arrow weight tolerances - in practice

[pHz]

i know in theory you should try to build your arrows to the tightest weight tolerances you can (its been suggested to me that within 2-3 grains is good enough for all but the very best archers)

but

if youre anal enough (like me sadly) to check the weight of your arrows - what is the actual REAL WORLD weight range in your current dozen (or whatever) ?

and - what practical effect (if any) do you think that has on your performance / scores ? - how would you prove this ?

anyone able to offer the physics of what a (for example - i AM building new arrows right now but have no idea yet of the tolerance im working to) 6 grain difference from lightest to heaviest might mean in terms of vertical spread at 80 yards / 70 metres ?

slainte : rob

[joetapley]

Brief summary
Carbon Tech Arrows - Dealers Page

[pHz]

some interesting bits in there

thanks joe !

slainte : rob

[moo-mop]

You can't see any difference in scores at my level. However, I modelled it using a few rough and ready things I knew about arrows that were 10 grains different in weight, when you can actually start to see it.

The model showed on average about 2 points, and at most 5 points, were lost on a distribution of arrow spread that gave a 630 level FITA 70m. My conditions were quite bad: 6 arrows that had two sets of three arrows one was 2-3 grains different to the the other three and the groups set in the middle for best score.

In my model you lost less points if you were worse and more if you were better, but never enough to be able to see the difference if you were shooting real numbers of arrows with more real variations (ie not over large averages that can be done on a computer).

[Desert Archer]

Someone posted an article by Rick McKinney on one of the archery boards (can't remember which one right now) that detailed the importance of uniform SPINE. McKinney claimed that was the critical factor and absolute straightness or perfectly matched weight didn't come close in importance.

Since I respect McKinney's past performance and current opinions (along with some other noted archers) I've quit worrying about exact weight within reason, which to me is the 2-3 grains you mentioned.

Dave

[tel]

I think thats the one reproduced on the page Joe linked to above.

[moo-mop]

Originally Posted by Desert Archer

McKinney claimed that was the critical factor and absolute straightness or perfectly matched weight didn't come close in importance.

Beware of marketing - his own brand of arrows are high in spine tolerance, so of course he stresses how critical it is. Other manufacturers claim differently. We really need more independent data, even though he is a highly respected archer, my feeling is at the moment this claim can't be justified, as of course is the case with much of what we hear on equipment.

[Desert Archer]

Originally Posted by moo-mop

Beware of marketing - his own brand of arrows are high in spine tolerance, so of course he stresses how critical it is. Other manufacturers claim differently. We really need more independent data, even though he is a highly respected archer, my feeling is at the moment this claim can't be justified, as of course is the case with much of what we hear on equipment.

I have to disagree with your cynical view of McKinney. He has a long standing reputation of being both honorable and interested in the good of archery as a sport. I know of at least one other Olympian who makes the same claim (that spine is more important than exact weight or straightness).

Also, Easton is known for having very uniform spine ratings and their X10 is the arrow of choice among the very best shooters in the world (their ACE was before the X10 was introduced). If spine doesn't matter as much as McKinney claims, why do you suppose the very uniform (in spine) X10 is THE arrow of choice?

Dave

[moo-mop]

I am a physicist (a PhD, like many hobby archers) I am trained to believe in data. If they want me to believe what is important then those involved should publish the data in a peer-reviewed sports science journal. I never claimed spine isn't important, just that there is no evidence presented in that article to suggest it is more important than weight or straightness. When you publish evidence it's fine to have a potential conflict of interest, you can still be sincere, but you must declare it. [Edit: there's some data on weight and straightness in the article but its lighter on the data behind the spine thing].

I'm sure McKinney is sincere, I never suggested otherwise - but he is an archer not a scientist. Which is why manufactures employ engineers (eg Gtek) to help them out.

I know Olympians that have made claims on kit based on experience, but it very very hard to show real effects by experiment and very complicated to model, ask Joe above. I'm not a good archer, but I have done some experiments on spine and like weight suspect it is not as critical as you might think. Such consistency in both is probably more critical as you get toward being truly good like the McKinneys of this world.

[archery_mum]

James Park suggests 0.5grains in one of his books. The closest I can get allowing for glue etc is 1 grain.