Kobwo

Kobwo

Active Member
Good Mornin,

I ran my fist line of rivets today along the front spar of the HS. I have the pressure set to Checkoway's chart for a -3.5. 37psi and hit it for 1.5 seconds. I also have the flow regulator on the gun (which is a 3x with the non-swivel mushroom set) set so it doesn't hit so fast that I can't control it. (I was told that the little regulator on the gun doesn't change the pressure but how quickly the gun hits.) The rivets set in 1.5 to 2 seconds and the gun is very controllable, however, the skin around the rivet is a little concave after setting. I have seen this on just about everyones airplane but there seems to be a few here on the boards that can shoot rivets and still have the skin around them lay almost entirely flat. Any techniques to shooting the rivets and still have the skin lay as flat as possible? :confused:

Here you can see what I mean
DSC_0029.jpg


In a different light it really shows up,
DSC_0027.jpg


Now these pics make it look more severe than it is because of the lighting but you can see what I mean.

All ears and thanks for your time,

Cheers
 
Last edited:
Looks Normal

That looks normal to me, and just about every RV I've seen looks like that. I've heard of some people that back rivet everything they can, which will give you a smoother surface finish. But I honestly don't understand how one would do that. Rivet on.
 
rivets are fun

Hi Shown,
The rivets look normal to me, a common problem is too much pressure on the gun can also cause denting around rivets, this is more apparent on thin material, a little less pressure when riveting will help. A good dollie or as you guys in the US call them bucking bar will help put down the rivets with less hits on the gun.

Cheers,
 
nick

Looks OK. For a little smoother finish, let me suggest a little less force when dimpling the skin. When you dimple, drop a rivet into the hole.
If you can run your finger across the top smoothly you're go to go.
 
As a very good pal of mine taught me, give the back side of the rivet a gentle tap with a hammer and punch or just the hammer. This will pop the rivet/skin suck in back to flush and make a big difference. Try it, it really works.
 
I used a soldering gun and a straight edge. The tip of the gun has been rounded over. I then just score the vinyl. I went too slow the first time I did it for a couple of inches and it left what looked like a scratch in the aluminum. 1 inch per second seems to work. Thanks C-FAH Q I will have to try that when I can get in there to do it. Not much room for a hammer inside.
 
RV6AussieNick said:
Hi Shown,
The rivets look normal to me, a common problem is too much pressure on the gun can also cause denting around rivets, this is more apparent on thin material, a little less pressure when riveting will help. A good dollie or as you guys in the US call them bucking bar will help put down the rivets with less hits on the gun.

Cheers,
Click to expand...

I'm gonna try a little less pressure and see if that helps. I'm using a tungsten bar for the dollie.

Any more techniques?

Cheers
 
Also make sure that the skin and ribs are FULLY dimpled. Not dimpling the skin fully could result in an appearance like this. Just a thought.
 
jrvssgl said:
Also make sure that the skin and ribs are FULLY dimpled. Not dimpling the skin fully could result in an appearance like this. Just a thought.
Click to expand...

Yea, I was thinking that as well. I'm using a DRDT-2 to dimple and when I set the dies, I close them until they touch and then a 1/2 a turn. This seems to make a really nice dimple and when I put a rivet in it looks like it fits perfectly. I've been told that you can't over dimple.
 
Bucking bar pressure required

Make sure you are holding enough pressure on the bucking bar. If you do not have enough pressure against the shop head side of the rivet, the rivet gun will tend to create a large dimple on the skin, as you are seeing. Also, make sure you keep the bucking bar tight against the rivet until the gun stops. Drawing the bar away from the rivet too soon, or even decreasing pressure can cause this.
Things to try...push out the rivet with the bucking bar, then push it back in with the rivet gun set, maintaining pressure with the bucking bar. This makes sure you have contact with the rivet and gives you a feel for both the bucking bar and rivet gun, on that rivet.
I think it's easier to get good results by using several brrp, brrp, brrp applications of the gun rather than one longer burst.
You should be able to rivet and obtain a really smooth skin surface, even riveting by hand with a rivet gun and bucking bar. Just takes some practice or someone there to get you started on the right path.
 
My sheet metal teacher told me "let the gun do the work". Don't push the gun in to the work piece. Only maintain enough gun pressure to make sure the set doesn't bounce off the rivet head.

The bucking side is where you have to work at it a little. Place the bar on the tail of the rivet and let the weight of the bar work for you. When the shooter starts to shoot, keep light pressure on the bar until you feel the tail of the rivet start to flatten. Then push back against the shooter. If you're shooting and bucking all by yourself, then it's a little easier to feel the balance at work, but a little more awkward to make it all work together.
 
DRDT?

I agree with Jarvis. These look just like some dimples I've seen that were done with a DRDT-2 and not fully dimpled.
 
That can also happen if your c-frame table is not flush with the height of the dimple die. Upon impact of the ram, the skins can dent like that.
 
Here are the dimples

For your inspection,

These were created with a DRDT-2 and not a conventional C-Frame,

Dimple%202.jpg


Dimple%203.jpg


I'm not a dimple expert but they seem to look really good.
 
I used a flat flush rivet that has a rubber ring around it so you don't damage the skin. I tried the one with the floating rubber head but did not have a lot of luck with it. On the practice kit I use just a flush rivet head and was all over the place riveting so I would recommend that you get one with the rubber around the head and it will keep you in one spot. Make sure you don't have too much pressure because it does not take a lot to set these 3.5 rivets. If you put one is a squeezer you'll see what i mean. I then use one of the bucking bars that I would get against the bottom of the rivet and gently push up just to make sure that I was on the correct rivet. since most of this is by feel.
The I could actuall roll the bucking bar on the rivet and make sure I was square to the skin.
Make sure you hold the gun squarely on the skin and keep the pressure on the rivet/skin so the gun should not bounce at all. After I did a couple of rivets by feel I would do a few more then check underneath to check the shop head size. Like one fellow said make sure that when you cleco the skins. use a lot of cleco's at least everyother one and check under neath in the sturcture to make sure the skin pulls down tight. Make sure your dimples on the structure are well formed so the skin pulls tight.
http://rides.webshots.com/photo/2796697140030256016DaMZwR?vhost=rides
Perhaps this will help you. The biggest problem I had was with the AEX wedge on the rudder. But it turned out okay by a couple of RVers.

Smilin' Jack
RV build pictures on webshots.http://rides.webshots.com/album/579665919lGvLyE?vhost=rides
Waiting on wings.
 
One last word,
The fellow up above that stated do simple little birps with the gun works better than using a 1.5 second burst when you don't know what your doing below and if your bucking bar comes off before you stop the gun you'll dimple the skin. make sure the gun is stopped before the bar comes off.
Jack
 
How are you supporting your work?

Kobwo,

How are you supporting your work? This also makes a difference. Some rivet their HS horizontally some vertically. What were you using to protect the opposite surface? Carpet? What happens is that some of the energy from the gun moves the entire HS if it is supported by carpet, foam etc. This means some of the energy is absorbed when the HS moves. Since not all the energy goes into setting the rivet you need to stay on the rivet with longer bursts. Longer bursts aren't always good.

My advise is to make sure your work is well secured. Minimize the movement. Short bursts and minimize the set pressure (not gun pressure) on the rivet just enough to keep the set on the skin while riveting. You don't need to push too hard. Let the bucking bar do the work.

I hope this helps.
 
Avery Swivel Head Flat Set!

Advice; Sneak up on the air pressure till it works like you want it to.
Do not set it to the recommendation of someone else's tool set up.

Additional story,

When I first started Avery sent me a swivel head flat set with an orange guard around it. He said I had to have one.

Well I received it with some other tools I needed.

I am also an A&P mechanic, back then an IA too.

In my mind I said "I dont need no stinkin rubberized rivet set" so I did not use it for 13 years of my very slow build project.

Then one day when I had no helper and I was riveting on the bottom tail skin, I had to really extend to rivet and keep my old set really straight.

I thought, "Nobodies lookin" I will see if it would be easier with the swivel head set with the rubber bootie.

It allows for some mis-alignment.

IT WORKED GREAT! even on the thin skins, so I did what I could that night and the next day I had a newbie rivet driver use it with perfect results also.
 
Mushroom Rivet Set

Check the face of your rivet set. Mine is about 1" diameter with a VERY slight convex surface. I have seen some that are smaller diameter with a pronounced convex surface, this may cause the indentations you are seeing.
 
jrvssgl said:
Also make sure that the skin and ribs are FULLY dimpled. Not dimpling the skin fully could result in an appearance like this. Just a thought.
Click to expand...

Jarvis is 100% correct. I've done quite a peer inspections of RVs and IMHO the folks with the DRDT2 dimpler seem to underdimple. Not that it's the fault of the DRDT2 -- it's only what I've observed.
 
You must log in or register to reply here.