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Author Topic: Lessons learned BBO failure  (Read 4918 times)

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Offline lesken2011

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Lessons learned BBO failure
« on: September 02, 2012, 10:57:11 pm »
I thought I would share another failure with you guys in hopes that it might save you from making a similar mistake. I have been working on a bamboo backed osage over the last couple of months on and off. Just so you'll know, I have a hard time pulling the trigger on starting a bow, sometimes. I try to plan it out in my mind, sometimes for weeks before I actually start one. Usually after a while I realize it is not going to make itself and I plunge in. In spite of all the mental preparation, I still find ways to screw up. In this case of this bow, the first mistake I made was left the the bamboo too thick. I didn't realized it till I got close to the final tiller. Near the tips there was as much bamboo as osage. In the past, most of my backed whitewood bows have held up. I had a bamboo backed ipe fail at the glue line and today this one did the same thing. In addition to both being heavy dense woods and bamboo, they were both glued with some reflex and failed at the reflex point. Here are a couple of pics...on the tiller tree with the long string



After bracing at about 2 inches.

As you can see, I had already added a purple heart handle and tip overlays... here is a pic shortly after the above pic...



a close up of the failed glue line

To some it all up my white wood glue ups with non-stressed designs I have never had a delamination, but on reflexed designs which have both involved bamboo and dense woods, I have had problems with the titebond products. My next glue up will be a test of Weldwood Plastic Resin which is a urea formaldehyde glue similar to Pro-glue or Resorcinol. I will keep you posted.
« Last Edit: January 01, 2019, 10:20:53 am by lesken2011 »
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Kenny from Mississippi, USA

Offline soy

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Re: Lessons learned
« Reply #1 on: September 02, 2012, 11:25:37 pm »
Man that stinks >:( i just started on a boo ipe....kinda worried a out the boo being to thin, it looks like it was glued with urac
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Offline Pat B

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Re: Lessons learned BBO failure
« Reply #2 on: September 03, 2012, 12:28:41 am »
That looks to me like the core broke along a short grain line running through the limb. When it failed and bent the boo delaminated.
  I've used Weldwood Plastic Resin with good results on boo and hickory backed osage and ipe bows with no glue failuse. I've never had a glue failure with TB or Elmers glues either.
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Offline lesken2011

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Re: Lessons learned BBO failure
« Reply #3 on: September 03, 2012, 10:18:48 am »
Could be, Pat, but this happened in the same spot on the bbi I made too. Right at the point where I glued in some reflex. My flat glue ups have all held. It just so happens that they were all hickory backed and all with TB2 & 3. I have recently read up alot on the various glues and one of the disadvantages of the pva glues like the titebond products is glue creep. Maybe the creep in the reflexed area of the limb creeps eventually leading to failure? Have you ever glued in some reflex in yours? These only had about an inch of reflex at glue up.
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For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast.

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Kenny from Mississippi, USA

Offline Pat B

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Re: Lessons learned BBO failure
« Reply #4 on: September 03, 2012, 10:21:43 am »
At least with the PVA glues you can heat the bow and the glue will release allowing you to reuse the backing strip.
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Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline lesken2011

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Re: Lessons learned BBO failure
« Reply #5 on: September 03, 2012, 10:25:35 am »
I hadn't thought about that, Pat. Decisions, decisions. Thanks for the feedback!!
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For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast.

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Kenny from Mississippi, USA

Offline Pat B

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Re: Lessons learned BBO failure
« Reply #6 on: September 03, 2012, 12:02:45 pm »
At 150deg(F) TB glues release.I have done this a few times. I start at the tip and once hot I slide a wood chisel between the backing and core and work it down to the handle heating as you go. Them start at the other tip and do the same. All thats need now is to sand the glue off the backing and use it again.
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Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline bowhntineverythingnh03743

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Re: Lessons learned BBO failure
« Reply #7 on: September 04, 2012, 08:56:11 am »
I have made two BBO bows now and use the URAC 185 glue... 13 grains powder to 100 grains resin.... No issue so far. I use 6 inch end blocks with a 3 inch middle block to add reflex into the bow. You will have to thin the osage slats from grip to tips about an 1/8 inch. No issue so far. Here is my thread of a build along with my frist BBO bow...

Maybe my mistakes will help you out!!

Justin

http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=007847;p=1
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Offline bobnewboy

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Re: Lessons learned BBO failure
« Reply #8 on: September 04, 2012, 10:01:22 am »
Hi Lesken,  this is a very interesting thread to me.  I have also just had a delamination failure (RATS!!!), in a hickory backed pau amarello ELB on the tiller at approx 15" drawn.  It was glued up with TB3 (first time I have ever used it), and had some glued in reflex to be absorbed by the belly taking some set during tillering.  I am always absolutely scrupulous about preparing glued joints, and this was no exception.  Both the glued surfaces were perfectly flat, freshly cleaned up with 80 grit paper and thoroughly cleaned with acetone.  The pieces were glued, bound with bicycle inner tubes, and left in a warm dry place for a week,  just as I always do.  The resulting glue line was really good and I was quite happy.

When the bow failed it wasn't too dramatic, because of the short drawn length, and the bend was nice and even immediately before it let go.  There was no warning at all.  On examining the backing (still completely intact - that is some tough wood) and the broken belly pieces, it just looks like a glue failure.  The glued surfaces are pretty clean with just a small amount of the yellow PA remaining on the hickory as tiny yellow marks in places.

I've made a dozen or more laminated bows of the same, similar and far more extreme profiles using a resourcinol two part glue without a single failure.  So I think that the small bottle of TB3 will stay on the shelf for other wood repairs from now on.

Pat its handy to know that the TB series glues can be undone with a heat gun.   I may be doing some of that this afternoon now  ;D
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Offline lesken2011

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Re: Lessons learned BBO failure
« Reply #9 on: September 04, 2012, 10:48:49 am »
Thanks Justin & Bob. I have heard that they are discontinuing the Urac. After researching the other glues I mentioned, I may try those first. Thanks for the tips and the build a long by Justin was very informative.
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For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast.

Ephesians 2:8-9

Kenny from Mississippi, USA

Offline tom sawyer

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Re: Lessons learned BBO failure
« Reply #10 on: September 04, 2012, 11:15:57 am »
When I heard you had a delam with both ipe and osage, I wondered if it was because you needed to clean the oil off the wood better before gluing.  Both of those are oily woods.  But I'd agree that it doesn't really look like your problem was delamination.  Getting a backing thin enough takes a lot of work and its kind of touchy.

I like resorcinol for my boo backed projects.
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Lennie
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Offline boughnut

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Re: Lessons learned BBO failure
« Reply #11 on: September 04, 2012, 11:43:59 am »
well I see a few problems.  the boo is defently to thick.  I get my boo thin thin thin with a .003 per inch taper before glue up.  so go much thinner.  my other suggestion is to trape the boo which it does not look like you did in the pictures but it is hard to tell.  Boo is a very strong backing and will crysal you belly if not trapped.  the only wood I have nown to not have any compresion poblems with untrapped boo is hickory.  Even though osage is a very strong compresion wood you still need to trap.  all this will take stress off the glue joint as well as the belly.  I only use urea type glues, like urac which is already off the market and unavailable unless some one has old stock which I do not suggest due to uracs short shelf life.  pro glue is my next go to glue.  if you use TB do not rough up your sufaces to much as it shrinks when it cures and will not fill up all the roughness.  if you do all these steps you will have a blooming success.

Hope this helps
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mikekeswick

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Re: Lessons learned BBO failure
« Reply #12 on: September 04, 2012, 02:16:23 pm »
Half / half backing belly is fine. Ideally you would want to thin the boo to help keep the crown lower. I like no more than an 1/8 thick at the tips.
If you used titebond 3 then it wasn't the glues fault! No need to switch glues. Titebond 3 is a very good glue even severely reflexed bows. I've done well over 100 glue-ups (many types of bows) with it and have never had a single failure.
To prepare your surfaces for use with titebond they really MUST mate perfectly. I use a drum sander with 80 grit to ensure perfect surfaces to the lams. Titebond will not fill gaps effectively and is not made to. It also does not like heavy clamping pressure. How did you induce the reflex? If you used a clamp to pull it in then thats your problem - a dry joint.
Resourcinol is also an excellent glue but the surfaces need preparing differently.
People often have a glue failure, then blame the glue and move onto another brand. The better option is to work out exactely why it failed. If you are struggling to figure it out then simply contact the technical staff at the manufacturer's. Also all glues have a spec sheet (rarely supplied!?) which it's a very good idea to get!
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Offline bubby

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Re: Lessons learned BBO failure
« Reply #13 on: September 04, 2012, 06:28:28 pm »
how are you clamping your glueup's, where you had failure's you may have starved the joint by too much presure or not had enough presure and had a gap, either way is bad news, Bub
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Offline tom sawyer

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Re: Lessons learned BBO failure
« Reply #14 on: September 04, 2012, 08:58:59 pm »
You typically score the belly and backing to make it nearly impossible to starve the joint.  I use a hacksaw blade.
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Lennie
Hannibal, MO
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