srry cant help dont know what an atatl is

Well, the fletching is useful.  Not essential, but quite useful.  Did you use a dart long enough?  If it's too short, it's bound to flip.

english my dart is 5 1/2 feet long

I find that a twenty inch atlatl with a half inch forty five degree hook carved in works best for me.

I like to "mammoth fletch" my six foot long darts.

You take two turkey feathers and, without doing anything to them except for cutting off the fuzzy feathers on the end, you tie and glue them on.

I can only explain it this method, : like a sandwich.

i fiddled with stone points but never got to put them on, i just sharpen the ends and try not to aim for rocks.

targets are cardboard boxes.

Henry,
It sounds to me as if your projectile isn't flexible enough which would cause it to flip as it flew. And fletching really helps to put drag on the rear end of the dart, which keeps the front end up and keeps it from flipping. And the atlatl doesn't need to be flexible, but the dart does. Flex should be somewhere between 5-8 pounds. You can test it on a bathroom scale by pressing one end of the dart on the scale and measuring the amount of force it takes before you notice it bend slightly. My atlatls are all about 26 inches long, and throw darts of about 6.5-6.8 feet long, including the detachable foreshaft. I make mine from solid wooden dowels and attach a detachable foreshaft of about 2 foot with a piece of pvc pipe, which helps add to its flexibility. I can usually put my darts out about 70-80 yards with a good toss. When you throw the dart, it should sort of wobble through the air, but still go in a straight line, and I would not, on this note, reccomend a side arm throw with an atlatl, if you're hoping for any sort of accuracy. It just makes it harder to get full leverage out of the atlatl and will also, therefore, affect your range. The throwing motion should be very similar to throwing a baseball, ideally. Overhand, with your atlatl and hand ending up beside your right leg if you'r right handed and left leg if you're a lefty.