Shooters with similar bows and wildly different arrow specs?

[FrankM]

I've been reading a lot of threads lately. Seems like some guys with say, #50 bows, like the same spined arrows with completely different point weights. One guy likes 30.5" 3355's with 250 gr. and another likes 29" 3355's with 125 gr. Yet they both tune. I see values all over the place, even when they have the same bows!

Is it really ultimately up to the individual shooting style and not calculators, formulas, etc? Or do you think these shooters may be compensating for problems in their individual form, etc? I don't want to start a troll thread. I'm just perplexed on this issue.

[nineworlds9]

There's a variety of reasons for this phenomenon:

-bows cut to center or past center are easier to tune on a variety of spines
-string strand count and material choice differences among archers will affect tuning
-creep at anchor by some archers (it happens!) causes that '28" draw' to really be a 27 3/4" or 27.5" or 27" etc.  LOL.  It happens, just sayin.  

-individual form, cleanliness of release will affect the efficiency of the bow and bow much energy goes into the arrow.

[FrankM]

Y'know, I'm inclined to call Stu's and the other calculators "mechanical zero" as in rifles.

[dragonheart]

There are differences in form.  The dynamic spine of arrow has multiple variables you can plug into a calculator.  That will get you real close.  We are still releasing the bowstring the way "we" do it.  There are differences and each has to compensate for their individuality in form.

[FrankM]

Sometimes I wonder if they only tune because the arrows compensate for torqueing a string, etc.
and the archer doesn't know it.

Of course, the other way of thinking is, if the arrows tune, who cares what the calcs say?

[ishoot4thrills]

Differences in draw length make a lot of difference in arrow spine too.

[overbo]

Some bows just shoot harder than others at the same draw weight. I have a 63lbs @28'' that bareshaft a 2219 w/ a 100gr point. Another the exact draw weight bareshaft a 2216 w/ 160gr point. Both 3/16 pass center, both arrows the same length, and both ff strings.

[Wheels2]

Originally posted by FrankM:
Y'know, I'm inclined to call Stu's and the other calculators "mechanical zero" as in rifles.

Miller (and the 3Rivers formula) have the Personal Form adjustment but unfortunately until you shoot a bunch, you have no idea what that value might be.
I am lucky as I am able to do well with the formula as is.

[Bowwild]

I too have great success with Stu's without tweaking the form calculation.

Of course an obvious factor is people with perfect form have different draw lengths which results in different draw weights and of course different arrow requirements.

Some folks different methods of tuning and accept various results. Frankly, I would have no faith in another person's recommended set-up for me. I almost never comment on threads asking for advice on tuning because of these and other factors.

[nineworlds9]

Indeed some bows just shoot harder.  Dynamic efficiency plays a big role.  Take a Centaur, a Bigfoot, a Stewart, or a Cari-bow or some other tops design and shoot it next to a run of the mill bow of the same draw weight and see what happens  :D

I like the analogy of the 'mechanical zero' far as Stu Miller is concerned.  It usually gets me close, but I also find I can do a bit softer spine and get great results with my personal form.  Generally if I go stiffer I start to see less than ideal results.

[ScouterMike]

I hesitate also to participate in "tuning" threads because usually the problem is the numbers and nobody likes to be proved wrong. The calculators work well if fed good data. If not, garbage in means garbage out. The reality is few seem to actually measure their draw weight at their draw length etc. so the charts, calculators all seem wrong. Also when similar bows seem to require radically different setups then I would guess that answer is in the actual numbers not the made up/assumed numbers used.

I built a calculator for arrow trajectory and determining approximate velocity of different arrow weights if one is known. It of course requires good data. I get alot of that does not work for me feedback. I even had a bowyer comment that the velocity difference between arrow weights was much less with his bows. If that was true then his bows lose large amounts of energy with small changes in arrow weight indicating something terribly wrong in design. I believe his bows are fine but his numbers are wrong.

[old_goat2]

The second post couldn't have summed it up much better!


 

Originally posted by nineworlds9:
There's a variety of reasons for this phenomenon:

-bows cut to center or past center are easier to tune on a variety of spines
-string strand count and material choice differences among archers will affect tuning
-creep at anchor by some archers (it happens!) causes that '28" draw' to really be a 27 3/4" or 27.5" or 27" etc.  LOL.  It happens, just sayin.  

-individual form, cleanliness of release will affect the efficiency of the bow and bow much energy goes into the arrow.

[old_goat2]

One other thing. The spine calculators work fantastic if you have a known good flying arrow for a particular bow to get a spine value for then virtually build another arrow in the software and get it's spine readout to be the same as the known good arrow.  And like any other computer program, if you put garbage in you get garbage out! Put good accurate information in you usually get good accurate information out. Why it's important to have all the toys, IE: grain scale, chronograph etc...

[Dale in Pa]

All of the above is true,but one factor no one touched on is---is the arrow really tuned well and flying straight?

Feathers cover up a lot of out of tune bow arrow combinations.

Can't count the number of times I watched or shot with people that had horrible arrow flight and never even knew it.

[blakeschack5466]

I can go into the stu miller calculator and easily create multiple arrows that are very different but still work according to the calculator.  For example: according to the calculator GT trads 3555 cut to 30" with a 12g insert and a 100g point has a dynamic spine of 62.1.  GT trads 7595 cut to 30.25" with a 50g insert and 225g points has a dynamic spine of 61.7.  According to the calculator these arrows can be shot from the same bow. There is more than one way to skin a cat. In fact there are dozens.

[FrankM]

Originally posted by nineworlds9:
Indeed some bows just shoot harder.  Dynamic efficiency plays a big role.  Take a Centaur, a Bigfoot, a Stewart, or a Cari-bow or some other tops design and shoot it next to a run of the mill bow of the same draw weight and see what happens   :D  

That's a good point.

For some it is more manly to want to claim that their bow needs more spine, I have seen far more claim that they need more spine than those that find that they need less spine.  The result with a bow like a Hill style that person may get an arrow that flies when the longest possible draw with a perfect release is made, but with an off position shot the release may be softer and the draw length shorter, which will result in a non functioning stiff spined arrow that skids hard against the bow, which in turn delivers a slower loggy flying arrow.  A person that is honest about his form, may find the Stu Miller numbers more accurate, unless the data in the program has already been tainted by overly prejudiced input, which I suspect to be the case with some popular bow models.

[damascusdave]

Stu Miller recognizes that personal form factors can also come into play and he allows for this with his Personal Form Calculator value allowing for up to 15 pounds of spine modification according to the past experience of the archer...I have certainly found string composition to play a huge factor in spine required...I recently tried a ten strand Whisper string on a bow that had a 16 strand Dacron string on it...whereas that bow previously tuned nicely for me with 340 spine arrows (61 pounds measured draw weight at my 30 inch draw) it now shows weak with 300 spine arrows and 200 grains of point weight...rather than try to tune an arrow to that bow and string combination I am trying to come up with a string that will work nicely with the 300 spine arrows and 200 grain points that I want to shoot

DDave

[Orion]

In addition to the factors already mentioned that affect tune, there's also the fact that most bows will shoot a range of arrows quite well.  Though there probably is one theoretical best combination for every bow, most of us don't have good enough form to find it.  Luckily, that's not really a problem, because most bows will accommodate a range of arrow spines and weights and will give perfectly good arrow flight with a modicum of fletching.

[NBK]

I agree with all that has been said prior but would like to offer one more, albeit obvious, addition in the type and amount of silencers on the string.
Just got done shooting a new to me bow and without particular arrow grabbed an assortment of bare shafts just to get started.  I initially placed four string leeches on the string, weighing 20 gr each.   Three different spine weights, all with same point weight.  The stiffest spine bare shafted just stiff, the weakest, noticeably weak.
I then replaced the leeches with two yarn puffs, each weighing 38-40 gr.   Weak shafts now showed perfect flight, and the other stiffer shafts were WAY stiff!  Same weight in silencers, but obviously more "drag" on the string.  Same bow, same arrows, same silencer weight, just different types put my tuning on its ear.