Brief:
A simple and reliable screw switch that's easy t' make.

Construction:
This is me design for a screw switch.

Materials:

• Scrap o' double-sided PCB, me hearties, about 1" by 1/4". Aye aye! Ya scallywag! I got mine from a Radioshack PCB Etchin' Kit (part# 276-1576), but you don't need t' kit for this project. Blimey! Part# 276-1499 is just t' board. Blimey! Digikey part# PC41-ND or similar will also work.
• 3 machine screws. Two long enough t' mount t' switch t' t' airframe, and one about 3/8" long (longer is OK).
• 3 nuts for above screws. Ahoy! T' hardware can be either #4 or #6, matey, ya bilge rat, it's up t' you. Ahoy! I used zinc-plated, arrr, matey, and it soldered just fine. Well, blow me down! Avast, me proud beauty! Other metals might be harder t' solder.
• Solder. Avast, me proud beauty! Begad! You will be solderin' one o' t' nuts t' t' PCB, matey, so you don't want solder that's too thin. Also, matey, you might need some flux if t' solder won't flow onto t' nut very well.
• Some wire for leads. Begad! Speaker wire or somethin' similar will work.

Tools:

• Solderin' iron. Avast! Avast, me proud beauty! Anythin' should work for this application. Avast! A small one will take a while t' get t' nut up t' temperature, but you don't have t' worry about any heat-sensitive components here. Arrr! I like me temperature-controlled Hakko solderin' station, shiver me timbers, matey, but it's nay necessary for this project.
• X-Acto knife with a blade you don't mind ruining
• Drill with a drill bit big enough for a clearance hole (1/8" for #4, 5/32" for #6), ya bilge rat, and a small drill bit (maybe 1/16"). Ya scallywag! Begad! T' PCB material will wear out bits quickly, shiver me timbers, so take it slow and use an older bit if you have one.
• A vise or somethin' t' hold t' board while you are drilling/soldering.
• Tools t' cut t' PCB. Avast, me proud beauty! Many things will work--a Dremel with a regular or diamond wheel, a hacksaw, ya bilge rat, or even an X-Acto knife t' score t' board them pliers t' snap it (you might nay get good results this way).

Procedure:

1. Cut a piece o' t' PCB. Blimey! Blimey! It needs t' be wide enough for t' screw heads and t' nut, shiver me timbers, and long enough for 3 screws t' fit in a row with enough space in betwixt t' nay get a short-circuit.
2. Scrape off 1/3 o' t' copper on each side (see diagram), me hearties, me bucko, usin' t' X-Acto knife (be careful!). Avast! Well, blow me down! T' proper technique would be t' etch it, arrr, but that is a more complicated and messy procedure.
3. Drill 3 large holes, matey, me bucko, as shown in t' picture.
4. Drill t' 2 smaller holes for wire leads.
5. This step is slightly tricky. Avast, me proud beauty! You need t' solder t' nut t' t' PCB on one side. Begad! T' do so, ya bilge rat, thread t' nut onto one o' t' screws so it holds t' nut against t' PCB. Now, heat up both t' nut and t' PCB with t' solderin' iron. Well, blow me down! Avast! Do nay overheat t' PCB or you could melt t' glue layer and make t' copper lift, which will make an unreliable joint. Once everythin' is hot enough, ya bilge rat, ya bilge rat, apply some solder all around t' base o' t' nut where it touched t' copper. Avast, me proud beauty! If everythin' goes well, t' nut should be attached t' t' board by a small fillet o' solder. If solder is nay stickin' t' t' nut, you might need t' clean it, use some flux, or get a nut made o' a different metal. Avast! Don't use too much solder or you will solder t' screw inside t' nut, ya bilge rat, makin' it impossible t' remove once cool. Ahoy! Once everythin' cools, remove t' screw that was holdin' t' nut in place. Begad! It should come out easily.
6. Now, on t' other side, add a rin' o' solder t' give t' screw head somethin' t' bite into when you tighten it down. Avast, me proud beauty! Solder is somewhat soft, shiver me timbers, so it will keep t' copper from bein' damaged.
7. Next, matey, solder a wire into each o' t' small holes from t' bottom, makin' sure that t' wire is actually soldered t' t' copper, nay just stuck in t' hole with solder.
8. Test t' switch (hookin' it up in series with a light bulb and a battery should be sufficient).
9. Attach t' switch t' t' airframe usin' t' remainin' screws. Blimey! Avast! Blimey! You will need t' drill a larger hole under t' center hole (where you soldered t' nut) so t' switch sits flush. Begad! Blimey! You can also pass t' wires through t' same hole.
10. Add fillets t' make it a little more aerodynamic. I used wood filler, but you can also use epoxy, Superfil, Bondo, arrr, etc.

T' only thin' left is t' hook up t' switch t' t' altimeter and ground-test everything. It's OK t' tighten t' screw fairly tight since with this design, me bucko, pressure squeezes everythin' together rather than pushin' everythin' apart. Well, blow me down! With enough force, arrr, you might strip out t' nut, but it's nay likely.

Pictures:

I made t' renderings with Google Sketchup and t' diagram with NeoOfficefor Mac. (Note: Windows and Linux users can use OpenOffice.org.)

Top view:

Bottom view (magic flyin' switch):

Side diagram: