blow up.....

[trentcur]

Ok I obviously am doing something very wrong. THis is my third blow up in a row. I have built prob 15 board bows...... but havent built one in about a year.

Last three atempts now have all broke. So to examine the things that I am doing differantly......... I have been gluing reflex into the bows...... and have been trying th leave the outer 1/3 of the limb a little stiffer. I think this may be my design flaw that is causing all of the blow ups. this bow was a kids bow, was right on target at #20@23..... had it at #18@22 on the tree and she exploded.

Any ideas as to what in the world I am doing wrong? Sorry I didnt take a pic when on the tree, didnt think she was gonna blow. THe braced profile looked good and the tiller looked good too...... but like I said I have been trying to leave the outer 1/3rd a little stiff.

I am going to take a few weeks off before my next go...... 3 in a row is hard to swallow. Gonna go stump shooting for a while.
 

[trentcur]

oh and this bow was 50" long and maple backed maple. backing was 1/8" and glue was urac185. heat box was used and kept at 110*. before she blew I stuck her back in the box at 80* for half and hour to warm the wood. then strung her up and continued the tiller....... then bang......

THE END

[trentcur]

looking at that joint it almost looks like the wood was starved for glue...... I left the surfaces smooth (prolly shoulda scored with a saw blade)....... does this look a little dry at the glue joint 2 u as well?

[vanillabear?]

[Pat B]

How was the grain on the backing. Did it fail in tension?  It may also have been too dry. You probably didn't need to "warm" it up before shooting it. Better to exercise slowly. How soon after glue up did you begin tillering?

[trentcur]

glued it up left it in the heat box for 2 hrs.... unplugged let cool and began tillering 12 hrs after it was cooled down. will throw in some more pics of the break

[trentcur]

 

this is a pic of one of the other bows that a blew up at final tiller as well. THe tiller wasnt done so it wasnt perfect, right limb was a little stiff and what not. But ya it was the left limb that blew on this bow.
 

I got my maple from a local hardwoods store. I tried to find quarter sawn (looking at endgrain looked like the top third of a circle). they said it was hard maple..........

[psychmonky]

Im in my phone so its hard to see in the pics, but are your edges square or did you round the corners before tillering?

[trentcur]

I rounded and smoothed the backing and rounded the belly wood as well. I kept the edges rounded the whole time............      

[Pat B]

Sometimes it just happens!

[fujimo]

one thing that always worries me with self/wooden bows- is when they are left on a tillering stick/tree for extended periods of time- i really believe this super stresses the wood.
a friend of mine had numerous bows break at longer draw- until we finally figured out what he was doing- he quit doing it and his bows started surviving.
i pull to the required draw hold the rope by hand- use my tillering gizmo right quick- and then let 'er down.- with lots and lots and LOTS of exercising!!
full draw pics are taken by my beautiful wife , (with me doing the drawing). max 2 - 3 seconds at full draw- just enough time for her to utilise her amazing artistic flair and her exquisitely shaped and perfect hands to take the most perfect picture     :rolleyes:  


jus' my .02c worth

[trentcur]

fujimo....... I have noticed the same thing and try to keep the position on the stick as short as possible. I usually just excercise with my pully while tillering........ when I get to the very end I nock her and step back for inspection to reveal anything I might have missed (or to take a picture;)

Oh well I am thinking that this wood may have been dry as well as these bows were all from the same 2 boards.

Ill be back home in 2 weeks and will start my next bow. I have some real nice boo and IPA waiting to bend:) flattened out my boo tonight. Ill change my luck with that build  

[fujimo]

best of luck-
i am sure it will work out well.

[gringol]

I've measured mc in maple boards at as low as 3%.  I believe that is excessively low, but there isn't a lot you can do once the wood is kiln dried to a mc that low.  Also, I agree with vanillabear regarding type of maple.  It is not all created equally...