Wat can be used as spar for coro plane?
For my SPAD I used a wooden yardstick .
A fellow member Sahil used an aluminium rectangular section
How about using 3mm plywood?
You could use 2 x 4mm coro flutes spanwise (easiest!) for the wing spar. It is really very strong and light. Check out this guy from SA at RCG who gives a good demo of this technique. http://www.rcgroups.com/forums/showthread.php?t=893170 (http://www.rcgroups.com/forums/showthread.php?t=893170) The build thread is here http://spadworld.net/forum/viewtopic...er=asc&start=0 (http://spadworld.net/forum/viewtopic...er=asc&start=0) this is a proven technique used in even wings of 8 foot span!!!
Edwin