FTFC20 Carl Goldberg Ranger 30 designed by Jon Carlsen

[TooJung2Die]

I measured the width of the firewall outline. The nose is too wide for some reason. I made a mistake somewhere in transferring the outline of the bottom sheet. No problem, it's only foam. I sliced off a 1/4" wedge on either side and glued it back together.

That's better.

Jon

 

[TooJung2Die]

Servos and Control. Control horns are cut from gift card plastic.

Servos are 3.7 gram type. I picked up some 0.040" carbon fiber rod on the last visit to the local hobby store to use as push rod. The z-bends are made with 0.032" piano wire. The wire is attached to the carbon fiber rod with heat shrink tubing. The wire can slide inside the heat shrink and when the length is perfect a drop of thin CA glue on each end of the heat shrink locks it in place. The guide tube through the fuselage is plastic tubing from a Q-tip.

I always use hot glue to mount servos because it won't find it's way inside the servo and ruin it. Hot glue is very easy to remove from recycled servos with a little squirt of alcohol. Peels right off nice and clean.

Jon

 

[TooJung2Die]

The servos and push rods are completed. The rudder has a double bevel tape hinge. I beveled the leading and trailing edges of the horizontal and vertical stabilizers to make them a bit more rounded and aerodynamic.

I discovered that foam-cure glue doesn't stick well to packing tape. I cut and peeled off a strip of tape on the horizontal stab where the vertical stab is glued for a foam to foam bond.

Jon

 

[TooJung2Die]

Top of the rear fuselage is glued in place with Foam-Cure glue.

Firewall is cut from 3/32" plywood. I copied the dimensions from the firewall position in the nose to plywood.

Firewall is glued in place with a little down thrust. I think white Gorilla glue is best for this task. The foaming action creates a wider, stronger bond to the foam.

Jon

 

[bracesport]

@TooJung2Die - I already mentioned this technique will be great for my 'KK invader' build - I imagine I will need some CF 3x1 rods or something to stiffen the main wing?

 

[TooJung2Die]

I imagine I will need some CF 3x1 rods or something to stiffen the main wing?

If you remove paper from both sides of the foam board then yes, definitely you will need additional support. The Ranger 30 wing is only 30 inches. With the balsa leading edge it is still quite flexible. If it needs additional support I'll add a length of clear tape to the top and bottom of the wing.

You are familiar with flyboa's glider wings. He builds beautiful 60" long (and longer) glider wings from foam board. He leaves just enough paper on the top and bottom for strength and needs no carbon fiber. How about copying that technique for your Keil Kraft? I can always make another wing for the Ranger using flyboa's technique if the undercamber doesn't fly well.

Great choice for the FTFC20, by the way. Even before the challenge when I saw Woodward's Invader I thought it would make a great foam board conversion.

 

[TooJung2Die]

Closer to the finish. I'm curious about how much the finished weight will be so I put it all on a scale with the 450 mAh 2S battery. This airplane is going to be closer to 100 grams than 200.

That is a ridiculously wide horizontal stabilizer. But, that's the way they designed free-flight airplanes.

Jon

 

[bracesport]

@TooJung2Die - great tips thanks - you ship is ridiculously light, well done - oh, and yes, I am very familiar with flyboa's DLG wings (I am on my second one at the moment)! these are all fabulous techniques!

 

[TooJung2Die]

yes, I am very familiar with flyboa's DLG wings

I figured that out easily by checking the threads in your sig. You and flyboa have a very similar airfoil. I wanted to see if I could build a whole airplane with naked Adams foam board, no paper. People who have been building foamys for a very long time can't imagine building with paper covered foam board. They think it's too heavy.

 

[TooJung2Die]

Landing gear. The landing gear is .040" wire sewn with dental floss and glued with CA to 1/16" plywood. Apply the CA front and back.

A slot is cut next to the front bulkhead and the plywood is inserted.

The plywood is glued to the bulkhead and slot with a generous application of Gorilla glue. It's messy but it needs to be strong.

Going old school with the wheels. 2 inch circles are drawn on 3/32" balsa.

They are rough cut outside the lines.

Glue and clamp two circles together with the grain at right angles. Use Titebond for wood to wood joining.

When the glue dries drill holes in the center and Titebond glue in a tight fitting bamboo dowel. After the glue dries these will get turned to shape in a drill press.

Jon

 

[bracesport]

- super-duper, lots of innovation!

 

[TooJung2Die]

lots of innovation!

Thanks but I can't take credit for any of these techniques. Some of them like the sewn wire and balsa wheels have been around longer than I have been alive.

Truing and shaping the wheels in a drill press. Rough shape with course grit until they are true and both wheels are the same diameter. Finish them up with fine grit. Go slowly. The balsa gets removed very fast!

Cut the dowel so there's about 1/8" on each side of the wheel. Using a drill bit slightly smaller than the axle wire, drill a hole centered in the dowel and stop halfway through. Flip over the wheel and center drill the other side halfway through. If you're careful both holes will meet in the middle. You will never drill one centered hole all the way through the dowel. A thin drill bit will follow the wood grain and wander to the side. Then using a drill bit slightly larger than the axle wire, drill all the way through the dowel. I made the first holes using a .038" drill and finished with .042". It's handy to have a complete drill index.

Total weight for both wheels: 3 grams

The receiver is mounted with Velcro and bound to the transmitter. My guess is the battery will go right behind the bulkhead the landing gear is glued to. The wing will come off to change batteries.

Another bulkhead is glued in to support the curved top of the nose. The bulkhead and sides are sanded and beveled. Card stock may be used instead of foam to cover the top deck of the fuselage nose. Whichever one looks best to you.

Jon

 

[TooJung2Die]

The electronics are in their preliminary positions.

I could not think of a satisfactory way to install a two-point wing hold-down like in the plans. A more conventional four point wing hold-down is used. Since the bare foam is so soft plastic reinforcement is glued to the bamboo skewer holes. It's terrible how easily the foam gets dented from handling.

The battery has to go further back than I anticipated. The receiver gets moved towards the tail and a battery shelf installed. With the battery all the way forward to the bulk head the CG is slightly nose heavy. The battery can be moved back more if it is too nose heavy during test flights.

I wish I had a lighter battery. The little 450 mAh 2S is going to be the single heaviest component in the airplane (32g). The little black mark at the bottom of the fuselage is the CG position indicated in the plan. We will start with the CG a little forward for test glides and maybe first powered flight.

It's getting close to the maiden flight.

Jon

 

[bracesport]

very nice indeed!

 

[TooJung2Die]

very nice indeed!

Thank you very much!

I made a deck for the nose from card stock to see what it looked like. I think the profile is too pointy so it is going to be foam.

In case you didn't notice there is no open cabin like the original. The foam is too weak to support the wing if the cockpit was open. The windshield will give it close to the same appearance. I cut the windshield template out and trimmed it a bit to fit better. I scotch taped the template to card stock. You can see the template if you look closely. Then I got a piece of transparent blue cellophane gift wrap and spray glued it to the card stock.

Cut out the windshield with scissors and remove the template from the card stock.

A little spray glue on the back of the card stock and we have a windshield. You can see the new foam deck of the nose too. The foam was rubbed over the edge of a table like the wings to get the curve.

I like to use wire insulation for wheel retainers. The insulation is tight so it stays in place but a tiny drop of CA glue guarantees it doesn't move.

I added a tail skid. It'll protect the foam and add a little more area to the vertical stabilizer.

At this point she's ready to fly. I'm pretty happy with the weight; 3.3 ounces empty. My smallest 2S battery adds another 1.1 ounces for a ready to fly AUW of 4.4 ounces or 125 grams. The battery is one quarter of the total weight! I ordered a couple of smaller 2S batteries today.

I hope she flies better than my first attempt with the Ranger 30. Version 1.0 of the foam board Ranger I made in 2015 was a tip stalling disaster. After a few revision we had a great flying little park flyer.

Jon

 

[TooJung2Die]

Woohoo! She flies. I gave it a couple of test glides on the back lawn. Yup, it was a bit nose heavy so I moved the battery backwards and gave it a bit of up elevator trim. Beautiful glide. I gave it 1/4 throttle and tossed it. It climbs! Way more thrust with a 5x4 prop than needed. After I reduced the rudder and elevator throws by 50% I was flying circles in the backyard. It responds very well to rudder and elevator.

The instructions have you add a shim under the trailing edge of the elevator for free-flight. I missed that. To compensate I added 3/32" balsa shims under the leading edge of the wing. I can now eliminate the up elevator trim.

I can't wait to take it to an open field and really see how she flies. She'll get a bit of color next. Flight video soon.

Jon

 

[TooJung2Die]

Just waiting for the first chance to take her out where she can stretch her wings. How does it compare to the balsa kit?

I think it might need a dummy glow engine head up front.

Jon

 

[rockyboy]

She looks fantastic!

 

[Willy Nillies]

Awesome job!

 

[Michael9865]

Looks great.