Why aren't sheets pre-dimpled?
 

I don't have any experience with Van's kits yet...still doing my research. It appears that while nearly all the sheetmetal arrives with the holes already punched, the builder still has to do all of the dimpling. Anyone know why Van's doesn't do it? They should be able to buy a tool for their turrets to dimple them right in the machine. Wouldn't this be a major time saver?

The holes would have to be bigger and debured so that's not going to happen. I would love for it to be done though, I HATE dimpling

Dimpling? Dimpling's easy!
 

It's far worse than you think. Dimpling is a no-brainer. Tedious, tiring, boring, yes. But honestly not a big deal. If I could choose for the factory to take the kit one step further, I would choose to have all edges deburred. After that, we could discus...oh wait, Vans DOES in fact debur edges. Heck, come to think of it, they dimple too!! It's called a Quickbuild.:p

If you choose to slow-build, then a significant part of enjoyment is the building process, and dimpling is just a part of it.

Of course, you could just use universal heads everywhere. You'd loose a couple MPH off the top end, but otherwise, no big deal.

Just order the empennage and get it over with!

Anyone know why they don't punch the holes out to final diameter?

Tooling Marks? Stress?
 

I'm by no means an authority, but someone explained to me that the punching process leaves tooling marks in the hole, and potentially stress risers. During assembly, all pieces are clecoed together and then final drilled to the appropriate hole size. The final drilling process removes the tooling marks and stress points caused by punching, making a nice, clean, shiny hole.

Personally, I also think it helps achieve a tighter fit in the pre-punched kits, since there is less clearance with the clecos, helping the builder produce a better final product.

Can anyone with professional industry knowledge confirm, deny, etc?

I didn't realize all of the holes get drilled to size. That explains it!

If you want complete plane, why don't buy one? We just have to do something that this would be experimental and we would actually build it rather than Van's... there are many places where Van's might have helped a bit but after all somewhere has to be the line where they stop. :o

This is why
 

See section 5B of

http://www.vansaircraft.com/pdf/section%205r9a.pdf

and you will notice the ragged edge left by shearing and/or punching holes in aluminum. The holes are prone to crack on the exit burr without a cleanup step to remove it before dimpling. That is the whole point of builder labor. The builder puts in the handwork labor to compliment the work done by Vans to come out with an inexpensive aircraft. There is some FAA rule about 51% or something too...

51%
 

Would dimpling come too close to the 51% we're supposed to do?

A thought.....it would definitely increase cost as well.

My .02

Yeah, but
 

the RV-12 comes with its holes prepunched to the final size. Maybe because its a slow(er) airplane so will put less stress on the airframe and the fasteners, etc, etc.
Steve