Wing Walk Doubler Lesson Learned

Just in case anyone else has this - I haven't seen it before on here.

I am assembling the left top skin on the left wing after previously having it together to c/s the rivets over the inboard 4 ribs where the wing walk doubler fits under the skin. When I put it all together and checked the fit of the rivets the c/s holes didn't line up well and the heads protruded, something that did not happen when I made the c/s.

So I put a couple in loose, and took off all the clecos where the doubler was. Then after putting in a row of loose rivets and seeing them more flush, I clecoed along that line. Repeated toward the inboard-most rib and now they are all as they should be.

So word to the wise - fit the doubler well prior to starting to rivet.

Also, the plans say to leave the c/s flush to 5 mil shallow, not deep. If the heads sit a little proud, why does that not matter? Is it because non-skid goes over the top anyway?

I would say it's because if you countersink too deep the rivet will not be tight when you set it. It will pull he head up against the puller and it will not be sitting down into the countersunk hole. The only way I can think of to set a too deep hole is to have a small washer the same diameter as the rivet with a hole in the center the same size as the mandrel and place it over the mandrel before placing the puller, but I would doubt Van's would want anyone to do that.

flush!

If the heads are proud, the treadgrip will wear over the heads and prematurely wear through....??
Roger

Maximum strength of a rivet joint is achieved when the 426 rivet is just a bit proud.

From pg16-02 Rev 2

Machine countersink all the rivet holes that correspond to the W-1027A Wing Walk Doubler - Fwd and W-1027B Wing Walk Doubler - Aft in the W-00002 Top Inbd Wing Skin for the head of an AN426AD3 rivet. Machine countersinks that are up to .005 too shallow are acceptable and are preferred to countersinks that are too deep.

Previous RV kits called for dimples, not counter sink of the top skin for the douibler area.

For those still building I suggest two alternative approaches:
1. Dimple the top skin, counter sink the doubler, leave the ribs as is.
2. Dimple the top skin as well as the doubler and ribs.

Carl

I left mine slightly proud per the instructions and the wing walk material (Ray Allen from ACS) covered them completely. You cannot see any bumps in the wing walk material so I can’t imagine it wearing through. My motto while building……Don’t over think it and follow the plans.

I'm glad to see my 6 yo thread resurrected; once it was sanded for painting the ever so slightly proud heads were invisible.....