Primitive Archer

Main Discussion Area => Bows => Topic started by: Red Dwarf on February 08, 2009, 07:58:48 pm

Title: HBH failures. Whats going wrong?
Post by: Red Dwarf on February 08, 2009, 07:58:48 pm: I have now had two early failures trying for a hickory backed hickory flatbow.
Here are a couple of pictures of the latest.
The backing was 5/16 quarter sawn and the belly slat was 5/8 plain sawn.
I had 20# moving things 6" on the long string and the tiller looking pretty good and was trying to brace it to a low brace height to check string alignment whan things went bang. This is the second one that has gone the same way. It looks to me like a sudden backing failure but cannot figure out why. Do I have a bad board for my backing strips?
The glue is Urac 185 and I glued in about 1 1/2" of Perry reflex.

Hope you guys can help me out here.

Red Dwarf

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Title: Re: HBH failures. Whats going wrong?
Post by: PeteC on February 08, 2009, 10:12:15 pm: RD,it's looks like you may be right,a bad board,or either much too dry.Sorry for the breakage.I feel your frustration. God Bless
Title: Re: HBH failures. Whats going wrong?
Post by: Pat B on February 08, 2009, 10:46:42 pm: I'd say bad wood too. The only hickory backed bow I have ever had fail(broke across the back) was from a log that was given to me and I sawed it out into lam strips and a few belly pieces. It turned out that a fungus got into the log and went to work. Under the right(or wrong) conditions it doesn't take long for whitewoods especially to start to degrade.
Title: Re: HBH failures. Whats going wrong?
Post by: JackCrafty on February 09, 2009, 12:55:14 am: I just had a failure like that with elm.....the same kind of clean break without splinters. I'm pretty sure it's because the wood is too dry.
Title: Re: HBH failures. Whats going wrong?
Post by: Pat B on February 09, 2009, 01:23:57 am: Hickory can take being 6% M/C where most other woods can't take it that low.
Title: Re: HBH failures. Whats going wrong?
Post by: Hillbilly on February 09, 2009, 12:03:57 pm: Probably a bad board. Also, I think 5/16" is a bit thick for a hickory backing-1/8" should be plenty.
Title: Re: HBH failures. Whats going wrong?
Post by: nickf on February 09, 2009, 12:08:41 pm: can you get a closeup of the grain of the board?

greetings,

Nick
Title: Re: HBH failures. Whats going wrong?
Post by: Red Dwarf on February 11, 2009, 01:27:58 am: Here's a picture of the board that I cut the backing strip from.
Hope it's clear enough for you to make out the detail (haven't got the macro setting sorted out yet!)

Red Dwarf

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Title: Re: HBH failures. Whats going wrong?
Post by: Pat B on February 11, 2009, 01:41:33 am: From what I see in the pic, I also would have made backing strips with that wood. Hickory is tough stuff. It was either too dry or infected with fungi. It's almost impossible to get hickory too dry from my experiences.
Title: Re: HBH failures. Whats going wrong?
Post by: adb on February 11, 2009, 02:40:13 pm: Looks like a suitable board for backings to me. I also cut my hick backings to 1/8"... I think it's plenty. It sure looks like a tension failure to me, which is not common with hickory. I'd guess it may be weakened wood from the start. Hickory actually excels when it's dry. One other consideration... I don't like hickory as a belly wood. I think it sucks in compression.
Title: Re: HBH failures. Whats going wrong?
Post by: nickf on February 13, 2009, 07:02:45 pm: that should have done the job. Do you have some pics of the tiller of the bow? that's the most logical failure here...