Model Rocket Building Blog
Semroc Sam 3 BackgroundAll the copy below is from the Semroc website. "The Centuri Russian SAM-3 was first advertised in the Centuri 1878 catalog with an availability date of May 15, 1978. It was one of the four models in the new Strike Force line. It was loosely based on the actual Russian SA-3 surface-to-air missile ...[Read More]
Semroc Sam 3 Build, Part 1, PartsAll parts were good, Centuri thick ST tubing. This model has a Dr. Seuss decor with a Green Eggs and Ham, "Sam I Am" decal. Lots of small 3/32" balsa pieces! The original Centuri kit had basswood tunnels. In this kit they are cut on the balsa sheet. A washer weight is included for better ...[Read More]
Semroc Sam 3 Build, Part 2, Parts Prep Before Building The KitThe upper fin tip pieces felt weak to me in the kit supplied balsa. The burnt edges were lightly sanded clean. Four new pieces were cut from basswood using the balsa piece as a template. I used a single edge razor blade to cut out the new fin tips. On the left is the initial cut. On the right is ...[Read More]
Semroc Sam 3 Build, Part 3, Engine MountThe engine hook slot was a small punch made with an X-Acto knife tip. Rather than just punching the engine hook through the tube, I enlarged the slot and cleaned it up. This is typical of some Centuri engine mounts from the late 1970s. The lower ST-7 tube is 3" long. No engine block, a coupler ...[Read More]
Semroc Sam 3 Build, Part 4, Small Forward FinsThe small, upper fins are made up of three pieces. I cut new forward strakes from basswood, the large middle piece is the kit supplied 3/32" balsa, the upper antenna was also cut from basswood. The older Centuri instructions have you glue the individual pieces together on the model. The new ...[Read More]
Semroc Sam 3 Build, Part 5, Joining The TubesThe upper centering ring goes right over the the tubes joint. The lower ring is glued 1/4" up from the low end.A bead of glue is set around the upper ring and more glue is applied the outside bottom edge. Slide the lower tube on until the upper ring is even with the top of the tube. A glue fillet ...[Read More]
Semroc Sam 3 Build, Part 6, Fins!The small nose cone canard fins were cut from basswood. I made a few extras and will pick the best four. The launch lug seams were filled before gluing on the model. Along with the nose cone canards, there are many pieces to fill! For reference, the small fins at the top should be shown in the ...[Read More]
Semroc Sam 3 Build, Part 7, Fin Gluing and AlignmentThe large, square rear fins are glued on even with the end of the body tube. Before gluing on the upper fins, the body tube edge got a quick wipe with CA glue. The edge was a bit rough. With the CA glue on it could be sanded smooth. The upper fins were aligned with the help of clothes pins. ...[Read More]
Semroc Sam 3 Build, Part 8, Launch Lug, Tunnels & DecalsThe launch lug is glued into the root edge of a lower fin, even with the front of the fin. Tunnels are glued on opposite sides between two fins. Four tiny fins are glued onto the base of the nose cone in line with the lower fins. Here's where we are at. Now to figure out a paint scheme. The ...[Read More]
Semroc Sam 3 Build, Part 9, Paint PlanI did some searching and found a few pictures of the Russian Sam-3. It's always interesting to see an actual missile and the design compromises made to produce a sport scale model. This looks to be the inspiration behind the Semroc kit paint scheme. This is a smaller model and masking will be a ...[Read More]
Semroc Sam 3 Build, Part 10, Kit Differences and DecalsThe old Centuri instructions have you glue the upper (3 piece) fin assembly with the rear edge 1/4" from the end of the ST-7 tube. The Semroc instructions have you glue the 3 piece upper fin assemblies 1/8" above the exposed end of the upper tube. That throws things off when you go to redraw some ...[Read More]
Semroc Sam 3 Build, Part 11, The Mask . . .This was going to be a difficult mask, I never should have attempted it! On the left is just the Scotch tape mask. The rounded root edges required a few pieces to get the tight arc. I also knock off just the sharp corners on the squared edges. Regular masking tape is used to mask out the middles. ...[Read More]
Semroc Sam 3 Build, Part 12, Touch-up and Red PaintI sprayed some of the Winter Gray into a small mixing cup and touched up the bad mask lift with a clean brush. Certainly not perfect. I had a feeling this mask was not going to work out. I did something different on this model. With the launch lug glued into the fin/tube joint you never know where ...[Read More]
Semroc Sam 3 Build, Decals and FinishedThis Centuri designed "Strike Force" missile is sport scale at best. When you compare the model to the actual missile pictures there are major compromises. I learned a few things - On a smaller model with too many close fins - don't bother masking! You'll spend too much time cleaning it all up. I ...[Read More]
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