Question about Rudder Backriveting

Bullseye · #1 02-26-2010, 09:05 AM

Hey all,

I just started working on the rudder, and have some questions about backriveting. All comments about "backriveting is so easy, a monkey could do it" aside, I am having trouble with a couple things.

1) I bought a 12" double offset backriveting set, and am having a hard time using it. Even with the pressure up near 50 psig, it doesn't seem to want to set rivets very well. I have a feeling that the length is causing some of the force to not transfer down to the rivet as well. Anyone seen this issue with these long sets? (Please forgive the dirty workbench, ski wax soaks right into MDF. Ask me how I know.)

2) Because of my rivet set issue, I switched over to a cupped set (which I heard someone suggest), but got these results. Notice the very slight rounded corner of the rivet shop head. I can't imagine this is an issue, but it would be nice to hear you guys agree with me.

3) The furthest aft rivet in the stiffener. I am using the tank dies on understructure, which leads me to bump up the rivet sizes in some places to get the proper length unset rivet. When I read that the last rivet in the row should be set fully, I figured I would just leave the original AN426AD3-3 size in the last hole. After setting, I think the shop head is a little small. It's not perfect, but is it worth drilling out given that this area will be covered in RTV and close to the pro-sealed trailing edge? I'm good at drilling rivets out, but I'm tempted to leave it. What do you guys think?

Sorry about the large pictures. I have to weight smaller pictures here or larger picture for the build log. (I thought there was a thumbnail option here, but I can't seem to find it.)

I will agree, though, backriveting does produce wonderful results.

JonJay · #2 02-26-2010, 09:08 AM

Go to a standard back rivet set and I think things will work out much better for you. Also, make sure you have a solid backing for the steel back plate.

mototopo · #3 02-26-2010, 09:18 AM

As everything else, backriveting is easy when done with the proper tools...
I don't understand why you used a 12" double offset rivet set or the cupped flush rivet set... just use a 2.5" or 3" straight back rivet set and you will find back riveting very easy.

50psi looks to me a little too low pressure. I'm confortable with 70psi with my 2X rivet gun.

About the rivet lenght... I always use the rivet indicated on the plans without any evident problem... by the way, I'd drill out the rivet in the third picture. RTV and/or proseal used in that area have no structural effect; the RTV just absorbs vibrations to avoid cracks and the proseal on the trailing edge is just to prevent the part to slip while riveting... they are not structural adhesives.
Maybe someone more experienced than me will give you better aids...

SmittysRV · #4 02-26-2010, 09:24 AM

I have a 1/4" steel backriveting plate that I bought from Home Depot that is imbedded in 2 sheets of plywood:

http://www.smittysrv.com/more_stuff.asp?ID=46

Also, I found that if I positioned the back rivet gun perfectly vertical, the rivet went in a little lop-sided. I had to lean the gun a little towards the upward stiffener flange in order to get a perfect back rivet. My pressure is set for 38 lbs for 3/32 rivets.

trib · #5 02-26-2010, 09:52 AM

Andrew,

The replys you got above are trying to tell you that the tool you are using, the 12" offset backrivet, it definitely not the right tool. If you are unsure, talking to someone locally with experience would probably be a good idea. The offset is used for areas where you need a long reach and cannot go straight in. Anytime you can rivet without having to use an offset you will do much better with a straight set. In assembling my -6A I probably used an offset for less than a dozen rivets total. The other side is that when you do need an offset, you won't be able to make do with anything else, so you're prepared for those hard to get to rivets

. The set Smitty shows you is the correct on to use for the rivets you're working on for the rudder. It's what you should use for about 95% of your backriviting for the project. I'd also recommend you get a longer straight rivet set, similar to your offset, for use later on tough to get to areas such as back in the tail cone when you might need to backrivet.

Bullseye · #6 02-26-2010, 10:44 AM

Quote:

Originally Posted by SmittysRV

Also, I found that if I positioned the back rivet gun perfectly vertical, the rivet went in a little lop-sided. I had to lean the gun a little towards the upward stiffener flange in order to get a perfect back rivet. My pressure is set for 38 lbs for 3/32 rivets.

I definitely experienced this, too. And once I switched over to the shorter set, everything went much smoother.

I think I am going to replace those shorter rivets at the aft end.

Anyone else using a cupped set? It says right in the directions..."A small flat, cupped, or special sliding-sleeve set is used to make the shop head."

This worked well for me, I just haven't seen anyone else do it on the few build logs I've been visiting so far.

Flyfalcons · #7 02-26-2010, 02:03 PM

I used the Cleaveland back rivet set and it worked out great.

flion · #8 02-26-2010, 07:39 PM

I, too, use the set pictured by Smitty. My psi is around 30-35, which sets on a fast 3-count for me. Because the sleeve helps keep the set on the rivet, I find that it's easy to use my other hand (which helps guide the gun in normal riveting) to hold the work down. I press with my fingers on both sides of the rivet, with the set between my middle and index fingers, That seems to eliminate both the rivet tipping and also any gap between stiffener and skin. I'm finding that pressing down firmly also keeps the skin from moving around on the set plate which, smooth as it is, can still scuff a skin's surface.

N55CU · #9 02-27-2010, 09:54 AM

Try rounding off one side of the plastic on the backrivet set as this will allow you to get a little closer to the flange and keep the gun vertical on the rivet.

flion · #10 02-27-2010, 12:42 PM

That's a good point. I looked again at Smitty's photo and his set is slightly different from mine. Mine came flattened on one side and a radius at the bottom to match; I've never had a problem riveting stiffeners. Got mine in the Avery's kit 15 years ago, dunno if the design has changed or if Smitty got a different OEM, but I'd bet you can modify the slide without hurting the tool.