With my current setup (44# recurve 28" draw) I have been shooting 2016s (5 inch feather fletching) with 125gr heads which fly straight and true. I decided I would like to try a slightly stiffer and heavier arrow and ordered a set of 2018s (5 inch feather fletching) and used the same 125gr heads. Well, much to my dismay, these arrows fly like #@!&*#!! I went back to the shop that cut the arrows for me and was told that shooting the heavier arrow was the problem. He, of course, couldn't explain why the heavier arrow would cause fishtailing and helical flight, but I tried his suggestion and tried 100gr heads and the arrow flight became even worse. So I guess my question is what would cause these kind of flight problems??

Sounds to me like you were at the top end of the acceptable arrow spine for your bow--the stiffer arrow is most likely the problem. Going with a heavier, not lighter, point should solve it, if that is the case. A heavier point will decrease the effective spine of your arrow, and vice-versa for a lighter point.

Chad

Long Bows Rule!

First of all if the 2016 had perfect flight you needed to add at least an inch of arrow shaft to get 2018's to fly straight with the same point weight and drawlength. Chad's right, if you want the 2018 to fly straight you need a 150+grain point. Not a lighter one. An easy way to tell if this is your problem is to overdraw your 2018's by 1-2 inches and see if this straightens out the flight pattern. Of course this will probably make you wobble when you release so everything goes back out the window.