Note on HS Drawing

[Flying C]

I've started riveting the HS and want to be sure I don't get too far ahead of myself. There is a note on the drawing that says "Matchdrill Under-Structure using Skin as a Drill Guide". According to the instructions I am suppose to rivet these holes, with the exception of the 10 that are used to which it states "Leave Open on Top Side Only....." So, my question is what is ment by the Matchdrill note? Should I rivet these holes or should I wait until later? Thanks again for your help.
Jake

 

[Sparky]

The "matchdrill" note is essentially telling you to draw a centerline with a sharpie on the flange of the rib (after straightening the rib by fluting and adjusting the flange to match the contour of the skin, of course), then clamp the skin to the rib lining up the pre-punched holes in the skin with the centerline you drew on the flange, then drill all the holes (to #40 in this case) through the skin and the rib flange using the pre-punched holes in the skin as a guide (installing clecoes as you go). You will later deburr all the drilled holes in the skin and the rib flange and then dimple and rivet all the holes EXCEPT those 10 holes identified to be left open. Much later, when it comes time to attach the empennage fairing, you will use these open holes to match drill the fiberglass fairing and then drill out the holes to a larger size to accommodate nut plates that will get intalled on the HS to attach the fairing. ...hope this helps.

 

[rrd1_99]

Or....

you will do like me and rivet them now, even after making a note to not do so. Then you get to drill them out later when you have nothing better to do.

Roger

Much later, when it comes time to attach the empennage fairing, you will use these open holes to match drill the fiberglass fairing and then drill out the holes to a larger size to accommodate nut plates that will get intalled on the HS to attach the fairing.

 

[Rivethead]

Put a piece of tape over the holes while you're thinking of it and you will never forget and rivet them to soon.

 

[jmartinez443]

I've started riveting the HS and want to be sure I don't get too far ahead of myself. There is a note on the drawing that says "Matchdrill Under-Structure using Skin as a Drill Guide". According to the instructions I am suppose to rivet these holes, with the exception of the 10 that are used to which it states "Leave Open on Top Side Only....." So, my question is what is ment by the Matchdrill note? Should I rivet these holes or should I wait until later? Thanks again for your help.
Jake

Assuming you are referring to the inboard ribs (H404 and H405 if I recall). Those ribs are not match hole from the factory. Therefore, as previously suggested, you have to draw a centerline on the rib and line that up with the holes on the skins to drill. You also have to do the same to the last few holes in the forward spar. This is very important: make sure everything lines up perfectly and that the aft root ribs seat firmly on the both spars before you matchdrill everything. Otherwise you will end up with gaps for which you will have to make spacers later on or you might end up with edge clearance issues on your forward spar. Feel free to check out this page to see what I'm talking about. I have an 8 but i believe they use the same HS for the 7.