Dimples: Those cute little depressions around the rivet heads that occur when riveting light skins are almost impossible to avoid. They are caused by too much pressure on the rivet gun. They can be removed (if you want your airplane to look different from everybody else’s) with a few light taps on the shop head with a punch and a small hammer.
Rivet Charts: Pay attention to the rivet charts, because although you are told the kind of rivet to use, you are not told the length of rivet to use. I keep a rivet log with calculations for each step that they are needed.Pay attention to the rivet charts, because although you are told the kind of rivet to use, you are not told the length of rivet to use. I keep a rivet log with calculations for each step that they are needed.
Cutting rivets: We had some rivets that needed shortening the other day on the Glastar project and I thought maybe the method I use might be of interest to some of you. I’m not really fond of the job that rivet cutters do, especially on # 3 rivets. Of course, I probably don’t have the best cutter that money can buy but even if it’s a great cutter, cutting a lot of rivets is a slow process. My cutter leaves a jagged, uneven edge and these rivets can sometimes be a challenge to drive. I have a few scraps of 1/8 and 1/4 inch bar stock lying around that I’ve drilled a series of #40 and #30 (on the drill press, so they’re straight) holes to check my machine countersink before use on the airplane. The holes are drilled about 1/2″ apart (or a little closer) and there are several rows. I also use this piece to shorten rivets. I stick a bunch of too long rivets in the holes along with one or two rivets the correct length and then place another piece of bar stock over the factory heads. I then shorten them on the brown (med grit), Scotch brite wheel on my bench grinder. Your eye will be pretty accurate as far as lining up perpendicular to the wheel and in also judging the length of the rivet, especially since you have placed a couple of rivets in the line up for reference. You end up with polished, more “square” rivets with this method IMO and it’s much faster.
Securing the part to be riveted: Having had to drill out every rivet in my rudder at least once, probably the single most important thing I found was to be sure the rudder and HS (that’s as far as I’ve gotten so far) are fastened securely or weighted down so they cannot move. On the very first rivet I tried to drive, the rudder shifted slightly and I have a long line of smiley’s on the skin. I don’t learn very fast, so I did the same thing a couple of times before it finally sunk in. Then trying to get coordinated to hold the bucking bar ON THE RIVET until the rivet gun came to a complete stop took a while, so I also had a bunch of crooked shop heads.
Anyway, the HS went much better, only 6 rivets to drill out and replace sooooooooooo, maybe the elevator will work out OK. So far I have done all the driven rivets with hand squeezer and the rivet gun/bucking bars I received in the GlaStar tool kit from Aircraft Tool & Supply. I did find that by grinding and polishing more of the surfaces on those bucking bars, it allowed me to do much more.
Filing down mandrels on pop rivets: To avoid scratching the surrounding skin, fabricate a protective device – simply a small piece of scrap aluminum sheet, with a rivet-head-sized hole cut out. Place this over the rivet to be filed, hold it down tight, and use your power tool with impunity, since any scratches will be only on the scrap piece.
Bucking bars: But here is a tip I should pass along too for other rookies. Having never riveted before I bought one bucking bar to examine and learn to rivet with. Mine seems to be cast iron. The main attributes of a bucking bar are mass, a polished face and the ability to fit where needed. In fact the more mass the better. I wandered out to the machine shop where I work and dug through the scrap bin. I now have about 10 bucking bars of various sizes and shapes with polished faces. The most useful ones are about 4 or 5 pounds each instead of the pathetic little ones in the catalog. In fact the one I used the most is .75 x 2 x 10 inches. I could slide one end down my sleeve and slip a rubber band around my wrist, put the bar flat in the palm of my hand and slide my hand flat into the rudder and position the bar between the flanges of the spars. I also just laid the bar in the spar and held it in place sometimes too. For the wider parts of the spars I used a 1 inch thick bar. With the heavier bars the riveting is a breeze. I think I messed up 5 or 6 rivets in the rudder and had to drill them out. Those those last seven little rivets actually took me only about 30 seconds each. So my advice is to get some BIG chunks of steel of various sizes for bucking bars. They can be anything, most of mine are just cold rolled steel but some are steel chunks of various types (A2, 4130, 8620, 1065, etc) and not heat treated.
Rivet gun size: A good 2X gun with a CP type regulator is all that is required for the Glastar. period end of discussion it’s over stop flogging this etc., you do not need a 3X gun or rivet squeezer hand or otherwise. These are niceties and they are helpful but a 2X is all you need. Now, if I had to choose one gun for working on all sheet metal applications yes I would have a 3X because it will drive 3/16 rivets as well as the little ones, but we are not doing that on the Glastar. The people who are telling you to get a 3X gun are mostly professionals who have driven countless thousands of rivets and some in their sleep. You are not one of them. Flatten out the learning curve and get a 2X gun! I also recommend using the longer (7.5″) rivet sets for the universal head rivets. These make it easier to stay straight on the rivet. As for the flush rivets use a large diameter set that does not ride on the last rivet you drove and use both hands to hold the gun from slipping and have someone else buck until you are very good at it. As for as bars use the heaviest bar you can comfortably hold. I would suggest that you have a supply of small steel pieces to make your own special bars. Do I have a 3X gun? yes. A “C” squeeze? Yes. An alligator? Yes. A hand squeezer? Yes and I use them all in different situations but I could do the whole enchilada without them. Whew, I guess that was a buck twenty fives worth. The quality of the gun and regulator will have a tremendous effect on the result.
–Cal at SH
Riveting thin metal: I have just viewed two different efforts of riveting on horizontal stabilizers and elevators. One elevator was ruined by a supposedly professional shop and the other by a builder that got the HS together but it is scared forever by the riveting results. The strength factor is ok, but every round head rivet is practically flush with the top of the skin. If I can personally view two examples of this mutilation in one day, there must be a lot of GlaStars out there being mutilated around the country and the world for that matter.
If you have the final issue of the Stoddard Hamilton News, read the Tech. Article on riveting thin material. If you do not have it, read a thumb nail sketch about it here.
First, put a flow control on your air at the rivet gun. This controls pressure by adjusting flow with a knob on the unit. Set it just high enough to handle the size of rivet, weight of set and even size of gun. Riveting with full shop pressure is suicide unless you are a real professional and make no slip ups. (Or riveting heavy metal).
We shall assume the parts to be riveted are flat together. Now with the rivet in place and the guns’ set resting on the head, apply light gun pressure. Holding this pressure, press the bar against the tail of the rivet hard enough to force the rivet head away from the skin slightly. Increase the pressure with the gun and set, enough to just press the head back against the skin. Give a small burst. This will swell the rivet into the hole and start the head to form. Keeping the gun pressure constant, increase the bar pressure and finish the bucked head.
With a little practice you will find that there is no need to drive round head rivets flush with the skin.
–Orville Eliason, 5298
Riveting with rubber: My wing nose rib flanges against the were tilted up a bit. I could easily push it down with my finger but there was no way I was going to get a spring clamp in the hole in the spar and my hand at the same time while I bucket the rivet. I made a simple rubber strip that I sanded to 1-1/2 rivet diameter thick, then punched a rivet diameter hole near the edge. I placed the rivet in the hole then placed the rubber over the rivet inside the leading edge against the fib flange. I partially formed the rivet which pushes the flange flush to the spar. I then pullet the rubber out and finished the rivet forming. This rubber technique also works well on keeping formed rivet heads from falling over when the holes are slightly oversize or elongated. Note: It is best to use a metal punch to make a hole that will fit the rivet. Using a drill make a VERY small hole in rubber.
Measuring hidden formed rivet heads: How do you quickly measure those formed rivet heads in areas that you cannot see such as the wing leading edge ribs to the spar and deep inside closeout skins? Simply make an impression on the end of your finger then look at it. You can even put your little gage over the imprint. It works real slick. You can even detect deformed heads by their oval shape. I got this one from a gentleman that worked at Douglas on DC10s. Didn’t think much of it until I was having trouble getting my little gage inside the leading edge. Only problem—your finger can get sore after 20 or so rivets.
–Gus Gustavson 5581
Riveting tips: As we were riveting the skins on the left wing we were getting frustrated with how hard it was to keep the gun exactly centered and flat on the flush rivets and how much pounding some of the longer rivets were taking to develop a proper head. Remembering Orville Eliason’s expertise with metal work, I gave him a call. He repeated one very useful hint and gave me one more. Giving full credit to Orville I would like to share them with you.
Orville before has mentioned taping over the heads of rivets to hold them in place. If you haven’t tried it you should. It really works great. It speeds up the riveting process by not having to wait while each rivet is inserted, but more importantly it protects the sheet metal around the rivet and keeps the gun from sliding around while pounding those flush rivets. No more little divots in the metal near the rivet. We used 3m blue masking tape, which seems to work better than the tan stuff. It’s called Long Mask #2090 by 3m. We are now using it on all rivets. Try it, you’ll like it!
Orville’s other helpful hint had to do with those long 1/8″ rivets that you pound and pound to get a proper head. For these, just ease up on the bucking bar slightly and let it bounce a bit. This seems counter-intuitive but it really works. For those rivets that go through the skin, the spar and two cap strips this is the hot ticket. You also need plenty of pressure (80 psi for our 2X gun), but easing up on the bucking bar is the real trick.
I would like to add one more suggestion to Dave’s riveting tips and that is to use fresh rivets. By the time I got around to riveting my right wing, the original kit supplied rivets were about one year old and very difficult to squeeze or buck, especially the 1/8 in rivets. I remembered the subject of hard rivets came up several months back and one of the GS-netters responded that he had found that Aircraft Spruce supplied reasonably fresh rivets. I ordered all new 1/8in. rivets for the right wing and it definitely made the job much easier. Fresh rivets require less pounding from the air gun and squeeze more uniformly. I also stored the fresh rivets in the freezer until ready to use.
–Dave Hulse, 5646