Riveted the trim tab hinge

My disease seems to have abated somewhat, so I spent some time downstairs and riveted the trim tab hinge to both the tab itself and the left elevator. The pneumatic squeezer is the weapon of choice for setting these rivets, but I had some problems getting the flush set to fit between the spar web and some of the hinge eyes. If the flush set is too far forward it can push on and bend hinge eyes, not a good thing. And surfing through the Van’s Air Force forum, I found others had the same problem. My solution was to take a spare flush set and grind it down a bit to reduce its radius. Worked great!

Here’s the trim tab, essentially complete.

Trim tab done

The riblets came out fine, I think.

Trim tab riblets

Prepping trim tab parts for priming

The last few days were spent on prepping trim tab parts for priming – deburring, dimpling, countersinking, scuffing and alodining. No pictures, but it’s nothing you haven’t seen before.

When countersinking the TT spar upper flange, I match-drilled it to a piece of rectangular pine moulding before applying the countersink. The match-drilled pilot holes keep the countersink pilot centered, thus preventing the countersink from chattering and chewing up the hole.

New trim tab skin came in

Another trip during the last week, so only a few things accomplished. First, the new trim tab skin came in. Folding the inboard tabs went a lot easier this time.

TT inboard tabs folded - again

Next, I removed the outboard tabs and forged ahead with making another riblet to fit inside the trim tab’s outboard end. Came out pretty well, I think.

TT riblet

The trim tab riblet in place. Until we have the money for a wing kit, there’s plenty of time to fuss over small details like this – so why not?

TT riblet in place

Trim tab

The last couple of days brought mixed success with the trim tab. Got the inboard tabs folded and was pleased with the results.

TT inboard tabs folded

The outboard tabs didn’t come out so well. They looked ok, but not great – sorry, no pics.. Got everything put together, then clamped the piano hinge into position and match-drilled it to the spar and skin. This is where things began to go south a bit.

The plans call for a 1/4″ distance between the front edge of the hinge plate and the match-drilled holes. This leaves exactly 3/16″ edge distance between the center of each rivet hole and the aft end of the hinge plate – and that’s the absolute minimum for #40 hole. The clamps must’ve needed a few extra turns, because the whole assembly slipped a bit and some of the holes didn’t have the required edge distance.

So, it was time to order a new hinge. And since I was ordering parts from Van’s, I decided to order another trim tab skin – just to see if I can do better the next time around. I may just cut off the outboard tabs and fabricate another riblet to take their place.

Brown Aviation Tool Supply

Another work trip last week, so no RV building. One of the nice things about traveling to Oklahoma City is making a trip to Brown Aviation Tool Supply. They generally have good prices on “staple” building items like drill bits and bucking bars, so a trip to OKC is always a good opportunity to stock up. On this trip I picked up liquid Boelube, some “rosebud” (hex flute) deburring bits, drill bits, and a new countersink cage.

Spent a few hours today on bending the trim tab trailing egde – sorry, no pics. We’re still scraping together the money for a wing kit, so I’m not in a huge rush to finish.