Back to work - Tech Counselor Visit and Access Panel Progress

Technical counselor Jim Elliot come out to the house to check on my project and answer some burning questions about my current dilemma. Jim has built or helped build many experimental aircraft and has a great deal of avionics, electrical, and mechanical expertise in all types of aircraft. So it was a great relief just to have someone with that kind of experience help sort through these issues.

The wallowed out holes on the tips of the first two ribs are still going to be a challenge, but  thanks to Jim I now have a plan of action to try to address that problem, and several possible solutions depending on what happens. He also answered several questions about rivet and nut plate placement and effect on loads being applied in certain areas as it relates to the mod that I am working on. I'll detail that more later.

For tonight, I'll just focus on the question about how many rivets I need to put in the plate that simply covers up the old hole. I was glad to hear Jim tell me that I do NOT have to turn that plate into a piece of Swiss cheese by drilling a million rivet holes into it. I only need to place enough rivets around the perimeter of the plate. The reason I am able to do this, however, is not immediately obvious, and all the books that I read to try to find an answer to this question did not really address it much.

The reason why I only need perimeter rivets is that the loads for the majority of each bay of the LE are carried by the rivets that attach the skin to each rib flange. The mounting brackets for an access panel act as I stiffener to help replace some of the strength that is lost when the hole us cut out. The last part of this has to do with the objective to ensure that the loads being applied to the LE while standing still and while flying are allowed to transfer across the structure as designed, without being concentrated too much in one area. For this reason only a minimum number of rivets should be used in areas other than the primary area where loads are designed to be transferred across the part, i.e. the ribs.

So Jim told me to use the width of the nut plate rivets that otherwise would have been used to attach the nutplates for the mounting screws as a guide, and to try to apply rivets around the perimeter of the plate using that spacing. the #8 K1100 nut plates have a rivet spacing of 22/32 of an inch, or 11/16ths. Tonight I started measuring out the rivet line around the perimeter and pre-punched a few of them. Here is pic. I am using 1/4 inch spacing around the edges and will fill in the remaining gaps using the nut plate rivet spacing as much as possible.

Ona final note, yesterday was the first time I had removed the entire LE assembly from the wing since I fabricated the new access panel hole in the subskin and created the patch plate for the old hole. I was also very happy to find that the holes I had drilled through my fabricated rear rib flange additions to the second rib appear to have worked out fine as far as edge distance is concerned. SO no more worries about that.

A lot of stuff about a stupid patch plate, but at least I have a plan to move forward.

KPR