If it was summer time in Colorado, perhaps having these difficulties would not matter so much to me. But when you have to fight the cold and the wind outside, it just makes these little dips in the road that much harder to take. The step forward was bending the trailing edge of the left elevator yesterday - very much a non-event, and everything turned out as expected. Dare I say I think I have the hang of bending trailing edges now. Unless there is any bending that takes place during the fuselage construction (Longerons I think), I think that the only things left to bend are the TEs of both ailerons during the Wing construction.
Here is the elevator skin in the bending brake, with the forward spar clecoed and clamped in place to serve as a reference for when the bend has gone far enough.
I clamped the center portion of the spar to the skin since you cannot get clecoes in the rivet holes in that area because the web on the spar is not wide or tall enough to fit clecoes inside the flanges.
I am including this next pic as a "Don't do this" photo when you bend your trailing edges. Do NOT place the end ribs on either end of the spar prior to bending the trailing edge. I did remove this rib prior to bending. I only put it there to help stabilize the placement of the forward spar and to check the angle that I was looking for at the root after the bend was completed. If you leave it attached you may not get the correct bend in the skin and that would be bad and possibly expensive to fix:
And here is the tip after the bend. The nice thing about bending this skin is that it is MUCH easier to bend than the other skins, since just under half of the trailing edge has been removed for the area that will be populated by the moveable trim tab. ON the other hand, it does make this a bit more awkward because you have to double check to ensure that the edge is positioned exactly where it needs to be, which is a bit more difficult due to the loose skin flopping around on the inboard side.
Notice the duct tape on the edge of the tip to keep the bottom skin from sliding forward as much as possible, and the flush edge up against the hinge line. This method has worked well for me thus far. There are all sorts of other posts out there talking about using 1/8 inch dowels to keep the proper radius of the TE, or placing the edge a certain distance forward of the hinge line, etc. I have found all of this to be unnecessary. What I did do was tape down both bottom edges, added a 2x4 in front of the brake and under the skin to help support the bottom skin that hangs out of the bending brake so as to prevent the bowing of the bottom skin, and placing the edge right up against the hinges before starting the bend. Works well enough for me.
Here is the shot from the right side. That curved tab will get cut off later.
Close enough from the top of the forward spar for me. The slight bow in the pic below is known as "ballooning", and if I really wanted to, I could keep trying to work that out until it was completely flat, but I don't think that this is necessary. Van's says to get it on top of the spar or "close" to it, so that there is not excessive stress required to hold the skin onto the spar. Strangely, this is exactly the opposite of the way that the skins for the Horizontal and Vertical stabilizers are applied to the frame. They are bent from the front side and attached to a spar at the back, so those skins are supposed to be stressed by design I guess, and they must be held down with clecoes to keep them from springing back up again.
Pic is a little confusing because the right elevator is sticking up in the back ground. So for clarity, these pics show the elevator from the front, with the forward spar web standing vertically, and the top left elevator skin shown draped just above the top edge of the forward spar flange to show where the bend ended up on the front side. If that fails to clear it up, just use your imagination! :)
Looking at the bottom side after the bend:
A blurry pic of the root end of the bend. I was still looking for about a 1/8 inch radius for the final bend. You will find that to get this raduis you will need to force the brake down to the point where the stiffeners from each side of the skin just start to contact each other. As long you do not forcefully smash the skin down to this point, and simply keep applying constant, steady pressure on the brake until this happens, you will end up with a nice crisp bend in the TE, which is what you want.
this bottom skin above looks a little bit bowed, but that is because it is sitting on top of my foam pad with no other structural support. So don't be fooled!
Next, I drew lines on each of the tabs that are going to be cut off. I marked them where the bend lines are supposed to occur, which is parallel to the line of the rest of the edge of the trim tab and elevator per the plans. I will then add another line about 1/8 inch further outward toward the end of the tab from each of these lines to ensure I have enough excess material to trim to final size after the hinges are installed on the trim tab and it is positioned on the elevator.
And now for the "2 steps back" part of this post. With the elevator skin bent successfully, time to work on the tip rib and drill that pesky lead counter weight.
Here is the rib assembly clecoed for match drilling onto the forward spar. Same way that was done for the right elevator.
Problem came after drilling the lead counterweight. I found a builders web site after completing the right elevator that mentioned the use of the drill press, and what seemed to be a better approach to drilling out the counterweight and corresponding holes in the counter balance skin and the forward flanges of the E703 and E704 tip ribs. The steps were basically to attach the rib and counterbalance assembly per the plans, but instead of free hand drilling the lead with the hand drill, simply mark the holes on the lead with a sharpee where the pilot holes on the front of the counter balance skin are located. then you disassemble everything and put the lead counterweight on the drill press and drill the holes to size. Then you put it all back together again and final drill the holes on the counter balance skin and then finally all the way through the lead weight and onto the forward flanges of the two ribs. Doing it this way seemed as though everything would line up just perfect, right?
Well, I think my big screw up may have been setting a 2x4 on the vise on my drill press so that it was level according to my bubble level, instead of ensuring it was PERPENDICULAR to the drill bit. I think this actually created an angle other than 90 degrees between the lead counterweight and my drill bit. Long story short, one of my holes in one of the ribs turned out to be just wide enough for the washer and the nut to be placed on the forward flange of the tip rib, similar to how it turned out on the right elevator.
Unfortunately, the hole I ended up with on the counterbalance rib flange was way too far inboard. Result - part ruined, hole dimensions in my counterweight are now suspected to be incorrect, and I need to order more parts and then ultimately learn how to smelt some lead to fill the holes in the counterweight and start all over again. I was too disgusted to take pics of this last night, so those will have to wait. Ordered a new counterbalance skin and counter balance rib from Vans today so should have those in a couple of days, hopefully before the holiday.
Next time I will do the following a bit differently:
1. Ensure that the counterweight is SQUARE to the drill bit instead of LEVEL to the ground - stupid me!
2. Drill a 1/16 inch hole through the lead counterweight on the drill press instead of drilling the final sized #12 hole for the screw. I will then take the counterweight with the small holes and drill through the entire assembly to see where the stupid hole will end up on the forward flange of the rib. At least this way I can tell how I need to adjust the hole, if at all, before I commit to drilling out a large hole and screwing up the hole thing all over again.
Once I know the hole is correct, I will disassemble the parts again and finish drilling the hole in the drill press.
And as a last thought before I close, let me be perfectly clear about the settings and drill speeds I used to drill out the counterweight on the drill press, which actually worked out pretty well:
1. I step drilled the counterweight just as I had done before. This allows removal of small parts of the lead without seriously bogging down the bit. I started with #40, followed by #30, #28, #21, #19, and finally a #12 bit
2. Drill press was set to 3100 RPM - as fast as it can go - I did not change it to a slower speed at all.
3. Used 3-in-1 oil RELIGIOUSLY for this. that means drill about 1/8 to 1/4 inch at a time, stop the drill bit, clean it off, re-oil the bit, drill another 1/8 to 1/4 inch, wash, rinse, repeat.
4. Technique to is be VERY SLOW with the press. I also would set the stops on the press so that the drill bit would not go all the way down initially. I would leave it about 1/8 inch high, and finish the hole by setting it down all the way once the drill had removed all the material down to that point.
5. Be sure to apply pressure to the press bar, and then back it all the way out to remove the slag. If you have the bit properly lubricated you should see small chips come out, and not see too many groove-filling slivers come up. Slivers are bad and may cause you to mis-direct your hole if you are not careful.
6. Took a while to do it this way, but the holes got drilled out as straight as my settings would allow.
Hard part about this is not being able to clamp the lead. If you try to clamp it you will distort its shape and will have to melt it down and reform and start all over again, or order a new one from Vans. This was even harder because my drill press caused the weight to vibrate quite a bit. Not so bad when you start out, but after the 2x4 got a bunch of oil all over it, it got very slipperly. I have a laser device on my press so I can keep a relatively good reference to the hole position and the drill bit. So I held the weight with my left hand and ran the press with my right.
Out of all the trials and tribulations I have endured thus far on this project, I would have to say that drilling non-pre-punched holes through multiple layers and thicknesses of dissimilar metal has to be the most challenging thing to do.
So hopefully that provides enough detail for those that may follow so that you don't screw yours up the first time around!
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