Rule of thumb for point weight selection

Whitehart

Well-known member
Archers sure like to make it complicated and read a lot into it. Maybe a bit of listening to the Easton Target Archery podcasts are in order where GT will quote FOC as F*(*king Over Complicated.
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Nobody has done either of these, except for Clarence.
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So if I made a nock the same weight as my point and a point the same weight as my nock (this is one for Geoff :)) all I would be doing is moving the FOC % to the back of the arrow and I would see no difference in arrow flight - correct?
 

KidCurry

Well-known member
AIUK Saviour
Recurve indoors I shoot the same setup as outdoors. Outdoors I shoot the lightest point that gives the best group at the longest distance. Bottom line you have to reach your longest distance first. If you can't do that the game is over. Arrow speed vs arrow weight...... hummmm :)
 

geoffretired

Supporter
Supporter
If you made a nock the same weight as your point, you would be adding weight to the back, compared to the normal set up. That would make the COG further back than on the normal arrow. You would have no margin of safety. And the arrow would weigh more, and fly differently.
If, on the other hand, you made a point the same weight as your nock, that would make the front much lighter than before, and move the COG back again. Less margin of safety, and a lighter arrow, and a different arrow flight.
 

malbro

Instinctive Archer
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If you made a nock the same weight as your point, you would be adding weight to the back, compared to the normal set up. That would make the COG further back than on the normal arrow. You would have no margin of safety. And the arrow would weigh more, and fly differently.
If, on the other hand, you made a point the same weight as your nock, that would make the front much lighter than before, and move the COG back again. Less margin of safety, and a lighter arrow, and a different arrow flight.
As I understand it the reason to have a Centre of Gravity that is Front Of Centre is to prevent the back end of the arrow from flipping down during flight as the arrow loses forward momentum, by keeping the CoG with a positive FOC the arrow tends towards a straight flight dropping at the front first. With a high FOC (> 15%)then the arrow will lose height more quickly so to get long range you need to aim higher, the heavier weight of the arrow helps to get the distance has it carries more momentum thus can travel further as it has more energy to counteract the drag forces. Lighter arrows will start with a higher velocity but will not absorb as much energy from the bow so there is less energy to counteract the drag, its a trade off that will depend on both the arrow and the bow in use.

Also bear in mind that many bows have a limit on how light the arrow should be, for example with my bow the lower recommended weight by the manufacturer is around 300 grains, less than that and the arrow cannot absorb enough of the energy from the bow so there is the danger of damage to the bow in the same way as a dry fire.
 

geoffretired

Supporter
Supporter
i think we are seeing different aspects to write about here. Malbro. with the two arrows described by Whitehart, they are both neither front or back heavy, the one with a nock as heavy as the pile(normal pile.) being same cog as the one with a plie the weight of a normal nock.The latter will be lighter and fly differently as the speed of launch will be faster making the arrow shoot weak.
 

KidCurry

Well-known member
AIUK Saviour
Clarence Hickman made arrows that could move internal weights and so independently change the FOC without changing weight.
Everything he did showed no difference in trajectory.
I'm not sure Hickman is relevant today. As he received the National Archery Association Thompson Medal of Honor in 1950 I assume his research was earlier. I would like to see his work repeated with the ultra light carbon arrow tech available today. Also a good reference to his reasearch would be good if being used to refute an argument. It makes checking the primary source much easier.
 

malbro

Instinctive Archer
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i think we are seeing different aspects to write about here. Malbro. with the two arrows described by Whitehart, they are both neither front or back heavy, the one with a nock as heavy as the pile(normal pile.) being same cog as the one with a plie the weight of a normal nock.The latter will be lighter and fly differently as the speed of launch will be faster making the arrow shoot weak.
Except for the weight of the feathers or vanes which would make the CoG slightly back from the Cog of a bare shaft i.e a negative albeit small FOC. As you point out the overall weight would be different so the arrows would have a different flight path.

None of this answers the original question of choosing a starting weight of the point which from my research seems to be in the range 60 to 100 grains for a target arrow, aiming for a FOC around 10 to 12%.
 

geoffretired

Supporter
Supporter
Perhaps, but it might give the OP a reason to consider whether or not to pursue the foc idea. Or put it better context.
 

Whitehart

Well-known member
Geoff I thought you would have been straight off to your shed and constructed the arrow and done a few test shots by now :)

Clearly moving the FOC % to this silly extreme will affect arrow flight. I agree knowing the FOC is not that important and I can see why Easton or any arrow manufacturer(some just copy others anyway) do not want to discuss it because they do not make an infinitely adjustable arrow with FOC in mind and feel that their own products based on their boffins conclusions and commercial interests are sufficient for us to take it as gospel - after all we are limited to adding/removing mass weight from off the shelf components to move this measurement.

What I said earlier - use the recommended point weight from the manufacturer and if you want play around from there go a head.
 

Andy!

Active member
I'm not sure Hickman is relevant today. As he received the National Archery Association Thompson Medal of Honor in 1950 I assume his research was earlier. I would like to see his work repeated with the ultra light carbon arrow tech available today. Also a good reference to his reasearch would be good if being used to refute an argument. It makes checking the primary source much easier.
Most of his work is detailed in here: Clarence N. Hickman: The Father of Scientific Archery - Schumm, Maryanne M. | 9780961358204 | Amazon.com.au | Books
 

geoffretired

Supporter
Supporter
Geoff I thought you would have been straight off to your shed and constructed the arrow and done a few test shots by now
Andrew, I would have done if........
If I had thought it was worth trying it out.
I like doing this sort of thing; but only when I might gain something or learn something that could be of value. There are aspects of archery that I have little interest in. I am interested in understanding why FOC is important or not, so I can inform others who might think they should get obsessed by it. I am not interested in testing it if it has already been done,heehee
 

Whitehart

Well-known member
Andrew, I would have done if........
If I had thought it was worth trying it out.
I like doing this sort of thing; but only when I might gain something or learn something that could be of value. There are aspects of archery that I have little interest in. I am interested in understanding why FOC is important or not, so I can inform others who might think they should get obsessed by it. I am not interested in testing it if it has already been done,heehee
Yes this was a bit obvious and deliberately so, having been told that changing the FOC but not the mass weight of the arrow does not affect the flight or trajectory. You have to know these things :)
 

KidCurry

Well-known member
AIUK Saviour
Thanks Andy. Yeh... found that but I don't want to buy it. If you have the page reference I can probably get my uni to get hold of the relevant pages.

Yes this was a bit obvious and deliberately so, having been told that changing the FOC but not the mass weight of the arrow does not affect the flight or trajectory. You have to know these things :)
Trajectory no, that's just classical mechanics. Flight, especially on windy days, I'm not so sure.
 

AJBrady

Active member
I read something in The British Archer many years ago about someone experimenting with moving the fletches forward, a LONG way forward - about half way down the shaft. The arrow apparently flew more like a boomerang.
 

geoffretired

Supporter
Supporter
Heehee I was told that you have to put fletchings at both ends to get the boomerang effect. I am not going to test that. Throwing a boomerang!! Now that's a whole different story; love throwing boomerangs.
 

mbaker74

Supporter
Supporter
AIUK Saviour
I fully understand the effect of changing point weight on spine & tuning etc. but what I don't fully understand is where a good starting point (no pun intended) is for any particular setup. Is there a good rule of thumb that says for a given draw-weight, spine, shaft length, shaft weight, you should start with about NNNgrains and fine tune from there?

Does anyone have a rule of thumb/algorithm for this? I've seen some more extensive calculators for optimising overall arrow weight, of which the point weight is obviously a signficant component, but I'm not after anything that sophisticated.

Thanks in advance for any thoughts
The Easton target product guide gives the recommended point weights for every spine in every arrow range. I assume other arrow manufacturers do the same?
 
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