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HELP! Vertical Stabilizer Woes

BoilermakerRV

BoilermakerRV

Well Known Member
Hey all! I've been working on my empennage for about 100 hours now. I've got the HS ~60%, the VS ~40% and the rudder ~10% complete. I'm waiting on a part to complete the HS, and working the rudder while waiting for my brother to have time off to help with hand riveting.

I have to say I'm really struggling at times with riveting. I don't know if I'm too critical or still on the leading edge of the learning curve, but I sure hope things improve and soon.

The specific problem I wanted to share with you is riveting the VS ribs to the front spar. I thought the rear spar went pretty well. I'm having a hard time getting the three AN470AD4 rivets connecting the VS-704 and VS-705 ribs to the VS front spar. I tried to get my pneumatic squeezer in there, but due to the angle that these ribs have relative to the spar I just couldn't make it work. So my brother and I spent and hour or more last night trying to set these rivets. It's been one problem after another. Sometimes they fold over a bit, other times, I've let the bucking bar slip, etc., etc. I'm just wondering how others have handled these rivets.

Below are photos of the forward and aft sides of the VS-704 to VS-702 to VS-705 rivet line. You can see the rivet at the top of the photo is starting to fold over. Any chance of saving that rivet?

It may be that the only advice you can offer is, to get a good night’s rest, drill out the bad rivets and keeping working at it. And, that would be okay. Thanks in advance!

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A couple thoughts..

That rivet looks a little too far gone from what I can tell. I think my lower rib gave me fits and I ended up with 2 additional rivets in it after drilling one out 3 or 4 times.

Do you have a bucking bar with an angled face? It looks like the bar isn't being held flat because of the flange or perhaps is bouncing upwards instead of just backwards.

Masking/painters tape on the rivet set seems to do wonders to both keep the gun on the rivet and keep from marring it. On the downside it only lasts for maybe a half dozen rivets. I just put a small piece on and depress it in with another rivet and let the ends stick to the side.
 
First thing, wrap some electrical tape or masking tape around the sharp corners of your bucking bar. This should keep the nicks down to a minimum. The other thing is as Shockwave mentioned, the bucking bar face isn't perpendicular to the rivet. That's what caused the shank to mash over like that. You might want to reduce the pressure on your rivet gun as well. If you're not absolutely dead-on with a high-pressure hit, the first thing it's going to do is fold the rivet shank over and every subsequent hit will make it worse. Lower pressure will give you more control and keep the bucking bar from chattering around as much, but it will take longer to drive the rivet. For the manufactured head in picture 2, it looks like the rivet set got bumped and turned a smile into a curb-stomp when the gun kept going. Again, I'd check pressure, and I'd use the double-offset rivet for this particular case.

What I found was that after a while, I could tell by feel how well aligned the bucking bar face was to the rivet.

Just my opinion, though.
 
I agree...I think that rivet won't get to fly with you one day. :(

If you don't already have an assortment of bucking bars, you'll need several of different shapes. Sometimes a different bar can help get square with the rivet. Also, in your photo it also looks like the rivet set may have come off of the rivet head. Your shooter is going to have to apply enough pressure with the gun to keep it from bouncing and making a "smiley".

Another alternative is to use a pull type rivet (a.k.a. pop rivet) in some of those tough to get to locations. They're just about as strong, and in this case, it won't be visible.

Hang in there...you'll get to be an old pro at this before you know it.
 
Another thing... If you have drilled out the rivets (especially multiple times), it sometimes helps to "pre-squeeze" the rivet a little before putting it in the hole. Put a rivet in a hand squeezer and squeeze it a little so that it is snug when you put it in the hole. Kinda of like making your own custom "ooops" rivet.

If you go with a pulled rivet in this area, use a CherryMax. My understanding is that CherryMax's can be used anywhere a solid rivet can be used. Regular pulled rivets should not be used in areas like this.

Keep at it. You'll be a pro soon...
 
I'll respectfully disagree with the suggestion of turning your air down. The more times you tap the rivet the more you're asking for trouble. Keep the air up and feather the trigger on the initial hit then gently apply more 'trigger'. Just like a real gun....don't jerk the trigger.

Be sure to use a double offset as another posted suggested.

Also, you can EASILY massage that top rivet to where it needs to be. I always say "don't let the rivets work you.....YOU work the rivets". Put the right bucking bar in there and apply pressure in the appropriate direction, 4 hits later it'll look great. If you concentrate (don't over do it) on putting some 'skin' (literally) between the bucking bar and the skins/ribs/whatever then you'll never blemish your parts with the bucking bar. No need to 'tape' bucking bars.

Something not mentioned, it's very possible that you and your brother are fighting against each other. I've taught a lot of folks how to rivet and this is quite common. On such a little part there is no way I'd want a 'helper'. The only time you should need help is if you can't physically do it yourself. Secure the parts on your table or use your legs (my favorite) to hold it. Then take the bucking bar in one hand and the rivet gun in the other and rivet the parts together BY YOURSELF. If you're hesitant then make up a practice piece and work on it.....BY YOURSELF. You'll soon gain confidence and WILL learn how to rivet AND buck left AND right handed....and, you'll get good at it. Added bonus is you won't be waiting around for help :). If you 'must' have a helper then have them hold the parts while YOU rivet and buck.

Good Luck!
 
Check your air pressure.

I'm with Rick in thinking your air pressure is too low. It shouldn't take too many rat-a-tat's to squeeze a short rivet like these. Also, the rivet gun does the work, so try experimenting with just how little pressure you can put on the bucking bar. Trying to muscle the riveting could explain your results.

A good trick someone showed me on drilling out rivets: Drill just deep enough into the head of the rivet that you can kind of pop the head off with a little flick of the drill bit. The rest of the rivet will usually fall out, or at least it'll be easy to finish drilling it out. This sort of technique minimizes the damage you'll do in widening the hole.
 
I agree on air pressure.

We have three airplanes being assembled in our hanger (2 RVs & 1 tube and fabric). Due to rearranging our planes around I found myself closer to the large air compressor than before and further from a secondary pressure regulator. Needing to set a few -4 (i.e. 1/8 in.) rivets I choose to hook up straight to the air compressor which is set at a fairly high pressure (about 120 psi). Man, you would think those rivets were made of soft lead. About five "baps" and they were well set. Neither the rivet gun nor the bucking bar had any time to get misaligned.

Just my experience. Normally I use a lower pressure and you really need to practice on some scrap until you are proficient.
 
Michael,

Riveting can be frustrating, even for those with lots of experience, we still screw up our share of rivets.

I don't like to play with air pressure too much. About 50 psi is good for riveting and 80 for everything else.

Try to apply an equal amount of pressure with your rivet set and bucking bar. Squeeze the trigger, then release the trigger then remove the rivet set. You are a bit "trigger happy". Perfectly normal at first. You will get the hang of it.

Drill a hundred holes in some scrap and try different techniques. It'll be time well spent, I promise.
 
That top rivet could probably be saved, or at least made reasonably close to circular, enough to be okay.

My advise? Get a tungsten bucking bar with one side angled at 15 degrees or so. You can get it in just about anywhere, the angled face is perfect for situations like this, it weighs a ton but is small enough that you can hold it with just a couple of fingers.

Work out a good, repeatable method with your partner, too...e.g., a rivet is set once and the shooter *never* sets again unless and until the bucker tells him ("real quick...set it") to drive it a little more; things like that.

Tungsten bar...best tool in the shop! :)
 
three tools to buy

two inexpensive, one of them not so much.

First tool

really tools though... a set of punches 1/8 and 3/32. They are worlds better than using an old drill bit to break the heads off of drilled rivets. As it turns out, I got most of the way through the emp kit using the ends of drill bits. I found out that I was ruining good bits by doing this and then went to using older dull bits... Even when I'm using something I already have and I'm not spending more money, I have to admit that the drill bits still don't work as well as punches do. Spend the money. The punches have nice sharp square ends and grab the rivet better. These punches also work to break flush rivet scraps that are left behind after snapping the rivet head off-- when the head doesn't come off cleanly in one piece. To do this I drive the punch at an angle towards the shank of the rivet.

Second tool

Spring actuated punch... Spend a few bucks on one of these and you'll use it a bunch. I use them to put a perfectly centered point on which to start my drill. I also use them to drive stubborn or cacked rivets into their predrilled holes in parts... it seats them well. I've also been known to use it to seat partially raised flush rivets when I know that I've not struck them solidly. Sometimes I can get them to sit flush and hit them again and other times I can use them as in my last example-- to drill it out. If your rivet head is really mashed such that its elongated and mangled. Measure to find the would be center from the undamaged side and split the difference on the width. Make sure to measure the width perpendicular to the direction of the mashing. I lastly use them to punch drilled rivets out after the heads have been snapped off.

Third tool

Tungsten bucking bar. I bought the one that's linked in the left hand side bar on this site.

One angled side one squared side. I use a small diameter inner tube scrap (from the bike store junk pile) to protect my work from dings, dents, and scratches. I guess you could use tape if you like to replace it regularly, or if you like sticky hands. You will rarely pick up any other bucking bar that you own... if ever. I second the advice about holding the bucking bar. It must be square to the rivet and you only have to steady the bar, you don't have to use ANY pressure at all. Let the gun do the work. The pressure is on the gun side. Too little and it'll hop, too much and with any angle and the rivet will ooze.

They look like this---> O)))))))). For these I cut the head off with a sharp cold chisel. The head is thin enough that they almost scrape off with a couple of blows
 
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I remember these particular rivets gave me a fair bit of trouble as well. I redid them several times...what I recall helping was to clamp the work firmly to the table to keep things from moving around. Get creative with some wood blocks and c-clamps to make it happen.

Normally when you're doing the heavier AD4 rivets there's more surrounding structure or thicker metal, and this isn't such an issue.

If you get fed up and just want to move on, Van's did tell me that pop rivets would be ok in this location.

Good luck!
 
Michael,

I had the same problem in the same places. I am still struggling with 1/8th inch rivets. But let me throw out a couple thoughts for consideration.

1) During my first attempts at using the rivet gun and set I was using a Cleaveland rivet set. It is a very nice set, but when I put a rivet head in the set and looked at it, there wasn't much of the rivet head sticking out below the end of the set. This meant that the set had to be held almost exactly 90 degrees to the surface to keep from getting smileys in the surface. I ordered a set from Avery and there was more room for error with it because the rivet didn't set quite as deeply into the rivet set.

2) Measure the tail of the rivet after inserting into the hole and make sure the rivet isn't too long. My experience has been that if the rivet is the tiniest bit too long, it will have a tendency to tip over.

3) Probably some of the guys here could save the rivet in your picture. I couldn't. I've tried, but when they start to tip like that for me, nothing I do seems to be able to bring it back. So when I get one like that, I drill it a bit, snap the top off, and usually the rest of the rivet will pop right out because it hasn't swelled enough to lock into the hole tightly. This helps to keep from enlarging the hole.

4) I think Paul is correct, it helps a lot to have your parts clamped down so they don't move around on you.

5) If you have a riveting partner so that you can use two hands, use your off hand to hold the rivet set on the rivet. It helps keep the set from moving around.
 
One of the things that I learned along the way is that you don't want the bucking bar to be pushed too tightly against the tail of the rivet...it should sort of float initially with more pressure applied as the tail sets. The bucker will learn to "feel" when the proper amount of pressure is being used based on the characteristics of the rebound.

It is impossible to teach this touch by the written word, but it is totally evident when done correctly...you can easily feel when things are right.
 
Michael, some things can be taught via the written word and some things can't. Riveting is a physical skill with many subtle physical details. Take the time to find experienced local training before you go further. Replace the damaged airframe parts. Use them for practice.
 
Hi Michael,

Sorry you're having some trouble. Yes, definitely keep your gun pressure up, so you won't work harden the rivets as you drive them....ie hit them too many times because the pressure is too low. You'll know if they're getting too hard if they take on an inverted, somewhat conical shape, instead of the nice slightly bulging shape that properly set rivets look like.

Also, clamp, clamp, clamp. If you're trying to steady your work and drive rivets at the same time, you won't get good results.

Give me a call sometime, I'm in Carmel....317-848-1345

Cheers,
Brad
 
Hi Michael,

Sorry you're having some trouble. Yes, definitely keep your gun pressure up, so you won't work harden the rivets as you drive them....ie hit them too many times because the pressure is too low. You'll know if they're getting too hard if they take on a somewhat inverted conical shape, instead of the nice slightly bulging shape that properly set rivets look like.

Also, clamp, clamp, clamp. If you're trying to steady your work and drive rivets at the same time, you won't get good results.

Give me a call sometime, I'm in Carmel....317-848-1345

Cheers,
Brad
 
Michael,

I believe the flying Scotsman hit the "rivet on the head". I spent a little more money on a Tungsten bucking bar and it has been worth every dime. I have a set of old different shaped bars but always come back to the tungsten bar. Here's their link www.buckingbar.net. They claim you can build a whole RV with just this bar and I believe them. I would also reread Rick Gray's post. Good info on practicing on scrap, and using scrap skin between your finished material.

Hang in there. It just gets better!
 
It looks like you have a lot of good advice here so far. The only thing I might add to is is to set up some practice parts to learn on and do that until you feel good about what you are doing and are proud of it. What I did was to clamp two pieces of sheet about 6"x6" together, drill a bunch of holes in them and start filling the holes with rivets.
Good luck!
 
Like learning to fly

Remember when you learned to fly and did your first several touch 'n goes with your instructor? It wasn't all that easy at first was it? There are many subtle adjustments that make a difference, but as time goes by...it becomes muscle memory with some observation in the mix. As others have stated, you will feel when things are right. You will also hear when things are right. If you get a thought just before pulling the trigger like, "this part could move"...STOP and secure it. (do a go around) Hold the bucking bar closer to the rivet side to take the play out of it staying square, too. Much more stable.

I use 60 psi for the -4, 470 rivets. About a two second burst. The advice for driving rivets into scrap is a good one. Repetition until you get the feel....just like touch 'n goes.

You'll get it !!!
 
Thanks!

Thanks to everyone for the support and advice. I've been pressing on, using some scrap for practice and taking much more of the advice here to heart. I've just assembled the rudder, and will start match drilling tomorrow.

I can't thank you all enough. Thanks again!

M
 
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