Preparing the Ribs

It's been a while since I've been able to post our progress, but we've still been hammering away at getting the horizontal stabilizer complete. Today was all about preparing the ribs and fitting the skin. I went straight home after work and met up with my dad and we immediately went to working on the plane. We started by truing the flanges on the ribs and getting them as close as possible to 90 degrees. This proved to be a bit more difficult then we thought.. When the ribs come from the factory, the flanges are at about 80 degrees, and they have to be bent to 90 in order to fit flush against the interior of the skin. We did this by pressing the flanges against the soft side of one of our work benches. It took about an hour or so to get all the ribs right, but it was an hour well spent. We also cut the notches in the forward flanges of HS-404 to accomodate for HS-710 and HS-714. Taking off the burs with Scotchbrite finished the process.

Once this was done, we went on to fluting the flanges. This process eliminates the unwanted bow that occurs from when the ribs are punched out of the aluminum sheet at the warehouse. We used Alan Gilmore's technique that worked very well for fluting accurately and predictably. He has a YouTube video located at http://www.youtube.com/watch?v=jqNoVAQLo0M which helped a lot.

After the ribs were fluted and ready, we clecoed them to the front and rear HS spar assemblies and then we fitted the skin to the complet assembly. The pre-drilled holes in the skin match up perfectly with the holes in the ribs, making it quick to put together. So far, this has been the most inspirational moment of the project, it actually looks like an airplane part! The only problem we encountered so far was a large scratch on the HS-601PP skin, it doesn't look too deep, but we're going to call up Van's and see if it's normal to receive parts like that. I know scratches are a hazard when building an airplane, acting as fatigue points which can later turn into cracks. Hopefully a bit of Scotchbriting will take it out.