Fournier RF-4 (oz16576)

About this Plan

Fournier RF-4. Radio control scale model powered glider. For electric. Wingspan 60 in.

Quote: "Full size free plan feature. Fournier RF-4. A 60 inch span sport scale model for electric power and four-channel control, designed by Peter Rake, with the prototype built and flown by Enzo Della Mea.

Now, before you start, I realise that modern, power gliders are simply not the type of model I'm known for. However, when an old friend mentioned that he rather fancied one, I volunteered to draw up some plans. Then, of course, I needed to find another willing volunteer to build and fly the model. As it so happened, whilst this style of model may not appeal to me, it most certainly did appeal to Italian modeller Enzo. Armed with an electronic copy of the plans, and cut parts sheet, Enzo proceeded to produce the model we see here. He claims to be something of a novice builder, but it looks nice enough to me - very pretty, in fact. Since English isn't Enzo's first language, he didn't feel able to write up the build himself, so for a change you'll just have to put up with me telling you what to do!

Tail surfaces: Since we have to start somewhere, we may as well do so with something nice and simple. Things don't get much simpler than those tail surfaces, Cut the parts from medium-to-firm grade balsa, join as required and sand overall, rounding off the edges. The trailing edge of fin and tailplane do not get rounded, to make for neater hinging. Whilst the plan shows parts for centre hinging using Mylar hinges, it is equally acceptable to top hinge with film.

You'll notice that no 'anti warp' keys are used. You could, of course, make the tips from wood with the grain running chord-wise, but I would not recommend inserting panels of cross-grain sheet as keys. I know all the old plans used to show this, but I could never get it to work as intended. In fact, as far as I could see, they actually caused more warps than they cured.

Wings: Right, you've had all the rest you're going to get! Now we move on to building the wings which are more complicated and require more by way of explanation.

The first thing we need to do is to join the spar parts, to make up a continuous one-piece spar with the dihedral angles built into it. Then there's a decision to be made. As you'll notice, the plan shows torque rod operated ailerons, but the photos show that Enzo used wing-mounted servos for his model. The choice is yours, torque rods result in a cleaner appearance, but there is less risk of slop with wing-mounted servos and short pushrods. The reason you need to decide which method you will adopt now, rather than later, is because it affects what holes you need to make in the wing ribs - those shown for torque rods, or omit them and make larger holes for the servo leads to run through.

So, once you've made up your mind, it's time to start pinning stuff over the plan and actually gluing things together. Begin by tapering the trailing edge off, and pinning down the lower centre section sheet (there is no servo cut out in this) and accurately glue the spar to it. Glue in place the ribs, noting that, at this point, the section in front of the spar should not be glued. Because of the wing section, the lower leading edge sheet, on both centre section and wing panels, will need to be glued to the ribs/leading edge after the panel is removed from the board. True, it could be packed up, but I find it easier and more accurate to do it as suggested above. Note the way in which ribs R1 and R2 are laminated to form the wing dowel position. (Do not glue in place the hardwood undercarriage blocks until you have the lower sheet pulled into place and can shape them to conform accurately to the curve. At that point, epoxy them securely to the sheet and the spar.) Glue in place the leading edge and allow the assembly to dry thoroughly..."

Fournier from Flying Scale Models August 2010.

Direct submission to Outerzone.

Note see also prototype Fournier RF-4 build thread by tacchino on RCGroups at: https://www.rcgroups.com/forums/showthread.php?1065705

Supplementary file notes

Article pages, thanks to RFJ.

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