Thursday, September 6, 2012

Faux Pas Averted

Sadly, most of the afternoon was spent correcting the faux pas I made a couple of days earlier. Being in the habit of squaring flanges to webs and having all the rib flanges fitting perfectly thus far, …  well, like a well trained monkey, I began squaring all the flanges on the halves for the fuselage frames.

After doing a few fuselage frame pieces, it dawned on me that I was correcting all the flanges by about the same amount ~ 10 degrees. A red flag popped up in my mind’s eye. Van’s parts are usually very close and here I am making the same correction on all the flanges on the frames, this can’t be right … and don’t think it is.

After stopping, I brought out the trusty angle gauge and looked at every flange on the tail cone bulkhead (left untouched)  ... interestingly they were all ~ 80 degrees from the web, and here I have been bending the tabs an additional 10 degrees to 90 degrees. It finally dawned on me  ...  Yes, you want the tabs 90 degrees to the skin, however, if the skin is on a consistent taper (which it is), then the angle of the tabs must compensate. So instead of 90 degrees, that angle is 80 degrees measured from the back of the web.
   Here is the measurement of a virgin tab, the angle gauge shows 80 degrees.
                                     Here is what some of the tabs I had already bent to 90 degreees looked like.

Fortunately, the error of my ways was caught before the skins were Clecoed onto the frames. I feel I would have noticed this anyway, because I do make a point of looking at how well the flanges fit to the skins … but it would have been far more inconvenient to fix the error then verses now. If the 80 degree angle is wrong I’ll return from the future and update this post.

Return from the future: The 80 degree angle was perfect ... the skins fit flush to all the flanges of each fuselage frame and aft bulkhead. All the parts fit together quite nicely.

                                         Correcting the flange angles I messed up using the hand seamer tool.
Once back on track, there was a little match drilling to do on one of the fuselage frames and then there were four holes that needed to be final drilled to #12 on the mounting plate for the vertical stabilizer.
                                           Final drilling #12 the holes in the mounting plate for the vertical stabilizer.

Next was deburring all the sharp edges and roughness on the fuselage frame components caused by the manufacture's stamping process. There were some lethal edges on the inside edges of the frames.
                                                   Deburring a lightening hole on one of the fuselage frames.