Riveting the rudder frame together

Bottom rudder frame

Started riveting the rudder frame together tonight…the frame goes together pretty easily. Van’s calls out optional LP4-4 blind rivets to attach the rudder brace and control horn. I wouldn’t know how to buck solid rivets here, or even squeeze them unless there’s some way to get a longeron yoke in there. Perhaps it’s possible to change the construction order and rivet the brace and horn together first. Whatever…

A fuzzy rudder counterweight

I also riveted the counterweight skin to its lower rib and then to the spar. That was enough for one day!

Primer

More carcinogenic primer

Despite a cold day (4C/40F) the primer went on well. I found some instructions on the web for my cheapo Harbor Freight HVLP spray gun, and they helped quite a bit.

Mmmm…primer!

And here are the rest of the primed parts. It’s time to rivet!

Back to the rudder

After a brief interruption for a wedding (Ellen’s and mine!), it was back to the rudder. This weekend’s tasks were to countersink the trailing edge wedge, prepare a piece of angle stock to hold the trailing edge straight, and finally, debur and dimple the skins.

Countersinking the rudder wedge

The first step in countersinking the TE wedge was drilling the holes to final size. I borrowed a technique for this from my friend Jim Piavis, match-drilling and clecoing the wedge to a flat surface – in this case, the hollow-core door I use as a work surface. Match-drilling into the door leaves a nice, accurate hole for the coutersink pilot. That, in turn, helps keep the countersink from chattering and chewing up the hole.

Dave’s pudgy hand. Note the wedding ring!

Here’s the end result. The process worked, and the wedge looks good. Another test-fit of the skins and wedge was encouraging. Next step – match drilling one rudder skin to a piece of aluminum angle per Vans’ instructions. I fastened the angle to one edge of the work surface for some added stability. Once assembled and prosealed, the trailing edge will be held straight when clecoed to the angle.

Drilling the wedge

The end result will look something like this…except with both rudder skins clecoed to the angle.

The wedge of doom

Lots of progress in the last three days

Rudder clecoed together

Lots of progress in the last three days. Got the rudder clecoed together, then trimmed and fitted the R710 rudder brace that goes between the rudder horn and the lower rib. The brace has holes punched in it to indicate where material should be trimmed away for fitting, but the plans don’t say explicity to cut to the centerline of these holes as when trimming stiffeners. I cut and trimmed to the hole centers, and found that I was a little short on edge distance when match-drilling to the rib sides. I called Van’s – again – and they said that due to the loading on this part, a little reduction in edge distance would be ok.

Rudder trailing edge clecoed together

I clecoed the AEX wedge in place to get a rough estimate of how well things are fitting together. It’s not perfect, but it’s straight enough to give me some confidence that the trailing edge will go together during final assembly. After this check, I match-drilled the skins. Then came fabrication and fitting of the 0.032″ strips that will hold the lower rudder cap. Finally, I disassembled everything and began deburring/edge finishing rudder parts.

Preparing the counterweight ribs

The next step is preparing the counterweight ribs and fitting them to the counterweight skin and spar.

Counterweight skin fitted to spar

I had to spend an entire evening trying to get this skin fitted correctly. I eventually found out that the skin wasn’t bent correctly at the factory and while I was able to get the skin fitted, the incorrect bends made the leading edge of the counterweight slightly skewed. Van’s says it’s ok, and I decided to use the skin as-is. The skin can be easily checked for a correct bend by simply setting it down on a flat surface with the skin sides vertical. If the skin’s bottom edges sit flat against the surface, it’s probably ok.

Time to build the rudder frame

With the skins done for now, it’s time to build the rudder frame. First step is to fabricate a small 0.032″ spacer that fits between the rudder horn and spar.

Rudder horn clecoed to the rear spar

The plans are a little confusing on this step; a detail drawing on plans page 7 seems to indicate that the holes on this spacer should be drilled in assembly with the rudder horn and spar. But there is a plans step that covers this match-drilling later in the construction procedure, so it pays to read all the way through and entire procedure. Then read it again…and again. Also, a fair amount of filing and finishing is required to allow the rudder horn to fit snugly inside the lower rib’s forward flange. The plans say to do this “if required”. Trust me, it’ll be required. In general, this portion of the plans and instructions are not very well written. A lot of re-reading and visualization are required. That’s not necessarily a bad thing, but a little more work by Van’s to add just a few clarifying words would really help. Van’s, if you’re reading this, I’d be glad to help.

Rudder frame clecoed together

The frame is clecoed together here. One other thing that’s unclear in the instructions is when to match-drill the rudder spar reinforcement plates. I did it when match-drilling the skins, but it should be done before the skins are clecoed on. It’s possible to hit a stiffener with the drill bit when match-drilling those reinforcement planes. Ask me how I know this…

Back-riveting

Since the last update I primed the mating areas on the inside of each rudder skin, then primed the stiffeners. Didn’t have time to mix up some two-part epoxy, so I shot the stiffeners with some Tempo zinc chromate I had lying around the shop. Then it was time to set everything up for back-riveting.

Rudder skin with rivets taped in place

Don’t all those little rivets look cool? It’s much easier to do all the rivet insertion at once and tape ’em into place with removable scotch tape.

Back-riveting a rudder skin

And here we go with the back-riveting. The primer application is my attempt to (a) limit the amount of hideously expensive primer that I’m using, and (b) not add as much weight to the tail. Some notes on back-riveting – there are a couple of different back rivet sets available. Some spring-loaded sets have a large Delrin sleeve that’s really too big to fit in tight places (like between these rivets and the adjacent stiffener angles). I have another one from my old RV-6 days that has a narrow metal collar. I put some hockey tape on the end to protect the surface – works great! [21 Dec 04 – Note from the future…a couple of extra hits on the rivets next to the trailing edge will flatten out the shop heads just a little and reduce the chances that they will cause problems when closing up the trailing edge. Right before I prosealed the TE, I had to squeeze these rivets a bit more because they were keeping the edge from seating properly].

One other communique from the primer wars – the Tempo zinc chromate doesn’t seem to be very durable. Even when applied over alodine, and when using tape on the back rivet set, some of the primer still wore off during riveting.

Back-riveting complete on the left skin

Here’s one rudder skin done…

Back-riveting complete on the right skin

…and the view from the other side. Another bit of info I’ve learned while trimming the blue plastic off these skins is that Van’s is spot-on when they say that the plastic gets harder to remove if it stays on for a long period of time. If I weren’t so obsessive about this stuff, I guess it wouldn’t matter that the plastic looks like crap.

Rudder stiffeners and skins

Lots of little tasks on the rudder stiffeners and skins were taken care in the last week. Right rudder skin stiffeners were cut and trimmed, then stiffeners for both sides were edge-finished and dimpled. One thing I learned from Gus at Van’s is that the reference holes used to trim stiffeners, don’t need to be removed – so I didn’t do that on the right stiffeners as I did on the left ones.

[17 Jan 05 – Note from the future…Van’s calls for these holes to be removed from the elevator stiffeners. Call them if you’re not sure what to do – maybe that will get them to standardize their plans/instructions.]

Rudder stiffeners prepped with the Touch-n-Prep pen

Before priming the stiffeners, they needed scuffing and alodining. I hate alodining…it’s a messy, nasty, potentially toxic process. So I was really jazzed to find Touch-n-Prep pens. These things are the berries…they’re like magic markers full of alodine 1132. Just coat the parts, and let them dry – no rinsing required. I got mine from Stein Bruch at SteinAir. Stein is great…he’s selling these things cheaper than anyone else, and I got mine a day or so before he said it would arrive. I used the pen to alodine these stiffeners, and the only waste was a couple of pairs of nitrile gloves. No contaminated dip water, no mess all over the floor – freakin’ fabulous!

Rudder skins prepped with the Touch-n-Prep pen

Here are the skins scuffed and alodined. This would have been a lot more messy with the old process of alodining. Next step is to prime the stiffeners and skin rivet lines, then back-rivet the skins and stiffeners.