Having problems with some new arrows.Only fletched up one to try,its a lodge-pole hex shaft.Tapered shaft 50/55 spine cut to 29in.with a 125 point.Bow set-up is a HH cheetah 66in. 48lb. at 25in.my draw.Problem is arrow goes where
I look but swings slightly to the right before it hits the target.Tried a 60/65 ash arrow cut at 28in. with a zwickey eskimo bh. and it flew like a dart.Thought you have to go to a lighter spine with a HHbow?That ash arrow is what I used out of my reflex-deflex longbows.What is wrong???

I shoot 10-15 # above the weight on my HH. Why are they cut to 29" if you draw 25" I think 26 1/2" or 27" would be better.

Nothing is wrong, but you must remember that each bow has its own preferences on arrow spine. I have 3 HH bows that like arrows spined for the stated draw weight of the bow. One of them likes higher spined arrows. My  two Cheetahs fall into this exact scenario.  Take the time to find what your bow really likes and you will get darts all the time.

I cut the arrows at 29in. to keep the weight up so I can use the eskimos.Don,t want to change bhs.

If I am not mistaken if they are cut to 26 1/2 or 27" they would be a little stiffer and may even fly better with the 125's. If not you could add a 160grn head

It's the beauty of wood.  Spine measurements only deal with resistance to flexing and don't account for how quickly the wood returns to its original state.  All woods have different recovery speeds so spine ratings between woods are often misleading.