Author Topic: mass calculation please  (Read 1452 times)

0 Members and 1 Guest are viewing this topic.

Offline stuckinthemud

  • Member
  • Posts: 2,300
    • avenue woodcarving
mass calculation please
« on: August 18, 2017, 01:33:39 pm »
Hi guys, I can't access my laptop for a while. Could someone calculate a projected draw weight for a 77"ntn bow weighing 30oz with tips and handle in line?
Thanks, Andrew

Offline Pat B

  • Administrator
  • Member
  • Posts: 37,520
Re: mass calculation please
« Reply #1 on: August 18, 2017, 01:45:25 pm »
Andrew, do a search here on PA. I just pulled up lots of info there.
 Badger(Steve) wrote a chapter in TBBIV that explains his mass theory.  Lots of other good stuff in that book also.
Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline Stick Bender

  • Member
  • Posts: 2,003
Re: mass calculation please
« Reply #2 on: August 18, 2017, 05:00:50 pm »
There is a lot of variables in your question ,handle/fade length,limb reflex if any draw length Etc  I always calculate manually from TBB like Pat said ! 
If you fear failure you will never Try !

Offline Badger

  • Member
  • Posts: 8,119
Re: mass calculation please
« Reply #3 on: August 18, 2017, 05:29:27 pm »
        If it was a yew long bow I would expect it to be pulling about 130#, from most other woods about 110#. If it were a stiff handled longbow with no reflex I might expect to see about 75#. You really need to know everything about the bow to calculate the mass. The bow might be too thick too bend right now and weight 30 oz, just no way to really tell for sure.

Offline stuckinthemud

  • Member
  • Posts: 2,300
    • avenue woodcarving
Re: mass calculation please
« Reply #4 on: August 18, 2017, 06:57:43 pm »
I smashed the screen, so no excel, no TBB! its a compass bend elb, slightly characterful blackthorn, Just over 1 inch squared at the centre, 15mm at the tips, parallel for the inner thirds, straight taper to the . I've got 4 inched of movement on the floor tiller and its ready to come off the long string. Too heavy for my scales.

Offline Badger

  • Member
  • Posts: 8,119
Re: mass calculation please
« Reply #5 on: August 18, 2017, 07:30:41 pm »
  1" is pretty narrow for a 77" long bow. If your bow has been on the long string what does it read at how many inches. Not interested in how much tip movement you have. How far is your long string hanging loose. Try to use a long string that hangs down about 6" or 7" and keep it on the long string till you are closer to target weight. You will probably loose another 4 or 5 ounces tillering so I imagine you will be about 80# or so. Are your tapers already built into the bow? Are you going for as much weight as you can get out of it? There is a technique you can use for that.

Offline stuckinthemud

  • Member
  • Posts: 2,300
    • avenue woodcarving
Re: mass calculation please
« Reply #6 on: August 19, 2017, 04:17:06 am »
The long string is hanging down 2", I'm not chasing a target weight, just seeing what the stave gives me. The tapers are built in and the bend looks pretty even. Will put some scales on it when I get a chance, but mine only read to 50#

Offline stuckinthemud

  • Member
  • Posts: 2,300
    • avenue woodcarving
Re: mass calculation please
« Reply #7 on: August 19, 2017, 03:15:29 pm »
Got my scales on it; it takes 35# at 3". That's  pretty much as far as I've taken it, the outer third of one limb is still a little stiff, but its nearly there

Offline FilipT

  • Member
  • Posts: 821
Re: mass calculation please
« Reply #8 on: August 20, 2017, 06:40:43 am »
Can someone say what do I write in the handle length when I have longbow/warbow? Do I put 0? My handle length on stiff handle bows is 4", and fades are 2". Do I put 8" for stiff handled bows? Thanks for answers.

Offline stuckinthemud

  • Member
  • Posts: 2,300
    • avenue woodcarving
Re: mass calculation please
« Reply #9 on: August 20, 2017, 08:31:49 am »
For bendy handles, I've been using 0; for stiff handles then I use the design length of the non-bending section

Offline FilipT

  • Member
  • Posts: 821
Re: mass calculation please
« Reply #10 on: August 20, 2017, 01:54:25 pm »
So I thought, thanks.