The Royal Wulff, although somewhat garish in appearance, has proven itself over numerous decades to be a remarkably effective dry fly pattern, particularly in rough water. I do tie the body on mine a little differently than most people, but there are many ways to achieve the same result.
I like to tie them on dry fly hooks with fairly long shanks, like the TMC 100 - these are size 12 but the pattern works well anywhere from a 10 all the way down to an 18. For the majority of the fly, I'll be using black 70 Denier Ultra thread.
Start your thread with some space behind the hook eye. Leave your thread at about the 3/4's position on the hook shank. This is where your wing will be. Here I'm using calf body hair for the wing but calf tail also works very well. Snip a fair sized clump from the hide and then give it a good stacking to align the tips. If you need to, flip the bundle around so the tips point toward the hook eye. Measure to produce a wing that is one hook shank in length. Saving that measurement, move the bundle up to the tie in point and, with a pinch wrap, secure the calf hair to the top of the hook. Calf hair is slippery stuff so bind it down really well. Pull the hair tips back and build a thread dam in front to prop the wing up. Make a couple of wraps behind the wing to really lock everything in place. Snipping the butts off at an angle will help to create a smooth body later on.
Separate the calf hair into two equal clumps for the wings then make figure eight wraps to separate them. Take wraps around the bases of each wing to collect any stray fibers and add support. Wrap down the butt ends to produce a smooth ramp to the hook shank. If you have any errant hairs now is a good time to snip them off. I like to add a small drop of Zap-a-Gap between the wings to ensure they stay upright and separated. Finally, wrap your thread back to the bend of the hook.
Moose body hair works great for the tail on this fly. Snip a small clump free from the hide and then pull the fluff out of the butts. Although moose hair stacks really well, you may have to pull an errant fiber or two from the bundle. Measure the bundle to create a tail, one hook shank in length and then, with a pinch wrap, secure it to the top of the hook. Pull the butt ends back and snip them off to create a smooth transition into the wing butts. Wind your thread all the way back to the base of the tail.
On this size 12, I'm going to use three peacock herls to form the body of the fly. Break or snip about an inch and a half off the tips of the herls as these can be rather brittle. Secure the herls to the top of the hook shank and then, with hackle pliers, get hold of the butt ends. Snip the butts off close so they don't get in the way later on. Twist the herls until they begin forming a nice uniform rope but don't twist too much or you'll end up breaking them. Begin wrapping the herl rope around the hook shank to form the body of the fly. Here the process is sped up a little bit. Once you have the herls secured, snip them off close.
Prepare a Coachman red hackle for tie in. With the dull side facing you, strip about an 1/8th of an inch of fibers from the top side of the stem to ensure the hackle wraps correctly. Starting behind the wing, secure the hackle to the hook shank then take several wraps in front of the wing. Now's a really good time to use a half hitch or two to kind of "save up" and keep everything secure.
A Royal Wulff should have a fairly bushy hackle collar. Three or four wraps behind the wing, followed by three or four more in front is about right. With the wraps complete, secure the hackle tip trying your best not to trap fibers as you go. You can then snip the remainder of the hackle off close. Pull the hackle fibers rearward and take a few more wraps of tying thread. I'm going to use my bobbin to do the whip finish here as its nozzle can be used to push the hackle fibers back and prevent them from being trapped beneath the wraps. Although it takes a little more time than a standard whip finish, it's a technique that works exceptionally well. Snip or cut your tying thread free and, if you like, add a drop of head cement.
Finally, load a bobbin with red thread, here, UTC 70. Start taking wraps at the midway point of the body. Once the thread is secured, you can cut the tag end off close. Take wraps to form a red segment about 1/3 of the body in length. Whip finish either by hand or with a large whip finish tool and then snip or cut your tying thread free as close as possible. I always use a drop of head cement on this segment to ensure it doesn't come unraveled.
The Royal Wulff is an oldie but a goodie and definitely deserves some space in a fly box, especially for those who fish rough, tumbly water.