Brief:
This latest Semroc offering is a Retro-Repro of an old Century classic. I never had a proper introduction to Centuri kits. They were rarely sold in the area I lived as kid. Occasionally, a couple Centuri kits would pop up at the local Hungate's, but for the most part, Estes was king. I'm glad to see some of the Centuri classics brought back to life giving us BARs a chance to catch up on stuff.

The Defender boasts 3 x 18mm friction fitted motor mount system and parachute recovery. The rocket is clearly styled after the early NASA Saturn rockets. I like that!

I ordered my kit the day Semroc announced the kit's release. As a result, I ended up getting a kit with an early production number, #26. No matter, I bought this kit to build and fly, which is what I promptly did upon it's arrival!

Construction:
I'm always amazed at how many parts Semroc can fit into such small packages. This bag was no exception. Everything was neatly an securely packed. The parts included are as follows:

• 1 Balsa Nose Cone (BC-516)
• 1 Body Tube (ST-530)
• 1 Balsa Transition (BR-510)
• 1 Body Tube (ST-1020)
• 1 Balsa Transition (BR-10165)
• 1 Body Tube (ST-1652)
• 3 Body Tubes (ST-790)
• 1 Body Tube (ST-1620)
• 1 Laser Cut Fins
• 1 Laser Cut Balsa fin strips
• 3 thrust rings
• 2 standard lugs
• 1 screw eye
• 1 length Kevlar® thread/recovery leader
• 1 length elastic cord
• 1 clay weight
• 2 12" plastic parachute kits
• 1 sheet waterslide decals

PROS:

• The instructions were well illustrated and easy to follow.
• All the parts were typical of Semroc's high quality. The laser cut fins are a treat, and the balsa cones and transitions are the BEST in the business.

CONS:

• I was so anxious to get started building the kit, I never considered the paint scheme before I started building. The instructions have the builder assemble the three main engine tubes right off the bat. This involves gluing the three longest tubes in a triangular fashion and then inserting them into the short lower body (fin) tube. Then a baffle/centering ring is glued to the other end and the Kevlar® thread is also attached. Another body tube slides over the centering ring and completes the lower body tube assembly. If following the instructions this way, it will complicate the painting later. Just be aware.
• The fin stock from Semroc is often a little softer than I would prefer. This kit was no exception. This can be remedied in many ways with very little effort. Papering the fins, using a commercial wood hardener, or even a soak with thin CA can easily cure this. I'm not overly concerned with this issue, since it is good practice to do those steps regardless. To be fair, I assembled the kit without doing anything extra to the fin stock. It flew and recovered without any damage. So what do I know anyway?

Finishing:
I would suggest that anyone building this kit to be smarter than I and paint the three engine tubes after they are glued together. This should be done after step #4 in the instructions, before the lower and upper tubes are glued in place. I would also pre-paint the balsa strips that slide between the "LOX" tanks and the fins as well. Perhaps the upper and lower tubes should be pre-painted as well? This will make finishing the model much easier and save time masking later.

The supplied decals are monotone black featuring two checkerboard sections, a large roll pattern, and the "Defender" logo. They really dress up the appearance of the model and look great against the white background.

This decals have nice, crisp lines and are very easy to work with. I usually fear the decal process, but that feeling is diminished when using Semroc decals.

Construction Rating: 4 out of 5

Flight:
This rocket is to be flown as a triple cluster. You can use anything from 3 As, 3 Bs to 3 Cs. I chose to use B6-6s for its first flight. I borrowed a clip whip from a fellow club member to hook up the igniters. All three motors lit as planned, and the rocket turned in a picture perfect flight. It flew straight as an arrow to about the projected height for a B motor in this rocket...900ft or more. Very enjoyable flight. Even with the 6 second delay, the rocket was still barely coasting upwards when the ejection went off. I'm not sure if I'd use the recommended B6-4s. I think a trio of C6-7s would be glorious.

Flight prep was pretty easy. I used about 5-6 squares of normal recovery wadding. The motors are to friction fit with masking tape. Once around each motor with the tape was all that was needed to get a good fit on mine.

Recovery:
The elastic shock cord is anchored to the engine tubes by a Kevlar® leader.

I forgot to attach the elastic before heading out to the range. I suspect the supplied length of elastic was more than adequate for this model, but I ended up using a longer piece from my range box that I installed while on the field.

The kit comes with two 12" plastic chutes. I replaced the two chutes with a single 12" nylon hemispherical parachute. That was just about perfect for this ricket, which resulted in a slow decent that still ended up drifting about 100 yards or so from the pad. No damage sustained.

Flight Rating: 5 out of 5

Summary:
I have been very pleased with every Semroc purchase I have ever made. This is a quality kit that goes together easy and is bound to deliver some spectacular flights. Just do a little thought and preparation ahead of time for painting and finishing the rocket and this will be a very enjoyable build. Very sharp looking.

Overall Rating: 4 ½ out of 5

Brief:
This is a reproduction of a Centuri design dating back to 1967 featuring a cluster of three 18mm motors crammed into a stretched BT-60. It takes its inspiration from a smaller brother called the Recruiter and the much larger Saturn 1b. If you like clusters, you’ll love this one in terms of sheer performance and design.

Construction:
Craig’s earlier review detailed out the parts list on this one and was accurate. Semroc quality is A-1, featuring Euclid tubes and their own homespun cones and transitions.

The instructions are very good, spanning about 30 steps over 5 pages. This one is best built in phases rather than counting on knocking it off in an afternoon, and I wound up spending about 6 hours on it plus finishing time, which is pretty significant for this one. I would probably rate this around a 3 on the 5-point skill-o-meter as clustering is not for rookies plus there are some challenging fit and finish aspects.

As Craig noted, the first construction step involves gluing together the “fuel tank” tubes and before doing this you’ll want to think through your paint options. One option (Craig’s suggestion) is to paint the tanks before assembly (gloss black) as well as the fin strips a gloss white. Another option is to wait until everything is together and mask/paint per instructions. Either way, you’ll still have some tricky masking. I pre-painted the tanks (glued together first, then painted the 3-tube assembly) and the fin strips, but there are 3 fins that wind up overlapping the fin strips that need white paint plus 3 more fins that get black paint, which meant I had to mask over the black tubes and somehow try to prevent overspray down into the lower BT-60. Having done it that way, I’m inclined to think it’s less of a pain to follow the standard plan and mask off the white fin strips, hitting the tubes and 3 fins with black later.

Once the 3 tubes are bonded together, you then slip a BT-60 over them. It’s a very tight fit and will flatten a bit on 3 sides as a result. At the other end, you tack on a centering ring that also serves to block off some of the exposed tube/exhaust area, which helps the rocket survive multiple flights. The Kevlar® shock cord is anchored in this joint, well protected from exhaust gasses.

The upper BT-60 slips over the centering ring, completing the main body assembly.

There are a total of 6 fins with two slightly different patterns used. Pay careful attention to them as the difference is subtle--one set has a little overlap tab and is designed to extend beyond the lower BT-60 to bond to the fin strips; the other set rests flush with the forward end of the lower BT-60. Alignment is handled via a marking guide template in the instructions (it works OK but I generally prefer a wrap). Before bonding the fins though, you need to slip in 3 fin strips between the fuel tank tubes (these are the white strips in the photo). This is also a very tight fit and winds up stretching the flattened sides of the lower BT-60 back out to a fairly circular shape. Again, think about the paint plan before doing this... Once these are in place, you then bond the 6 main fins.

There is a pretty straightforward payload section on this also, consisting of two tubes and transitions. Note that the upper tube needs to be packed full of clay for weight/stability.

Finishing:
As noted, painting is a bit of a pain on this but can be worth the effort. I pre-painted the tubes black and fin strips white, masked off the tubes, then painted the whole rocket a couple of light coats of white primer. I followed up with 2 coats of gloss white, then masked off the white for painting the 3 black fins and upper payload section.

The decals provided are excellent, covering 3 roll/checker patterns and a bold “Defender” logo/name. The cover art also shows a couple of black trim stripes at the transition seams, which I accomplished using a fine tip Sharpie.

I wrapped up with a couple of coats of Krylon clear coat for protection.

Construction Rating: 5 out of 5

Flight:
First flight was at the National Sport Launch in Muncie, Indiana and wound up being the closing flight of day 1. I hastily loaded the 3 tubes with B6-4s to beat the check-in deadline but forgot to take my clip whip out to the pad. No problem--as closely packed as these 18mm tubes are, I was able to twist all 3 igniters together for a proper cluster prep. I managed to get all 3 lit, and the rocket absolutely screamed up to well over 800 feet.

Craig’s review noted he was a bit early with -6s, and I’ll say my -4s were way too early, as this rocket was still climbing at a good clip.

As an aside, talking to Carl and the Semroc gang at NSL, it seems this can fly OK with two of three motors lighting, but one would not be enough to get it stable off the rod so make sure you prep carefully including packing a little wadding in the tops of each motor to prevent accidentally lighting one in the air off the ejection of others if it didn't catch on the pad.

Recovery:
The kit comes with two 12” chutes for some reason, which are probably an effort to protect the 6 fins. I didn't want the long walk so I just packed one, which was fine despite the fact that my finished model weighed in at 2.8 ounces versus the kit spec of 2.2. You might consider swapping out an 18" if worried about a hard landing.

Flight Rating: 4 out of 5

Summary:
This is a very cool cluster rocket, nice looking, and stylish. Be sure to fly in a big field though, as it will soar on you.

Overall Rating: 4 out of 5