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Discussion Starter · #1 · (Edited)
I do not want to stir another pot like the 17+ page "circus" that got started over on AT recently by Turbonockguy making some misguided and immediately repudiated speed claims for Black Swan bows. I know it wasn't the first dubious claims and there are some legitimately dissatisfied cutomers here. However, I was a bit stunned that in TBM's interview this month Arvid himself apparently claims that his bows have recently been tested at 300 fps IBO. It's been awhile since my wheelie days and my mind isn't the "steel trap" that it used to be, but if memory serves that's 70#, 5 gpp (350gr.), and 30" draw. Not that I'd ever want to basically dry fire a bow, but is that claim as outrageous as it looks at first glance? I didn't think that compounds had achieved that until fairly recently. There seem to be some legit "technoweenie" types over here, maybe some cooler heads could weigh in please? I may have to rethink my subscription if that's as bogus as it sounds.
 

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Snake oil, bovine droppings, and other dubious terms apply to this "claim"
 

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And that is why independent testing and reporting like Blacky's is so important to this sport. Anybody can make claims and they soon become fact via the internet. Watch this one. In a month Black Swan will be the 300 fps bow on most forums.

Very sad!

Mike
 

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Well, there's production bows and "fast" bows. I don't mean that productions bows can't be fast. But there have been bows that have been built not to sell and expected to survive a limited number of shots.

Ever hear of Walk the Talk or Talk the Walk? It was a Pirates of Archery invite or at least was "sponsored" buy that site. It was a bowyer contest, to build the fastest bow. I was never there, but "heard" that bows approached that speed. As I recall those bows didn't last more than a few shots.

As I recall a couple of productions bows won it. ACS and Whippenstik come to mind. This all occurred more than 5 years ago and I have trouble remembering yesterday.

I also believe that feet per second is a little like climbing a mountain - you've gotta get back down. Take that out of the equation and maybe 300 is possible.

Better have a 6 pack handy after that.

Bowmania
 

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You need 2 things for speed.
one is light mass and the second is stored energy.
you need both.
it simply wont break records without a combination of both.

So you will need a limb mass of about 140grams.
you also need a stored energy of about 1.1 for the 200fps at 10gpp Mark.
to get 260fps we estimate you would need a stored energy level in the range of 1.5se/pdf.
thats a thumb suck calculation.
or you would need a limb mass in the 10-20 gram mark.
our computer bow model starts to fall appart with funny answers at this end of extreme values.

hope that helps put some of this in perspective.
 

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I am guessing most any bow shooting a 9gpp arrow with 190 fps or 200 @28" would do 300 at IBO standard. But why bother and try it out? This standard is way off for single string bows.
 

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You are missing the point, this is yet another claim, along with inventing the ilf system, dubious world records, and other stuff that continiously comes from this particular source.
 

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From the calculation projections from our program it would take about 225 fps at 9 gpp @ 28 to get anywhere close to the 300 fps. Even that projects the efficiency staying at the same level and we know that won't happen with that light an arrow.

The fastest bows on the market are 20+ fps slower that this number.

Mike
 

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And that is why independent testing and reporting like Blacky's is so important to this sport. Anybody can make claims and they soon become fact via the internet. Watch this one. In a month Black Swan will be the 300 fps bow on most forums.

Very sad!

Mike
Happens way too often Mike. If the claims aren't verified independently, they mean squat diddly.

Sent from my iPhone using Tapatalk
 

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I ran the calculations a couple of ways. I have gone through this enough times that I added a linear draw force curve bow to my bow program. So using the following specs:

Draw=30 inches
Brace height = 9 inches
Distance from rest to back of bow = 1.75 inches
Weight at 30 inches = 70 pounds
Arrow mass = 350 gr
Speed = 300 fps

You would need an efficiency of 125%

Of course our bows store energy better than that. That is Sid's point. This linear DFC bow is only storing 0.8 ft-lbs/lb. A decent bow should store about 1.0. So just doing a quick scaling of the potential energy so that we get 1.0, you would get an efficiency of

Efficiency of 100%.

If we scaled for a ground breaking value of 1.2 for SE/PDF you get an efficiency of

83%

This is a number that you can hit with a shooting machine. So using these simple calculations (as opposed to Sid's more robust model), it is possible, but would be revolutionary. So now they need to show us. We need to see a record breaking SE/PDF and an extremely high efficiency.
 

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If the claims aren't verified independently, they mean squat diddly.
This is very interesting in that there appears to be universal suspicion of this particular bowyer. Yet there are other bowyers who also make unsubstantiated claims about special materials and performance yet it is very difficult to question anything they do here. Yes, the answer is testing. The other one is insisting all claims are verified no matter who the bowyer is. Or to put it another way we shouldn't question those who question unsubstantiated claims.
 

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MAT,

The key is that you need to validate that the claims are within the boundaries dictated by physics. A good experimentalist will perform a reasonableness check to ensure that they are measuring what they think they are, and that their process is working correctly. I did this in the previous post and could not say it cannot be done, but established some boundaries on the bow in order to make it happen. There have been claims in the past that flat out won't work. So now we need to see. The claim is not out of the question using a linear DFC approximation adjusting for SE/PDF. This is pretty crude but a least it takes us to the next step, which is: "show me more".
 
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for a 350 grain arrow to be launched at 300 fps. requires an applied KE of 70 foot pounds.

Assuming an efficiency of 85% on the bow, the bow would have to store 83 foot pounds of energy..

Would dearly love to see the draw/force graph for this bow..
 

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That's my point, Webster. I would like to see it as well. To me the limiting cases are a linear DFC and a square wave for minimum and maximum energy storage. A linear DFC is like a D shaped longbow, and a square wave is the most efficient compound. The square wave stores twice the energy. The DFC has to be somewhere in between. It will have to have a pretty big bump in the middle.
 

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Not to hijack, but I like thinking of all this in terms of

http://en.wikipedia.org/wiki/Hooke's_law

(scroll down for a draw force curve of sorts)

and how compound and single-string bow makers attempt to get around it (in a sense, not implying fraud but deviating positively from the behavior of an ideal spring) given the limitations of their particular type of bow.
 

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Hooke's law is an approximation that applies to small deflections. The range over which Hooke' law applies depends on material and geometry. When a limb stacks, it is going non linear.
 

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Dan, there was no smiley on your comment so I am not sure whether it was in jest (by the way, I never use emoticons. I let folks guess whether I am being serious).

In response, you would need to calculate potential energy correctly for the whole system so that the measured efficiency was below 100%, so you are not violating the first law of thermodynamics. Race cars are complicated systems. Doing the energy measurements and calculations correctly would also be very complicated. The real art to energy calculations is how you define your system, what is in, and what is out, and making sure your system is complete. This was actually the core of my PhD thesis, but I applied the principle to enzyme catalyzed reactions in the body. Enzymes, bows and cars still follow the same fundamental laws.
 
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