Joe Graham's Online RV-7 Builder's Log
Building the Horizontal Stabilizer
February 24 to March 12, 2006
Now it's time to start the Horizontal Stabilizer (HS) construction. The left and right HS elements are mostly identical and are built in parallel. Here's a view of the two HS702s (Front Spar Channels) , the HS710 (Reinforcement Angle), and HS714 (Splice Angle).
The first step is to cleco the parts together and match drill the 5 inboard holes for each angle and channel. The ends of the angle pieces (With the outboard 3 holes) will be bent 6 degrees aft in a later step. Those holes will be match drilled in assembly with some other parts. Since the angles will be bent, the holes would be misaligned if they were drilled before the bend is made.
After the inboard holes are drilled, the angles need to be marked and shaped. Very similar to the HS609s. Here is a picture of the HS710 as I marked it. The plans call for a rounded end, tapering back to the full width of the angle base 2.5 inches from the end of the piece. This looks like more than I want to grind away, so I think I'll use the band saw to get the rough cuts accomplished.
Here's the results of my shaping efforts on the HS710. Remember the 2D rule on edge distance from any rivet holes? Well this piece does not meet that rule. I removed too much material. &!$%@ *$@%!^%@^#&^$#&*^$#(^#$*&#&*#&*# # (translation - oh darn, I messed up my first piece). I don't have pictures of how this happened and I won't go into much detail, but let me pass on a piece of tool advice for you... DON'T BUY A RYOBI BAND SAW! I guess there is the possibilty of operator error, but I can not for the life of me get that saw to cut a straight line. The blade just wanders all over the place. Very frustrating.
Ok, so lets make lemonade from the lemon. First step - order a new HS 710. Second step - Return the Ryobi Band Saw (or sell it on E-bay if I can't find my receipt). I need to practice the 6 degree bend anyway, so now I have a practice piece. The plans say to use a bench vise and some blocks of wood to hold the piece, and then bend it to precisely six degrees. This is a stout pice of T6 aluminum angle, so I was expecting the bend to be difficult. Not to mention that if it is bent too far, then it needs to be unbent a little, and multiple bi-directional bends reduce the strength of the piece. So I pondered the vise setup, and the method of bending, re-read the plans, and then finally decided to just do it. Here is a picture of the bent piece laid on top of the plans as a reference for the bend angle accuracy. You can see that I achieved a perfect 6-degree bend. That wasn't so hard after all.
So now fast forward a couple of weeks. I had to go out west on a busines trip. Before I left, I ordered a new HS710 from Vans. Here's the fresh new part.
I didn't take pictures of the vise setup the first time, so I did on the second go-around. Here's a picture of the correctly shaped HS710 in the vise and ready for bending. Note the bend line marked on the HS710, at just the top edge of the wood block. This helps line up the 710 in the vise to ensure the proper bend location.
And here is the result in the vise. The photo is a little blurry, but you can make out the 6-degree alignment mark on the protractor. I also verified the bend angle on the plans just like I did above on the practice piece. Perfect!
So now that the 710 is fixed, I can move on. The HS702 flanges needed to be trimmed back about a 1/2 inch from their stock configuration. These parts are also used on the RV-8 which has a slightly smaller aft fuselage and need the longer flange. Anyway, here are the HS702s after I trimmed the flanges, cut the bend relief radii, and bent the inboard webs 6 degrees, to match the 710 and 714 angles.
And here is my favorite tool so far... The pneumatic squeezer. It dimples holes (or anything else that gets in the way) and squeezes rivets, depending on which die set is installed in the yoke. Here you can see that the dimple die set is installed. The HS702 web holes are my first official dimple on the airplane. They turned out perfectly using the squeezer. This is a 500-dollar tool so some folks opt not to buy one. But I think it's the best gadget in my toolbox and is money well-spent.
And finally, here is the properly bent HS702 assembly with the 710 and 714 angles clecoed together.
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