Warbird Information Exchange

Me to! The sheet river queens always love you long time with a peso on your forehead.

Now I'll be having nightmares after thinking about where that peso was hiding

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Don't touch my junk!!

I know it's been a couple of days since the last update, so I thought I'd let y'all follow along while I make one of those "simple" little projects that I just completed.......

As y'all know, the local EAA Chapter is graciously taking on the chore of recovering our control surfaces for the B-24. They are nearly ready for the recovering process to begin on the elevators & rudders, but were waiting on me to repair one of the elevators first. So, this morning, I went ahead and knocked that out for them.

The elevator had actually been repaired by someone years ago, but was cracking through the former repair, as you can see in the photo......





The first step in this process was to drill out the rivets that held the old patch into place.......



One of the reasons that the old patch cracked was that it simply wasn't strong enough to do the job. Much of the metal on these control surfaces is made out of .025" thick aluminum, or more commonly known as "oh-too-thin." Although the previous patch was made moderately well, it needed a duplicate piece riveted to it underneath the damaged skin, as well as on top. Here's what it looked like when the old patch was removed......



So the next step was to start fabricating two new patches in order to make this repair. The first step was to get a peice of .025" aluminum and trace out the pattern of the old repair. But since the patch requires a 90 degree bend in it, I needed to mark where the bend was going to be before I traced the rest of it........





Once traced, I then went over to the shear and cut the sheet down to the pattern lines.......



Then it was over to the bandsaw to cut out the excess material. Notice how I used relief cuts to allow the bandsaw blade to make the corner more smoothly........





Once both pieces were cut out with the bandsaw, our quality assurance inspector insisted on coming by to give them a "cat-scan." .......



Once the "inspector" and I argued over who was more qualified to do this job, I was allowed to continue and smoothed out the radiuses of the new pieces with the flap wheel on the die grinder..........





Then, it was time to make the 90 degree bends with the sheet metal brake. I didn't know if everyone knew how this worked, so here are some basic details. First, you put the sheet in the brake and clamp down on your marks.........







Then you pull the handle upwards on the brake to make the bend. With this thin material, there is little chance of cracking with a bend such as this. However, with thicker materials, you must be careful to insure you have the proper bend radius, or it will crack and you'll have to start all over........





And here's the bent piece........





When marking the bend for the bottom piece, I needed to account for it's location being slightly different, due to the original elevator skin being the "meat" in a "repair sandwich." Since this is such thin material, the mark I made was only about .025" or so past where the top piece's bend was..........



Oh, and just in case anyone is wondering how I'm going to recognize the top piece from the bottom piece since the two bend radiuses are so close together...I made sure I marked the bottom piece with a different color of marker (green in this case). Later on, when primed, I used a center punch to make a discreet mark.........



So now that the two new pieces are fabricated, it's time to start drilling holes. The first holes are made by clamping the piece to the elevator by using a recently donated sheet metal clamp (thanks for that by the way ), and then drilling a hole or two for the clecos to attach to....





Oh, and just in case any of you reading this are wondering what these clecos are and what they do exactly, here is a real quick example of how they work. As an example for you, I have the cleco pliers, a cleco (for a #40 hole that a #3 rivet will go in), and two scrap pieces with a #40 hole in them.........



In order to install a cleco, you just put it in the pliers and squeeze.......



To make the cleco hold onto something, you simply release the tension on the pliers and the spring inside will pull everything together.........



And here's an example with the two pieces of aluminum.........





Okay, so enough of that. Back to the project at hand.

Once the top piece had all of it's holes drilled, it was time to simply duplicate the hole pattern on the bottom piece. This was simply done by clamping it all together and then getting the clecos installed once a few holes were drilled. I'm not too crazy about the sloppy rivet pattern here, but I was kind of married to it since that's how the old repair was done....







Once all of the drilling was done, I had to deburr all of the holes.........



Then I shot some zinc chromate primer on all of the pieces of this "sandwich" and clecoed them all together while still wet. This will help create a moisture barrier that will ward off any corrosion in the future.....



Then it was just a matter of squeezing the rivets in place with the rivet squeezer.........



And with one more coat of primer just for good measure, this repair is completed. The elevator will get primed completely before it's covered with fabric........





So there you have it. One simple repair. Total construction time...approximately 2.5 hours.

I'm not sure what I'm going to go after next. We'll just have to see what the next update brings us, huh?

Gary

Thanks for the update Gary and glad to see your furry four-legged "inspector" approving of your work.

John

Gary, which way was the grain in the aluminum going?

It wouldn't matter too much on this part as it is not "structural" but the grain appeared to be going along the bend.

Good eye, King. On these pieces, the bend did go with the grain, rather than against it. It just worked out that it would only work that way with the piece of sheet I found to do this and I was too lazy to cut up a brand new sheet for this repair. However, with .025" and the radius that was used, there was really no issue of cracking. There is no doubt that I consider the grain when making bends in aluminum, particularly with thicker parts and sharper radiuses.

Again, good eye. I see that I have to reeeeealy watch myself with what I do, since it's obvious y'all are keeping a close eye on it.

Gary

I'm not looking for your mistakes by any means. This is one of my pet peaves and I am astounded on how many people don't know how to set the grain for a particular part.

Oh, I know you're not looking for mistakes. That was a good point about the grain vs. the bend. I should've mentioned it in my update. It's input like yours that helps make this an informative thread for everyone.

On another note about bending aluminum vs. the grain of the sheet.....the only other time I could think where it's not particularly important is when you're using "0" (non-heat treated) aluminum. I'm sure that if you crunched the numbers, going against the grain would be stronger than with the grain, but it's soft material, which makes it more pliable. You will see an example of this in my very next update.

Thanks again for your input, King. Your thoughts are just as important to read as mine.

Gary

Oh, I know you're not looking for mistakes. That was a good point about the grain vs. the bend. I should've mentioned it in my update. It's input like yours that helps make this an informative thread for everyone.

On another note about bending aluminum vs. the grain of the sheet.....the only other time I could think where it's not particularly important is when you're using "0" (non-heat treated) aluminum. I'm sure that if you crunched the numbers, going against the grain would be stronger than with the grain, but it's soft material, which makes it more pliable. You will see an example of this in my very next update.

Thanks again for your input, King. Everyone elses thoughts on WIX are just as important to read as mine.

Gary

Good Catch King!!!!

Well I do design parts and repairs for aircraft all day long.

Okay, I thought I'd start this next update with an old picture. Its a blown up and expanded copy of a copy of a duplicate of a copy. But it's all I have to work with when trying to fabricate the tracks for the tailgunner's sliding doors.

If you look at the upper, R/H side of the picture, and look closely at the little joggle in the track, that's the only reference I have for building this thing.........



Sooooo, I'm sure you can imagine that I've been losing some sleep over how I'm gonna make this work. There is also a fair amount of imagination needed when designing something like this. But, so far, it's actually going fairly well. I found some .080" non-heat treated (soft) aluminum that was going to work out pretty well for this project since I needed to do a fair amount of stretching and shrinking with it. I got lucky in the fact that the sheet that I found was exactly the right length for this project. So I sheared off the width I needed for the first piece of track and put it in the sheet metal brake.

I need to note that due to the length only being right in one direction, this piece had to be bent with the grain, not against it. In reference to my earlier post, this isn't a big issue in the fact that the material is soft (non-heat treated) and cracking around the edges of the radius did not happen....





Once I had my first angle made, it was time to start shrinking the material to make the bends needed........





Now that the angle was shrunk the amount needed, I had to stretch it the other way.......





You can get a better idea of what I was going after with this picture. It's starting to look like the old original photo to me.............



The next step was to get the aft portion of the angle shrunk around to the same radius as the tailcone. There's lots of back and forth and up and down the ladder from the shrinker to the airplane at this stage. But it eventually comes to shape.......



Once I was happy with the shape of the angle, I needed to sand and polish the teeth marks out of it that the shrinker and stretcher made. First with the sanding disc, then the Scotch Brite disc, then finally the polishing disc.......



And finally, you can get a good idea where I'm going with this........





There is a ton more work to do with this piece, but I've had enough for today. I'll get back on this project tomorrow and will hopefully have more to update for you regarding this little project.

Gary

Hi Gary,

Great work on Lil. I was just wondering if there is plans for more reinforcement on the newly-fabricated tailcone. It looks like it is only being held on by the rivets, and it seems to me that to be a viable mount for a gun and various other paraphernalia would necessitate some more reinforcement. I'm sure there is still much more work to be done, this was just something I noticed from looking at the photos.

-WC

Gary,

Quick question on control surfaces.....

Since you're recovering, does it make sense (or have you already decided) to paint them before recovering to protect against corrosion? Does it matter with control surfaces that will be covered to paint them before hand?

Curious in Virginia

Gary, Does it take a lot of extra for you to make all these photos and answer all the questions on this forum, or are you makeing a record anyway? Great work either way. I know something about engines, but not sheet metal and it seemS like art as much as mecanical to watch you make stuff. Is that cat a tough as a BKD cat; can it catch rattlesnakes?

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Bill Greenwood
Spitfire N308WK