	The Floppy Disk  II, FD II, is probable one of the simplest, and most rugged flying machines that you will own. It is called the FD II in that the original plane was the Floppy Disk, and we have made many, many mods to the original to enhance flying qualities, and ease of building.  I do not know the origin of the original.  The plans presented here are from our version that was built looking at was thought the original.  If anyone out there has information about the original, I sure would like to here from you.
	It is referred to as a flying machine as opposed to an airplane because it really doesn't fly like an airplane.  For you scale guys, it is exactly 12 inch to the foot scale.  It relies more on the prop, than lift from the wing, or disk.  It is for this reason that we recommend a very reliable, and powerful motor.  Many have been flown with the Fox .25, and Royal .28 with excellent results.  The OS .25 FP offers marginal performance in this plane.  The Fox will give you slightly more power, and is a bit lighter than the Royal.  Whatever you choose make sure it is powerful, and reliable.  Remember to adjust the engine properly, and not too lean.   A 9x4 prop is the best for this plane; it keeps the speed down, but the thrust up.  If building the rudder, too much speed will cause damaging flutter.   Also stay away from anything bigger than about a .28 or .32.  You will not really need the power, as with the Fox it will go vertical at about 1/2 throttle.  A bigger engine will mean more weight, not only in the nose, but in the tail, to balance.
	This is NOT a beginners model.  If your are very conformable with a low wing aileron ship, you will not have any problems with this plane.  It does have some different habits that you must learn about while flying at altitude.  It sometimes takes awhile to pull out of a maneuver.  If you normally just pop open the throttle for take off, and chop for landing, you will have to learn not to do that with the FDII.  You will need to use the throttle!  It is a very important, but much forgotten, flight control with all R/C aircraft, but very much so with this plane.  Also if you have enough altitude, it will glide better than a refrigerator, but not much better.  This is the reason for the reliable engine.   Remember this plane flies more on thrust than lift.  Use this to your advantage.  Only add the rudder if you are a very experienced flyer who uses the rudder all the time during routine flying.  Not just for snaprolling, but for correcting in cross wind landings, and the such.  It will give the FD II some nasty habits if over used.  It flies fine on three channels, but the rudder adds a great deal to the weird aerobatics, and helps while hovering in for a landing if used properly.  You can always add the rudder later.   The FD II will definitely enhance your reflexes, and flying skills.  
	With that out of the way, lets build the FD II.  The material used is 1/8 corrugated plastic like that used for signs.  To start off, carefully cut out the fuse, tail, and formers.  It is best to make a few light scores, than to cut the whole way through in one pass.  We use a #11 hobby blade for the curved parts, and a utility knife for the straight parts.  The next part is very important for a level, straight disk.  Carefully fold along the two fold lines on the fuse after you made your cut.  Cut like the hinge ( see plan), and have cut part on inside You want to fold with the cut part on the inside of the fuse.  Be careful here and refold if necessary.  It helps a bit if you run a blunt nail along the fold line first.   You want the platform where the disk sits to be level.  The reason for the difference that you may find is that the flutes, the hollow part of the plastic, are about 1/8th inch wide.  If you fold differently on both, you can be off as much as 1/4 inch.  Not good!!  Double check your work here!  Once you are happy with the folds, carefully glue the formers A, B, C.  Make sure the formers, and the fuse sides, are at 90? using a right angle of some sort, such as a right triangle.  Start at C.  We use medium zap and kicker with very good results with plastic to plastic joints.  Now cut the firewall from some 3/16" or 1/8" aircraft ply.  Do not use lite-ply.  Cut the height to suit your engine mount.  Make sure to install the blind nuts for the engine mount before preceding.  It is best to mount the engine upright to avoid damage to the muffler on the not so perfect landings.    Roughen, and clean  the plastic where you will be gluing.  Cut the bottom from 1/8" ply, and the side doublers from 1/16" ply.  We use 5 or 15 minute epoxy for all wood to plastic joints. Now glue on the firewall between the doublers.  Backup the firewall with some scrap triangle or square stock.  We use 1/8" spruce sticks.  Also add a doubler for the landing gear.  The location for the center of the gear is marked on the bottom template.  For gear we use small aluminum type, with a spreader bar for the rough landings.   It is best to attach the gear with nylon bolts so they break away on the occasional rough landing.  Keep spares in your field box.  Now drill and tap for those holes.  Be sure to fuel proof the firewall, and tank compartment.
		 We recommend a electronic mixer of some sorts.  Either in the transmitter, or using one of the small mixer modules.  We have used the DAD mixer with very good results.  This saves weight over a mechanical sliding tray mixer, and greatly simplifies the set up.  If using a sliding tray, build and install as normally done with a sliding tray.  Your balancing will also be a bit more difficult when using the sliding tray.
	The fuse is basically done.  Before proceeding mount the throttle servo behind bulkhead A.  Servo tape works fine.  Be sure to clean the plastic, but do not roughen it.  Now drill bulkhead A, and the firewall for the throttle pushrod.  With that done, place the receiver and battery in the radio area of the fuse, tape the disk to the fuse, and tape the tail on.  With the engine mounted, tape the elevon servos to the outside of the disk, one each side.  Include the rudder servo if used.  Adjust the elevon servos until the disk is balanced.  The balance point is 5.5" from the leading edge of the disk.  If using a sliding tray skip the rest of this paragraph.  Now mark the location of the servos, and make cutouts for them.  Make the cutouts about 1/16" oversize.  Make mounting plates for the servos from 1/8" ply, and glue them to the inside of the fuse ( and disk for rudder servo if used ) where the servo screws will go.
	Now is a good time to glue in a scrap piece of ply for mounting the tail wheel, and cut access holes in bulkhead B if needed for the servo wires.  It would also be a good time to cut the hatch for the receiver and batteries.  See the plans.  Do not cut all the way through the hingline.  Only cut one side of the flute, just like was done for the fold line.  When flying use good strong tape to hold the hatch shut.
 	Now for the wing/disk.  If you choose to use a rudder ( experienced pilots only ) plan for the rudder servo.  We mount ours in front of the rudder.  Make sure it will not interfere with the elevon servos.  Cut and mount the rudder servo as you did the elevons.  It is best to do this before gluing the disk to the fuse.  While working on the disk, cut out the elevons.  Make sure you only cut the underside of the flute for the hinge.  Also cut away any of the excess plastic on the cut flute.  This makes an almost indestructible hinge with no gap.  See plans.  Make sure you understand this before making the first cut.  After that, cut about 1/8" from the elevon on the side facing the disk.  This will give proper clearance so that it can move freely.  Attach control horns with the holes lined up with the hinge line.  Do not over tighten as it will crush the plastic.  You can even back up the horn, and plate with part of an EZ type hinge.  Cut out the notches in disk for the fin, and fuse tabs, if not done already.   Once you are sure all is ready, carefully glue the disk to the fuse. Have the fuse on a flat surface and start at the front.  Trim the tabs when done.  Make sure it is straight, and has no warps.  They do fly well with an amazing amount of warp, but they fly better when they are straight.
	If you are going to add a rudder, cut it out as you did for the elevons.  Make sure you include the hinge.  We made ours 16 flutes long, hinged on the 17th flute, and it stands off about 1 inch form the disk.  Glue on the fin, with or without working rudder, making sure it is square to the disk. 
	Your almost done.  Drill four small holes, two on each side. along the fuse below the tank.  This is for the pegs that hold the rubberbands for securing the tank.  We use small pieces of inner nyrod for the pegs.  Next make a cutout for the fuel tank in the leading edge of the disk.  Make sure to leave enough room for foam.  Install the tank, a six once fits great, with plenty of foam, and attach with rubberbands on the pegs.  Install the elevon, and rudder servos, routing the wires to the receiver .  The linkage should run straight to the control surface.  All the disks that we have seen use 2-56 rod with no problems.  Now on one of the elevon servos, using the opposite servo arm than for the control surface, make a connection to the tail wheel.  We used a metal clevis that has the arm with the pin cut off to connect to the push rod with an EZ connector.  A piece of brass tubing crimped, and soldered also works.  Make sure to bend the tailwheel wire to the proper side when setting up.  You may want to connect the tailwheel to the rudder, as is conventionally done, using a wire from the rudder to the tail wheel.  We do not recommend this as the rudder is very sensitive and will cause a severe roll over on take off.  Now make sure that the disk is balanced.   It should be very close if you pre-balanced the model as described above.  If not add weight where necessary.  You may want to adjust the CG later ( we fly ours slightly tail heavy ) but do so after you are conformable with the model.  Route the receiver antenna down one of the flutes in the fuse and attach to the tail.  Adjust for proper control direction.  For throw we use 1.5" for rudder, and  1.75" for elevator/aileron.  This is measured from the widest point, and moving only one control at a time.  For example elevator only, and aileron only.  If using a movable rudder, cut the elevons so they do not interfere with the rudder movement.  Do a small amount at a time until there is no interference.  Do not cut the rudder as it will detract from the performance.
	Now all that is left is to fly.  Of course you have done a range check, and proper battery check.   You may want to try a taxi test, but we prefer to just fly.  DO NOT use rudder on the ground!!!  Let me say that again, DO NOT USE RUDDER ON THE GROUND.  If you have some rudder input, and the disk leaves the ground, you stand a very high chance of snapping in.  Once airborne, try not to climb too steeply at first, gain altitude, make wide turns, and trim for straight and level flight, to get used to the different flying style of the FD II. For the first few landings you may want to fly it in like a conventional plane, but after you are used to it, it will hover in very nose high using the throttle for descent.  Also try out the rudder at altitude first.  It can be very sensitive, and get you into trouble very quickly.  Once you are comfortable with the plane, the sky is the limit.  It does some of the most unusual gyrations you will ever see.  We are constantly coming up with new maneuvers that only this plane will do.  How about an ascending flat spin? Or a flicker tumble? Or a, well you get the idea.  Play around with the sticks, and have a ball.  Remember to leave some altitude as the plane sometime takes a while to recover from some of the weird maneuvers.  You will see that using the throttle will not only enhance the flight performance, but it is required during some maneuvers, such as a pull out.  It is best to be at low throttle, and then give full throttle, and full up to pull out of this maneuver.  Also this plane is very fun to fly in the wind.  Backward flight the length of the runway is no problem with a bit of wind.  Make sure that you take off, and land directly into the wind.  Once on the ground the disk will very easily tip over.
	As with any RC model kit, we have no control over the final product.  It is up to YOU to fly in a safe manor.  Always check all of your equipment, and fly in a safe manor.  Stay away from spectators, and make your turns away from the pits.  The plane is not hard to fly, just different.  Get used to its habits before trying anything low.  Above all have fun safely. 

I would be very interested in heraing about your Floppy Disk.  E-Mail me any comments, suggestions, or questions.
 
Happy and safe flying.

Dave
Davew@telerama.com

