LOST FOAM AND REED CONSTRUCTION...
Lost foam and reed is a fairly new construction method...
Those of you who used to make the carved block models will understand the process of carving the foam to the shape of the fuselage.  Taking care to make sure it's 1/8 inch under the required size to allow for the reed formers that will be wrapped around the foam plug....
Pic #5
The fuselage side view and top view is cut from the plan (I prefer to use copies of the plan) and they are placed on the fuselage block.  Usually laminated from Pink or Blue insulation foam.  Most of the foam has a plastic film moisture barrior...be sure to remove this before laminating the block pieces together....don't ask me how I found this out

Once the block is ready, it pays to have a few of the blades for the breakoff blade knives from the Dollar Store or similar.  Make sure that you use a sawing motion when cutting/carving the foam block.  If you don't the foam will snag on the blade and begin to rip and chunck off and you'll have a mess... Foam really dulls blades so don't be afraid to change blades often when it starts to drag a lot...

Once the rough shape is attained finalize with 80 grit sandpaper on a block with very little pressure then 100 grit then 320 grit.  This should give you a fairly smooth surface.  

Once you have the shape then mark off all the former positions on the foam block...
Pics #1&2
You may want to mark wing root positions as well as former positions.

Now comes the addition of the reed formers. The reed was purched HERE You want the #1 reed approximately 1/16 inch diameter (1.5mm) This will be enough reed to make probably more models than you'll get to in this lifetime.  I cut the reed in length so that I'll have approximately 1 inch over lap.  I soak this in the same solution of water/amonia 50/50 over night.  This is where it gets tricky...If you're going to have balsa glued flat to a former the reed needs to be butt joined and reinforced with a short piece of reed behind the joint so you'll have a flat former to glue to.  Otherwise you can just wrap the reed and over lap the joint and glue it there.  I use Cyanoacrylate glue with kicker to glue the reed.  Cyano will attack the foam so application of the cya needs care.  I use a very small tube attached to the cya bottle that allows small amounts of glue to be applied. I then use a piece of balsa scrap dipped into some kicker and applied to the joint to harden the Cya immediately.  This keeps the Cya from running and makes a nice hard joint of the reed.  Once the reeds are wrapped around the fuselage plug and all the stringers and wingroot saddles are added the foam can be removed by soaking in laquer thinner.  The black plastic plumbing pipe 3 or 4 inches diameter works well if the fuselage will fit inside it for dunking.  Make sure there is a large opening in the structure to remove the foam through.  Nose blocks can be temporarily tacked on for shaping and then removed for the dissolving of the foam.
Pics #3&4
Feel free to ask any questions and I'll try to give you an answer or send you to additional help...
Tom