Poplar Joints seperating - Woodworking Talk - Woodworkers Forum
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post #1 of 22 Old 05-12-2013, 04:11 PM Thread Starter
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Poplar Joints seperating

Hello,
I am a set (movies/commercial/theatrical) builder that recently started taking on more advanced woodworking projects and have just run into a problem.
A few months back I built a "plank" style bed platform for my friend and his wife. I used 5/4 poplar (for budget and because I like the way to wood looks). The boards are approx. 6' long and they were biscuit joined and glued evenly with titebond and clamped for a weekend. There are roughly 9 boards (varying widths). I live in Los Angeles and built the bed here and delivered it to them in Bakersfield about three months ago. The other day my friend sent me a photo of a crack (1/8" wide at least 18" long) along a seam and said there was one more that bad and some hairline cracks on other seams.
My plan is to go up and re-glue and clamp the seams, but I'm not sure how useful this will be as I was sure that my initial glue and clamping was adequate. I know Poplar is relatively soft and that the temperature change in Bakersfield is significant, but is there something I can do to prevent the cracks from coming back once re glued and clamped? A different glue perhaps? maybe additional bracing underneath or pocket screws from underneath?
As you can see I have access to a lot of tools and working knowledge of them but my specialty lies in temporary structures and faux finishes for the sake of entertainment.
Any help would be greatly appreciated!

-Buddy
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post #2 of 22 Old 05-12-2013, 05:45 PM
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It is not likely the glue. It is more likely the wood you purchased had higher moisture content than the eventual location.

Did you purchase from a big box store? Their Kiln Dry lumber is perhaps 15% at best.

You perhaps needed to let the wood reach equilibrium at your location before constructing the bed.

When the wood has moisture change it will "move" is the term we woodworkers call the change in dimension as wood absorbs or looses moisture. Most of the change is at right angles to the grain, so normally in the width of a board. Very little change parallel to the grain.

If the joints were good at the time of the initial gluing, I would have expect the wood to crack somewhere other than the seam. Yellow glue, like Titebond I, II or III and good joints with no gap prior to gluing is normally stronger than the surrounding wood.

If you attempt to re-glue and force the boards back by clamping you will have a joint with a lot of stress and it will likely fail again.

It will be best to rip the boards apart, re-joint the edges so that they are all straight, and then re-glue. The wood at this point should have reached equilibrium with the new location.

Sorry, I expect you wanted an easy fix. I do not think this is an easy fix.
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post #3 of 22 Old 05-12-2013, 05:45 PM
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Post a pic, so we can see the construction and the cracks.

Off hand sounds as if the lumber was not dried properly.

Pure mathematics is, in it's way, the poetry of logical ideas. - Albert Einstein.
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post #4 of 22 Old 05-12-2013, 06:31 PM Thread Starter
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Yeah, I was afraid that ripping it apart and re joining would be the best solution. I'm surprised that it retained so much moisture as I was working on this over the course of a month or so in my set shop.
The hardest part of this that its far away from my shop and I dont think working on it in Bakersfield will be an option. I will have to cut it into smaller pieces and bring it back down to LA then re build/ re finish it (UGH)
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post #5 of 22 Old 05-12-2013, 07:31 PM
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If you have a jointer plane or a flush trim router bit, you can rip the offending joints apart and joint them on site with one of the two methods.

If you putt the joints together with pocket screws, it will be solid an especially if your jointing was close and you used NEW TB III glue.
The poorly dried wood or old glue may have caused the failure.
Another thing to consider is how close the boards that failed were to the center of the tree. If the end grown rings are very arched, the boards may have warped then put extra pressure on the joints. As mentioned, if you check the failure line it should have pulled fibres off the other side unless the glue itself failed. Any boards within 4-6 inches of the center are too close and need to be culled and used in other than a panel glue up.
Hope it works.
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post #6 of 22 Old 05-12-2013, 07:35 PM
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I suspect that there is another problem at work than moisture content at time of glue-up. Are the ends of the glued-up panel captured so that the panel can not float? If not and it only separated at the glue lines than it sounds like a glue starved joint, either not enough glue was used or too much clamping pressure was used or the boards were not jointed and pulled together with the clamps. Also PVA glue does not glue to itself, so you would have to use either epoxy or rip and re-joint the boards.
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post #7 of 22 Old 05-12-2013, 07:47 PM
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Kieth makes a good point. You can't fix(screw) a panel down other than about a 4 inch area usually in the middle to allow the ends to move in and out. The fibres should be pulled off at the failure sites if the glue up was good.
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post #8 of 22 Old 05-13-2013, 08:47 AM
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Quote:
Originally Posted by Keith Mathewson View Post
I suspect that there is another problem at work than moisture content at time of glue-up.
+1
Very unusual failure, would love to see a picture of how this was put together.

Pure mathematics is, in it's way, the poetry of logical ideas. - Albert Einstein.
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post #9 of 22 Old 05-13-2013, 10:16 AM Thread Starter
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Thanks everyone for the guidance. I will be going up to Bakersfield this Thursday to assess and try a fix (ripping and re jointing probably). I only have a crummy cell phone pic from my friend that shows one crack, I will post photos when I get there. Apparently there are two "large" cracks. One on the left side of the bed and one on the right. The interesting thing is that they are on the "front"/"back" of the same board so I guess the opposing joints.
That one board that the joints are separating from I assume is moving a lot.
As mentioned I will try to get pictures as soon as possible.
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post #10 of 22 Old 05-13-2013, 10:57 AM
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I'd like to see a picture too... but dare I say the issue is biscuits... biscuits are no good, for that matter neither are pocket screws! Come on fella's the guy intends to build FURNITURE. He is going to want to learn joinery - not crackerjack crap.

How how wide is the jointed edge we are talking about here? I use to rub elbows with some of your IATSI brothers as a set medic down here in Holly Wood South, a couple had furniture back grounds - are none of the other guys on your crew familiar with traditional joinery?

Pictures would be a big help.
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post #11 of 22 Old 05-13-2013, 09:46 PM
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Firemedic,

I'm afraid you are way off base here. Biscuits have nothing to do with how well an edge joint performs and pocket screws can work very effectively as a clamping method on in this type of application.
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post #12 of 22 Old 05-14-2013, 12:05 AM
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We had rain last week with temps in the 60s.Today we saw temps in the 100s across so California.Bakersfield is not that far from me.Most likely bad timing for your project.i feel for ya the past few day I been working on some night stands.So during the day I can hear wood popping and cracking.I usually try to finish my fine woodworking before summer.Summer time is for building gate and decks.
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post #13 of 22 Old 05-14-2013, 12:39 AM
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Well guys, I don't know why biscuits get such a bad rap and IMHO and those at Fine Woodworking. Biscuits do add strength to a joint. In fact It's better than a dowel in a lot of ways. There is a time to use them and a time not too.

Almost any two boards will glue edge to edge with plane ole yellow glue. I remember when Tight Bond was invented. Before that we used white Elmer's glue.

If I had to guess I would guess not enough glue, too much clamp pressure.

Al

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post #14 of 22 Old 05-14-2013, 10:37 PM
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Fire medic are you out of the closet as a woodworking snob?.

A repair job sometimes calls for repair tools.
Biscuits or splines have their place in joinery but not particularly in side to side panel glue ups. They can be useful there for registration of surfaces but don't add strength. The can add strength in T joints like a leg to apron though not as good as a good M&T joint.
Pocket screws look unatractive from the wrong side but can be a good way to fix and hold a side to side glue up while the glue set. They can be removed the next day.
They should NOT be needed in a conventional well jointed panel glue up.
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post #15 of 22 Old 05-14-2013, 11:23 PM
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People always start to quiver with anger when I denounce their beloved pocket screws and biscuits!

It is NOT "joinery." Never has been and never will be. Biscuits and pocket screws are used by two people - those who don't know better and those who don't care to know better.

It's tough for someone new to building furniture to see through all the gimmicks out there, I totally get that. Fine woodworking and several other extol the virtues of pockets screws for one reason and one alone - Kregg keeps their lights turned on.

Modern woodworking publications are about advertisements not learning. Even good ole Norm only had one agenda - convince you that you need a new tool he is pushing that week. It's a business just like anything else. It's marketing. If I use this tool on my show XYZ will pay me for a product placement AND pay for advertisements in my catalogue - that's right, it's no longer a magazine.

Am I a snob? I don't think so...? I buy vintage (cheap) tools and put sweat equity into them. I saw my own lumber. I don't think that I'm the best cabinetewright to walk the earth. So no, I don't think I'm a snob.

On the flip side I believe in REAL joinery that, low and behold, actually classifies as JOINERY. I happen to know that biscuits are only useful for plywood and pocket screws are a nice way of saying I'm too lazy to do it right - in a way that will last. I know that Walmart China crap that people call "furniture" be it made in China or the guy down the street is in fact crap. So if THAT makes me a snob then sure I guess I am.

So someone, anyone tell me why anyone in their right mind would substitute biscuits for a M&T. Who in their right mind would be so ignorant to think that pocket screws actually last? Tell me who believes that furniture that is "hand built" should be just as disposable as a piece from Big Lots department store. And tell me what happened to a sense of pride in your work too. Tell me if you think your furniture will still be around 200 years from now.

"But they are so fast... and cheap... And they require little to no skill to use!" I get all that - I do. But It's a disservice to speak to a guy interested in building FURNITURE not cabinets as if those were actually valid methods.

Let the fist pounding and angry rants begin - I won't be around to read em. Apparently we need a section on cardboard furniture.

Last edited by firemedic; 05-15-2013 at 08:25 AM.
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post #16 of 22 Old 05-14-2013, 11:39 PM
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Quote:
Originally Posted by Midlandbob
Fire medic are you out of the closet as a woodworking snob?.

A repair job sometimes calls for repair tools.
Biscuits or splines have their place in joinery but not particularly in side to side panel glue ups. They can be useful there for registration of surfaces but don't add strength. The can add strength in T joints like a leg to apron though not as good as a good M&T joint.
Pocket screws look unatractive from the wrong side but can be a good way to fix and hold a side to side glue up while the glue set. They can be removed the next day.
They should NOT be needed in a conventional well jointed panel glue up.
I'm a snob too, of a different kind than Firemedic. But let's face facts. Most woodworkers and handy guys are snobs in one way or another. Our work is personal and we take it serious. To be a good snob the first step is knowing your a snob. We don't really think we're the best but we sure come off like we do. We think in absolutes more than most people. We think there are good reasons to believe, "some things are just not done". Like admitting you voted for Jimmy Carter and using those stupid looking "no-sand wood plugs" to cover a screw. It's just not done!

But there are reasons to enjoy the woodworking snob. You can glean a lot of good info and advice from one when it may be important. And if you sell upper end stuff, they are a great source for income.

For those who are not I would say good for you. I can envy you. Well, until you do something, "that's just not done". :)

FireMedic, It takes one to know one.

Al

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post #17 of 22 Old 05-15-2013, 08:16 PM
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While your passion is commendable lets not get too far afield. What the OP asked was about edge glueing and in that respect biscuits and pocket screws work well. The biscuits do nothing to improve the quality of the edge joint but may help in alinement. The Pocket screws act as a series of clamps and again add nothing to the edge joint. The final result is in fact joinery just not applied in a manner you may approve of.
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post #18 of 22 Old 05-15-2013, 09:15 PM
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Quote:
Originally Posted by Keith Mathewson
While your passion is commendable lets not get too far afield. What the OP asked was about edge glueing and in that respect biscuits and pocket screws work well. The biscuits do nothing to improve the quality of the edge joint but may help in alinement. The Pocket screws act as a series of clamps and again add nothing to the edge joint. The final result is in fact joinery just not applied in a manner you may approve of.
I have to disagree with regards to biscuits. They do add a great deal of strength and the brand I use, Porter Cable. Do not aid in alignment. The PC cutter cuts a wider grove than the biscuit. It has wiggle room. after the biscuit swells from the glue it does fit tight.

While I don't have a Kreg jig I do believe the ugly things add strength. Any screw adds strength.

Al

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post #19 of 22 Old 05-15-2013, 09:30 PM
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This reminds me of a conversation I once had with a structural engineer I was required to hire to certify a complex curved stair I built. In the course of answering his questions about construction methods he was perplexed about the use of glued wedges and the riser-to-tread glued edged joints. But his face brighten when I explained I used pocket screws to act as clamps to hold the joint closed while the glue dried. He wanted to know the size and spacing of the screws. I told him the screws did nothing and could just as well be removed after the glue set, there is a few hundred years of stairbuilding to support this. Apparently there is a lot of information about screw strength but not as much understanding about glued edge joints.
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post #20 of 22 Old 05-15-2013, 09:44 PM
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Quote:
Originally Posted by Keith Mathewson
This reminds me of a conversation I once had with a structural engineer I was required to hire to certify a complex curved stair I built. In the course of answering his questions about construction methods he was perplexed about the use of glued wedges and the riser-to-tread glued edged joints. But his face brighten when I explained I used pocket screws to act as clamps to hold the joint closed while the glue dried. He wanted to know the size and spacing of the screws. I told him the screws did nothing and could just as well be removed after the glue set, there is a few hundred years of stairbuilding to support this. Apparently there is a lot of information about screw strength but not as much understanding about glued edge joints.
Well if you stress the joint glued at 90 degrees. Having a screw in the joint will in fact strengthen the joint.

Al

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