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TAC 15/15i Basic Unpublished Information

 
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  #22  
Old 03-13-2011, 10:20 PM
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Re: TAC 15/15i Basic Unpublished Information

What makes you say that no matter what bow the arrow flexes horizontally? Isn't that a matter of which way the spine is oriented? Especially with a rail less design like the TAC.

And if using super short heads such as the Phat head, the idea is that there is not enough blade surface area to "catch" the air and start deflection. That is why they can say they fly just like field points. They don't, but they get much closer than conventional heads.

Getting back to the flexing. If you orient the spine to the same position, then each shot the arrow should behave much like the shaft before it. You can get each shaft to flex whichever way you orient the spine.
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  #23  
Old 03-13-2011, 10:31 PM
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Re: TAC 15/15i Basic Unpublished Information

Ultimately, the rear of the arrow is trying to accelerate before the energy is transferred to the front of the arrow. Assuming the cams on this device are pushing in the same fashion as a compound bow and the tiller of the limbs is equal and the nock is placed directly in the center of pressure generated by the string/cams, I would expect the shaft to flex in line with the string. As few things engineered by man are perfect, the timing of the roll over of the cams would tend to produce a horizontal energy wave.
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“The rifle itself has no moral stature, since it has no will of its own. Naturally, it may be used by evil men for evil purposes, but there are more good men than evil, and while the latter can not be persuaded to the path of righteousness by propaganda, they can certainly be corrected by good men with rifles.”

Col. Jeff Cooper
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  #24  
Old 03-13-2011, 10:34 PM
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Join Date: Aug 2010
Location: North West Washington
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Re: TAC 15/15i Basic Unpublished Information

On the broadhead question: The idea is to get all the blades on each of your arrows catching air the same way every time they are launched…for consistency/accuracy.
__________________
“The rifle itself has no moral stature, since it has no will of its own. Naturally, it may be used by evil men for evil purposes, but there are more good men than evil, and while the latter can not be persuaded to the path of righteousness by propaganda, they can certainly be corrected by good men with rifles.”

Col. Jeff Cooper
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  #25  
Old 03-13-2011, 10:37 PM
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Re: TAC 15/15i Another Accuracy/Maintenance Tip

Proper cleaning of either alloy or carbon composite shafts is mandatory prior to fletching with plastic vanes or natural feathers. White Ivory soap and hot water scrubbed onto the shaft with a new sponge and then wiping with a clean paper towel in one direction, one time and then air drying for ten minutes will produce a clean, oil-free shaft ready for the gluing process.

A small drop fletching glue applied to the leading end of the base of the vane is standard procedure after the vane has been glued to the shaft. I set a kitchen timer for ten minutes setting time for each vane glued while in the clamp. Twelve hours at 72 degrees F curing time will produce a bond that only a razor blade will remove. Cooler room temperatures will require a longer curing duration.

Depending on the vane selected, some bases of the vanes are treated with a primer and as such have a finite shelf life. I have found Bohnig’s Blazer vanes have been both durable and extremely accurate in my archery endeavors. I have an e-mail in at Bohnig as we speak relating the Blazer to the TAC 15and will report when it is answered. They also stabilize my largish fixed blade broadheads as well as my field points.

Bohnig’s FletchTite Platinum glue has produced excellent results on all shaft materials I have used.

I would also suggest the Bitzenburger fletching clamp tool as there is none finer on the market…the benchmark against which all others are judged.

Remember, after cleaning, touching the shaft or the vane’s base is verboten.

Numbering shafts is critical to sorting. Verifying both ends of the shaft are square is critical as well. Try placing your arrows point down on a hard surface and spinning them.
Wobbling equals poor flight. If you can see it, it will make a difference, particularly at extended range.
__________________
“The rifle itself has no moral stature, since it has no will of its own. Naturally, it may be used by evil men for evil purposes, but there are more good men than evil, and while the latter can not be persuaded to the path of righteousness by propaganda, they can certainly be corrected by good men with rifles.”

Col. Jeff Cooper
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  #26  
Old 03-14-2011, 12:11 AM
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Join Date: Dec 2010
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Re: TAC 15/15i Basic Unpublished Information

Hi Konrad,
Great input and a very needed discussion point! One of our members had recently noted in another thread that he couldn't get his broadheads and arrows to fly with any consistency at all.

After reading his thread I assumed it was due to the fact that the arrow shafts for the TAC15's are not spine measured and indexed by the manufacturer, nocks are not aligned to the spine either, so this would likely cause a high level of flight deviation due to the constantly varying spine deflections with each shot.

The typical process used in archery is to tune broadheads to your shafts by setting each broadhead to the exact same position on each shaft so they are all aligned to the same location in relation to the spine of the arrow. This provides a consistency of flight on each arrow.

The member who wrote the thread I'm referring to was suggesting that instead of tuning the broadheads to the shaft, for these arrows he's been doing exactly the reverse and tuning the shafts to the broadheads. He does this by gradually rotating each broadhead until he finds which position will steer the arrow to hit in the same spot as the others at longer distances (60 yards). Not all arrows can be redirected to hit exactly where the ones shot earlier are hitting. In those cases he removes this arrow from his final group.

It's a sorting out and tuning process, but in the end it leaves him with arrows that are good for very tight groups at longer range shots.

The side to side oscillation that you refer to is better known as the Archers Paradox. I'm not sure if the oscillation on these arrows follows that typically seen on other shafts for a number of reasons.

  • These arrows are much longer than any other crossbow bolts.
  • The new type of Carbon Filament Woven Fibers used in their construction have entirely different spine and flex points than any arrow that's come before these and are not similar in design to any other arrow ever made.
  • The Spine Deflection readings and characteristics are unique and are unpublished, which is why PSE had special vane configurations created to provide optimal flight performance.
  • All flight testing and data was developed for the 85 gram field points. Broadheads were tested later, but were not the basis for the shaft development matrix.
Can you provide any input or feedback on how your performance is when shooting at longer distances such as between 60 and 100 yards?

We have been testing and searching for ways to improve the accuracy at these distances and we now understand a good bit about the information I've outlined above. Don't get me wrong, these crossbows are very accurate compared to others, but we are looking for 3" groups at 100 yards and that's entirely possible if we can find a way to make each shaft fly the same as the one before it. It's already possible if you shoot the same arrow each time, but as soon as you change to a different shaft, you lose the accuracy.

I think many members would stand to gain a great deal if you've been able to overcome any of these issues and can assist us with any ideas on how resolving these problems can best be accomplished?

It's clear that you have a great knowledge base on crossbow properties and performance, so it's great having you on the team.

Thank you for sharing your knowledge with us on this thread. Please keep it coming, since there's so much to still learn and discover.

Jon
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  #27  
Old 03-14-2011, 01:18 AM
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Re: TAC 15/15i Basic Unpublished Information



Modern techniques in carbon composite and alloy construction of archery shafts have virtually eliminated the wooden shaft concept of a spine (a line of less deflection extending the length of the shaft). Alloy shafts have very consistent deflection rates all around the shaft diameter. Newer carbon composite construction techniques have also eliminated this issue. Early carbon composite shafts were actually “wrapped” for want of a better term and did present the tester with a specific area on the shaft with less deflection than in other areas around the shaft (where the material actually over lapped). This construction method also presented weight distribution issues of rotational balance and has been all but outdated over the last few years.
I would also presume all testing and development was done using the 85 grain point for one of two reasons:
A: In order to achieve correct forward of center (FOC) balance point.
B: It was technically impossible to develop a shaft stiff enough to withstand the forces applied by this system using a heavier point.
C: Or it was a combination of both situations…
Modern compound archer’s arrows usually hover around the 29 to 30 inch over all length and as such require a heavier point to achieve the 10 to 15% FOC. As a rule of thumb, the lighter the point, the less spine is required for proper flight. Typically, a high to moderate FOC will also produce better flight characteristics assuming the actual spine of the shaft is up to the task. Extreme FOC is seen as over 19% FOC. The use of a too heavy point causes erratic flight when using a weakly spine shaft.
A broadhead I would seriously consider would be the Muzzy Phantom MX 85 grain two blade.
http://www.shopatron.com/products/productdetail/Phantom%20MX%202%20Blade%2085%20Grain/part_number=4185-MX/182.0.1.1.1928.7266.0.0.0?pp=8&
Please, don’t let me confuse you as I do not actually own one of the TAC15 bows. I am a serious compound archer and life long chucker of projectiles various. The subject intrigued me since I receive an offer to enter the arrow give away. I am not planning on the purchase of a TAC any time soon (and said as much in my first reply to the offer) but know that the information I have gleaned over the decades will apply to this project. It was only after reading some of the posts that I decided to contribute.
My standard practice range is only 50 yards.
__________________
“The rifle itself has no moral stature, since it has no will of its own. Naturally, it may be used by evil men for evil purposes, but there are more good men than evil, and while the latter can not be persuaded to the path of righteousness by propaganda, they can certainly be corrected by good men with rifles.”

Col. Jeff Cooper
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  #28  
Old 03-14-2011, 01:53 AM
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Join Date: Dec 2010
Posts: 390
Re: TAC 15/15i Basic Unpublished Information

Your assessment of the reasons for the 85 gram point is "C". It was both of the reasons stated.

PSE sent the data they captured in their test labs on the force produced by the bow and asked Carbon Force to develop a shaft they could use on these xbows. The heavier the head you go to, the more flight anomalies become visible.

This would indicate as you stated that the spine compression being produced with anything over 100 grams is likely pushing the limits of what these arrows can handle. The engineers at PSE have recommended the 100 gram Steel Force, Phat Head Broadhead as one of the better performing heads they tested. I believe a lighter head in the 85 gram weight would probably provide better arrow flight if the head can be prevented from planing or steering improperly.

Carbon shafts seem to have a number of consistency problems that can vary from nonuniform consistency in shaft wall thicknesses to not being perfectly symetrical over the shafts length. Whilst I agree that the latest generation of carbon shafts are reported to have overcome some of these weaknesses, they are still not flying with consistent grouping capabilities.

Each shaft flies with unbelievable repeat precision and almost same hole accuracy at 60 yards. When shooting a group of shafts the performance of the groups opens up by as much as 5 or 6 inches.

In my experience, this is not a fletching attribute, it's typically a spine (Nock Indexing) or shaft deflection attribute.

Can you shed any additional light on this or do you have a different opinion on the likely cause?

Regards,

Jon
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