laminate bow exploded

[mnviking]

I know this is not totally primitive but I have been experimenting with bows made from wood laminates.  I have made several that shoot well in the 30-40 pound class from red oak and TBIII.  I decided I wanted to make an embedded handle one piece long bow recurve style using G2 two part epoxy and curly maple outer layers with hickory on the inside laminates.  I also put a partial laminate with tapered ends that was just about half the length of the bow --maybe 18 inches on either side of the center line-as the middle layer of the laminates.  total limb thickness at the tips about .3 inches  the limb thickness was about .6 inches near the handle. the  majority of the limb width was 1 1/2"  including the area around the embedded handle.  I had previously used glued on fixed handles about 7 inches long and wanted something with a smoother appearance.  therefore the try at an embedded handle.
So--i put on a long tillering string--the bow was 62" ntn and started to "exercise the limbs.  the upper limb action was really nice and springy.  well the next thing I knew the upper limb literally exploded with the the limb flying past me about 10 feet behind me.  I will be wearing safety glasses next time i exercise a new bow.  wow.  the limb broke right were the internal laminate taper ended.  the g2 two part epoxy was great as it did not let go -the wood literally shredded.  the laminate layers were all .1 to .15 inches thick. 

so for what it is worth to someone out there --that is what happened on this experiment  explosive power -i didnt realize

[longbow steve]

Curly maple probably isn't the best option for an outer lamination unless you use glass. It is hard to visualise what you describe but that may be where the problem stemmed. Steve

[Pat B]

Curly maple is not a good choice for the tension side of any bow. Curly maple is cut through grain. Thats what gives its beauty but very little integrity. You would do better with the hickory for a back.

[vinemaplebows]

Unless you cut that curly maple quarter cut...it was doomed from the begining. Curly maple when planed will have violated grain. I will be trying the same thing very soon, and expect it might explode...but what the heck, if it makes it it would be cool!

VMB

[warpath]

Longbow Steve is right. Curly maple without the benefit of glass normally doesn't stand a chance. I did make a boo backed curly maple bow awhile ago and it took me 5 attempts to get it right. Still only came out to about 40#'s. Don't trust it enough to sell or trade it, but it is fun to shoot. Hickory backing would've been better with a 3/16" curly maple belly might have fared better. Would've kept the hickory core but made it the length of the bow instead of shorter as you described. Maybe even a veneer of curly maple on the belly for looks. It wouldn't be a functional part of the bow as far as adding any significant draw weight, but would achieve the look you were going for on the belly at least. Just my opinion.

  G

[JW_Halverson]

Probably the only thing with less integrity than the curly maple would be saltine cracker! 

Oh, man, but it must have been absolutely gorgeous until it blew into smithereens!

[DarkSoul]

Why did you switch from TiteBond 3 to G2 epoxy? I'm inclined to think that TiteBond3 would have been a better choice.
Did you tiller this bow at all? Or did you just glue it together and expected the tiller to just be magically perfect? "Exercising the limbs" is NOT the same as tillering by any means.
If the bow broke at the handle fade, there's probably a fault in the taper of that handle. It needs to have an absolute feather taper. Very gradually tapering to translucent.
As said, curly maple makes a very bad backing. Put the hickory on the back.

Post some pictures of the casualty. We all break bows - nothing terrible. Try to learn from your mistakes.

[mnviking]

yep  I am thinking about putting glass over the maple on the next try as the wood was really great looking and the limb reaction really seems great as well. 
thanks for your thoughts

[mnviking]

I have attached a photo of the limb fracture.

I switched to g2 epoxy vs titebond III just to test it as it has twice the tensile strength of tb III-  just an experiment.  the wood  started to fracture at the hickory taper end which was next to another interior hickory layer.  the outside layers were the curly maple.


I guess i will try this again with some glass and no interior taper but I sure liked the limb action with the original layout.

as far as the tillering I thought the bow tiller looked good before I started exercising the limbs. 

thanks

[mnviking]

ok guys one more photo.  this photo shows the embedded handle .  you will see that the limb did not break at the handle taper but it broke about 8 inches further up the limb at the end of the internal hickory taper that was in the middle of all the laminates.

just a clarification as I led some to believe it broke at the end of the handle taper but it was about half way up the limb at the end of the internal tapered hickory strip.

I will let you know how the next bow turns out with a layer of glass as the outer layers.

this site has been very helpful

[Pat B]

If you do add glass, post the pics on "Around the Campfire". Glass is not allowed in the Bow section.

[mnviking]

ok Pat B
thanks
I assumed glass was a no-no in the primitive bow site but was not sure

I appreciate the heads up

[Pat B]

ALMOST anything is OK on Around the Campfire! 

[BowEd]

Except polotics and religion.