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Balancing arrows. (Read 1837 times)
Mike_R
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Balancing arrows.
Jun 14th, 2005 at 7:43pm
 
This might make no sense but here it is. Do arrows have to balance from front to back? I couldn't really find any answers to this. Does an arrow that is too heavy in the tip dip down when fired? Does an arrow that is heavy at the nock and light at the point tip up and hit high? I think that they do. So I made a little pedestal for the arrows to ballance on. Then I move them until it ballances. But where should the balance point be? Right in the middle? Mine seem to balance so that the front third of the arrow is on one side and the back two thirds balance on the other side. These seem to fly perfectly. But when I put some broadheads on that are lighter than the points I normally use that tip up and hit high. I use 150 grain field points and the broadheads I was testing were about 75 grain.
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english
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Re: Balancing arrows.
Reply #1 - Jun 15th, 2005 at 9:07am
 
Different sorts of arrows have to have different centres of gravity.  However, typically, for a regular, flighted, 28" arrow, I'd put the balance point at about 1/3 from the tip.  Remember, an arrow with a nock heavier than the tip will fly so erratically as to make it a joke.  Balance point is important, but often it can be intuitively judged.
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Mike_R
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Re: Balancing arrows.
Reply #2 - Jun 15th, 2005 at 12:30pm
 
Different sorts have different balance points how? And that is where I have been putting the balance point. But my arrows are almost 33" long. I draw to about 31.5" But I guess that it would be about the same.

And holy crap, arrows heavier at the nock end fly all over the place. I tried some and the would tip up sharply, or break hard to the left or right.
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english
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Re: Balancing arrows.
Reply #3 - Jun 16th, 2005 at 3:12pm
 
Yep.
  Flight arrows might have a balance point that is nearer to the middle than most, that kind of thing.  The Chinese developed a whole system of making arrows based on the balance point.  I'll try and find the information soon.
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Mike_R
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Re: Balancing arrows.
Reply #4 - Jun 17th, 2005 at 1:28am
 
I just thought it was strange that it is overlooked. Since I started making my own custom arrows I've been matching the grain weight, the spine, and the balance point. It just made sense to me.

Also does anyone know a good reliable source for wood shafts with heavy spines? The stiffest, highest grain ones I can find around here is about 550gr and 70-75lb spine. I want some that are about 90lb spine at 33" And hopefully 600gr weight.

Right now the heaviest setup I can put together is 500gr + 150gr points, and spined to 75# at 33". They hit with lots of momentum and fly straight but I could do with a bit tougher as I have broke a few hunting. They tend to pass through and smash on something hard.
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T._Kumpulainen
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Re: Balancing arrows.
Reply #5 - Jun 23rd, 2005 at 2:00am
 
The balance point of an arrow is expressed in FOC %, or how much Forward Of Center in % of the total length of the shaft, the balance point is. Typical hunting / target arrows have a FOC of between 10 and 15%, target arrows used for long range shooting (up to 90m) have a 7 - 9% FOC, while flight arrows are normally at 0% FOC, or even up to several % backwards of the center point.

Most hunting archers (myself included) feel that the more FOC an arrow has, the more stable it is - with high enough a FOC (17%+), one would not even need any fletching to make the arrow fly well. For comparison, low FOC arrows can turn sideways in mid-air if insufficiently fletched. The biggest reason not to use very nose-heavy arrows is that they make the shaft act weaker, requiring thicker / more massive shafting than most would want.

For consistent arrow flight, all arrows must of course have the same FOC. Practice / field points' weight should match the weight of hunting points / broadheads.

Finding 90# / 33" commercial wood shafts can be next to impossible, since almost no one uses such heavy (both in spine and, inevitably, physical weight) ammunition. I wonder what's the need for 90# shafts if your 75# shafts fly straight, as you say. If they have good flight, it is almost guaranteed that a 90# shaft will be too stiff for your bow / shooting style, and not hit where you want it to. What you need, then, is 75# shafts made from stronger materials to hold up under the strain. The vast majority of commercial shafting is made from Port Orford Cedar, a light, weak wood. Norway pine is also much used, and not much better in terms of strength. I would suggest hardwood shafts: maple, ash and hickory have all been used with success. If you can't find these, make your own (I do). Bamboo is another, very tough arrow material - I've hit rocks with some bamboo arrows without damage to shaft! If carefully selected for straightness and spine, even ordinary garden supply bamboo stakes make good field arrows.

Tuukka
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Mike_R
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Re: Balancing arrows.
Reply #6 - Jun 23rd, 2005 at 9:25pm
 
Thanks. Finally an arrow scientist steps forward and sets me straight. I had come up with some of that on my own. Like that the point is heavier and that all the arrows in a group should be the same. I even mad a little balancing deal, like a teeter-totter for arrows to check that all the arrows in a group were the same.
You ar correct that really heavy spined arrows would be too much. But I need them to be at least 75# spined at 33" long. I could cut them down an inch to increase the spine but I would rather keep them full length. I have some nice big two blade broadheads, maybe I can cut an inch off and put those on. The heads are like 3" long so they should be just about right.

Anyway thanks, I'm planning to make some shafts on the lathe, try a bunch of different woods. So I should be able to make some nice ones that hit like a runaway schoolbus.
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