Matching your arrows

By RJ Bachner



Have you ever considered making your own arrows? Having considered that, you probably looked into how to do it and came across such arcane terms as front of center (foc) or Matched shafts? Well we are here today to explain such as this to you. Believe it or not your ability to get better as an archer depends on such arcanery as this.

Note:

This is for people that know next to nothing about fletchery, you will read some things that are not technically correct but explain better the way I have written it. If you can tell what is being fudged then you do not really need this little primer but for the rest this will provide you with enough basic knowledge to get the job done and will allow you understand a complicated issue in small steps.

We who use wooden arrows are faced with a number of technical handicaps, wood is not consistent and therefore each and every shaft is different. Weight varies, spine varies, this you can do little to fix but strive to combine arrows that all rest with in certain set standards for accuracy. By minimizing variance in these and other factors such as foc and having properly matched arrows we can minimize the mechanical side of our handicaps and move on to the mental and physical ones that impede our dream of being a ludicrous Bowman.

I suppose I should start out by defining "foc" and "Matched set" hunh?

  • Front of center (foc) is a value that represents the ratio of the difference between the balance point and the center point of the arrow divided by half the length of the arrow. I knows it sounds complicated but it isn't.

Basically as you release the arrow, the force of the bow is transmitted into the arrow as forward motion or Kinetic energy which changes to potential energy when arrow and string come apart. This "energy" for the lack of a more descriptive word, is assumed ( for the sake of theoretical physicists) to be contained in the front end of the arrow and infact the arrow is sort of pulled along behind the point.

Of course this is assuming that the balance point is infact in front of the center point of the arrow by about 10-15 % for heavy or hunting arrows and closer to 10% for light weight arrows . More than this and the arrow is nose heavy and becomes unstable quickly as the fletching cannot stabilize the flight and any breeze will throw the tail about. Less than this and the arrow becomes tail heavy and as it slows down will start to stall and destabilize just like a plane will if it slides backwards.

You may hear some folks talk about the foc being at the 2/5ths. They mean that the foc should be 2/5ths of the total length behind the point. This works out to about 10% so either way they are right and you have nothing to worry about.

To Calculate foc you simply follow some simple steps.

  • 1. measure the arrow from the point where the shaft meets the nock and the point where the shaft meets the point.

    Length measurement
  • 2. Calculate the center point.

    Center calculation
  • 3. Balance the arrow on a sharp sturdy surface so that the balance point can be measured accurately. Write this down so that you can use it later.

  • 4. Calculate the ratio of foc by subtracting the center point from the balance point, this is called the difference. Now divide this value by the centerpoint and multiply by 100.

    Difference Ratio of foc

  • Matched Sets. of arrows are ones that have been measured and tested to within certain standards so that they may all be as similar as is possible.

As I said before, wood is variable and not consistent, this forces us to adopt standards of precision that are, well they are "close enough". Most fletching suppliers will provide arrow shafts in 5 lb spine groups, where all the arrows will be spined at between say 45-50 lbs. For most newbies, this is a sufficiently precise group that beginners will not see much of a difference if we spined them any closer.

The reason the suppliers do that is so that they can get more use of their stock, if they had to separate them into +/- 1 lb or half a pound or whatever then there would be 13- 49 lb arrows and 7- 46's and 23- 44's and so on. you can see the problem with that from a suppliers side can't you?

However for a skilled archer that will not be enough, as spine weight varies, the location of the arrow on the target will vary left and right. For my own arrows I spine then to within +/- 1/2 lb. My 47 lb arrows all sit within 46 1/2 and 47 1/2 for accuracy.

The other thing is to match them for weight, +\- 10 grains from the supplier is normal. This gives a 20 grain range. Trying to go for closer weight is possible and maybe even worth it as you get better but again for most newbies it won't make much difference.

If you want to get it to a more exact measure, there are 2 steps to getting there. Firstly you need your otherwise untouched shafts, tapered as cleanly as possible, a good grain scale and a sharp taper tool.

  • You must first weigh them all and choose the lightest one. This is the one you will bring all the others down to.
  • Now using the taper tool, carefully remove wood from the nock end of each of the heavier shafts until it matches the lightest one.
  • Note: This will work best if all the shafts are closely matched to begin with or you can shorten some shafts so much you will significantly alter the foc and throw the whole thing off again.

Once your raw shafts have been brought down to the same low weight mark, you need to:

  • Stain, paint and crest them, this all adds weight so do try to be consistent in this.
  • Then you must dip them in sealer which adds a lot of weight, about 5 grains a coat.
  • When they have had 3 coats or however many you feel they need and have dried completely weight them all again.
  • This time select the heaviest one and bring them all up to it's weight range. You do this by giving lighter arrows another dip or 2 in the sealer at 5 grains a dip to bring the weight up. (1 dip at a time with a drying period in between)
  • Now you assemble the complete arrow being carefull to avoid adding too much weight with glues and whatnots.

Ok, now that you have your shafts all measured and you are happy in how they match, you need to test them to make sure they all fly the same. This is the pesky bit I hate to tell people who cheaped out and only bought a dozen shafts. You have to make up a bunch of arrows and shoot them to see where they each go.

I seldom make arrows in groups of less than 24 and I do not recommend you do less if you would be accounted a good archer.

  • First you must number them all, sequentially works well and take notes on how each one flies to the target. Choose a nice still day, mornings are best I find. When you have shot each one 10 or 15 times, shooting the bunch sequentially as you numbered them, your notes should show which ones consistently go high, low, dead on or wild.
Shooting them in this way will allow you to eliminate your errors of form by increasing the sample size and giving you a better averaged idea of what that arrow will do. You do have to record the position for each arrow and I would also suggest you have someone else do this for you.

Have them hand you each arrow in order and then record high, low, dead on or wild for each shot, the actual score matters not.

  • Group like with like, high with high, low with low and dead on with dead on. Hopefully you have enough arrows in this batch that you can make 3 bundles of at least 6 (an end in the sca). The wild ones, if they cannot be fixed should be tossed, or better yet donated to someone who doesn't care.
  • Wild arrows can be caused by many different things, the bow string may be fraying or have broken strands, the fistmaile may be off, the bow may be broken or breaking or just plain too heavy for you. Are your sleeves catching in the string? Various body parts? What I am trying to say is that a lot of wild shots may be indicative of your own shooting and not the arrows so don't assume that the arrows are at at fault right off.
I recommend cresting them to show each group from another, kinda like transistor stripe code where each pattern means something specific.

At this point you should have a pretty good idea of where your arrows hit in relation to one another so now go see what you can do on the range.


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