Linen-backed red oak break test --WARNING GRAPHIC CONTENT!

[k-hat]

Now that i have your attention   (it actually is quite graphic, you have to see a bow tortured and blown to pieces )  In retrospect i hate that i did this test (sentimental value of the deceased), but if we can learn something then it's worthwhile.

There's been a discussion in another thread about the merits (or supposed lack thereof) of fabric (eg silk, linen, etc) backings.  I have, well... had, a linen backed bow that i wanted to use to test the idea.  I thought posting it on another thread would be useful because it gives some insight into the "controversial" uses of board bows, red oak, and backings. 

Some specs and history:

Linen-backed Red Oak (linen painted brown  because i didn't like the look), TB2 for the glue.  This oak had very straight grain and about .8SG, a dream board.  Dimensions as tested are:
1.75" wide parallel then tapering to about .5" the last 12" or so.   (This was a Ferret's build-a-long bow)
ca64" ntn, 8" stiff handle, about .5" of reflex at the tips

History:  This was the second bow i ever made a good while back, before i joined this site.  The first was (intentionally!) a lighter version of the same for my son.  As with most noobs however, this one came in underweight and had to endure my "fixitis".  I forgot why i backed it with linen, probly all the suggestions of backing your first couple bows from the more experienced folk.  Here's some of what she's been through:

*tempered in reflex after coming in under weight
*tempered again a couple more times (last deeply charring it) to try to raise weight (thinking perhaps i just didn't do it right the first time lol)
*mind you, all of these tempering sessions happened AFTER backing with linen (THAT'S A BIG NO NO!)
*piked a couple times to raise weight (again )
*found string out of alignment, so i redrew center and shaved off 1/4" from side of each limb and reshaped the handle to bring it close to center
*tiller is outta whack cuz after all this i never bothered to adjust it after making changes

I put at least a few hundred arrows through her during all of this, and kept hearing a "tick" on the draw and never figured out what it was until one day i sighted down the bent limbs and could see a boatload of splinters trying to raise under the linen.  She's been in the corner ever since.


Here is a pick of just one of the splinters threatening to poke through the linen.  It's still under, but scared me enough to retire her.  There are many others along both limbs:



Was trying to get a pic of the frets (they are all over the belly on both limbs), but just a blurry pic of the charred belly (the REALLY dark stuff was scraped off).



Here she is at low brace (about 3", didn't feel like adjusting it cuz i wasn't gonna shoot it!)



This is at almost full draw, here 43#@27".  Surprised she still had this much weight.  You can see from these the tiller is way off!


CAN YOU GUESS WHERE SHE'S GONNA BREAK???

NOW the moment you've all been waiting for!! The video.  I have a string tied to the nock point and gonna draw her back until she snaps.  How far do you think she'll get???  Click to view the video (the "event" is at 44seconds):



Here is the carnage:


This is the same spot i showed earlier, splinter still the same!!!! (it looks more raised but it's just a better quality pic)



The unbroken limb still showing about .5" of reflex and almost the same profile after going to 36"!!!!!



Thoughts, comments, and questions are welcome!

[k-hat]

So what does this say to y'all??? 

Quality of a board vs stave bow?  Is there that much difference?

Is a linen backing worthwhile? That is, does it do something or is it just added weight?  Is there a linen-backing myth here?

I know what i think, i wanna know whatchall think!

[Slackbunny]

I think its pretty impressive that it got to 36 inches after splinters had already begun to form. I don't think any unbacked board would take that kind of punishment after splinters had already started.

[k-hat]

My thoughts exactly slackbunny.  It's also a testament to a good piece of red oak.  I don't know of many bows that could be overdrawn by 8" and not take a HUGE amount of set.  Even before the break i got it to about 34" and it had just started to make some splintering sounds.  I'm tempted to get some good epoxy, patch her up and get'r going again lol

[SLIMBOB]

Curious where it broke?  Which limb?  I would have said right limb 6 inches or so from the fade, but it looks like it may have been the left?

[Hrothgar]

That's an impressive draw length. I've always been a firm believer in backing bows and linen is my favorite material. I've broken a couple that were backed, but like you said, it was a crack and not an explosion (and not 36"). 

[Pat B]

It looks like it broke along a grain runoff. Check the grain lines along the side. The splinter lifted at one end of the runoff and it came out on the belly side.

[k-hat]

You nailed it slimbob.  Right limb where you said it.  I thought for sure it would go where that biggest splinter was if anything, but as I said that part stayed in tact.  I know it's not a scientific study, but it's hard to deny that a splintered-up bow would have held together through all that without the backing. 

One of the reasons i added all the abuse to the tale is because there was a lot of emphasis on the other thread about perfect glue surfaces, sizing the back, etc etc.  All that is good, but you don't have to do a perfect job to get some security/safety.  I laid the glue down, wet the linen, rung it out, laid the linen down, slathered some glue on top, and let it dry.

I wonder how long it would have held on if i had done a better job on glue-up, AND not tempered the belly after putting the linen backing on there.  I don't doubt that the heat affects the glue, i'm just saying we don't give good ole TB2 enough cred

I strongly believe i could have put another 1000 arrows through that bow if i hadn't done this test. 

[k-hat]

I'll take a look Pat, you're probably right, if you're talking about radial grain.  The longitudinal grain was just about perfect on this bow.  I realized after the fact that the rays (radial grain) were running at an angle on the back and sides (not steep, but certainly not parallel). 

[k-hat]

Yup you nailed it Pat, good eyes!  The break follows the radial grain from back to belly, and you can see the fracture runs parallel to the rays on the side when i hold the two pieces together. 

[bubbles]

Linen backing sure doesnt seem like dead weight to me.  It may not protect as well as a thick piece of rawhide or a wood or sinew, but it does offer some protection.

[mikekeswick]

The bow had a splinter lift under the backing. The board wasn't good enough to be a self bow and would have best been backed with a thin strip of hickory imo - no splinter would have raised then.
I'm a beliver in the saying 'if a jobs worth doing it's worth doing right'. I just don't think that linen is doing a job right - it's too much of a halfway measure to me.

[Del the cat]

Blimey, if that had been tillered better you could have pulled it all the way back to the UK .
Impressive that it went so far before blowing.
Del
(I think it would have been better if it had the 'Jaws' music in the background....  )

[k-hat]

Mike, dude!  Nobody's saying that a hickory backing isn't better than linen.  The board wasn't good enough to be a self bow??? It was severely abused and out of tiller!  Could it have been drawn to 36" with a hickory backing without breaking? 

Not everybody can get whatever materials they want when they want.  You work with what you have.  That's the way the primitives did it. 

The only thing I was trying to determine was DOES LINEN PROVIDE A MEASURE OF SAFETY.  I wasn't even sure how far this could go, but anyone who answers this question with a NO after this test is just being willfully blind.  Nobody says you gotta use linen, but it's nonsense to say it's not useful.

[SLIMBOB]

Interesting post.  I think there are points on both sides to this.  A cloth backing does add a measure of protection and this ought to clearly show that.  36" in a splintered back!  Still, better backings available than cloth.  Kind of goes without saying as far as I am concerned, as there is better wood available than Red Oak...but if RO is what you got, RO is what you use.  Ditto cloth backing.  Testament to ones skills to make a weapon from less than perfect material.  I think it shows the range of ones skills.  Why make a bow out of ERC?  Because you can.