Twibright Bastard, an open source skateboard

Provides

A short DIY skateboard that looks half like a streetboard and half like a slalomboard. Can turn extremely sharp curves, easy to ride in a crowded city, yet stable at moderate speed. Small to be taken into public transport easily. Easy to learn pumping. However heavier than has to be due to simple material being used.
Weight 2064g. Comparison: Indiana Big Chief slalomboard has 2110g.

Requires

Power jigsaw
Electric drill
2 Silverspace Professional 110mm trucks or Seismic 45 deg 110mm trucks (didn't test how stable this board is with Seismic), or at least ordinary 110mm slalomboard trucks (with them it will be surely stable, yet not so capable of small bends)
15mm x 150mm x 520mm birch (or stronger) plywood. Maple is supposedly the best. If stronger than birch, can be 12mm.
3.5mm (or 2-4mm), 5.5mm (or 6mm) and 9.5mm (or bigger) drill
55cm black griptape
8 inox countersink bolts M5x30
8 nuts M5 inox or zinc plated
8 nuts M5 with plastic inlay inox or zinc plated
8 toothed spring washers, inox or zinc plated. Teeth pointing inside are preferred.
8 washers M5 inox or zinc plated
8mm wrench
Allen wrench or a screwdriver according to the bolt heads
Printer
Paper scissors
Carpet cutter
Paper glue
Hand washing brush
Any wheels, preferrably 65mm ones
Bearings. With rubber shields if you can afford them. I use Bones Swiss from Skate One (former Powell-Peralta) and am happy with them.
bearing spacers. Make sure they have length compatible with the wheel - seems to be 10mm for large soft wheels and 8mm for small hard ones.
Optional: a company that makes sticky foil logos

Manufacture

Postscript / PDF / EPS / BIG png / DXF (qcad)

Print the template. Shear the two pieces out. Glue each template on each end of the board, so that the half circle creates a half circular ending of the board

Cut the board out

Predrill the holes with 3.5mm drill or similar, drill out with 5.5mm and make a countersink with the 9.5mm (check with the head)

Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Optional: Send this Encapsulated Postscript (EPS) to a company that makes sticky foil logos and put the logo on the bottom of your skateboard. Don't use the remaining formats they are incorrectly clipped because the graphics is bigger than an A4. Please note the pictures are missing a nut and a toothed spring washer on each bolt. What it's gonna look with the graphics:

What it's gonna look like without the graphics:

Assemble

Assemble so that when you stand on one edge, the wheels on that edge come together. Put washers on the bolts first. Then the plain nut and normally tighten with a wrench and a screwdriver. Then put on the toothed washer. Then the plastic inlay nut with the plastic facing away from the first nut. Turn only the plastic inlay nut until the whole bolt starts to turn. Then hold down the bolt head and tighten somewhat more than you tightened the plain nut.

Glue the griptape on. Bend on the edges and cutt off with a carpet cutter.

Usage for beginners

If you don't want to risk injury, then get a bike helmet, rollerblade knee and elbow pads and gloves with an anti-break-wrist contraption.
The trick is that the board is self-stabilizing to the sides. If you stand there like a dustbin and don't move your feet, if you start falling to the side, the deck tilts and makes a curve that keeps you up there. But that works only from some speed up (quite low for this Bastard).
So the only thing you basically have to care about is not falling forward/backward.
Easy. It's normal you feel like an idiot at the beginning. It's even normal when you feel like an idiot after long time of learning. You don't have to force yourself into learning. You want to learn how to use it, not how to break your bones. You can ride wildly later.
Using it for going to work is a painless method how to learn without losing motivation.
To accelerate, kick back on the ground while pushing your foot forward with continuous force.
To deccelerate, kick back on the ground while pushing your foot back with continuous force. No slipping necessary. Slipping wears down your shoes.

Usage for advanced

The board can be accelerated without touching the ground. It's called pumping. Wiggle your feet to make it ride in a snake like wave. Then force the board into it's path deliberately. This way you are performing mechanical work and that has to end up in accelerating the board. Do it with your knees bent, then you have more control and flexibility. For a scientific description of this angular momentum transfer mode see (1).
It's possible to brake this way too. I have seen someone, but I didn't yet manage to learn this :(
Maybe there is some more advanced method how to accelerate without touching the ground but I didn't manage to reverse engineer that one yet ;-)
The board is heavier than necessary. You may want to switch to a proprietary one made from more advanced materials if you get fed up with the weight. The trucks and wheels are great for a professionally made board so you can keep them.
If you think the shape is crap, tell me your suggestion how to improve it.

Maintenance

Especially in the beginning, the wood can creep under the pressure and the trucks can get loose. It's not dangerous, just annoying. In such case retighten the jam nuts. It should eventually stop, the wood is not infinitely compressible ;-)
If the ball bearings don't come with maintenance instructions, clean them every time the wheels don't turn loose or make sounds. Disassemble the bearings and wash in rubbing alcohol. If rubber alcohol isn't enough to dissolve the dirt, use gasoline on the metal-only parts. Prevent gasoline from coming into contact with rubber or plastic parts of the bearings! Then re-grease with Twibright Sex Cream, the open source skateboard lubricant.

Technical note - Jam nuts

Why did I choose jam nuts instead of the more common nut with plastic inlay? The later nut doesn't hold on the thread enough and turns eventually loose. You don't want to lose energy in a friction absorber created by the truck-deck interface. The inlay nut is also specified single-use only. The jam nuts seem to be reliable when tightened in the proper sequence.

Credits

Jost Fetzer provided his power jigsaw for cutting out the prototype.
Gürkan Sengün - shooting ride pictures
John Hennessy - shooting ride pictures
Peter Rohrer - shooting ride pictures

Gallery

References

(1) Die Beschleunigung beim Slalomskateboarden - diploma thesis on Swiss Federal Institute of Technology (ETH).
Junkers test video shows that helical spring washers actually aid vibration losening of threaded fasteners.
Fastener Design Manual
The Jam Nut
Basics of Design Engineering - Fastening and Joining