Tonight I’m starting on another F1 Mod to the Horizontal Stabilizer. This mod calls for adding skin stiffener angles to the upper and lower skin surfaces between the rib bays – 2 per bay, both on the upper and lower surfaces. See the diagram below.
I began by marking lines of the HS skins where the stiffeners will be located. As I wanted to line up the stiffeners with existing rivets, I wasn’t able to get the stiffeners to per perfectly in line with the same plane as the main and tip ribs. Therefore you will see that they are slanted inward a little.
The stiffeners are made from 0.040″, 2024-T3 aluminum. I cut the pieces to size, so that there is a little space between the stiffener edges and the forward and rear spars.
After the stiffeners were cut to size, I used fluting pliers to get the stiffeners to match the curvature of the HS. In the picture below, you can also see that I marked the edge distance on the front and aft end of the stiffeners. I center punch these ends and pilot drill the stiffeners. Once pilot drilled, then I line the stiffener up on the lines previously marked on the inner skin surface. When I get the stiffener centered on the line, I then match drill the stiffener to the HS skin.
Here the stiffener is match drilled to the skin. Also, due to interference with the rear spar outer hinge doubler, I have the outer stiffeners facing towards the tip to provide clearance for the hinge doubler.
Next I removed the skin stiffener and with the rivet fan, spaced the rivet holes on the stiffener to match the existing rivet holes in the HS skin.
Here is a picture with the stiffeners all match drilled to the HS skin.
Amongst all the drilling on the stiffeners, I also finished drilling the spar to tip rib stiffener angles to their final 1/8″ dimensions.
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