Waterside observation of the behaviour of the particular insect we wish to represent, in whatever stage of its life cycle, is the first stage in fly design. I was often told by an artist friend that no matter what I thought I saw, I should draw just what I was looking at. When designing trout flies this has a distinct advantage. Looking at the mayflies, they are an obvious challenge to build upside down on a hook. The result lovely drawing; hooking ergonomics disastrous! So how do we build it?
Tails tied in around the bend, split for aerodynamics; abdomen built along the shank; wing behind the hook eye, tied within the bend; thorax in size and colour to match the natural. Legs, if any, further complicate the build. Do we choose to hackle the fly? If not, the thorax may be picked out to assist floatation. What if we want to imitate the legs, like in the yellow may dun with its bright legs and glowing body? How do we build the upside-down fly to land USD and ensure it stays that way? And finally, will it catch trout?
The answer to the above is elusive. Tailing/winging are major considerations in aerodynamics in this style of fly. The winging and hackling are the major obstacles to hooking. Hackling is preferable for a long float and when you want legs. When these obstacles are overcome the fly becomes viable in its design.
Dry flies need light hooks. In my opinion long shank lightweight grub hooks are ideal for USD flies. They give a low centre of gravity, allow you to get the wing away from the point, deliver an excellent profile of a mayfly dun or spinner and accommodate enough hackle at the thorax to ensure a sound platform for the imitation.
When constructing the fly, lay a bed of thread from behind the thorax to 1/3 way round the bend. Tie in four soft strong fibres, hackle fibres are good, if they are springy. Spread them in a fan shape. They need to be springy so that they will retain their aerodynamic effort after sustained casting; and soft enough not to interfere with hooking.
Build the abdomen, ribbed for effect if you wish, on the rear half of the body. I feel that the body should be low slung, but not quite in the surface; of course the lower you sling it, the better the centre of gravity of the fly, so that lessens its chances of falling over. In a breeze, this fly, instead of toppling over, faces into the wind like a natural dun. You heard it here first folks! Segmentation is achieved with mono, wire or tinsel.
Winging the fly is a problem. The first and glaring disadvantage is that the wing and hackle may mask the hook point. The long shank hook helps a bit here, by placing the wing further from the point. We can crank the hook about twenty degrees at the wing base to alter the hooking dynamics and, of course, choice in winging material is also crucial; it must be strong, flexible and soft - not stiff. The wing is tied within the gape, behind the eye, a quarter way down the shank. Woodduck, pintail or mallard fibres stripped off the stalk and tied in thin, up to twice the length of the gape, makes an enduring wing and aerofoil which will fold away from the point on the strike. Polypropylene gives good effect and can be trimmed to a sparse wing, but will fold into the bend and collapse. Take a Velcro brush along to groom these up. Whole feather wings within the bend spell disaster for my hooking percentages.
The thorax of this imitation should be made of water resistant material. Hare's ear fur, dyed to suit is easily dubbed. The shape should present a slightly fatter profile than the abdomen in order to imitate the natural.
We could funnel the hackle over the eye and cover the roots with dubbing for the thorax and you have Neil Patterson's Funneldun, an excellent pattern or we could hackle the fly around the wing roots within the bend - a tricky and perhaps not enduring construction - or parachute outside the bend USD Paradun style - a good method, though in practice the length vs. density of the hackle is crucial and the centre of gravity of the fly is just a fraction too high for my taste. Alternatively we could palmer a hackle then cut off the barbs outside the shank - this palmer design is messy and wasteful but good support is achieved and the light pattern is excellent, with that necessarily low centre of gravity.
A few hackle fibres tied, facing aft will help support the fly even better. Always select a hackle which is strong and springy, without being stiff.
One night I was sitting drawing again, cabin fever strikes down the best of us sometime, under my cabin bed, but I definitely digress here
I drew a USD dun - a lovely fly, then I had a flash of inspiration, nothing new in principle; again, just the application changes. I thought if I took the thorax cover, as used on tying a nymph's wing cases - and tie it in as a breastplate for the dry fly, he will have to spread his arms like a true warrior. Tied thus I could use every fibre of those precious hackles and form an excellent platform for the fly in one simple move. We have the USD Palmerdun. For a confirmed light pattern enthusiast, who is a founder member of Hackle Misers Anon, this appeared to be a step forward. It is easy to construct so it is renamed the EasyPeasy USD dun.
Thus, above, you have my considerations of the challenge of USD. The lovely thing is that, if properly constructed, the fly is extremely effective (besides being great to look at!). The manner of construction is again crucial, with regard to proportion, aerodynamics and presentation. This fly should be built sparsely. I only use Permaflote, the old stuff, as greasy floatants can ruin the profile and thus presentation, due to matting of the fibres.
Taking my own best advice above I build the EasyPeasy USD as follows:
- Tie silk from 2mm behind eye round bend to 30 degrees
- Tie in tails, splayed outwards at 40 degrees for aerodynamic effect
- Tie in rib
- Dub and wind abdomen
- Rib and tie in
- Attach wing, slim and made from 15 mallard flank fibres, tied in within the bend 1½ to 2 gapes tall, quarter way down the shank
- Tie in thorax cover and hackle hackle should be 1 to 1Ό times gape, the thorax cover can be feather fibres, the hackle stem or whatever you choose. Pick a colour to match the thorax of the natural dun or spinner.
- Dub and wind thorax fur
- Palmer the hackle two turns at rear, then to eye
- Tie in hackle, DO NOT cut off excess
- Dress the palmer hackle back then down over the wing to split it in half to each side of the thorax. Ensure the rear hackle barbs point aft.
- Pull the thorax cover through to the eye and tie down.
- Cut off only the excess of the cover.
- Whip finish
- Finally pull off the hackle tip, leaving the dozen stray fibres behind to complete the light pattern and the artificial fly's platform.
Note: if you are tying this fly streamside, you can omit the thorax cover by using the hackle stem as a thorax cover. This is also useful on smaller flies.
This fly will support a degreased leader and it will face into the wind like a natural. It presents a light pattern representative of mayfly duns on the surface of the water very effectively indeed. The aerodynamics are such that it always lands correct way up and due to the low centre of gravity it is unlikely to fall onto its side. The profile of the natural is very well imitated against any background.
The colours should be selected to match the naturals whatever they appear to the fish - since the trout can see flies through white water and outside the spectra known to man, I am still working on this area. Seals fur bodies are good, blended to suit. Tying silk should be in sympathy with the body colour. Hackles can easily be blended by using two colours or types. Excellent combinations can be obtained, even mixing for example a sunburst grizzly dyed cock with a well-defined rusty blue dun hen hackle - which makes a very effective platform for the Yellow May Dun. Play with hackle mixtures; some wonderful colour mixes can be had. Entertain your quarry! ;¬}
Subtly dressed the EasyPeasyUSD takes no longer than a standard dry fly to tie. This pattern is most pleasing in the fly box, wonderfully attractive to the fish and if it is overdressed it is a disaster and a mountain of frustration. Properly and slimly dressed it is a great catcher of trout. If you make a mess of it the first few times, you will have some excellent cripple patterns!
Roy Christie (firstname.lastname@example.org) is a flytyer and Sexyloops' board member, who likes to tie flies backwards, upsidedown and inside out.