Arrow cavitation question

[hurlbri1]

So I've built a few arrows from birch dowels.  The 36" 5/16" dowels fly really well with my buddy's 72", 48lb @ 30" draw bow.  They spined between 40 and 45 lbs.  125gr field points.  5 inch shield cut feathers.  Self nock.  They are working for him great.

Then I build some arrows for me.  I built 3/8" birch dowel arrows, same build as above except I cut them down to 28" with 125 gr. Zwicky 2-blade broadheads--they were heavy.  My arrow was dropping at 9 yards, so with my short draw of 26", I cut them down to save weight.  These arrows also had a much stronger spine--4 came in around 50lb the rest were 55lb or better spined.  I only shoot the 4 that are around 50lb.  My flatbow is 60" NTN, 51lb at 26" hickory self bow.  I also shoot carbons from the same bow (too expensive to toss, so I still shoot them--don't yell at me, ok?!). 

Here's the dilemma.   The carbons shoot fine.  Straight and fast and for the most part where I aim them--I am no perfect shot!  They are 31" long.  The wood arrows are slower, still have a good snap though, but kick to the left.

I know they are too stiff for my bow, right?  Left is too stiff, right is not stiff enough.  BUT, the way it flies is so weird--the arrows stays on a flat plan--does not porpoise (at least from what I can tell--but it might)--as it flies, the tip of the arrow is left of the bulls eye and the nock is to the right of the bullseye--it flies like that.  Not straight as an arrow.  And it always winds up to the left of the bullseye, at an angle in the target where the tip is to the left of the nock.

Is 3/8" too wide a diameter for my small 1/4" wide arrow rest?  Is this the way it flies when there's too much spine?  Does the width of the arrow increase archer's paradox so I need to spine wider arrows lower?  Can I fix it?  What the heck is going on?

Thanks for your help!

[PEARL DRUMS]

If your only pulling 26" you have to add 5# of spine per inch under 28", so your 50# spined arrows are really 60# from your bow, too heavy. Add weight up front and see what happens.

[aaron]

Like pearl said, and you suspected, your arrows are too stiff. Adding weight up front should do it. Besides your short draw, and the shorter arrow length, another thing that may be making these arrows too stiff is the width of your handle- wider handles require softer spine.
yes, thicker arrows need to bend more because they are farther from center shot, but I think this difference is small compared to the effect of handle width, arrow length and draw length.
I have been learning a lot about comparing spine and taking into account all these variables, by playing with a free program called "stu millers spine calculator".

[PEARL DRUMS]

Carbon is carbon. It has its own mega spine range. 3 sizes cover every bow made damn near. Thats why they shoot so nice for you. Wood reacts totally different and requires alot more increments. In your case the difference from center each shaft sits due to its diameter, plays a very minimal role. Now take a 50# spine 5/16 and a 50# spine 23/64 wood shaft and shoot them, you might notice a difference.

[bubby]

I use a lot of poplar dowel arrows, you would be better off with 5/16" instead of 3/8" with the 26" draw unless you go with a longer arrow

[stickbender]

    All of the above, but try a longer arrow also.  Just because you have a short draw, doesn't mean you have to have a short arrow.   

                                                                        Wayne

[crooketarrow]

  RASP,SAND THEM DOWN TO THE RIGHT SPINE.

  If your knocks arepointing left or right. You need to ajust your brace hight.

[hurlbri1]

Sorry--it's been a while since I've been on.  Just wanted to say thank you so much for your insights!  I am finally done with some obligations, so back to some arrow building I go!

[tallpine]

Your probably not going to be able to add enough weight up front to get decent arrow flight. Its been my experience that a self bow needs about 10 lbs. less spine than a glass bow with a cut in shelf, both having the same draw weight. If you are going to use 3/8 shafts , taper the last 1/3 of the shaft down to 5/16. I chuck them up in an electric drill and use sandpaper wrapped around the shaft. I never cut my shafts to length until I shoot them first then I cut off a 1/4 inch at a time until they fly right. I think that one of the hardest things about primitive bows is getting good arrow flight.

[Pappy]

Leave them long,or as Crooketarrow said sand/plane/rasp  them down in the middle 2/3 that will drop the spine and some arrow weight also. Point weight will help some just not as much for the weight you add,I use point weight to mainly fine tune my arrows. I have a 26inch draw also but most of my arrows are 29/30 some even longer.
   Pappy

[Danzn Bar]

hurlbri,
Lots of very good advice from lots of experience.  arrows can be a booger to shoot straight sometimes then there's that one you want to shoot all the time.  "Priceless"
DBar

[Forresterwoods]

I think there is something about diameter that affects spine and I'm not sure how. One difference I know of is I use harder woods to achieve smaller diameter with the same spine. I can shoot 50# 5/16 arrows from my 58# longbow....and 43# 9/32 arrows with the same bow. With softwoods I need 60# spine. I think the stiffer the wood the quicker recovery from paradox. Fun stuff to play with.

Kevin

[DGF]

I think there is something about diameter that affects spine and I'm not sure how.

My theory is the center of the arrow shaft is further from the bow on the 5/16, 50# arrow so it should act stiffer than an arrow of the same static spine in a smaller diameter shaft when shot. Unfortunately I can't shoot well enough to notice the little differences.

-Dan

[Danzn Bar]

I think your right  Dan........Further away from center shot.