Tuning the EFOC and UEFOC Shaft - by Troy D. Breeding
with a followup tuning video by Dr Ed Ashby...
For many, tuning your arrow shafts for best flight can leave you wondering if you will ever be successful. You shoot and adjust the shafts length several times but are still left feeling as though you will never reach your goal of finely tuned arrows.
Hopefully, this article will give you better insight on how to make tuning easier.
For starters, you need to decide what weight broadhead you want to shoot and match that weight with fieldpoints. Next, you need to determine what shaft material you want to use.
If you decide to use one of the glue-on style broadheads and are planning to use carbon or aluminum shafting, you have to include the weight of the broadhead adapter. This will increase the overall weight of the broadhead, so matching the overall weight of the fieldpoint has to be considered as well.
There is one other fact to remember. The heavier the overall broadhead and fieldpoint weight, the stiffer the spine of the shaft will have to be.
If you are looking to venture into the EFOC or UEFOC design of arrows, testing has shown that carbon shafting is the best choice. Wood shafting can get you into the lower side of EFOC. However, getting into the mid section or upper section of even EFOC could very well require you to shoot an arrow in excess of 20 grains per pound of bow weight.
Next, you must decide what spine to choose. Most likely, this is not your first few days of shooting, and you already know what has been shooting fairly well for you with a normal FOC arrow. If you have decided it is time to check into the advantages of increasing your FOC and are now reading that increasing point weight requires increasing spine, you are right.
To be honest, there is no formula written in stone for figuring correct spine. No two shooters shoot the same and no two bows shoot the same. If you already know what is shooting fairly well for you, my suggestion is to start by taking the point weight you are now using and subtracting it from the weight you want to use. If the difference is under 100 grains you may very well be able to use your current arrows unless you cut them to a length that brings the point right back to the shelf of the bow. However, if your current arrows do not stick out past the back of the riser by at least 2 inches when at full draw, you will most likely need to move up one spine group. This same principle goes for wood shafting.
At this point of making the arrow some may ask about feathers, crowning and cresting, or even wraps as well as other things that fancy up the arrow. There are a few things to consider when you talk about making the arrow fancy.
1) Weight added to the rear of the shaft decreases your FOC.
2) Increasing FOC moves the balance of the shaft forward.
3) The further forward the balance, the longer the rear steering arm of the shaft.
4) The longer the steering arm, the less fletch it takes to correct the flight.
If you want to make your arrows fancy, you need to consider that the addition of items like wraps and big fletching can and will change the effects of proper tuning and should be taken into consideration before hand.
Now lets move on to tuning.
At this point, I have decided what weight point I want to use and have chosen the shaft as well. I will be using carbon shafting and a point with weight in excess of 300 grains. I have also elected to use a brass insert instead of the normal aluminum because aluminum can be a weak link in the set up.
The first thing I do is to install the insert in the shaft and glue in the steel point adaptor to the fieldpoint. Install the insert first because I will do all the trimming of the shaft from the rear. The nock is a press fit and easily removed and reinstalled, causing no damage to the shaft.
If using wood or aluminum shafting, the points or inserts can be easily heated so they can be removed to trim the shaft and reinstalled without damaging the shaft. However, be careful with heating carbon shafts because they tend to break down with excess heat.
The best results are obtained by starting with a full length shaft. Cutting the shafts before you start tuning can result in having shafts too stiff and unusable which would require you to increase your point weight to well above what you wanted to use.
The final thing to consider before starting is the target to be used. I suggest using either one of the block style targets or a large block of styrofoam. Bag targets tend to be soft and will not allow you to see the directional impact of the shaft. In addition, you will need to consider the target face you will be aiming at. I suggest using a piece of paper or cardboard with a straight line down the middle of the paper.
Before you shoot the first shot, I would like to offer a little word of advice. The way you hold the bow must be considered. If you normally hold your bow at a cant, you will want to change that and hold the bow vertically when bareshafting. If you cant the bow, you can misinterpret the reading of the shaft, resulting in cuts to the shaft and adjustments to the bow which will continue to send you in the wrong direction.
It is now time to make your first shot. Begin with only shooting at ten yards. The stiffness of the shaft has to be determined, and shooting at a further distance could cause you to totally miss the target and lose your shaft.
Before you even consider making a cut of any length to the shaft, shoot the shaft at least six to ten shots. What you are looking for is consistency. Don’t jump the gun and start trimming before finding out that everything is consistent. Normally, I use two shafts to do my tuning to make sure the results are uniform.
As you can see from this picture, several shots have been made, and the shafts are impacting the paper to the right side of the line as well as having a fairly heavy tail-left impact. Being a right handed shooter, this picture shows that these shafts are shooting weak. If you are left handed, a weak shaft would impact the target on the left side of the line and would have a tail right kick.
At this point, I will now take the shafts to the cut off saw and start trimming the length from the rear of the shafts to increase the dynamic spine of the shafts. My first cut will be rather short. If I get carried away and cut off too much, I could end up with two of my shafts being too stiff to continue. When making the first few cuts, I also suggest you never make a cut over ¼”. If the first cut corrects the shaft quite a bit, the remaining cuts could be limited to 1/8” or less.
Let’s make the first cut and do a little more shooting.
As you can see from this picture, the cut did make quite a bit of change to the shafts. The heavy tail-left kick has straightened, but the shafts are still impacting to the right side of the line. Again, be sure and take several shots. You can see I have most likely made 10 to 15 shots before taking this picture.
A little side note here:
If you are seeing a slight tail high impact on the shafts in the picture, remember, I am not the best photographer and I am trying to show the correction of the tail-left kick. Also, I am still shooting at ten yards which does cause a slight downhill shot angle.
If you are lucky enough to have a target that can be set up at chest height, you will not see this if the arrows are flying correctly off the nock on the string. If the target is at chest height and you are getting nock high impact, you will need to raise your nocking point on the string to level out the shafts.
The next thing to consider is how much to take off on the next cut. The first cut took out a lot of the tail-left kick but did not bring the shaft over to the line. If you are feeling like you would rather take the safe road over the speed run, I would suggest making the cuts from this point on at no more than 1/8”. As the old saying goes, “it is better to be safe than sorry”.
Compare this picture to the one prior, and you will see that my cut made some changes on the impact spot of the target. so I decided to make another ¼” cut. If you are more conservative with pushing the limits of your tuning skills and only cut 1/8” off, you may not see similar results. In either case, make sure of the out come of each cut with several shots, and continue cutting and shooting until your shaft starts to straighten.
Your results may differ from what I’m showing, but don’t give up. Tuning is not something that is easy to learn. Still, as you do it more and more, the process will become easier, and you will learn when to make the longer cuts.
As you can see from the picture, I am getting fairly close. However, remember I am still shooting at ten yards. We will get to the longer distance shot in a little while.
The cuts so far have made great improvements. From this point on, I will limit my cuts to no more than 1/8”. Even though this makes the process slower from here on, a little at a time will be all I need.
Another side note here:
If your results have not progressed as fast as what I am showing, don’t get bent out of shape. Making a little progress at a time and taking several shots before reaching for the cutoff saw will always yield a faster learning curve. Jumping the gun and heading to the cutoff saw after only taking a shot or two can cost your pocket book more than you would like.
The arrow setup I am using here is the same one I’ve been through several times.
The cut I made on the shafts for this picture shows that I am right where I want to be at this point. The shafts are sticking fairly straight into the target, and the tail-left kick is basically gone. Now, we can start moving back and increasing the distance of the shots. However, I am still not ready to jump way back and will only move back five more yards.
Now shooting at fifteen yards, I have made a switch from the paper with the line to a target which will allow me to see that I am shooting down the center and allows me to pick a spot.
From the picture above, you can see that the shafts are still impacting fairly straight and in line with my sight picture. I made several shots at this distance, and as far as impact, I am feeling good at this point.
However, now that I am back far enough to see some of the flight of the shafts, I am starting to pick up a tail-left kick during the flight. For some of you, this type tail kick may very well look like a big sweeping motion, as though the shaft is shooting around a curve. This is nothing more than your eyes playing tricks on you. In fact, the point is going straight and the tail of the shaft is kicking left. This is a real a mind blower if you are not expecting it.
I will make another 1/8” cut and shoot several more shots before moving further back. What I am looking for at this point is as close to the same results as I was getting at ten yards -- Straight flight and straight impact.
Again, if your results differ, take the time to make several shots and decide whether or not you need to make another cut or more before moving on.
You will also want to watch out for a shifting of the tail kick to the right or impacting the target to the left side of the line on every shot. This can happen when you just cannot stand to being held back and feel you need to cut and run too soon just to be able to get things finished.
After making another 1/8” cut, the shafts are now flying fairly straight and still impacting on the spots. I did not post a picture of this because it would not look much different in a new picture compared to the last one.
In the picture above, I have now moved back to twenty yards. The shafts are still impacting fairly straight and impacting right in my sight picture. However, every time I increase the shot distance, the tail-left kick/sweep seems to creep back in. As you can see in the picture, the shafts have different impact angles. The one on the top is impacting a tad bit straighter than the one on the bottom. This is another reason I suggest using two shafts over one when tuning. The slight difference in the two will start to show at the longer distances. Had I only used one shaft and not seem the tail-left kick/sweep and had it been the one on the bottom, I would have made a tiny cut to bring it back into straight flight not knowing the other shafts could very well be different.
However, I am still seeing a tiny tail-left kick/sweep in flight with both shafts and will make a tiny cut and carry on shooting.
At this point, the shafts may be good enough for some shooters, but not for me. I want to see clean flight and impact.
With impact holding true, I am now concerned with flight, so making another tiny 1/16” cut will most likely be all I need. If you are still seeing a heavy tail kick or sweep, you may want to make a 1/16” cut and shoot several more shots before making another cut. Small cuts will not show progress as fast, but will allow you to see the changes without pushing the shaft to the stiff side before you understand how tuning works.
After making the 1/16” cut, I moved the targets around and shot one arrow at a time to see if I could tell which shaft was which. As you can see in the pictures above, both shafts are now impacting straight in, and the flight at twenty yards is flawless.
The main thing to remember at this point is the dynamic spine has now reached the intended goal and is correct. Any further trimming of the shaft will start to push the dynamic spine to the stiff side. Adding the fletching will slightly increase the dynamic spine of the shaft as the feathers drag on the tail.
If this is your first try at bareshaft tuning, I would suggest that you leave the shafts a tad bit on the weak side. You can always go back and resume the tuning process after you have started shooting the fletched arrows, if you feel they are still on the weak side. Once you see the results of a well tuned shaft, shooting everyday becomes a hard habit to break. In addition, leaving the spine a tad bit weak helps if you find yourself in a position where you can’t get to full draw like you would standing in the back yard or on the shooting line.
With everything in correct dynamic spine, the time has come to fletch one of the shafts for a comparison shot. What you will be looking for at this point will be to see if both the fletched arrow and the bareshaft are flying the same.
To check the comparison shot, I fletched one of the shafts with three 3” feathers. You may want to use longer feathers to start. However, one of the advantages of EFOC or UEFOC is the forward balance point of the shaft. The further forward the balance point, the longer the rear steering arm will be on the shaft. The longer the rear steering arm, the less fletching it requires to correct any possible bad flight normally caused by a bad release.
We will cover feather tuning a little later.
As shown in this picture, the fletched arrow flies the same as the bareshaft. Here again, I normally start shooting back over at ten yards and will work my way back to as much as 25 yards. This was the ten yard shot.
Like before, remember you will want to take several shots to ensure you have everything correct. Shooting only once or twice can lead you to the wrong impression. Also, most shooters take several shots to warm up and to achieve a smooth release.
In this picture, the shot was taken from twenty yards. You can see both the shaft and the arrow are still impacting with the same straightness. If you have followed these suggestions, your results should be fairly similar.
If you have any doubts to the results shown in this tuning workup, I encourage you to give it a try. There is nothing like seeing a well-tuned arrow fly.
A few suggestions, if you are still having trouble:
If this is your first time to try bareshaft tuning and you find yourself still having weak spine issues, you may be shooting a bow which has too deep of a cut in the sight window. A lot of bows today have the sight window cut past center. If this is the case, there is a much easier fix than spending money for stiffer spined shafts. Simply build out the sight window.
A simple and low cost way to find out if this will resolve your problem is sticky backed Velcro which can be found in almost any craft section of your local box store. One layer of Velcro will move the sight window out approximately 1/8”. If further movement is required, simply add on another layer. Once you find the correct setting, you can measure the thickness of the add-on and either replace it with stacked leather that has been glued together and covered with one layer of Velcro or many other ways.
As you can see in this picture, even I made the mistake of cutting the sight window past center when I built this bow sometime ago. The bow was built with the sight window cut 3/16” past center which has now been moved out to 1/8” before center. This adjustment can easily be removed should I decide one day to sell the bow.
Another tip for improved flight comes in the area of fletching size. As I stated earlier, one of the benefits of EFOC and UEFOC is the increased length of the rear steering arm of the shaft. When you increase the length of the rear steering arm, less fletch is required to control the arrow.
Here, I suggest you start with whatever feather length you are comfortable with. For target shooting with fieldpoints, I believe anything over three inches is overkill. If you insist on using long, high profile feathers remember all you are doing is shifting the dynamic FOC of the arrow further to the rear, thus loosing the effects of the FOC you have just tuned into your shafts.
However, as you get ready to test shoot your broadheads you may find more feather is required, and you can tune the feathers to your broadhead flight. Whatever it takes to carry your broadheads will always be plenty to handle fieldpoints.
To tune your feathers to your broadhead, install your broadhead and start shooting at ten yards. Once you see that the feathers are controlling the flight, you can start by trimming ¼” at a time from the front and reshaping the slope with scissors. Continue shooting at ten yards for a few shots, and then back up to fifteen yards. If the feathers still control the broadhead, trim another ¼” and reshape the slope of the feather. Take several more shots to ensure the control is still there. Now, back up to twenty yards. If the feathers are still controlling the flight at this distance, trim another ¼” and reshape the slope. Shoot several more shots to ensure everything in still in control and move further back. When you reach your maximum hunting shot distance, keep trimming and reshaping until you start to see the slightest inconsistency in the flight of the arrow. It may help to have someone watch who knows what to look for. Be sure to shoot several times before making the call of “that’s all folks”.
Now comes the trick that, to me, helps as much as anything on broadhead flight. It is called the turbulator band and is a small band made of thin vinyl. This is the same material as the common arrow wrap used under the fletching, and I use a wrap to make mine. Cut a 1/8” strip off the end of a wrap. Peel the backing and apply ¼” in front of your feathers. Make several shots to ensure the flight is stable. If the flight is not stable, remove the fletching as well as the turbulator band, and replace it with feathers ¼” longer and a new turbulator band. Take several more shots to ensure that everything is right.
The above picture shows not all shafts require the same length feathers and shows the turbulator band.
Several factors come in to play as to how short to make your fletching. Poor release is a major one. Additionally, the size of your broadhead is another because short, wide broadheads tend to show wind sheer more than long, slim heads. The amount of FOC you obtain with your setup is a factor, and even your draw length and length fr your finished arrow is a factor.
Now that you have your broadheads and feathers in tune, the final test will be shooting in different wind conditions. If you did your tuning on a calm day, you will want to double-check everything on a windy day. The set up you found to be the best can often change when shifting wind currents are involved. The design and size of your broadhead can require increasing the fletch size in broadside and quartering wind conditions. Only you will be able to determine this.
“What works for you doesn’t mean it will work for your hunting buddy”
“Everyone should tune to their own bow and shooting style”
Additionally, Dr. Ed Ashby gave us his spin on Tuning the EFOC Arrow at
the 2013 P&Y convention in Dallas Tx, and while they are substantially the
same, you will learn a lot of additional tricks by watching this 38 minute
Additionally, Dr. Ed Ashby gave us his spin on Tuning the EFOC Arrow at the 2013 P&Y convention in Dallas Tx, and while they are substantially the same, you will learn a lot of additional tricks by watching this 38 minute video...
- Dr. Ed Ashby and his Broadhead Lethality Studies
- Ashby .pdf's
- Ashby Jan 2012 Kalamazoo, MI
- Ashby May 2013
- Game Animal Anatomy
- Education Links
- Archery Formulas
- Selecting the Bevel
- Edge Maintenance
- Sharpness & Bloodtrails - Dr Ed
- Tuning the EFOC &
- Arrows for Elk
- Single Bevel Discussions and Opinions
Links of Interest