1. Minimum Edge Distance for rivets
. 470 rivets are 2 x the diameter and 426 rivets are 2.5 x the diameter.
2. Machine countersink
only when material thickness is greater than rivet head. This doesn't mean the total thickness it means the sheet of material directly under the rivet head.
3. #3 Rivet hole is 3/32
. When dimpling - drill the 3/32" hole, dimple and then if necessary ream to a #40. If you final drill to a #40 your holes will be sloppy when you dimple and they'll be too big for the rivet.
4. Cutting / Trimming
. Always 2nd guess Van's on their cutting dimensions. When cutting something cut it long and then trim or file to fit. Otherwise you won't have the minimum edge distance for riveting. Especially see #1 and #5
. Don't trim to Van's specs. If you do, you'll not have the edge distance along the edge you just trimmed. Go to the Search Box and simply type in R-710 - you'll see
. There are punched holes in R-606 and R-405PD that line-up with each other, but no corresponding holes in the R-802 spar. The holes in 606 and 405 are holes used for alignment of the part during manufacturing. Don't use the holes and don't drill into the spar.
7. Circled Xs
. Look on plan Drawing 3-8 of the horizontal stabilizer. On the inside edge of the left and right horizontal stabilizer you'll see circled x's over rivet holes and there's a corresponding note and arrow that reads leave Open on top side only for empennage fairing attach, 10 places. Well, don't dimple the skin or the understructure where these are depicted.
8. "Information acceptable to the administrator" Is Free.
That means it's information promulgated by the FAA. Let's face it. We ask questions and opinions on an open forum because were curious, we like short cuts, we don't have any idea where to find the information or we're just too lazy to do our own homework. Van's publishes a lot of information in the beginning of the builder's manuals and that also includes some "tricks". But every bit of information on building aircraft, wood, fabric, metal, helicopter, balloon, their components, and the rules, regulations, minimum criteria etc. is free from the FAA. Especially useful are mechanic's handbooks. https://www.faa.gov/regulations_poli...uals/aircraft/
9. Drilling a hole.
Drilling a hole is apparently an art. Different materials and different thicknesses require different speeds. Pushing too hard leads to a bent, malformed triangle. Drill bits are like dresses, there's a lot of differences. There are fractional, numbered, and lettered, angles are 90°, 110°, and 118° 140°. There's 0° rake angle, single cutting edge, double cutting edge. There's HSS, Titanium, Black Oxide, Cobalt, Carbon. They come in different lengths, some are double margin. Theres different speed drills. Then there's IPS. Drilling in Acrylic or Lexan or other plastic there's single cutting edge vs. 2 cutting edge Unibits. Then there's Rotabroach....Then there's about 50 different kinds of reamers.
10. Hole prep.
Improper hole preparation facilitates cracks. Prior to dimpling or squeezing rivets the hole has to be clean, the correct size and round. When shooting or squeezing a rivet, the rivet expands into the hole with enormous force. Any inclusion in the hole is potentially a crack later on.
11. Bending Metal
Just like there's a minimum edge distance for riveting, bending metal has a minimum bend angle. That depends on the material, the hardness, and the thickness. The overwhelming majority of A&Ps and I/As even when given the formula and charts can't tell you the minimum bend angle of a piece of metal - and of the 5% of those who can I'll bet 2% of them can't give you the set back. Take a scrap piece of aluminum and squeeze the daylights out of it and then put it under a 10x or better magnifying glass. You'll see where the clad plating starts separating from "work hardening" the material from excessive pressure. (I'm sure, I'm in the 95%)
12. Work Hardening
Dimpling and bending metal and hammering on it via riveting work hardens the metal. Use as light a blow and as few blows as you can from a rivet gun.
13. Scrubbing the aluminum coating off AlClad
. The Aluminum is there for corrosion protection but some people use Scothcbrite to scrub the protective surface off the AlClad so they can apply a protective surface (alodine). The pure aluminum coating is only 2%-5% of the material thickness so on a piece of .020" the pure aluminum coating can be as little as .0004" thick. Scrubbing the corrosion protection off to apply another corrosion protection never made much sense to me.