Old School Model Works: Raven ducted fan jet

[Michael]

I lightly sanded the outside skin, and then added a few drops of CA glue to the inside seams to strengthen the sheeting-joints. I quickly spread out the CA glue along the entire seam/joint before it dried.

[Michael]

Next I CA-glued the front edge of the upper sheeting to the leading edge, leaning on the front ribs tops.

Once the glue was thoroughly dry/set, I sprayed and wiped-smooth the Windex along the outside front upper sheeting. Within a minute, the sheeting started wrapping itself along the upper rib curves.

[Michael]

My next step was not planned; it just made sense, so I went with it.

The balsa sheeting easily fit the upper rib contours, so, holding the wing vertically, bottom (un-sheeted) facing me, I simply added CA glue to all places where the sheeting came into contact with the upper wing sheeting. I held the wing carefully to make sure it wouldn't warp when being glued.

One problem I encountered was that the sheeting wouldn't come into contact with some areas of the trailing edge, because the ends of the rib tops and the trailing-edge-doublers (hinging areas) were a bit higher than the trailing edge. I was able to squeeze most of these areas and glue with CA, but the gap at most inboard section was too thick, so I added in a small length of scrap 1/32-inch balsa sheet. It fit in perfectly.

[Michael]

Although the edges haven't been trimmed yet, the upper wing looks great!

The upper wing sheeting took only a few minutes. It may be challenging to work so quickly for some. Some builders may want to proceed more cautiously, and follow the instructions with slower-drying wood glue.

[davidk]

I had trouble visualizing the top sheeting instructions... they didn't quite make sense to me.  The top sheeting is made up of 2 balsa sheets, eventually glued along the long edge.  Taking just 1 sheet, the leading edge sheet, you're supposed to:

Soak the outer side of the wood to expand the fibers.  Now hold it to the curvature needed.  Place this sheet you just formed up against the leading edge of the wing."

Yeah... right.  Then you're supposed to glue the 2 sheets together.

Instead, like Michael, I glued the 2 sheets together using Michael's tip on using a more pliable sheet for the leading edge... now I have 1 big flat sheet.  Michael was able to figure out where to cut this balsa sheet for the trailing edge but I just couldn't see how to do that, even though he explained it to me.  Instead, I wanted to form the sheet and then turn the wing over to see where to cut.

Michael is brave enough and has the talent to start by gluing the leading edge... I couldn't do that.  I taped the leading sheet to the leading edge.  I started using painter's tape but then I remembered Mark's advice and used electrical tape.  Painter's tape will let go once Windex is spraying.

I started spraying and like magic the balsa started bending... all by itself!  I draped and shaped it over the ribs, loaded it up with weight, and went over it lightly with a heat gun.  I let it dry for the night.  Now that the sheet is in the right shape, I turned over the wing and marked where to cut.

[davidk]

Having done one wing top sheet, I tried Michael's method on the 2nd wing of securing the leading edge, soaking, and then gluing with CA as the sheet was bending with the ribs.  This worked out well.  I couldn't have done that on the first wing, but knowing how the wood responds and how things feel, it was great for the 2nd wing.

[Michael]

Both wings-tops sheeted and trimmed.

[Michael]

Bottom sheeting is completed, similar to the top. I used yellowish wood glue thinned with a bit of water, brushed onto the structure where it would contact the sheeting. Windex soaked into the outer sheeting helped bend the sheeting to the bottom. I used a bunch of batteries to hold the sheet down as it dried. This took several hours.

I cut and glued on the trailing edges as per the instructions. The aileron (not glued on) will be shaped later.

I used the template provided (last sheet of the instructions) to cut an under-size square for the aileron servo area. I carefully enlarged it to meet the inside edges of the back of the spar and the front of the servo bay rear frame, and the outside edges of the hardwood strips (matching the inside of the ribs). The servo covers fit well (not glued).

[davidk]

Flying was great today.  There were a few drops of rain for 10 minutes and then cleared.  I brought a Raven wing and Michael and I talked about the HS parts, the 3 doublers that go between some of the ribs.  On the top side these are not an issue as only a little bit sticks up above the ribs and is easily shaved and sanded away.  The Top side process is Step 22.

The Bottom side, Step 32, presents more of an issue.  The Bottom side tabs on the Ribs are to be removed.  This doesn't leave very much of the Rib at the trailing edge.  Most of the doublers would need to be shaved away.  Instead, I used scrap 1/16" balsa.  Now, very little needs to be removed.

I also put a doubler between every rib.  On the Top side, the sheeting in the sections without doublers could be depressed.  So, not only did I put a doubler between every rib on the Bottom side, I also cut and sanded a wedge shape piece of 1/16" to fill the gaps on the top side.  I pushed these into the space from behind the trailing edge and only pushed them so far as they touched the trailing edge.  Pushing them farther into the trailing edge would bow the sheeting.  I only want to support it.

[Michael]

I skipped step 39. The wing tips are optional, and I may decide to redesign later, to a shape I like better. Also, the wing will be easier to cover if the wingtips are not installed first.

Step 44 indicates that there will be a 1/4" gap at the bottom of the FS7's and FS9's when glued together. The plywood and balsa pieces must be glued together, even at the top, front and rear edges (remember to build a right side and a left side.) There is a 1/8" gap on the bottom edges of mine; not a 1/4" gap as indicated in the instructions. I believe the 1/8" gap is correct; the center-section builds properly as such.

Be careful and aware of what is top and bottom.

[Michael]

I assembled the wing-center-box as per instructions, steps 45 to 49.

In step 50 (and step 49), when gluing plywood to plywood, with epoxy, I scored (scratched or cut) the surfaces, so that the epoxy would have more to sink into and hold.

I sanded the landing gear section (bottom part LG2) flush with the 1/4" strips. See my photo 35.

I used elastics to hold the bottom plywood LG1 while drying. I used epoxy.

[Michael]

I glued together the dihedral braces as per the instructions. They fit into the wing center section without any sanding. I did need to sand the braces to fit into the wing slots.

I did not glue the braces, center-section and wings together at this point. It will be easier to cover them first.

Essentially, I'm building a kit into an ARF, which will be assembled later.

I did not find aileron-shaping or hinging instructions in the manual. I will do this next.

(I want to finish the wing construction soon, as I want to put some effort into another model of mine, due the consequences of a bad landing.)

[Michael]

Shaping and hinging deflection surfaces. This next bit of work is not covered in the instruction manual. I'm sharing this for anyone who hasn't done this before. Note: Nothing is glued here. Gluing in the hinges will take place after the model is covered.

I sanded the ends of each aileron, to make sure there was enough clearance for easy movement, especially for after the model is covered. 42.

I drew a center line along the rear wing edges, and the front aileron edges, and then marked off where I would put hinges. 43.

Then I drew/dug deeper indentations where the hinge cutter would cut. This was to make sure the hinging-cutter didn't slip and cut in the wrong place. 44.

I used a razor-plane to shape a V-edge on the aileron front edges, carefully so as not to cut into the hinging line. The rear-wings (where the ailerons will be attached) remain flat/square. 45, 46, 47.

Hinge-pockets are cut. 48, 49.

Pins are put near the center of the hinges to make sure they don't go in too far on one side, more than the other. The hinges are inserted, and the ailerons are fitted onto the wings. Nothing is glued yet. 50, 51, 52.

I repeated the process for the tail surfaces. Nothing is glued yet. 53, 54.

Before proceeding with the fuselage, the wings and tail surfaces will be sanded. The rear elevators/rudders will be left square; they do not need to be tapered to be sufficiently aerodynamic.

[Michael]

Fuselage started; steps 56 to 63.

I simply followed the instructions carefully. Photo 55.

Photo 56: Make sure the plywood lines up with the balsa, the ends of the tabs flush with the balsa; not overlapping.

Photo 57: I drew a line on the inside fuselage where the front side of Former F6 will be glued, as a guide for the 1/4" balsa strip.

Photo 58: There wasn't enough 1/4" square balsa in my kit; I used some scrap that I had from before.

[Michael]

Fuselage is going together just as per instructions, so far, up to step 68. The lower corners of former 7 are not cut enough to fit over the 1/4" balsa strip. I just cut it to fit. The other formers fit accurately.