Any ideas why this one failed? More pics. added

[Red Dwarf]

I really would welcome some help with this one.

Hickory backed elm board bow. 62" ntn going for 45# @ 26"

It broke on the tillering tree.
I used 24hr cold cure epoxy to glue on the backing, and thought that the hickory/elm combination would have been almost indestructible.
Here is a picture of the break

And one of the bow just before it broke pulling 45#. I scraped a little more after this picture and pulled an additional 1" then POW!!

It was the right limb that went bang.

Red Dwarf

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[El Destructo]

Nothing jumps out at me....the Left Limb looked to be the Stiff one....,ooks like the Backing Broke....was this edge grained or Biased Cut Hickory?

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[Hickoryswitch]

I'm no expert but it looks like the hickory might have had somethin wrong with it. I've never seen hickory break that clean but like i said i'm no expert.

[Rich Saffold]

 Red Dwarf Have you got the heater going where the bow is?  It's quite easy to run the moisture content to low in the winter in these situations. You also have 45# at brace height which translates to about an 111# bow@28" . Elm and Hickory are tough woods, but you exceeded the limit for that bow ..

If you have 15#'s at brace height of 6",  and another 20" of draw at say 3#'s andinch gives you a 75# bow, a backed bow like that may not lose that much poundage, and depending on the unbraced profile you can see you need to have a little less poundage at brace than that..It really depends on the reflex etc. as well.

.At the point where your bow blew I'm still floor tillering the bow and getting a feel for how each limb reacts to the bending. It's real easy to lay more weight than necessary on the pully rope..

Hey It's only wood..You aren't the first to do this trick and you won't be the last...

Rich-

[Badger]

I see the same thing Richard sees. Looks like it may have over dried out. Looks like  brittle wood break, Steve

[mullet]

 Yep, as soon as I saw the straight across break, I have to agree with Rich and Steve. That's a lot of draw weight, even for epoxy and Hickory.

[Pat B]

The back definitely failed. The only hickory backing that has failed(it also broke across the back) for me was one that was infected with a fungus due to improper storage and seasoning. Here in the South East, we don't have too much trouble with over dry wood.      Pat

[Justin Snyder]

Before I agree I would like to see a side picture of the broken limb.  It looks almost like the backing might have delaminated then broke.  Justin

[jamie]

like pat said the only time ive had hickory break that clean was because it had a fungus problem. once it dried the area broke clean just like yours.

[Red Dwarf]

Rich

I was pulling 45# at 10" movement on a long string, not 45# at brace height.
The hickory was also from a board. I do not have any prior experience with either elm or hickory but can see no sign of any fungal decay.

Justin

I will post another couple of pics when I get back from work later today.

The RH in my basement shop is around 35%, temp around 19 deg. Celsius. I too was wondering about things being too dry, but, from TBB I read that both elm and hickory can tolerate some pretty low MC.
No idea of the MC of the wood, though being boards could they have been low when delivered?

Thanks for the help so far guys


Red Dwarf

[adb]

Kiln dried wood has very low moisture content, usually less than 10%. At 35% RH, it's going to be even lower. I keep my wood storage room at 45-50% RH. Hickory is very strong, but like any wood, it's brittle when too dry. This is organic bowmaking. Things break, and sometimes for no apparent reason. Your tiller sure looked good to me.

[George Tsoukalas]

When I do a board bow I choose one with no knots because I had a hickory board bow break at an even tinier knot. Jawge

[Red Dwarf]

Justin

Here are a couple more photos.

The backing took some elm with in in all but a small 1/4" x 3" SECTION.

Red Dwarf

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[jeduffey]

It happens to all of us. Look on the bright side, in addition to getting some more valuable experience, you have a nice start on a fine atlatl.