Archery Talk Forum banner

1 - 20 of 35 Posts

·
Engineer at Birth
Joined
·
284 Posts
Discussion Starter · #1 ·
I got my brand new Bear Arena 34 a couple weeks ago straight from the factory and after i got it set-up, I found that it was shooting substantially under IBO speeds. I know what you're thinking, "here we go again... another moron on archerytalk... IBO is tested at 70#, 30" draw, and a crazy light 350 gr. arrow... you aren't going to be getting the IBO speed unless you are shooting those exact specs... " I get that... I really do... Here's the thing, my 340 FPS bow was shooting a 309 FPS IBO speed AFTER considering the reductions for my draw length, poundage and arrow weight... So my 340 FPS bow should have been shooting in the 290's according to my arrow design software, but it was only chronographing 276 FPS at the bow shop. (good chronograph with accurate history)

So i started to investigate... I measured my axle-to-axle and it came out to be 3/8" longer than factory spec; brace height was right on the money; max poundage was 71#; at full draw it was holding 23#, which is a 66% let-off, rather than 75% like it was supposed to be. So i knew i had some issues... Not sure if "Skeeter," down at Bear Archery, was eating a snickers bar instead of tuning my bow, like he was supposed to or what...

Anyway, i went ahead and added twists to my buss cable and control cable equally and took some twists out of my string until the % let-off and valley felt better and until draw length was right (this took a couple iterations with d-loop length). At the end of this process, ATA and brace height both ended up 1/16" shorter than factory spec; max poundage bumped up to 73# and let off was a nice crisp 76%. After fine tuning till I could shoot bare shafts with fletched arrows out to 30 yds and it was holding nice and steady on my target and shooting exactly the way i wanted, then i was off to the bow shop to see what happened to my arrow speed.

After all the adjustments i found my arrow speed went to 295 FPS; which taking into consideration my draw length and arrow weight and poundage, translates to an IBO speed of 330 FPS. It's still not quite up to the advertised 340 FPS IBO speed rating, but we all know the published speeds take advantage of every tolerance benefit and rounding error possible, so I think it's about as close as i can reasonably get.

I was surprised at the effect of ATA and %-let off on my arrow speed. If you're having issues like I had, then you might check your bow for factory specs and maybe you can increase your speed like i did.
 

·
Premium Member
Joined
·
10,326 Posts
Good information, thanks
 

·
Engineer at Birth
Joined
·
284 Posts
Discussion Starter · #5 ·
I'm guessing they put the brand new strings on the bow and tune to factory specs all during the same 1/2 hr time period. The 3/8" longer than spec ATA makes me wonder if the strings stretched a bunch while it sat in the warehouse for months under load.
 

·
Registered
Joined
·
95 Posts
I'm curious, because I want to test some of this out and get more knowledgeable, what arrow design calculator are you using?
 

·
Registered
Joined
·
3,475 Posts
Where do you get the factory specs from and how do you measure that out?

I have new strings coming for my arena 34.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
206 Posts
I watched my buddy bust a dloop knot on his brand new never shot out of the box Bear Effect RTH. This of course caused a dry fire and derail of string, and busted his arm. The dloop was installed at Bears Factory. I have zero confidence in Bear equipment.
 

·
Registered
Joined
·
2,367 Posts
weird your over dw by 3# but still arent hitting ibo
 

·
Registered
Joined
·
20,670 Posts
It's amazing what tuning your bow will do.
 

·
Registered
Joined
·
20,670 Posts
Where do you get the factory specs from and how do you measure that out?

I have new strings coming for my arena 34.


Sent from my iPhone using Tapatalk
It's the advertised measurements of the bow. 34.5" ATA and 6.5" brace height.
 

·
Registered
Joined
·
2,037 Posts
Skeeter must have had a good breakfast and some amorous adventure the night before he set mine up (Arena 34).....it was shooting right at IBO with my DL, arrow weight, etc. But a good tune does work wonders!

G
 

·
Registered
Joined
·
20,670 Posts
OP what are all your specs?

What's the measured DL, draw weight, arrow weight, what's on the string and what type of chrono was used?
 

·
Registered
Joined
·
2,298 Posts
There is a small loss on the front side poundage that reduces the overall fps. Different by make most calc go off a average.

Looser noc, different rest, string weight not affecting fps right, i give 5 fps just from the cable guides.
 

·
Engineer at Birth
Joined
·
284 Posts
Discussion Starter · #15 ·
I'm curious, because I want to test some of this out and get more knowledgeable, what arrow design calculator are you using?
Archers Advantage Online software. I think a one year subscription was $12 - $15 or something. It's a GREAT tool for designing the optimal arrow. Instead of guessing arrow length within an inch or two, you can design your arrow for the sweet-spot balance between spine, weight and speed. It also estimates your arrow speed and once you select your bow model, it will automatically upload your bow's specs. I've used it to design arrows for 5 or 6 bows now. I've found that reducing the bow's advertised IBO speed by about 5% in the Setup/Bow tab will yield pretty accurate estimates.

Gotta be careful though; with computers... garbage in = garbage out... You need to be exact and accurate with your data entry in order to get useable results.
 

·
Registered
Joined
·
681 Posts
weird your over dw by 3# but still arent hitting ibo
He's not shooting draw length of 30 though. I shoot 65 lbs @ 26" and only shoot 270's with a 400 grain arrow.

Sent from my SM-G900V using Tapatalk
 

·
Un-bannable!
Joined
·
2,206 Posts
Never knew the factory tuned the bows or that D loops change draw length. ...........
 

·
Engineer at Birth
Joined
·
284 Posts
Discussion Starter · #18 ·
I watched my buddy bust a dloop knot on his brand new never shot out of the box Bear Effect RTH. This of course caused a dry fire and derail of string, and busted his arm. The dloop was installed at Bears Factory. I have zero confidence in Bear equipment.
That's prolly jumping to a conclusion, right there... I too have a buddy that shot a brand new Hoyt and it blew up in his hand on the first shot... I still have great respect and confidence for Hoyt products. I wouldn't make an indictment against a whole brand based on a single event; especially if the event was the failure of a d-loop and had nothing to do with equipment that the manufacturer even fabricated. Anyway, all brands have a one-off issue, or a bow that gets damaged in transport, or something.

I don't believe Bear pre-ties their d-loops on the bow string at the factory, so you'd be hard pressed to blame a d-loop on Bear. Also, why didn't your buddy give the d-loop a look-over before reefing back on it... and why was he drawing the bow without an arrow nocked-up?? Sounds like operator error to me...

Anyway, I've had great experience with Bear products and i've got a lot of confidence in Bear equipment.
 
1 - 20 of 35 Posts
Top