This describes a cockpit cover. The techniques can be used for a more complete
cover. Obviously more elaborate designs are possible, but in my case, the
primary protection is for the cockpit and instruments, from moisture and
greenhouse heat.
I used a 1957 Singer of the type which uses mechanical cams for zig zag
stitches. It's clearly a domestic machine but seemed to handle the canvas as
well as a carpet machine. Perhaps a new Huskeverna may protest a bit more, but
the show stopper is the needle; not the machine.
You're on your own.
Actually you can pick from any number of suitable materials, and you may
just happen to have something already. Sunbrella is a canvas-like material
which is designed for tarps, old-style beach umbrellas, etc. On the low cost
side is a strong paint tarp, which has the density of jeans. Also, you may
find some army tent material. If you want to spend money, go to a convertable
top place and tell them you want some of the factory OEM material used by
Mercedes for making convertable tops on the SL's.
If you have cotton component, you'll want to pre-shrink it, by getting it wet and running it through the dryer.
Learn how to sew a dart:
Take it to the plane and just stretch it out. If there are antennas, just
break them off close to the roof line; that way you don't have to cut holes in
your fabric. The "towel bar" antennas are particularly problematic,
in that they are harder to break off.
Go to the aft part of the fueslage and, with the material centered, fold it at approximately the top of the window line to get the bottom of the material to line up with the bottom of the material at the widest part of the fueslage. If you do it right, you will have a more-or-less straight bottom as a result of your having folded the fabric.
While the fabric is folded, use a pen to mark the fold and the flat material. In other words, pen the fold and the place where the fold meets the material, to make it look like you got them both simultaneously with a big magic marker. When you get the fabric to the sewing machine, you will sew that fold together.
The fold is marked at the aft part of the fabric, but you also want to identify where this fold tapers to zero. This can be at the very top of the aircraft, or a little back from that point. Just decide where the fabric will lay reasonably flat without the dart. Mark that point. When you get to a working surface, you can draw a line from the fold measurement to the end of the dart, so you will get a straight line.
Now do the other side.
Now you are ready to do the windshield. My plane has panel access cowl covers in front of the windshield so I had to have a part of the cover extend over part of the cowl. This is actually easy. Just like the aft taper, make folds so that the bottom of the tarp becomes straight. Mark the fold.
Now, mark the bottom of the windshield, the top of the windshield and parts of the roof where the roof slopes down toward the windshield. You want the fold to taper from the bottom of the windshield to a part of the roof where it can lie flat. It sounds like you have several steps as the windshield changes its slope, but as a practical matter, a single taper is sufficient. This does not have to match the precise contour of the airplane; it just has to stay on the plane without flopping around.
Now take it off, duct tape the antennas back on and take the fabric to the machine. Draw straight lines to define the darts, and make a single row of stitches over the folds. The seams should attach the folds to the inside of the fabric, so the stitches go through three layers of fabric. (If all works as planned, you will add a second row of stitches later.)
Hopefully, you broke the antennas clean, but if you were too lazy and just tore the fabric, it's a good idea to run a ring of stitches around the holes to prevent later fraying. You have a choice of making the cover loose or tight around the base of the antenna, but keep it loose above the base.
Now take the piece de arte back to the plane and check its fit. If it's not totally f****d up, mark some desirable attach points which will tend to keep the fabric from bunching up in the wind. I have three pairs of attach points, including one which wraps in front of the nosegear. It may be possible to use just two of the attach points, but I want to prevent the cover from rubbing the windshield for some reason. Measure the length that you need to cover with both strap and bungee.
It is possible to use straps without bungees, but unless you have elasticity in the fabric, that will invite the cover to move in the wind. Thus, bungees or good elastic is a desirable feature.
Take it home and, add a second row of stitches so as to reinforce the seams and
prevent them from tearing the first week. Make your grommet or bungee attach
straps. Make "socks" for the antennas, leaving plenty of room for
the duct tape.
There's supposely some stuff that can be used to waterproof tents by soaking the material and then curing it in the dryer. I hadn't gotten the stuff as of yet, but I suppose it's latex based. It was near the beginning of the hunting season and so I never got the stuff. I also heard a mixture of linseed oil and something else will waterproof canvas. I'll update when I find out.
I've heard Thompson's Water Seal works, and that its use on canvas is specified on the label. It works!
Before that, I used visqueen to line the thing; so the cover can soak or not soak, but the visqueen is pretty nonporous.
It's also a good idea to spray both sides with PTFE carpet stain repellant.
Spraying the outside repels water and dirt, and spraying the inside provides a
little protection for the plexiglass and paint. Don't spray it until it's
sufficiently waterproofed, because waterproofing is less likely to stick to
stain repellant.
If you intend to use this on a certified aircraft, you need to ground test it.
Do so by finding a place below where large numbers of birds congregate and park
your plane there for a week.