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I
guess some readers might think it is a little unusual to find articles on how
to build a real aircraft on a flight simulation site, but one of the reasons
for writing this series is to show people how easy it can be, given a little
time and perseverance. Just to give some scale to this enterprise, you might
be interested to know that the majority of commercial and many freeware flight
simulation aircraft packages absorb more man hours of development than it will
take us to build our plane, and I also know several simmers who have built FS
hardware setups that make my investment in our RV-9 look pretty cheap. That
isn’t to say that I think money spent on FS software or flight controls
is wasted, far from it – my message is that today, building a plane is
a far more practical option than is commonly supposed. I will end up investing
roughly the same sum of money in a one-third share of our RV that I would spend
on an automobile, the important difference being that in twenty years time,
my RV share will at the very worst have kept pace with inflation, whereas my
current vehicle will be on a scrapheap someplace.
Yes, but… you say, I can’t afford to even learn to fly/I don’t have good enough eyesight/I was attacked by a set of cleco pliers as a kid/it’s all too difficult.
You really want to hear a serious answer to that? Everything is possible, if only you want it enough.
The thing that decided me against building a plane was a lecture I once went to at a flying club. As the evening wore on and the speaker began discussing the merits of different types of quarter-sawn timber and the challenges involved in laminating your own main spar, I realized that this was the kind of task only supermen would dare to attempt. The one bright spot was when the guy admitted in response to a question from the floor that yep, it was correct that although he had been talking about the project for five years, he hadn’t actually quite got around to starting on it yet.
As I sipped my stale beer and dozed fitfully at the back, I had no trouble imagining all the dreadful things that could go wrong with a home-built, like discovering I had used the wrong kind of glue at 10,000 feet one day; or the rudder falling off because I had forgotten to bend the ends of the split pins over; or the engine quitting because I had fitted the filters backward… or any one of a thousand other possibilities. Just to completely dispel the idea that I am the sort of person whose idea of fun is taking a gearbox to pieces to find out how it works, I have moderately serious trouble identifying gearboxes, even when they have an arrow pointing to them and a big label saying ‘the gearbox is here’ at the other end of the arrow. To put it bluntly, I know virtually nothing about engines, view hydraulics with extreme suspicion, never did metalwork at school and electricity scares the hell out of me.
But I have a history of not letting tasks daunt me and sometimes life takes the most unexpected turns.
So though that
lecture decided me that I was never going to attempt anything so stupid as a
home build on my own, it didn't stop me finding out a little more about how
it might be gone about. The conclusion I came to is that there seem to be as
many types of home built planes as there are folk to build them. At one extreme,
you have hairy chested stuff which you build out of wood using nothing more
than your own ingenuity and a set of plans. Scarey. There is no book and you
are pretty much out there on your on your own, and in my experience you only
get involved if you are about sixty, have built at least half a dozen other
planes, sailed the Atlantic in a barrel and are on the lookout for something
that is really going to stretch you this time.
Next level down is something like a Pitts, which utilizes mixed construction and is built in large enough numbers that you can always find someone to talk problems through with, even if it is only on the Internet. Len and I know a guy who has finished three, which leads me onto the observation that there is something infectious about building planes – once people have done one, it is surprising how often they get the urge to build another. Some people get carried away and start the second one before they have finished the first; I know one guy who sold the first one before he even flew it; and extreme cases can't remember the last time they went flying because they are always building. [Ed. note: doesn't this happen to flightsim designers too...always working on the latest plane or scenery but never firing up the sim other than to test the latest work?] I think this must have its roots somewhere in the fact that when you build a plane you end up making two of most things; and because the second one is always better than the first, you end up with a feeling of slight dissatisfaction about the end result. This is such a strong feature of home building that they say it is better to alternate which side you build first as each component comes along, or you could end up disliking the entire left hand side of your plane. But I digress.
Vans’ kits lie in the middle of the spectrum of homebuilts – what you buy is a collection of formed and pre-punched parts, together with a set of plans and a thick book of words – while at what passes for the easy end you have glassfiber kits which radically cut down the number of parts you need to deal with, thanks to the wonders of mouldings. What all homebuilts have in common is that they take many hundreds of hours to build; you can budget 1500 hours for the early model Vans planes like the RV-4 and even a ‘quickbuild’ RV kit that comes with the major structures virtually complete takes at least 750 and that would be the time for an experienced builder.
They say that anyone can build a kit plane and I guess it is probably true, but it is an incontrovertible fact that more get started than ever get finished. Vans recognize this in the way they sell their kits: although you can buy the whole thing at once, most people start with the empennage, which is relatively cheap and lets you learn all the techniques you will need later over, about 150 hours of building; then the wings, which are more complex and took us 450 hours; then the fuselage and ‘finishing kit’, which we estimate will take 5-600 as it involves wiring the panel and the engine installation too. After that, the aircraft has to be fully rigged, stripped for painting and then flight tested, which is likely to eat another hundred hours. The one thing homebuilding doesn’t give you is instant gratification and I would love to know how what Vans ratio of empennage orders to finishing kits happens to be – I would hazard a guess of about 4 to 1 – some of the excess will be builds in progress, but drop-outs must be fairly frequent. That is one of the advantages of building an RV; since the empennage only costs around $1500, so if you decide home building is not for you, you won’t have wasted that much money and you may well be able to sell it on.
You can get
some idea of the range of skills you need to build a plane by checking out Vans’
recommended list of
tools. If you don’t know what a deburring set, bucking bar, cleco
or a dimple die are and aspire to building a plane, then I suggest that you
go visit your local EAA chapter in the US,
PFA Strut in the UK, or the equivalent
in your own country. These organizations are there for the express purpose of
helping and they all run courses that teach the basic skills. In this piece
I am going to go through how we built the wings for our RV, so you can get an
idea of the type of processes involved.
The wing kit arrived in a long wooden box, all the way from Oregon, and I can tell you we were pretty excited when we unpacked it one evening late last summer. Len sat down with the parts list and I sorted through the components, identifying each one as he checked it off. There were the inevitable couple of mislabeled bags to eliminate, leaving us with a long list of non-existent parts. I have heard of builders faxing Vans and demanding to know where these ‘phantom parts’ are, but the answer is that you have to make ‘em yourself, out of various channel sections and flat plates which are provided with the kit. The rule is not to throw away anything, no matter how useless it might appear, because it might be the piece of metal from which a particularly crucial part has to be formed. Phantom part construction is the fence at which many wannabee builders fall, but it isn’t difficult if you have basic metalwork skills – if you need to learn, night school is the place, there are plenty of courses around that will teach you everything you need to know in a few weeks.
After checking all the components in and making and labeling all the phantom parts, the next thing we did was read the instructions again, consult the plans and make a start clecoing the main spar and ribs together. Understanding technical drawings is quite an art, because for one thing, they usually only show one side of the plane – taking the RV-9 as an example, all the drawings show left wing assemblies, and you have to reverse everything in your mind when you tackle the right hand side. Believe me, this sounds much easier than it is in practice; the wings are probably the most complicated bit of the plane and there are numerous little sub-assemblies, most of which are handed and have asymmetric tooling. So a dry run is pretty much essential, because it is the only way you have of finding out if you have all the parts in the right orientation; not only is drilling out rivets a really, really tedious occupation, but the price of a slip with the drill might well be the loss of several days’ work if you have to begin over. Worst case it will mean a fax to Vans asking for a new panel.
I mentioned clecos
– if you build a plane you will come to love these little critters. A
cleco is a spring loaded clip that operates with a special set of pliers and
can be used to temporarily hold together two surfaces that you are going to
rivet later. At one stage the wings had hundreds of clecos sticking out of them,
making them look like bizarre metal porcupines (second shot from the top), but
there is no better way of holding the structure together during the prep work.
And there is quite a lot of prepping in an RV wing, because even after the phantom
parts are made, all the rib flanges have to be bent into line and deburred,
as do the skins and many other components. The pic here shows Len doing some
fine adjustments to one of the ailerons - all those silver things sticking out
of the assembly are clecos and the special pliers are lying in the foreground.
Once we were happy with each assembly, the next step was to drill each hole out to the correct size and deburr it. The drilling has to be done because although most of the holes in an RV-9 kit skins are pre-punched, they are intentionally made too small, so that they can be drilled to an exact fit against their neighboring components. Deburring is one of those boring, but essential parts of metal working – when a part is stamped out by the factory, the cutter leaves a rough edge on one surface. This roughness is so slight you can barely feel it, but it is a prime breeding ground for cracks, which develop ever so slowly and sometimes only become visible years later, at which point major remedial work - like taking the whole plane apart - is the only way to fix them. So once each piece is drilled, it has to be smoothed with a deburring tool and then you get to dimple it. Dimpling is necessary on an RV, because the skins are flush riveted and you can’t have flush rivets without some kind of dimple for them to sit in. Dimpling tools have specially shaped heads, one for each size of rivet and depending on the shape of the part, you either do it using a fixed tool on a bench, or a handheld one that fits in a big pair of crimpers. Bench dimpling is as noisy as hell and handheld dimpling gives you pecs like Arnold Schwarzenegger, but there is no way of avoiding it.
Once you have drilled and deburred – about 40% of the work in a wing is doing this mundane, but highly necessary stuff – the whole thing has to come to pieces in order to be sprayed with a corrosion proofing etch primer. Fortunately, Len’s business has a full paint shop, so we didn’t have to do any of this ourselves. Then, guess what? You get to cleco the whole lot together again (you become bored with this, but keep yourself going by imagining what a 2000 foot per minute rate of climb feels like) and then, and only then, can you start riveting.
Rivets make
me think fondly of clecos. At least clecos can be taken out easily – once
a rivet is in, it is in, and there are tens of thousands of them in an RV, at
least half of which are seriously awkward to place, which means that no matter
how good you are, you will get to drill at least a few out. Riveting is a minor
art form and there are endless ways of doing it: you can use an air driven rivet
gun and buck them; you can back rivet; you can squeeze ‘em; you can blind
rivet; and then there is downhill, slalom and freestyle riveting. Bucking a
gun driven rivet is the easiest way of doing it once you learn the skill, but
let your attention wander for a second and the result is a ‘smile’
in your beautiful skin. So you have to concentrate.
With the exception of squeezing, shown in the pic here, or pop-riveting, every rivet has to be driven in against a steel bar known as a bucking bar. These come in all shapes and sizes and every home builder has their favorite. You get square ones, rectangular ones, round ones, bars with extensions, bars with beaks, bars which taper at one end - you name it, if you can make steel that shape, someone has built a bucking bar that way. The reason for this huge variety is that airplanes have curved surfaces and half the time you are trying to buck a rivet which comes through in a place where there is no room to get the bar in.
This raises the interesting question of how people build these planes on their own, because we know they exist. The reason for my interest is that there are three of us and we are frequently all occupied with a single job; one holding the part, one operating the rivet gun and one bucking the rivet. I have come to the conclusion that the guys who solo build either have arms like Orangutangs, are married to female bodybuilders, or aren't telling us the whole truth. Maybe they know something we don't, but I wouldn't like to build a kit without knowing I could call on someone else's help on a frequent basis and at five minutes' notice.
If you are wondering what the blue stuff is, it is a type of protective plasticized ink which is sprayed onto Duralinimium when the sheets are cut. We have peeled it off where the rivet lines are, but it will all have to be removed before the final spray job is done. In the picture above, you are looking at a tank being built. No-one has yet come up with a really good way of building aircraft fuel tanks: many planes use rubber bags, which work far better than they should to my way of thinking, but can get ridged and trap water inside; others use metal internal tanks, which are heavy, and more suited to large hulls; Vans uses the wet wing principle, where the fuel is held within the wing structure, which means you had better seal it but good.
While we are talking tanks, I'll add something which all aviators discover on their first flying lesson, which is that fuel gauges in light planes can only be relied upon to give an accurate reading when they say empty. We have gone into endless trouble to make sure ours do not fall victim to this trend, but if we succeed, it will only be the second plane I have flown which has accurate fuel gauges - the other was a 177RG and I still can't quite believe the gauges really worked. Maybe they weren't made by Cessna.
Which leads me
onto Thiocol, aka Black Death, aka other names which I will not repeat here,
save to say that if you ever get any of it on your hands, they will come to
you unbidden, because this stuff sticks like glue, only better. A friend of
ours sealed his tanks with it last October and he still has traces of it about
his person. You mix up two components to produce an extremely tacky black paste
and then Vans suggest you squeeze it out the cut off corner of a plastic bag.
We thought about this, looked at our friend, who followed Vans' advice to the letter, and decided not to do that in case we ended up looking like he did. Instead we acquired some special syringes and put it on that way. In the shot here, you are looking at the outboard end of the right tank and we are running a line of Black Death just prior to putting the back plate on - if you look at the shot above, the back is on and we are squeezing the rivets that hold it in place. This qualifies as one of the most critical tasks in the entire project, because if those tanks fail to seal, it is virtually impossible to do anything about it once the back plate is riveted and you end up having to make a new set. At a guess, that would involve the loss of about 100 man hours of work, not to mention the expense. I notice Vans now offer and option to buy the kit with the tanks already done and I am sure it will be popular.
As you might imagine, testing the tanks definitely had our full attention. We did this by putting balloons over the feeds, having blown slight positive pressure into the tank (I heard one guy did this using his compressor and he literally blew the tank apart) and then painting soapy water over all the joints - very fortunately there were no leaks.
I haven't mentioned the ailerons and flaps. These things take a couple of full days to build, each; the crucial part being that the trailing edges must be perfectly flat, or you end up with all kinds of problems flying the plane. Neither must you allow a warp to be built into any of the control surfaces, which is hellish easy to do and means using sandbags to weight everything down onto an absolutely flat worksurface - we built one specially - and you have to start riveting from the center of each structure and chase out, as you can see we are doing in the fifth shot down. I bet you never realised that building planes was so complicated and no, neither did I.
Then, just when
you think you are done, you realise that the wing tips need to be fitted. Should
be easy enough, you tell yourself, these are just fiberglass mouldings.
Wrong.
The wing tips need stiffeners built into them because they take a lot of load during flight maneuvering but the major difficulty with these components is that if you ever want to get them off after putting them on, you have to rivet in plate nuts all the way around the flange on the inside edge of the unit. You might ask why you would want to take a tip off, but all planes need regular corrosion checks and there is nothing worse than realising it is going to take a hacksaw to gain access, hence the platenuts.
Even if you have never built a plane, you will know about platenuts, because most aircraft cowlings would fall off if platenuts disappeared. Platenuts provide the grip for the screws that keep the cowlings on planes, unless you have the turnbuckle kind of fastening and even then, they use a modified platenut. Trouble is that fitting platenuts means riveting and glass takes to rivets like fish do to parachuting. I do not know how, but we managed to get all fifty (sixty?) of the varmints in place without screwing up the gel too much and some kind hand of fate put them all in the right place so that the screw holes in the ends of the wings match up. Well, almost all. We have one recidivist, but we are working on it.
In the pic is a nearly finished tip, complete with strobes, which I utterly refuse to fly without, since they are the best way of getting noticed by pop-up military traffic I am aware of - and with the nav light in place. Theoretically, homebuilts in the UK are day VFR only, though this may well change and we don't plan to have to go back and change anything. We nearly fitted the nav lights the wrong way round, as a result of drinking too much of that Spitfire beer one afternoon, which could have been kind of embarassing, though the Dude would not have noticed; most probably he would have assumed the plane was upside down.
And then, we realised that we were that close to finishing the wings. Funny thing, you labor away for hundreds of hours - six hundred so far - and then suddenly, you turn the page and it says 'fuselage' and you think, wow, one last push and we are done, guys!
So it was all
hands to the pumps and we really burned the midnight oil and there is the result.
All we have to do is bolt them onto the fuselage we haven't built yet, rig them,
connect the electrics, the control surfaces, the aerials, the pitot and the
fuel lines and we have a plane, except we haven't begun the fuselage yet and
haven't even paid for the engine, though if the exchange rate keeps going the
way it is, Lycoming may end up giving us one.
Has it been interesting? Yeah, I would definitely say so. Top of my list has been watching Len, who is a proper, hands-on engineer, solve problems that baffle Nick and me.
How on earth do we do this? We ask.
Len looks patient. With this tool, he says, holding up a thing we have never seen before. He only appears to have three tool boxes, but everything you need to build anything seems to be inside them and the rest of what we need is in his head (every now and then, when Len isn't there, I look at the boxes, just in case they have false bottoms or something, but they really are as small as I think they are).
He shows us how to use the tool. Usually, this means he does the job first time round, while we watch, spellbound. Afterwards, at work, I tell people about how exciting this learning process is and they look at me patiently, too; but then I guess it is a good job that we all aren't interested in building planes or the skies would be full.
How do you build the plane without a Len? That would be a good question, were it not for organisations like the EAA and the PFA and the people who make up their membership. If you are stuck, there is always somebody who will give you advice and there is lots of help available on the 'net. Just about the first thing every RV builder seems to do is start their own website, with a page for everyone in the family, including the dog (just in case you are thinking what I think you are thinking, we don't have a website; the dog insisted on his privacy). The Vans site has an entire page of such links, which is worth a visit, if only to see what people get up to in their spare time. Other kit plane build sites are much the same - and there are thousands of folk beavering away in their garages at this very moment, doing precisely what we are doing.
Which is dreaming of wings.
Andrew Herd