A happy New Years at the ThermosWorks

After more than 12 years, the rudder and elevators are mounted to the empennage and they’re moving freely without binding. Took a lot of fiddling with washers and spacers, and some expert help from my Tech Counselor (thanks Bob!) to make that happen, but it’s done.

Here’s a short demo of today’s work…

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


The tail end

Over the last month and a half I’ve been slowly working on getting the horizontal and vertical stabilators attached. There’s nothing terribly complex here, but there are some places where access for drilling holes and installing fasteners is tough.

Starting with the horizontal stabilizer, I aligned it with the fuselage per plans and drilled the inboard holes that attach the forward spar. Access isn’t so good here for a regular drill so I used the angle drill and my technique wasn’t great…despite using an undersize drill bit, the holes wound up oversize.

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The outboard holes were easier to drill, but required some extra care to ensure that edge distance was maximized on the stabilizer, fuselage longerons and bulkhead. I drilled these holes initially to #30 to check alignment, then final-drilled them to #12.

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I talked with Vans about how to handle the oversized inboard holes. Their recommendation was to upsize the holes to 0.25″ and use AN4 fasteners. Before I did that, though, I wanted to try a first-oversize close tolerance NAS6604 fastener that’s approximately 1/64″ larger than a norman AN3 fastener. That would preserve 2D edge distance on the hole. I reamed the oversize holes to accommodate the NAS6604 bolt, and the bolts were a perfect fit – problem solved.

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With the forward horizontal stab spar drilled to the fuse, I clamped the rear spar to the fuselage attach bars. If you look carefully, you’ll see the business end of a 3/16″ punch between the rear spar and fuselage aft deck. That 3/16″ gap establishes proper incidence for the horizontal stab relative to the fuselage.

With that gap set, I clamped the fuse bars and rear spar together, and using my Brown Tool drill block, drilled the four #12 holes that hold the assembly together.  I use the drill block whenever I can…it works great for getting nice, clean, straight holes.

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Here’s everything bolted in place. Look carefully and you’ll see the dimpled heads of the NAS6604 bolts on the front spar.

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Here’s the HS stab in place. It’s been sitting in storage for ten years…and now it’s part of the airplane. Cool.

The next step was to attach the vertical stabilizer.  There are several steps in this process, and a couple of them were somewhat tricky. Just getting the vertical stab aligned correctly was a challenge – it was tough to get everything clamped in place firmly enough that the vertical stab didn’t shift while measuring its alignment relative to the horizontal stab.

I had already fabricated the upper stab attach bracket and match-drilled it to the fuselage – with the stab aligned I used my trusty drill block and match-drilled the attach bracket to the stab. All those vise-grip clamps I’ve been collecting sure came in handy.

Drilling upper VS attach

Upper VS attach bracketAfter the upper attach bracket was match-drilled, I fitted the angled attach plate that connects the vertical and horizontal stabilizer forward spars.

Drilling VS front spar 1 Here I’ve already match-drilled the plate to the horizontal spar – those holes will be opened to #12 – and I’ve started drilling the plate to the vertical spar as well. I had to insert a 0.020″ shim between the plate and spar to improve the fit.  The plans tell you to anticipate this, and have dimensions for fabricating a shim if one is required.

Drilling VS front spar 2

I used the angle drill sparingly on these holes. Some of them didn’t get final-drilled until I removed the vertical stab for priming.

Rear VS attach

Here’s the vertical stab’s rear spar primed and bolted into place.

Tailwheel fitting bolted and torqued

I neglected to take many pictures of the measurement and drilling process for the lower three bolts – they secure the vertical stab lower spar and tailwheel aft attach bracket to the fuselage.

The measurement process was a little tricky – edge distance has to be maintained on the tailwheel bracket and the vertical stab spar, but they’re on opposite sides of the aft most fuselage bulkhead so it’s impossible to directly measure edge distance. The only way I could get this done correctly was to establish a series of reference points for the tailwheel bracket measured from the fuselage sides and aft deck. Those reference points allowed me to project the location of the tailwheel bracket onto the rear side of the aft fuselage bulkhead.

With the vertical stab clamped into place, I was then able to pick hole locations that met all of Vans edge distance criteria. After that, drilling the holes was a piece of cake.

Tail in place

Here’s the vertical stab bolted and torqued into place…very cool.

Tail attached from the rear

Another pic? Sure, why not…

Nice tail!

And I couldn’t resist temporarily installing the rudder…it’s been waiting a long time to be on the airplane!

Fun with the pneumatic squeezer

VS frame riveted to skin, spar clecoed in place

VS frame riveted to skin, spar clecoed in place

Ellen and I riveted the VS frame into the skin, then came all sorts of fun with the pneumatic squeezer setting the root and tip rib rivets. Had to drill out a bunch of ’em…

…but the end result was good. Once I figured out how to handle the no-hole yoke, getting the tip rib rivets was easy. The aft spar will remain clecoed until my first EAA Tech Counselor inspection.

Motivation is going again!

VS frame riveted and clecoed into its skin

I’ve been on travel for the last couple of weeks, but finally got back to the airplane. A trip to the annual EAA Chapter 486 RV Forum got my motivation going again!

VS nose rib scratches polished out

Riveting the root rib, nose rib and front spar together proved to be a problem for me. I was being a little too cautious in bending the nose rib out of the way, and thus cleated a couple of rivets. Considering using blind rivets, I called Van’s to find out which ones would work. Turns out that an LP4-3 would work fine, but I decided to give solid rivets one more try and everything worked ok except for…

…some scratches from the bucking bar. Some fine emery cloth and a scotchbrite pad polished ’em right out.

…back to the VS

Just finished up the HS to the point of being ready for inspection. So…back to the VS.
The next step in VS construction was riveting the rear spar together. Not too many problems here; the pneumatic rivet squeezer proved its worth once again while squeezing all those -4 rivets.
Finally got some use out of the Avery back-riveting plate. The countersunk/dimpled rivets came out pretty well – or at least the camera makes ’em look good.
The frame is going together next. Here, the bottom rib/spar rivets are ready to be squeezed or bucked. I really need a thin-nose/no-hole yoke for the squeezer. It would really help here.

Remaining countersinking done on the VS spar doubler

Not much progress in the last week…family stuff took priority, and then work stuff got in the way. I did, however, get the remaining countersinking done on the VS spar doubler.

Following that, I finished all the parts prep work – deburring and edge polishing, then dimpling for the other VS parts. All that remains for the VS before assembly is cleaning, Alodining and priming.

Primer arrives

Lots of things happened in the last week. My primer finally arrived, after only a month’s wait. Super Koropon may be a great primer, but I don’t understand why it takes PRC a month to crate and ship a two-gallon kit.

One thing I didn’t mention in the last couple of weeks is that I messed up the VS spar reinforcement plate while trying to cut lightening holes with a fly-cutter. That’s probably a result of not taking shop classes in high school.

There were some newsgroup debates about whether to cut the holes at all. The argument that makes the most sense to me is that lighter is always better, at least in RVs, and that 8 ounces saved in the tail could mean not having to eventually add pounds of weight in the baggage compartment to fix a CG problem.

Anyway, the new VS spar reinforcement plate arrived on Tuesday, and after using the old part for fly cutter practice, I was able to cut acceptable holes in the new plate.

A side note about pre-punched parts – I was concerned that the new plate would have some minor alignment problems with the spar itself, since I had already match-drilled the two. Well, the new plate clecoed right into place on the spar. Pretty impressive manufacturing tolerances at Van’s, I think.