This has been beaten to death here and elsewhere.
Google this newsgroup for 'scarph' or 'scarphing'.
Also search the boatbuilding section of the WoodenBoat forum HERE
There are many different ways to cut scarphs. For spar scarphs, jigs that create a ramp for a long handplane might be the easiest way.
For spars, you want at least 12:1 taper.

"Bert van den Berg" wrote in message ...
I have seen wood scarfed for wood mast construction where there is a long
joint made by overlapping two pieces of tapered wood. Can anyone tell me
how you physically create the long tapered joint? I have been thinking of
using a thicknesser with multi passes.

Regards,

Bert van den Berg