Rudder is giving me trouble

OK I think I know what is wrong but I will ask the gallery. I started to rivet the stiffeners on to the rudder today and it has been giving me fits. I can't seem to consistently get them set straight. My back rivet set was too wide so I flattened one side, this allows me to get straight over top of the rivet. My back rivet plate is recessed in a 3/4" piece of MDF that is plenty big.

I tried to be careful and not deburr too much, but I think between drilling and deburring the holes have enlarged to the point that it is difficult to set a rivet straight. I have done one side of the rudder and quit. I am giving thought to ordering a new skin and set of stiffeners and try again. I am not sure I could get all the bad rivets out without trashing the skin. I did not have this trouble with the VS or HS so I am not sure what else to do. I was taught a trick at a building class that I guess is not an approved technique which is why I did not do this on my rudder. But this person would dimple the holes without drilling size, (just for the stiffener holes). I must say it made for nice rivets. I feel like I should have gone that route. My other thought if I get new parts is to drill to #41 in hopes the holes don't end up too large.

The first photo is to show how much room there is around the rivet, the other photo show some of the bad rivet. I think I would have to drill out at least 20% of the rivets on the side I have done. BTW, the practice project back rivets came out great, I don't know what is up with this!

What does it look like to you builders out there, are the holes too big and that is why my rivets are falling off? I am making a good effort at holding he rivet gun plumb and holding the rivet set with my fingers so that it does not move. Also, I ease into the set and tap a few time before going more heavy on the trigger, I have the gun set at 40 psi.

Thanks for any help or suggestions!

The top of the tipped rivet does not appear parallel with the rib, the set had to be tipped for that to happen. I assume your using the set that has the spring loaded plastic collar? Try placing the set over the rivet, but dont compress the collar yet. Tip it front to back and side to side untill the collar is sitting square then push it down without moving the rivet gun. The holes always enlarge when dimpled, I measured it once and found it to be several drill sizes over. Perhaps try pre squeezing the rivets in a squeezer untill they just fit through the skin/stiffener?

I am not a back rivet expert by any stretch of the imagination but I felt compelled to respond because I have had so many problems with this myself.

I have found (the hard way) that you not only have to be careful about having the back rivet set square but it has to be pretty much centered to get good results. It looks to me like the center of the rivet head in your photo has a little bit of a scuff. Usually when this happens to me it is because I am off to one side a bit. I actually look through the little hole in the side of the white collar on by back rivet set.

Be patient and persistent and it will come.

Bill Finnell
Tucson AZ
RV-8 Tail

back rivet

Mike,
your top photo looks pretty normal. Instead of drilling each hole #40, I now ream every hole with a #40 reamer, less deburring, and very consistent with the hole sizing. Avery and others sell both #40 and #30 reamers-now I can't live without them.
Second photo looks very familiar. I took that stupid nylon bushing off my back riveter-it pushes the riveter off center due to the stiffener flange. With my left hand I place index and middle finger either side of dimple capturing exposed back shooter less nylon bushing between my fingers, and pushing down on metal surface. Carefully tap the rivet, teasing the trigger till it snugs up dimpled metal. Then finish it off to a good shop head. It will pinch your fingers if not carefull, but I found that I could consistently get perfect shop heads with this technique. You can also see the rivet being formed, and if properly centered and square on the rivet shank, this way. That nylon bushing causes it to be BLIND riveting.
Hope that this helps,
Mike H 9A/8A

Mike
How long are you driving the rivet? It looks over shot to me. Also try to set your gun so you squeeze the trigger all the way for a second or so to set the rivet. Don't try to feather it in.

One thing that makes a big difference in getting consistent rivets is to regulate the air flow at the gun and run max pressure in the air line. That way you don't get an air pressure drop when you start riveting. Keeps you from accidentally smashing up your plane when you go between your drill and rivet gun also.

When it comes to riveting the rudder stiffeners ( I remade a cracked rudder this weekend) tape all your rivets in first then when you are riveting press down on each side of the rivet with your figures to hold the stiffener tight to the skin and back plate. that will also hold the rivet centered in the hole.

Cam

Dimple Die Set?

I just finished my rudder stiffeners and they came out really well. (Except for the part where the plate was not under the rivet and I dented the skin, and then made it worse by trying to fix it, which caused another dent...doh!).

Anyway, it does look like the holes are somewhat big. Something to check, that hasn't been mentioned is the dimple die set. Perhaps you had a -4 set and it stretched the hole? Also, I dropped the pressure of my 3X gun down to 37-38psi, because I thought 40 was too much.

Get the back rivet set from Cleveland Tool. It is smaller in diameter and the outside plastic piece has a much thinner wall thickness. It will allow you to center the set and your problem will go away. Buy one now as you have a lot of back riveting to do and the Avery set is just too bulky. Don

Mike,

I did the exact same thing on my RV-7 rudder a few months back, see here:

http://www.vansairforce.com/community/showthread.php?t=20229

I ended up re-ordering skins and stiffeners (now I have a lot of scrap metal to play with!) and deburring VERY lightly, still drilling with a #40 (though #41 may work better), and gently dimpling with my C-Frame (no DRDT-2). The rivets still had a little bit of slop in the hole, but this is kind of the nature of the beast when you drill and dimple thin skins. I just forged ahead and back riveted and they came out great the second time around.

I thought about just dimpling the un-drilled holes too, but when talking to other builders, began to fear this would cause cracking. I just chocked the whole thing up to a $150 mistake and a lesson learned.

I would drill out the bad rivets and try it again. I had good luck doing #40 rivets at 35 psi. The image of the crooked rivet looks to me like the gun was not straight over it.

Make sure the back rivet plate is flush with and not below the MDF surface.

Thanks for all of the input. Just to answer a few of the questions and add some thoughts I have come too. After more thought and looking on line I do not think my holes are too large, just the way they came out, I am careful and up to now no problems. I also used a #40 ream for these holes.

The rivet set I think is my problem, due to the size it is not easy to make sure it is square over the rivet, I hold the set secure with my fingers but perhaps it is not sitting straight. For those buying tools I would avoid the back rivet set sold at Planetools, however other than this tool I have been happy with my tools and service from Planetools, I would still buy tools from them. This set is just too large to rivet the stiffeners.

I am using the tap and drive technique, I tease the trigger and let it tap a few times to hopefully expand the rivet some and get the parts to tighten up I then give the trigger a good squeeze for what is less than a second, you can hear the sound as the rivet sets. I think I will take the collar off and try it that way and or find another rivet set. I may see if I can borrow one from a -7 builder here, I think he bought all of his tools from Cleveland. I bought my tools from all of the big tool suppliers. I basically chose what I thought was good from each, what I did not know was the size of the back rivet sets, Cleveland seems to have the narrowest set, you don't know what you don't know when you a initially buying tools. Thanks for the help gang, it is a new day and I will try again. Time to get more practice drilling out rivets.

I still have not decided to get the new skins, I want to see how drilling out the bad rivets go. I think I will have to re-dimple some since the clenched rivets have fallen off and crimped half of the dimple. I just don't want any weakness since in an aerobatic aircraft the rudder a control surface that gets a lot of stress. I want that sucker at design strength or better, which is why I may go the new parts route, only $95 for new parts that and a new rivet set i might be better off. I know from experience how drilling out rivets can make things worse but most of these rivets are just too bad to leave in. Up to this point I have only trashed one part (a stiffener), I guess every builder at some point has to spend some money on new parts to make up for errors.

Cheers

I'm real glad to see this thread.

I was having similar problems with the same tool. The supplier sent me a new one free of charge, since I thought it was a defect in the tool (the head of the rivet set seemed curved, not perfectly flat). The replacement tool seemed a little better, but this may have been due to me changing my technique a little (more air pressure/less shooting time).

I would be very interested in the results with the new tool, before I go buy another one myself.

I had the same problem when I first started back riveting. I felt I wasn't holding the gun perpendicular to the rivet even thou it looked like I was. So I hot glued
a small bullet level to the back of the rivet gun and when the bubble was in the middle shot the rivet and son of a gun they all came out perfect. With enough practice I didn't need the level any more. Bit of a crutch but when your first starting use anything you can.

Just a thought - are you compressing the spring in the back riveting set so its face makes contact with the end of the rivet before you squeeze the trigger ? The rivet should be firmly held between the back plate and the face of the rivet set before you shoot.

Rivet technique

mistergerf said:

Just a thought - are you compressing the spring in the back riveting set so its face makes contact with the end of the rivet before you squeeze the trigger ? The rivet should be firmly held between the back plate and the face of the rivet set before you shoot.

Click to expand...

To answer your question, yes. I press with my free hand the stiffener and hold the rivet seat collar so that it can't move around (in theory). I then apply downward pressure with the rivet gun so that the set contact the rivet. I then apply light pressure to the gun so that the set starts to tap a bit, after I think it has started to expand the rivet I pull full pressure on the trigger for less than a second it seems, I stop if I hear the sound change, which is an indication the rivet has set.

I took a builders class and built two aileron sections for practice (Van's training project). During all of this back riveting did not seem like a big deal, I thought it was the easiest type. I honestly think it is the rivet set, the set is wide and the head is curved which might make for a problem striking the rivet squarely.

At any rate I bit the bullet and ordered new parts after trying to redo some of them. I can drill out rivets just fine without making the holes bigger, but setting the new rivets gives me the same trouble, but presqueezing the rivets does help. Rather than trash the thing more I will just start a new hopefully with a new rivet set.

Cheers

Mike-

You've met Steve Lindberg, right? You might give him a call. I'm sure he'd be happy to come over, or have you come over, and he might have a different rivet set or different technique that might help you. I'd offer the same, but I doubt you want to drive 2.5 hours!

I had no trouble doing these, and back riveting is usually pretty straigtforward, so I'm suspecting it is just your particular back rivet set or an inability to get both layers to sit completely flat on your back rivet plate. FWIW, I have the Cleaveland back rivet set that is about 0.5" wide.

Hang in there.

This may sound odd but I found I got more consistent shop heads if I oscillated the rivet gun slightly as I drove the rivet. Since you now have a practice rudder, give this technique a shot (pun intended). Anyway, FWIW, here's my log page on backriveting: http://www.rv8alog.com/empennage/rudder/r3.htm

Mike,

If you're worried about hole size after rivet removal, don't forget there are 'oops' rivets available which may help. These have a larger diameter shank, but same size c'sunk head, and may help get a better set.

Allan

Back-Rivet Set Curved?

RVG8tor said:

I honestly think it is the rivet set, the set is wide and the head is curved which might make for a problem striking the rivet squarely.

Click to expand...

Whoa. You may have found your problem. A back-rivet set should be FLAT, not curved.

Curve in set

Mel said:

Whoa. You may have found your problem. A back-rivet set should be FLAT, not curved.

Click to expand...

Thanks Mel, my set has a slight curve to it so i suspect that is the issue. I have ordered the set from Cleveland so I will try this out and post what happens. It will be a few weeks, I get my elbow operated on tomorrow so I will not be able to build for a while.

Steve,

I figured i would give Stephen an email, I will be laid up so hopefully he can come by. He can also look over my HS and tell me what he thinks.

Cheers

My set comes from the same supplier and has the same slight "curve" to it. I haven't been able to get decent results but I thought it was me so I just gave up on using it and use the flat set now when I back rivet.

The Avery set is flat and I haven't cleated a rivet yet with it (knock on wood).

I had the same problem even using the c-frame to get perfectly square. My solution was to go down a half size in rivet. I ended up with perfectly driven rivets that met all dimensional requirements for shop head height and width and not a single one went over sideways like almost all of them were doing with the called for rivet.

So my answer is that the rivet callout is too long by .5

Best of luck.

Back-riveting helper tool

I had a lot of trouble with rivets bending over while driving, too. I resolved the problem by removing the plastic ring and spring from my Cleaveland back rivet set and making a small brass guide block:





It's got flats to apply plenty of force to hold the parts together with my fingers and the block holds the gun perfectly perpendicular to the work.

If you have access to a machine shop, I highly recommend getting one made. It cured my problem.

mcencula said:

I had a lot of trouble with rivets bending over while driving, too. I resolved the problem by removing the plastic ring and spring from my Cleaveland back rivet set and making a small brass guide block:

It's got flats to apply plenty of force to hold the parts together with my fingers and the block holds the gun perfectly perpendicular to the work.

If you have access to a machine shop, I highly recommend getting one made. It cured my problem.

Click to expand...

That's pretty sweet Mike!

Super Idea

mcencula said:

I had a lot of trouble with rivets bending over while driving, too. I resolved the problem by removing the plastic ring and spring from my Cleaveland back rivet set and making a small brass guide block:

It's got flats to apply plenty of force to hold the parts together with my fingers and the block holds the gun perfectly perpendicular to the work.

If you have access to a machine shop, I highly recommend getting one made. It cured my problem.

Click to expand...

Matt,

I like your idea, I will have to see what I can come up with. Looking at your pictures, your set is flat as a pancake. Part of my problem I think has been that the set I have is slightly concave.

Does your brass setup still allow you to reach the stiffener rivet that are near the trailing edge?

Cheers

RVG8tor said:

Does your brass setup still allow you to reach the stiffener rivet that are near the trailing edge?

Click to expand...

Yes it does. You have to orient it so the short leg of the brass block is towards the trailing edge.

Just some follow up on this since I had similar problems with the rivet set from Planetools. I borrowed a Cleveland set from another builder (thanks, Jamie) and just did my aileron stiffeners with it.

Much improved. I can't say every rivet was perfect, but much easier to center,and the end of the set is FLAT, unlike the others I have.

I'm not saying there isn't some operator error involved in the problem...maybe someone more experienced wouldn't have trouble. But, to me, I think the issue was the tool.

In defense of Planetools, though, when I raised the question to them about 6 months ago they sent a replacement set to me right away. I was supposed to send the original set back but never got around to it. So, I didn't give them a proper chance to solve the problem. I'll send them another email and also send back the set(s). Those guys are top notch and have always responded instantly to any tool problems I have had.

By the way, the tool is stamped ATS 2470S.

Good luck.