Rudder Fun

Well I have been working on the rudder. By far the most difficult part to date. This piece requires taking the time to plan and figure things out.

I didn't want to buck all the rivets because my bucked rivets are not as good as those when I use the squeezer. So I had to buy a 4" yoke for the squeezer to reach the rivets.

Also the screws that hold the lead counter weight are #10 with a 100 degree countersink. So had to get a #10 dimple die for this screw. Lastly, I had to relieve the lead weight to clear the forward most rivets of the rib.

I needed what is called a longeron yoke to get the rivets on the control bracket, but didn't have one. I ended up putting a nut under the rivet set on the squeezer and this worked.

When I riveted on the doublers and nut plates to the spar, the 3/8" heim joints would not screw in. So I drilled out the rivets, inserted the heim joints in the nut plates and then riveted the doublers and nut plates to the spar. This was the only way to get everything lined up while riveting and I had to use the  4" yoke and longeron trick.

To make the trailing edge angle tooling that will hold it straight while assembling, I match drill all the trailing edge parts, then double sided taped the AEX strip to the aluminum angle and match drilled the angle to the AEX strip using the drill press.

When countersinking the trailing edge AEX piece I made a simple wood jig and used a allen wrench that was just big enough to hold the trailing edge flat.

No where in the instruction manual did it say when to rivet on the rudder bracket. This should be done just before the first skin is riveted on. I riveted the top of the skin near the balanced weight, and then had to carefully lift it up to get the rivets squeezed holding the bottom bracket; it would have been better to do the bracket before the skin.

As per the instructions, I  bonded the trailing edge together with pro-seal using the aluminum angle tooling on the outside to keep everything straight, waited three days, and then riveted. The trailing edge came out straight, but I seem to have gotten some separation of the trailing edge skins from the AEX wedge, and some pillowing between the rivets. This really bothered me until I read other blogs, and I am not the first. There is pro-seal on all the surfaces, so it is not an adhesion problem. Maybe it was too thick. Next time I will use a scrap pick of angle and squeeze the trailing edge together using seaming pliers immediately after assembly. This should squeeze out the extra pro-seal leaving a very thin layer to bond, hopefully eliminating the pillowing. For the separation, I tried re-riveting the end but it didn't change anything. It is acceptable, just not preferred. Maybe in a year or two, if I haven't come up with anything better, I was thinking of adding some JB weld to the seam to fill in the gap, making for a rigid, impervious, blunt trailing edge; nothing I can do about the pillowing an it is very slight. 

"Just keep swimming.." Dori

I was able to add some wall art to my shop, namely the completed horizontal and vertical stabilizer!
The vertical stab came out good but not great. I vowed to improve my riveting technique half way through..I had a problem with the rivet gun slipping while using the mushroom set for the flush rivets. This would cause a minor smiley or indentation in the skin. I decided to try some double sided tape to see if it would help. I was worried about it leaving the rivets set high. Turns out it worked great. It was sticky enough to keep the mushroom set from slipping, but not sticky enough to prevent removal. You can see in the picture the first rivet I did with this strip of tape left a circular indentation in the tape, but it came away intact from the rivet/surface. I think this is the new way for me when riveting with the gun solo.

Now onto the rudder and elevator.  I was able to prep, mix the primer, shoot, and clean up the mess in about 4 hours. Not too bad and I think worth the effort.. I love the 2 part primer; so much better then the rattle can stuff. If I add drying time into this analysis, priming with 2 part is less time than rattle can, and cheaper too. My prep was simple, wipe with acetone, then shoot, being careful not to touch the surface with my hands. And I did this before dimpling. I am only priming the inside part of the skins, but both sides of ribs, spars, and everything else.

Priming lessons

So....
Started using the proper primer instead of the rattle can stuff from the local auto parts store. This is the same Sherwin Williams P60G2 primer that Vans Aircraft uses, but in the US it is tinted green.

There is a fellow builder, Sam, using  Dupont Veriprime615s. He seems to have had great success brushing the primer on. This sounded great and easy. So I tried that technique with the SW P60G2 on the rear spar of the horizontal stabilizer. Here are my results:

They have a molted appearance, but all the metal is covered, and it isn't too thick... But man is it fugly (really ugly).

So I bit the bullet and decided to brush up on my painting skills using a spray gun (pun intended). I was 18 the last time I painted aircraft parts with epoxy paint; all I remember is plan and prep, plan and prep.  I was going to build a spray booth, or downdraft table,  but this was a lot of infrastructure, and stressing over this became no fun. So I just decided to keep it simple and spray the stuff with cardboard on an old table. The stuff dries really fast once sprayed. And the over spray is easy to control since it is going on very thin; not much worse than rattle cans.

It worked out well. The primer was hard to get stirred up, until I took it to a paint store and had them shake it. Mixing the catalyst was easy, felt just like old times. My prep is simple: Scotchbrite the dimples and very smooth areas of the skins and spars, wipe down with acetone using gloves, and then spray. I didn't go for this 3 stage process others are using with etch, alodine, and whatever. (Some people don't even prime, and the plane comes out fine; do you believe that? ;-)

Below is my vertical stuff all primed. Maybe I will wait a day before assembling, to give it time to harden.

This has been a yuge learning curve but now time to move on. Not sure if I will prime the wings or not. But probably wont prime the fuse because I will be crawling in there a lot and I want the reflection of the metal to help with lighting during inspection.

Busy Few Weeks

These last few weeks have seen great progress.

The horizontal stabilizer is complete less the rear spar; waiting for the rear spar to be primed before installation. The vertical stabilizer is ready to be primed, then riveted.

 I had a tech counselor visit and reviewed my work to date; all is well. We went for a quick flight in his RV9; it flies really well and seems to yearn to be in the sky.

The tech counselor showed me his tungsten bucking bar, and I now own one too. This is a must have tool in my opinion, especially for the front rivets in the horizontal stab. I would recommend buying the smaller bar, something like the 1/2" x 1/2" x 4" for less than $100. I got a slightly the larger one and it seems a little over kill for the tail feathers, but will probably be good for the beefier fuselage and wing rivets.

In addition to finishing the horizontal stab and making good progress on the vertical stab, I picked up the wing kit from the factory. I also picked up Proseal for the rudder and the locking gas caps. I would like to have the wings started before the New Year.

More steps

This weekend, I was able to complete the right side of the horizontal stabilizer. And the local high school celebrated with fireworks.

This was a major riveting sessions. I wish I would have bought a tungsten bucking bar for the nose ribs; it is really hard getting in there; those rivets aren't pretty but acceptable because I had to make do with the bars I had. I tried using a big chisel and other thin steel objects, but they just didn't have the mass to buck. It can be done with the standard bucking bars, but just takes time and yoga.

This kit is very precisely made; if the holes are off by a few thousandths of an inch, then something is wrong. The skin needed some clearance filing around the front spar brackets. Otherwise the skin would have been right up against the brackets. This could produce a squeak in flight, or worse, be a start for skin cracking. A few swipes of a jeweler file relieved the skin a few hundredths of an inch. 

First Rivets

I managed to rivet my first part, the horizontal stabilizer's front spar. I think it came out pretty well, but we will see what the local EAA

tech counselor thinks about it.

Primer woes

As I complete the horizontal stab dimpling and prepping for assembly, I was hit with the imfamous primer plaque.

My plan was to use rattle can primer on the horizontal stabilizer because there are holes in the rear spar and water can get in when parked. Since primer is not required, I figure simple rattle can would be adequate without the hassle of the two part stuff. Boy was I wrong. The rattle can went on fine and hardened up Ok after a week, but any hint of a chemical nearby and it curled up and was useless.

In addition, when priming the spars, a few drops of sweat got under the primer and got trapped there. Of course this will stay forever since the primer seals out, and seals in, moisture. Come to find out this leads to corrision problems. So I had to go over the spars and remove the primer where moisture got trapped. Then during touch up, the old primer reacted and a mess was made. I was able to get the front spars acceptable, but the rear spars required stripping the primer off completely.

For the priming, I think the only way to go is two part primer. The factory recommended Sherwin Williams s60g2 was out of stock; but I will wait and reprime the rear spars with this two part primer. It is more work, but the rear spar seems to be the most exposed to the elements.
Lesson learned: learn from others, do what others have had success with. In this case two part primer