Wing Alignment holes

[racaldwell]

I forgot one of the mount block bolts went into the web of the Tee cap strip. It's been an eternity it seems since making the spars.

Rick Caldwell
Xenos 0057

[sonex1374]

I asked Pete Buck that very question as to whether or not he had any concerns regarding leaving the 3 alignment bolts in place in a completed wing. The question was asked recognizing that leaving the 3 bolts in place would, in a small way, alter the manner in which the loads are transferred from the left wing spar to the right wing spar and vice versa. Pete had no objection to leaving the 3 bolts in place.

Those 3 holes are located in the mid-point between the top and bottom spar caps, and lie very nearly on the “neutral axis” of the spar. The web material on the neutral axis is neither in tension or compression, but rather just sort of idle from a bending load perspective. Locations holes on the neutral axis is preferred because the holes don’t detract from the strength of the web when placed there. Correspondingly, filling in those holes doesn’t really make the spar any stronger either. So if you analyze the spar strength three ways, 1) no holes, 2) open holes, and 3) filled holes with bolts the results don’t really change.

There are some other dynamics going on in the web that can be affected by holes, even ones located on the (bending) neutral axis, but those other conditions are not the limiting design condition on a Sonex spar. Essentially, the spar is so overbuilt that it just doesn’t matter.

All this is to say, those holes aren’t a problem, but filling them with bolts isn't either. Take your pick.... it’s ok.

Jeff