Got A Bit Of A Surprise Today

[Jim Frye]

Our new home was built in 2015 and all of the wood trim was factory finished to our specifications. The interior woodwork has been great, but the bottom of one window picture frame trim suddenly bowed out in the middle and could not be forced back and stay put. So I pulled it off and removed the 1 1/4" brads that held the trim on. Further examination showed the piece of trim was a wee bit too long and the finish carpenter just wedged it in place and nailed it in place. It took ten years for the brads to lose their grip on things, and the piece is bowed. The surprise came when I could see the back of the board. It was labeled "made in Chile with sustainable wood". I'm not sure what the species is, but it's fairly hard and straight grained. I think it looks like Alder, but who knows. I have the board clamped to my assembly table and have been wetting the unfinished side with wet water to see if the bow can be removed or reduced before I refit the piece back in place with longer brads.

[leehljp]

I have been guilty of doing similar only to be shown up later. It might seem like a "no brainer" wedging a board in - in certain situations but wood moves!

I don't know why this reminds me of chuck Yeager story. Some of the F-104s crashed and others had no problems. They could not figure it out. Yeager was flying the 104 fairly high and experienced the same malfunction that the others had that died in crashes. Yeager managed to get the plane upright and get the plane down. Upon examining the stabilizer, they noticed a bolt in wrong. It was supposed to be installed from the bottom up due to clearance issues. But the one on Yeager's plane was installed top down with the nut on the underside instead of top side.

They went to the factory and the line that installed the bolt wrong. The long time senior plane mechanic was asked about that and he said something along this line: "No one installs bolts bottom up! I have never seen that before!" They told him the need to install it bottom upward with the nut on top. That change made the clearance on the stabilizer pivot mere millimeters, where as top down had caused jamming on the stabilizer and caused a few deaths. They never did tell the mechanic what it had cost, but he did change the way he installed them.

What seems like normal work can cause problems down the road!

[LCHIEN]

I hope that's not a true story. Every assembler, whether senior mechanic or apprentice, whether its an experimental fighter jet or a kids toy tricycle, must put together things according to the designing engineer's blue prints, drawings and instructions.

His experience should not override the Designing engineer's authority. Most engineering drawings that are any good have an exploded diagram with parts callouts, and the order of assembly with nuts and lock washers etc is clearly indicated including the side the bolt is inserted from.
The engineer should not have to indicate on a particular part that an assembly as shown is life-critical but that everything else on the page you can assemble any way you feel is better than what the engineer wants.
If a senior tech or mechanic feels a design is in error, he should bring it up to his superiors. But not change stuff on his own accord. He should have been fired on the spot.
Such behavior, I hope would be rewarded with immediate dismissal rather than a gentle admonition (how did he ever become a long time senior mechanic when he willfully defies blue prints???) Such behavior costing lives and billions in lost time and aircraft? The very first thing taught an assembler is to MAKE IT LIKE THE PRINT.

As far as the aircraft goes. Some had crashed? More than one? For the same apparent problem? In all aircraft especially new ones but even old designs, they ground the aircraft until they are convinced that they have solved the problem.

[Jim Frye]

My Pennsylvania Dutch Grandmother's old saying comes to mind. "The hurrier I go, the behinder I get".

[Jim Frye]

Well, that didn't work, and I should have known that clamping the piece flat wouldn't take the bow out. That's what I get for not thinking things through before plunging ahead (or back). The piece of trim is just over 48" long and has a good 1/2" bow in the middle. I now have it clamped to the table at each end with a 3/4" spacer underneath in the middle to hopefully overcome the defect. I also have six layers of paper towels on top to keep the wood wet longer. I have a painting project starting that will occupy at least two days, so we'll see what things look like after that.

[Jim Frye]

Update: It took longer than expected, but I finally got the trim piece flat. First pass actually gave the piece an opposite bow, so I had to reverse that mistake. The second try left the trim with lesser bow in the original direction, so try number three was done to a smaller amount and it finally came out flat. I applied a couple of applications of mineral oil to the unfinished side and let it cure overnight with a fan blowing on it. Then I shaved the end miters until the piece fit with no bowing. I fired up the compressor and nailed the trim back on with 1 5/8" 18 ga. brads to replace the original 1 1/4" ones the finish carpenter used. A bit of Color Putty was used to fill the brad holes.

[Koryffertz]

Update: It took longer than expected, but I finally got the trim piece flat. First pass actually gave the piece an opposite bow, so I had to reverse that mistake. The second try left the trim with lesser bow in the original direction, so try number three was done to a smaller amount and it finally came out flat. I applied a couple of applications of mineral oil to the unfinished side and let it cure overnight with a fan blowing on it. Then I shaved the end miters until the piece fit with no bowing. I fired up the compressor and nailed the trim back on with 1 5/8" 18 ga brads to replace the original 1 1/4" ones the finish carpenter used. A bit of Color Putty was used to fill the brad holes.

It is perfectly normal for the trim to warp in different directions after each adjustment, as wood reacts to moisture and bending forces, so it is necessary to work in small steps as you do to get a truly flat result. It is also wise to apply mineral oil and let it dry overnight before reinstalling, allowing the wood to stabilize before fixing it with longer nails to limit rewarping.