Had some family obligations this weekend, so not a lot of time spent on the plane, but I am inching ever closer to spraying more of that expensive epoxy primer on my remaining LE parts. Here is pic that I love showing to folks so they can see the difference between brand new "tools" and what it looks like after you use them during the build. On the left is a brand new, as yet unused medium grade (maroon) scotch brite pad. On the right is the one that I started using when I prepped the first two LE ribs and a couple of other parts. Since then I have prepped the 4 remaining LE ribs, and the interior LE skin.
When prepping my main wing ribs for primer a long time ago, I decided to follow a practice that Steve Riffe used to clean his parts prior to priming them. I took two orange HD buckets, filled both with warm water, and put Dawn dish soap (original formula) in one of them. I have found that the subsequent cleaning with acetone goes much faster if the most of the grime and residue has first been removed by washing the parts with Dawn first. It does not take long for the soapy water to turn pitch black, and I am always amazed at how filthy the parts actually are. Anyway, I set up a wash/rinse routine for the 4 remaining ribs, using a scrubbing sponge with the green scuff pad attached to one side.
I have not yet done this for the main wing skins, and I had not used this method for any of the other larger skins yet. But since I needed to prime a larger-than-normal part of the interior LE skin due to my subskin that will be in contact with the interior of the first bay of the LE, I decided that I would also try the same washing method I used for the ribs. Obviously due to the size of the LE skin I could not dunk it into the buckets like I did for the ribs, but I did use the sponge to wash the interior as best I could, and then wiped it dry with a micro fiber cloth. It seems to have worked well.
Prior to this I realized that I had not yet deburred any of the edges of the access panel holes or the outer edges of the LE skin itself. So I took my edge deburring tool and took care of that. this also raised a question that I will need to get answered from Vans or from someone on VAF. I am not certain if I am supposed to kerf the edges of the skin where they will attach to the main wing spar flanges. I think that I still need to do this, but I need to make certain.
I only question this because these skins are supposed to butt up very closely to the main wing skins and the fuel tank skins. I don't know if kerfing the LE skin will introduce a larger than desired gap between the main skins ant the LE, or if this is still necessary regardless, so that the edges of the skin will lay flat against the wing spar flanges when riveted in place. If I find out that I need to do this, I will need to find my edge kerfing tool from Cleaveland Tools, that I haven't used since I put all the tail feathers together.
Next is a pic of the 4 ribs all scuffed, cleaned, and final cleaned with acetone and a microfiber cloth. when you do multiple parts like this, especially those that need to be assembled in a very specific order, you have to devise a method to keep each part organized, since all prior identifying markings will be removed during the cleaning process. In this case, I kept the ribs organized by keeping them stacked in a very specific order each time I scuffed or cleaned them. I lined them up on the table after cleaning them so that they were in the same position that they will be installed in the LE from left to right. The end rib flanges face a different direction than the rest, so that one is easy to spot. But the others are exactly the same rib, with the same rivet holes and flanges all facing the same direction. Keeping them in order is very important, since even small variations in the match drilling process can make a difference in the final fit of the parts when they are riveted together. After they are primed I will put some tape on them and mark the rib position on the tape.
And finally a pic of the wing skin all washed and ready for primer. After the suds bath all scuffed metal was final-cleaned with acetone and a microfiber cloth (my carcinogen of choice for cleaning metal). I used chemical-resistant rubber gloves to keep it off my hands. These are the long green ones at the bottom of the pic. Also shown are a large number of microfiber towels that need to go in the washing machine so I can try to reuse them. Suggestion: do NOT put these in with any other clothes. Best to keep the airplane building/chemically-laiden materials away from other things, just in case.
Since I will most likely need to use a bit more primer to cover these parts than I did for the last batch, I will plan to use my HF HVLP spray gun, since it has a 20 ounce cup and larger spray area, compared to my touch up sprayer than only has a 7 ounce cup.I think that one full cup-load of primer from the HVLP gun will cover the interior skins and the 4 remaining ribs.
I will probably scuff and prime the entire subskin as well, since I have not yet determined the final form of this part, and I can't really do that until I have this access panel mess taken care of once and for all. One nice thing about living in Denver is that I don't have to worry about surface corrosion very much. So I can leave the scuffed parts till tomorrow, when I have more time to set up the sprayer and everything else that has to be setup for priming.
Till then,
KPR...
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