Countryboy16

I was wondering about my speed. I am shooting a BT Tech 29 @28" and 62lbs. I shoot arrows that way 8.0 gr./inch and are 27.5 inches long. I hae a peep, a kisser, and a loop on the string. I was thinking in the neighborhood of 290 . . . . I hope. Any in put would be greatly appriciated. I would use bowjackson.com but i dont understand all that i need to fill in on that so i cant use it.

Thanx in advance.

PABowhntr

Countryboy,

I was originally going to bump this up for one of our current Bowtech gurus to answer but I figured, what the heck, I will take a stab at it.

The higher of the two advertised IBO speeds for the Tech 29 is 320 fps (70 lb draw, 29 inch draw length(since that is as high as the Tech 29 goes), 5 grains per pound).

You are "losing" roughly 10 fps for your shorter draw length and 14 fps for your lighter draw weight.

You mentioned that your arrows weigh 8 grains per inch and that you shoot 27.5 inch arrows which would give us a total of 220 grains but you did not specify what point weight you have on them nor what kind, length and number of fletchings you use. Assuming a 100 grain point weight (most common) and adding roughly 70 grains for fletching, insert, nock etc.... that would give you a total weight of 390 grains.

If that is your arrow weight then you will lose roughly 8 fps for that.

The peep sight, kisser and string loop will also reduce speed but that varies depending on style, weight and position on the bow string...but I think a 10 fps reduction in speed is probably pretty conservative.

Add that all up and you are looking at a reduction of 42 fps compared to the high end IBO rating of 320 fps. That gives you a speed of 278 fps.

Hope that helps.

BowTech_Shooter

Franks calculation sounds good to me.

500 fps

I think Frank is way off. I'm going to say closer to 279.<img src=icon_smile_big.gif border=0 align=middle>

Sorry, just trying to get a rack!

JeffB

Actually I think the speed will be abit slower than Frank stated simply ebcause a kisser is generally one of the worst things you can put on a string from a speed standpoint as they are usually heavy, and are close to the direct center of the string.

Also is the bow a 60 LB peak model? or is it a 70Lber lowered to 62? If it's the latter, the bow is operating at it's worst efficiency levels and will be significantly slower than the 60 LB maxed limbs.

I have shot 2 different T29's through 2 different chronos at 312 and 315 FPS w/ a 29&quot; module and 70/5 (IIRC).

JeffB

TheArcheryProgram

Depending on the actual finished arrow weight (I used 380 grains) I predict around 260 f/s.

Happy Shooting!



>>>------Tony Virnoche------>>>
>>>---The Archery Program--->>>

PABowhntr

I did say that my &quot;guesstimations&quot; would be on the positive minded side simply because I used the upper range IBO rating and a conservative guess on the reduction of speed based on the items on the string.

If we went with 312 instead of 320 and subtracted 16 fps instead of 10 for the items on the string then my &quot;low end&quot; guesstimate would be around 264....

...so, between 264 and 278 fps...<img src=icon_smile_wink.gif border=0 align=middle><img src=icon_smile_tongue.gif border=0 align=middle>

Pinwheel 12

I had a customer in with his Tech 29 with 29&quot; awhile back and we ran it through the chrono at 309 to 311 at 70lb, 5 grains, pretty close to being right in line with Jeff's findings.

Glad to see Frank has the energy to go through the calculations for you,<img src=icon_smile_big.gif border=0 align=middle> I would say he'd be close to being correct! <img src=icon_smile_wink.gif border=0 align=middle> Good shooting, Pinwheel 12

Edited by - Pinwheel 12 on 02/16/2002 16:03:28

Countryboy16

My finished arrow wt. is 375gr.