Question on rivet length

OK, ready to rivet skin on hs....nose ribs done, spar in place, skin clecoed to spar and main ribs. Rivet call out for skin to spar is -4.......I placed a -4 rivet in and it looked long, marked it and measured .162. 1.5 diameter is .141 for a -3 rivet. FAA guide has a 1.33 min. Diameter to 1.5 diameter of the shaft for pre driven rivet. The -3.5 rivets looked right, and I think it measured + or - the .141. ? Should I go ahead with the 3.5's or do I do more investigating? Thank you for your thoughts.

Use whatever the plans say. Its that simple. If its just skin to ribs, its probably a 3.5.

You will get times where the river length specified is slightly longer than the 1.5 times diameter spec once it has gone through all the layers. One example is the F-601A-2 to F-601N to F-601G-1 to F-601J AN426AD4-9 rivets. At their -9 length you'll find they'll tend to bend over, but the -8 is slightly too short. Take a little off the end with the disc sander until they achieve that magic 1.5x diameter length exposed, and they'll squeeze fine. Just use common sense and your rivet gauge and you'll be fine. Just make sure you have all the required layers of material in and that the rivet doesn't appear too long because you have missed out a spacer, hinge line etc.
Van's plans/instructions are good, but they're not perfect, so keep your eyes peeled.
Good luck.
Tom.

I find a rivet gauge comes in very handy. Between the plans and the gauge, you should be able to choose the correct length.

http://www.cleavelandtool.com/One-Piece-Rivet-Gauge/productinfo/RLG1/#.Vz1e-XCSIva

http://www.aircraftspruce.com/menus/to/gauges_rivet.html

Note that when you dimple a hole it's effective diameter increases a bit.

This says that you should err on the side of a slightly longer rivet than a shorter one when you use the rivet length gauge.

The skin/fwd spar/main rib flange combination on my -8 HS ended up with 3-4 rivets. I spent a little time worrying over this as well.

FAA guide?

I'm new here. (Going to use that as long as I can)

AC 43.13-1B. Available online for free from the FAA. Covers rivet length requirements and a whole lot more.

I have a gauge as mentioned earlier. They are quick to use and not expensive. The problem is sometimes you are right between sizes and I don't have a cutter. I tend to use the longer one in those instances.

I have found numerous places that for whatever reason the rivet called out in the plans is not exactly correct. Maybe only off by 0.5 but still...

rapid_ascent said:

I have a gauge as mentioned earlier. They are quick to use and not expensive. [...]

Click to expand...

A word of caution regarding rivet gauges - at least the two we have reflect 1.5 times the rivet shank diameter. Van's however requires on 1.3 times as the minimum diameter, what is also in accordance with MIL specs. This means, that you do not necessarily have to drive the rivets so much that they do not pass in width anymore. If you do (I am speaking from experience, after some not so great advice from another builder), the driven head might as a result be too short. I don't think that we ever had this issue with #4 rivets. All #3 rivets, particularly those in dimpled holes, however ended up being too short if we tried to make them so wide that they would not pass the 1.5 times gauge anymore.

I therefore suggest to measure the actual gauge dimensions and to compare them with the specs on Van's website (table III): http://www.vansaircraft.com/public/Specs.htm.
Resulting from this learning experience, we made our own #3 1.3 times gauge by drilling a 1/8" hole into a scrap peace of aluminium.