Okay, I had some second thoughts about making this post today as it pretty much ends up showing what a bad day I had with my fabrication process. However, after more consideration, I figured it's only right that y'all should continue to see the good AND the bad as the reconfiguration of this ol' clunker continues, and that there could possibly something to learn with this. The first part of the day went fairly well, but as the day went on, it started to turn ugly.
When I left off at the last update, I had just riveted on the framework to the outer skin for the waist gunner's door. I was thinking that the window frame was going to be the next step, but decided that I should make the upper angles for the outer frame first. These will help hold the door in it's proper shape and will be what the inside skin will attach to.
Due to time constraints, I decided to only make the straight portions of these angles. When the inside skin is screwed (or riveted) to these, the door will be quite strong, so the corner angles shouldn't be necessary. So the first step was to cut out a piece of bulb angle that I had laying around, to it's correct length for the first side....
It was obvious that I would need to stretch the angle a bit to conform to the correct radius for the door. So, as you should know by now, the first step is to place an index mark on the door and the angle, so that you go back to the same spot every time you check it for shape.....
Then off to the stretcher we go. It is crucial to remember that when stretching the metal, you MUST go slowly. You are essentially pulling the metal apart, so if you get over zealous, you'll crack the piece you're working with. Shrinking the metal isn't nearly as bad as stretching it, although, there is a point where the metal can only be "squeezed" so much before it cracks as well. So here's the angle on the stretcher. You can see that the curve is already starting to take shape.......
It looks like I need more stretching to get the curve I'm looking for. So I placed some red marks where the majority of the stretching needed to take place......
And believe it or not, I the part fit perfectly on the second attempt. It's better to be lucky than good, I reckon. So from here, I clamped the part in place and started drilling the rivet holes and clecoing the part in position...
The one outside frame angle needed a touch of trimming, so I took care of that at this time....
I then deburred all of the holes and clecoed the part back in place one more time....
It was really eating me up inside about how rough this door was looking, but I just don't have the time to make the little cosmetic fixes to it that I'd like. However, I did compromise a bit and polished out some of the "high spots" on the outer frame, where the shrinker marks were......
Then it was just a matter of riveting the frame into place...
Once I did that three more times, the outer frame angles were installed...
Now comes the fun part. Time to start on that inner window frame. I need this frame, not only to fair in the window when the door is complete, but it will also serve as a place for the inside skin to attach to and help with the rigidity of the structure. Now, I need to point out here that I realize this will look nothing like the original waistgunner's door that I'm currently borrowing, but after further review, I've noticed that the "A" model door is actually nothing like any of the other B-24 doors anyway. Figures, huh? Anyhow, I recall seeing in our drawings that we have (I'll have to dig them up later for the non-believers in the crowd, I'm sure), that the "A" model door is pretty much a squared off assembly, much like I ended up making anyway, after all of my other failed attempts at making the framework look like that late model door we have. Also, the later B-24 waistgunner positions were all lowered about 8" or so. This means that the contour of the door is different because of it's location on the fuselage. I confirmed this by trying to install the borrowed door we have on our airplane, and it simply will not work.
Okay, let's get back on track now. In order to make the inner frame, I needed to make my own angles (we're out of stock on everything else). I opted to use .040" 2024T3 material. It is quite strong (same heat treating that's used on the outer skins of the airplane) and is generally easy to work with. Like most everything else, it just starts with a flat sheet. I just picked out a sheet that was the length of our shear (too lazy to cut these by hand this time), and cut out three pieces, 2 1/2" tall. This will give me a half inch flange (minus the radius) when the angle is bent. Now, something to note here is that I was careful to cut these pieces of metal to where, when bent, the "grain" of the metal will be the same direction as the bend radius. It will be much less likely to crack and will retain it's strength this way.....
Now, since this metal is so thick, I needed to be careful with the bend radius and not make it too sharp, or cracking would occur. Since our sheet metal brake has no adjustment for radius, I just cheated by simply bending another piece of aluminum and putting it in the brake first. Then I just put the metal I'm using for my angles in underneath that to get a nice radius, with no cracking.........
So now that the angles were all made, I needed to start shrinking them to fit the window frame. I knew going into this that it was going to be a challenge, because of the tight radius of the window. This is why I chose such a small (1/2") flange in the angles I bent. The smaller the flange, the more it should tolerate shrinking without deformation. And naturally, the all important index mark was put in place, along with a tick mark for where the bending should be done........
Well, it didn't take long at all before I scrapped the first piece. I just tried to get too much shrinking done in one spot........
So, in the trash it goes............
I decided to keep trying with the other end of the angle....
Now this time, before things got too carried away, I decided to polish out some of the shrinking marks in the metal. The old saying of "a scratch is a potential crack," fits well in this scenario. If you polish out the marks left by the shrinker, you should be able to ask more from your metal. The first thing I did was to put some Boelube on my sanding disc. Then I rough sanded the marks off (inside and outside of the angle), followed by the polishing disc. The tricky part about this is that you don't want to take too much material off, as that just makes the metal weaker.......
This polishing allowed me to keep on shrinking the metal around to match the radius of the window frame. This picture shows that I'm juuuuuust not quite there.......
There. That's more like it...........
So, after trimming the bad end of that angle off, it was time to start the next piece........
I had started the bending and just polished the shrinker marks off, but it appears I must've taken too much material off when polishing and this happened when I went back to the shrinker.......
Soooo, you know where it goes........
I started with the next piece and decided it needed juuuuust a little moooore before I started polishing. I was wrong.

.....
I'm gonna have to get a bigger garbage can.........
Okay, attempt number.......aww, hell, I dunno...who's keeping track anyway? On this piece, I went step by step to insure I was doing everything right. I started with deburing the edges of my angles.......
Followed by checking the placement of my index and tick marks for bending......
And just nice and slowly starting the shrinking process.......
Okay, I'm too chicken to go any further. Polishing time.......
Yup. Went too far before polishing. Found a crack. [EXPLATIVE!] So, you know the next step........
Okay, I know that some of you out there have been wondering why I haven't done the following step sooner. Laziness is essentially the answer, I reckon. I just didn't want to take the time to do it, but here it goes anyway.
I decided that it was time to anneal the metal before I started the shrinking process. What this does is essentially takes the metal back to a "soft" material. There's much more to it than that, but that's the basic description. As I shrink the metal, it becomes harder. And as you've seen from the other pieces that ended up in the trash can, the metal can get only so hard before it becomes brittle and cracks. Hopefully, the annealing process will help solve that dilemma.
The first thing to do is to get a rosebud tip on your gas torch and make an extremely rich flame (you know...one where it's putting out that thick, black smoke)...
The next step is to lightly run the torch over the piece of metal you're working with. This will leave a light coat of black soot on it. I know it's tough to see it in this picture, but you don't want too much soot on there, just enough to lightly cover the entire piece..........
Then, you add oxygen to your torch, to get a nice, blue flame going. There's no need for lots of heat here, just a nice, soft flame. You then start to apply the heat to the aluminum. TAKE YOUR TIME. This is an easy place to get impatient and burn right through the piece you're working with. Just nice, even movements, back and forth across the metal......
And how do you know you've got the right amount of heat in the aluminum? Well, you'll start noticing that the soot is "burning" off. Don't ask me the physics regarding the "hows & whys" of this, I just know it works. You can just barely tell from this picture that I'm getting closer to being finished, as the soot is slowly disappearing into thin air. Magic.........
And here it is, all soot-free and soft. Once this is done, go into your office and check out WIX for a few minutes, as you want the metal to cool on it's own........
To spare y'all all of the gory details (that you've seen over and over now), I think this picture shows that the annealing process worked for the first corner (lower left).........
So, it was time to start on the next corner.........
Alllllmost there..........
Then, disaster. Upon making one of my last few shrinks, the end of the angle that had already been completed, contacted the opposite end of the shrinking machine, cracking not only the completed end, but the end that I was working with...........
So, after a few choice words, and some gentle reshaping of that piece (made in disgust), I put it with it's friends in the trash can..........
And that was about it for my day's work yesterday. I was already not feeling well and was grumpy before that series of errors, so I had enough. I went home and stewed over how I was going to regroup and make this work. I think I've got it figured out, but unfortunately, I doubt I'll be able to do much with it today. We have some other stuff going on today that will require my presence on the forklift, rather than the airplane. It's frustrating when I'm constantly pressured to get the job done, yet I'm the only one able (and willing) to do some of the other Squadron work around here too. But, I just do what's needed at the time and will get back to the airplane when able.
Gary