Ozbow

Morning All.

Better Archery companies do a lot of R&D on their bows and test to far greater 'conditions' that they experience during normal use.

Here is a clip from Win & Win of a limb being tested to destruction. Note the failure of the core material, it fails differently as compared 'Vertical Laminated Bamboo'.

http://www.youtube.com/watch?v=UU92F1AIOJk

Is that a foam core material Grahame? It does seem to break differently to any wood or bamboo cored bows that I have seen break. It just seems to disintegrate.

Jeff

Stickbow Hunter wrote:Is that a foam core material Grahame? It does seem to break differently to any wood or bamboo cored bows that I have seen break. It just seems to disintegrate.

Jeff

Apparently the limb was a Black Douglas DX Ultra HEX6 BB2.

"SuperFlex core - an economical based synthetic core. Not a foam but a light-weight solid core forms an ideal foundation for ultra high performance limbs."

Daryl.

Thanks Daryl. What I also find odd is how the core seems to have completely separated from the outer carbon or glass as if it wasn't bonded correctly.

Jeff

Hi Jeff.

Stickbow Hunter wrote:Is that a foam core material Grahame? It does seem to break differently to any wood or bamboo cored bows that I have seen break. It just seems to disintegrate.

My best guess is that it was some form of foam.

p.s. WRT Photos. Have a look at this one and the post a few down from the photographer. http://www.archery-forum.com/showthread ... ompetition

Stickbow Hunter wrote:Thanks Daryl. What I also find odd is how the core seems to have completely separated from the outer carbon or glass as if it wasn't bonded correctly.

Jeff

Jeff, I had similar thoughts.

Given that the film of glue between the synthetic materials is probably thinner than glad wrap it may be almost impossible to see with the naked eye.

It looks as though some carbon fibre may have come away with the fragments of core material.

Daryl.

GrahameA wrote:My best guess is that it was some form of foam.

p.s. WRT Photos. Have a look at this one and the post a few down from the photographer. http://www.archery-forum.com/showthread ... ompetition

Thanks Grahame. That is a great photo alright as well as the story behind it.

greybeard wrote:It looks as though some carbon fibre may have come away with the fragments of core material.

Perhaps but it still doesn't appear like the composites are held together well. If I had a the limb core and glass of one of my bows come apart like that I would have real concerns.

Jeff

Stickbow Hunter wrote:
If I had a the limb core and glass of one of my bows come apart like that I would have real concerns.

Jeff

Jeff,

The only way to find out is to do some destructive testing.

Daryl.

Morning All.

greybeard wrote:The only way to find out is to do some destructive testing.

A number of years ago I tested an ELB style bow which had been backed with some "Fibreglass Tape and Epoxy" - the sort of stuff you use for "Stich and Glue Boats".

* The 1st lesson I learnt was that it can be difficult to test a bow to destruction - I was surprised at just how far you could draw the bow before it failed and how difficult it could be.

* The 2nd lesson I learnt was destructive testing does require some special equipment if you are going to do it. (And there are probably some bows you could never get to fail unless you had some big pulling gear)

Daryl & Grahame, Yes I do realise about the testing but if what happened in that video had of happened to one of my bows I would immediately assume I did something wrong with the glueing up process or the glass (I think carbon in the above instance) was faulty. I say this because the backing carbon broke across the bow as if it was cut and then the core material just exploded into pieces and there was virtually none of it left in tact with the carbon. It does appear some slivers of carbon were attached to some of the larger bits of core but it seemed rather clear that the belly carbon had separated from the core pretty cleanly. Obviously you would need to see the actual pieces to verify this.

The following would need looking at.
Why such a neat break in the carbon across the limb? I have seen this happen with glass once with a Vince Hamilton longbow of mine at the National Safari one year way back in the 1980's.
Why did the core separate from the carbon so cleanly?
Where the core did have slivers of carbon why did it break up into small pieces as it did?

Perhaps the above is normal for carbon. I don't know as I have never used the stuff. If it is normal then I would have doubts about using it. In saying that it is used widely now days so you wouldn't think the above was normal.

Anyway who knows; not me and I have no intentions of testing it to find out.

From the video I will say I have never ever seen a bow break in that manner before.

Jeff

at least it exploded away from the archer

Fanto wrote:at least it exploded away from the archer

Good point mate.

Jeff

Hi Jeff.

Stickbow Hunter wrote:From the video I will say I have never ever seen a bow break in that manner before.

Yes that is why I highlited it in my original post. I found it very different to the normal failures one sees,

GrahameA wrote:... Note the failure of the core material, it fails differently as compared 'Vertical Laminated Bamboo'. ...

An educated guess is that the failure occured in two parts. First the core material collapsed then the limb bent back and snapped as the limb became thinner due to core collapsing. I have seen a few foam core limbs whereby the foam has 'crushed' - although none in the recent years. Materials like 'Carbon Fibre" I seem to remember lets go all of a sudden .... there is no gradual fail.

Note : Failures in bows are relatively uncommon.

GrahameA wrote:Materials like 'Carbon Fibre" I seem to remember lets go all of a sudden .... there is no gradual fail.

The video seems to back that up.

Jeff

yes it's the same in structural engineering. concrete and steel fail very slowly. carbon and composites could be used in building structures, but they fail very dramatically and quickly.

Thanks Fanto.

Jeff

Here ' another couple from Border.
I believe the draw length was about 47 inches before it gave way.

https://www.facebook.com/photo.php?v=10152051555166181
https://www.facebook.com/photo.php?v=797426026949487