First Flight Hobbies - Semi-Sonic

Contributed by John Lee

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar_border
Overall Rating: starstarstarstarstar_border
Manufacturer: First Flight Hobbies

Brief:
LPR, Sleek, 18mm, Parachute Recovery

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.

Construction:

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.

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. 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". 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.

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.

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®.

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

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.

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

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.

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.

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

Finishing:
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.

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.

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. It turned out my hunch was right this time and I was able to sand it with #400 without any gumming problem.

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.

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.

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.

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. 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.

Construction Rating: 4 out of 5

Flight:
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.

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.

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: http://www.flickr.com/photos/23694991@N03/3811545799/

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

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

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.

For the third flight, it was just a matter of repacking and then loading a motor. I chose a B6-4 this time. Although close inspection would show some damage, it still looked good on the pad.

The flight profile was a bit different this time. If anything, it whipped off the pad faster but it also did some spinning on the way up. It had not done that before.

This time the ejection seemed to be right at apogee. The streamer deployed with a pop and it drifted down. The smiley damage in the tube was reinforced and there was a small nick in the cone.

A video of the third flight can be seen here.

The final of my test flights of this rocket saw me introducing a C6-5 to the setup. It was loaded and put on the pad. The ignition and flight went well. There was no repeat of the previous spinning. Ejection again seemed just about perfect but, like the first flight, the streamer parted ways with the rocket. It tumbled down fine.

Checking the rocket over after the 4th flight, I saw that the elastic bounce was an issue. It probably needs a bit longer of a harness. I also found some fin damage after the final flight that I attribute to the whipping of the snap swivel based on the manner in which I had installed it. It is all easy fixing.

A video of the fourth flight can be seen here/

Recovery:
A Word of Warning: I did not set up my recovery system as provided by the instruction. Instead of using the nice chute that was sent, I used a streamer. It worked fine but generated its own issues attributable only to me, NOT First Flight Hobbies.

Flight Rating: 4 out of 5

Summary:
I took a closer look at the damage from the first outing. The most noticeable thing was the dents in one of the fins where the snap swivel struck after the last ejection. Somehow, I don't know how, the launch lug was also damaged. The last real noticeable bit was the "Estes smile" on the NC and a similar issue at the top of the BT.

The first step on the road to recovery was to fill in the holes. With that in mind, some Elmer's filler was applied to the nicks, dings and gouges. The goop on the fins was sanded down smooth. The restored profile was not perfect but it was satisfactory to me. In order to strengthen the filler and help it to hold up under flight, some thin CA was drizzled on and allowed to soak in to harden it. The filler on the nosecone too was sanded smooth but no CA was added here since the filler was within the wood instead of forming a new edge like on the fins. While sanding the NC, I found another dent in the cone. The newly found dent got a layer of goop and was given a day to dry.

A combination of tape and aluminum foil was used to mask the lavender area above the lower fins. The only goal was to completely mask the lavender, not to reproduce the original borders. The masked rocket was taken to the booth and sprayed with the same red paint used originally. It took 3 coats to cover the filler. Meanwhile, the nosecone was detached from the shock cord, put on a painting tube and sprayed as well. It only took 2 coats.

I cut the old lug off with a razor knife leaving in tact the part that had been glued to the body. A new lug was glued into the same place with white glue. Titebond Trim and Molding Glue was used to apply a fillet to the launch lug. I had not used this product before and gave it a try because I was told how well it worked for fillets. Its stiff and does not leave holes as it dries. It did very well.

I thought the kit needed a longer shock cord and the manufacturer agreed. Instead of replacing mine, though, I just tied in another length of sewing elastic. Mine is now longer than needed but I like the look of a long recovery train as it comes down. First Flight is now providing longer cords.

The last step was to touch up the lavender paint. The trailing edge of one of the forward fins needed some and then there were a few other places such as the new lug and the forward end of the BT. I sprayed some of the original lavender paint into a paper bowl and then used a brush to apply it where needed. The paint was allowed to dry for a few hours and, with that, the repairs are complete and the Semi-Sonic is ready to take to the air again.

For its first post repair flight, I loaded a Quest A6-4. The Semi-Sonic was to be the first launch of the day at the Alamo Rocketeers September 09 launch. As before, it performed well on lift off. It flew straight. It ejected on schedule and returned to earth under its streamer without any harm at all. The added length of shock cord made all the difference.

A video of the post overhaul flight can be seen here.

All in all, I am well satisfied with this rocket. The issues I identified during the build were promptly addressed by First Flight and changes are to be incorporated into the production model. The production model is supposed to included a decal as well.

Persons wishing to see what happens with this rocket can find it all documented here: http://www.flickr.com/photos/23694991@N03/collections/72157622523644403/

Overall Rating: 4 out of 5

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