Wednesday, October 21, 2009

Thou Shalt Commit Rivetry

I started out the night with some countersinking on the big old getting-tired-of-seeing-it vertical stab spar. Countersinking is done to provide space around a hole for a rivet head to fit down into so it will be flush against the skin. Imagine it as a very tiny toilet bowl. Or, just see if you can pick it out in this picture:

Four of the holes are countersunk. The big ugly black thing to the left of the metal is the countersink tool. It goes in the drill just like a drill bit. The bit is inside the black cylinder and comes out when downward pressure is applied. The amount of bit that comes out is set by adjusting the cylinder by twisting it in or out on the threads. You set it for any given job by testing it on a piece of scrap metal until a rivet sits flush against the metal when placed into the hole. With the precise adjustment made, the bit then works differently on every single hole you try to countersink.

Well, at least it does when I do it.

The countersinking of those holes was the last task before riveting that part (and its mirror image part) onto the spar. That was done with blind rivets. Blind rivets are nice because they don't require access to the other side of the metal as is the case with the solid rivets I squeezed in last night. That's not important with the spar I'm working on, but it will be very important later on when doing things like riveting skins onto wing ribs.

It's really pretty easy. The rivet has what is essentially a nail running through it. If you pull really hard on the nail, it will compress the rivet. If you pull hard enough, the nail will break loose and the rivet will remain in place.

Here's a before and after view of a blind rivet:

You can also see where I did some test holes to set the depth of the countersink tool.

It didn't take long at all to pull the eight rivets that would permanently attach those two parts to the spar:

This is the side that will be visible, so the "manufactured" rivet head is on this side:

This side will be inside the tail, out of sight forever. So this is the side where the "shop" head of the rivet goes:

All in all, a good night in the shop. Nothing broken, in other words.

Eight rivets down, 12,492 to go.


Julien said...

Thanks Dave for all the detailed explanations and photos, I learn something new with every post. The way you document the proces makes homebuilding a bit less intimidating for those of us with that dream at the back of their head. Whenever the topic comes up again, could you say a bit more about how the cleclo thingies work? Thanks!

Ageless Stranger said...

You're not really considering pulling all those blind rivets with a hand rivet gun, right? You'll have a really strong grip on your right hand if you do!

DaveG said...

GregJ -

No, I have a pneumatic puller in the hangar. When I have big chunks to do, I'll haul everything out there. It will all end up out there eventually since I have a space limitation in the basement: if I let anything get too big, I won't be able to get it out!

DaveG said...

Julien -

A picture is worth 1000 words, and a video is probably worth 1,000,000:

Julien said...

Thanks for the video! It did indeed provide me with all the information I was looking for about clecos, and then some. Thanks! The other videos look very interesting too.

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