[secant0give]

Jason, you make shaping foam look so easy, I'm a bit jealous in how you can make a new plane for yourself so quickly. Nice work....

Jason, you make shaping foam look so easy, I'm a bit jealous in how you can make a new plane for yourself so quickly. Nice work....

It's not really that hard to do and your right carved foam is a very fast way to make planes. It did take me a while to work out a few basic steps tho.

The main thing to remember it keep it light!! I cant stress this enough This means don't add strength where it's not needed!! It's much better to design a model to handle flying loads than the enormous forces encountered in a crash. Never try and design models to handle a crash. That will only make it heavier than it needs to be and heavier means harder to fly. HARDER TO FLY MEANS more likely to crash! It also makes it harder/slower to build in the first place and harder/slower to repair when it crashes.

My suggested steps in a foam scratch build might be

1) Pick a plane, find a 3 view of it on the net.

2) work out how big you want the model. In this case it 1.1 meter span. That works out to be 6.5 times bigger than the scale of the 3 view when printed.

3) You could make templates for wire cutting the wing and do it your self. It's not difficult and there are lots of tutorials on the net. Or you could just give the dimensions to Colin and for a modest sum he'd cut a very nice set set of wing cores.

4) A little bit of epoxy, glass and brown paper and the foam core wings are ready to be joined and covered with Iron on film or perhaps coated with the water soluble polyurethane Steve B uses. s cut the ailerons straight out of the wing and hing with tape hinges.
Mount the servos, fit control rods/horns, wings are now pretty much ready to be glued to the fuse with epoxy. later to be painted with what ever color scheme.

5) marking out the fuse is quite easy all you need to do is find a pen and a rule. Use the the 3 view to scale dimensions and take your time. "think twice and cut once"

6) First cut or join together pieces of foam to form a rectangular block that is the overall dimensions of the fuse. Use the straightest/squarest edges to take all your sizes from. Allays scale from the same edges. ie from the nose back using the fire wall as a datum draw a straight line along the bottom of the fuse to use as your other datum. draw the same lines on you 3 view then measure everything from these and transfer them to the foam block in the new scale.

7) draw the side profile on the side of the foam block. draw the top profile on the top of the foam block.

8) cut around the side profile using a band saw or jig saw or even a hand held fret saw. You must keep these cuts square this is important and it takes a little effort but it's easy enough if you go slow and take your time.
It helps greatly if the block you start with is nice and square, in fact this is pretty much a must.
when you cut around the side profile don't cut it off completely if you leave it partly attached this way you can use it to hold the block straight when cutting the top profile. then cut through the last little bits later.

9) If the fuse is rounded break all these rounded edges up into 45 degree champhers. then champher those champhers again. you'll see from the pics how I marked these out cut them then marked them and cut them again. once you have the shape as a bunch of facets you can fair them out with a block and glass paper. Go easy so you don't tear out balls of foam it's not that hard. Let me tell you I'm no artist when it comes to carving. I mark then cut to the line I can't transfer a shape by eye. Your cutting can only be as good as your marking out. USE A RAZOR SHARP KNIFE !! get a leather strop and a straight edged boot makers knife. Keep it sharp. I stropped the knife about 5 times making the fuse alone and even more doing the floats.It's very easy with a sharp blade and imposable with a blunt one.................All the usual OH&S about sharp edges applies

10) tail feathers are flat plates cut from 6mm depron control surfaces are hinged with tape hinges. servos are cut into the foam to fit neatly and hot melt glued in. push rods are carbon with z bent wire bound to them with thread soaked in cyano.

11) Pick you motor and ESC mount them I use a piece of ply glued to the fire wall with epoxy and mount the motor to this. Mount the servos control rods landing gear wheels and everything else except the lipos and the receiver.
Landing gear/ float struts will need to be mounted to ply wood load spreading pieces epoxied to the foam fuse.

12) Glue wing to fuse or arrange other means of attachment rubber bands screws ect. If using screws spread the load using 1mm ply pieces glued to the foam.

12) work out where the C of G should be. About 27% of average wing cord back from the leading edge. Mark this place on the wing.

13) Pick a lipo pack suitable for the model, probably the lightest one that will power the motor safely Is a good choice and will probably give a good 5mins of flight time. (unless your name is Samste then double the lipo pack size, quater the flight time and fit on board cryo-cooler)

14) Sit the lipo pack on the fuse in the place that makes the assembled plane balance on the C of G. Hopefully it's under the canopy if it's too far forward then get a slightly heavier pack this will allow it to go back a little. when you get it in the right spot mark around it and carve a pocket that it will fit into. you have to do this last after every thing else is added.

15) mount the receiver under the lipo pack or behind the lipos never in front 'cause the pack will act as a hammer in a crash and mash the receiver.

16) don't try and make it perfect first time just make it straight enough to fly well. It's only going to get dinged at some stage so worry about making the next one better, just get this one in the air and flying well and find out what works.