American bison and arrow building
The brown bear arrow thread got me to thinking and rather than posting this in his thread I started this one sonce its on par with what he is asking.
Iíve was asked by a friend to outfit him with a arrow and broadhead combination for a February Buffalo hunt out West. He was using his current whitetail bow but wanted more than the 350 grain arrow/broadhead set up he uses for deer. I agreed with that. Everything I have heard and read about Bison is that you should be shooting for the heavy carpet that covers the front shoulders. I would expect that this hair is thick and matted and since the hunt will take place in February, that it might also be ice covered. For this reason, I wasr shooting for an arrow weight over 700 grains.
After looking around for arrow shafts, I settled on Carbon Express Heritage with the wood grain look. These shafts weigh around 12 grains per inch. Next, I picked the Wensel Woodsman as the broadhead for this hunt because I wanted him to use a strong, cut on contact head. The 3:1 aspect ratio of the woodsman means greater penetration. I ordered from 3Rivers, a half dozen 125 grain Woodsmans and since he will be screwing these into a carbon shaft, I also got some 100 grain steel adapters that are needed to mount a glue on style head to a carbon arrow. For added weight, I also got 50 grain brass arrow inserts instead of the normal 15 grain aluminum inserts. I also got him some brass weight washers.
after reading Dr. Ashbyís report on extreme FOC arrows and their increased ability to penetrate, wanted to create a front heavy arrow (FOC moved forward) . What I built added up to 285 grains at the tip alone. The shafting weighs 12 grains per inch and he uses a 29 inch shaft for 348 grains of carbon. He is using a luma nock and I fletched the shafts with (3) 5 inch barred turkey feathers which added another 30 grains putting us at 663 grains so far.
Since my son and I are working on a broadhead collection, I used one of the Wensel Woodsmen to do a little testing. The woodsman has a very sharp tip but bison bones are big so I filed a secondary tip angle which shortened the head by about an 1/8 of an inch which will make the tip less likely to bend or curl upon impact with a large bone. I was planning on a worst case scenario in that he hits a rib on both sides of the bison.
Next, I took the woodsman and sharpened it to a fine edge and then lapped it on ceramic plates to get a mirror finish on the cutting edge.
In an effort to show my friend the benefits of a cut on contact head, I set up an experiment where he and I used two very common and popular heads on the market. A Muzzy and a Thunderhead that were in the collection. I used a short length of shaft and some sponges to keep the arrow from sliding around on the scale.
I used a very thick and heavy piece of boot leather as the test medium. I placed the leather over each broadhead and by holding the leather out at the edges, pressed down until the head passed thru the leather. My friend watched the scale to check the poundage. I started with the Muzzy. I pushed down until I reached 30 pounds of force and I could not get the tip to go thru the leather.
Next, I used the Thunderhead and when I applied 24 pounds of force, the head came thru but ripped the leather before the blades could start cutting. The thunder head hole is to the left on the picture above.
Lastly, we used the Woodsman and It went thru the leather so fast and with such ease that we repeated the test several times to make sure we could trust the results. After 4 tries, we kept coming up with the same results. It took only 6 pounds of force to slice thru the leather and there was no tearing, just clean cuts. There are other heads on the market with cut on contact tips that are just as good but I think the Woodsman was a good choice for this hunt.
In order to reach the 700 plus final weight, I have decided to use a few 27 inch lengths of .065 string trimmer (weed whacker) line that will be placed inside the arrows. This will ad weight from front to back but will not change the arrow spine which is 350.
Once the shafts arrived I cut them to length and epoxied the 50 grain brass inserts in place. The hunter asked that I use barred feathers and crest the arrows. The colors he picked were black, red and silver cresting to match the fletching.
While the cresting was drying, I assembled the 125 grain Woodsmen heads and the 100 grain steel adapters. I also placed 2 brass weight washers on the heads. Total head weight: 235 grains.
Over the course of the day I was able to get the first two shafts fletched.
As I said, to boost the arrow weight, I am messed around with string trimmer (weed eater) line. 4 strands is the max I can fit inside the shaft.
When I finished the arrows I contacted the hunter and he came over. We shot a few test arrows in my shop. The final weight came out to 760 grains. By using (4) 10 inch lengths of weed eater line bundled together and positioned in the front of the shaft, I was able to get a 15% FOC.
All the heads are razor sharp and ready to go. I had him take a few shots through the chronograph and he was consistently shooting 200 FPS with his 70 pound Jennings. He practiced with the broadheads for a few weeks prior to the hunt.
His new arrows deliver 67 foot pounds of KE at point blank but more importantly, they will have .674 Lb/Sec. of momentum even at 40 yards he will still be at 63 foot pounds of KE and .654 Lb/Sec. momentum
His whitetail arrows weigh 353 grains and shoot 285 FPS, giving him 64 Foot pounds at point blank but only .446 Lb/Sec of momentum. At 40 yards, he drops to 55 Foot pounds and .414 Lb/Sec of momentum.
That is a 150% increase in momentum at point blank and 158% increase at 40 yards. These will be deep driving arrows. Now he just has to hit the right spot.
The Bison hunter when he had his bull. He got penetration on both sides but the arrow did not completely pass through and exit the far side. He got both lungs and the heart and the beast broke his arrow in 3 pieces.
Live weight 2,400 pounds, Hanging weight (without head, hide, hoofs or guts) 1,109 pounds. Total boneless meat is 717 pounds. It scored in the SCI top 20.
the guy's partner got his bull with a restored Sharps rifle and put 6 shots in the boiler room before his bison went down.
The hunter stopped by my house today to drop off some pictures of his bison and to show me the arrow (all 3 pieces of it) The broadhead was as sharp and as good as new.
As stated, the entire head came thru the far side but the arrow did not completely pass through and out of the bison.
Someday I hope to go after such a great animal myself. I would love to try it with my longbow.
I may be having an acute attack of the stupids but I am having a hard time understanding how you manage to keep ten inches of weed whacker line positioned at the front of the arrow during the shot. If you simply slide the bundled line inside the shaft and do not glue or otherwise fix it in place I would imagine that, at the shot, static inertia of the line within the accelerating shaft would result in the line sliding backward (relative to the forward moving shaft) where it would end up at the nock end of the arrow. Otherwise, your descriptions are very clear.
I am experimenting with weight tubes and inserts in hopes of maximizing my own arrow delivery system.
Thanks in advance for clearing this up for me.
The line was wedged pretty tightly into the shaft with tape. I struggled to get the bundle into the shafts so I donít think it would slide inside the arrow tube.