Primitive Archer
Main Discussion Area => Bows => Topic started by: Kegan on November 14, 2009, 01:01:27 pm
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Besides stiff and light tips, what are some other factors for increasing dry fire speed?
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Dang Kegan, I'm not even going to say those words together. _____ _____ speed........... ;) The less mass you have the better so shorter lengths make a difference.
I rarely dry fire at a target or deer so I guess I don't really worry about it. ;D
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I meant more along the lines of dry-fire for flight shooting. I don't think my bows would forgive me if i tried to actually dry fire them :D
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String weight.
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What do you mean by "dry-fire"???? because I think of a dry fire as shooting the bow with no arrow....and I know Ive always been told that that is horrible on a bow
-Ky
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Pat- I'm making my FF string even smaller lately too ;D.
Ky- basically, but still with a light arrow in this case. When shooting lighter arrows, like for flight shooting (or in my case, just lighter than 8-10 gpp), the bow itself can't get in the way of the recorvery, so the lighter arrows can actually move faster. I'm slowly becoming a speed freak, and the easiest way to get speed is light arrows. Now to design some bows that shoot light arrows properly :)
I've made bows that didn't shoot light arrows any faster than heavy arrows. So I'm looking for design characteristics to include/exclude.
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Kegan, you might contact Steve Gardner. He wrote the article in TBBIV about his mass theory plus, Steve is a flight shooter.
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I'm not sure of the relevance of this dryfire concept, if you should never dryfire a bow????
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I'm not sure of the relevance of this dryfire concept, if you should never dryfire a bow????
Whomever said you should never dryfire a bow is talking about hunting bows. These are flight bows and it is entirely different. They might shoot a 75 grain 20" arrow, which is the same as shooting no arrow. The difference is that the bow was made for shooting a couple of arrows a long way. If it beats the world record it did its job so the damage done while shooting is of little concern.
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I'm not sure of the relevance of this dryfire concept, if you should never dryfire a bow????
Whomever said you should never dryfire a bow is talking about hunting bows. These are flight bows and it is entirely different. They might shoot a 75 grain 20" arrow, which is the same as shooting no arrow. The difference is that the bow was made for shooting a couple of arrows a long way. If it beats the world record it did its job so the damage done while shooting is of little concern.
It is NOT the same as shooting no arrow, there is inertia, I can't be bothered to work out the physics.
The arrow may 'weigh' 75 grains, eg mass x gravitational acceleration, but the bow is accelerating it at more than 1g so it's effective 'weight' is much greater (It's mass of course remains the same)
Del
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Has anyone ever tried to dry-fire a bow to see what happens??? I've heard the bow will be damaged , but I dont know of anyone , or even heard of anyone who tried it!! perhaps a bow can take it? maybe it's a myth-call the myth busters, I'm too attatched to my bows to try
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I'm not sure of the relevance of this dryfire concept, if you should never dryfire a bow????
Whomever said you should never dryfire a bow is talking about hunting bows. These are flight bows and it is entirely different. They might shoot a 75 grain 20" arrow, which is the same as shooting no arrow. The difference is that the bow was made for shooting a couple of arrows a long way. If it beats the world record it did its job so the damage done while shooting is of little concern.
It is NOT the same as shooting no arrow, there is inertia, I can't be bothered to work out the physics.
The arrow may 'weigh' 75 grains, eg mass x gravitational acceleration, but the bow is accelerating it at more than 1g so it's effective 'weight' is much greater (It's mass of course remains the same)
Del
Now your just getting petty. ::) A heavy string or double serving would make that difference.
When a bow is considered dry fired at as low as 7 grains per pound and at risk of breakage, and you are shooting 1 grain per pound, for the bows sake, you might as well shoot no arrow. If I stuck a 1 grain BB on it would have mass and not be dry fired by your definition, but it would not help the bow.
Dragonman, yes I have seen several bows dry fired. Some have broken, but most have not. I have seen the string pop off a couple that were dry fired and split the tips out.
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I'm willing to bet most selfbows wouldn't have much trouble from a dry fire but maybe some laminated ones might come apart. Not sure. I have an older 60# boo ipe I could try it on for fun :) On video of course ;D Anyone dare me ;D Thinking it might be fun. Maybe dangerous though?
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I'm with Del the cat. His meow makes sense to me.
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I'm not sure of the relevance of this dryfire concept, if you should never dryfire a bow????
Whomever said you should never dryfire a bow is talking about hunting bows. These are flight bows and it is entirely different. They might shoot a 75 grain 20" arrow, which is the same as shooting no arrow. The difference is that the bow was made for shooting a couple of arrows a long way. If it beats the world record it did its job so the damage done while shooting is of little concern.
It is NOT the same as shooting no arrow, there is inertia, I can't be bothered to work out the physics.
The arrow may 'weigh' 75 grains, eg mass x gravitational acceleration, but the bow is accelerating it at more than 1g so it's effective 'weight' is much greater (It's mass of course remains the same)
Del
Now your just getting petty. ::) A heavy string or double serving would make that difference.
When a bow is considered dry fired at as low as 7 grains per pound and at risk of breakage, and you are shooting 1 grain per pound, for the bows sake, you might as well shoot no arrow. If I stuck a 1 grain BB on it would have mass and not be dry fired by your definition, but it would not help the bow.
Dragonman, yes I have seen several bows dry fired. Some have broken, but most have not. I have seen the string pop off a couple that were dry fired and split the tips out.
Sorry, I just don't understand the accusation of pettiness. As Scotty would say 'Ya cannae change the laws of physics'. You can push a small car or a motorbike by leaning on it, just try accelerating fast by giving it a sharp shove.
Come to think of it...don't bother, just believe what you like. >:(
Del
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Out of interest I just found this table on the web having googled 'arrow acceleration'
It refers to two different bow types (one being a longbow)
Acceleration Force on arrow
average max average max
(G) (G) (lbf) (N) (lbf) (N)
200 378 6.4 (28) 12.0 (53)
145 340 7.5 (34) 17.7 7.9
I think an acceleration of 200G is significant :o.
The assertion that a 75g arrow is the same as a dry fire is self evidently nonsense.
There is plenty of energy imparted into the arrow which would otherwise go into the bow and string.
Del
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I didn't mean to start an argument :(
I was just looking for attributes that make good flightbows. Take those characterisitcs, add them (as best as I can) to hunting bows that are shooting about 7 gpp arrows, since they would need different attributes than a bow shooting a 10 gpp arrow.
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I was thinking the same that self bows could probably take it!!
Jesse-S, if you do. it is a good idea to wear some goggles and maybe a helmet!!, it would be interesting but a shame to sacrifice you're bow. The damage may not be immediately apparent either
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I was thinking the same that self bows could probably take it!!
Jesse-S, if you do. it is a good idea to wear some goggles and maybe a helmet!!, it would be interesting but a shame to sacrifice you're bow. The damage may not be immediately apparent either
I was thinking of a bow I dont like anyway and yeah I would wear some protection just in case ;) If I did it I would most likely do it many times to see if I could get it to break ;D
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Kegan
Have you read the chapter by Dan Perry in tbb4. He talks o lot about dry fire speed. I like the concept of the dry fire speed.
You could for example get high dry fire by having a long stiff handle, making the tiller more whipped. Like that Hazelbow by Stellapasfänger in BOM October.
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I'm not trying to be arguementative, but I still dont appreciate this concept! (maybe I dont understand it) but bows need to shoot well with an arrow not without, and you can not test the theory without endangering the bow!! I guess I'll go back and read up. I must be missing something
Jesse; interesting experiment ,if you document and post the results, (I'd be interested anyway)
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Kegan - While I know absolutely nothing about flight shooting or dry fire speed I feel like the same principles of making a bow fast apply to all bows but the reason flight bows are fast is because they are pushed to the absolute limit of the materials for best possible speed. I was talking to Tim Baker about making a holmegaard style bow for optimal speed and the bottom line is make the outer limbs stiff and light with the inner limbs wide enough to take minimal set. Also heat treating is magic stuff.
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I have been thinking about this topic and I can see that what we have here is a misscommunication. Del, you are absolutely right about kE. The arrow has some on impact at the target. What Kegan is refering to is speed of the string. At a certain point the arrow becomes so light it has negligable effect on the speed of the string because the wood can only recover so fast no matter what. It is similar to throwing a bowling ball or throwing a BB. The bowling ball will slow your arm considerably. The BB will cause no percevable change. The BB still has mass and will have kE, but your empty hand cannot travel any faster than the one with the BB because you have reached the reaction speed of your muscle.
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Thank you Justin :)!
TBod- yes, but I'm currently re-reading it. See, here I thought whip tillers were for heavy arrow bows ???. I need to do some more reading...
Dragonman- I'm not going to ACTUALLY dry fire one of my bows. I'd just like to increase their light-arrow performance.
Ryoon- Considering I'm not going to be using true flight arrows, you very well might be right. I'm working on several stiff, light tipped bows at the moment. Maybe jsut a little tweaking is all I'll need for them. Still, it's good to know just in case :).
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The term "Dry-Fire" speed is a bit confusing but in flight shooting, high "Dry-Fire" speed simply means that the bow remains very efficient even with very light arrows. I believe that Dan Perry coined the term.
I have shot bows that could not get out of their own way even with if there were no arrow mass on the string at all. The drop off in efficiency with lighter arrows is very abrupt and the hand shock unbearable. A 3-4 ggp arrow in this bow would be little different than a dry fire.
On the other end of the spectrum, I have shot an unconventional bow design (modern materials), where I accidentally dry fired it. The string sounded like it cracked the sound barrier and sheared through a 1/8" steel protective plate before destroying itself. This is insanely high dry-fire speed. A 3-4 ggp arrow in this bow feels like the equivalent of lobbing a heavy brick compared to a true dry fire. Although this would be a very FAST brick! Even a 2ggp arrow slows down the string considerably with this kind of bow.
It is a lot of fun to see how changes in design an construction affects performance with very light arrows. It certainly helps keep bow building from becoming dull for me. There may only be a few fps difference between bows with heavy hunting arrows (10 ggp +/-), but the performance difference is magnified with light arrows. A great side benefit is that you will find that your target and hunting bows will improve based on what you learn from your flight shooting bows.
With regards to durability, a well made primitive flight bow can last a long time and I have seen many examples that continue to set records years after they were built. Dan Perry is a good one to ask about that.
There are a couple of design approaches to take to get a high "dry fire" speed. The first is to design a bow that focuses the bending area over as small a portion of the limb as possible. The inner/handle and outer portions of the limb should be stiff as possible. This forces all of the limb kinetic energy back through the string and into the arrow before it leaves the bow.
The other approach is to play around with "gear ratios". What is meant by this is that the design allows a long draw but the heavier limb moves as little as possible so there is little energy lost to accelerating the limbs in the first place. A compound wheel bow does this and there are some other unconventional designs that do this.
Regardless of the design approach, it is always good to keep the limb mass to a minimum and you use the lightest and stiffest string material you can find.
If you are interested in flight shooting and setting records, the US Flight Shooting nationals are held at the Bonneville Salt Flats toward the end of August. There are several Primitive classes as well as modern classes. It is a blast to be able to shoot far as you can without having to worry about losing your arrow. :)
-Alan
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See the whip ended state,ment making a fast bow confuses me. I believe that in one of the tbb the world record holding bow had very long outer limbs that worked like long levers with a very very small working portion of the limb right out side of the handle ???. I might be mistaken, i made the mistake of loaning my tbb's to a newby bowyer and havent seen them since lol :(
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Lots of things make a bow faster but less durable. Whip tiller is one of them. I believe underbuilding is a fairly common practice in flight bows. At least underbuilding what we would in a target or hunting bow.
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Hey, Kegan... I understand your fascination with speed... it's fun. But, when it comes to hunting bows (which I think you're talking about), I much prefer momentum = penetration. Heavy arrows are more efficient than light arrows. With a heavy arrow, more of the energy in the bow's limbs are tranfered to the arrow, and less is lost with things like string vibration, limb vibration, etc. Light arrows fly like laser beams, but pack no punch when they arrive on target.
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As I understand it "limb timing" for want of a better term is also relevant. I know Marc know his stuff about speed and doesn't necessarily agree with my characterization of topic. The idea is that if bow limbs return along the same path the took during the draw, and in addition with as little variation as possible in the string angle along the path, upper compared to lower, the bow is more effiicient. Essentially if the nock doesn't travel much during the power stroke, it's better.
Improved efficiency (techniques) applies all bows, not just "flight bows." Like the movie "an elk don't know how many feet a horse have..."
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ADB- I'm not talking about using 300 gr arrows. For the weight I like to shoot, a 500-600 gr arrow is "light". I've built bows in the past however, that even though these same arows were spined properly, they made the bow kick like a mule and were no faster. I'm trying to build my way around that problem :)
Thanks all. I think I have enough to try a few test bows. Wish me luck :)
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I like your approach Kegan. Getting a better understanding of optimum speed with a 75 grain, or 500 grain arrow will help us to build a more efficient bow that shoots 900 grain arrows. I like efficiency.
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Thanks Justin! My train of thought was "If I take what makes a 3 gpp bow shoot well and apply it conservatively to a 7 gpp bow, I should see increased performance."
Likewise, reading through the flight shooting chapter of TBB vol. 4 I picked up some good tips for normal hunting bows too :)