Archive for category Empennage
1.0 Hours -
The goal for the day was to finish attaching the horizontal stabilizer to the fuselage. Since only four holes needed to be drilled, this should have been an easy task…and it was.
First, I had to take a few measurements to insure that the horizontal stabilizer’s incidence was at 0°. With the 3/16″ spacers under the aft spar, the incidence should be set, but the distance from the aft deck to the tooling holes in the inboard ribs of the horizontal stabilizer ribs can be used to confirm the incidence. There are several tooling holes, and the distance was equal on all of them. Therefore, 0° incidence.
With the incidence set, it was just a matter of drilling four holes through the F-711C vertical bars and aft spar of the horizontal stabilizer. Nothing complicated here. Access was easy, and there is a ton of material in this area, making edge distance concerns negligible. I drilled the holes to #30, then to #19, before finally reaming them to the appropriate diameter for the AN3 bolts.
Of course, as soon as the horizontal stabilizer was installed on the fuselage, it had to come back off. There were two reasons for this. The first is that I need to fit the elevators and drill the elevator horns for attaching the push rod. Second, the elevators, and all of the other empennage parts have been stored in our attic, and, with the horizontal stabilizer attached to the fuselage, there just isn’t enough room in the garage to gain access to the attic.
2.5 Hours -
My plan for the airplane is to finish up some of the little things now. Then, when the weather gets hot, I want to finish up the canopy. The next thing on my list of “little things” is to install the tail feathers.
First things first, I decided to turn the fuselage around so that I would have more room to work on the tail without having to move the plane halfway out of the garage anytime I wanted to do something. Although turning the fuselage around should be an easy task, my current garage setup made it a little more challenging. Our kayaks, lawnmower, and a few other things had to be moved out of the garage so I would have enough room to back the fuselage out. Once the path was clear, backing the fuselage out, turning it around on the driveway, and pushing it back in was a pretty easy task thanks to my rolling fuselage cart that has four castering wheels instead of just two.
Once the fuselage (and all the other stuff) was back in the garage, I pulled the horizontal stabilizer down off the wall for the first time in about 4 years. After wiping off some of the dust, I gave the horizontal stabilizer a thorough inspection. Since this is the first part of the plane that gets built, I somewhat expected to find some sub-par craftsmanship. However, I didn’t find anything that I wouldn’t consider passable today. So, on the fuselage it went.
To position the horizontal stabilizer, I placed all of the spacers and shims where they needed to go (3/16″ drill bits used as spacers on the aft spar), and then clamped the aft spar to the F-711C vertical bars. Then, I measured from a point on each side of the fuselage to one of the aft, outer rivets on each side of the stabilizer. If the measurements are equal, the stabilizer is centered. Of course, it took multiple measurements and multiple tiny movements to get the stabilizer’s position just right. Once positioned, I made sure everything was solidly clamped, then marked out the locations for drilling the forward horizontal stabilizer spar to the fuselage.
Normally, drilling four holes is a pretty simple task. However, the four holes that will be used to attached the horizontal stabilizer’s forward spar to the fuselage are critical holes, and half of the assembly is under the aft deck and very hard to visualize. In addition, the two out holes also go through the longerons, where edge distance is once again critical, but the part is hidden from view. After a lot of careful measurements, I decided to go for it and drilled the first hole. Edge distance was ok, so on to the next, then the next and the last. All four holes are now drilled and edge distance is acceptable all around.
Next, the aft spar of the horizontal stabilizer needs to be drilled to the F-711C vertical bars. Fortunately, these everything is visible and easy to access and there is plenty of bulk in the area, making edge distance a non-factor. However, I decided to call it a day.
0.5 Hours -
With very little left to do on the empennage, I went ahead and installed my internal rudder stop. Nothing complicated…just clamp it in place and use the holes in the rudder stop to drill holes in the hinge bracket for two AN3-7A bolts. Once drilled, I used AN3-7A bolts with two washers and a stop nut on each. Everything was torqued to 25 inch pounds, inspection lacquer applied, and done!
On another note, my wing kit shipment, originally scheduled for mid-May but delayed to mid-July, has been bumped up the priority list at Van’s. My kit went to crating on Monday and will be shipped as soon as it is all boxed up. In two or three more weeks, I should be back to some serious airplane building!
Rudder stops are another one of those RV things where you can ask 5 people and get 10 different opinions. After reading as much as I could about the pros and cons of internal vs. external stops, I decided to purchase an internal stop. At $25, it isn’t a big loss if i decide not to use it (and I can probably get $20 back by selling it to another RVer).
If following the plans as Van’s has written them, the rudder stops are pieces of aluminum angle that are riveted to the aft fuselage just forward of the rudder. At full deflection, the rudder horn will hit these stops before the rudder skin smashes into the elevator. By modifying the angle of the stops, you can alter the amount of swing in the rudder. While this works well, I think it is unsightly. Granted, the rudder cables hanging out of the fuselage are a little ugly too, but at least one ugly can be eliminated.
The internal rudder stop is simply a chunk of delrin plastic that is milled to a specific shape and drilled for two AN3 bolts. The plans for this stop are available for free on vansairforce.net, or a pre-cut stop can be purchased from Merlin Enterprises (Stockton, CA) for $25. I chose to buy the finished product since the purchase of raw material, combined with my time to make two of them (because I will screw up the first!), will easily surpass $25.
The internal stop is bolted to the top half of the lowest rudder hinge on the vertical stabilizer using two AN3-7A bolts (if I measured correctly). When the rudder swings to its limits, the rudder spar will contact the stop, preventing further movement. The down-side of this system is that some people believe the stop, when in contact with the rudder, will stress the aft-most fuselage bulkhead. However, no one has done a complete stress analysis, it is believed that the only stress severe enough to cause damage would occur only in an aggressive maneuver such as a tail slide (I’ve got bigger problems if this happens), and there are over 500 RVs that have implemented the internal stop. In my opinion, concerns some builders have are unfounded. If my rudder jams in-flight, I’ll change my opinion ;-)
0.5 Hours -
After doing bits of work here and there on the HS tips, they are finally finished for the second time! This time, I made sure to check the fit with the elevators after each step. The pictures don’t really do them justice. The flash makes the aft surface look uneven, but it is really just an effect of sand the surface smooth. When sanding, primer is knocked off high spots, leaving the white micro to show through more than it does on the low spots.
1.0 Hours -
Despite my lack of posts over the last week and a half, I’ve actually been working on the plane almost every day. However, as I’ve stated before, with fiberglass, it is 15 minutes of work followed by hours of drying time.
On my last post, I had just finished filling and priming the HS tips. They looked beautiful too. Unfortunately (or fortunately), I checked the fit one last time before riveting them on. To be sure the fit was OK, I also attached the elevators to make sure they had enough clearance. Well, they didn’t! The elevators could no longer swing because I built up the aft surface of the HS tips too much. Come on…I only had two layers of micro, two layers of thinned epoxy on top of that, and two layers of filler primer on top of that!!! The prime culprit really was the micro. I had the tips cut down to the perfect length, then filled past that with micro.
So, my once beautiful HS tips had to be sanded all the way back down to the wood rib, leaving just a bit of micro in the low spots, then re-sealed and re-primed. Now, they look just as good as before, but still have the necessary clearance for the elevators to swing. At least I’m still waiting for my wings and have plenty of time to play with these tips!
In addition, I bought and assembled a new BBQ grill this weekend. Assembly took about 2 hours. If Van’s wrote the instruction manual, assembly probably would have taken an hour max!
0.5 Hours -
This evening, I spent a few minutes countersinking the HS tips and dimpling the HS skin. Once this was done, I cleaned the HS tips with soap and water and then sprayed on two coats of primer. It looks like I may still have some pinholes to deal with on the aft surface of the tips. Once the primer is dry, and if pinholes are present, I will probably sand the primer and then add another layer of epoxy to try to seal these holes.
0.5 Hours -
Good news and bad news today.
The good news is that I sanded down the micro on my VS tip and put on a couple coats of primer. The gap filled in nicely and the tip looks great now.
The bad news is that I received a letter from Van’s stating that my wing kit shipment will be delayed. A poster on VansAirforce.net told me that there are shortages of raw material in the supply chain and some of the OEMs that Van’s contracts with are probably not able to get enough material to fill all orders. In addition to this, kit orders are way up. Looks like the economy is recovering!
So, my delivery date has been pushed back almost two months! The wing kit is now scheduled to be shipped the week of July 12th.
0.7 Hours -
Today, I was able to get another 45 minutes of work in on the HS and VS tips. As usual, now they have to set overnight before I can do anything else.
After sanding down the layer of micro on the aft surface of the HS tips, there were a lot of pinholes present. On the VS tip, I decided to layer on some more micro, but, this time, I decided just to put on two coats of straight epoxy and see if that seals the holes.
Once my epoxy was on the HS tips, I turned my attention back to the VS tip. I had piled on some micro to see if I could fill the gap on the forward edge between the fiberglass tip and the metal skin. I did a quick, rough sand on this micro, and it looks like the gap is nicely filled. I still need to do a bit more sanding, follow the sanding with a coat of primer, and the gap should be a distant memory!
0.8 Hours -
Since this is more fiberglass work, as with the last few posts, this entry covers work that occurred over multiple days. I’m combining some of these because I can’t justify writing one post for something that took 15 minutes to do and then had to set overnight before I could do more work.
The other night, I reinforced my wood HS tip ribs by adding a layer of fiberglass to the inside of the joint over the flox filet. Once the epoxy was set, I returned to the tips today and put a layer of micro over the aft face of the wood ribs. This was done in the same manner as with the vertical stabilizer tip. However, I tried to make the micro a bit thicker in order to prevent it from running down the side of the tips (it took a lot of sanding to fix that on the VS tip). This time, my micro was the consistency of thick frosting rather than a runny glaze. This thicker micro had to be spread on instead of poured, and it seems to have fewer air bubbles than my previous, runnier micro.
Once I coated both HS tip ribs, I still had some micro left over. With the extra, I decided to slather some on the gap that is present on the leading edge of the vertical stabilizer where the aluminum and tip meet. I’m hoping the micro will fill the gap and be easy to sand back to the contour of the vertical stabilizer. If it doesn’t work, I may have to glass the seam on the VS and I’m trying to avoid this.