I reviewed all my calculations this morning and headed out to the shop. Since pictures do so much better than trying to decipher my detailed dribble in my posts, I took a lot of pics. Objectives were to use some scrap .032 2024 T3 aluminum alclad sheet metal to fabricate each part. I used a couple of different methods for both trimming the part and forming the part because I wanted to see which methods I liked better. To trim the first part I measured the dimensions - 1 and 7/32nds wide by 3 and 1/16th inches long. The length was determine by starting with 2 inches as I discussed in my previous posts. 2 inches plus 7/16 inches to cover the cutout in the 408 rib to clear the spar bars, and then 5/8ths of an inch more for 90 degree flange that lays flat against the Main wing spar web.
I cut the blank using my straight tin snips. This caused the metal at some of the edges to bend just a bit, reaffiriming the reason why I don't like to use the snips when I need the metal to lay very flat. A couple squeezes in my table vise corrected the bending to my satisfaction.
The next task was to mark a line where the flange bend needed to occur. Then I needed to find a piece of metal or wood that was also 3/16th of an inch thick to match the of the rod that purchased to form the bend. After a bit of searching I discovered that my small rapid square was exactly 3/16th of an inch thick, so problem solved. I placed the square flat on the bench, the placed the 3/16 diameter metal rod in front of the square, and then used the flat metal part to align it flush against the edge of the bench. Then I taped up the part over the square and the rod,and secure the square with my clamps. Before taping the part to the square to secure it during the bending process, I placed the bend line for the flange as close as possible over the center of the rod. Then I taped it in place.
Here is the pic before bending:
As can be seen in the pic - I set this one up to bend the short end of the metal part. The was the only way I could do it using this method. To bend the flange I was able to start it by bending it over the metal rod with my hand. Then, after it had been bent over a little, I took my rubber hammer and tried to finish the bend by tapping it down further with that. Unfortunately this caused the square and the rod to start moving as my clamps were not quite strong enough to handle that, so I removed the part and finished bending it with my hand seamer tool.
Here is the finished part placed in its planned location against the rib The bend came out pretty good and seems to follow the bend pattern of the normal 408 rib rear flange.
and again with the longer portion on the other side of the rib web,which is how I intend to attach it to the rib web when the time comes:
the mark next to the 5/16 gap note represents where the 709 rib's rear flange terminates. the whole idea for this part of the mod is to try to make the 408 rib look and function as closely as possible like the 709 rib that it is replacing. SO I ma simply trying to make the rear flange length dimension match the 709 rib dimension as close as possible, and thus the reason for added rear flange parts.
Next is the pic of the 408 rib clecoed into place on the left wing spar in the proper orientation (top and bottom of rib in the correct position). Notice the cutouts on both sides of the rear of the rib web to clear the spar bars from the main wing spar. Also note that there are no spar bars to clear in this location.All 709 ribs have no cutouts, since they are not used in locations where the spar bars exist.
Hopefully this pic makes what I am trying to do very clear:
For the second part I decided to use different methods to create the part and bend the flange. This time I used my dremel tool with a cutoff wheel instead of the hand shears. I guess I should also mention that after cutting out both parts I smoothed all edges and corners on the scotch brite wheel.
Next, instead of marking only one line for the bend line of the flange, I placed two lines. The first is the 5/8s inch bend line, and the second is the 3/32 inch radius line on one side of the part:
Next was the method I used to bend the flange. This time I placed the part in the jaws of my table vise. The jaws are protected with Gorilla tape. to keep the rough edges of the jaws from marring up the surface of the part while clamped in the vise. With the part loosely placed in the vise, I tool the 3/16 inch metal rod and placed it in front of the part on the top of the forward jaw of the vise. Then I position the part so that I could just see the top reference line appear on the very top of the rod. This is how I determined that the bend line was centered on the rod. The other major difference is that this time I will be bending the large area of the part instead of the small flange. Overall I liked this method better but I was not certain if I could secure the rod on the top of the vise jaw well enough to perform the bend. With the rod in place and the part properly positioned, I clamped everything down tight, and then took one of my bucking bars and placed it on the back side of the part and started bending it around the rod as best I could.
And here is the end result of both parts:
And finally I placed the parts on their sides so I could eyeball the edge distance for each rivet that will be driven into each flange of each part. Looks like they should work as expected:
I'll probably trim the parts down to 1.25 inches of material that will be used to rivet them to the rib web, and then each flange gets one AN470 rivet through the main wing spar. Of prepping and priming will need to be done as well. Tomorrow I will trim them and layout and drill the rivet holes.
Was nice to be in the factory again making an airplane.
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