Several little things here. First, the wiring for the electric trim-tab servo is now complete and waiting for a cable to be plugged into it. This of course will happen a very long time from now when the airplane is almost complete. But I took some time to make it easy on myself later. I bought some nice locking connectors, soldered the wires in place and mounted the connector in a spot which will make it “easy” to reach when the trim tab servo is mounted. One thing I learned is that in the future, I’m going to get a wire crimper and connectors that take crimped pins rather than the solder cups. Once the wires are soldered to the cups, it’s not possible to get the heat-shrink tubing around it. This wasn’t a problem here since I slid the heat-shrink tubing on before soldering, but in the end, I could have used longer tubing for a better look and then another, larger diameter heat shrink tube over that whole thing to give it some more strain-relief. This one is fine, but in the future, I’ll be crimping instead of soldering.
Also included the pin-out right here in this blog so that I’ll always be able to find it when I need it. I do have the sheet I took the picture of in my airplane folder, but just in case I lose it, it’ll be here too.
Then Scott and I got the elevators fully attached to the horizontal stabilizer. This was described in a previous post. It was more of the same. But now the job is finished. Both elevators are aligned and had holes drilled into the control horns, etc. They’re ready to go when we’re ready to go. One thing I had to do was figure out how many turns the bearings could be backed out and still be safe. I found out that they need to be fully engaged to the nut-plate that they screw into. That means that all the threads have to be in play, so to speak. I found this position by counting threads. There are 6 full revolutions of threads in the nut plate. This means that after 6 full revolutions of the bearing, all threads are in play. This is the point at which the bearing can’t be backed out any further. I then turned them in and counted the turns until the starting spot as indicated by the plans were reached. I counted 1.5 turns. To get the elevator to swing freely over the full range prescribed in the plans (30 degrees up and 25 degrees down) we pretty much had to back all but one of the bearings out that 1.5 turns. When I checked up on this, I discovered that many of the other builders had the same experience.
Finally, I got back to the trim-tab anchors. The plans call for these to be riveted to the cover plate. But long ago, I decided to buy better anchors (it is agreed by most everyone that the anchors supplied in the kit are pitiful – just a nut welded to a flat piece of metal). And apparently with these anchors, it’s very difficult to install the trim tab cables. So others have done similar things to what I did. I bought some self-locking pem-nuts (actually, I got them as samples from the manufacturer) and made little nut-plates to fit over the holes in the anchors. I wanted to press the pem-nuts right to the anchor, but the hole required would have been too close to the edge of the anchor, so I made nut-plates with scrap aluminum and the pems. Then I riveted these nut-plates to the anchors and voila, I have removable anchors.
Then I’m about to put the lower fairing on the rudder. Because I want to put some navigation lights back here, I don’t want to permanently install the fairing with pop-rivets. I found some people on-line who used nut-plates installed on the fairing in order to make it removable. I have all the parts and will be doing that probably over the weekend. Then it’s just build a cradle for the wings and wait for the wing kit to arrive.
Elevators are complete!!
Today I had a lot of help from three of the kids and everything went pretty smoothly. The hinges were cut to size for attaching the trim tabs to the elevators. We tried to use the mitre saw for this task, but in the end just used a hack-saw followed by the scotch-brite wheel smooth it out. The hinges were match-drilled and riveted. Then the trim tabs were positioned and the hinge pin inserted. Then the end of the hinge pin was bent in order to better secure it to the elevator so that it can’t back its way out (still have to put on the safety wire when I get some, but that’s a 2 minute job.)
All in all, I’m really happy with how the elevators turned out. There are a couple of pictures showing the elevators balanced on the bench. This gives me a good feeling. In the end, they’ll have to be balanced correctly before flying, but the fact that they don’t slam down on one side or the other has an intuitively good sound to. The trim tabs don’t look the greatest, but I believe they’re structurally sound and will be fine in the end. That said, when I have the EAA Tech. counselor over to inspect my empennage construction, I’m going to ask him to look that over carefully just to be sure.
The parts for the tailcone (aside from the skins) have been moved to the garage and the elevators into the “airplane room.” My hope is to order the wing kit at the end of this month. We shall see.
Took the four lead blocks which are the counterbalance weights, trimmed them according to the plans and installed them into the elevator tips. The bolts were properly torqued and marked.
The only thing of interest tonight is that lead gets REALLY hot when you use a belt sander on it. And it stays REALLY hot for a very long time. I started out trying to cut, or rather shave, by using a vixen file. But this would have taken forever. I didn’t want to use a hack-saw because I’d never be able to keep a line straight through the block. Not to mention the dimensions of the cuts were down to the 1/32 of an inch. So, I used a mitre saw for some of the cuts. They came out pretty good. And on two of the blocks, a large protruding area had to be removed from the surface, so I decided to put in a fresh belt and use the belt sander. It took a long time, with many, many long breaks to allow the lead to cool enough to be handled, but that part, too, came out really good.
I think one more session and I’ll be finished with the elevators! All that’s left is to attach the trim tabs.
Trailing edges and leading edges are done. I did the trailing edges of the elevators in just about the same manner as I did for the rudder. The only improvement to what I did before was rotating the angle-iron sooner and I propped the elevators up better so that there was no stress on the skins from the angle-iron while hitting the rivets. The trailing edges are as straight as a razor. I’m very pleased about this! No issues at all with rolling the leading edges. It was a little time consuming, but no problems.
The only problem I had tonight was with the aft-most rivets in the tip rips. After the trailing edge was complete, it was time to set three rivets on the top and bottom surface of the elevators. The last one on each surface closest to the trailing edge does not provide enough clearance to set with a squeezer or to get any bucking bar in there. I got one of the four rivets (one on each surface of both elevators) set by the offset back-rivet method. This method was described way back in the elevator days, I believe. As said, I got one set, but it was a real effort. And after an hour or so trying to get the second one set properly, I realized that I just bought a small supply of cherry max rivets for just such an occasion as this. Cherry Max rivets are pop rivets (AKA, blind rivets) but are structural. That means they can be used where you would normally use a solid rivet. The only draw-back to the Cherry Max rivets is that they’re expensive at about 80 cents each. You wouldn’t want to use them for every one of the 26,000 rivets or so needed to build the RV-10. But using three of them in these very tight spots is just perfect.
Finally got the trim tabs done. Wow, they were a hassle. There was a particular rivet on both trim tabs that gave me particular difficulty. I had to drill it out on one side 3 times, and twice on the other side. On both sides, I discovered cracks in the dimple of the skin and had to remove the rivet, drill out for a #4 rivet, dimple for a #4 (the hole was a little oblong after drilling out a couple times (on both sides) and I wasn’t comfortable using an oops rivet), and squeeze them in. The pictures show one of the holes after polishing out the cracks. I suspected the crack initially and used a handy magnifying glass that Zach keeps in the garage for easy access when he’s in the mood to start camp fires in the fire-pit (which he actually does successfully). The troublesome rivets were in the trim-tab control horns which are shown.
Then I did the proseal job. Man does that stuff every bit live up to its reputation. What a mess! But now the foam ribs are in place in the trim tabs and the elevators. I’ll give them a day or two so the proseal can cure and then hopefully finish off these elevators! I’m guessing there’s another 10 hours of work to finish them off.
Primed all the parts for the trim tabs. Because the pictures of the primed parts are hardly interesting, I took some extra pictures of the yard, which always looks so nice this time of day under a blue sky.
A ton of little things done tonight. The closeout tabs on the sides of the trim tabs were bent into place – though these aren’t perfect, I’m sorry to say. It involved clamping wooden wedges into exactly the right place and bending aluminum and then hitting the aluminum with the rivet gun set at low pressure in order to crease the aluminum on the right line. But I had a problem with the wedges moving when hitting it with the rivet gun and creasing the aluminum slightly out of place. It’ll hardly be noticed and isn’t a safety issue, so it stays as is.
Other things done were trimming the trim-tab control horns to the right shape and deburring the edges, final drilling holes, deburring holes, countersinking holes, and probably one or two other things I can’t remember. With all this stuff done, I forgot to take any pictures.
Oh, and I had some help from Daniel today. He helped to hit the edges of the trim tabs with the rivet gun (as mentioned above) while I tried to hold the wedges in place. This method helped, but still didn’t give us perfect bends.
These trim tabs are annoying. Not because they’re hard. No. Because every step requires you to build things out of wood. So, to avoid buying a band saw, I arranged to borrow the six clamp blocks needed for the trim tabs from someone whose further along in their construction of an RV-10. Then I had to buy a long 2×8 and hinges to build a break for bending aluminum. Of course, I made the break and sanded it smooth so it doesn’t scratch the trim-tab skins. Then I needed a couple of wooden wedges having the same geometry as the clamp blocks. These wedges are used for bending the ends of the trim tab skins. … Anyway, I think I’ve now got all the extra wooden things made and the trim tabs are under-way.
I didn’t put in as much time on the airplane as I had hoped today. Scott and I went to the local EAA (Experimental Aircraft Association) meeting this morning. We both wanted to hear the speaker who was a former Top Gun instructor and had some great stories. And I wanted to see a demo that was being done on how to use proseal. Good timing on that demo since I’ll be using that stuff for the first time in a few days.
There are several builders at the Manassas chapter of the EAA (this is the chapter we belong to) who are building or already flying RV-10’s. As a bonus today, there’s a member getting ready to fly his RV-10 for the first time within the next couple of weeks, and he invited Scott and me to come by his hanger and check out his airplane. It was exciting to see and made Scott and me both look forward to when our airplane is at the same stage.
Realizing that I’ll have to do the proseal dance again with the foam ribs in the trim tabs, I decided to hold off on that task on the elevators until I can do this job on both the trim tabs and elevators at the same time. Therefore, I began the trim tabs, the first task of which is to cut wood to be clamping brackets. Such precise measurements are given for the dimensions down to the 1/32 of an inch! The marking lines I draw on the wood are thicker than that! Anyway, I almost finished the first of six blocks and decided to stop because it’s late and I’m obviously tired.