Sunday, September 13, 2015

Estes MIRV Review (flight report added)

I didn't anticipate writing a post on this kit but now am even more fascinated with it. I hope to fly it this coming weekend and will fill in a flight report shortly thereafter.

Overview

This is a four stage rocket! Others may contest this fact but it has one booster and three parallel- staged sustainers. 3 + 1 = 4. That's my story and I'm sticking to it.  The components are interesting for Estes. It has a plastic manifold to direct the blow-through from the booster to the three sustainers and the body sections are made from white foam.  The foam dings easily but  makes for a quick build and a light rocket. For several reasons including laziness, I didn't spend a lot of time finishing the rocket.

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Booster Section

The booster section consists of a motor tube, a metal retainer clip, a short foam body, a two part plastic manifold, a dowel, and three, two piece, die-cut fins. These fins, and one fin on each sustainer, have to be glued together. This wasn't a problem per se but I would have rather had them as a single piece. I assume this was done to save a skosh of balsa stock.

The foam body was done nicely and made the rest of the assembly easy. It holds the retainer snugly and aligns the fins perfectly.

The two part manifold requires some plastic cement and attached easily to the motor tube. It also holds the dowel that forms the launch rod for the sustainers.

Oh yeah, there is also a balsa standoff and a launch lug. The standoff also fits nicely in slot in the foam body.

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Sustainers

Each sustainer consists of a foam body, a long section of BT-5, a motor block, a launch lug, three balsa fins (one of which is two-part so that's 4 pieces of balsa each), a two-piece plastic nose cone and a standard Estes rubber band shock cord.

Again, I like the foam bodies. I won't sweat the dings and it does a great job aligning all the parts.

The motor block goes in with a spacer and the shock cord via a tri-fold mount. I generally don't use these but did so in this case. I especially don't like them in BT-5's since I can't get them far enough in not to interfere with the recovery components. These sustainers use tumble recovery so there is little chance of snagging.

The lugs are cut from a longer section and are staggered between the three sustainers so they will all fit over the dowel on the booster. The engines protrude a quarter inch or so and slide into the plastic manifold. I think the whole thing is pretty slick. The only issue I see is that the body sections do not fit very snugly at the nose end. Others have been concerned about this and some have held them together with a small amount of tape.

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Finishing

Because of the foam parts, you need to be careful with the type of paint that you use.  I chose Krylon H2O for the booster and Testor's spray enamel for the sustainers. I left the manifold and nose cones in their native black plastic. The kit comes with a slew of waterslide decals. I may put them on someday. This is actually one kit that I would have liked to have had peel and stick decals.

Flight Prep

As mentioned earlier, the booster used a standard clip. On the sustainers, the motors are retained with a wrap of tape around them and the lower body. I haven't done this yet and am not sure what this wrap will do to the fit between the motors and the manifold  Time will tell.  You then add some wadding, stuff in the shock cord, put the cones on, and slide them all together.

Flight

I flew the MIRV on a C6-0 staged to three A10-3s. Unexpectedly, it boosted cross-wind and headed over the soy bean field. All three RVs staged and headed off in slightly different directions. The booster and one RV were lost to the beans. The land owner asked us to stay out of them as much as possible so I just grabbed the parts that were tracked and made on pass along some central open paths. Maybe I'll get lucky and someone will find them.