This took a little more time for the left wing than John Slade (who was up for the week helping me build the wings) and I expected. Mainly this was because of a few small alignment issues setting up the cores, but we wanted to get things perfect. Also, I caused us to take longer in the squeegee step by putting on too much epoxy by getting over-eager with my "dump and run" layup method. Still, the left wing joint is beautiful. We'll see if I can do the right wing just as well. When you cut the W18 cover plates that go over the wing attach bolt access holes, note that cutting per plans is unlikely to produce a good fit. A better way is to cut the plates slightly oversized, make the bend, then get the plates into position and scribe them to cut off the excess for a perfect fit. You only use an extra half inch of aluminum this way, and they look much better. Also, a comment on Alodine. I've had mixed success with this, so I thought I'd pass along a few tips that generally produce better results. The most important thing to know is that the qality of the Alodine step is almost entirely controlled by the cleanliness of the part. The Alumiprep can produce a part that looks clean, but once you alodine you see fingerprints and such left over. By then, it's too late to do anything, and that spot won't take the Alodine very well.
To make sure the parts are perfectly clean, first use some MEK or other cleaner to remove any micro or epoxy contamination that might be on the piece from setting it on a workbench, against a curing work piece while measuring, etc. The key to understanding what's happening is knowing what these chemicals actually do. Alumiprep will NOT remove this stuff - it's an acid, not a solvent. It's designed to react with corrosion and remove it, and etch off any other surface problems. But it only works against aluminum-related problems. So, after removing any epoxy issues, wash with clean water and a strong detergent to remove skin oils. Alumiprep will not remove all oils, just a few of them.
Next, know that the effectiveness of the reaction will be controlled by heat. You're suposed to dilute the Alumiprep, which is fine, but do it with warm water, not cold. You'll get a better reaction. Use a disposable brush to remove as much surface crap as possible. Then comes the key - use an abrasive Scotch Brite pad. (Use one without soap in it - Harbor Freight sells cheap but usable pads.) Get down into any scratches, which you ought to have - you did rough up the faces before glassing, right?
Finally, when Alodining, use a brush to make sure you have good coverage of the chemical. Some of the initial reaction may produce free converted material in a thin barrier liquid layer of used-up reagent on top of the piece. A brush will move this aside and allow the reaction to finish on the piece itself. I use small disposable acid brushes for this - you can get 36-packs cheaply. Don't forget to radius the corners of the wing attach hard points to match the foam, before installing them! And don't forget LWA2 and LWA3, which are described in Chapter 14. I missed mine for the left wing, and will fix this when it comes time to glass the bottom.