Arrow Speed
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James from MN asks:Hi Bill, I was wondering if you could explain a little bit about the idea of momentum when it comes to bow hunting. I hear alot about KE and Velocity, but every now and then I come across momentum. So how do you calculate it, whats a good number to have and do you think its more/equal/less important than KE or velocity? The reason I ask is because when using a arrow speed calculator, i found that I can use a bit lighter arrow and get more arrow speed with the same KE. But I was wondering if this is where the importance of momentum comes in.....? SO my final question: Do i take a 25gr light arrow for extra speed with same KE or heavier arrow with same KE but a 10fps slower....? Thanks!Winke Responds:James, I studied mechanical engineering in college and when I got out, I always felt momentum was the true indication of how far an arrow would penetrate. You use the law of conservation of impulse and momentum to determine the force required to stop the arrow. It translates better into determining how much force of resistance would be required to slow an arrow over a set period of time (the equal but opposite impulse that occurs on impact). To be honest, I have forgotten much of this stuff, but I'll take a cut at it from what I remember. Momentum is simple: it is just mass times velocity. Getting the units right is important. It is mass in slugs (American system) and speed in ft per second. Slugs are the weight in pounds divided by 32.2. There are 7000 grains per pound. So for a 400 grain arrow traveling 280 fps the momentum is roughly .5 lb-sec. So that means for very simple calculations, to conserve the momentum on impact, it would take just 1/2 pound of resistance acting on the arrow over a second of time to stop it. However, it would take 250 pounds acting on the arrow to stop it in 2 milliseconds - about the time it would take to go through a deer. If you hit the shoulder it is likely that you are dumping 500 pounds of force on impact. Once you factor in all kinds crazy physics describing the hydraulics and forces of the arrow going thorugh the deer, it gets pretty hairy to say exactly how far each level of momentum would penetrate. I am not even sure I could still do that, and I certainly don't have the time to try, but the point is, I feel momentum is the best indicator of penetration. I am not sure of the best range for that number. I haven't thought about it enough, but surely something in the .5 range is at least good.
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cameron bender from PA asks:mr.winke, i really enjoy all of your hunting shows, keep up the good work. i'am shooting only 40 pounds at 29" draw length. i wanted to know how much speed you increase, per 1 inch of draw length. i'am also interested in your opinion about using the 85 gr. magnus stinger 4 blade, or do you think i should use the 2 blade. thank you.Winke Responds:Cameron, I appreciate your support and hope we can keep offering advice that helps you to become a better deer hunter. You won't get a lot of speed with a 1 inch increase in arrow speed maybe about 5% roughly. More important than getting that speed is the need to have a bow that fits perfectly. I shoot much better with a bow that fits me perfectly and even 1/2 inch either way (too long is worse than too short) will reduce my accuracy. The right draw length is the one where the elbow on your release arm points straight away form the target. If it pulls around behind you at full draw, even slightly, you won't shoot as well. Magnus makes great heads, but I would stick with their 2-blade at this point. Go for maximum penetration until your draw weight increases higher.
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Dale from NY asks:Hey Bill, first off just wanted to say great job in everything that you do. I have enjoyed all your writings thru the years and the show is absolutely amazing! Keep up the great work! Here is my question: I shoot 64# and a 27.5" dl. I currently use an easton axis arrow which weighs 396 grains and shoots 272 fps. If I use the KE formula my arrow sets up at 65# KE. Today, I tried out an easton flatline shaft that weighs 342 grains and chronoed 288 fps. Using the KE formula that arrow combo = 63# KE. I believe that the increase of 16 fps outweighs the loss of just 2# KE. A close friend says that you should always shoot the heavier arrow shaft. What are your thoughts on this? Thanks for your insight.Winke Responds:Dale, Thanks for your support. I think as long as the bow is not too loud, you are OK. You are starting to get a bit lighter than I like. As you get down around the 5 grains per pound of draw weight (you are at 5.3 grains per pound) you run the risk of creating too much vibration. There is a point when you start to incur damage on your bow because the arrow doesn't soak up enough energy. Take it to the extreme - a dry fire is like shooting a 0 grain arrow. So obviously there is a sensible lower limit somewhere - I have always felt that 5 grains per pound is that sensible lower limit. Otherwise, giving up 2 ft-pounds of KE is not a killer. Just be careful how light you go.
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rob from IA asks:Hi Bill after watching your lateest video on your arrow issues i thought of a question. i shoot a 70# pse bow according to what i have read the arrow should be no lighter than 350 grains. (360 to be super safe)right now i shoot 400 grain arrows. how particular do you get with your arrows? is there enough benifit in the extra speed you gain to spend the time getting my arrows down that low? or are there some problems that arise that are just as bad as not having the throttle wide open on the speed chart? thanks RobWinke Responds:Rob, This is another question I answered for another viewer. Please refer to the other Ask Winke questions. The simple answer is yes, there are some problems that come with making your arrows lighter and there are some benefits that come with making them heavier - there are definitely tradeoffs. Good luck.
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scott from WI asks:Hi Bill Great Show.I shot a mathews outback 27"draw 60#max hha single pin sight goldtip xt hunter 55/75 tip/100grain 3blade muzzys.I use a ripshot/turefire release. I hit 2 deer this past year that i didn't find do to lack of arrow penetration.One deer was boardside hit shoulder. Sec. quartering away.Is my set wrong? Thanks ScottWinke Responds:Scott, I don't see any problem with the setup. I would guess the shoulder shot simply was the result of the bone hit. The second one is not so obvious. My guess is that you hit something hard or skipped off a rib if the shot was quartering sharply enough. It is hard to know for sure, but I would not fault your choice in gear. Good luck.
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marc from MI asks:Bill, I've never been to hung up on arrow speed and have usually gone toward the heavier end of the spectrum. But as I've gotten older and come down in draw weight have started to pay attention to some of the details more. My current set up is an 07 Bowtech Commander (60lbs at 31 1/2" Draw.) CE Maxima's 350(8.9gpi)w/Blazers and 100gr Tru Fire T1 3blade broadheads. My math tells me I'm at an approx 420gr arrow. Arrows hit the same as field tips out to 40yds(My max range) Anything worth tweaking in your mind? I have never shot a chonograph but I did shoot a Dart system last year. Its estimator said 292fps. What are your thoughts? And will you be in Grand Rapids, MI this year?Winke Responds:Marc, I am guessing the Dart is overstating your speed. Not that this bow is slow, but you are shooting a fairly heavy arrow for your draw weight. I would guess you are closer to 270 fps. I like fast arrows because I can shoot them through smaller openings, they smooth over some small errors in range estimation and they reduce how far a deer can drop if it reacts to the sound of the shot. For that reason I like to shoot as fast as I can without making my arrows too light or my brace height too low. In your case, you could drop your arrow weight slightly (40 to 60 grains) and gain some more speed. In the grand scheme of things, I wouldn't say it is necessarily worth it. Next time you buy new arrows, consider a lighter style. Stay above 350 grains of total arrow weight (at your current draw weight) and you will be fine. By the way, I will not be in Grand Rapids this year. I am not planning to attend any deer classics personally, but MW will be at a few of them using the local pro staff. Good luck.
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Mike from AL asks:I was wondering why there is such an importance put on speed when sound travels at 1129 fps?(i googled it.)That's 4 times faster than the average hunting bow.The things that are advertised to sell bows are the same things that make a bow less accurate.lighter bows move around more,bows with shorter brace heights are more inclined to torque.So with that being said should'nt bow companies stress accuracy and how quiet a bow is?Winke Responds:Mike, You are correct in all of your statements but there is a balance point where speed makes sense. As you say, as long as you aren't giving up much pure accuracy to get it, a faster arrow is better for three reasons: 1. It allows you to shoot through smaller openings and reduces the deflections from branches above your line of sight when shooting through typical openings. 2. It reduces how far a deer can drop at the sound of the shot. It is very hard to make a bow so quiet that a deer can't hear it, but you can reduce how far it drops to load its legs by shooting a faster arrow. 3. A faster arrow reduces the affect of small errors in range estimation. Again, if your shooting form is good, you can benefit from a faster arrow. My advice to everyone is to shoot a bow with a modest brace height (around 6 1/2 to 7 1/2 inches) and as much draw weight as they can comfortably hold at full draw for at least 2 minutes. Ideally, it is a longer, more stable bow, but that tends to be a matter of splitting hairs. A 30-inch bow may not be a lot less stable than a 32-inch bow but it will be noticeably less stable than a 38-inch bow. So in other words, a couple of inches of either way in bow length is not worth worry about. All your points are good ones.
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Matthew from OK asks:My friend who farmas my land says he has been seeing bucks all the time. Yet when i deer hunt, all i see are does. What might be the cause of this?Winke Responds:Matthew, He may be pushing them from cover as he works past them and those same deer may not be moving during the day, not naturally, at least. Also, when someone covers a small area from a single tree stand they are not going to see as much as a person who covers lots of ground with equipment or when driving to and from the area. I learned that the hard way after being frustrated for years by people telling me of seeing big deer crossing the roads near my stands, etc. We cover a small area from a tree stand, we just aren't going to see as much as someone on the move. Don't be discouraged, it is all part of the game.
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jordan from MO asks:Hey Bill, I asked you what you thought of the hoyt powerhawk a couple weeks ago and I just got it. I love it and i think its a great bow. The Bow is advertised as shooting around 300 FPS. I'm not that into speed but I would like to know how fast it's actually shooting. I got it set at 50 pounds with a 28 inch draw and im shooting easton 400's with 75 grain tips. Could you give me a ball park of the FPS?Winke Responds:Jordan, Here is a way for anyone to figure out arrow speed without a chronograph. Use your 20 yard pin but stand back at 40 yards. Aim at a small spot on the target with the 20 yard pin and make good shots. Don't try to hit the spot, just try to make good shots using the 20 yard pin from 40 yards. Obvioiusly you are going to shoot low. Now measure the distance from the aim spot to the center of your group. At 260 fps, the distance will be 10.3 inches. At 270 fps, the distance will be 9.5 inches. At 280 fps, the distance will be 8.9 inches. At 290 fps, the distance will be 8.3 inches. At 300 fps, the distance will be 7.7 inches. At 310 fps, the distance will be 7.2 inches. At 320 fps, the distance will be 6.8 inches. At 330 fps, the distance will be 6.4 inches.
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Jordan from IN asks:hey Bill loving the shows so far and can't wait for the seasons to get into full swing. I have been out practicing with my bow non stop lately and started noticing at around 35 yards and beyond my arrows are starting to turn sideways and its affecting my long range accuracy. Am i using too light of arrows or is my bow just not powerfull enough to shoot them? i shoot a pse stinger at 50#. Thanks and good luck this year!Winke Responds:Jordan, Thanks for your support. Boy, without seeing the setup it would be really tough to tell. However, there are too things to consider. First, if it was windy the arrows will fly sideways. That is because the wind will push the fletching harder to the side than the shaft causing the arrow to turn in flight. This is one reason that I switched to mechanical broadheads back in 1995. With fixed-blade heads, the arrow will then start to plane into the wind. With mechanical heads it drifts downwind. I can play the drift if necessary, but it was really sketchy trying to determine how much the arrow would plane into the wind. Second, you will need to paper tune the bow to see what the arrows are doing a few feet after they leave the bow. Cut out the bottom of a cardboard box and tape a piece of printer paper across it. Shoot through the paper into a target. Stand about five or six feet from the paper and make sure the target is at least three feet past the box so the arrow is clear of the paper before it hits the target. The way the arrow tears the paper will tell you how it is leaving the bow. Give that a try and see what you learn. Good luck.
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Matt from IA asks:Bill, after having the biggest buck I have ever seen in the wild duck my arrow, only sustaining a flesh wound I have been analyzing, maybe over analyzing, my setup. I have been thinking of going to a lighter arrow, as I see you have. I just read an article of yours where you suggest 6 gr. per pound of draw wt. At 70 pds that,s 420 gr. My arrows, 340 spine 28.5" with every thing, come in at 425 according the the manufacture's specs. In your view, and I understand it, I should not be going lighter correct? The only thing I have to remove from my string is the peep tube. I intend to try a meta, I saw your article about that in the same magazine. I have my limb bolts pretty much bottomed out and my arrow as short as it can go. I'm not shooting the fastest bow but it's no slouch and I like it. Have I reached the limits of what my bow can do? I know speed is not everything but your input would be greatly appreciated. Also, do you shoot with one eye closed or both open? ThanWinke Responds:Matt, If you watched the shows this year you know I faced the same problem. I went to a slightly lighter arrow (from the Full Metal Jacket to the N-Fused Axis). That picked me up maybe 7% in speed, not enough to make a huge difference. I think you are about maxxed out on what you can get from that bow. However, you can shoot a lighter arrow. The bow will probably handle it. The problem is if you do a lot of off-season shooting, the vibration will increase from the lighter arrow and the accessories will take a pounding. If everything you are shooting is rock-solid, you can drop down to 5.5 grains per pound and do fine. The IBO 3-D shooters are down to 5 grains per pound. I did that one summer with a 105 pounds bow and ACE arrows. I was shooting 360 fps before that number was even a dream. I bent axles all the time and split limbs. I did it more just to see what would happen than anything else. I was probably lucky not to come away with a big scar on my face from that bow! Anyway, drop down a bit in arrow weight if you like, but the real solution to this problem is not going to be something we can purchase, but rather in our ability to read the situation and adjust our aim points accordingly. I am afraid I am still guessing on that one, but beyond about 20 yards, the possibility of a high hit from dropping goes up dramatically if you don't adjust. Good luck.
