Construction Notes
by Frank Justice
Introduction 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 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.
- 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
- A tabletop belt/disk sander
- A Dremel tool or equivalent with cutoff disks and a cylindrical
cutter bit
- A four- or six-foot long aluminum ruler
- 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.
- 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.
- 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
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