Step by Step converting Cosmic Interceptor to RC Interceptor rocket glider

[burkefj]

I wanted to do a step by step in case someone wanted to replicate what I did taking a cosmic interceptor kit and making a standard Interceptor styled RC rocket glider. Estes is closing these kits out and I think they are a steal even just for the cone and body tubes....The performance is quite good on E-6 motors and the glide is very reasonable. I've done four different versions and this is the lightest one. So, i may be talking to myself, but here goes..
I'll post a pdf of the tracings of the parts, it's just three normal sheets.

Need

6mm depron foam.
two great planes wing skids
two rail buttons
two brad head t nuts and screws
24" by 1/8" carbon rod
blenderm tape
two two prong dubro micron control horns
foam safe CA+(hot stuff UFO) or bob smith super gold plus.
two 9-11 gram servos
receiver
1s 450-500mah battery
Cosmic Interceptor kit.

From the kit you will use one coupler, the two body tubes, the nose cone, and the 24mm motor mount tube and the two fiber centering rings.

For this version I already knew where it needed to balance so I wanted to optimize where the equipment went to avoid any balast weight. To do this I knew would have to put the receiver and battery near the rear of the model but still be able to access it. I devised a method of a removable motor mount held in place by the rear rail button screw to allow installation and removal of the flight battery, worked like a charm. This model is 39" long and 24" wingspan and has a rtf weight of 10.5 ounces with a wing loading of around 6 oz/sq foot. It boosts vertically like it's on a rail and seems to boost to around 500-600 feet.

 

[burkefj]

1)glue the two body tubes together using the coupler.
2)mark the body tube for the two wing slots and the tail fins.
3)Cut out the slots. Use some scrap depron to check the fit of the slots, sand them so that they are snug but not overly tight.
4)Cut the motor tube to 2.75"
5)Bend the long motor hook to 2.75" and cut off the excess
6)tape the motor hook onto the motor tube with the blenderm tape
7)glue one centering ring at the forward end of the tube and the other about 1.5" from the back end.
8)cut out the little foam half circles
9)glue the half circles about 2" in front of the rear of the wing slot, one above and one below the slot, I used a bamboo skewer poked in the foam to insert them. These will form a pocket which will hold the receiver and battery above and below the wing.
10)Install a rail button on the bottom rear of the body tube 1.25" in from the end, install another one 2.5" from the forward end. I used brad hole t nuts which have no prongs on them, they fit inside of the rail button. I used an exacto to counter sink the rail button so that the screw will fit flush.
11)Mark two holes for one of the wing guards just in front of the rail button and into the nose cone, this will help protect the rail button when landing, and help hold the nose cone in place, install it into the holes.
12)do the same for the rear button, install the wing guard at least 2.75" forward of the rear of the body tube so that the prongs won't interfere with the motor mount.
13)Cut out the wing and vertical fins, sand the edges round if desired. Cut the carbon spar to fit the wing span and cut a v slot in the bottom of the wing for the spar. Drag the end of the spar in the v groove till it fits nicely into the slot. Glue the spar in place with foam safe CA+ Once set, tape over the spar with blenderm tape.

 

[burkefj]

14)cut the elevons, trim 1/16" off each end to allow for clearance.
15)cut the bottom leading edge of the elevon at a 45 degree angle.
16)using blenderm tape, tape the elevons to the top of the wing first with the elevon sitting on top of the wing, wrap the tap all the way around to the bottom of the wing.
17)fold the elevon back flat with the wing and apply blenderm tape to the top of the joint. This makes a slop free flexible hinge with plenty of movement.

 

[burkefj]

18)insert the wing into the body tube, make sure it is centered and then apply foam safe CA+ to both sides.
19)Insert the motor mount into the rear of the body tube, mark the centering rings where the slots for the vertical tails are
20)cut notches in the centering rings to clear the vertical fin tabs.
21)Glue the vertical fins in the slots with foam safe CA+, angle isn't critical as long as they are approx the same.
22)Test fit your receiver and battery in place
23)test fit the motor mount, the front of the motor will butt against the wing, the notches will slide over the vertical fin tabs, and the rear centering ring should be right in front of the rail button screw, when you tighten the rail button screw it will hold the motor mount from falling out, any forward thrust will be taken by the wing trailing edge. You may need to clearance the centering rings slightly to slide over the t nut and vertical fin tabs.
24)poke holes in the bottom of each elevon approx 1" from the inboard end and glue in the control horn. Make sure to put some glue on the little tabs that poke through the top of the surface to lock them in place.
25)make two .039 music wire pushrods, put z bends on each end in opposite directions. They should be approx 4" long, make that they are such that the servo will not be sitting on the taped wing spar, make the rod shorter or longer to avoid this.

 

[burkefj]

26)insert a control rod into the outermost hole of the control horn from the inboard end.
27)attach a servo to the other end, servo should be inboard and servo wire should point toward the back of the model.
28)make sure your radio is setup to move the servos the right direction, and they are centered.
29)Cut a rectangular slot in the bottom of the body tube to pass the servo wire through, this slot should be cut so that it enters into the little section designed to fit the receiver(to the rear of the foam half circle and in front of the back of the wing..)
30)Poke the wires through the slots and out the back of the model, then attach to your receiver. Make sure everything is correct.
31)Push the receiver and wires into the bottom reservoir under the wing forward of the motor mount.
32)Turn on the radio and plug in the receiver battery. Note I have a wire that plugs into the reciever with a jst connector that is long enough to stick out the end of the model so I can plug in the recevier battery without pulling on the receiver.
33)Glue each servo to the surface of the bottom of the wing using CA+ foam safe glue so that the pushrod is straight and the control surface is neutral. Tape the servo wires down and tape over the holes for the wires to keep water out.
34)push the battery into the top compartment and poke the wires in place. Slide the motor mount in place and tighten the rail button screw to hold it in place.
35)install a loaded motor and balance the model, it should balance right where the leading edge of the wing hits the forward strake. Add weight to the nose or tail as required.
36)Set your elevon throws to 5/8" up and down and the aileron to 70% of elevator throw. Set your glide trim to 1/8 to 3/16" of up trim. For boost use neutral or a few clicks of down trim for the first flight.
37)Boost straight and pitch the model over after burnout while you still have airspeed, then click in your up trim, adjust your glide so it doesn't stall and fly it in s patterns or circles over the field to ensure you can make it back, set up for landing, a foot or two off the ground gently flare for touchdown.

 

[burkefj]

There you go, took me about 3 hours to do the build, longest part was cutting the slots in the tube. Test flight today was spot on.
I'll post the templates later. Added some panel lines and waiting for my stickershock23 IntR/Ceptor vinyl to finish it off.
I'm at a little under $100 for the entire model including kit, foam, parts, electronics and the vinyl.
Other than painting the wing tips red, there is no painting required, the nose cone is white and you can use a sharpie to set off the panel lines, the tube and foam is white. I did put a stripe of black vinyl on the bottom of the tube before I started, that will help keep the tube bottom from getting wet when landing on grass.

Frank

 

[McKailas Dad]

Hmm, I think I may have one of those stashed in my build pile, and also have a fair share of RC stuff laying around. Other than the battery and maybe a few other things, I may already have most of what is needed

Thanks for sharing!

 

[burkefj]

Here is the pdf of the wing/tail pieces....Print them with no page scaling, no page fit and no margins..

View attachment InterceptorConversion.pdf

 

[burkefj]

 

[burkefj]

I'm writing an article on my RC interceptors so wanted to revisit this design. I still had several Interceptor cones but Estes does not have their 2" tubing for sale any more. If you had a trajector cone you could also use that as it is identical. I found that BMS ST-20 couplers fit the cone shoulder perfectly, so I cut a 1.25" long piece, slipped it over the shoulder and now it fits the ST-20 with just a barely visible lip. In order to keep the cone from slipping down I cut a 1/4" long ring of ST-20 and glued it to the front of the coupler section. The ST-20 is lighter and I got rid of the middle coupler using a single 27" long section.

I made my motor mount with foam centering strips instead of foam rings which are easier to fit and got rid of the un needed motor clip. The foam strip method allows me to insert the motor tube and not interfere with the fin tabs ir rail button. I got rid of the skids that are not really needed and mounted my rail buttons further back.

The new depron is a bit lighter as well and I changed the wing spar to 2.5 mm and so I had to move my wing forward to 5.5" ahead of the rear of the tube to retain cg without nose weight. I also moved the fins forward a bit too for looks. I inset the servos into pockets cut into the body tube.

This reduced overall weight to 9 oz rtf. Here she is and here's a family photo with my H-13 4" version, the new ST-20 version for E-6 24mm motors and my 1250 kit conversion for 18mm D2.3 motors.

 

[burkefj]

Some more of the build photos

 

[burkefj]

And a few more before the major decals. This one I reduced the tip pod size and it came out under 9 oz and just a few grams nose heavy without any added weight.

 

[burkefj]

Here is the maiden of the new lightweight version.

 

[modeltrains]

Flight speed of launches had a great sense of "This is a real thing with real mass and real inertia and real momentum".

 

[burkefj]

Stickershock is sending me a German themed set to finish the new one off .

 

[burkefj]

Finished her off.

 

[McTschegsn]

Looks awesome and like a very good flyer! What motor did you use on the flight on youtube?

 

[burkefj]

Looks awesome and like a very good flyer! What motor did you use on the flight on youtube?

E-6 is what all my models this size use.

 

[McTschegsn]

Thanks for that heads up