And the winner is...

It's AZKO all the way! Granted the prep time is longer and the chemicals are noxious, but man I'm getting a much better finish with AZKO than I am with the self etching primer. Here are two siffeners from the practice project. The dark gray one in front was primed using the self etching primer and the gold one in back was primed with AZKO. Both pieces were alumiprepped and alodized.

Please excuse the blurry photo, but here you can see the self etchingprimer scratches off easily with a fingernail:

This is one of the reinforcement places. These were the last parts I primed. This is pretty close to what the finish should look like. Very light coat, just enough to make the part that distinctive gold color. I was holding the part by the corners which is why they are not covered well. I still have to put together a chickenwire spray and drying rack.

I'm sure there are as many opinions on the topic as there are builders - and then some. For me, it's the three step Alumiprep, Alodine, AZKO. Sure it may slow down the process a bit, but I can't argue with the finished result. I'll still keep some self etching primer around for the little one-off jobs.

I'm going to try and alter the build process a bit in an attempt to reduce the number of batches I need to prime. I would love to complete the tail kit with only one or two days of priming. That means getting all the subassemblies fitted, dimpled, and deburred before I drive any rivets so that I can prime all of the parts in bigger batches. I'm not positive on the feasibility of this approach, but I'm going to give it a try.

Primer Wars

Last night my dad brought over a compressor which is great news because there's not much I can do without one. Before I begin my empennage kit I need to decide which priming technique I'm going to use. I wanted to compare the 3-step process of Alumiprep, Alodine, and AZKO with an off the shelf self etching primer. So after work I stopped by the closest Auto Zone and picked up a couple of cans of Rustoleum self etching primer.

When I got home I resumed work on the practice project and completed everything I could do before I needed to start riveting. I brought the spar, ribs, siffeners, and trailing edge up to the garage to prime. I Aumiprepped and Alodined all of the parts. I've heard that some people skip that step with self etching primer, but I wanted to give the Rustoleum the best shot possible. I used the Rustoleum on two of the stiffeners, and I used AZKO on everything else. It took me a little while to get used to the sprayer (dialing in the right pressure and liquid flow) but by the last few parts I was getting a nice thin coat. I can already see a difference between the two products, but I will reserve my verdict until I've let them cure overnight.

Tomorrow I have Josh all day so I probably won't have any time for the project. My next task will be to complete the practice project so I'm warmed up for riveting, then it's on to the real thing.

Another Practice Project

Way back when I first became enthusiastic about RV assembly, I ordered a practice kit from Van's. I had none of the tools I needed to complete the project, but I wanted to get a feel for what the materials are like. Since then I've taken the SportAir RV Assembly workshop (which I highly recommend to anyone thinking about building an RV). At the workshop we were each provided with a kit to build during that weekend (which is the same exact kit I ordered from Van's). So long story short, I have one practice kit that I completed at the SportAir workshop, and one that's still in pieces. I thought it would be a good idea to get myself warmed up for the real thing while trying out some of the new procedures I've learned using the practice kit. You can see that this time I used a solidering iron and a straightedge to score the plastic coating of the skins. This is a common technique that allows some of the protective plastic to remain on the skins while still exposing the rivet holes. Van's recommends removing all of the plastic as soon as possible because the glue strengthens over time and can be a real pain in the arse to remove. I'd rather deal with super sticky glue if it means fewer scratches. This time around I am also going to really smooth out all of the rough edges (I took some liberties with the SportAir project) and I will prime the spar, ribs, and stiffeners.

Here you can see the project in progress along with the completed project in the background:

My dad is coming over with a compressor just as soon as he's finished watching the Celtics kick the snot out of the Bulls. Hopefully tomorrow I can try my hand at spraying some AZKO primer.

Alumiprep and Alodine

My primer shipment arrived from Aircraft Spruce this afternoon, so I thought I'd play with the Alumiprep and Alodine process during my lunch break. I finished deburring one of the stiffeners from the practice kit and headed up to the garage. Looking back, I should have dimpled it too. Oh well... it's just a practice part. I poured a 5:1 ratio of the Alumiprep into a Dixie cup and applied with a foam brush, then rinsed with water. Once that was almost dry, I poured a little Alodine into another Dixie cup and applied with another foam brush. The aluminum takes on a gold hue. I rinsed the part once more and set it out to dry. It seems simple enough. We'll see how I do with mixing and spraying the AZKO. I just need to pick up a compressor from my dad's house and I'll be ready to rock.