Primitive Archer

Main Discussion Area => Bows => Topic started by: toomanyknots on November 12, 2010, 08:52:14 pm

Title: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: toomanyknots on November 12, 2010, 08:52:14 pm

Just curious. It makes sense that it would doesn't it. ? Someone has had to think "I want this 50# bow design to pull 70#", or " I want this kids bow design to pull about 10# less. So if the above assumption is true, could I figure out what fraction of wood I would need to add of/reduce to get the weight I want from an existing bows design?

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: Little John on November 12, 2010, 08:58:31 pm

If you reduce the width by half you will lose half the draw weight. If you reduce the thickness by half you wont even have a kids bow.  Removing even small amounts of thickness decreases the draw weight by bunches.     Kenneth

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: jeff halfrack on November 12, 2010, 08:59:23 pm

width=2x strength    thickness=8xstrength    some thing  like  that,   anyone????   JEFFW

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: NTD on November 12, 2010, 09:27:14 pm

Yep, that's the way I remember it Jeff ;)

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: toomanyknots on November 12, 2010, 11:20:24 pm

Alrighty... kinda get confused sometimes trying to understand stuff. I always thought the 1 to 8 ratio thing was just a ratio of width to thickness, or something. I'm not good at explaining myself really. But thank you! (I get confused too easily, lol)

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: Pat B on November 13, 2010, 12:01:25 am

Take an 8' 2x4 and lay it flat with each end elevated and press on the middle. The 2x4 will bend. Turn it on edge and set it up the same and press in the middle. Bet you can't bend it!  ;)

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: Badger on November 13, 2010, 01:47:28 am

  I think 25% of the thickness will lower the strength by 1/2 or pretty close. Steve

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: Del the cat on November 13, 2010, 05:38:04 am

Quote from: Badger on November 13, 2010, 01:47:28 am

  I think 25% of the thickness will lower the strength by 1/2 or pretty close. Steve

whoops. you mean 25% OFF the thickness, 25% of the thickness will give a floppy lath.
To answer the original Q
Stifness of a beam is proportional to the cube of the thickness. which is where this factor of 8 comes from 2x2x2=8
So half the thickness is 1/8 of the stiffness.
Del

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: Jim Davis on November 13, 2010, 09:38:55 pm

Del, I think Badger l means remove 25% not leave that amount..


Jim Davis

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: Del the cat on November 14, 2010, 05:22:56 am

Quote from: asharrow on November 13, 2010, 09:38:55 pm

Del, I think Badger l means remove 25% not leave that amount..


Jim Davis

Of course I know what he meant...I was merely correcting the english for the benefit of those who don't (who asked the question) and have to rely on the accuracy of the written word.
I realise that sloppy english and spelling is the norm on the internet, but for anything with a technical content correct usage and accuracy is vital.
I daresay this mini tirade is full of typos, but none of them has the potential to ruin a bow.
Sorry if I sound like a pedantic A hole :-[ .
Del

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: Jesse on November 14, 2010, 12:52:46 pm

Del you crack me up :D

Title: Re: If I reduce a bows thickness by exactly 1/2, will it reduce the bows wieght 1/2
Post by: Badger on November 14, 2010, 03:00:09 pm

     I tend to struggle with the human language and don't take offense when someone fixes my screw ups LOL. Steve