Through years of making paper airplanes, I’ve learned how to make a good one. One of the things I’ve learned is that flat-noses are best. What I don’t know is why. Could anyone explain?
I doubt that the aerodynamics of the flat nose have anything to do with it. Often the nose of a paper airplane includes multiple folds intended only to increase the weight, so it may be that your flat-nose designs have a better center of gravity/rotation due to the forward weight.
Well, why is a forward center of gravity good?
I’ve noticed that most flat nosed airplanes also have larger wings, since the wings are the same width (which is wide) the entire length, as oppossed to sharp nosed planes, where the wings start narrow and become wide.
Larger wings = better floating.
IME, a balanced or slightly forward biased plane tends to resist excess lift that causes the plane to stall when thrown more forcefully. A plane with too much forward bias, on the other hand, acts more like a dart. It might fly straight and get good distance, but it will not be as good at generating lift as a more balanced plane.
It’s not so much you want a forward center of gravity as a centered center of gravity. You want the CG located such that the airplane meets the air at the angle of attack resulting in best glide speed (assuming you’re going for distance) or, put another way, the minimum sink rate.
It’s a little hard to tell without actually seeing your designs or attempting to determine their CG, but it could be the that the sharp-nose designs you’ve been using have an aft CG, which would tend to make the airplane fly nose-up, which can combine to give you sink rate greater than minimum, or even to stall the airplane (the nose and plane go up, pause, the nose drops, and the airplane tends to plummet. Or maybe nose down - fly a bit - nose up - pause - nose-down - fall - fly - nose-up… rinse and repeat all the way to the ground). A better CG results in a much more consistent and longer glide.
Too much of a forward CG, as already mentioned, will result in lawn-dart flight paths.
You might try experimenting with adding some sort of weight to the front end of a sharp-nose design (it won’t need to be much at all) and see if that give a result more like your flat-nose design.