Aileron and Flap Rigging

Time: 8 Hours

This weekends task was to finish up the fuel connection lines from the fuselage to the wing tanks and rig both the ailerons and flaps. The fuel lines consist of a connection for the vent line and a connection for the fuel feed. Since I had used flop tubes, for inverted flight, I had a little bit different fuel feed line vs the standard pick ups. The lines have to travel through the hole that was drilled in the tank attach brackets. They will also have a union in the line where the standard ones don’t. The vent lines just have to clear the brackets staying below the skin level so they will be hidden under the flashing that will get put there. I made the lines and their connections minus the end that goes on the fuel line that comes out of the fuselage. That will get cut and flared after the wings are removed to make room.  

   Once I had the fuel lines done I moved on to the big task of rigging the ailerons and flaps. First up is to attach the ailerons to the wings and set the neutral point. I used a digital level which has a magnet and stuck it to my control stick to get perfect neutral stick. 

 With the stick in neutral I adjusted both of the ailerons so that they were in their neutral position. This is done by aligning three tooling holes in the outboard rib and the aileron tip. When all three line up the aileron is in neutral position.  

  Once I had both ailerons on and adjusted to be in the neutral position I had to make adjustments back at the control stick to return it to the neutral position. This is done by adjusting the rod ends on the two pushrods the connect to the control stick.  Once the ailerons have been adjusted you can move on to the flaps to line them up.  Before doing this I put in the aileron judgment tool the Vans gives you to hold neutral position. This is a jig that has a hole in it for the aileron rod bolt to go through and a flat surface to sit against the wing spar. When installed the bell crank is in its neutral position but also holds the ailerons from moving.  With the jig in place I know that ailerons will not move and I can adjust the flaps to match them. The flaps need to line up with the ailerons so that as you look down the wing in neutral position the ailerons and flaps trailing edge is lined up in a perfect line. To do this with the flaps you just adjust the pushrod either up or down to get the flaps to line up with the ailerons. Before you can do this you need to enlarge the hole in which the pushrod it goes up-and-down through.  
   You need to open this whole up as when the pushrod goes up-and-down it’s geometry changes moving the pushrod forward and aft as it moves. Once you have this whole opened in the pushrod no longer hits the skin you just adjust its length to align the flaps trailing edge with the ailerons in there up position.  
 With the flaps adjusted both left and right I removed the aileron jig to check their travel in the up and down position and compare to the degrees that vans specifies.   
 All the measurements were dead on and perfect!  One thing I did find with my flaps was that I did not bend the rears are flange enough when I built the wings. This caused the wings skin to curl up just a little at the aft end of the top skin. Vans knows that this is an issue for builders and describes how to correct this with a 2 x 4 jig. I took a 2 x 4 and cut a slot in it and drilled out the center in order to bend the flange without bending the skin as I do that. 

 The idea is that the slot would allow the 2 x 4 to slide over the skin at the very tip I opened up the slot a little to slide over the rivet heads on the rear spar flange then I could use the 2 x 4 to slowly bend the flange down in turn lowering the skin. 

   This worked out well and I will do a little more tweaking on it to get it perfect. What is fun is that I can make the flaps go up and down using a 9 V battery with it’s flat motor. Kind of fun to see things working like they should!

Rods Finished

Time: 4 Hours

I forgot to post my work from yesterday so at lunch today I figured I better finish this write up. I had plenty of work to do around the house to get it cleaned up as my girl was arriving for a show that she is working in Chicago. When I got done with that I got a few hours in before having to go get her at the O’Hare airport. First task was to prime the long pushrods before I could rivet them.

While those were drying I turned my attention to riveting the smaller rods. They have 2 rivets per end at 90° to each other. Van’s calls for AN470-12 rivets here which are pretty long. I have read where other builders have had problems with the tail tipping over during the squeezing of these. They recommended going down a size to a -11 which is what I did. You have to go slow and control the squeeze as it’s real easy to tip them over. I know this as I did it to two of them! Good thing that drilling them out was not a big deal as the rod pieces are steel and don’t enlarge very easy. Taking my time proved to be the key to successes.

With both rods riveted I screwed on the end bearings and adjusted them to the required length as labeled on the plans. I then attached one end to the aileron bracket and the other to the bell crank.

Now was the time to get the aileron in alignment so that it is a neutral position with reference to the wing structure. Two tasks you need to do to complete this. The first is to get the bell crank in a neutral position. To do this Van’s gives you a jig that has a hole that lines up this the bolt used to hole the small rod to the bell crank. When the flat side of the jig is flush with the main spar and the bolt is through the hole then the bell crank is in neutral position.

Now that we have the bell crank set neutral the aileron trailing edge should be in the neutral position as well. To check this we use 2 of the tooling holes that are in the outboard wing ribs. You drill a hole for and AN3 bolt in both spots on some straight edge, I used a 42″ aluminum ruler. Then drawing a line on the top of those 2 holes as well as the bottom. This gives you 2 parallel lines from the two holes extended to the end of your straight edge. The aileron will be centered between these two lines when in neutral position. If they are outside of the lines the. You just make the required adjustments to the rod ends to get it centered.

I repeated this process on the other aileron and now have them aligned neutral when the bell crank is neutral. The last item I did was to blind rivet the ends on the longer push rods after the primer was dry.

Ailerons Mounted and Push Rods Started

Time: 5 Hours

Now that the flaps are done I needed to start to assembly of the control surfaces onto the wings. First item was to mount the aileron bell cranks to the main spars. These bell cranks transfer the motion from the control stick in the fuselage 90° towards aft and the ailerons. They are powder coated steel and rotate around a brass bushing.

I first cleaned up the top and bottom of the bell crank tube where the bushing slides into. I then made a measurement on the tube and the bushing. Van’s calls for the bushing to be 1/64″ to 1/32″ longer than the bell crank tube. I used the scotch-brite whell and sand paper to get the length perfect. The bushings were a little tight inside the tube so I put the bushings in my drill press and turned it on while using some 400 grit sandpaper to hone them down until they slid nicely into the tubes.

Now I had to ream the inside diameter of the bushing to accept the 1/4″ bolt that goes through it. I just placed the bushing in my padded vise and used the reamer in my hand drill. It work pretty slick and the reamer just guides itself and is always centered.

I then assembled the bell crank pieces that will hold the push rod from the bell crank to the aileron. For this I had to cut a spacer from some stock that they give you.

I bolted the bell cranks back into position on the spars but didn’t torque them as I’m not sure if I will have to remove them later. I had originally torqued and sealed the 2 brackets that the bell crank bolts to on the spar back when I was working on the spar but relieved that I needed to remove them to install the bolts for the bell cranks.

With those back on I moved my attention to mounting the ailerons. The ailerons are connected at 2 points on the wings, 1 bracket on each end. They use a combination of bolts, small washers, a large washer and a spacer similar to the bell cranks. The ailerons need a travel limiter, a physical stop so they don’t travel to far and cause damn he to them or the wing skins. Van’s has you make a small angle piece and rivet to the leading edge rib of the aileron. This angle will eventually hit the aileron bracket as it moves closer to its full travel. When it hits that’s the farthest the aileron will travel. My buddy Glen had a much better design that he used on his first RV-8 and repeated it on the one he is building now. What he did was transfer the contact point of the stop from the angle that’s on the rib to the spacer that’s in the bracket on the aileron. Clear as mud? Let me show you in pictures. Normally the stop would happen prior to the spacer hitting the bracket, around 1/8″ as you wouldn’t want just the spacer to be the limiter as it is just aluminum tubing. Glen used a piece of delrin tubing, it’s like plastic to me, and cut it to match the length of the spacer. He then reamed the inside so that the spacer would slide into it. Now when the aileron travels it will hit this new soft covering of the spacer and stop the movement. I first cut the space and made it perfect then I cut the delron tubing to match and reamed it to final size. I then assembled it all together as the plans show along with this new part.

That white spacer will come in contact with the bracket on the spar and stop it’s travel. Glen said this work great and it was super easy to make and install. You can see in several of this photos the various washers and how tight they are. I bought a set of washer wrenches to help with inserting these. They are just thin stainless steel wrenches that have various sized ends that hold washers by spring pressure. You then can slide them into place and when the bolt is inserted pull on the wrench and they pop off.

Again I didn’t torque any of these as I’m not sure if they will need to come off later. I then turned my attention to the push rods for the ailerons. There are 2 per side, one short steel one that goes from the bell crank to the aileron and a larger aluminum one that goes from the fuselage controls to the bell crank. I cut them with my pipe cutter to the length described on the plans. The shorter ones are cut to 23 13/16″ and the larger ones to 69 3/16″ for the RV-8. The plans give you call outs for several different models. Once cut I cleaned up the ends and the insides so that the rod ends would slide into them easily.

I repeated this process for the larger tubes which were a little easier to cut since they are aluminum.

The large rods get riveted to their ends by 6 rivets. 360° divided by 6 is 60° so I downloaded a protractor online and printed it so that I could create a template to make the rod ends.

I used the template to mark all 4 ends of the 2 rods and grabbed my jig I bought from Harbor Freight to drill them. After I bolted the jig down and made all the required adjustments I drilled 3 holes and went completely through the rod making all 6 holes. I started with a #40 bit and used my #30 reamer to enlarge the holes.

I then moved on to the smaller rods in the same fashion. These just use 2 rivets per end at a 90° to each other. Since these are steel I sprayed a bunch of primer inside and rolled them around to get the entire inside covered.

That’s where I decided to call it a night. I should have a few hours in the Hangar tomorrow.

Right Aileron Complete

Time: 5 Hours

I had an early flight this morning and was a little tired when I finally got home but wanted to get the right aileron finished today. The process was the same as the left aileron so I won’t go into every detail as I did for that one. I will add that forgot to mention on the other aileron that I used my edge roller on the top and bottom of the leading edge skin to help these sit flat on the main skins after riveting. I also got out my pneumatic rivet puller and did the repairs on it that I knew it needed from a couple of years ago. This was a tool from Harbor Freight and haven’t used it in a long time. My reasoning for using it today was that I could barely squeeze my manual puller after all those blind rivets I did in the left aileron. I hurt muscles that I apparently never use! It took an hour to fix the tool but well worth it as it made quick work of the CS4-4 rivets. Here are a few pics from today’s work. Now on to the flaps!

Left Aileron Complete

Time: 6 Hours

Today’s task was to get the left aileron buttoned up and riveted while watching game #2 of the Blackhawks vs Wild. I had prime red all the parts last night before heading out to dinner so they would be ready for today.

First thing to do is rivet the spar reinforcement plates on both ends of the spar. There are only a couple holes you can do, the 3 inner one on both ends, as the rest will be done in sequence with the forward and main ribs. You also can rivet the nutplate on the inboard end. This is needed as the 3 bolt for the inboard aileron bracket will be inboard of the main rib and you have no access to put a nut on it.

The leading edge ribs are then blind riveted to the counterbalance.

I then put the counterweight/ribs into the leading edge skin. I then slid the aileron spar into the main skin and the attached it to the leading edge assembly. I only clecko’d the top side of the skins to the spar as I need the bottom skins open to rivet the top skins. I set this aileron on the shelf for a while so I could work on the right aileron. I did this because I need the 2×4’s I used for the counterweight drilling to make the next jig for the riveting process. The right side is done with the same process as the left. All parts were assembled to match drill including the counterweight. The countersinking was done by sight again.

The riveting process for the aft skins is to lift up the bottom skin enough to get a bucking bar inside the skin to access the spar. To aid this I have seen other builders some 2×4’s to make brackets for you to screw down the aileron and hold it securely so you can rivet.

I bought a new bucking bar that was 1″x1″x6″ with a angled end and a squared end. The angled end was too steep so I ground the squared end to a good angle. I then wrapped it in tape to protect all the parts from getting scratched. Here you can see how it fits and how you rivet the top skin.

It took me about 30 minutes to rivet the total line of rivets and they turned out real nice.

You then rivet the top of the leading edge ribs and slide in the 2 main ribs and rivet their top holes along with all the rib to spar holes. You can then bolt on the aileron brackets and torque them.

So you then flip the aileron onto the top so the bottom is available to work on. The first task is to rivet the counterweight with the blind CS4-4 blind rivets.

The plans say that you need to weight down the bottom skin to keep it flat as you rivet the skin. I decided to use a couple of flat shelve boards and clamps to keep the skins flat. Then you can rivet the bottom skin to leading edge and main ribs.

I then riveted every other hole of the leading edge skin, main skin and spar holes with the same CS4-4 blind rivets and then the remaining holes.

That’s the left aileron all done! Now I need to finish up the right one tomorrow. Most of the prep is done on it except the edges of the leading edge skin and priming. I couldn’t resist and had to put the aileron in the wing to see I what it looks like! Fun weekend in the Hangar.