Adam Thomason's
RV-8 Build
... and other aviation related things
Welcome to my website documenting my RV-8 aircraft project. Below you will find entries discussing my progress along with pictures. Make sure to check out the menu bar at the top for other pages on this site as well.
Contact me: awthomason74@gmail.com
Project Current Status
Blue assemblies are completed.
Red assemblies are currently in progress.
White assemblies are not started.
1/8/19 - Horizontal Stabilizer
Over winter break I was able to finish up the horizontal tail. Now the entire tail is complete except for the elevators, which I plan to complete this coming summer. I was also busy doing some work on my composite rudder project, which I had briefly mentioned before. I moved that project to its own separate page on this site, so make sure to keep up with that if you're interested.
I have also added a questions and comments page, so feel free to browse or contribute to that. Unfortunately Google Sites doesn't make it very easy to do that, so the format is a bit weird.
I was really busy trying to cram all this project work in over winter break, so I'll just leave the pictures below. It was very close to the construction of the vertical stabilizer, just with two surfaces sharing a rear spar and joined at the front spar.
7/21/18 - Rudder
Today the rudder was completed. This will be the last bit of work I do until I get back to Indiana and find time to start on the horizontal stabilizer. Another milestone complete, many more to go!
First, the skeleton was deburred, dimpled, primed where appropriate, and then riveted together.
Next, I fixed the skin so that the skin is completely flat all the way up to the trailing edge radius. You can see here where the skin used to dive away from the straight edge, it's now flush right until the bend.
I then put a big dab of RTV at the end of each stiffener right before riveting everything together and closing out the structure. This is a known crack-prone area. After years of vibration, the stiffeners push into the skin and can produce cracks near the trailing edge of the skin.
Then, on went the skin! It was all pretty easy riveting and I could use the pneumatic squeezer for pretty much all of it, making it a quick and painless job. Since there are only stiffeners and no internal ribs or spars, I didn't have to wedge my arm inside with a bucking bar like I did for the vertical stab.
The counterweight then went in next. Sticking a big hunk of lead in an airplane just seems wrong! However, this is necessary to prevent flutter, which is a very complex phenomenon that happens to aircraft control surfaces. Flutter will destroy an aircraft in a matter of a second or two, well before the pilot can do anything about it. It has to do with a thing called "aeroelasticity" and inertial forces. Check out this video and this video showing what happens. Adding the counterweight is a method of flutter mitigation called "mass-balancing" where weight is added forward of the rudder hinge line, to compensate for the weight trailing the rudder hinge line, which modifies the resulting inertial forces that cause flutter. Below you can see the nutplate strip I made, which will let me tighten the screws from the underside of the rudder horn, without having to remove the fiberglass fairing that will close out this whole tip area.
Next the leading edge of the rudder was bent. This required a bit of patience. I used a steel tube duct taped to the skin, and rolled the tube inward toward the spar. This gets it fairly close, but I still had to wrestle with is to get the skin to meet and put clecos in place.
After match drilling and deburring, the clecos were exchanged for rivets and the rudder is complete.
Below you can see where the blind nutplates are on the closed out side of the rudder spar. Rod ends screw into here, which are then bolted to hinge brackets on the trailing side of the vertical stabilizer spar. I laid the rudder next to the vertical stabilizer, and it looks like they'll fit together nicely! Good thing, right?
7/8/18 - Rudder
All of the rudder skeleton parts were trimmed, fitted, and temporarily assembled today. As you can see, there's not as much to the rudder skeleton structure as the vertical stabilizer skeleton, since there's lots of stiffeners on the inside of the rudder skin. The bottom of the skeleton is pretty stiff. That's where the rudder cables will attach (at the thick aluminum angle piece) and will take the largest stress concentration in the rudder. Most of the moment produced by aerodynamic loads will transfer through here.
There are three nutplates that will be riveted to the aft side of the spar, and will be closed out and inaccessible once the skin goes on. This is where rod ends will screw into, and be bolted to the three hinge locations on the aft side of the vertical stabilizer.
The skin was also clecoed onto the structure today, which meant, for the most part, all of the parts I brought out to California with me were used at this point. No random parts still laying around when everything is assembled is always a good thing! Next up will be some match-drilling, followed by disassembling, and a marathon of deburring.
Here you can see that the trailing edge of my rudder is slightly under-bent from the process in my last post. The skin should be flush with the straight edge all the way up to the point where the tight radius of the edge starts. You can see the skin diving away slightly before the edge starts. This is only seen when the skin is all attached to the skeleton. Surprisingly, small deviations from design on the trailing edge of control surfaces like this can make large differences. The trailing edge shape plays a big role in the force required from the pilot in order to move the control surface. Another adverse effect from a poorly bent trailing edge is a tendency for the control surface to oscillate back and forth, we don't want that! This will be corrected once the rudder is all riveted together.
7/4/18 - Rudder
Today, Nick Bain, an Aerospace Engineering student at MIT and fellow intern at Scaled, came over and helped me out for a bit. I built the fixture that is used to bend the trailing edge of the rudder and elevators to a precise radius. This is just a couple pieces of 2x8s with a couple door hinges. It took a little bit of trial and error to bend the rudder skin to both the correct angle and correct bend radius. We eventually got it right after moving the skin away from or closer to the hinge line of the tool to tweak the bend radius.
6/23/18 - Rudder
This past week I started on the rudder. This angle stock below was cut to length, and tapered so that it will fit in the trailing edge of the rudder once the rudder is completely folded over. These are stiffeners and will keep the skin rigid without the need for too many ribs. Once cut to size, they were match drilled to the skin.
After all the deburring and dimpling, rivets were taped in the holes and the stiffeners were back riveted in place. In the last picture the stiffener taper is obvious to fit inside the trailing edge.
6/15/18 - Vertical Stabilizer
After about 30 hours, I'm done with my first major sub-assembly! Riveted the skin on, 205 rivets today. I managed to not put any big dings in the skin with the bucking bar and I'm happy with how it turned out. On to the rudder!
6/13/18 - Vertical Stabilizer
Riveted together the skeleton yesterday. The rivets holding the bottom ribs to the front spar were a 'yuuuuge' pain. The ribs are at angles, making it very awkward to get a bucking bar in perpendicular to the rivet face. I think I drilled out 4 rivets for the 3 that ended up being set. The squeezer wouldn't fit in with the geometry of the assembly down there.
Today I finished up those last rivets with some help from Nigel. Then the skin was clecoed in place and will be riveted on next. The rear spar, seen in the last picture, will slide into place and be riveted in to close out the stabilizer. This is done afterwards so a bucking bar can get inside the assembly to rivet the skin to the front spar and middle rib. The top and bottom rib flanges face outward and are easily riveted with a squeezer.
6/9/18 - Vertical Stabilizer
Ribs are primed and will soon be ready for the stabilizer assembly. I used Tempo rattle can aviation primer, which was quick and convenient for a small batch of parts and without the hassle of setting up and spraying a two-part primer. I had a choice of yellow or green primer. Coming from a racing background, painting things green is considered bad luck, so I decided to play it safe and went with yellow.
The dimpling vice grips ended up working out really well and didn't even need to be ground down. They produced dimples of much higher quality than the "pop rivet dimpling" technique.
6/6/2018 - Vertical Stabilizer
Today all of the holes in the skin were deburred and then dimpled.
6/5/2018 - Vertical Stabilizer
Realized I made a stupid mistake already. I'm sure the first of many.. I riveted the spar doubler to the spar without dimpling the holes on the spar caps (sides) where the skin overlaps first. In the first picture you can see the pneumatic squeezer fits just fine without the doubler in the way. Of course the second picture shows my trouble. I can't get any tools far enough down to dimple these holes. So I called my dad back in Indiana where all my tools are. The guy I bought all my tools from had some special vice grips that are modified for dimpling. You can see the die for dimpling the #30 holes is already ground down. Looks like he ran into a similar problem! So these are being shipped to me and I'll have to grind down the #40 dimpling die. I'm thinking this should solve my problem.
6/3/2018 - Vertical Stabilizer
Finished riveting together the aft spar. For scale, the spar is about 4.5 feet tall. The white hinge brackets will be where the rudder attaches. You can see the difference between the universal and flush rivets in the second photo. Now I'm waiting for primer to arrive so I can prime the ribs. The majority of the aluminum alloy sheet metal parts in the kit are "alclad". This means that there is a thin layer of pure aluminum on the surface of the alloy. This layer forms aluminum oxide, which is corrosion resistant. However, the vertical stabilizer ribs are not might not be alclad (part index lists two possible materials) and should have some form of corrosion protection.
6/2/2018 - Vertical Stabilizer
Below are a couple examples of the tedious "deburring" process that every part goes through. The photos show a hole and an edge before and after being deburred. Holes have a slight burr around the rim from match-drilling. This burr is removed using a tool that's basically a large drill bit, which slightly chamfers the edge. this allows parts to fit tightly together when riveted. As seen on the in the photo with the rough edge, most parts have tooling marks and sharp edges from being sheared at the factory. This must be smoothed and rounded to reduce possible stress concentrations in the part. Over time, imperfections on part edges will be the first place a crack will start.
The front of the bottom section of the vertical stabilizer spar must be flush because it will mate flat against part of the fuselage (~4 years from now). This means that the parts must accommodate flush rivets in this area. For the thinner spar, this means using two dies that squeeze a "dimple" into the material, as seen in the first photo. The spar (second photo) is a bit thicker and must be countersunk. This allows the two parts to be sandwiched together with interlocking holes that will accept flush rivets.
You can see the section that was flush riveted, and will eventually sit flat against other parts. The second photo shows the back side of the spar, and the formed head of the rivets. The rivets are squeezed down to hold the parts together. These rivets were all set using a pneumatic squeezer. At first I tried to use a method of riveting called "back-riveting". The tails of these rivets are quite long and the rivet squished to the side rather than straight down. That rivet was drilled out, and the pneumatic squeezer did a much better job. The last photo shows a universal head rivet as opposed to a flush rivet. These are used on the rest of the spar assembly since they don't require dimpling or countersinking. When finished, my airplane will have a total of about 16,000 rivets. I've got a few more to go!
6/1/2018 - Vertical Stabilizer
Today I got started on the vertical stabilizer. This included using quite a few clecos, which are temporary fasteners to hold the parts together. The parts are assembled with the clecos, leaving about every other hole open. The holes are pre-punched in the parts are not quite full size for the rivets, and require "match-drilling" to final size. The ribs, along with all other components eventually, require a bit of "deburring" which involves using different methods of filing and sanding to round all edges of the sheet metal. This ensures there are no sharp edges or corners in the parts that will induce stress concentrations, and possibly form cracks. The assembly starts to look like an airplane part, but once all the holes are match-drilled, the entire assembly will come apart again so that all of the holes in the skin can be deburred along with the spars.
5/31/2018 - Work Space
My work space is set up and ready to go with all parts and hardware organized and ready for building. My work table is just big enough for the vertical stabilizer and rudder, which is all I brought to California this summer. Nigel is letting me use all of his aircraft tools which makes it much more convenient.
5/25/2018 - Practice Kit
Finally getting settled in for the summer in Tehachapi, California. I'm staying with Nigel Speedy, an instructor at the National Test Pilot School in Mojave, and a contributor for Kitplanes Magazine. He has also built an RV-8 and has been getting me started on my tail kit. I recently completed a practice flap kit, which I messed up in a few places. I had the rivet gun at way too high of a pressure, and thought it was just my technique. Oh well, that's why its a practice kit. Now time for actual airplane parts...
5/5/2018 - Inventory
Empennage kit arrived! The parts were inventoried, and then the vertical stabilizer and rudder components were separated to be shipped off to California with me for the summer.
