Foam Wing Sheeting

1.)	There are 2 basic methods of preparing foam surfaces.
	A.)	Sheet all foam pieces, top and bottom, then cut out all control surfaces; elevators,
		rudder, ailerons, etc. (I use hacksaw blade or a small fine bladed keyhole saw.) 
OR	B.)	Cut out all foam parts, then sheet.

I recommend A . I find parts stay straighter with "A" method

Note:	I like to use 3/8" to 1/2" balsa on both sides where control surfaces will be hinged; so you 
must cutoff additional foam areas to accommodate balsa thickness. Use Hobbypoxy Two or similar glue 
to attach balsa to foam. Pica white glue is another excellent product for this job.

2.)	Since I glass all my balsa-foam composite parts, I sand all my trailing edges just enough to
 	fair with fixed surfaces and they have a round radius edge of approximately 3/32"; not a
 	critical measurement. Sheeting is generally 3/32" balsa or 1/64" plywood; 1/16" balsa is 
	good on tail surfaces for lightness of construction.

3.)	I cap exposed edges of foam surfaces, like ends of ailerons, elevator and bottom of
 	rudder with 1/4" balsa and on fixed ends of stabilizer. This adds a little strength and allows
 	easier fitting of moveable surfaces; by giving you a sandable surface without fear of
 	getting into the foam.

4.)	Install wing, stabilizer, rudder and leading/trailing edges on all surfaces as appropriate.

5.)	Fit, slot and hinge all surfaces TEMPORARILY; do not glue yet. Fair moving control
 	surfaces into the tips and adjoining areas.

6.)	Horizontal stabilizer and wing - I like to join my foam wing sections together with Pica white
 	glue. From the bottom side, cut out balsa and foam to the length and width of respective
 	dihedral braces. Try not to cut through the top side of the balsa, but it is no problem if you
 	do. Use at least the front and middle dihedral braces. These braces can be used later to
 	carry the landing gear loads

Sheeting - Wing, Tail, Rudder
Normally you will find that 3/32" or 1/16" balsa is widely used; 1/64" plywood sheeting is also being
used. I like to use the balsa as it allows me to rough fit parts and sand them to fit. With the plywood,
you need to be very accurate from the start.


Attaching sheeting to foam
The foam cradles that the parts come in should be used when attaching sheeting. This will help insure
that parts will be a true match and built-in wing washout (2°-3°) will be maintained in finished part (wing).
If using balsa sheeting butt glue enough pieces so that you overlap all four sides of the parts to be covered. 
This can be attached with Hobbypoxy Two, sorgum, corebond or contact glue. I keep parts in their cradles and 
attach top surfaces first. If dihedral braces, wire tunnels, servo boxes, etc., need to be cut out, I do this now.
Then I attach bottom surfaces. Don’t forget to mark bottom sheeting before gluing as to slot, box, etc., locations.

Notes: 		1)	Consider putting a piece of wax paper in cradle to keep from sticking to cradle if
 			glue seeps out.
		2)	Weight part down in cradle if not using contact cement; as you want cradle to
			maintain parts shape.
		3)	Insure that you have cradles on level building board, door, etc.
		4)	This same technique is used on the tail surfaces.
		5)	Next attach leading/trailing edges, tips and end caps.


Wing Dihedral Braces 
When installing, make braces a tight fit to insure good bond on foam and to lessen areas for epoxy to
pool up, generate heat and melt some of the foam. Always install from bottom. My preference is to install after
sheeting, but before is okay too. We use dihedral wing braces of 1/8" aircraft plywood and tail braces from 1/16" or 3/32"
aircraft plywood. Hobbypoxy Two or Pica white glue is my choice. However, other epoxy glues are acceptable, but try to use 
those with 20 minutes of curing times or greater. This results in a stronger bond and prevents foam melt down.


A word about dihedral angle. You may take a little out if you want a faster rolling ac. I wouldn't’t add more dihedral. 
As you determine the amount of dihedral you want, sand the abutting wing ends (Root ends). If reducing dihedral, I let 
middle of dihedral brace hang below wing and sand even with wing bottom. Use Hobbypoxy Two to secure in place. 
Apply Pica or Hobbypoxy Two at the butt joint and dihedral brace area. I like to add some cotton flocking, cab’o’sil or 
micro balloons to thicken Hobbypoxy Two.


Notes:	With a foam wing that is sheeted and glassed the dihedral brace adds some strength,
	but its main purpose is to spread the landing gear load throughout the wing. Wing
	strength is derived mainly from the sheeting, balsa or plywood, and the application of
	fiberglass cloth to make a composite unit. Therefore I usually use 4 ounce cloth from
	the wing root to just beyond the landing gear area on the top and bottom of the wing. I
	then cover the entire area with Dan Parson's light fiberglass cloth. I put the finish layer
	of glass on while the 4 ounce structural glass is still wet. This technique results in
	excellent bonding of the materials. The West epoxy resin is used for the wing and tail
	finishing process.