Model Rocket Building Blog
Centuri Astro 1 FinsThere was some questions raised the YORF forum about the Centuri / Semroc Astro 1 rocket. At the right is the Semroc Astron, a slight downsize of the Astro 1 and still uses 18mm engines. Carl from Semroc answered many questions about it's design and history. The Astro 1 fins were close to the ...[Read More]
Centuri Astro 1, Build, Part 1 Parts and ChoicesThis is actually the Semroc kit, #KV-30. I'll be finishing it in the Centuri catalog paint schemes. I've always wanted to build one, going back to 1969. Many builders turned the fin around to where it looks like the Estes Alpha. That wrong grain direction led to a lot of popped off fins! The inset ...[Read More]
Centuri Astro 1, Build, Part 2, Engine MountThe engine mount tube has a small slit obviously cut with an X-acto knife. It's a short "stab" cut, not quite wide enough for the end of the engine hook. Make a small cut from the other side, joining the other cut. Flip over the blade with the sharp edge facing up, connect the two cuts. The slot ...[Read More]
Centuri Astro 1, Build, Part 3, Engine MountHere's how the Semroc instructions show the Kevlar tie. An overhand loop knot slips under the bend in the engine hook. I didn't tie a knot in the Kevlar, but simply twisted it under the line 3 or 4 times. After the fillets were applied the Kevlar loop was pressed into the drying glue. Here's the ...[Read More]
Centuri Astro 1, Build, Part 4, Nose Cone and Fin PrepTake an extra moment before screwing in the screw eye. Mark the center with a pencil. Rotate the nose cone and chances are that first mark won't be perfectly centered. Mark the center again. TIP: When screwing in the screw eye, go slow. Screw a full turn, stop and check the alignment. Be sure it ...[Read More]
Centuri Astro 1, Build, Part 5, Basics - Rounding Fin SidesOnce in a while I'll do a basic rocketry technique, there are some new builders following the blog. On the left is an Alpha style fin with sharp corners. On the right is the same fin silhouette after a beginner has rounded the edges. The corners aren't as sharp after using too rough a ...[Read More]
Centuri Astro 1, Build, Part 6, Fin Primer and DecalsThe fins were set down on some sticky side up masking tape. The root edges are butted up against each other to keep the primer off an area that'll be glued. That's two sets of fins, I'm building two Astro I kits. I wasted a full sheet of decal paper. You can do all the measuring and planning you ...[Read More]
Centuri Astro 1, Build, Part 7, Semroc ParachuteThe print on the Semroc parachute sheet looks like the old Centuri chutes. The shroud line attachment is very different. If you were to tie the shroud line on before sticking down the disk, the adhesive on the disk would be covered with skin oils and dirt, diminishing it's hold on the plastic ...[Read More]
Centuri Astro 1, Build, Part 9, FilletsAfter the fins are glued in place with white glue, Titebond M&TG is used for the fillets. If you use the right amount of pressure and apply the right amount of glue, the fillet should be pretty even right out of the bottle. The inset picture show the glue fillet smoothed out using a fingertip. ...[Read More]
Centuri Astro 1, Build, Part 8, Fin GluingThe fin lines were drawn down the body tube with pencil. The primer was then sanded off with some old 220 grit on a block for a better gluing surface. I sanded down just to the white body tube. The pencil line was re-drawn. Look close at the glue on the root edge of the fin. TIP: After applying a ...[Read More]
Centuri Astro 1, Build, Part 10, Fin Border Decals, First TryThe 1972 Centuri Astro I catalog model had a black border line around the root edge of the fins. I tried a decal first. It wasn't successful. I printed up the decal at home and hit it with three coats of clear acrylic. A hole was punched to fit over the rounded leading edge of the fins. Straight ...[Read More]
Centuri Astro 1, Build, Part 11, Fin Border Trim, Second TryI went back to my old, standard trim material, the Contact Paper Blackboard Covering. It's stiffer and easier to place than a thin decal. Three strips were cut. The top of the hole position marked with pencil and holes were punched. A straight edge and knife were used to cut the fin "slot" out of ...[Read More]
Centuri Astro 1, Build, Part 12, Decal Wrap FixThis is the second decal wrap I printed and it was still too wide! I guess I shouldn't feel too bad, I've had a few kit wrap decals that overlapped. I applied the wrap so the seam is right above the launch lug. When the rocket is on the launcher (with the lug behind the tube for a picture) you ...[Read More]
Centuri Astro 1, Build, Part 13, Wrap Top TrimThere was a little clear edge that overlapped the top of the body tube. Another sharp razor blade was used to trim off the overhang. Wait until the decal is dry before doing a trim like this. The decal will just flop around if it is still wet and pliable. For a smoother color transition at the ...[Read More]
Centuri Astro 1, FinishedThis is the 1971 catalog Astro 1. I'm still working out some masking problems I had on the 1969 version. It's a sharp design, 4" taller than the Estes (equivalent) Alpha. This was the starter rocket kit for first timers.[Read More]
Centuri Astro 1, Second Build, Fix Mask, Part 1A while back I was building two Centuri Astro 1 models, one in the 1969 catalog motif, the other in the 1972 style. The 1972 model came out fine. I had some root edge masking problems with the 1969 build. I set that one aside for a few months. The root edges were sanded smooth and new tape was set ...[Read More]
Centuri Astro 1, Second Build, Fix Mask, Part 2For once the wrap around decal I drew up fit the circumference of the body tube! Too bad I couldn't use it. On the left was the dry fit to see if it was close. After doing the transfer to the body tube, the black was a bit translucent. That's one of the problems with home print decals, they aren't ...[Read More]
Centuri Astro 1, Second Build, FinishedI'm glad to have this one finished. While the decal is easier, the Monokote and Contact Paper trim look better. The long orange stripe looks wider than the catalog art making me think there may have been five black bar divisions in the roll pattern instead of the four I did. The roll pattern was ...[Read More]
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