Build Post
The final version of the plans are attached (Rev 6) and include the Sketchup file, the DoubleCAD file, and both a tiled and full PDF files. Note that the tiled version is optimized for the least number of page joins so use this instead of the full version if you are printing on regular paper.
View attachment Ohka 43 Rev 6.zip
Generating the plans, cutting the pieces, and making the parts
Printed out the PDF and joined the tiled pages
Then cut out all of the pieces except the wing
The HS is reinforced with a thin piece of paint stirrer embedded in the underside
EDF holder ring - note cut out the hole and test fit the EDF before completing the piece which is a little fragile
One of the inlet ducts (for decorative purposes only)
The canopy
The NAMA duct (1 inch inlet and 1 inch either side to hold the fuse. Will add a wooden reinforcement later
Assembling the nose. All of the fuse pieces are assembled the same way. The paper where the foam is removed is where the opposite edge of the piece will be hot-glued. I tried a number of techniques for this and I think this is the best because it lets the piece fold as if there was a score cut in that position. This means that the join will fold with the same flexibility as the rest of the sections. Each of the score cuts are opened and a thin smear of gorilla glue is added (much like the hot glue reinforcement of a control surface hinge). Finally the piece is folded and hot-glued.
Assembled pieces on parade. Note that I cut "frames" for some of the fuse pieces to ensure they maintained shape while the gorilla glue dried.
Assembling the Pieces
Nose pieces hot glued together. Fitment is okay. These will also be put aside as this nose will be the hatch (I think)
Front fuse pieces glued together - these fit together pretty well.
EDF holder ring glued on and thrust tube taped on - making sure that the thrust tube is straight and parallel to the EDF
I had to notch the EDF facing side of the NAMA duct to accommodate the nose cone on this EDF
Test fit the NAMA duct and add a hole for EDF wires and the elevator servo wire. The blue marks are where the rear of the canopy will sit so the wires will be hidden by the canopy.
A notch added to the EDF holder ring to allow a wood spar reinforcement to pass by the EDF
Used the NAMA duct to position the EDF into the fuse. Then holding the fuse tightly so that the EDF does not move, remove the NAMA duct and add glue to EDF holder to secure in place
Cut a 6 inch long, 1/4 inch wide piece from a paint stirrer and glued to the top edge of the NAMA duct. Note that the EDF side needed to be trimmed to fit past the EDF.
Hot glued the NAMA duct in place into the rear fuse section
Joined the two fuse sections by gluing the NAMA duct into the front section of the fuse.
NOTE - this was a mistake I discovered later that there was a slight rotational misalignment between the front and rear fuse sections. This meant that the wing and tail feathers were not 100% parallel to each other. For future builds I suggest the order of operations be
(1) Install NAMA duct into rear fuse
(2) Add tailfeathers to the rear fuse
(3) Install wing
(4) Join the front and rear sections via the NAMA duct watching the alignment of wing and tailfeathers and add a little twist if needed.
Installed the tail cone. Note the deformed/creased foam panel. The "frame" I made to hold the shape of this piece while the gorilla glue set was too tight and I over compressed the piece to get the frame on.
"The end is in sight!"
Added tail feathers.
Time to start building the wing. Cut out the wing part. The "spar" is just a single piece of 1/2 inch wide foam - the strength will come from a wooden insert, nnerdnic style. This will help make a nice thin wing.
Flip the wing piece over and added a strip of tape along the leading edge..
Then flipped it back over and "beveled" the leading edge. I stopped using a blade to bevel these edges. Instead, I just crush the bevel in place with the blunt end of a barbecue skewer. Then I glued the foam spar in place.
Now I offer up a paint stirrer to the wing, pressing it against the spar and aligning the end with the root of the wing. This allows me to mark a trench that will accept a wooden reinforcement cut from the paint stirrer.
Score cut the outline of the wooden reinforcement and then started to pull out the foam with a BBQ skewer.
Insert the paint stirrer into the trench and mark it along its length at the height of the foam spar. Then cut this piece off (using a blade and a straight edge, repeatedly score the wood until the piece you want breaks off).
Put hot glue into the trench and along the edge of the foam spar adjacent to the trench. Insert the wood reinforcement pushing it into the trench and up against the side of the foam spar.
Create two pockets for the aileron servo and glue the servo into the upper wing surface pocket. Test fold the wing to make sure the pockets align. Also, don't forget to add your servo extension.
Add hot glue to the top of the foam and wood spars, into the lower wing surface servo pocket, and along the trailing edge of the lower wing surface. Fold it over and hold down hard across the spar and trailing edge until the glue sets. Airfoil is not brilliant, but not too bad.
Repeat for the second half of the wing. Cut two 1 inch strips of foam and insert under each wing tip to set their height when you glue the two halves together - this will set the dihedral for the wing. When the glue is set, fill in any open spaces with glue and then add a strip of extreme packing tape to the seams, top and bottom. Note that I did not cut or add a spar to join the wing halves the way nnerdnic does. For this plane, although it should be reasonably quick, I don't think it needs this additional strength.
This is the wing loosely installed into the fuse - looks like a plane! The NAMA duct is not really that conspicuous.
Finishing Touches
Installed the elevator servo by pocketing through both layers of foam (stabilized and fuse section)
Extended the motor wires and fed then through the fuse towards the front of the plane
Decided not to go with the nose hatch. I had moved the EDF unit forward about 1/2 inch in this version and there should be no problem balancing her by placing the battery towards but not actually in the nose. This is a very simple hatch - just cut it out. The gorilla glue makes the piece rigid so it holds its shape without any more reinforcement
Scaled up the canopy slightly and re-printed and re-made the part. To fit to the fuse you need to bevel all of the edges and keep doing this until you are happy with the fit. Same approach is used for the decorative ducts.
And here she is, pretty much done. Just control rods and some tidying up of the wiring.
And here she is, painted up.
DamoRC
