A few tips

I’m awaiting delivery of the avionics harness from Approach Fast Stack so I decided to tackle a task I’ve been avoiding for more than 13 years – fitting fiberglass tips to the horizontal stabilizer, elevators, vertical stabilizer and rudder. I’ve said before that I hate working with fiberglass and that’s still the case.

Van’s ships the elevator tips with no front end and recommends fairing over the counterweight with an epoxy/flox fill, essentially making it non removable. I decided to add a thin fiberglass layer over but not attached to the counterweight so that I can remove the tip later on if necessary.

Tip prep was simply sanding down the front surfaces to give the layup something to bond do.

Elevator tip prepped

I laid up 3-4 layers of 9 oz BID cloth over the counterweights and front of the tip. Before doing that I covered the elevator and counterweight with clear packing tape as a mold release.

Fiberglass ready to apply

The layup initially looked too thick but when I sanded it down to match the elevator and HS tip there wasn’t much left – but there really doesn’t need to be.

Initial fiberglass layups

Here’s the inside of the tip after removal..it conformed pretty nicely but I had some voids in the cloth that required some additional epoxy to fill.

Interior of tip after removal

After sanding and before priming…looks good!

Finish-sanded tip

The HS tips come without a back end and there’s no requirement to add one but they look better and more “finished” if they’re closed – so that’s what I did, using the foam technique in Section 5 of the instructions and and a sheet of pink foam insulation from the aircraft construction department at Home Depot.

HS tips covered

The same foam closeout technique was used on the VS tip…already done in the pic below.

The rudder upper fairing was a really poor fit, a common complaint with previous versions of fiberglass parts shipped by Van’s. I had to build up the front end with balsa and fiberglass, and apply epoxy and microbaloons to fill gaps on either side.

Upper VS and rudder tips

Surprisingly, the rudder lower end cap fit pretty well when trimmed to the scribe marks applied by Van’s. I decided to make it removable by adding #6 platenuts to fairing attach points on the rudder.

Lower rudder cap

The lower end cap looks good now, but pop-riveting the nav/strobe light attach plate caused the fairing to crack (shit!) so I had to mix up some epoxy and flox for a fix.

Lower rudder tip fitted

Here are all the emp tips sealed and primed with K36 primer to protect them until time for paint.

"Finished" emp tips


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.