Chrono Test - March 15

I tested two more limb pairs with disappointing outcomes for both. First up was set #73. This set does not have the reverse taper in the outer limb that most of the other limb sets have, so the thickness continues to decrease around the recurves, toward the tips.  The outer limbs for this limb set is left wider than those limb sets with the reverse taper otherwise, the tiller would end up very "whip ended".  

Drawn to 11" (6" short of full draw), I shot a heavy and light arrow at 387 fps and 438 fps, respectively, but there was substantial vibration and noise compared the prior set tested.  Dynamic efficiency for the 387 fps shot was 57%, and only 45% for the 438fps shot, which is very poor.  75% or better is expected at these low speeds. As a general rule, I do not shoot below 50% dynamic efficiency, therefore these limbs are far from contention.  Inspection revealed signs of compression around the nock groove so I aborted any further shooting at longer draws. 

Next up, set #61. I had high expectations for this set. The thickness profile controlling the bend is closer to ideal and the outer limb is stiff and narrow. It looked very good strung up. I lightly plucked the string a couple of times. The high pitch revealed good string tension at brace. Then all of a sudden, there was a loud popping sound and large piece of the left outer limb landed a sharp blow to my belly before coming to rest on the floor.  What a disappointment. The test ended without a single speed measurement. 

You can see in the picture that the glue bond at the fades between the belly-side glass and core failed since it pulled away clean in that area. Oh well. I have to remind myself again that it is better for this to happen at home instead of at the salt flats. 

I am sure it is salvageable. It will just add to the growing pile of footbow equipment needing repair. 

Alan