In a previous post I talked about paper tuning an old compound bow. Never one to leave well enough alone, I decided to go back and recheck the tune on my traditional bows while I was at it.
First up, my Howatt Savannah.
Tuning the arrows
In the years since my initial attempts at arrow tuning, I’d noted a very slight tendency towards a “nock left” impact.
According to my well-thumbed copy of Shooting the Stickbow, this meant that my arrows were slightly too flexible–too bendy–for this bow.
Or in technical terms: these 29 1/2″ Easton Axis Traditional 500-spine carbon arrows were “underspined.” The resulting arrow flight was inefficient, robbing me of energy on impact.
I set up my high tech paper tuning station to confirm my findings.
If you’re going to do a lot of paper tuning, you can build a PVC frame and attach a roll of butcher paper so it’s always handy. My setup is somewhat cumbersome, and the recycled legal paper I use is a little stiff (which tends to exaggerate the tears), but it works well enough for our purposes.
I paced off 15′ from the paper and shot enough arrows to confirm that I indeed had a slight nock left tear.
The Easton spine chart recommended a stiffer arrow for my longbow than the 500s I was using, but I’d convinced myself early on that 400s were too stiff for my bow (spine is a measure of arrow deflection, so lower spine = stiffer arrows).
This time around I decided to order some 400s and see if I couldn’t get them to work.
But arrows are expensive and I already had a bunch of the 500s, so I wanted to try and tune them, too.
I couldn’t make arrows stiffer, but I could make them act stiffer by means of various cunning tricks. In other words, since static spine was fixed, I would adjust dynamic spine.
Referring again to Shooting the Stickbow, I changed from 125 grain arrowheads to 100 grain. Reducing weight up front makes the arrows bend a little less coming off the string, as if the arrows themselves were magically stronger.
You can see the upper tear is shorter than the lower.
There was still a little nock left tear remaining, but I didn’t want to go lighter than 100 grains on the arrowhead to fix it: while light arrows are faster, they lose speed quicker and therefore don’t hit as hard.
Instead I cheated and added a 5 grain brass washer to the nock end of the arrow, which also stiffens dynamic spine.
I ended up with a smaller tear: not quite a bullet hole, but an improvement over what I started with.
Straighter arrow flight out of the bow means the fletching–feathers–don’t have to work as hard, creating less drag. More efficient flight means more energy and better penetration on target.
The ultimate test of arrow flight, in fact, is bare shaft testing, in which you shoot unfletched arrows along with fletched to see if both group together.
Since I order my arrows pre-cut and pre-fletched, this would entail removing the fletching from some of my good arrows, which I was loath to do (which helps explain why I ended up shooting underspined for all those years).
If you’re like me, however, you’ll eventually damage the fletching on one of your good arrows. Rather than attempt a repair, cut the feathers off and replace them with an equivalent weight electrical tape wrap, then set that arrow aside for future bare shaft testing.
If bare shaft arrows group consistently with your fletched arrows at 20-30 yards, the arrows are tuned for that bow. Broadheads, which tend to exacerbate crooked arrow flight, resisting the streamlining effect of the fletching, should now group well also.
If not, you can fine-tune further.
I shoot these same arrows out of my other bow, a 55-pound pull Samick Sage recurve. By strange coincidence, tuning for one generally works for the other, so I get double duty out of my arrows.
This is not usually the case: different bows, like gun barrels, are a law unto themselves, needing carefully-matched ammunition to operate at their best.
Sometimes it’s better to be lucky than good.
In my case, after tuning arrows to a standard that works well for both bows, I can further tune each bow to suit the arrows.
Tuning the bow
The brace height on my longbow has been at 8″ forever, which is near the top of the recommended range.
I thought the bow might be happier at a lower brace height, closer to a median value.
Lowering brace height boosts arrow speed slightly, at the cost of “forgiveness”: since the arrow is on the string longer, it’s important to hold good form for just that extra instant.
I was willing to give it a try.
The cheat sheet in Shooting the Stickbow says that lowering brace height stiffens dynamic spine. Undaunted, I unwound two twists from the bowstring, lowering the brace height by almost 1/8″.
Paper tuning showed that my “slightly weak” arrows were now “slightly stiff.” Also, loosening the string raised my nocking point slightly, resulting in a nock high tear. I tried shooting from below my nocking point, but that caused a nock low tear.
DISCLAIMER: you can make yourself dizzy chasing trends during paper tuning, especially with traditional bows which can be particularly sensitive to variations in shooting form. Take your time, take multiple shots–varying the range if possible–before changing anything. Bare shaft tune afterwards, if you can, to verify.
I needed to split the difference in nock height (when paper tuning, you should correct nock high/low errors first to keep potential fletching clearance issues out of the mix).
I slid my nocking point an eighth of an inch down the bowstring, using an arrow nock to push it, then shot again.
Now I was (mostly) level, but still slightly nock right.
I added one twist back onto the bowstring and tried again. Now the slight remaining nock high tendency was gone, and I was back to slightly nock left.
When the tears get down around half an inch, you may need to put Sharpie (or lipstick, if you prefer) on the arrow point to help you tell nock left from nock right tears.
My 400-spine arrows arrived, and proved to be less stiff than the excellent-for-the-price Cabela’s 400 Stalker Xtremes I’d experimented with back when I first started shooting.*
*You might think that arrow spine–deflection–would be consistent across different brands. If so, you’d be wrong: in this example, both Cabela’s 400 and 500 spine arrows were noticeably stiffer than their Easton counterparts.
I found that 200 grain arrow points kept the dynamic spine on the Easton 400s just slightly stiff (top), while my 500-spine Eastons remained slightly weak with 100 grain points (bottom).
If you’re really trying to maximize arrow performance, of course, you should concentrate on tuning one type of arrow to one bow, then cull any individual arrows that underperform.
In this case, I was content with improving arrow flight for differently-spined arrows on both of my bows, allowing me to shoot faster, lighter arrows at paper targets while having heavier projectiles tuned and ready for more dangerous game…
