composite wing, wing spars

This may be only slightly off topic, but I'm building a foam core solid wing
for an iceboat/land yacht. I'm familiar with R/C model airplane foam core
wings, but I'm not sure how to scale that up for what I'm doing.

Here are the specs:
49 square feet
pluggable sections (one 10 foot section, and one 6 foot section)
wing is stayed at the 10 foot mark.
main foil and flap ratio is 60%/40% respectively
Something like 4' chord at the bottom, 2' chord at the top (main + flap)
sheeted with probably 3/32 ply


I'm looking for optinions, book references, and/or online links for helping
me out. Specific questions a
- how to build the main spar. I'm thinking a glass/carbon wrapped box spar
that allows plugging in the top section
- do I need more than the main spar?
- I'm looking at affordable, not the utimate in light weight.

If your interested, here is a discussion group talking about various design
aspects of solid wing sails. If your really interested, your welcome to
join the discussion group.
http://groups.msn.com/LandsailerandI...ndconstruction

Here is one construction method that works:
http://groups.msn.com/LandsailerandI...oto&PhotoID=24

Thanks in advance
Dave