RV-8F

N772RW

Building, testing and operating an experimental aircraft

HS Rear Spar Assembly

26 Nov 2009

The building begins! After finishing the practice kit and getting a handle on how best to use the tools at our disposal, Dad and I jumped right into the empennage kit.

HS-609s Clecoed HS-609s Clecoed

We had completed inventory of the packages several days ago, and had safely stowed all of the parts not related to the horizontal stab (HS) assembly. Van’s does a great job of wrapping various similar-sized parts into little sub-packages, and the packing list contains a detailed breakdown of everything you’re supposed to have, so the actual inventory, while a bit tedious, is very straightforward.

HS-609 and Scotchbrite Wheel HS-609 and Scotchbrite Wheel

Although we had watched the GeoBeck Empennage Construction DVDs several times and found them very helpful, we decided not to follow Mr. Orndorff’s somewhat out-of-order methodology, and we stuck with Van’s step-by-step instructions. The first order of business then was to “break” the edges of the HS-609 rear spar reinforcement bars. These come pre-tapered and pre-drilled, but they still need quite a bit of work to get the satin finish the instructions recommend.

Dad Polishing Dad Polishing

We tried hand filing with the 609s supported in a vice, but found it difficult to control the file and ended up with too many deep cut marks where the file would “chatter” along the edge. In the end, we found the best solution was to simply sit at the Scotchbrite wheel and grind away the edges and corners. By the end of the session, I had even worn a little groove in the wheel in which I would guide the edge of the 609 until it was smooth. (My apologies for not taking a “before” picture of the 609s, but you can find those elsewhere.)

Safety Tip: When working on the Scotchbrite wheel, be sure to wear leather work gloves, protective eyewear and some kind of dust mask. The wheel will give you a nasty cut, and those tiny airborne aluminum particles are no good for your eyes or lungs.

We finished the bars up by hand with 400-grit wet/dry sandpaper, used wet. This left a near-mirror finish that we found satisfactory. They may not look perfect, but I think they meet the guidelines called out in the plans.

Satin Finish Satin Finish

Next we clecoed the 609s to the HS-603 rear spar, and match-drilled all the pre-punched holes using a #30 bit. Four of the holes on the spar were enlarged to #21 to accommodate the HS-708 rib later on down the road.

HS-603 Spar HS-603 Spar

We then located and attached the HS-412 and HS-413 elevator hinge brackets and final-drilled those to #30. These powder-coated steel parts we found hard to cleco to the spar before drilling, I think because the coating had shrunk the holes a bit. We had to drill each of them out individually on a scrap 2x4 before clecoing them to the spar assembly and doing the final match drilling.

HS-412 Brackets HS-412 Brackets

Finally, we assembled and drilled the HS-411/VA-146 bearing assembly, primed the bearing flange with one coat of SEM self-etching primer, and squeezed the big AN470 AD4-5 rivets with the Cleaveland hand squeezer.

First Rivet! First Rivet!

We were understandably a bit tense at this point, since these were the first real rivets of the project. Others have noted that the -5 rivet is not quite long enough to produce a decent shop head in this assembly, and have substituted a -6. We stuck with Van’s callouts, and found the diameter of the -5 shop head was just a hair small when tested with the rivet gauge, but looked acceptable. You can judge for yourself from the closeup shots.

Spar Assembled Spar Assembled

Well, the pre-game jitters are over, and we’re deep into the meat of the project. There’s no turning back now.

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