The way it went for me (and I think is fairly typical) is you will struggle and struggle and struggle to get the timing right. Then all of a sudden it clicks and you wonder what the heck was so hard about that? Drills help a lot, especially one-armed fly (for me at least). You'll definitely get it soon enough.

I saw a YouTube video yesterday on a fly drill that supposedly helps you learn the rhythm of the kick and is supposed to be more relaxing for beginners. The drill involves extra kicks between the pulls. You basically do one full stroke and after the recovery, keep your arms out in front (like you're about to catch the water and do your next pull), do two or three extra dolphin kicks and then a full stroke. I think the video is called "butterfly extra kick fly", by GoSwim.

There's no doubt you'll get it, you've gotten all of the other strokes down & this will be no different. As Prof. Owl said, it will all of a sudden "click" - I tell the kids I work with that it's like riding a bike, all of a sudden you've got it & you'll never forget how....

My MFP friend, LKuderna, pointed me to a YouTube video for a butterfly "tipping" drill that helps with the timing of the body. That might be another good resource for you. The biggest thing that will help is practicing the things you learn.....

I did 15 mins of my fly drills this morning and seemed to get it most of the time but I only do a couple of leg kicks then arms then glide and stop/start again. My hips felt like the were dipping at the right moment instead of my bottom poking out of the water when I lift my arms out as was happening before! I will google both the suggestions (tipping drill and one arm drill) and give them a go on my next swim on Saturday. Thanks for all the suggestions.

For a while you may want to do a drill with a dolphin kick and breaststroke pull, they are little easier to do then fly arm pulls, and they can help you get the hang of the rhythm, and getting your hips up high. People call it kick timing, I prefer to call it rhythm that happens throughout the whole stroke cycle. If you get the whole rhythm of it down, then it will be easy fine tuning little things, like doing the kick a tad sooner or later. With timing of a specific part, especially with people who are just learning, people often zero in on one component of the stroke and neglect that it needs to work as a whole.

Fly and breast are both considered 'short axis strokes', in plain language that means they are related, lot of basic building blocks are similar and can be used for both.

To prevent hips from sinking and that whole sliding downward and backward feeling, rhythm and building up strength are key components to fixing it.

oh, oops, I read that wrong, I thought you had said your hips were sinking. *blush*

Thanks Connie - I already do breaststroke with fly legs (I can't do traditional breaststroke legs due to hip problems) - I seem to get the rhythm there OK, but my issue is more that when I lift my arms out of the water for fly my hips also rise out of the water instead of being down so that's what I will be practising like crazy tomorrow. Will let you know how i get on.

How fast is your fly? Do you practice any of it with fins? Fins may give you some extra momentum so your hips don't have time to float up?
Although, this is very much a guess on my part, not having actually seen you swim.

Make sure you do the dolphin kick with your whole lower body, the movement goes almost from the chest down. It may be possible you are doing it with just legs, especially knees and down, so if your hips aren't engaged and pushing down, they could float up. Again, I'm guessing trying to think of things that may cause it.