Just like a pilot would, I developed checklists for the various aspects of the building.
PREP & PRIME CHECKLIST
- Confirm parts
- Plastic off
- If it's a rib, check that all the flanges line up.
- Mark with part # (I actually don't do this much anymore since I can usually identify the parts necessary).
- Deburr holes (usually not needed because they're punched, but you should check anyway in case the punch was old and left some burrs) and edges (Scotchbrite by hand or wheel)
- Double check for all smooth edges and holes
- Spray with cleaner and remark # (see note above).
- Once clean don't touch the aluminum with bare hands so as to avoid getting any oils on them.
- Spray with Cortec Primer (I decided to use Cortec's non-toxic primer 373 because it's super easy to use and Zenith recommends it for their planes which use the same aluminum as the Slings. See below for more explanation.).
ASSEMBLY CHECKLIST
- INSTRUCTIONS
- Check Other Build Logs
- Prep/Prime
- Draw centerline on outer ribs so that any twist can be detected later when assembled (easier now than after assembly!).
- Cleco structure
- Check for outer rib alignment with digital level if applicable
- Check for evenness along rib flanges with long ruler
- Check for correct assembly, parts and orientation
- Cleco on skins
- Check for bulges or dips on the skins where they connect to the ribs.
- Check for fit and trailing edge twist
- Un-Cleco skins (fix ribs for any bulges/dips found on skins)
- Double check instructions for correct assembly, parts and orientation
- RIVET STRUCTURE!
- Double check for outer rib alignment
- Re-cleco skins
- Check again for any bulges/dips on skins
- Check for trailing edge twist
- RIVET SKINS!
PRIMER THOUGHTS
I decided to go with Cortec VpCI-373 Primer for a few reasons: It's non-toxic (I'm pretty sensitive to toxic fumes), according to my research it's just as good as any other priming method, it's very light weight and it's what Zenith recommends for their planes, which are constructed from the same aluminum as the Sling's (Zenith recommends only priming the surfaces that contact). The 6061-T6 aluminum is much more corrosion resistant than the aluminum used on Van's planes (2024), so I greatly discounted the information on Van's related websites, which tended toward over-the-top (and insanely time-consuming) priming.
Sonex are also built of 6061-T6 aluminum and they don't even recommend any priming and don't do it for their own planes. Here's an excellent Sonex builder's blog where he discusses priming. I've even read on a kitplane discussion forum about someone that builds ocean docks using 6061-T6 aluminum and they don't prime them - and have no corrosion problems... If that doesn't convince you not to bother overdoing it, I don't know what would.
Another benefit of my approach (all internal surfaces), and I think this was the clincher for me, it's a very simple process to apply. Since it's self-etching, all you need to do is clean the aluminum with a solvent (I use this) and spray on the primer. No Scotchbriting required! I confirmed this method with Cortec technical support. Love simple and fast!!!
RANDOM TIPS
- You'll find many of the holes seem slightly too small for the rivets. I have a cordless drill at the ready with various sizes of chucking reamers. These are the sizes of reamer bits I use for the various rivet sizes:
- 3.2mm rivet ==> #30 reamer
- 4.0mm rivet ==> #20 reamer
- 4.8mm rivet ==> #11 reamer
- You can get all the chucking reamer bits here.
- Related to that I recommend making a wooden pusher stick to help push rivets into the holes. I just have a 1" x 1" x 12" piece of wood that I've drilled a hole in one end that's the width of the rivet mandrel. If it requires even slightly too much pressure to push the rivet in, then don't push it, ream it!
- The Sling's are pre-punched with the correct size holes, as such they should not need drilling (unless the instructions say otherwise!), nor should they need deburring (generally). I've been checking the holes and rarely have they seemed to need deburring. If a drill has touched a hole, it needs deburring.
- Broke my first rivet gun, but I'm glad I did, because the new one I got is WAY better! Quieter, more powerful and can more easily pull many rivets in a row without having to empty the container. This is it: Astro Pneumatic PR14 Air Riveter
