Model Rocket Building Blog
Centuri Finless Build Part 1 PartsThe plans are from the Centuri American Rocketeer magazine, Volume 4, Number 1. The plans are on page 15. Go to: oldrocketplans.com HERE Parts are available from Semroc: 1 ST-718 18" Long ST-7 Body Tube 1 TR-7 Engine Block 1 BTC-7 Balsa Nose Block or Coupler 1 BC-736 Nose Cone Conical, 3.6" long 1 ...[Read More]
Centuri Finless Part 2 Parts PrepThe ST-718 tube was cut 4 1/2" from the top for a payload section using my Odd'l Rockets CUTTER tool. This upper section will also hold the clay nose weight. A nose block was made for the payload section from a 7 tube coupler and the shoulder from a old, unusable nose cone. I just kept sanding ...[Read More]
Centuri Finless Build Part 3 Centering Ring HolesThe engine hook notch and launch lug hole will be on opposite sides of the body tube. Draw a pencil center line across the centering ring. Using a rotary punch, set it on the largest hole or 3/16" diameter. TIP: A 3/16" hole will fit a 1/8" launch lug perfectly. I also used the rotary punch to ...[Read More]
Centuri Finless Build Part 4 Engine Block and KevlarThe engine block (or thrust ring) was notched for the Kevlar. I've been using a small diamond file with good results. After tying on the Kevlar, the block ring was glued into the rear of the ST-7 tube. An engine casing was marked 1/8" from the end. The Kevlar was fed through the casing so it'd be ...[Read More]
Centuri Finless Build Part 5 Hook RetainerHere's how the split 1/4" long piece of BT-20 will hold down the engine clip. Before gluing the split ring, a piece of masking tape was set on the lock after making sure it was in line, straight down the tube. Enlarge the picture and you'll see the tape has fine blue fibers stuck to it. I reduced ...[Read More]
Centuri Finless Build Part 6 Shroud PrepThe shroud was printed up using the Transition Tool from the Payload Bay website HERE : Print up the shroud cone on 110 lb. cardstock. Tube 1 size is an ST-7 at .759" Tube 2 size to fit the centering ring is 2.08" Length is 3" (The original adapter fits a ST-20 tube which was 2.04" diameter. I ...[Read More]
Centuri Finless Build Part 7 Shroud CementPre-roll the shroud before cementing together. I learned a valuable tip from the Apogee website about using rubber cement instead of white glue when gluing a shroud tab. Lay a coat of rubber cement on 1/2 of the length of the tab. Stick the tab under the long edge of the shroud. Apply more rubber ...[Read More]
Centuri Finless Build Part 8 Lug SlotThe shroud was dry fitted down the tube and over the centering ring. A (longer than needed) 5" launch lug was pushed in from the rear lug hole until it hit the inside of the shroud seam. A pencil mark was made where the lug raised the shroud from the inside. This is where the lug slot will be ...[Read More]
Centuri Finless Build Part 9 Lug SlotThis is the first try at the lug hole in the shroud. The shroud sides are still raised too high from the pressure of the lug underneath. I'll make the slot longer by punching another hole a little farther back. In the end the punched hole was 11/16" back from the smaller front of the shroud. ...[Read More]
Centuri Finless Build Part 10 Shroud GluingThe original Centuri instruction plan has you glue the ring into the shroud then install it on the body tube. Because of the retaining ring, you'd be better off gluing the ring on first. Then, slide the shroud down the tube from the top and onto the ring. If you were to glue the ring and shroud ...[Read More]
Centuri Finless Build Part 11 Fill and Finish PrepEven after the first primer coats, I was still trying to fill the lug / shroud gap with white glue fillets. It took a few applications to smooth it over. The nose cone was brushed with thinned CWF and sanded smooth. Some CWF was over the edge of the nose cone shoulder. TIP: To get a better edge on ...[Read More]
Centuri Finless Build Part 12 Shroud Paint and TrimI applied some medium CA around the lip of the shroud to strengthen it a bit. Here's the shroud after the white undercoats. To do the stripes and roll patterns, there won't be any hard masking. All the trim will be done with Contact Paper, almost the same stuff my Mother used to line her kitchen ...[Read More]
Centuri Finless Build Part 13 Black Shroud TrimI had printed an extra shroud on some 20 lb. paper to make a template for cutting the Contact paper trim. The shroud sides were extended up to their center point. A compass was used to draw the horizontal lines. The vertical lines were simply extended from the center point. The sides of the ...[Read More]
Centuri Finless Build Part 14 Black Shroud TrimThe white areas were cut away from the template. While cutting away the template, I tried to cut through just the top black layer of the Contact paper. Be careful cutting the inside corners, you don't want the vinyl to tear when placing the trim. The paper template was removed. The open "white" ...[Read More]
Centuri Finless Build Part 15 Upper Black TrimThe upper trim roll patterns were strips of the black Contact vinyl. These were rolled around the body tube using the Centuri instructional drawing as a rough guide. Use a sharp knife and straightedge to cut the stripes and rolls. Position the black vinyl using a clean knife blade, not your ...[Read More]
Centuri Finless Build Part 16 More TrimThis is how the model looked using the Centuri instructional drawing. I liked the looks of it, but it needs a third trim color. Time to find the aluminum Monokote Trim sheet. More detail was added by using my rotary punch again. I punched some 3/16" diameter dots and placed them at random. The ...[Read More]
Centuri Finless Build Part 17 Nose WeightTo balance with the trim colors, the nose cone was spray painted aluminum. The instructions call for .40 oz. of clay weight to be added to the payload section. Clay was weighed and pressed it into the upper payload section. The upper section isn't used as a payload, so the nose cone was glued in ...[Read More]
Centuri Finless Finished!I like the finished look, the aluminum trim helps set it off. Lessons learned: I didn't get as good a seam fill as I'd hoped. I tried a new smaller can of Dupli-Color Perfect Match Scratch Filler Primer after my larger can ran out. The larger can is a different formulation and filled the seams on ...[Read More]
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