Broke my bamboo

[BCWV]

I was tillering my BBO. I did have some trouble with a hinge on the other limb but got it worked out and the tiller was starting to look pretty good. I heard a crack, took it of the tree and the boo had broken at just shy of mid limb.

 

 I know that I over stressed the boo to have it break but not sure why. My boo was 1/8" at the break and the osage was a little over 3/16".

 

 Did I get my osage too thin? I still needed to finish tiller and get my weight. I'm thinking I should have went with a more rounded belly. What say ye?

 Thanks
 Brad

[bowhntineverythingnh03743]

Where ido you take your measurement of the bamboo? Looks  thicker than 1/8. You want to measure it in the middle of the crown.

[Roy from Pa]

The boo does look way too thick, and you want to trap the back of the bow and round the belly and sides of the bow.  Don't leave any square edges, looks like the whole bow is square. But boo has a habit of doing that sometimes. You can sand the boo off and put another piece on, just go slow sanding and when you start to see the glue line back off and switch to hand tools. Also did you remove the rind from the boo? Looks like you did, you just want to barely remove the rind and don't scrape or sand into the power fibers.

[BCWV]

Justin,
 No, I measured the edge. Just thought I knew what I was doing   :(   .

 Roy,
 Looks like I left the boo to thick. I'll give it another shot with thinner boo and round my corners on my next run.
 I did scrape the rind but just enough to get it off.
 Thanks

[kennym]

Question for ol boo-boo Roy and guys??


When you do a boo backed whatever, do you do the profile width on the boo before you flatten it and thin it?

The bow I tried with 2 lams of osage, I flattened the boo then glued up and then it blew the osage when limbs were narrowed to profile. I noticed the boo  was now really thick toward limb tips after tapering to tips.

[Millhimes]

Correct kenny.Cut the boo to shape first,then thin it to 1/8" measured between the nodes.measure to the crown of the boo.1/16" at the tips--Joe

[macbow]

Ken, I flatten mine till the edges,are 1/16 or less. Then cut to shape. Then thin some more. I prefer about 1/16 on the edges.

[jsweka]

That's a real bummer Brad.

[Roy from Pa]

Yupper, first I run it across the jointer to get the belly flat, then lay out my bows pattern on the flat side and cut that out almost to the line, then get to the line with hand tools. Then I thin it way down, 1/8th at center of handle to 1/6th at tips. Make it thin so it's very flexible. After glue up and it's all cut out, I trap the back of the bow a good bit, do facets on the belly side and then round the edges over.

[J.F. Miller]

I'd be curious to see a picture of the belly opposite where the bamboo let go. in the second picture it looks like there is a slight dish in the core thickness. could be an illusion, hard to tell.

either way, the bamboo might be a touch thicker than what I consider ideal, but that would not cause an outright tension failure, but rather it would overpower the core and cause a compression failure. after the belly caves, then the bamboo will let go. is the belly fretted to hell in that spot?

if you don't have any damage on the belly in the same area that the bamboo came apart, then I think you may simply have a bad piece of bamboo. sometimes lesser quality bamboo will just splinter up like that for no good reason, and without warning. where did you get your bamboo?

[macbow]

I agree with J. F. It should not have caused the the tension failure.  Probably something to do with the hinge or bad bamboo.
What glue did you use? If tite bond PatB says a heat gun will loosen it.
Other wise a lot of grinding to save the Osage.
It does look a little thin where the hinge was.

[Roy from Pa]

When I have to remove boo like in this case, I clamp the bow down on my work bench and use a belt sander to get most of the boo off, sand across the limb. It won't take but 5 minutes to sand it off. But once you start seeing the glue line, stay away from that area with the belt sander. BBO bows are a love hate relationship because of boo throwing up splinters. But they sure are pretty and quick when they hold together.

[BCWV]

Jamie,
 I got the boo and osage from Pinemountain as the BBO kit. The hinge I had was on the other limb but that's not saying that I may not have had a thinner spot there.

 Mac,

 I used Unibond glue and have the boo sanded off already and smoothed everything up. I didn't notice any big difference in thickness but should have paid more attention.

 Roy,

 I'm not on the love side of my first boo relationship but it's not the boo's fault it's all mine.
 I tillered out another osage self bow today to try to get happy again and end the week on a high note. It seemed to work for me   :D

[Roy from Pa]

Brad, I wish I had a dollar for every BBO bow that blew up a splinter on me, I could buy a case of beer:)
The second piece of boo might not come out as smooth on the sides at the glue line, but all that is going to get faceted off anyway. I trap the back of my BBO bows a good bit.

[BCWV]

I had it coming Roy. I've been very lucky so far. It was just a matter of time before it ran out. If bowbuilding goes like the rest of my life I'll probably blow up the next 10 or so.

 I'm not quitting on it, just need a break   :D

 Thanks for all your help!

[Roy from Pa]

I've had bad streaks of luck and good streaks of luck with bows. Just goes with the process I suppose.

[bowhntineverythingnh03743]

Do what Ol Roy says and grind it off... will be worth the effort. I just did the same thing to this one and had to add a thin lam of osage. Before the fix it was 30# and then cracks all in the boo... After the fix I got it to 45# and it is only 58" n-t-n.