First Flight - Semi-Sonic Beta Test

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I was fortunate to be asked to test out a new rocket from First Flight called the Semi-Sonic. Mine was a pre-production model. It arrived in a hanging bag with all parts and instruction included and neatly bagged. It is a sleek looking design which has two sets of 3 fins, one mounted just before the other, that gives a visual impression of speed.

 

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Construction began by locating the motor tube and making an 1/8" cut for the engine hook. The hook was inserted and bound into place with the addition of some electrical tape. The motor tube was then marked as per directions and the centering rings slipped into place. Both of the rings needed a slight bit of sanding along their inner surfaces to fit. They were secured with yellow glue. The thrust ring was then slipped into place, flush against the engine hook, and sealed into place with the addition of some more yellow glue. The motor mount was then set aside to dry.

 

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Although this is intended as a beginner kit, the builder is expected to cut the fins from sheet balsa using the provided template. This is NOT a bad thing and teaches an important skill. The templates were cut out and the outlines of the fins were transferred to the balsa stock. Instructions guide the correct layout to ensure everything fits and that the grain is oriented correctly.

 

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With the outlines marked, the fins were cut out with a razor knife using a steel ruler to keep me honest about such slippery concepts as "straight".

 

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Both sets of fins were then stacked and evened up with some sandpaper and then the leading, trailing and outer edges were rounded a bit with some sanding.

 

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The template sheet also comes with a wrap around fin marking guide. I much prefer these to the end marking type. The guide was cut out and taped into place on the body tube. The fins lines an lug line were then transferred. The guide was removed and the lines were lengthened to the entire length of the tube.

 

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The kit comes with a Kevlar shock mount. It was tied into place around the front end of the motor mount and filleted into place with the application of some white glue. A notch was also cut in the forward ring in order to pass the Kevlar.

 

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The balsa nose cone looked nice and needed just a small bit of sanding around the shoulder to fit the body tube. It was pre-weighted for stability. The eye screw was then screwed into place and sealed with the application of a drop of glue.

 

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When that glue had dried, I doused the cone in thin CA in order to harden in and fill it some.

 

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I allowed everything to dry overnight and then fed the Kevlar back through the motor mount to keep it from interfering with the actual mounting. A scrap of wood was used to swab yellow glue around the interior of the the body tube and then the motor mount was pushed into place with the engine hook aligned with the lug line and leaving about 1/4" or the motor tube protruding from the rear.

 

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The rear fins were mounted using a double glue joint and yellow glue with their back ends flush with the aft end of the body tube.

 

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When those had stiffened up sufficiently, I began applying the forward fins in the same manner along the same fin lines leaving a space about the thickness of the balsa between forward and rear fins.

 

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When all the fins were in place and the yellow glue had dried, white glue fillets were applied to all.

 

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As the fillets set up, some white glue was used to apply the launch lug along the marked line between two of the upper fins.

 

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The Kevlar still had to be fished through the motor mount and the body tube. Before doing that, I tied on the sewing elastic and then used a long piece of rod to poke it through. The kit came with a snap swivel for attaching the parachute but I did not attach it at this point; I merely slipped the elastic through it for safe keeping.

 

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With the launch lug in place, assembly of the Semi-Sonic was complete.

 

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I decided to use Elmer's filler for filling the balsa grain. Accordingly, I took out my stash, noticed it needed a bit of thinning and added some water. It was then brushed onto all the fins and onto the hardened nose cone. The rocket was then set aside to let the goop dry.

 

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The filler dried for a day and then I took the sandpaper to it, bringing it down nice and smooth. I went from 220 to 380 grit and then used a brush to remove the plethora of dust it generated.

 

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The rocket was then taken to the spray booth and given 2 coats of Kilz for primer. Normally, that stuff needs plenty of time to dry but the combination of heat and lack of humidity led to to chance just leaving it for 7 hours.

 

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The rocket was then taken back to the booth to be given a base coat overall of a very light lavender. It received 2 such coats.

 

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The lavender had a day to dry and then I began masking for the dark red contrast. My nephew came up with what sounded like a nice scheme but, unfortunately, I didn't have the masking skills to pull it off. I wound up with a simplified version of his idea. I masked off the forward fins and tried to continue the lines of the edges along the body tube. I also masked of the nose cone.

The rocket was then taken back to the booth and sprayed with 2 coats of a darker red. The red was not as dark as either my memory said or the top of the can.

 

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When the masking was removed, I found I had a few places of seepage under the tape but nothing that could not be fixed by hand. I did not like the scheme I had settled on as well as I thought I would have and it was certainly not as cool as my nephew's idea but it would work and it was definitely all mine.

 

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A day later I took a closer look at the runs and creeps. I was less happy even than I had been the day before. It wasn't anything that would be noticed from the launch pad but I noticed it and it bugged me.

 

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To fix it, I shook up the can of lavender paint really well and then sprayed a big puddle of it in a paper bowl I keep for just that purpose. The paint from the puddle was then brushed on over the bad places. Again, its not perfect but its much better than it was.

 

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The day finally came for the maiden flight and I prepped the rocket with dog barf and an Estes A8-3. It got favorable comments based on appearance from others present.

 

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Lift off was a quick affair and confirmed what this rocket looked like: it looked fast. Even with an A motor, it snapped off the rod.

 

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The streamer deployed while the rocket was still moving up, although not very quickly. A few seconds into the deployment, it was evident that the Kevlar thread I had used to attach the streamer had cut through the mylar and the rocket recovered as a tumble. Both rocket and streamer were recovered near each other and no damage to the former and only the cutting on the latter.

A video of the first flight can be found here: https://www.flickr.com/photos/[email protected]/3811545799/

 

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The second flight needed minimal preparation and started much as the first except that a B4-4 was loaded and the streamer was re=attached. IT was put on the pad and it still looked good.

 

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The flight performance was very similar to that of the first flight except for the altitude attained. It flew well.

 

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Deployment of the streamer was again marginally early but not a real concern. This time the streamer stayed connected and it came down the way it was supposed to. On inspection, the rocket seemed fine except for a small whack made when the cone rebounded.

A video of the second flight can be seen here: https://www.flickr.com/photos/[email protected]/3811549743/