These are just some ideas and thoughts on Spey flies from my own experience and from talking with friends. Spey casting and tying has been a hobby of mine for around a decade, so I’m sure there are people much more experienced. Maybe my ideas are wrong in here, maybe there’s something here the experienced folks have not realized, maybe not. Hopefully there’s some helpful stuff here for somebody.-
Spey casting and fly casting in general is an easier thing to do, the lighter weight your flies are. The more weight in the fly from the hook, its materials or from the water it absorbs, the tougher it is to pull out of the water and send to its destination. The larger the fly is, the more fly weight comes to play, so for small flies this is less important. Fly weight is especially important with spey casting since the fly doesn’t get to shed water on the back cast and the fly starts its flight from in the water itself. A lot of these issues have been bypassed with modern spey lines that have extremely large amounts of mass to turn over heavier items, but even they have limitations. Even with the modern lines, learning how to tie a spey fly that is easy to cast and gives the impression of a larger fly without excessive material usage is one of the fundamentals of modern spey fly tying. Conversely, at a certain point very large lightweight flies begin to be very wind resistant and adding a little bit of weight like some lead, dumbells or a cone may actually make the fly cut through the air and wind easier (especially moreso with 1 handers). Its about balancing to your conditions/situation. Adapting your tackle to the river and the fish.
Generally softer materials that absorb water, move well in the water but don’t hold their shape as well and stiffer materials hold their shape but don’t move as well in the water. (generally) For example, rabbit especially absorbs a lot of water and moves amazingly. The problem is rabbit is heavy from the water absorption and quickly becomes difficult to cast. The more rabbit that is used in the fly, the harder it is to cast. For smaller flies its fine, but for really large flies, rabbit is almost unusable. Marabou absorbs a bit less water, but moves very similarly to rabbit. materials like rabbit, marabou and other very soft materials can often turn your fly into a streamlined leech pattern if you don’t use your other materials to provide your shape and profile, although a skinny fly isn’t always a bad thing though. Anadramous fish attack streamlined patterns pretty intensely at times, probably mistaking them for a lamprey or an eel or possibly a skinny minnow like a sandlance.(Or just because they’re steelhead and they want to attack something) Still, if you want to give a profile closer to a squid, medium to deeper bodied baitfish or other common food form, use your soft and stiff materials together to create the movement and shape respectively.
Weight also comes from the hook or shank you use. Something like a Waddington shank adds quite a bit of weight, so using something like a plastic tube or even an old hook shank for your body can cut a lot of weight from your fly if that’s desired. Some rivers you need heavy flies, some you don’t. I tie a lot of my flies now fairly lightweight, and add tungsten cones onto the line in front of the fly if I need weight. Although I still tie a few heavies and some intruder style flies with dumbells to invert the hook for dragging on the bottom. Again, it really comes down to adapting your tackle to the rivers you’re fishing in.
Lastly, fly tying and fly fishing is a personal thing. Whether you’re tying rubber flies with worm weights, or maybe intruders with some traditional touches, or even tying a full dress Jock Scott salmon fly, what you tie and fish with is totally up to you. Don’t let anyone tell you different.
Here’s a few intruders and tubes Ive been tying lately. A few for myself, and some others for some of our local non-profits to raffle off. Nothing too serious, just some stuff to fish with.
I also had 3 different Truckee area friends going up to AK this summer to guide. I tied them up a few different baitfish style tubes (chartreuse or blue/ white) to huck at Kings. I hope those flies get some use and abuse.