What should we discuss next?

geoffretired

Supporter
Supporter
Del, I think the whole process is being masked by not knowing what bow weights and what let off and cam profiles we are considering, or not considering.
I don't think there is any doubt that a compound can be far gentler at getting arrows on the move from standstill to.......
It's at what point the heavier poundage kicks in and how rapidly that increases.
Did you see the quote I posted about the slow arrow getting to a short target first but getting overtaken by a faster one when shot at long ranges?
How does that work?How can a faster arrow get left behind at the start? It is faster from the start.
 

AndyW

Well-known member
I have never seen anyone shoot a wood arrow out of a compound and probably never will. I see no advantage in doing so. The discussion seems to more about how each bow delivers their respective energy.
It's been done.
I was following a group round at a comp three years ago when the compound guy ran out of carbons with about 1/4 of the course left. He was shooting a 50 - 60 Bowtech of some sort and his mate was shooting a border recurve. He just borrowed a few arrows and shot the rest of the course. I wouldn't do it myself but it worked that day.
I would be less concerned with the shooting of them than the shooting of them after they've been pounded into a few targets.
 
D

Deleted member 7654

Guest
Del, I think the whole process is being masked by not knowing what bow weights and what let off and cam profiles we are considering, or not considering.
I don't think there is any doubt that a compound can be far gentler at getting arrows on the move from standstill to.......
It's at what point the heavier poundage kicks in and how rapidly that increases.
Did you see the quote I posted about the slow arrow getting to a short target first but getting overtaken by a faster one when shot at long ranges?
How does that work?How can a faster arrow get left behind at the start? It is faster from the start.
I didn't see it. It sounds like nonsense... (If the arrows are identical)
I think the detail of cam profiles is irrelevant and is just masking the basic principle of how and why a compound works.
Del
 

Bandit

Active member
It's been done.
I was following a group round at a comp three years ago when the compound guy ran out of carbons with about 1/4 of the course left. He was shooting a 50 - 60 Bowtech of some sort and his mate was shooting a border recurve. He just borrowed a few arrows and shot the rest of the course. I wouldn't do it myself but it worked that day.
I would be less concerned with the shooting of them than the shooting of them after they've been pounded into a few targets.
for field archery I could see compound limited shooting wood arrows with nice round wheel cams. They would look the part for sure. Those round wheel bows were lovely to shoot. I don't see much application for long distance target archery though with wood arrows.
 

geoffretired

Supporter
Supporter
I think the detail of cam profiles is irrelevant and is just masking the basic principle of how and why a compound works
A compound could have round wheels, pivoted on centre. The cable modules could be round and pivoted on centre too. The draw force curve for that would be like a recurve, a sloping line almost straight.
By having the string wheels bigger than the cable wheels, mechanical advantage allows really strong limbs to feel like weaker ones. If they are round and pivoted on centre they have the same draw force curve shape as a recurve. A sloping line almost straight. The two could have the same holding weight, with the right wheels fitted to the right limbs.
Compounds like that would give the same kick at the start as a recurve.
Pivoting off centre allows a left off point to be established before the bow reaches its end of draw distance. Changing cam profile can do the same but with greater flexibilty to add a let off where they want it( late or early) and how much they want( lots or a little.)
From the arrow's point of view the let off amount and the length of that let off gives the slope on the graph, towards full draw. That, in turn, shows the rate at which the force on the arrow will increase, when the cycle is running in reverse.
These are details in the working principle, I agree. But they are the ones that change the profile of the power stroke from easy going to, be prepared for a shock.
 

jerryRTD

Well-known 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.
Eight pounds Geoff you must be having a laugh and 16 lbs for the second inch NO My holding weight on the back wall of the bow I am currently shooting is arouind 21 lbs an inch off the back wall and the poundage is around the mid fifties.
But that is only half the story the real action takes place at the other end when the arrow arrives at the target damage is much more likely to happen when the arrow hits the boss and stops that is when can become damaged and that is far more likely to happen if the arrow was shot off a compound bow. If a wooden arrow is damaged and is shot from a recurve, whereupon it fails then because the archers paradox is horizontal and the bow arm is below the arrow the archer will not be struck by the arrow. Harmless.
If the same arrow was shot from a compound bow then because there is a paradox in the vertical if the arrow breaks it will be driven into the archers arm.
 

geoffretired

Supporter
Supporter
My holding weight was 8lbs end of. If yours isn't 8 lbs, then that is a different bow obviously.
, whereupon it fails then because the archers paradox is horizontal and the bow arm is below the arrow the archer will not be struck by the arrow. Harmless.
When the arrow breaks the bits go in unpredictable places, depending on the grain of the wood.
However, we are getting into other issues here.
The thing that started this was the idea that a compound bow can give an arrow an easier launch than a recurve, Very little bending due to the release aid and the slower start than the 40 hit when at a standstill.
 

jerryRTD

Well-known member
@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.
It is not the damage that could be done by the bow it is the damage that is done by the boss. If I were to shoot those 60lb spined wooden arrows at a straw boss with an IBO 340 fps compound at a straw boss at 20 yds I think i would break arrows and maybe get a ride to A&E The compound is too strong for the woodies in the matter of impact energy.
 

jerryRTD

Well-known member
Del, I think the whole process is being masked by not knowing what bow weights and what let off and cam profiles we are considering, or not considering.
I don't think there is any doubt that a compound can be far gentler at getting arrows on the move from standstill to.......
It's at what point the heavier poundage kicks in and how rapidly that increases.
Did you see the quote I posted about the slow arrow getting to a short target first but getting overtaken by a faster one when shot at long ranges?
How does that work?How can a faster arrow get left behind at the start? It is faster from the start.
It does not unless the compound archer stops for a bite to eat. A fast compound will have beaten the recurve before the arrows have left bows around 300 fps for the compound around 200 fps for the recurve . That means the compound arrow about a 100 fps advantage There is no coming back from that.
 

geoffretired

Supporter
Supporter
Don't you agree that it seems odd that someone who has explained things in detail, then adds that a slow arrow will go a short distance faster than a quicker one?
 
D

Deleted member 7654

Guest
Don't you agree that it seems odd that someone who has explained things in detail, then adds that a slow arrow will go a short distance faster than a quicker one?
I've found the bit you refer to Geoff:-
He's referring to time measured from the instant of loose and it's a little bit silly.
The compound, (because it builds up to full speed slower) takes a longer time to leave the string. Thus the slow arrow gets a head start leaving the bow first but at a slower speed and therefore gets overtaken fairly quickly. (probably within a yard or so)
He just words it in a daft way... If he said the fast arrow overtakes the slower one soon after leaving the string, you probably wouldn't have batted an eyelid.
Putting it another way...
IF you synchronised the arrows from when they leave the bow (very had to do in practice) then, as common sense dictates, the fast arrow is always pulling away from the slow one.
But he times them from the instant of loose and the conventional bow gets the arrow away a fraction before the compound does.
Del
 

geoffretired

Supporter
Supporter
Del. Thanks for that.
Is that because the compound has another 3" of travel to go, due to the 6" brace height v 9" on the recurve?
I can't really get my head round that.
I can understand that from release, the recurve arrow starts faster. The compound starts slower. more gently as described several times in this thread. With slo mo I guess I could imagine the recurve taking an early lead from the point of release. Then I can imagine the compound catching up and overtaking the recurve arrow while both arrows still on their string.
 

Bandit

Active member
Del. Thanks for that.
Is that because the compound has another 3" of travel to go, due to the 6" brace height v 9" on the recurve?
I can't really get my head round that.
I can understand that from release, the recurve arrow starts faster. The compound starts slower. more gently as described several times in this thread. With slo mo I guess I could imagine the recurve taking an early lead from the point of release. Then I can imagine the compound catching up and overtaking the recurve arrow while both arrows still on their string.
My compound has a brace height of 8.5 inches not 6
 

geoffretired

Supporter
Supporter
Yes, I know they vary but I couldn't think of any other reason for the recurve arrow to be off the string before a compound.
I understand the principle that, at release, the recurve arrow starts to move very quickly and that the compound starts more slowly. I can see that the compound arrow will very soon start to speed up more than the recurve and start catching it up.
I am struggling with the idea that the recurve arrow leaves its string before the compound arrow leaves its string.
I understand that it is possible( maybe on an old round wheel compound) it just seems very unlikely with today's compounds that reach peak weight after a very short slower section.
 
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