Holes on airframe somehow losing alignment

[billdz]

Hope this isn't too dumb a question, but it has happened to me 3 times and I can't figure it out. A rocket needs to be connected to a coupler or nose cone with plastic rivets or shear pins. I connect the 2 pieces, drill holes through both while they are connected, mark the locations with a marker, and then insert the rivets. All looks good and the flight is perfect. A month or 2 later, when I prep the rocket for its next flight, I put the pieces together but now the holes are out of alignment. I twist and twist but no joy, and the only solution is to drill new holes.

Any thoughts on what might cause this and how to prevent it? My first thought was that the switch band on the coupler had moved, but it seems to be well glued in place.

Thanks,
Bill

 

[JoePfeiffer]

I've seen this when I've accidentally rotated 180 degrees the second time I assembled (and my holes weren't positioned quite as precisely as I thought!)

 

[teepot]

I've had the same problem. I started drilling a depression half on the switch band and half on the body tube as a reference mark. when the halves line up so do the rest of the holes.

 

[dr wogz]

Depending on the materials used, I would suggest these materials differ with environmental changes: heat & humidity..

but I wouldn't expect them to 'move' that much, to make them that much out-of-alignment..

I also mark my AV bay tube with "up" or an arrow pointing up / or "nosecone". (You may have your AV bay up-side down)

I have also marked my AV bay with a line, and marked the inside of the body tube with a mark, so they also all line up..

 

[kalsow]

When drilling multiple holes around a tube, offset one of them vertically +/- a half inch. The "weird" hole will be your key so you always reassemble it the same way.