Author Topic: BOW BREAK HELP  (Read 405 times)

Offline Tyler Langston

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BOW BREAK HELP
« on: December 03, 2009, 08:41:00 PM »
Board bow 60" ntn, red oak first time building a board bow and it broke i was wondering what i can do with my extra piece of lumber to make another one of these so it dont break to. Any information will help.
http://s845.photobucket.com/albums/ab14/tlangs31/?action=view¤t=101_4804.jpg" target="_blank">http://i845.photobucket.com/albums/ab14/tlangs31/101_4804.jpg" border="0" alt="Broke below the handle">http://s845.photobucket.com/albums/ab14/tlangs31/?action=view¤t=101_4805.jpg" target="_blank">http://i845.photobucket.com/albums/ab14/tlangs31/101_4805.jpg" border="0" alt="broke below the handle">http://s845.photobucket.com/albums/ab14/tlangs31/?action=view¤t=101_4808.jpg" target="_blank">http://i845.photobucket.com/albums/ab14/tlangs31/101_4808.jpg" border="0" alt="Back side of the other half of the lower limb">http://s845.photobucket.com/albums/ab14/tlangs31/?action=view¤t=101_4809.jpg" target="_blank">http://i845.photobucket.com/albums/ab14/tlangs31/101_4809.jpg" border="0" alt="grain of the back side of the bow">http://s845.photobucket.com/albums/ab14/tlangs31/?action=view¤t=101_4810.jpg" target="_blank">http://i845.photobucket.com/albums/ab14/tlangs31/101_4810.jpg" border="0" alt="back side of the bow where it broke on the lower limb">http://s845.photobucket.com/albums/ab14/tlangs31/?action=view¤t=101_4811.jpg" target="_blank">http://i845.photobucket.com/albums/ab14/tlangs31/101_4811.jpg" border="0" alt="Back of the bow">http://s845.photobucket.com/albums/ab14/tlangs31/?action=view¤t=101_4803.jpg" target="_blank">http://i845.photobucket.com/albums/ab14/tlangs31/101_4803.jpg" border="0" alt="Photobucket">

Offline Stiks-n-Strings

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Re: BOW BREAK HELP
« Reply #1 on: December 03, 2009, 08:50:00 PM »
Go back to photo bucket, scroll your mouse over the pic and it pops up a little thing under the pic. Right click on the IMG icon and then left click on the highlighted area and click Copy. go back to your post and right click then paste.
 that should get your pics up.
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Offline 4est trekker

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Re: BOW BREAK HELP
« Reply #2 on: December 03, 2009, 09:08:00 PM »
Hey, Tyler.  Sorry to hear about your bow.  Here's some questions and some observations that might help you next time.  (I had to past your pictures in my web browser, but I got there!  I've pasted them at the end of this post for you.)

1) How did the bow break?  On the tillering tree or while drawing by hand?  Were you using a tillering string or a short string with the bow at brac?

2) 60" is awfully short for a red oak board bow of nominal draw length (26-28") and draw weight (#45+).  In my experience, it's just too short.  Not sure if it blew before you reached full draw or not, but regardless...make it longer next time.  I use the following formula:

      Bow Length=((Draw Length x 2) x 1.15) + 1

That is, I take the draw length, double it, add 15% (multiply it by 1.15), then add 1".  

3) It doesn't appear that you rounded the edges of the bow limbs at all.  If you did, it doesn't look like much.  This allows the stress the back is feeling under tension to build up at that sharp edge and lift a splinter, which can lead to a full-width break.   Always round the edges before you begin tillering/drawing the stave, ESPECIALLY on the back.

4)  You handle looks a touch long.  That is, the distance between the fades is too long, which further reduces the working length of the already-too-short bow.  Further, the inner third of the limbs take the most stress during bending (especially the inner third of the lower limb when the bow is drawn in the hand).  Also, your actual grip is a long ways from the upper fade.  The lower you grip a bow on the handle, the more it effectively shortens the lower limb.  This puts that limb under more stress, which can lead to limb failure.  

5)  The board looks like it's just shy of quarter-sawn.  Sometimes the grain of quarter-sawn or near quarter-sawn boards can appear rough.  My question to you is, is that back of you bow perfectly smooth?  If not, it makes splintering much more likely.  Again, maybe my eyes are just not seeing it correctly in the picture.

Keep it up, guy!  Make the bow longer and wider than necessary when just starting out.  It allows more wood to share the load.  You can always build them shorter, thinner, narrower, and lighter in mass as you get more experienced.  Get yourself another good board and make some sawdust!    


Here's your pictures, guy:

 

 

 

 

 

 

 

 
"Walk softly...and carry a bent stick."

"And whatever you do, whether in word or deed, do it all in the name of the Lord Jesus Christ, giving thanks to God the Father through him."  Col. 3:17

Online Pat B

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Re: BOW BREAK HELP
« Reply #3 on: December 03, 2009, 10:48:00 PM »
Sorry it broke. Looks like the side grain was too steep where it broke. Generally sound wood will break along a grain line. Your shaping and wood work looks good so time to move on to the next one.
  Check your other stave real well. Be sure the grain on the back and along the edges don't have severe violations. If they are questionable you may want to add a simple backing to help hold it together. Silk, linen, burlap or brown grocery bag paper and some TB glue will help with this.
Make the most of all that comes and the least of all that goes!
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Offline George Tsoukalas

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Re: BOW BREAK HELP
« Reply #4 on: December 04, 2009, 02:40:00 PM »
Tyler, here's my advice-forget the handle pieces glued on and forget the cut in shelves. Those are for fg bows. Get a nice straight grained piece of red oak and make a bend in the handle bow. Go 1.5 for 50# or so and 1 3/8 in wide for 45#. There's a red oak board buildalong on my site. Jawge
 http://georgeandjoni.home.comcast.net/~georgeandjoni/

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