Interceptors and siblings: Estes Trajector
 

This is my third build of a Trajector. The first one got lost into a creek on its first launch. The second was OK, but I didn't like how the plastic pieces glued together. So, I built it again to get it better, and in part, to add to my build of Interceptor family members.

The Trajector is basically an E2X rocket, but in the Pro Series II group. There's no painting or cutting. It's mainly gluing and sticking on decals. Not waterslide decals, but stick in place decals.

The motor mount is a lot like the ones in the E2X rockets, with plastic rings. Since it uses larger motors, 29mm, the bottom of the mount screws on with threads, instead of just twist-on detents for a better grip.

The fins are some kind of plastic, ABS I think, and maybe the pods are as well. This member of the Interceptor family only has three fins, and they are all the same. At least they have pods on the tips of the fins. The lugs are also of the same type of plastic.

The nose is the same as the Interceptor-E and as the Cosmic Interceptor.

When I build the Trajector before, I kind of messed up the fins. Which, given how basic this rocket is, kind of surprised me.

Each fin comes in two halves, like a clam. The instructions say to assemble the two halves with CA. Although that is brittle glue and not good for structural places, in this case it seemed to be OK. One end of the fin is mechanically held together by the motor mount, and the other end is mechanically held together by the pod.

On the prior builds, my mistake was more about dexterity. While I was holding the fins to apply glue, and while I was squeezing the two halves together, I got glue on my fingers. Which, as per the second law of thermodynamics, immediately transferred from my fingers to the surface of the fins. So, I goobered the appearance of the fins. The more I assembled, the more of a mess I made.

This time, I skipped the CA, and violated the rules by going with 15 minute epoxy to assemble the fin halves. I first scuffed up the inside of the fins with 180 grit sandpaper, to give the glue purchase. In fact, the smell of the plastic of this step was identical to the smell of cutting ABS plumbing pipes, so I think that's what was used.

To avoid gumming up the surface of the fins, I masked them off with blue tape. Now, if any glue squeezed out of the joint and onto my fingers and back onto the fin, its destructive influece would be blocked by the tape.

Once the fins dried, I did a similar technique for the pods, by masking them off to glue the halves together, and then masking off the fins before attaching the pods to the fins.

The motor mount is assembled by gluing the two rings onto the motor mount tube. The spacing and alignment of the two rings is critical. If they are rotated relative to each other, the fins won't fit into both rings.

Also, if the fins are spaced apart as per the instructions, I don't think the fins will fit into the space between the rings either. The instructions said to position the rings at 1" and 3 3/16" from the back of the motor mount tube. When I dry fitted the pieces, I couldn't get the fins to go into place. I had to adjust the upper ring at 3 5/16" from the base.

Actually, by gluing on the lower ring first, and using the fins as spacers, the top ring can just be glued into place without measuring it. Just be sure to remove the fins before the epoxy sets.

Also, remove any epoxy from near the mounting point for the fins. I didn't do that on a prior build, and a glob of epoxy prevented the fin from sliding in far enough. Then, I had to grind off a corner of the fin tab. This time, I used a Q tip to clean out the fin mounts.

Once the rings for the motor mount are set, and the thrust ring is installed, the motor mount and fins can be assembled.

Again, I added blue masking tape to the fins to I wouldn't transfer epoxy from the glue joint onto the aesthetics of the fins.

The launch lugs were epoxied into place with the same protections.

Oh yeah, I scuffed up each of the plastic surfaces with 180 grit sandpaper before epoxying it.

No fillets are needed, since it is through-wall assembly and the fins should be held firmly to the motor mount and the internal plastic rings. Those rings act as internal alignment guides too, so they come out 120 degrees apart with no problem.

Now, there's not much left to build. Just the recovery system.

The Trajector comes with a variant of the tri fold. It has a couple pieces of plastic that hold the shock cord, and then that is glued inside the body tube. It's OK, but I went with a baffle instead.

Once it was assembled, I needed to see where to place it. So, I laid out the nose, the parachute and cord , and the baffle on my measuring board. I decided that about 9" would be enough space to hold the shoulder of the nose, the 'chute, and the cord. (On the photo, it is from 10" to 19" on my board)

I fastened the shock cord to the baffle, with a eyelet. The eyelet was attached to the top of the baffle after I reinforced it with two disks that came with the baffle.

To glue the baffle, I used an old-time technique. Get a long dowel and mark it with tape about how far the glue should go in. Then, put a big goop of glue on the end of the dowel, and insert it into the body tube. At the right distance, smear that goop around the inside of the tube. Do that a few times.

I did that for the top and bottom of the baffle. I also wetted the baffle edges with glue so it would be ready to stick when I shoved it into place with that dowel. Oh yeah, I had to do it over some scrap paper, because that glob sometimes dripped before I got it into the tube.

Being an E2X-equivalent, it's basically done now. The nose is already painted, and only the decals remain.

But, on my prior builds, I goofed the positioning a few times. That adhesive grips immediately, and if you try to move it, it lifts the silver coating on the tube.

This time, I used the drop of soap in the water trick. I mixed up a small amount of water with a drop or two of shampoo. Before applying the decal, I wetted the back of it with the soapy water. I also spread a thin layer of soapy water on the body tube where the fin was to go. This film gave me a small opportunity to position the decal before it stuck hard. When it was in place, I wiped down the decal with a towel, squeezing out the water and letting the adhesive bond to the paper tube.

Now, it's finished. And, it's posing with my Interceptor K-50 which started the family.

I built my Trajector with the Accur8 NASA skin, sans pods (I like pods in general, but am not a fan of the pods on this particular kit. To me, the Pursley skin gives it a heavily-decaled look that is even more Interceptor-ish (although the NASA skin is probably not the *most* Interceptor-ish option, it was my favorite).

This might help anyone building this kit, or a kit with this type of fins.

I was worried about getting fingerprints on the fins, so I added little “handles” to each half. I did this by forming little “Ts” with masking tape. The top of the “T” getting stuck to the fin surface, and the body of the “T” formed glue-side to glue-side of the tape, and standing out from the fin surface. Made it very easy to apply CA then pick up each fin half and press them together.