Stiffeners clecoed to the Rudder Skin

If you are confused from the previous posts about the siffeners and what they are used for, perhaps these last pics will help clarify. Here they are clecoed to the skin on one side. When the rudder is finished each side of the skin will have its own set of stiffeners. You can see how they taper to a small point or edge as they move further back towards the end if the rudder, and are wider at the front. The angle is used to counteract any torsion moments of the skin, and is the real reason why the term stiffener is used. If you simply applied a strip of aluminum without the angle to the inside of the skin, you would not get the same stiffening quality that is needed here. As more of the rudder comes together you will see how these parts interact with the rest of the structure.

Smoothing the rough cut stiffeners

Here are some pics that show the finished stiffeners after smoothing all the edges on the Scotch Brite wheel. What an amazing tool for working with aluminum. Sometimes the chemical folks come up with the some really amazing things to benefit mankind. Dangerously jagged edges are all made as smooth as a babies bottom. The corners are rounded, and the parts are completed.

The idea here is that the stiffeners must conform to the tapered shape of the rudder. (Small at the tip or trailing edge, and much wider at the front. The rudder is actually a very complex shape that contains multiple tapers from top to bottom as well as in width from side to side. So the stiffeners must be very small at the trailing edge where they essentially come together with both sides of the skin, and they then widen out as the skin gets wider towards the front.

Trimming Stiffener Cont'd.

This is a pic of the safety glasses, ear plugs, dremel tool, and the scrap aluminum pieces you end up with when you are done cutting all 16 stiffeners. Note how sharp looking these are. it is important to clean these up and ensure that they are picked up off the floor as soon as they are cut. I could think of no useful purpose for any of this scrap material, so it ended up in the 86 files (trash). Recyclers will now respond and attack me "En masse" for doing such a foolish thing. So it goes I guess.

More on trimming the stiffeners

The process to trim them is basically to secure the angle to the work bench with the clamps. I absolutely must use two hands with the dremel tool in order maintain control of the tool while it cuts, so it is imperative that the clamps are positively securing the work. If you even suspect that the part is starting to move, turn off the tool and re-clamp the piece before continuing. You line of the cutting wheel so that it si just outside of the trim line for each cut.

I basically started with the cuts that separate each stiffeners from the angle stock, and then reclamped each one individually to make the angle cuts on the flange and do the final trimming. Using the Dremel tool makes this process go quite quickly, but it is also very easy to make a mistake. The key, as with all things about this process, is to take your time and follow the same process for cutting each one.

Tools, Safety, and Trimming the Stiffeners

I used my dremel tool to cut the stiffeners from the aluminum angle. Other tools included clamps, Safety glasses, ear plugs, and several REINFORCED dremel cutting wheels on the standard Mandrel. Do NOT use the small standard NON-REINFORCED cutting wheel as these will shatter as soon as you hit the aluminum. The reinforced cutting wheels will work fine, but you will go through at least 4-5 of them in the process of trimming all 16 rudder stiffeners. The wheels dissipate quite rapidly when cutting the aluminum, so you will need several of them. You MUST where safety glasses and ear plugs, and, as I found out the hard way, even some gloves to keep from burning yourself on the hot dremel tool.

The last thing you need is tiny shards of aluminum in your eyes. Believe me, there are plenty of them hitting your face as you cut the metal. If you are less inclined or do not possess a Dremel tool then a good hack saw or metal cutting blade will work fine. I set my Dremel to a 9 power setting (Almost full speed). I did not want to experiment with a slower setting for fear of binding the aluminum causing the wheel to jump and cut things other than those you originally intended to cut.

Marking the stiffeners

Here is a series of pics that shows the various markings to be made in order to trim the stiffeners from the aluminum angle. You can see the semicircle notches that Vans made and the lines drawn to connect the marks to create the correct trim lines for each stiffener. The only thing I did not like about this process was that Vans attempts to show this in their plans with the angle drawn "flat". They say this is for "clarity," but I found this to be quite confusing. They really need to show a better diagram so that you can understand how the trim lines need to be drawn. Nevertheless, I managed to figure it out.

More on Rudder Stiffeners

In my research, I found that any detail concerning the fabrication of the stiffeners for the rudder and elevators is woefully lacking on most builder sites, so I am attempting to fill that void by providing a bit more detail. This pic shows the labels forsome of the stiffeners, which are labeled from A through H. There are eight per side, for a total of 16 for the rudder. All 16 had to be trimmed from the angle provided from Vans.

The stiffener basically "stiffens" the thin rudder skin to keep it from flexing to much. The only ribs for the rudder are the two end-ribs, one on top adn one on the bottom. I'm not totally certain why the rudder does not contain a more robust skeleton made of fully formed ribs from end to end, but perhaps this has to do with the fact that this is a critical moving part of the aircraft that controls a force called yaw, or the left and right turning capability of the airplane. Perhaps hard formed ribs that would attach to both sides of the rudder skin may be subject to failure and cracking due to the amount of force that this surface will endure over time. It could also be related to weight concerns, since this is the aft-most structure of the entire airplane, and therefore has a large affect on the center of gravity.

165 hours - Starting on the Rudder and finishing the VS

Items 1 through 6 on my previous post have been completed. All that remains now is to clean, prep for primer, clean again, prime, and slam the rivets together to complete the VS. I had to buy some more primer yesterday and spend some time doing early Xmas shopping as well. I wanted to finish the VS over the Thanksgiving weekend, but it did not quite happen. Instead, I spent a lot of time reviewing other builder sites and VAF posts to learn more about creating the stiffeners for the Rudder. I also and actually managed to cut, trim, and smooth the edges of all the rudder stiffeners. Here is a pic of the angle aluminum that the stiffeners must be trimmed from. They are about 3 feet long and contain special pre-punched markings that define where the angles of the flanges need to be trimmed.

155 hours Continuing with VS

Trimmed the vinyl off of the VS skin and almost finished deburring all the holes in the skin. The ones closest to the leading edge are always hard to get to so you usually end up using a scotch brite pad to debur those holes because the deburring tool is too big to slide in between the skin halves. Rib flange holes that line up with the holes in the skin are all dimpled.

Only things left before I can rivet the VS together are:
1. Dimple holes in skin using the squeezer and c-frame
2. Dimple leading edge rib holes that I can't get to with the squeezer by using the close-quarter tool.
3. Clean up the edges of the front and rear spar and the skin
4. Finish edge -deburring the spar doubler that strengthens the rear spar. The forked ends on one end are a bit challenging because you need to debur the edges at the base of the fork. I have a method in mind uaing 220 aluminum oxide sandpaper and a dowel that I can use to make a sanding block to smooth the remaining edge. It's too thick for a scotch brite pad and I can't use the wheel to get into this area. This part was stamped out of a very thick piece of aluminum and contains very sharp edges, so it is important to debur the edges so that they do not dig into the rear spar over time.
5. Counter sink the holes in the spar doubler where the rivets will join the doubler to the rear spar. (22 holes to do)
6. Dimple the matching attach points on the rear spar where the spar doubler will be attached.
7. Prime the parts
8. Rivet it all together

More VS pics

The VS goes together much faster than the HS. Less parts, less drilling, less everything. Here is a series of pics that shows what it will look like when it is all riveted together. First is the rear spar with the bottom rudder hinge and the spar doubler in place, which is a thick piece of reinforcing aluminum that provides support. Second is the VS all clecoed together - it's not really all that big. Last is another shot showing the full length of the rear spar with all three hinges that will attach the rudder (as soon as I build it anyway!) On thing that I found interesting is that the rudder is actually a relatively complex shaped part. It tapers in all dimensions as it goes from the bottom to the top. The rudder is a bit thicker on the bottom and not quite as thick on the top, so the bottom hinge is actually slightly longer than the other two hinges to account for this difference in the shape of the rudder from one end to the other.

154 hours VS work continues

Ribs, spars, rudder hinges and skin for the VS are match/final drilled, deburred, and almost all holes are dimpled except for the skin. I have to break out the soldering iron with the rounded tip again to trim away the vinyl covering that protects the metal from scratches. Then I'll need to rig up the C frame again to dimple the rivet holes in the skin.

Here is yours truly working the drill while I match drill the holes in the rear spar with everything clecoed together and clamped to the bench. Rule number one is always secure the work! I clamped the rear spar to the bench, and also clamped a small block of wood on the back side of the spar where each of the three sets of hinge brackets are located. I did this for several reasons: The hinge brackets are made of steel, and are therfore much harder to drill through.

I applied a lesson that I learned during the HS assembly where I tried to drill the hinges without having a solid backing flush against the hinge. The resulting holes were quite rough, and had to be deburred quite a bit. The compressed block of wood against the hinge bracket ensures that the drill bit maintains a consistent tension as it goes through each of the holes in the aluminum and the steel. The only trick was to use a size of wood that would cover the hole in the hinge bracket and slip in between the clecoes holding it in place. It worked well, and the holes in the rudder hinges came out much cleaner this time.

150 hours back on the build again

Just when you thought I had vanished off the face of the earth, I'm back! After a summers-worth of home projects, and hunting season all but over, I finally manage to start working on the plane again - just in time for the cold weather! So to pick up where Ileft off, after Oshkosh 2010 I had repaired my blunder on the HS, but I still had some doubts about the fit of the end rib to the rear flange on the right side. There was a small gap that indicated that the flange was not quite seating properly. This is a structural concern and I finally stopped wrestling with the decision and decided to drill out the 2 AN470 rivets and do them over again. Read the series of posts about my major repair and you'll understand why I was hesitant to try to drill out any more AN470 rivets. This pic shows the gap. I was able to refit this and close up the gap successfully, and re-do the last flush rivet on the end of left side that I had also messed up, and now the HS is hanging up on the wall above my work benches, waiting on assembly with the fuselage someday down the road.

Here is the 8'4" long HS for my RV8. Just needs some fiberglass tips on the ends that I will install later. I'll probably pull it down again when my elevators are done just so I can test fit them to the HS and dream about the day when it's time to attach them to the fuselage for the very last time.

Now on to the Vertical Stabilizer, or what most folks call "the tail" or "the fin." You can see the frame or skeleton of the VS on the table just to the right of me. More VS pics will follow..