Main ribs primed and riveted to front spar

Over the last two weeks, I cleaned and primed all of the main ribs for the left wing.  I also finished riveting all of the platenuts on the upper and lower flanges of the main spar, which needed to be redone since Vans replaced my front spars a few months ago.  After I had my system down for installing the platenuts, I was able to finish all of them in about two hours.

Yesterday, after all of the platenuts were complete, I worked with Jim to rivet the main ribs to the front spar.  I was a bit worried about this process, but it all went very well.  Out of seventy or so rivets, there were only two I wasn't totally happy with, but both were acceptable.  An excellent days work!  I made the mistake of riveting the outboard rib, which only gets riveted to the rear spar at this time.  I started today by drilling out those five rivets, and proceeded to rivet all of the ribs to the rear spar. Several different size rivets are used for this particular section, so I was frequently referring to the rivet callout on the plans.  The left wing skeleton is now ready to be clamped to the wing stand where most of the remaining wing construction will take place.  This coming week I will complete all of these steps once again for the right wing.

Left side ribs cleaned and ready to be primed

Priming in progress

All left side ribs ready to rivet to front spar

First ribs attached to front spar

Riveting teamwork

All ribs attached

Riveting last few outboard ribs to rear spar

Rear spar attached to main ribs

  

Main ribs ready for primer

I've had the majority of the work on the main ribs completed for some time now, but I hadn't yet decided which holes I was going to drill / increase in diameter for items such as pitot and static lines, coax, and AOA tubing.  All of the holes are drilled for the 3/4" conduit (purchased from Vans) that I will be installing for most of the wiring. The middle hole on most of the main ribs is pre-drilled to 7/16", and is therefore left alone.  The bottom tooling hole was opened up to 3/8", which is the size specified by the SafeAir1 pitot / static kit for grommets.  Only one tooling hole exists on the three outboard ribs, and I opened up that hole to 3/8" also.  It was not necessary to modify the outermost rib.  This was the last step that needed to be finished prior to priming all of the main ribs and attaching them to the spars.

Conduit holes drilled to 3/4", one tooling hole on each rib opened up to 3/8"

All main ribs ready to be scrubbed and primed

Tank baffle work

I needed to fit the rear baffles to both fuel tanks, so I spent a little time getting them ready to be match drilled to the tank ribs and the skin.  I removed the vinyl from the rivet lines, and deburred all of the edges.  With that finished, I clecoed the baffle to the right tank and match drilled all of the holes that attach the baffle to the skin, and then the ones that attach the baffle to the tank ribs.  The same process was completed for the left tank as well.

Vinyl removed from rivet lines

Baffle edges deburred

Baffle match drilled to skin and ribs

Fuel tank prep

I took a slight detour from the plans and did a little work on the fuel tanks.  I already had all of the fuel tank ribs deburred and straightened, and I wanted to attach them to the skins.  I hit the nose of each rib briefly with the Scotchbrite wheel to remove any bumps around the notches, which allowed the skin to fit well.  As many builders have discussed on their build logs, it's pretty challenging to attach the skin to the ribs for the first time.  I found a good description of what sounded like a practical method on Jason Beaver's RV-7 builder's log, which I modified slightly.  Here are the steps I used to cleco the skin to the tank ribs:

• Cleco the entire upper surface of each rib to the skin
• Place two 2x4s stacked on top of one another on the floor, and place the back of the ribs on top of the 2x4s.  This keeps the skin off the floor
• By pressing down on the leading edge of the skin, it becomes easier to align the holes between the ribs and the skin.  Place clecoes from the leading to the trailing edge
• A pick can be used to align the holes before clecoes are inserted

Once both sides of the tank were clecoed to the ribs, the tank was placed in the tank cradle and all holes were match drilled.  The rib locations will now be marked for future reference (which rib goes where), and everything will be disassembled.

Tank ribs clecoed to upper surface of skin

Tank in cradle prior to match drilling

Skin match drilled to ribs

First portion of tank assembly complete

Wing skeleton assembly

Everything has been progressing nicely with the wings.  I finished riveting the rear spars a few days ago, and assembled the right and left wing skeletons today to match drill the rear spars to the main ribs.  It takes longer to get all of these components clecoed together than it does to match drill them.

Once the rear spars were match drilled to the main ribs, I attached the outboard nose ribs to the main spar and match drilled them also.  The inboard nose ribs make up the fuel tank, and are attached later.  A few holes exist in the main spar that don't exist in the ribs, so the spar is used as a guide to drill those holes.  A 12" drill bit works well for this, which allows you to flex the drill away from the ribs and keep the drill bit in correct alignment.  With that completed, the nose ribs were labeled, removed from the spar, and all holes were deburred.

Left rear spar attached to ribs and match drilled

Right outboard nose ribs attached and match drilled

Wings assembled - nearly ready for rivets.

Rear wing spars

With all of the main and nose ribs deburred and straightened, it was time to start construction of the rear wing spars.  The primary component of the rear spar is an aluminum Z channel, to which several doubler plates are attached in critical areas for reinforcement.  The inboard doublers (W-707D and W-707G) require trimming at a specific angle prior to being attached, and an opening in the middle doubler (W-707E) must be drilled to allow movement of the aileron pushrod.  For surprisingly simple structures, it seemed like it took quite a bit of time to get both of the rear spars ready for rivets.  It was rewarding to have them finished though.

Started match drilling doubler plates to spar channels

Trim lines marked on W-707D.  This will be used as a template for W-707G

Aileron pushrod opening started with unibit.  Remaining material removed with dremel.

Opening enlarged to final size and deburred.

Outboard portion of rear spar ready for rivets

Center doubler only requires 5 rivets at this time

Inboard doubler plates attached and ready for rivets

Rear spars finished

Trim tab motor test

A small amount of work needed to be done to finish up the trim tab.  I needed to increase the size of the opening in the skin where the threaded rod exits to allow full up/down travel.  This was accomplished with a rat tail file and some emery cloth.  Once that was finished, I connected the motor leads to my cordless drill battery, and tested the motor in both directions. It was cool to see the motor moving the trim tab for the first time.

Increased size of opening in skin for trim tab threaded rod

Used cordless drill battery to test movement of trim tab

Completed rudder and elevator leading edges

I've been working on finishing the last items on the empennage over the last few days.  My wing kit arrived a few days ago, and I'm anxious to start working on the forward spar.  The leading edges on the elevators and rudder needed to be closed up, and I have a small amount of work on the left elevator where the trim tab motor sits, and that's it for the tail section!  

Getting the leading edges of the elevators and the rudder to come together nicely takes a bit of work.  It's easy to roll the leading edges, but it's challenging to get the outer skin to sit flush without any gaps after the blind rivets have been set.  To resolve this, I ended up slightly over bending the outer skin, which allows the two skins to sit flush next to one another.   Bending one section at a time, outboard to inboard, makes the process easier.

Several builders have written that they used a pipe wrench to grip the dowel (3/4 inch) that is used to roll the leading edge.  I found that a steel handle, such as that used for a bending brake, worked much better when inserted into a hole drilled through the dowel.  The wrench was hitting the forward spar of the elevator, limiting the amount the leading edge could be rolled.  Using the steel handle at the inboard end of the elevator by the control horn eliminated this issue.  

After I had the skins rolled, I taped them in place with strips of duct tape and match drilled the holes.  I didn't find it necessary to use the ultra sticky duct tape that some builders use - the standard duct tape worked great, and didn't take the primer or blue vinyl off where I didn't want it removed.  The tape was then removed, the holes deburred (with a scotchbrite pad on the interior surface), and the blind rivets were set.  I wasn't happy with one of the elevators after it was finished, so I drilled out the rivets, slightly adjusted the leading edges by bending the skin a bit more, and re-riveted.  I was very pleased with the results.

Two sections rolled on right elevator

Right elevator leading edge finished

Left elevator leading edge clecoed - ready to be match drilled

Two sections on rudder complete - one to go

Rudder leading edge finished

The completed airplane parts are getting larger!

Vertical stabilizer finished

With the elevators and rudder complete except for the leading edges, I went ahead and finished the vertical stabilizer.  Jim and I set the internal rivets with rivet gun and bucking bar, and I finished the perimeter rivets with the hand squeezer.  No surprises here - everything was fairly straight forward.  There are a couple of rivets along the rear spar that are difficult to squeeze since they are located right next to the hinge brackets, but the no hole yoke worked pretty well in those areas.  Once everything was finished, I removed the blue vinyl and hung the completed stabilizer from the ceiling.

Hand squeezing perimeter rivets

Vertical stabilizer finished - ready to hang next to the horizontal stab

Ready for storage

More rudder work

This weekend I made good progress on the rudder.  I notched the counterweight to fit between the rivets in the counterbalance rib, and torqued the #10 screws after the weight was in place.  All of the perimeter rivets were then set, with the exception of the trailing edge (and a few in the top and bottom ribs for trailing edge access).  I've been doing some reading about the best method to tackle the trailing edge, and decided to use Proseal to keep the skins attached to the AEX wedge and keep everything straight during riveting. I allowed the Proseal to cure for nearly a full week, as it has been pretty cool in the hangar, which likely increased the cure time.  

I used one of the rudder skins prior to final assembly to match drill the trailing edge holes in a piece of angle aluminum.  That piece of angle was then clamped to a second piece, onto which the holes were transferred.  That allowed me to clamp the trailing edge together after the Proseal was applied to the AEX wedge until the curing finished, keeping everything straight.  I have to say I was more concerned about messing up the trailing edge than I was bending the ends of the trim tab, which gives many people trouble.  I looked at several examples and spoke with several accomplished builders, and decided to squeeze all of the rivets rather than use the back rivet technique.  I felt that backriveting left too much room for error, and that I could control how much the rivets were driven more effectively with a hand squeezer.  This was the method I used:

• Numbered the trailing edge holes 1-6, then repeated the pattern down the entire trailing edge.  I used these numbers to set the rivets in a systematic pattern to prevent warping.
• Starting in the middle and working to one side, I set all of the number 6 rivets half way, then repeated the process in the opposite direction.
• Repeated this process for all number 5 rivets, and so on, until all of the rivets were set half way.
• I then took a flat set I had ground down on my Scotchbrite wheel to match the angle of the trailing edge, and set the rivets the rest of the way, using the same pattern as before.  I constantly checked to make sure no warping was taking place. 

This process resulted in a nice straight trailing edge with no dings in the skin.  I'm very pleased with the results, and happy this portion of the rudder is complete.

Counterweight notched and countersunk, ready for installation

Torquing counterweight screws

Front spar attached to left and right skins

AEX wedge clecoed to table for countersinking.  Holes were match drilled in table to center the countersink pilot

Aluminum angles match drilled and clecoed to trailing edge

Removed primer from inside portion of skins where Proseal will be applied

Thin layer of Proseal applied to both sides of AEX wedge and placed in trailing edge

Trailing edge clecoed between aluminum angles to cure

Rivets taped in place (all in the same direction) ready for squeezing

All rivets set half way with flush set in squeezer

Rivets completely driven with angled set.  Shop heads showing.

Finished trailing edge.  Nice to have this done.