Archive for category Empennage
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.
1.0 Hours -
Today, I was able to fit the left HS tip, construct the wood rib for it, and bond both the ribs to both tips. This time, I decided to bond the ribs in place while the tips were clecoed on the HS. Since the tips deform quite a bit when not clecoed in place, I was worried that the fit may not be quite right if I removed the tips and bonded the ribs outside the HS. Once the flox set, I removed the tips and laid a fillet of flox around the inside joint of each tip/rib combo. Tomorrow, I’ll reinforce them with some glass.
On a more positive note, about one more month until my wings arrive. Hopefully, when it comes time to order the fuselage, I’ll be able to save the money earlier and not have a construction gap after the wings are completed.
1.0 Hours -
The HS tips require the most work of all the empennage tips. Since some metal is cut from the end of the stabilizer to accommodate the elevators, an equal amount of the HS tip also has to be removed. In addition, the horizontal stabilizer is not pre-punched for the tip attachment locations. This is the only part of the empennage where an entire row of rivet holes is missing. Like the VS tip, the HS tips are also open ended and I will need to make some wood ribs to close them off.
I started by trimming the tip. Using my Dremel, I cut about 0.2” from the flange, and removed over an inch from the aft end to allow the elevator to swing. Being cautious, I made sure to remove less than required from the aft end. It’s much easier to sand it down the rest of the way than to rebuild it with fiberglass.
Next, I needed to measure and mark the horizontal stabilizer for the tip attachment holes. Since the flange on the tip is 0.5” wide, I decided that my rivet holes should be 0.25” from the edge of the HS. Drawing this line was the easy part. Now, how do I decide on the number of rivets to use to attach the tip and how far apart do they need to be spaced?
After looking at the other empennage tips (all of which have different rivet spacing), I decided to place the first rivet 1” from the leading edge and then place three more rivets at 1.25” intervals for a total of four rivets per side. Once I marked this pattern, I used a center punch and then drilled the holes to #40.
Another difficulty with the HS tips is that they are not quite wide enough. If I clamp one side to the HS, the other side is almost a half inch from the flange. However, they do easily stretch to fit the HS. With this in mind, I clamped both sides of the tip in place and started match drilling the tip to the holes I had just made in the HS. As with the other tips, I drilled my first hole, then carefully re-checked the fit before moving on to the next hole.
Once all the holes were drilled and the tip was clecoed on, I attached the elevator to check how much more of the tip would need to be removed. Fortunately, not much! The aft end of the tip will require a bit more sanding in order to make a nice, even gap the entire length. The elevator tip also sticks out a bit more than the HS tip. To fix this, I’ll probably put a layer of micro on and then sand it to shape so that it is even with the elevator’s tip. On one builder’s site, I saw that they actually closed the entire HS/elevator tip gap with micro, sand the final shape, then re-cut the gap with a saw. I may try this as well.