Semroc - Penetrator {Kit} (XFS-MRK1)

Contributed by Dale Marshall

Construction Rating: starstarstarstarstar
Flight Rating: starstarstarstar_borderstar_border
Overall Rating: starstarstarstarstar_border
Published: 2010-12-13
Diameter: 0.92 inches
Manufacturer: Semroc
Style: Sport

Brief:
The Semroc "Penetrator" is an X-Kit. This kit is a reproduction of the Flight Systems Inc, kit first released in 1967.

Construction

The kit consists of:

  • Balsa nose cone.
  • 2 x 9" body tubes (0.921" OD).
  • Tube coupler.
  • Laser cut plywood fins (3).
  • 18mm motor mount kit including block and metal hook.
  • Kevlar+elastic shock cords.
  • Waterslide decal.
  • 12" plastic chute.

There were no instructions included with the kit, but there was a link to an online source. I didn't download the instructions since it looked like a very simple kit to build and it was. One thing I've been doing lately is installing the engine mount very late in the build process to give my rockets something flat to sit on and it worked out well for this kit.

I started out lightly sanding the three plywood(!) fins and the balsa nosecone. I wasn't too pleased with the quality of the balsa in the nosecone, it seemed soft.

When I assembled the body tubes I noticed one of them had small marks on one end for the fin locations. I extended the lines up the tube a bit to make the fin installation easier. The tubes went together quickly and easily with the included coupler.

While that was drying, I constructed the engine mount. The rings were notched which made it easier to slide them over the engine hook, and I was pleased to find the engine mount tube already had a slit in it for the hook.

I installed the fins and the two launch lugs and the Penetrator was ready for finishing.

Finishing:
I toyed with several paint schemes for this rocket, since it was being built for the EMRR "Double Vision" Contest. I wanted to get the most points possible so I was going for the "mirror" or "opposite" scheme. I wanted to do a candy-stripe and call it "Peppermint Stick" but I wasn't too keen on doing spiral masking. So I decided to use some of that way cool Testor's purple and gold glitter paint and go for more of a Mardi-Gras theme.

First, I shot the whole thing with a coat of primer and let it dry then sand. Repeat two more times for a pretty good finish. I stink at nosecones but it didn't come out too badly.

One one rocket (I had to build two for the contest) I started with a gold base coat and with the other I started with the purple. I waited for all that to dry, and then started masking. Again, I though about doing something complex, but eventually decided on a series of stripes around the rocket.

I masked off the area between the fins first since the fins were going to be a different color than the base color. Then I masked off the striped areas trying to keep the size of the stripes the same on both rockets. When that was ready I shot the overlay color on both rockets, waited for it to dry and then shot a second color for good measure (the gold didn't cover the purple too well on the first coat).

Construction Rating: 5 out of 5

Flight:
I launched this rocket on a pretty windy day so I started out with A8-3s in both. The launch was picture-perfect into the wind and recovery was reasonably close to the pad. For the second flight I used B4-4s and again the launch was perfect but a bit further from the pad. However, I noticed that I had a ding in one of the nosecones where it snapped back against the body tube. For the third launch, I again used A8-3s because I didn't want to chase them down. Again a perfect flight straight into the wind and perfect recovery close to the pad. Also, again, I had a ding in one of the nosecones. I will definitely need to attach more elastic the next time I fly these beauties.

Recovery:
The shock cord is too short on this kit. Definitely needs another four or five inches at least. Other than that the flight and recovery were great.

Flight Rating: 3 out of 5

Summary:
Overall this is a great kit and easy to build. I like the plywood fins but the balsa on my nosecones seemed not up to Semroc quality. If I had read the other review on EMRR I would have added more elastic. Oh well.

Overall Rating: 4 out of 5

Flights

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