This first shot with our new Mk. VIII limbs struck a tad low and scuffed a two foot  furrow in the dirt before burying itself twelve inches into the old pine log at the edge of our parking apron.  I have laid an identical bolt shaft and head on top of the log to indicate the depth of penetration.

Of course this much of a puncture may say as much about the relative rottenness of our parking log as it does about Firefly’s actual performance.   …..Although the shot looked quite fast for the measly 2500 lb draw weight that was used…….   Still only a flashing error reading from the new chronograph.  I may have to mount it separately on a tripod to avoid smothering the poor thing with too many vibrations.

Tomorrow I will take a chisel to this log and we will see just what is what.  Got to get that chronograph working.

Here is the vid of this shot.  Note the dismally slack bowstring.  First shots in a tune-up sequence are always thus.

Click for Vid:       n20110928164955(1)

P.S.   Just got through  playing this vid in slow motion.  It looks like that sloppy string slaps itself all the way out over the chronograph.  I’m hoping that’s the cause for the error reading.

P.S.  P.S.   I remember what old Dale Sorrels used to say,  “When in doubt, and only absolutely, positively when you’ve tried  everything else, take a look at the instructions.”   Oh yeah, that…..   So anyway,  I had assumed the flashing 2 and 04 that appeared on the chronograph were error readings.  Not so it appears.   This particular device calls out the velocity by code.   It now appears that this first 7000 grain bolt launched with the VIII limbs was traveling at 204 feet per second.   Not hopelessly bad given the relatively low level of  torsion that has been induced into the bundles so far.  Also that loose bowstring is a real velocity killer.

I feel  stupid for not reading those instructions more carefully Dale.

5 Responses to “How old is rotten?”


  1. Pat B says:

    Good to see you up and shooting again, Nick.

    A couple of questions.

    First, from the vid it looks like a near-90 degree cocking angle, though the force is only 2500 lbs. Is that because you’ve substituted lighter bundles for the old ones (which you were talking of doing) or is it just that you haven’t employed any pre-tensioning?

    Second, I’d like to ask how your chronograph works. I’m imagining that you have to prime it with data first, telling it the length of the object whose speed is to be measured. In action it clocks the tip as it passes, and then the tail, and calculates the speed from length/time. Is that right?


  2. Pat B says:

    Re the chronograph – unless it works in some very novel way (and the word “Doppler” leaves open that possibility), I’m suggesting an error due to its being too close to the bowstring and clocking the missile’s velocity too early. If I’m judging lengths correctly, the bolt is still being accelerated by the bowstring as the tip passes the sensor, and won’t reach peak velocity until it has travelled several more inches – possibly as much as a foot. In that case the true exit velocity will be higher than the reading says. To get an accurate reading, you’d have to move the chrono further away, so the tip doesn’t pass the sensor until the bolt has left the bowstring.

    That is, provided my assumptions about the way this device works are correct.


  3. Nick Watts says:

    Pat,

    All that I know is that the new chronograph is based on microwave radiation and that it is specifically designed for archery use. I believe it works on the same principle as a traffic cop’s radar gun. I have lowered it so that it now sits 2″ below the top of the bolt groove rather than 1″. It seems to work fine now.


  4. Nick Watts says:

    Also: The bundles are the same as last time, I am only just starting the pre-tensioning procedure, thus the low draw weights and velocities.


  5. Pat B says:

    Yup, I figured out about the bundles with your subsequent posts.

    If the chronograph works like a radar gun, then I guess it’s probably OK where it is, because the doppler effect wouldn’t take place until the tail of the missile is moving away from the sensor – i.e. after the missile has reached peak velocity. Even so, I’d read those instructions carefully. Vertical positioning could be a factor too.

    Here’s hoping.

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