Scott & Tanya Card RV9A build log (N4822C)

Time for an update:
I finished up the second flap and got the flap and aileron hinge brackets riveted to the rear spar. Both flaps are hinged and all is well. The second flap went together pretty much like the first. I’m not going into all the gory details. My tips for others building -9 flaps are: Make very sure you don’t oversize the spar rivet holes when machine countersinking. I think Vans says somewhere that it is ok if you do, it is not. This requires that you machine countersink the main flap skin and spar together as a single unit for the dimple in the nose skin to fit. Check hinge bracket alignment against the completed brackets on the wing after the flap skeleton is riveted together and a couple of skins are clecoed on (top and nose skins). This is the time to make small adjustments for a perfect fit.

All of the aileron and flap hinge brackets were riveted to the rear spar (and ribs) without much problem. I was able to squeeze a little more than half of the rivets. The rest I shot with the rivet gun. I think I have officially finally overcome my struggle with shooting large AN4 long rivets. The key is clearly high air pressure at the gun and duct tape on the tip of the rivet set. I am using about 64 lbs. of pressure to shoot the big rivets (a little higher when using the offset). Any less, and you have to hit the rivet too many times and the metal work hardens and will simply stop compressing because it is now too hard. You can clearly see this happen while you are shooting the rivet. With higher pressure, you hit it much harder fewer times, and the rivet is properly set by the time it is hardened and won’t go any further (keep hitting it after it has hardened, and it will start to crack or fracture).

The flap hinge brackets on the wings each get a small brass bushing press-fit into them at the hinge point. The hole should be the right size for the bushing. If you press the bushing into the hole and the hole is too small, guess what, the bushing inside diameter compresses and then the bolt won’t fit right. So, I measured the OD of the bushing and the ID of the bracket hole and opened up the bracket hole just a bit to within a few thousandths of the bushing size with a little bit of emory cloth. A very nice press fit of the bushing resulted. I used a block of wood and a vice grip clamp for the press. The block of wood was soft enough for the bushing to press into it the 1/64″ called out.

Oh, did I mention that my primary ear protection finally decided it was done. I went to put it on before riveting and ended up with two pieces. Time for new ear protection.

Moving on to fabricating the aileron push tubes. First I cut the short steel aileron pushrods to length. I did this by hand with a hacksaw and boelube with the tube in the vice. I decided to stay away from the band saw for this part. I drilled the rod ends in the drill press and after deburring, inserted the rivets. Wow those rivets are long. My squeezer wasn’t up to the task so I had to shoot them. Shooting those rivets actually worked out pretty good. They aren’t perfect (a little folded over), but good enough for me. Then I got out the aluminum tubes that attach the control stick in the cabin to the aileron bellcrank. I cut these to length once again with the hacksaw and deburred then drilled the ends in the drill press. Many thanks to Tanya for standing there supporting the end of the tube while I drilled.

Once the aluminum tubes were prepared, I mixed up some primer and primed the insides of the tubes by just pouring primer in and twisting the tube back and forth and pouring out the excess. The tube ends were then riveted on with six blind rivets on each end. Next up is to prepare and prime the outside of the push tubes.

Note that this covers many days of work.

 

  

  

  

  

  

  

  

  

  

  

  

  

  

  

 

I completed riveting the trailing edge of one of the flaps. It came out very straight. I’m amazed. I also riveted the outboard aileron hinge bracket assemblies onto both wings. There are two rivets on each of these that must be bucked.

David came over with some hardware that he just received that I had added to one of his Vans orders. Much appreciated. It is very nice to have three of us building in the same neighborhood. It makes it very easy to consolidate parts orders.

Yep, another fun filled weekend of flap and aileron construction. If you can’t tell, I’m just about ready to be done with these parts.

We started off by shooting a few remaining rivets on the flap skeletons. I’m happy to report that they all went well. It was then time to start stitching the flaps together. I used bags of lead shot to weight them down on the flat bench surface all along the way (as much as possible). This is supposed to help them come out straight with no twist. Even so, there is still plenty of opportunity to introduce a twist into these long flaps. The skin riveting process on the flaps is pretty easy except for the bottom skin to spar rivets which must be shot blind. This is no simple trick. I got one of the flaps closed up and the trailing edge bonded with proseal just like the ailerons. I still need to rivet the trailing edge after it has had a day or two to sit.

Tanya and I (yes, she has been shooting most of the skin rivets) got much of the second flap riveted together except for the bottom skin. For some simple storage space, I took some of the cardboard that came in the fuselage crates and put it on top of the wings to make a place to temporarily put parts. This has been working out very well.

I decided to take a little break from flaps and got out the ailerons. The trailing edges had been curing on them for a couple of days so they were ready for riveting. I got both of the aileron trailing edges riveted using the same method that I used on the empennage (squeeze the rivet with a modified flat set, then back rivet with a mushroom set). Both trailing edges came out very straight. I’m pleased. Then I was able to move on to installing the aileron hinge brackets. This is kind of fun although a bit slow because I’m taking much care to get them on straight.