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.

Left elevator ready for riveting

Work and the Archer annual have been consuming most of my time recently. But I finally got the left elevator ready for riveting. One oops here…after riveting the ribs and one side of the spar, I realized that I’d forgotten to RTV the stiffener trailing edges.

There wasn’t enough space to get my hand inside the elevator, so I worked around it by taping a couple of soda straws together, squirting RTV in one end of the extended straw, and using an air chuck in the other end to blow the RTV out between the stiffeners. RTV is pretty messy stuff – I think I got more on me than I did in the elevator – but in the end it worked fine.

RTV...what a mess!

Ken…where are you?

I haven’t been able to reach my EAA Technical Counselor (Ken…where are you?) so I asked Bob Booth to take a final look at my work before I finish the last empennage part. Bob is an IA and has been performing annuals on our Archer for the last two years. He’s very thorough, and has an eye for detail. He took a hard look at the Mighty RV’s empennage and was very complimentary of my craftsmanship. That was great to hear!

We also accepted an offer on the Mighty Archer this evening. Even though we’re committed to selling it, it feels like we’re losing a member of the family. The Mighty Archer has been a good ship, and she’s taken good care of us.

The dreaded elevator tab bend

It was time for (insert drum roll here…) the dreaded elevator tab bend. Folllowing Vans’ directions, I cut blocks out of a piece of very hard red oak. I did some practice bends with the blocks and a vise, and everything seemed to be working. So, I jigged up the blocks and left elevator skin on the bench.

Blocks in place

Following the directions further, I started bending the lower tab. Well, it didn’t come out so good…


Despite two big clamps, two-sided tape and a precisely measured bend line, the block wasn’t positioned quite well enough for nice, crisp bend. It doesn’t look really bad, but I decided to cut my losses by cutting the tabs off and inserting a bench-formed ‘riblet’. Here it is…

Dave's handiwork

Not too bad, I think. By the way, if you have the same problem and decide to make a riblet, the hardwood wedge used to bend the elevator tabs also makes a good forming block for the riblet – assuming you make the wedge the same angle as the elevator trailing edge (11 degrees is what I measured). Just make sure you have the block’s edges appropriately radiused.

Here’s the block inserted in the elevator skin…looks like a good fit! I don’t know yet if I’ll install it web in (with solid rivets) or web out (with blind rivets).

Dave's handiwork

The trim motor

Back at work after a too-long break. First task for today was to fit and drill the left elevator’s electric trim mounting plate and brackets. The plans-specified mounting dimensions for the mounting brackets may not be quite right; if you use them, the trim servo’s control arm may not be centered in the mouting plate cutout. I adjusted the servo/bracket assembly on the plate until the control arm alignment was correct, then match-drilled everything

Here’s the final result after deburring, dimpling, priming and back-riveting. Not too bad.

More trim, please

One other gotcha. The rearmost rivets on each mounting bracket (kinda hard to see in this picture) will probably interfere slightly with the trim motor itself. I test-fitted the motor, then gave those rivets a couple extra whacks with the back-rivet set.

Riveting trim

Still no progress

Between my sister’s wedding and the almost-finished Archer annual, I’ve made absolutely no progress on the left elevator over the last week. If there’s a record for the slowest empennage construction, I’m definitely a contender.