The mast is as simple as it gets. Use as clear
a 10 foot 2x4 as you can find. Taper it starting about 3 ft above the base, to
1.5" at the top. The 3.5" dimension runs athwartship (side to side) so
it's strongest side takes most of the stress. A 3/8" or 1/2" hole is
drilled in the top for the halyard. If you round it with a quarter round bit it
becomes a pretty smooth "fair lead." If you end up in conditions you
think are going to break your 2x4, get out your oars and get home!
Both my spars - the yard and the sprit are bamboo. I know most
don't have access to bamboo, so the yard can be made of closet rod if you can
find it in 10 ft lengths. You can also make it from 2x2 which is
1.5"x1/5". Round the corners to cut down on sail abrasion. The sprit
can be made of the same, but you can also taper it starting about a third in
from each end. Taper to 1" square. Find the clearest wood you can.