Saturday, March 30, 2013

Wing Walk Doubler – Small Issue

Having spent most of the day running errands and dong chores on Friday, didn’t get into the shop until very late in the afternoon to finish up removing the rest of the plastic film from rivet lines of the W-1202B upper center skin and securing it onto the left wing skeleton.
                                            Removing blue protective film along rivet lines on the W-1202B-L
                                            upper center wing skin after melting the film with a soldering iron.

Fellow RV-12 builders will notice I’m not riveting the W-1201 wing skins just yet as called for in the plans. The plans instruct the builder to rivet the W-1201 skin except for the wing walk doubler area, then rivet the outboard W-1203 outboard skins, followed by riveting the W-1202 center skins. I suspect Van’s has the builder assemble in this fashion because of the large number of Clecoes required to do the entire wing at once. The number of Clecos they suggest necessary to build the RV-12 is NOT enough to Clecos to properly do the entire wing at one time (but keeps builder tool costs to a minimum). Early on in the project, the DOG Aviation procurement department procured many extra Clecos knowing they come in handy (and have already during construction of the tail cone).

In an effort to ensure the best possible uniform fit, all the skins are being secured in place onto the left wing skeleton before riveting. There are a few potential problem areas a builder should be cognizant of … in particular, those locations where a single flange (or tab) on the ends of the ribs are under the main spar and rear spar. Because I dimpled the rear spar along with all the W-1210 rib's single aft flanges, the dimple secured the single flanges so there were no problems here for me … but builders not dimpling should exercise care in both these areas.
                               Lifting the aft edge of the W-1202B-L skin and using a flashlight and mirror to verifying
                               the flanges under the main spar did not get pushed down from the rivet being inserted.

Builder tip:
The first thing I’ve been doing is verifying the tabs under main and aft spars are perfectly centered. Some tabs tend to want to move a tiny bit after they are positioned so once the skins are placed on the wing skeleton, the first thing I do prior to clecoing is use a center punch that is the same size as the rivet hole to center the tab then place a rivet into the holes that have single flanges BY HAND. This helps ensure there is not enough pressure on the rivet to bend the flange out of the way as the rivet is seated into the rivet hole. Placing a rivet into a rivet gun and shoving it into a hole at these locations is just asking for a flange to be bent out of the way and ultimately not riveted.

The last item that needed addressed was the wing walk doubler plate. Van’s has the builder place a couple of dimples in it and then set it in place to test the fit of the leading edge. (I of course, had already dimpled so those dimples were already there plus many more). The plans then say if the test fitting results in a gap, break the edge of the doubler to improve the fit. Can’t do it using a breaking tool because the rollers get hung up on the dimples! The breaking tool just won’t work AFTER the skin is dimpled! I worked and worked on the edge and spend a lot of time on it only making a small improvement … it would have been SO much easier to have broken the skin’s edge first prior to dimpling.
                          Using a metal plate to press the wing walk doubler tight to the edge of the workbench
                          while working the edge with a piece of PVC to place a small break on the edge.

Builder tip:
Do yourself a favor and break the forward edge on this skin before dimpling or even trial fitting … you will be glad you did.

The last task for the evening was to prepare the W-1201 skins for primer in the area where the wing walk doubler plate will be covering the top of those skins.
         Zinc chromate primer sprayed onto the portion of the wing where the wing walk doubler plate will be placed.