4 Steps To Perfect Broadhead Flight
March 14, 2003
Going From Field Tips To Broadheads Requires Arrow Tuning On A Higher Plane.
Thousands of bowhunters will suffer hours of frustration this fall, and that's before they get into the woods. I'm talking about the unfortunate souls who will have trouble making their broadheads fly true.
I've seen their frustration and desperation. They'll fool with their setup for days only to find they still can't get their broadheads to group or hit where their field points do. Sadly, there's little reason for this struggle. Yes, broadheads are more difficult to shoot accurately than field points, but making broadheads shoot well doesn't require a Ph.D. or years of experience as a bowsmith. It only requires that you pay attention to certain details.
"What details?" you ask. That's what this article is about. Much can be learned about bow tuning for broadheads by observing the arrow's front-of-center balance point, making the right fletch choices and knowing how to check broadhead alignment. Follow the four steps listed here, and the odds are your broadheads will group better than ever.
The Well-Tuned Bow
The first thing you have to do is make sure your setup is truly tuned. Don't be fooled into thinking that your bow is in tune because you can shoot tight groups with field points. Field points can be very forgiving, and it's possible for an out-of-tune bow to shoot one-inch groups at 20 yards with field points. (This is why mechanical broadheads tend to group better. They're much more like field points.)
Most broadheads, however, aren't going to let you get away with bad tuning, especially if you have a fast bow. This is because the blades on a broadhead can act like wings and steer an arrow all over a target face. Launch an arrow poorly and the blades will catch air and drift off target right from the start.
Due to space requirements, I cannot go into bow tuning here, but two great sources for tuning guidance are Larry Wise's book Tuning Your Compound Bow from Target Communications, or Easton Technical Products also has a great technical bulletin on tuning that's very easy to follow.
Make sure to re-check your arrow spine before you begin tuning. I constantly come across bowhunters who are using the wrong size shaft. Having an arrow that's too stiff or soft will make it impossible to achieve perfect broadhead flight. Make sure to consider all the variables that influence spine stiffness. According to Easton, the variables are:
- shaft size (diameter and wall thickness
- shaft length (+/- 3â„4 to one-inch can significantly change shaft stiffness)
- weight of the broadhead to be shot (+/- 25 grains can significantly change shaft stiffness)
- draw weight of the bow (+/- 2.5 to five pounds can significantly change shaft stiffness)
- archer's draw length (certain shafts become significantly weaker when cut past 28 inches)
- string material (Dacron strings are slower and require a slightly softer arrow, for example)
- type of bow (recurve or compound with a wheel, soft-cam or speed-cam)
- finger or mechanical release
(finger shooters require a slightly stiffer arrow)
- bow length (bows less than 40 inches in length require a slightly stiffer shaft)
- overdraw length, if used (three-inch-plus overdraws require a slightly stiffer arrow)
If you shoot Easton shafts and have a computer, it's worth purchasing Easton's "Shaft Selector Plus" program to help you select the right shaft. The program is much easier to use than a chart. Easton's website, www.eastonarchery.com, also has a free shaft selector, but it does not take as much information into account as the program. If you don't have a computer, check to see if your pro shop has the program. If you have to use a chart, or shoot another make of arrow, be certain to read the instructions on shaft selection very carefully. Finally, keep in mind that your setup may vary enough to require a different size shaft than the one recommended.
Now that you've got the right arrow, you need to tune the bow to the shaft. Note that I wrote, "You need to tune the bow." You don't have to be the brains behind the tuning, but you can't have your local archery shop do this for you. This is especially true if the shop's idea of tuning only involves setting nock height and moving the arrow rest a little. This isn't tuning; it's just setting up the bow for tuning.
Nor can you have the shop pro paper-tune or bare-shaft-test your bow for you. You have to do the paper/bare-shaft/group testing, as other people are likely to shoot your bow differently than you do. A true tune can only be achieved if you're the one doing the shooting. If you don't feel confident about the mechanics of tuning, have the shop pro adjust the bow while you fling arrows.
You don't have to tune with broadheads at this point; field points are fine at this stage. Later, you'll want to shoot at long range with broadheads (anywhere from 35Ã‚ — 50 yards depending upon your skill level) to test your tune. If you've completed the other steps in this article and are still having trouble getting your broadheads to group, then you probably still have a tuning problem. The same is also true if your field points and broadheads have a different point of impact.
The Right Fletch
A lot of bowhunters go for extra speed by reducing arrow weight. That's OK, within reason, but don't save weight by cutting back on the size of your fletch. Arrows with field points can get by with very little fletch guidance. The same is not true in regard to broadheads. You need a lot of fletch to counteract any attempt by the broadhead to steer your arrow from the front of the shaft.
The general recommendation is that release shooters use five-inch vanes or four- or five-inch feathers. I've found you can sometimes get away with four-inch vanes and three-inch feathers on arrows weighing less than 425 grains, but it never hurts to have a little extra guidance. You should also consider that you might need extra guidance on lighter shafts because they're going to be launched from your bow at a higher velocity.
Feathers, by the way, do offer more guidance than equivalently sized vanes. This is because their rougher surface offers more wind resistance. Traditional shooters should almost always go with five-inch feathers or possibly a four-inch, four-fletch combination. Finger shooters need all the help they can get to counter the initial wobble of a finger-released arrow, and shooting off the shelf requires a fletch that collapses when it hits the shelf. Compound shooters who have a finger release are also probably better off using feathers. Whether you're using shooting fingers or a release, you should have a helical setting on your fletch. You never want a perfectly straight fletch when shooting broadheads. Helical fletching does a much better job of stabilization. A helical fletch causes the arrow to spin like a well-thrown football. This moderates any attempt by the broadhead to steer the arrow.
Bowhunters who use small-diameter carbon shafts may have trouble with their fletching clearing the arrow rest when using a helical orientation. In this case, the best choice is to select a straight offset of about one to three degrees. Incidentally, this is how most arrows prefletched by the manufacturer are oriented. Despite the campfire stories you might have heard, feathers and/or a helical fletch will not slow your arrows significantly downrange. Feathers are initially faster and only start losing speed once you're well past typical hunting ranges (50 yards). Helical settings on vanes cause almost no loss of speed at hunting ranges. So, err on the big side if you're uncertain about what fletch to use.
What is FOC?
If there's one variable of broadhead flight that's often overlooked, it's the arrow's front-of-center balance point, or FOC. In practical terms, FOC determines how much leverage the fletching has to correct the arrow's flight. The farther forward the balance point is from the center of the arrow--the FOC point--the longer the lever the fletching has to work with and the easier its job. The general recommendation for FOC is 12 to 15 percent for broadhead-tipped arrows. This compares to a recommendation of eight to 11 percent for field points (for pure target applications). The difference in suggested FOC is due, in part, to the longer length of a broadhead. It's also due, in part, to field points not having the ability to steer an arrow like a broadhead can.
Finger shooters, and those shooting shafts less than 26 inches in length, should probably look for a higher FOC. This is because shorter arrows are inherently less stable, and finger shooters, once again, need a little extra help to correct the normal arrow wobble upon release.
Note that it's possible to shoot very accurate groups with field points with less than eight percent FOC, but again, field points are more forgiving than broadheads. Just as with fletch size, it's better to err on the large side with FOC. You don't want to go overboard, though (past 18 percent). Too much FOC makes your arrows point-heavy and less aerodynamic downrange.
How do you figure out your arrow's FOC? The Easton computer program that I mentioned earlier in the article has a calculator that will do the job for you. If you don't have the program, you have to do the math yourself. Here's how I do it, and since I'm no math wizard, it's pretty simple. The formula is: [(ABP Ãƒ· TAL) - .50] x100 = FOC%
ABP is the distance to the arrow's balance point from the nock of the arrow, and TAL is the total arrow length. (This formula is different than the one recommended by the AMO. It provides the same answer, but I've found it a little easier to use.) All you need is a tape measure and something to balance an arrow on (like a pencil) to use the formula. First, balance the arrow and mark the balance point with the pencil. Then measure from the throat of the nock (where the string fits inside the nock) to the mark you made at the balance point. This is the arrow's balance point (ABP).
Next, measure the length of your arrow from the throat of the nock to where the insert goes into the shaft. This is the total arrow length (TAL). (If you use carbon shafts with outserts, measure to where the point screws in.) Finally, input the figures into the FOC formula. For example: If you had a 30-inch arrow that balanced at 19 inches, the formula would read: [(19Ãƒ·30) - .50] x 100 = 13.3 percent FOC.
What do you do if your arrow's FOC is too low? You might have to use a heavier broadhead or change shafts. Be careful here. Adding a heavier head can change arrow spine, meaning you might have to use a different arrow or, at the very least, re-tune the bow.
If you really don't want to change shafts or components and you're shooting vanes, try switching to feathers. They're typically much lighter and could move your FOC forward by two percent or more. You can also try using a lighter nock.
Straight To The Point
The final step is to make sure your arrows are perfectly straight and that your broadheads are perfectly aligned. The easiest way I've found to do this is with a tool called The Arrow Inspector from Pine-Ridge Archery. One quick spin on the Arrow Inspector will reveal even the slightest bend.
This tool is also invaluable for checking broadhead alignment. It will reveal whether your insert is square in the shaft and/or if the broadhead is bent. It's perfect for mounting traditional heads too. While I've never had bent broadheads from my any of my favorite manufacturers, it never hurts to check each and every head. A warped broadhead or a bent arrow can result in terrible arrow flight.
Note that I didn't mention anything here about aligning the broadhead's blade with the fletch. This is another campfire story that's been debunked by scientific testing. Those individuals who insist this makes a difference have likely experienced a poorly aligned insert. Rotating the insert to put the broadhead's blades in line with the fletch probably improved the broadhead's overall alignment.
Also, note that nowhere in this article did I mention switching to another type of broadhead if things weren't working out. Granted, some broadheads fly differently than others if the bow's tune is off, the FOC is wrong or the fletch is too small, but you should be able to get almost any head to fly tolerably well if you take all the variables into account.
If you're still having trouble, go back over these four steps again. In particular, recheck your tune and consider adding a little extra fletching. Be aware that a modification in one step can influence other steps. For example, switching to a heavier head to improve FOC can make a shaft too soft and change your tune. Note that all of the above steps apply to shooting mechanical heads too. While they're generally easier to tune than fixed-blade heads, they're still not field points. I hate to say it, but if you're not willing to work a little to get fixed-blade heads to fly like they should and are still going bowhunting, then you're probably better off using a mechanical head. They may not penetrate as well as conventional heads in all situations, but they're more likely to hit where you're aiming if you're not set up properly.
Getting your broadheads to fly true shouldn't be a study in frustration. A little attention to detail goes a long way. After only one afternoon of fun on the range, you should be ready to hunt. Once your equipment is tuned, don't complain to me if you're soon cutting the vanes off your arrows because your broadheads are grouping so well.