Building, testing and operating an experimental aircraft

Wing Work

09 Aug 2014

It seems like a hundred years ago that we stopped working on the wings, but we still had a few items left to accomplish. We hadn’t riveted on the bottom skins, and we’d never installed the flaps and ailerons, so after Oshkosh, we set ourselves to these tasks.

Riveting the Bottom Wing Skins Riveting the Bottom Wing Skins

We began by riveting on the bottom wing skins, a project that is considerably more difficult than it looks. The skins must be peeled back in order to reach the rivets near the rear spar, making proper planning essential. It’s easy to get ahead of yourself and rivet yourself into a corner, so to speak.

Making the Stretch Making the Stretch

The trickiest area to reach was probably the wing walk ribs on the right wing near the fresh air vent. We had, of course, already installed the SCAT ducting for this vent, and it was difficult to maneuver the bucking bar onto the adjacent rivets.

Setting Aileron Travel Limits Setting Aileron Travel Limits

The ailerons and flaps had been finished years ago and stored away, but we’d never installed them on the wings. So, we layed out everything per the plans to set the aileron travel limits.

Aileron Bellcrank Jig Aileron Bellcrank Jig

I affixed a 2x2 onto the wing tip to act as a chord line extension and marked it with the proper “in trail” position for the aileron. Then I installed Van’s handy bell crank jig and adjusted to rod end bearings until the aileron tip was properly aligned.

Aileron in Trail Aileron in Trail

Once the aileron was properly in trail, we used a SmartTool digital level to measure the up/down limits in degrees, using the travel limits spelled out in the Flight Test section of Van’s Preview Plans for guidance.

SmartTool Level SmartTool Level

We happened to notice at Oshkosh that many builders use a wide nylon spacer washer on their inboard aileron hinge, which acts as a bump stop for the aileron, effectively setting the travel limit. I like this idea better than trying to install the limit stop supplied by Van’s, so we may add something similar once the wings are installed. At this point, however, no stops were added.

Aligning the Flap Aligning the Flap

Next we set about aligning the flap trailing edge with the aileron, and drilling the flap hinge, a process which was eerily reminiscent of the elevator trim tab layout we’d completed nearly four years ago.

Drilling the Flap Hinge Drilling the Flap Hinge

Two problems arise when installing the flap hinge: (1) you need to ensure proper edge distance on the hinge when drilling your rivet holes, and; (2) you want the trailing edge of the flap to align with the trailing edge of the aileron. These two requirements are at odds with each other.

Flap Hinge Clamping Method Flap Hinge Clamping Method

Van’s ships the MS20257-3 aluminum hinge with the wing kit, which some builders find to be too narrow to meet both requirements, so they order a -4 (wider) hinge. By careful layout and attention to both of these parameters, we we able to use the -3 hinge and successfully meet both the edge-distance and trailing-edge constraints.

Riveting the Flap Hinge Riveting the Flap Hinge

Once these tasks were completed, we stored the wings back in their cradles with flight control surfaces installed and inspection covers in place. I’m sure we’ll have to do more tweaking with travel limits, etc., once the wings are mated with the fuselage – sometime in 2025. :/

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