With the flap skins fitting properly, it was time to start fabricating and fitting the flap braces. The aft part of the brace is precut and prepunched by Vans, but the forward angle is fabricated from 1″x2″x0.125″ 6061 angle stock. Nothing particularly difficult here, just exercise due dilligence in laying out rivet holes to maintain edge distance on the angle – repeat for the other flap and we’re done.
The aft brace also gets a slight bend just behind the area where it joins the angle. The bend allows it to set flush against the inside rib. Here are the two parts clamped together and ready for fitting to the left flap. The angle is predrilled. Sorry, no pictures of the right flap brace…

Those new flap skins arrived today. I couldn’t wait to yank those bad boys out of the box and see if they fit properly. And they did! Very cool.

The replacement unpunched flap ribs arrived from Van’s; the lower flange of each rib is not punched. I was anxious to try them and get going on the flaps. Long story short – the flap skins were mis-bent and no amount of tweaking with the ribs would fix the problem. I spoke to Joe Blank at Van’s and asked for new skins. To his great credit, he shipped them right away at no charge and with no complaint. Thanks Joe!

Work has been busy; getting the flap braces tweaked took several days with little time spent each day. After match-drilling, the braces are countersunk to accept dimples in the skins. This leaves the upper surface of the brace flush to mate with the flap hinge. Taking a cue from Brad Oliver, I drilled a piece of wood to each brace to guide the countersink pilot and then countersunk the holes. Easy!

Vans’ response on my flap skin problem wasn’t exactly what I was hoping for. They’re aware of this issue, but don’t ship replacement skins any more. They suggested using replacement inboard and outboard ribs with no prepunched holes; according to Joe Blank at Van’s, match-drilling those ribs to the skins will fix this problem. I agreed to try their solution, since the replacement ribs are free. We’ll see if they work.

Meanwhile, I did some cleanup work on the flap braces on both wings. One thing I had neglected to do in the past was match-drill them to the lower wing skins. Before I could do that, I had to tweak the braces a bit with a hand seamer to make them line up smoothly with the skins. The braces are left with a bit of a twist due to the way they’re riveted to the rear spar and doublers. With a little adjustment, the braces and skins line up nicely for match-drilling.

With all those shims in place, it was time to drill the flap hinge and lower skins to the skeleton. With the spars and shims drilled, match-drilling the lower skins was easy. Drilling the flap hinge took a little more work, since it’s one, long floppy piece of AN piano hinge. There’s also very little room for error when drilling it with the proper edge distance as specified by the plans.

The first step was marking a centerline on one leaf of the hinge. I fabbed up a homemade edge marker block similar to the one sold by Avery Tools and marked the leaves of both flap hinges. I then clamped the hinge in place on each flap spar, making sure to align the centerline and spar holes. One minor trick…I used small pieces of thin plywood between the clamps and hinge leaf to avoid squeezing and deforming any hinge eyes. A few minutes with the Sioux and a #41 drill bit, and the hinges were match-drilled to the spar. I then match-drilled the entire structure to #40.
Things were going great, I was on a roll…so I decided to finish up by match-drilling the upper flap skins to the lower skins, spars and flaps I had done over the last two days. I grabbed those flap skins, clecoed them in place…and then found a problem. Remember that picture from October 6?
If you noticed before that the trailing edge bend didn’t look right, you’re very observant. Other builders have had the same problem with flap skins delivered in late 2005 and received replacement skins at no charge. I called Vans and reported the problem, we’ll see what they propose.

Another area where shims are required is between the aft end of each interior flap rib and the lower skin’s J-channel. This is one I really can’t understand…why doesn’t Van’s just make the ribs long enough? Ok, enough grousing already.

One minor catch here…the aft-most hole in each rib’s lower flange isn’t drilled. That gets done by using the corresponding lower flap skin as a drill guide. Without a cleco to hold them together, the rib flange and skin must be clamped together tightly before the rib’s rear tab and shim are match-drilled to the J-channel, pulling the tab into the proper position. Clear as mud, right? Anyway, I used a small piece of plywood and a clamp to pull the flange in place, and another clamp to hold the shim in place as it and the tab are match-drilled to the J-channel. The shim gets trimmed to length after drilling.

For some reason known only to Vans, there are a few places in the flaps where shims are required to fill gaps between the skins and adjacent substructure. One place I can understand – a gap formed by the overlap of the upper skin on the lower skin at the outboard and inboard ribs. The upper skin actually wraps around the trailing edge and is riveted to the J-channel formed in the lower skin. Here’s a picture of an outboard rib…look closely and you’ll see an 0.025″ shim under the lower aft side of the rib.
You’ll also see that the skin doesn’t fit well. That’s a topic for a future post.