Play with that brace height!!

[Rigs]

Greetings All,

So couriosity go the better of me and it was time to play...

When I first chrono'd Take Two, I averaged 182.6fps. 52#@29" with 9.55gpp (9.548gpp to be exact). My daughter Kassi would watch for the mark on the arrow to reach the front of the riser...

I decided to make sure I was hitting 29" and dug out a clicker...set it to the length of the arrow, grabbed the chrony again and hit the back yard. The average was a little slower, but not by much. Kas did good.

I then dropped the brace height from 7 3/16" to 6 15/16", weighed (still 52#@29"), and headed out to the back yard again. Average for the 10 shot series dropping a high and low averaged 184.9fps with 9.55gpp.

I even dug out an old fletch hunter release and shot it. I only shot three arrows as the bow didn't like the release much...190, 188.0, 187.8fps were what I achieved... The string has on some of my yarn silencers...I could step out and hunt with the bow tomorrow.

This was all done with the bow three feet from the front of the chrony. I'm really courious to see what this little bow would do @ 9gpp...

Back to the brace height. No more noise. The arrow still flew great (shot it quite a bit after the "testing" was over). The bow was dead in the hand as well.

I'm amazed that a few twists in the string grabbed me another 2+ fps without any illl effects on flight, noise, or accuracy... Have any of you seen this before?

Happy hunting,
Jason

[Hamish]

Is that a few untwists grabbed you another 2+fps?

[Hamish]

Interesteing the change in braceheight made no differance to the bows weight at 29" draw.

[longstick]

I was tuning some arrows the other day with my lomgbow and found raising  the braceheight straighted them out great. They were porpoising a bit in flight. By rule of thumb Ive heard this is possible and pick up more speed by dropping but it will make the arrows a bit more on the light side on spine as well
This sound right guys?

[Rigs]

Hamish,

That is correct...  Dropped the brace height from 7 3/16" to 6 15/16".  

Longstick, no loss (sp) of draw weight.  No ill effects on noise or arrow flight as well.

Happy hunting,
Jason

[Hamish]

Thats what i think because of the extra cast you get from a shorter braceheight it will apply force to the shaft for longer and get more speed. But i have read that lower brace also changes the weight of the bow at full draw to be less 1-3# per inch of braceheight. But i have not done any tests on this myself just what i have read.

[Rigs]

Hamish,

I honestly figured in a loss of draw weight, but I was tickled it stayed the same.

Maybe this is one of those bows that just defies the "laws".  Either way, I am extremely happy with the performance.  This is the best design I've ever come up with in 5 years of bow building...

 

 

 

 

Happy hunting,
Jason

[Hamish]

Cannot see pics on my work computer Jason just gray boxes, LOL, but i look forward to having a look when i get home.

Cheers

Hamish

[Orion]

What you found out for yourself is published in just about every book on traditional archery.  Fun to experiment though.  Changing the brace height does not change the draw weight at a certain draw length.  For example, all a higher brace hight does is take up some of the draw before the shooter completes the rest of the draw.  Your assessment of the cause of the extra speed at the lower brace height is also correct.  At a lower brace height, the arrow stays on the string longer, absorbing more of the bow's energy.  In tuning, the trick is to find the lowest brace height possible which still yields good arrow flight and low sound.

[Rigs]

Jerry,

     Which books are you referring to?  I've studied tons and am still amazed by what I find out building my own bows...  The results I'm getting are worth posting.  

P.s.  Where u live in WI?  I used to live in Iola, Northland, and WI Rapids.

[Deadsmple]

Rigs,
I'm not sure which books Orion is refering to but I know it's stated in "Traditional Archery" by Sam Fadala.

[Hamish]

Your bow looks sweet Jason nice work mate.