foam Mayfly

As promised in “Beyond Fur and Feathers,” a story on the fly tying innovatons of TU member John Gribb that ran in the Fall 2012 issue of TROUT magazine, here is the recipe for John’s “SB” (which stands for seat belt) mayfly pattern.  Yes, the wings are made from the seatbelts of junkyard cars.  If you can get your hands on some of those materials, give this pattern a try.  It’s absolutely deadly.

Materials List for John Gribb’s SB Foam Mayfly (photo numbers refer to elements in frame, beginning top-left and moving clockwise):

Hooks: Bronze Mustad 3282 sizes #12, #10 and #8 for large mayflies bent 90 degrees. For very small flies use Orvis big eye hooks 4641 in size #12, #14, #16 and #18 bent 90 degrees. See #1 in photo.

Note: Use only hooks listed as they will bend without breaking…most others are too brittle!

Razor Foam: Available in many colors from your fly shop (#2 in photo).

Double stick carpet tape, 3M brand is preferred.

Tying thread size 14 called “Sheer” brand available from fly shops (#3 in photo).

Seat belt out of back seat of old model cars, preferably 1970 or older, in silver or black. Cut both edges off and strip away outer fibers from both sides leaving a ¼” in the center to keep things together. Now you can pull out one bundle at a time which is the proper amount for ALL sizes of flies tied (#4 in photo).

Cut one edge of silver ribbon and pull off the silver strands (save strands pulled off) exposing the nylon filaments, which come out one at a time in a “V” shape and will be part of the tail. This ribbon can be found at stores like WalMart or any ribbon department (#5 in photo).

It’s best to use a slightly oversized hackle.

Super glue liquid: Most flies are ruined by using too much glue. Use only a very tiny drop (size of a pinhead).

I prefer to use super glue liquid available in Dollar Stores in 1-oz bottles and make a simple dispensing unit using a flap off a cardboard box and folding it in half, punching a hole a inch from top for bottle and stapling the cardboard to a block of wood (see #6 in photo).

NOTE: You MUST use super glue on these patterns; head cement will not work.

Water-Shed the flies as nylon absorbs water quickly. 


Tape 2 sheets of Razor foam together (2 thin sheets for size 18 and 20 hooks); a thin and thicker sheet for larger flies. For example, I use tan underneath and green on top for a BWO. Use your own combinations of colors for whatever fly you are tying.

Cut out the rough outline of the body (see #7 in photo).

Bend hook at 90 degrees and pinch the barb down.

Secure the foam to make the body. Then secure a single V-shaped nylon filament and wrap thread over the filament ¾ the way up the tail, and double wrap last segment, and then wrap down again to the base segment. Clip off the ¼” left beyond end of the tail which served as a handle while tying the tail. Use size 14 thread or the thinnest you have able.

Take one bundle of seat belt fibers and add one silver filament and fold them over the hook from the bottom and make a single thread turn around the folded bundle above the hook to complete the post. All that’s left is to hackle the post.

Add a just a touch of super glue (see above) under the thorax and at the end of tail on the top.

Water-Shed the flies and let dry overnight before using.

-John Gribb

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