After a busy morning dodging thunderstorms both in Chicago and Omaha I got in the hangar for some work. I knew I would only have a few hours between office work out at the airport and game six of the Stanley Cup (let’s go Hawks). I had the left elevator all assembled and matched drilled a few days ago. So next was to disassemble it all and treat the edges, deburr all the holes, scuff the surfaces and dimple/countersink where required. All those tasks were completed except for the countersinking of the trim tab spar.
That spar has dimples on the bottom flange and countersinking on the top flange. That’s due to the trim tab hinge being attached to the bottom side of the top flange of the spar. This is a sandwich of sorts, the skin on top, the spar flange in the middle and the hinge on the bottom. If you dimple the flange they would not allow the hinge to sit flat. Unfortunately I didn’t realize this until I read ahead. But at that point I was mr. speedy working with my pneumatic squeezer and had already dimpled both the top and bottom flanges of the trim tab spar. So I thought I would be ordering a new part from Van’s. So I grabbed the MacBook and loaded up www.vansairforce.net and did a search for the trim tab spar. What do you know I’m not the only novice builder that has made that mistake! After a little bit of reading I found that it would be perfectly acceptable to use my pneumatic squeezer and my no hole yoke/flush set and flatten the dimples. You can do this once without to much distortion of the metal. So I figured this would be a great time to call it a day, after making a mistake(and a severe thunderstorm warning rolling through my area). So I cleaned up the hangar and pulled the truck inside. While cleaning up I decided to drill a couple of holes in the workbench to hold the trim tab spar. The spar is fairly thin metal and when you countersink thin metal the hole gets enlarged a little. That larger hole will now let the guide, which is the size of the rivet, wander causing chattering and a bad countersunk hole. To prevent this I’m going to use wood as a backer on the flange of the spar. I will drill holes through the holes of the flange into the wood matching all the holes on the spar. This will allow a hole for the countersink guide to stay centered and make a nice countersink.
So that’s all for today, I fly a day trip to Minnesota tomorrow and will get some time in tomorrow night.
Got out in the hangar this morning to do a little work. The task for today was to rivet the rest of the right elevator skin. Pretty easy task with the pneumatic squeezer. Just three different rivet sizes, AN4263-3.5, 4 and 4.5. Those are 3/32 diameter flush heads and three different lengths based on how many pieces if material you are going through. So the right elevator is done minus the rolled leading edge which I will wait for the left side to be ready for that step as I have to set the jig up for that. Then the fiberglass tips which I will wait for the empannage to be finished so that I can work on all the fiberglass at the same time. Next up the left elevator.
Too nice of a day to not take the Harley out for a ride. I have two day trips on Monday and Tuesday so I will have a good week to play in the hangar!
The weekend started off right with nice weather although it is warming, finally. I wanted to give the primer on the right elevator substructure parts a little more time to cure since it is pretty humid here. So I started to work on a difficult project (and a tough decision) on the left elevator. As I have discussed in other posts the left elevator differs from the right in that it has a trim tab. For you non flying types, this tab can be adjusted inflight to reduce the loads on the control stick by helping deflect the elevator in the direction needed. So the left elevator has a cut out for this tab that will attach with a hinge. The side view of the tab ends and the one side of the elevator where the cut out is have to be dealt with. Van’s has you use wood wedges to make a form and bend the aluminum over closing up these ends. The usually leads to headaches if the bend doesn’t go smooth and ends up with a dented and mangled end. I have read several blogs and it made me nervous. The other option is to cut off the ends (the ears) and install a riblet to that area. That was my plan, I mentally prepared myself to this process. For now I will work on just the elevator as the trim tab will be done in the following days. I need to make a run to Home Depot to get some new cut off wheels for my Dremal tool. Once I got back from the Depot I needed to lay out the cut line. I found the line where the bend line would have been and marked it out.
After measuring top and bottom 43 times and remarking a few times I was finally satisfied with the location of my mark. So now was the time to make a cut with the Dremal tool. The plan was to cut within a 1/16″ of the line and use a file to bring the cut right to the line.
After the top was done I flipped the elevator over and cut the bottom ear.
So what to replace those ears with? Several builders have built their own riblet from scratch aluminum. I don’t have any experience with bending and forming tight spaces yet. So I decided to follow another path and use a piece of a E-703 rib. This is a rib that is used in the elevator so it has the right shape already in it. I ordered two extra ribs when I ordered my other parts, due to my earlier mistake on the counterbalance weight, from Van’s. I had one scrap E-703 so that made up the three I needed, one for the elevator and two for the trim tab. So I did some measuring and came up with the right length. I wanted the riblet to extend into the trim spar and tie them together. The problem with that plan was that the elevator skin was already pre drilled to the trim spar. Where the riblet would land in the trim spar had a drill hole right on top of the riblet web line and not on the middle of the flange where it needed to be. I could slide the riblet inward to accommodate this hole but I wanted the riblet to be flush with the edge of the skin for the strength factor. So I then decided that connecting the riblet to the trim spar wasn’t necessary as the the ears that folded over wouldn’t have either. So I took my measurements and cut the end of the E-703 rib on my band saw and finalized the shape with my Scotch-Brite wheel.
This rib was already matched drilled to the end in the elevator during my counterbalance mistake. So the holes in the end where there already and I would need to do some careful measuring. Normally you would have the holes in the skin and drill the riblet from those holes. This time I would work backwards. I’m happy to say that my measurements were spot on and all matched perfectly.
That was a lot of fun! and it was time for a lunch break to give my brain a rest, it doesn’t take much to wear mine out! :-). After a little food and rest I got back at it. Now up was to rivet the right elevator substructure. The plans call for you to rivet the two ends ribs, E-703 & E-704 together then to the spar. I have read several blogs the recommend you rivet the shorter rib, E-703 to the spar first then to E-704. This is due to the weird angle of those two rivets, so that’s what I did. Then I riveted the two ribs together pretty easily.
Next up was the doubler plates and their nut plates.
The other end of the spar gets the E-709 rib and is attached with AN426 flush rivets as the elevator horn attaches over this area.
The plans give you the option on the next step. There are four rivets, two top and two bottom that attach part of the E-713 strap to the skin that will be inaccessible to buck when the spar is in place. They give you the option to rivet those now with solid rivets or later with blind pop rivets. I decided to go solid and keep the look the same.
Now to place a dab of RTV silicone on the ends of the elevator stiffeners that meet each other at the trailing edge to prevent vibration cracks. Then you slide the counterbalance weight in place followed by the spar substructure. I the clekoed the pieces all together.
It was now time to call it a day to get ready to watch the Chicago Blackhawks game! All in all a great day in the hangar
I haven’t had the chance to get in the hangar for few days but today was a perfect day to get some work in. First up was to finish up all the edges of the right elevator substructure. Then deburring all the drilled holes followed by dimpling. In preparation for priming I scotch-brited all the surfaces, fun work!
After I cleaned all of the parts for priming I set them aside to dry. I figured it was a great time to trim the counterbalance weight. There are two weights, one for each elevator. On the right side there is less weight in the elevator compared to the left side. That’s due to the left side having the trim servo and trim tab. The weight needed to counterbalance the right elevator needs to be less than the left. So Van’s has you trim the right side weight as seen on the plans.
I laid out the section that needed to be removed. I placed it in a clamp and used a hacksaw to cut trough the thick lead. Then I used a rounded file to create the radius and a flat file to finalize the size.
The lead weight didn’t take too long to form so I decided to step ahead and start working on the left elevator. Just like the right elevator process you start with matching up pieces and match drilling them. The skin, spar, ribs, trim spar and and elevator horn all get drilled.
That’s where I stopped for the evening to break for dinner and a movie. I’ll be back at it tomorrow morning and will get a good weekends worth of work done.
Been busy this week and on the road with my flight schedule. It was a good time since I have to wait for the replacement parts from Van’s. Yesterday afternoon, after landing in Omaha from New Oreleans, I jumped on the phone and called Van’s and ordered my RV-8 wings!! I’m pretty excited at this big step. It takes right at 8 weeks for them to cut and shape all the pieces. Now I will have a pile of aluminum for me to play with this fall and winter!
That spar has dimples on the bottom flange and countersinking on the top flange. That’s due to the trim tab hinge being attached to the bottom side of the top flange of the spar. This is a sandwich of sorts, the skin on top, the spar flange in the middle and the hinge on the bottom. If you dimple the flange they would not allow the hinge to sit flat. Unfortunately I didn’t realize this until I read ahead. But at that point I was mr. speedy working with my pneumatic squeezer and had already dimpled both the top and bottom flanges of the trim tab spar. So I thought I would be ordering a new part from Van’s. So I grabbed the MacBook and loaded up www.vansairforce.net and did a search for the trim tab spar. What do you know I’m not the only novice builder that has made that mistake! After a little bit of reading I found that it would be perfectly acceptable to use my pneumatic squeezer and my no hole yoke/flush set and flatten the dimples. You can do this once without to much distortion of the metal. So I figured this would be a great time to call it a day, after making a mistake(and a severe thunderstorm warning rolling through my area). So I cleaned up the hangar and pulled the truck inside. While cleaning up I decided to drill a couple of holes in the workbench to hold the trim tab spar. The spar is fairly thin metal and when you countersink thin metal the hole gets enlarged a little. That larger hole will now let the guide, which is the size of the rivet, wander causing chattering and a bad countersunk hole. To prevent this I’m going to use wood as a backer on the flange of the spar. I will drill holes through the holes of the flange into the wood matching all the holes on the spar. This will allow a hole for the countersink guide to stay centered and make a nice countersink.
So that’s all for today, I fly a day trip to Minnesota tomorrow and will get some time in tomorrow night.
