Sneak Peek

[Shredd]

  Quit laughing Roy...  You'll give yourself a hernia...   

   Geez...  Do I feel like a dumb a$$...  Glad you caught that...  I thought the numbers seemed off (too high) but then I thought this was the first bow and it could have a bit more tension...  I think I am getting old...

   I divided the numbers backwords, which will give you 108...  The funny thing is I double, triple checked it...  LMAO...

  i am gonna go back and correct it...

  Thanks Bvas...

[Shredd]

  Well at least two good things came out of  this...  1.  I am glad it was a simple mistake on paper and not on the bow... 2.  I don't have to revise my formula...   Yay..!!!

[Roy from Pa]

I gotta admit,  I was LOL.
 

It only gets worse as you get older.

Like the time I was looking for my glasses on the workbench.

I found them, on my face.

LOL, looking for glasses and all the time I had them on.

So I understand shreddy..

[Forwardhandle]

Looks good there Shreedy did you lose the 5 1/2 lb sanding ?

[Shredd]

Yes... The first number is just rough sanded...  The limbs are now sanded to where the limbs are supposed to be...  I will still lose another 1 1/2 to 2 lbs when I do the finish sanding...

  Yeah Roy...  Sometimes I think I am losing my mind...  Which I probably am...   

[BMorv]

Lol.  I was asking so many questions I felt bad asking about how you got that number from that formula.  Hey it's your own formula right? You can divide it however you want.

[jess stuart]

Those are really good numbers, looks like you a winner.

[C. Johnson]

Could you humor a fat bald plumber and post a pic of how you're measuring the string tension?  I've never done this and I honestly can't picture what you're describing?

Also, please forgive my ignorance, but I'm not sure how a guy should use that information.  As in, what does a measurement of the string tension tell you?

[Shredd]

  Here is a pic of it strung up on a bow...  In general I just feel it is good too have as many methods possible to evaluate a bow...  That way if something is off or you are trying to solve a problem or trying to reach a goal the more tools or methods available to you to help you to see into the bow a little more deeper...  I am mainly talking about trying to reach max performance...  There are things going on inside a bow that you cannot see... I believe the numbers help you to see...

   I use the string tension number just as kind of a barometer...  If it is high I expect good performance from the bow... If it is low I expect sub-par performance from a bow... If it is high with sub-par performance it is time to start looking for answers why this is going on and visa-versa when it is low with high performance...  If you go looking and find the answer you get more knowledge about the bow, how it works and maybe learn a new trick to tweak performance...

   Sure you can trap limbs, add wedges, add some deflex or reflex, change limb angles and core materials... Monkey see monkey do and you might get lucky...   But how do you know what is really happening unless you have some concrete numbers to go by...  If you just have a bow scale to measure draw weight you are relatively operating blind...  Now add a chrongraph and you can see a little better...  With each tool you use you see better and better...  Tiller sticks to map limbs...  Tiller tree with a rope and pulley... A tiller tree that can accurately measure a DFC...  String tension scale...  When you start seeing the numbers changing for the better you know you are on the right track and getting closer to optimum performance for that bow...

   I call it the Alchemy of bow making....

   Hope I answered your question and then some...   

[BMorv]

I agree with you Shredd.  Why not measure what the bow is telling you especially if it’s as easy as attaching a bow scale to a turnbuckle and parachord.  I’m going to start measuring string tension after this discussion.
Have you had many instances where the string tension was low and speed was high?  If so, were you able to figure out why?

[Shredd]

  Not generally when it is real low...  But I have made bows when the string tension was high and they shot mediocre speeds...   I think there was one bow where the speed was not up to par but had high tension...  It was because the the end of the limbs were on the wide side and were probably carrying too much weight but the bow had a great side profile...  So I sanded the limbs narrower but the tension also dropped and so did the arrow speed so I stiffened up the tips with less taper in a lam on the next bow...

   I am a firm believer in the DFC also but your numbers have to be dead accurate or you will never be able to read it to make fine adjustments or accurately compare DFC's to other bows...  What I mean by dead accurate is that you need positive mechanical stops...  If you are eyeballing it  you are gonna have a funky curve and your numbers will be all over the place...  The DFC that I posted is a pretty sloppy one...  I am not sure what was going on but my numbers are generally in better order...  Although it is sloppy you can still see that my numbers  are mostly within 5/100's of a lb...  I have seen DFC's where they are a half a pound or more off...   When you see DFC's posted by a Pro source like a manufacturer you will sometimes see the numbers rounded off to the half pound and the curve doctored...  It tells the story and you get a general idea what is going on but it is not good for comparisons...
    The way to test it is to do two DFC's of the same bow and compare them...  If they are running .15 of a pound or more off its starting to get unaccurate and may make it difficult to compare bows for finer tuning... 
   When I say compare DFC's I don't mean they should have the exact same numbers down the line but they should be close... What I mean is when bow #1 goes down a half a pound between 12 and 13" so should bow #2...   And when bow #1 goes up a tenth of a pound between 24 and 25" so should bow two...  In theory and if everything is jibing, if bow#1 is .20 pound off from bow #2 at the 10" mark then they should also be off by .20 pound at the 28" mark...  But this is unlikely to happen because of Hysteresis...  Things will change a little every time you flex the bow...

[Buemaker]

Any ideas on how to make such an apparatus with dead exact stops at each drawn inch?

[Shredd]

  I have what I call a ratchet tree...  It stops at every inch...  It is a bit involved to make...  But you can make a simple device that basically is a long hook which hooks onto pins on the tree...  All you basically need is the first 6-7 numbers and the last 6-7 numbers...  You want high numbers in the beginning of your draw and low numbers at the end...
   You want to get the pins spaced close to exact as possible...  But if they are off a smidge it is ok, as long as you use the same tree for both bows when comparing...  I will try to post a sketch of it tomorrow...

[Shredd]

   My apologies...  I been super busy..  I get that sketch on here when I get some free time...

[C. Johnson]

Ok, thanks gentlemen.  I understand now.

[Roy from Pa]

I have what I call a ratchet tree...  It stops at every inch...  It is a bit involved to make...  But you can make a simple device that basically is a long hook which hooks onto pins on the tree...  All you basically need is the first 6-7 numbers and the last 6-7 numbers...  You want high numbers in the beginning of your draw and low numbers at the end...
   You want to get the pins spaced close to exact as possible...  But if they are off a smidge it is ok, as long as you use the same tree for both bows when comparing...  I will try to post a sketch of it tomorrow...

OMG this otta be good:)

[Shredd]

Ok...  Here is a sketch of a DFC Tree...  The tree is constructed of 2x4's...  Space out and predrill for nails as accurately as possible...  I think 20D nails will be better than 16's...  Put a little wood glue on each nail to keep it from coming out...   Make the hook out of 1/4" bar and weld a handle to it with a spacer in between the two...  If you got any questions, hit me up...

*** WARNING ***  Make sure hook is fully engaged or you may be wearing it on your face...

  The trick is rythm for a nice accurate DFC...  Once you start the process don't stop or stall... Don't rush but move quickly and have about the same amount of time between hooking each nail...  It helps to have someone to write down the numbers and read the scale but not necessary...  Use the same method for both bows...  Another words Don't have someone help you on one bow and not the other...

[Roy from Pa]

I'll be darn, ya stole my idear son...

[Shredd]

Whatcha got going on there??  All I see is a pully...  Maybe post a closeup...

[Buemaker]

Thanks Shredd.