I've got the bamboo backing blues

[Gordon]

Well, I just broke my 3rd bow in a row due to a backing failure. I'm not sure if there is a problem, or I'm just on an extraordinary run of bad luck. At any rate, this is starting to get old...

[Blacktail]

i think you need a good pick me up... of vine maple..john

[Tom Leemans]

Got pics?

[Rich Saffold]

Gordon,

Lemme guess 4+month old Urac, and/or the work shop is around 60 degrees... Or sometimes batches of bamboos aren't what they seem to be quality wise..

I feel your pain, and when you have your skills this only amplifies it.. I know it can be figured out. I get a fair amount of phone calls with folks in a similar funk and can usually get them straightened out in a laminating kind of way..

Rich

[Gordon]

Rich,

The Urac glue is new and I've sucessfully made several bows from the same batch of bamboo. But my workshop is probably around 60 degrees. I didn't think that would make a difference if you cured the glue-up in a warm place though. Is that an issue?

Gordon

[makenzie71]

Why do you think it's backing failure?  The only reason I'm asking is the only failures I've had, when it comes to bamboo, have been because the boo crushed the belly...something that actually happened to me this very day.

[Gordon]

Why do you think it's backing failure?

The last two failures had a large splinter lift up from the bamboo backing. I did not see any evidence of compression stress on the belly (both of which were Ipe).

[makenzie71]

Did it lift at a node or a damaged area?  Not calling your bluff...I just never had splinters lift on bamboo myself.

[M-P]

You've got my sympathies.   I've read enough of your posts to believe that you're probably a better bowyer, so I won't even try to guess what's going wrong.   Ron

[medicinewheel]

Maaaaan Gordon, really sorry to hear that!
Do you do any tempering on your bamboo before glueing??

[Gordon]

The first failure I believe was due to an improperly implemented powerlam and the limb broke between nodes. The second failure was a splinter that lifed about 1/2 inch from a node - I think I may have made the bamboo too thin in that spot to withstand the high draw weight. The final failure, and the most heart-breaking, was a splinter that started very close to a node. Perhaps I got too agressive when I took off the rind and smoothed off the node, I don't know...

Frank, I did not temper any of the bamboo.

[Granite Mtn]

I have had failures exactly like yours,  with all kinds of bamboo, ie Franks in Ca., Bamboo and Ratan works east coast, and the tonkin bamboo from Dryad Bows.  Dean has ways of patching splinters with silk, and has alluded to selfbows being more dependable in some of his writings.  I trust bamboo backed bows for extended hunts in remote areas only if I can take a spare selfbow.  If I can take only one bow it is a selfbow or sinew backed.  I know this will not be everyones opinion but most will agree a well made selfbow is simply the most dependable.

hope this helps
Chris

[artcher1]

It's just a run of bad luck I think Gordon. Unless you harvest the stuff yourself you're at the mercy of those that do. I've found hickory backing to be the same.

I've had many boo backings fail to no fault of my own. Curious thing though, they all failed on the upper portion of the stalk/upper limb. I build everything as it "stands on it own" and 99.9% of the time it's always  the upper limb that fails. Whether backed boos or staves.

If I ever do build anymore boo backed bows it'll be with two lower sections of the stalk/backing and spliced 'em in the handle.

Can you tell us at which end of the backing is failing (as it stands in the stalk)? ART

[Rich Saffold]

Gordon,

The splinters lifting might be from the bamboo getting a little too dry somewhere between the field and the bow. Often heaters run during cold weather will cause splinters to lift. This I have learned from sending bows to the cold regions where the heaters get the mc% in the house too low for what bamboo can handle..

They may have been helped by getting it a little thin and removing the rind..I stopped removing rinds because of the problems its caused even though I like how it looks.

Since bamboo is really a "grass" its not as tough in this sense as one might think..

If you were getting separation on the glue line then it might be a glue issue, but I think you are fine there..

I hope this helps, and trying bows with thicker bamboo backings was influenced by my desire to get as consistent on these as possible.

Rich

[Dano]

For what its worth, I have never removed the rind, and have never had one break, but I've only done a half a dozen or so.  I also leave the nodes proud.