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The IOBO Humpy

August 15, 2016 3 min read

The CdC IOBO Humpy

must be one of the world’s greatest dry flies. It is incredibly simple to tie yet unbelievably effective since in various sizes it imitates/suggests a host of insects (Midges, Aphids, fluttering Stoneflies, Fluttering Caddis Flies, emerging Olives, Olive Duns, Black Gnats & others).

IOBO stands for It Oughta Be Outlawed,

it is that good. It was devised in the mid 1990s by Pennsylvanian Jack Tucker. Dutch flytyer, Hans Weilenmann, has put a video on You Tube that shows Jack’s original method of tying. My method is very different, but the resultant fly is virtually identical. I modified the tying method to make it easier to judge accurately the wing length, also to facilitate the easy forming of 2 slightly splayed wings to ensure that it landed correctly every cast & also to allow thin or fat bodied variants to be tied (I virtually always use thin bodied variants). In recent correspondence with Jack (when he kindly contacted me to thank me for crediting him with the pattern in an article for FF&FT magazine) he very generously said that he preferred my method of tying.




  • 8/0 Tan or yellow Uni thread.


Cdc dry fly by David Southall | Sunray micro thin fly lines.

1. Wind thread from short of the eye to the bend. ( I like to wax the thread first). Then tie in two CdC feathers (natural gray) with 2 loose turns. Pull the CdC feathers towards the eye till the tips are about 11/2 to 2x the shank length. (Match the size of CdC feathers with the hook size).

Cdc dry fly by David Southall | Sunray micro thin fly lines.

2. Tie in CdC with 2 or 3 more tight turns. Then wind the thread to just short of the eye in open turns over the feather butts. Trim off any remaining butts.

Cdc dry fly by David Southall | Sunray micro thin fly lines.

3. Pull the CdC “tail” forwards (over the back) & tie in with 3 to 5 tight turns. Whip finish in front of wing to push it up slightly, as shown. I like to leave a few trailing CdC fibres as a ‘tail/shuck’ (not on the original pattern).

I tie it in sizes 26 to 12 (mainly 24 to 18).

When fishing CdC flies ignore all the erroneous advice that CdC flies are useless for more than one fish after they get slimed up. Follow the sequence below & you should be able to catch loads of fish on the same fly, even on a wet day.

  • Rinse the slimed up/soaked fly thoroughly in the river/lake.
  • Squeeze hard in a piece of absorbent kitchen paper (much cheaper than amadou & when it gets dirty it can be discarded. Old amadou gets impregnated with hydrophilic slime & dirt, which render it useless).
  • Rub vigorously with the kitchen paper & blow to open up the fibres (CdC is very tough!)
  • Apply a tiny drop of Roman Moser Miracle Float (available from Stu Wardle at Durham Flyfishing Company) or slightly less effective a drop of CdC oil or Tiemco Dry Magic onto your forefinger. Spread thinly between thumb & forefinger.
  • Rub into the CdC.


The IOBO Humpy, Shuttlecock, F Fly & Hackleless Elk Hair Caddis

are my four most used dry flies & I would be devastated if I was unable to use them.

Grayling are suckers for a size 20 to 24 IOBO Humpy but in my next Blog I’ll be talking about sight fishing for big grayling with nymphs, shrimps & bugs.

This video is 1 of 94 casting tutorials explaining everything from basic set ups to master level casts

Fundamentals | Starting to Fly Cast

The basics of tackle
Language of casting
Sensory awareness


Fundamentals | Understanding Fly Tackle

Fly line weights, lengths & tapers
Rod lengths & weights
Leaders & tippet
Tackle to practise with


Fundamentals | Overhead Casting

How to hold a fly rod
Circles 8's & straights
Remove all slack
Plane of the Cast
Triangle Method
Overhead Cast
Stop & Drop
Retrieving the Line
High Back Cast
Breaking The Wrist
Shooting the line
Loop Shape
Slipping the Line
Stroke Length
The Forward Delivery
The Shelf
Drift Versus Breaking the Wrist
Backslash Forwardslash
Speed Ramp
Body Movement


Fundamentals | Double Haul

Intro to the Double Haul
Tackle for the Double Haul
Single Haul
Double Haul
Double Haul Fast Track
Cast Trajectory
Late Haul
Hauling Grip
Double Haul for Accuracy
Line Trays
Offset Alignment Guides


Fundamentals | Taking it to the Water

The Lift
Pick Up & Lay Down Cast
Roll cast
Energy of a Roll Cast


Advanced | Spey Casts

Intro to Spey Casting
Switch Cast
45 Degree Single Spey
Backhanded Cast
90 Degree Single Spey
90 Degree Snake Roll
45 Degree Snake Roll
90 Degree Double Spey
The Running Mouse
The Silent Spey
45 Degree Double Spey
45 Degree Snap T
90 Degree Snap T
45 Degree Circle Spey
90 Degree Circle Spey
Body Movement
Spey Cast Hauling
Beating Obstructions Spey


Advanced | Beating the Wind

Tail Wind
Head Wind
Side Wind


Master | Mends

Upstream Downstream Mends
Curve Mends
Reach Mends


Master | Pick Ups

Corkscrew Pick Up
Snap Pick Up
Roll Cast Pick Up
Double Spiral Pick Up
Snap Pick Up Variation
Aerial Spey
Cast Stringing


Master | Accessory Casts

Casting Big Flies
Feed Cast
Free Snag Cast
Snap Cast