Brief:
This is one of 10 "ready to build" models released by Semroc at NARAM-52. The Mini Explorer is based upon the Centuri larger scale Explorer, but downscaled to fly on 18mm motors.

Construction:
Parts were excellent quality, and the sealed bag contained:

• Balsa nose cone
• Series 10 slotted body tube (1" ID)
• Series 9 stuffer tube (1" OD)
• 18mm motor mount (tube, metal hook, centering rings)
• Laser-cut balsa fins
• Elastic shock cord
• 12" plastic chute
• Waterslide decals

The "ready to build" series is Semroc's answer to numerous requests for "ready to fly" rockets. In the RTB series, the modeler still has to actually do work to build and fly the model, but the design includes a number of features that simplify the build process, including slotted body tubes for thru-wall fin mounting, an alignment jig, and a stuffer tube to serve as shock cord anchor and reinforce the body tube.

The RTB series are all fairly easy to build, with almost all of the construction process using the same standardized steps. This is definitely a skill level 1 model, and aside from paint and surface prep, the total build is well under an hour.

The motor mount is a standard BT-20 tube, metal hook, and a pair of centering rings. Unlike the typical mount, though, there are two different centering rings involved with slightly different diameters. Pay careful attention to the instructions, as the white ring goes forward and the brown ring goes aft. This is critical later in the process. Surprisingly, the mount does not include an inner motor block, so the metal hook will have to hold for the life of the model. I found the centering rings a bit too snug, and had to peel off a layer of paper from the inside of each, plus one layer of paper from the outside of the white ring.

The stuffer tube contains a couple slits, which are used to slip the elastic shock cord through, serving as an anchor. After knotting the cord and reinforcing with a drop of glue, it's ready for the motor mount. The motor mount slides just a tiny bit into the stuffer tube, enough that the forward (white) centering ring is flush with the aft end of the stuffer tube. Do not slide the motor tube any further--the aft/brown ring is too large for the stuffer tube and instead is used to align inside the large series 10 body tube. Sliding the assembly into the body tube to dry fit is a good idea at this point, to make sure the forward centering ring is aligned properly inside the stuffer tube. Once the motor mount/stuffer tube assembly has completely dried, it can then be glued inside the body tube (though be careful to make sure the metal engine hook does not line up under a fin slot).

As noted, fins are thru-wall, and the fit against the motor tube was very good. Included in the kit is a nifty little cardboard fin alignment jog, which fits smoothly on the series 10 body tube and has notches to accept 3 and 4 fin patterns. The fixture fits well for most fins in the RTB series, though for fins that have a significant span and are not swept back very far, the slots in the jig are not long enough to be of much use. That was not the case with this model, though.

Tack on a launch lug, make the chute, and add a screw eye anchor to the nose cone and construction's done.

Finishing:
I went with the stock paint scheme on this, starting with two coats of primer, following up with a couple thin coats of gloss white, then masking off to paint the fins blue and the nose cone black.

The waterslide decals add the name, a roll pattern, and a blue stripe towards the top and were great to work with.

Construction Rating: 4 out of 5

Flight:
The first flight on this one was using a C6-5, and on a day where just about all the RTB series were zipping off the pad, this one stood out as among the highest flying, which kind of surprised me. It was absolutely straight, no sign of a roll, and the -5 wound up being just a bit early.

Recovery:
The chute worked fine, no damage to the model on hard, dry grass.

Flight Rating: 5 out of 5

Summary:
I think the steps Semroc has taken to simplify the build process in their RTB series are helpful. With this being such a solid flyer, this is certainly a fine candidate for a first build.

Overall Rating: 4 out of 5