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jerryRTD

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I like your swing analogy :)
Del
I am not convinced according to my research a recurve is spitting out arrows at 225fps max The ibo speed for my compound bow is 335 fps That is 110fps extra that has to be gained. give that the poundage ramps up in about a inch the arrow has to gain that extra speed in about 28 inches.
but all that is not important there is another very good reasons why you should not use wooden arrows. most compounds actually do have a a small verticle paradox That means that if a arrow fails there is a a good chance of the arrow being driven into the arm.There is also a good chance that.wooden arrows are going to be damaged by the extra power of a compound.
 
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geoffretired

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Jerry. The first inch of travel for a compound arrow is being pushed by about 8 lb. the next inch by about 12lb the next by about 16lb..
The recurve in the first inch pushes the arrow with max holding weight, possibly 40lb. It's like hitting a nail with an 8lb hammer compared to 40lb.
It's a similar effect as being tackled in ruby by some one running at you at full speed when you are standing still. Compared to being tackled by someone who is running from behind you and you are running the same direction and just a bit slower. The impact on the players is far less.
Or put another way; you can throw an egg quite a distance; but you can't kick one very far.
 
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Bandit

Active member
Jerry. The first inch of travel for a compound arrow is being pushed by about 8 lb. the next inch by about 12lb the next by about 16lb..
The recurve in the first inch pushes the arrow with max holding weight, possibly 40lb. It's like hitting a nail with an 8lb hammer compared to 40lb.
It's a similar effect as being tackled in ruby by some one running at you at full speed when you are standing still. Compared to being tackled by someone who is running from behind you and you are running the same direction and just a bit slower. The impact on the players is far less.
Or put another way; you can throw an egg quite a distance; but you can't kick one very far.
That’s depends on the cam. I would say the first inch is dependant on let off then after that a huge acceleration of 60lb. No tickling going on. Check out the arrows supplied for these super compound cross bows you can buy now that shoot full length arrows. Stick a wooden arrow in one of those and you will have a bad day

You could maybe be safe shooting broom handles but again I ask what’s the point?
 
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geoffretired

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Yes, it does depend on the cam. I think we do need to put this issue in context.
Possibly, for the same launch speed; or the same maximum poundage.
 
D

Deleted member 7654

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I am not convinced according to my research a recurve is spitting out arrows at 225fps max The ibo speed for my compound bow is 335 fps That is 110fps extra that has to be gained. give that the poundage ramps up in about a inch the arrow has to gain that extra speed in about 28 inches.
but all that is not important there is another very good reasons why you should not use wooden arrows. most compounds actually do have a a small verticle paradox That means that if a arrow fails there is a a good chance of the arrow being driven into the arm.There is also a good chance that.wooden arrows are going to be damaged by the extra power of a compound.
If the facts won't convince you, nothing will. What do you think they were shooting out of the original compounds when they were first developed?
Del
 

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KidCurry

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I think I'm with jRTD here. You can't compare today's compounds with those 50yrs ago. Even my early compound used eccentric wheels. These were slow to get up to speed. Top performance compounds are now extremely quick, with the valley over a knife edge. And they transfer the energy very effectively. By the time my last compound was 1" on its way it way pretty much at peak weight. There's no way at 3" it was only at 16lbs since about 1990 :)Ask anyone who has dropped their concentration at full draw on a recent top bow and you are luck if the release aid doesn't get ripped from your fingers or your arm from it's shoulder.
But jRTD makes other really good points. I have had many carbon arrows fail when hitting a boss, mainly straw. These are strong arrows that are made with virtually, to no, flaws. I doubt you would be able to make a set of wooden arrows with no flaws. And even with no flaws they will not take the impact energy that carbons need to survive. Once or twice maybe, but they will fail. I've seen a longbow put a wood arrow through a hand, I can imagine what a compound would do. And I recon you will not get one retailer to say it is safe to shoot wood arrows from a compound.
 

geoffretired

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That is pretty convincing. I think I was guilty of repeating things I first stated 30 years ago and have repeated without updating the story to take the fast cams into account.
I have upgraded from windows NT to windows 10 in the last 20 seconds.
Cheers
 

KidCurry

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AIUK Saviour
If the facts won't convince you, nothing will. What do you think they were shooting out of the original compounds when they were first developed?
1596485138769.png
Del
Okay, apart from the losses from a finger release in the first inch of travel, which are ignored, there are issues way beyond taking abstract data from a graph to show a single point of view; I hate un referenced data :) I can show a dozen graphs that will, in isolation, show global warming is not happening. The point is is a wood arrow safe to shoot with a compound, not will a wood arrow survive the first one thou of a second at launch? A wood arrow is good at absorbing the initial arrow acceleration, I have no issue with that. Ignoring any impact issues, what I have an issue with is a wood shaft absorbing the increasing and sustained acceleration of the compound over the repeated longer period. A really well made wood shaft will last longer but it will fail way before a carbon or alu arrow.
I guess the real question should be how much sooner will it fail?
 
D

Deleted member 7654

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Okay, apart from the losses from a finger release in the first inch of travel, which are ignored, there are issues way beyond taking abstract data from a graph to show a single point of view; I hate un referenced data :) I can show a dozen graphs that will, in isolation, show global warming is not happening. The point is is a wood arrow safe to shoot with a compound, not will a wood arrow survive the first one thou of a second at launch? A wood arrow is good at absorbing the initial arrow acceleration, I have no issue with that. Ignoring any impact issues, what I have an issue with is a wood shaft absorbing the increasing and sustained acceleration of the compound over the repeated longer period. A really well made wood shaft will last longer but it will fail way before a carbon or alu arrow.
I guess the real question should be how much sooner will it fail?
I'll try and explain further...
Dealing with your points one at a time.
1. I can reference the graph:- https://sites.google.com/site/technicalarchery/technical-discussions-1/arrow
2. The peak acceleration from the conventional bow is in the first few milliseconds. From the compound bow it is after about 12milliseconds (see graph). With the "sustained acceleration" you talk about the force on the arrow will remain constant... it's a steady acceleration.
The peak force on the arrow is a maximum acceleration. In the graph in question the maximum acceleration is the same. It just happens much more suddenly with the conventional bow.

I think your answer simple reinforces my original assertion that many people don't actually understand the physics of a compound.
I will again ask the question! What do you think they shot from the original compounds?
Just out of interest, I've looked at recommended arrow spines for 28" carbon arrows on a 60-64# compound using a 100grain point spine of 400. I've converted that to the old fashioned way of measuring spine (note it result is adjusted for the fact that AMO uses a metric weight rather than 2 pounds).
What do you think the "old fashioned" spine is?
Do you think it is much stiffer than the poundage suggests?
What arrow "old fashioned" spine do you think would be needed to get the same deflection as the recommended carbon arrow?
Do you think a 3/8" diameter Ash warbow arrow would survive?

Let's just clarify something... the velocity of the arrow is just down to acceleration multiplied by the time for which that acceleration is applied.
So it is quite reasonable that a compound can have a lower maximum acceleration and still give a higher final velocity! (Yes I know it's counter-intuitive)
Here's a worked example to illustrate... it doesn't claim to be accurate, it's there to illustrate the counter-intuitive result.
E.G say the conventional bow has a fairly linear acceleration curve (starting high and going down to nothing) lets say that gives an average acceleration of 5,000 units for 0.02 of a second (the peak acceleration being 10,000 units) that gives velocity of 100 units.
Say the compound has a much more constant acceleration, (allow some time for it to ramp up linearly which we can add in)
peaking at say 8,000 units for 0.015 seconds plus a ramp up averaging 4,000 units for 0.005 second.
Note I've given them both the same overall duration. The compound velocity adds up to 120 plus the ramp up of 20 units.
That's a velocity of 140 units
Del
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...
Oh btw it comes out as 63# spine.
 
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geoffretired

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Supporter
I am confused!
The two graphs in the link show compound in red on one graph and blue on the other.
For close targets, the arrow released from the "slower" traditional bow will get there first, but in reality the arrow from the faster compound bow will pass the arrow from the traditional bow after only five feet of flight and 19 ms of flight time.
And I can't understand how a fast arrow can overtake a slower one?? How did the fast one get left behind if they set off together.
Recurve and longbow shooters bend their arrows at the start of the power stroke; surely that bending will eventually lead the the breakage. Compounds with release aids tend to be far less off axis witheir power stroke, compressing the shaft back to front, more tan bending it.
 
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D

Deleted member 7654

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I am confused!
The two graphs in the link show compound in red on one graph and blue on the other.
And I can't understand how a fast arrow can overtake a slower one?? How did the fast one get left behind if they set off together.
Recurve and longbow shooters bend their arrows at the start of the power stroke; surely that bending will eventually lead the the breakage. Compounds with release aids tend to be far less off axis witheir power stroke, compressing the shaft back to front, more tan bending it.
(maybe that's why I just showed the one important graph originally?)

Let me try to explain again.
If something accelerates at a modest rate for a long time it will end up travelling faster that something that accelerates at a greater rate but for a less time.
The conventional bow starts the power stroke at max acceleration, but the acceleration is dropping off all the time. The arrow is still gaining speed but at a lower rate.
The compound builds up acceleration and maintains its maximum rate for longer.
This shows up in the force draw (F/D) curve.
If you look at the force draw curve for a longbow it's a straight diagonal line.
The compound (or to a lesser extent a modern recurve) has a bulge in the F/D curve which shows the greater energy storage...
Ah! And that's were lots of people make the mistake!
They say " Ah! see the compound is putting more energy into the arrow it must be bending it more!!!"
NO .. It's putting more energy in in total but not putting any more in at any one instant... it's a longer steadier energy input than with the longbow.
E.G
If you divide the power stroke into say 4 sections for simplicity.
Longbow puts in say 4 units of energy in the first quarter of the stroke immediately after loose, 3 in the second quarter, 2 in the third and 1 in the fourth.... that adds up to 4+3+2+1 that's 10 ok?
The compound puts in say 3, then 4, then 4, then 3 that adds up to 14.
You see that, at any one part of the power stroke it's not putting in any more energy than the longbow did at it's max... but that totals 14.

That is the whole point of how and why a compound works... it's to overcome the longbow's limitation of poor energy storage... the let off is a bonus feature to allow longer hold, aim and a smoother release with less arrow flexing!
Does that help clear it up?
Del
 

KidCurry

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You obviously don't understand the graph the physics or what acceleration is.
Dealing with your points one at a time.
1. I can reference the graph:- https://sites.google.com/site/technicalarchery/technical-discussions-1/arrow
Thank you. Where is the soft start acceleration as the string is leaving the fingers? As with many theoretical models difficult bits to model are ignored
2. The peak acceleration from the conventional bow is in the first few milliseconds. From the compound bow it is after about 12milliseconds (see graph). [/QUOTE] Yes, but the graph ignores the soft start of the finger release. Why?... because it's hard to model.

What do you think they shot from the original compounds?
Doug Easton developed aluminium arrows 1939. Holless Wilbur Allen patented the compound bow in 1966, 27 years later. I'm going to go with aluminium on this one.

If you read my post I never said a wood arrow will not survive being shot from a compound. I said...
A wood arrow is good at absorbing the initial arrow acceleration, I have no issue with that. Ignoring any impact issues, what I have an issue with is a wood shaft absorbing the increasing and sustained acceleration of the compound over the repeated longer period. A really well made wood shaft will last longer but it will fail way before a carbon or alu arrow.
I guess the real question should be how much sooner will it fail?
This is why I hate it when people don't reference their sources. So, the draw force curve shows a 6" draw valley. That's an old stinger. I havent shot a compound with a 6" valley for years. As I said many new compounds have a valley about an inch long. The one referenced is a soft cam IMO.
Lastly, this is all good theorehtical modelling. Show me one perfect wood arrow and I would be happy to shoot it once. After that, not a chance. I would not consider it safe after that.
 
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D

Deleted member 7654

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@KidCurry Maybe read my previous post that responds to Geoff.
To response to your "soft loose" question, it represents a much shorter portion of the loose than the let off from a compound. (Note in the graph I posted. It starts at time=zero, and yes there is small gap before the first measurement, but it is very small compared to the significant portion of the graph and is dwarfed by the slower start of the compound)
Further.. yes I'm sure not all compounds are identical, but if it has some let off the general idea will be the same.
I notice you don't answer some of my questions.
So what do you think the recommended spine for your compound works out as in "old fashioned" spine?
It comes up very much in line with the "old fashion" poundage spine used for wooden arrows, and as the compound is virtually centre shot and generally using a release aid there is less sideways force on the arrow than with a longbow. So compounds don't have much stiffer arrows, as I've seen suggested elsewhere.
Are you really suggesting that a "ladies weight" compound is going to bend an arrow more than a gents 55# longbow?
Anyhow, there's no point be trying to enhance the understanding of someone who has no interest in it, so I won't be contributing further.
I think you have validated my original assertion about compound shooters not understanding!
Del
BTW. Most of the arrow injury pictures you see are carbon arrows stuck in people's hands.
 
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KidCurry

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@KidCurry Maybe read my previous post that responds to Geoff.
To response to your "soft loose" question, it represents a much shorter portion of the loose than the let off from a compound. (Note in the graph I posted. It starts at time=zero, and yes there is small gap before the first measurement, but it is very small compared to the significant portion of the graph and is dwarfed by the slower start of the compound)
Further.. yes I'm sure not all compounds are identical, but if it has some let off the general idea will be the same.
I notice you don't answer some of my questions.
So what do you think the recommended spine for your compound works out as in "old fashioned" spine?
It comes up very much in line with the "old fashion" poundage spine used for wooden arrows, and as the compound is virtually centre shot and generally using a release aid there is less sideways force on the arrow than with a longbow. So compounds don't have much stiffer arrows, as I've seen suggested elsewhere.
Are you really suggesting that a "ladies weight" compound is going to bend an arrow more than a gents 55# longbow?
Anyhow, there's no point be trying to enhance the understanding of someone who has no interest in it, so I won't be contributing further.
I think you have validated my original assertion about compound shooters not understanding!
Del
BTW. Most of the arrow injury pictures you see are carbon arrows stuck in people's hands.
 

KidCurry

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@KidCurry and as the compound is virtually centre shot and generally using a release aid there is less sideways force on the arrow than with a longbow. So compounds don't have much stiffer arrows, as I've seen suggested elsewhere.
I find it odd that lots of finger shooters always think compounds don't flex arrows because there is no flex left to right. It's the vertical flex on a compound that breaks arrows with an inherent weakness or damage.
(video from 7 seconds)
And I have never said compound need stiffer arrows. In fact compound shoot softer arrows pound for pound. Again, this is not the issue. The issue is compound operate at higher energy levels that the wooden arrow are not as well equipped to manage. Of course over engineering an arrow will negate many of the failings.
It's a shame you don't want to carry on this difference of opinion further, I do in fact think it's really interesting. I don't mind being insulted and I don't retaliate, ever.
 
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geoffretired

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Del, I do understand the accelerations you mentioned. It is how I have viewed things for some years now.
I think the formulae are getting me confused, because I can't carry their information into words I can make sense of.
I can see that with a really aggressive compound cam, the max acceleration of the shaft could be close to that of the recurve.
Arrow speeds being the same, I would put the compound as gentler on the arrow.
Peak weight being the same, I would expect many compounds to be gentler on the arrow, with the most aggressive cams possibly less gentle.
I still think the arrows break because of a combination of push and bend. The more the release causes a bend, the less acceleration needed to break the shaft. Just like nails bend when you hammer them in if you hit off centre.
 

geoffretired

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Supporter
I think it is about how each bow delivers its respective energy. There are two schools of thought; one says a compound is gentler on arrows than recurve/longbow. The others thinks otherwise.
I believe, from shoot compounds and recurves that they have a gentler launch than is expected. from the speeds they reach.
If we use extreme compounds they could be equally hard on the arrows. Context is important.
 
D

Deleted member 7654

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@KidCurry
Thanks for your nice post... I'll try and continue in the same spirit! :)
The vertical flex you illustrate is small compared with that exhibited by a longbow arrow.
IMO You are falling into the energy trap.
Imagine an arrow accelerated at rate you'd get from say a 20# bow but applied for say a minute !!! It would acquire a huge velocity and have had a huge amount of energy put into it, but it would be under no more stress than if it had been shot from the 20# bow. (I haven't worked out the numbers and it may be going supersonic and burning up by now... it's just an illustration!)
It's not about the final velocity... it's not about the energy. (excluding the impact with the target)
There are two main considerations... how quickly that energy is put in (e.g max acceleration) and any forces that will start to bend the arrow.
A 3/8" Ash shaft with a spine of about 80# is going to consider being launched from a compound as a gentle stroll in the park. As it impacts the target it may muse to itself "Ooooh, i'm going faster than I thought! Such fun"

TBF. I've looked up my reference to early compounds ("Billets to Bows" by Glen St Charles) and it doesn't actually specify the type of arrow being shot. In further reading about the history of the compound, I found this:-
Compound Bow – Facts and History of Modern Bows
One of the pertinent paragraphs says:-
"Arrows for compound bow have less “spine” (relative to the recurve bow) because compound bow will accelerate an arrow more gently and linearly"
Interestingly, it immediately contradicts that by saying:-
"Wooden arrows are not used because compound is too strong for them. It could break them and even hurt the archer".
Maybe, here we find the root of the problem/disagreement ???
I cannot reconcile those two quotes... they make no logical sense.
How can it be "too strong" and yet accelerate it "more gently" ????

Further reading on various forums produces lots of anecdotal stuff on both sides, many breakages but also people having "no problem"
I think the key is "an appropriate wooden arrow". So if you take an arrow suited to a 60# ELB it will likely be spined at 50# and may well be unsuitable for a 60# compound. However a 3/8" Ash shaft arrow spined at 70# would doubtless be fine... it's pretty obvious that no one is going to do the necessary testing to find the optimum spine for wooden arrows from a compound.
It is also likely that the impact could be the thing that would damage a wooden arrow and thus cause failure on the next shot.
I think the only logical sensible conclusion is :-
Yes you can shoot wooden arrows from a compound but it is a bad idea due to the potential failure probably cause by the high impact energy from prior shots.
Del
PS. I expect another major reason for not shooting woodies from a compound is that they wouldn't give the consistency required to score well.
 
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