Two 24mm motor cluster, skill level 2, payload section, parachute recovery.
This is a strange looking rocket that only gets stranger the more you think about it, but it is a good performer. It's not too difficult to build but a bit more challenging to paint if you want to use the default scheme on the facecard.
Construction begins with the marking of the BT-50 motor tubes. Each tube is marked in 4 places and the second mark from the end is slit with a razor knife for the engine hook. Before placing the hook though, a thrust ring is inserted and glued into place with the provided spacer tube.
With the thrust rings in place, the engine hook is inserted into its slit and a retaining band is slipped on to the appropriate mark and glued into place.
The kit comes with 4 cardboard centering rings perforated for tandem 24mm motors. I poked them out of their framework and sanded off the inner and outer nubs with sandpaper. The bottom ring, the one with an engine hook slot, was slid into place along both motor tubes and aligned with the first mark. The other centering ring was slid onto the other end of the tubes and lined up with the last mark. The rings were glued into place with yellow glue and filleted.
The rocket has two transitions that are meant as fairings betweens sections of BT-70 and the twin BT-50 motor mounts. These come in the form of a single symmetrical plastic molding that must be cut in 4 places. 2 cuts remove a short piece of "spacer" separating the 2 halves and the other 2 cuts remove the excess plastic that fits into the BT-70s. These cuts were made with a hobby saw and the rough edges were treated to some sandpaper. After they were cleaned up, the 2 transitions were slipped onto the assembly around the BT-50s.
With the transitions in place, it was time to mount the remaining 2 centering rings. These are in all respects identical to the first two rings. They needed a bit of sanding to fit around the BT-50s but fit into the BT-70 just fine. They were placed at the marks called for, filleted, and allowed to dry.
While posting a build thread on TRF, I heard that this kit has a history of problems with the transitions fitting into the BT-70s and a workaround described. When I checked I found that indeed the transitions do not fit into the BT-70s. The solution was to cut a pair of notches into the inner sleeve of the transitions, allowing them to be compressed a bit. With that done, the transitions fit fine and were secured with CA.
By the time I heard this, the transitions were already on and the notches had to be cut "on the fly". They are not pretty but they did work.
I decided to skip the entire rubber band and tri-fold travesty and try a FlisKits baffle designed for the BT-70. I started putting that together and then had to wait for it to dry. While it was drying, I worked on the upper section of the rocket.
The upper section is really quite simple. It consists of a plastic shoulder to transition from BT-70 to BT-60, a length of BT-60 and a plastic nosecone. I cleaned the flashing off of the plastic, sanded a bit and fit the pieces together. Although they are meant to form a payload bay, I never fly payloads and used CA to hold the whole thing together.
The next task to tackle was the fins. There were 3 balsa fins that were pretty thick and most notably tough as iron. When I try to sand a profile into fins, I always worry that I am going to snap them. This time I worried about having strong enough sandpaper. They should be sturdy!
I rounded all edges except the root. Then, using the lines transferred from the fin marking guide, I placed the fins with CA. After letting the CA cure, I began filleting with yellow glue.
Then the baffle from Fliskits was ready to install. I found that it fit perfectly in the BT-70. Installation consisted merely of swabbing a glue ring in the body tube and pushing the baffle down into place, making sure that the Kevlar® was oriented in the right direction (towards the nosecone).
Another item that still needed to be addressed was the installation of the launch lugs. There are two of them. One is located on the lower BT and the other on the upper. A line had been marked earlier and I glued them on with the aid of a rod to keep them aligned. That left me ready for finishing.
PROs: Fairly easy cluster build
CONs: Tri-fold and rubber band mount, Fairing shoulders do not quite fit and must be modified
I still had not picked up any Elmer's Wood Filler so I started off the finishing by sealing the fins with sanding sealer. I made sure to shake the bottle well to get all the particulates suspended and started to paint it on. After 2 coats, I gave it a light sanding and applied another 2 coats of sealer. Upon inspection I realized that I needed another 2 coats for a total of 6.
Priming was done with Kilz. I applied a total of 2 coats and then sanded.
The first paint to be applied was Testor's gray. I did not paint the whole rocket, just the lower part where there would be some gray transitions.
Red was the next color to be sprayed. I masked off the areas that remained gray. Again, this was fairly easy and caused no problems. Those could be expected with the black because the black was to be blended into adjacent colors.
I masked off the areas that were supposed to stay red and then set the rocket up on the turntable in my booth. I decided to try and eyeball the black. The middle section was easy because the transitions are sharp and the rocket was masked. Gradually transitioning from gray to black and from red to black was another matter. It was done completely by trying to control my aim and the distance to the target.
It actually turned out better than I had feared but there are a few areas that will see the application of sandpaper to try and remove some of the black. This was my first attempt at something like this and I can only get better at it, right?
I used #600 sandpaper to remove some of the black overspray near the top of the fin can. It did not do a perfect job but from any reasonable distance, the original problem is now hard to see. I decided to let it go at that.
At the end of the paint phase, I was a bit disappointed. It did not look terrible but the rocket did seem kind of plain. Thankfully, the decals to care of that problem.
I was very pleased that this Estes kit has forgone the crack and peels in favor of real waterslide decals. I no longer take that for granted after getting the trashy stuff in my Maxi Brute Honest John. The pleasure only went so far, however.
I started with the silver flames that go on the fins. I found that the decal material was very stretchy and difficult to place. After floating off the backing, it wanted to rip the surface instantly and brushing out the bubbles was time consuming. This was true for both sides of each of the fins. I was not looking forward to working with the big decals on the payload or nose section. The bid decals went on easier though. They slid right into place and were smoothed out with a minimum of fuss.
When all is said and done, the decals really dressed up the rocket to where it looks pretty good. Mine is not as good as the face card but it is perfectly acceptable to me.
Construction Rating: 4 out of 5
For the maiden flight, I loaded a pair of D12-5s. That almost cost me the rocket. It took off in a flash and just kept going straight up...way up. When the chute deployed, it had plenty of time to drift a long way. I got the right vector for where it came down or I never would have recovered it. My direction was right but the range was way short. When I did find it, it was in great shape and ready to fly again.
For the second flight, I loaded a pair of C11-5s. It too had a perfect but not so extroverted, flight profile. I actually managed to get it back without crossing any highways or barbed wire fences. Again, it was in perfect shape.
PROs: High performer.
CONs: Easy to lose do to extreme height.
As mentioned in the build, I used a FlisKits BAF70 baffle in this rocket. It performed flawlessly. In place of the 18" plastic chute, I used a 15" nylon.
Being a bit suspicious of the baffle, I used a small bit of dog barf for the first flight. I need not have bothered. I did without on the second flight and the system worked perfectly.
Flight Rating: 5 out of 5
This is a cool rocket that is a good and easy introduction to clusters. It's also nice in that it looks a bit out of the ordinary.
Overall Rating: 4 out of 5