Monday, May 15, 2017

Scratch build RC airplane tutorial - Part 2

Scratch build RC airplane tutorial - Part 2

Time to continue.
First, sand the control surface edges to 45 degrees, both ailerons and elevators.
If you don't like sanding, you can do that with sharp hobby knife.

Do the same 45 degree bevel on wing where control surfaces hinge. Sand the leading edge of the wing to round.

Now, you need to make a groove in the wing for wing spar.
Grove can be made with dremmel rotary tool or just by cutting the V shaped groove with your hobby knife.
For wing spar  best to use is carbon tube 4-5 mm diameter. If you can't find that, you can also use balsa square rod, or purchase plastic arrow at hunting and fishing shop and cut to size.

 Mix some 5 minute epoxy glue and fill the groove with it.

And finally put the spar in the groove.

Be sure that wing is on flat surface, use some wax paper to cover it and put flat weight on the wing. I use books, but you can use anything you like.

Finally, when glue cures after 30 minutes, add transparent packing tape over wing spar.

Time to hinge control surfaces. I use tape hinges because they are cheapest solution, and hold very well. Be sure to put tape on both sides of control surfaces. In the next picture you can see how it should be done, and second picture shows final result on elevators.

Continue on assembling main fuselage. first glue those 2 longer doublers to fuselage intake sides and then glue in the fuselage sides itself.
You can use UhuPor glue or hot glue.

Prepare the hatch, glue hatch doublers from inside, but be careful not to put glue on part where hatch closes.

Continue with rest of the fuselage parts. Don't glue the bottom fuselage with hatch yet. We will need to install electronics before that. before closing

I have prepared motor mount from 3mm plywood. Mark motor holes and drill 1mm holes. Add a drop of CA on those holes. I use self tapering screws to fix the motor to motor mount.

Next is fixing the motor to the motor mount and gluing it to the fuselage with 5 min epoxy glue.
I use some scrap balsa pieces to reinforce the motor mount with fuselage.

While glue cures, prepare the servos. Be sure to center servos first and then mount servo horns.
After that, mark openings in fuselage for servos, cut them out and glue them in with hot glue.

Most boring part is (for me) connecting control surfaces to servos.
Use carbon rods, steel rods, anything you have, I use rods from old umbrella. Make Z-bends with pliers for servos, and use stoppers on horns for ailerons and elevator. This will take a lot of time, and final result is shown on following pictures.
After you finish that up, power on the servos and your radio, and center all control surfaces.

Now it's time to put that last fuselage piece with hatch on and glue it.

Only thing left is vertical stabilizer. on this model it's rather big, so I use 2 techniques for gluing it. First, I glue it with UhuPor, and second, I put some hot glue to it's sides as seen on the picture.

Finally, add packing tape to the leading edges of the wing and those wing tips, since they have tendency to break during landings in grass.

Final part is to glue U shaped intake at the front of the fuselage.
You can then sand all what you think still needs sanding, and you are ready to fly.
Full video of building this model is available here:

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