Construction Notes

by Frank Justice

This sequence of instructions is set up to minimize the amount of time spent in setups and task changing; reduce the chance of mistakes, and produce good alignment and neat-looking work. Sometimes the reason is given, sometimes not. The steps should in most cases be followed in exact order; in particular, do not do any task, especially riveting, before it is called for. The order of steps within a task is designed to make each step as easy as possible such as by doing any operation on the smallest possible piece or while it is most accessible.

The order of major steps is designed to get each subassembly as complete as possible so that once the fuselage is done there will be very little work left in the final assembly. This is sort of a psychological thing in that you don't want to be looking at another 1000 hours of work when it already looks like an airplane.

I would appreciate any information from users as to errors or easier ways to do things. Also, I am particularly interested in hearing about mistakes made so I can add warnings to the instructions.
Deviations from the plans
There are a lot of ways in which you can deviate slightly from Van's plans, whether it is to eliminate pop rivets, make the appearance more show-like, make the structure stronger, adapt to tools you have or don't have, or allow easier assembly. These instructions follow the plans as much as possible simply to avoid confusion. I have heard numerous tips from builders about deviations, many of which do not appear to have any significant value, and these are usually not included here. These instructions do try to eliminate those pop rivets which are easy to eliminate, since that seems to be the thing that most builders are interested in.

At the moment these instructions start with the elevators; I intend at some point to go back and write ones for the rudder and stabilizers, but these parts are well enough documented already that there are only a few problems people have with them. I also want to document the use of the jigs I made for doing the stabilizer skeletons. It is assumed that the horizontal stabilizer is skinned but the tips are not put on at the time the elevators are started.
Hints gathered from various builders and other sources

Countersinking and Dimpling
If you plan to dimple a skin, use a #41 drill bit for all its rivet holes so they will still be reasonably tight afterwards. (Dimpling enlarges the hole) If you plan to countersink, you may want to use a #40 drill instead if your countersink bit tip does not go easily into #41 holes. Also, if you plan to countersink, use a Scotchbrite wheel or fine sandpaper to deburr the back side or else be very light-handed with a deburring bit. Normal deburring with a rotary bit bevels the material and an oversized hole will result in thin material after countersinking.. Never countersink without another piece of material behind unless the piece is much thicker than the countersink depth; otherwise when the cutter goes all the way down it will start to enlarge the hole sideways. The backing material must be firmly held to the item being countersunk. If the countersink starts to squeal, stop immediately; it is probably enlarging the hole. Make sure the countersink is exactly perpendicular to the hole, and look at the hole afterwards to make sure the ring is even. Hold the foot of the microstop to keep it from rotating and marring the skin. Use light pressure on the drill so you won't distort the surface of thin material and wind up with the wrong depth, and don't stop too soon. Purchase a good quality microstop countersink tool. Some of the cheaper ones may allow the cutter to wobble excessively or will not hold it exactly perpendicular to the work. Make a countersink gauge by gluing a rivet to a match stick or similar and use it liberally. Do not countersink too deep; you should just be able to see a ring of cut metal around the head of the rivet and the head surface should be just barely above the skin surface. Go too deep and the head of the rivet will not be tight against the skin after driving, and the rivet is more likely to tilt and fold over during driving. If the countersink is a little too shallow the top of the head can be shaved down with a rivet shaving tool or a Dremel sanding disk but this is not something you will feel like doing a lot of.

There is considerable discussion among builders as to whether countersinking or dimpling is appropriate to use at any one point. In general, countersinking can produce a smoother surface if done right, and the RV designs are conservative enough that the any loss of strength is not significant even with 0.032" skins. On the other hand dimpling can produce a surface that is just as good but it must be done very carefully with a lot of pressure on skins that are 0.032" or thicker. Some builders partially dimple and then put a slight countersink in the hole; this requires a lot of extra work and will still result in a slight depression around the rivet unless the dimpling operation was done almost perfectly. As for strength, the head on a 3/32" rivet is just about 0.032" high. If the forces tending to pull two pieces of metal apart are tension, then it doesn't matter whether dimpling or careful countersinking is used in 0.032" or thicker material; the rivet head itself is an equal or weaker link. If the forces tend to slide the joined pieces of metal with respect to each other, dimpling will be slightly stronger.

Some flush pop-rivets have a 1/8" shaft but the heads are the size of 3/32" rivets. For these, first drill the hole #40 and dimple it. Then drill the hole out to #30.

Last but not least, do not countersink or dimple until you are ready to rivet; clecoes can hold parts in better alignment using plain holes.
Empenage and Wing Jigs
The jigs described in the construction manual are required for only a very small part of the total construction time. These plans are organized in such a way that you will do everything possible before you need these jigs. Do not put up the empenage jig until you are ready to start skinning the stabilizers and do not put up the wing jig until you are at the last stage of assembling the wing skeleton. That way you don't have the jigs taking up valuable space when you don't really need them.
Other Instructions
Whenever a hole is drilled, put a Cleco fastener in it; the exception is that in skins you can often go two or three holes per Cleco. When a step is finished, leave the clecos in unless the next step is a disassembly. The parts in Van's kits are normally cut very accurately and bent with moderate accuracy. As with any typical moderate precision sheet metal work, any dimension, bend angle, or bend line may be off enough to cause difficulty in getting proper alignment later. Things to watch for will be noted, but there may be a problem with one of your parts that was not a problem in my kit; let me know. Van sometimes has several different vendors for the same part. Measure every part against the plans before starting to work it.
Tools that I have found that are well worth the money for the time they save yet are not fully covered in most lists are listed below. They will also be useful in many non-airplane tasks.
  1. A rivet squeezer with a yoke having a three-inch throat, two flat dies and a 1/8" universal head die, 3/32", 1/8", and #8 screw dimple dies
  2. A tabletop belt/disk sander
  3. A Dremel tool or equivalent with cutoff disks and a cylindrical cutter bit
  4. A four- or six-foot long aluminum ruler
  5. A small-size 3/8" variable-speed electric drill such as Black and Decker makes; use it instead of an air drill because it works just as well, is just as easy to handle, and makes much less noise.
  6. The "Avery tool", the bench-mounted riveting and dimpling aid that you pound with a hammer. This is used seldom enough that three or four builders can share one. You can get by without one but it will cost you at least 100 hours of work. Make couple of platforms about 1 by 2 feet with carpet on top to lay work on while using the tool. They should be high enough that the work will lay lightly on the tip of a male dimple die installed in the Avery tool.
  7. A rivet-nut puller. It looks like a pop-rivet tool but has a threaded rod that it pulls instead. It is designed to set threaded inserts. These inserts serve the same purpose as plate nuts but are inserted through a single hole and squeezed into place without requiring access to the back side. In the RV there are several places where holes need to be dimpled but there is not room to use normal tools. You have to make your own dies; the dimple part is made by drilling a hole through the center of the head of the proper size screw so that you wind up with a volcano-shaped item. The female half is made by drilling and tapping a piece of steel, then countersinking it, then cutting it down to about the size of a large nut. To dimple a hole such as on the spar for the tanks or at the trailing edges of the control surfaces, put the volcano on the threaded rod of the puller, put the rod through the hole, turn the threaded die onto the rod, and squeeze. An alternative to the puller described above is is a simple device consisting of some spacers and a threaded rod that you turn into the insert and then turn a nut or capscrew with a wrench to do the upsetting.
Hole Punches:
A worthwhile tool to have when preparing the ribs is a hole punch such as the Roper-Whitney #5 Junior. A punch makes precise round holes and puts them exactly where you want them. It is especially good for match punching (using one piece as a guide to punch another) because it does not try to make the parts move with respect to each other like a drill bit does . It is also faster, less messy, and gets into tight corners better. These punch sets are available for anywhere from $22 (J. C. Whitney) and are also sold by many of the tool vendors we normally use. You do not need one to follow the directions here, but it is very good for aking the matching holes in the tip and main ribs.
Rivet Shaving:
To use a rivet shaving bit, put it in a good quality microstop tool and set it to shave only a couple thousandths of an inch at a time. Don't set the cutter down on the rivet head; set the cutter beside the rivet and slide it slowly sideways over the head. Some dimple die sets do a better job than others, and the more expensive ones that have a slightly curved surface do the best job. If you round off the sharp corners on a cheaper set and use enough force it will do an adequate job. If there is a depression around the rivet head you didn't use enough force. Don't use so much force that there is a distinct mark from the die all around the rivet. For those hard-to-reach dimples you can grind a dimple die down almost to the cone one one side.
Rivet Squeezers:
If your rivet squeezer is too heavy you will have to limit yourself to a 1" throat yoke. If the squeezer is awkward for you to handle you will find that the rivets bend over easily. Best tecnique is to hold one die against the shop head forcing it against the material. Slowly squeeze to bring the other die down to the other end of the rivet; watching to make sure that end hits in the exact center of the die. for smoothing heavy pieces for cutting where you can't get in with shears and for radiusing after cutting Cordless screwdriver, preferably one that will turn several hundred RPM. Use it with a countersink bit or deburring bit held either with a drill chuck adapter or the hex-to-threaded bit tool sold by Avery. Much faster than hand deburring.
Drill bits:
Either 135 or 118 degree bits will work about as well in aluminum. Cobalt bits don't cut any better or last any longer than standard High-Speed drill bits in aluminum; they are designed to resist the heat generated by high speed drilling in steel. Use split point bits; with reasonable care (start slow, don't push hard) they will not wander when you start to drill, so no need for a centerpunch.
rvnotes 11/6/93 Frank Justice

Go back to Hovan's Home Page

Comments or feedback, please send to