Bow failure. Diagnosis help please.

[Fractured]

Hello everyone,

Relatively new to bow making and have just started my fourth bow.  I've been cutting my teeth on board bows and have been trying different things on each bow.  My first bow was a  bend through the handle flatbow that I over-tillered to low poundage and cut in a shelf on the wrong side.  I went on to pike the bow and my wife is using it now (she's a lefty).  Second bow was for my daughter and was a shorter pyamid style bow with stiff handle.  I got a little rushed with heat treating and it broke trying to string it too soon.  Trying to learn as much as I can from each bow I make so I am here for some feedback on my third bow.

66 inch ntn pyramid bow with glued on stiff handle section.  Backed with fiberglass tape (I know, I know  ) as it is what I had and wanted to try a backing.  Unfortunately I didnt take pictures till after it failed but I would appreciate any feedback I can get on this one.

I had taken my time tillering with frequent trips to the tree never pulling up to my targeted draw weight.  Was aiming for 40-45 pounds at 29 inches.  Kept it under 35 pounds on tree.  Got it to brace and next trip to tree it started popping and cracking well before 35 pounds.  Here is a pic of tiller.
Bow1 by Matthew Chodat, on Flickr


Pic of the area where it failed.  Was about a third way up the top limb which is on the right side in the picture.
Bow1 by Matthew Chodat, on Flickr

I was also struggling with alignment on the lower tip and could not seem to get it to change effectively with wood removal. 
Bow1 by Matthew Chodat, on Flickr

On a different note...  I was very happy with how the handle turned out.  Was considering putting in a shelf.
Bow1 by Matthew Chodat, on Flickr
Bow1 by Matthew Chodat, on Flickr

Any input is appreciated!

Thanks in advance

[sleek]

I see nothing in the tiller that would warrant a failure in the bow. Yes it bends ever so slightly more there where you say the crack happend but not enough to cause failure.  Another interesting thin is that its a crack not a splinter, and it happened there on the side. Typically bows splinter towards the center when they fail. Cracks like that are caused by sharp edges and weak spots in wood. Your edges look like they arent crisp and square so I assume that's not what caused it either. I dont see a deep tool mark, nick, gouge or anything else there either. So, im just gonna say the wood was crap. Maybe you picked a bad piece. Neat to see the glass actually work for a change.

[Del the cat]

... Neat to see the glass actually work for a change.

Eh? The glass didn't work!
It didn't act as a bomb proof backing... the back cracked!
The glass is maybe just masking defects that may otherwise have shown up.
@ Fractured...
My advice would be don't "try something new" every time.... try to get something that works consistently, material, design, technique... then try small variations and changes. Floundering around changing random elements never gets you anywhere. A slow logical patient approach is needed.
Yeah ok, have a go at something mad now and again, but get the basics right first!
Del

[stuckinthemud]

Is there a tiny pin knot hidden under the tape?  A backing like that can mask problems you may have had chance to fix if you could have seen what was going on

[bassman]

My first attempt at making bows were made from Amish hickory wagon wheel staves, and  dry wall tape as backing, and wood glue. That tape did nothing to strengthen the bow's back with not so good at the time tillering. The bows would break on the back in a heart beat. What did end up working for me was double layers of F glass mesh cloth glued on the back with Smooth On using a Pyramid Design, and building many of the bows edge grain. Still the tillering had to be at least acceptable or the belly's would fret. Not Primitive, but successful, and that was what I was looking for at the time.  I also made some Sudbury bows that way that I have, and still shoot on occasion.That was better than 15 years ago. My how time flies.

[RyanY]

For it to break like that with so little bend and draw weight, there had to be some type of grain defect or issue with the wood's integrity.

[Pat B]

I think the wood was inferior or too dry. Sound wood doesn't normally fail on the back unless there is an underlying problem.

[sleek]

... Neat to see the glass actually work for a change.

Eh? The glass didn't work!
It didn't act as a bomb proof backing... the back cracked!
The glass is maybe just masking defects that may otherwise have shown up.
@ Fractured...
My advice would be don't "try something new" every time.... try to get something that works consistently, material, design, technique... then try small variations and changes. Floundering around changing random elements never gets you anywhere. A slow logical patient approach is needed.
Yeah ok, have a go at something mad now and again, but get the basics right first!
Del

I mentioned the glass worked to keep it from exploding,  not tgat it saved the bow

[bownarra]

So now you know that fg tape is useless for backing a wood bellied bow:)
A much better choice would be some linen cloth, silk, etc
Also your fades are too abrupt (thickness). You have a more or less straight line from handle down to working limb. This area should be concave with a more gradual blend into the working limb.

[Del the cat]

BTW. Site rules are no F/G at all in the "Bows" section.
It should be in the "around the camp fire" section... just sayin'
Del

[sleek]

Can hardly call it a bow at this stage eh? Hey rip that tape off and all will be well with the natives. And while your at it, toss the rest of the roll into the rubbish bin!

[Tommy D]

Sometimes bows break!! But what Del said makes sense - get a decent bow wood and work on a tried and tested design until you know you can repeat it - then you can start to tweak things here and there. Once you get a shooter you can always then play around with things - heat treat the belly, bend in recurved tips, pike the bow, stick a backing on it ... and you can then figure out which was the “straw that broke the bows back” so to speak...