Centuri Astro 1, Second Build, Finished

I'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 interesting, a three fin rocket with four black vertical bands around the tube. That's why the long orange strip is offset, just like in the catalog.

Centuri Astro 1, Second Build, Fix Mask, Part 2

For 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 as opaque as silk screened decals.
The clear areas were pretty wrinkled. This did go away after the decals dried.

I peeled off the decal and went back to my old standby, the Contact Paper Blackboard Covering.
Strips were cut and lined up using a paper strip folded in quarters.

The orange stripes were cut from Trim Monokote.
Both these materials are very opaque. When correctly cut you get very high contrast colors.

That one bad masked root edge was re-trimmed with a leftover strip of printed black decal. After it dried some Future Acrylic was rolled on with a Q-tip.

The black Contact covering material is a flat finish. To gloss it up a bit, more Future was applied with a Q-tip to shine it up.

Centuri Astro 1, Second Build, Fix Mask, Part 1

A 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 down.
In the picture I'm burnishing down the tape lines with a Q-tip. Using the Q-tip is softer than using a fingernail.

This time the masks came up clean and sharp, except for one edge. Still, a big improvement over what I had before.

I had some hints of black paint above the tops of the fins.
I used a damp magic eraser sponge to remove them.
The inset picture is after cleaning off the black.







I carefully scraped the white paint off the engine mount hook. This isn't necessary but that paint would probably bubble up and flake off anyway being so close to the engine flame.

Centuri Astro 1, Finished

This 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.

Centuri Astro 1, Build, Part 13, Wrap Top Trim

There 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 nose cone / body tube joint, a Sharpie was used to blacked the body tube edge at the black decal band tops.









I don't know what happened here -
There must have been some oil on the primered nose cone.
The black paint didn't stick and pulled up near the shoulder.

Let it dry, sand smooth, primer and re-shoot the black.

Centuri Astro 1, Build, Part 12, Decal Wrap Fix

This 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 won't see the vertical bar that was trimmed.

I used my aluminum angle to cut through the decal overlap.

The cut was made before the decal was totally dry and still flexible.
Use a new razor blade. a dull blade could flake the decal ink.

On the left the overlap is peeled off.
On the right is the trimmed decal with matched corners.
Sure, it's not perfect, one of the vertical bands is narrower than the others but it looks better than the overlap did.

Centuri Astro 1, Build, Part 11, Fin Border Trim, Second Try

I 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 the center.





The center hole half was set over the rounded leading edge of the fin.

Leave the sides long so you have something to hold onto while setting the lines down the root edge

On the left is 1972 catalog page showing the Astro I.

The black fin border I did looks thicker than the ones in the catalog. After the previous decal try, the thicker lines are okay by me.

Centuri Astro 1, Build, Part 10, Fin Border Decals, First Try

The 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 lines were cut down the middle and to the sides of the punched circle.
Decals tend to be a bit brittle and the punched holes weren't that sharp.

Here's how the decal fits over the fin and down onto the body tube.
This is a dry fit before soaking and transferring the decal.

I could see this coming.
After the thin strips were flexed and pressed into position, the decal edges broke off.
I'll have to try something else.

Centuri Astro 1, Build, Part 9, Fillets

After 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.

Many builders forget about the front leading edge tip of the fin.

Roll some glue around the tip joint and smooth with a fingertip.



The back end root edge joint also needs some extra glue set into the seam. You can use a Q-tip to pick up the excess if it is too hard to reach.

Check out the tube wall thickness of the ST-10 and ST-7 tubes. SO MUCH STRONGER than the Estes BT-50 and BT-20 tubes.

Centuri Astro 1, Build, Part 8, Fin Gluing

The 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 line of glue, run your fingertip down the edge at an angle removing some of the glue and evening out the glue bead.
This makes for a cleaner glue joint with less glue to remove when the fin is pressed onto the body tube.





After the first fin was glued on a straight paper strip was taped and slid down to the top corner of the fin.

The other fins were glued on just touching the paper strip. Also check the rear of the model to be sure the trailing edge is even with the end of the body tube.

Centuri Astro 1, Build, Part 7, Semroc Parachute

The 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 sheet.

Avoid touching the sticky side of the reinforcement disks.
Use some long tweezers and set the line through the sticky back side before setting the disk onto the chute. Orient the shroud lines as shown for an easier tie.
The picture here shows the disk flipped over after the shroud line was stuck down on the back side.

Tie a square knot after the disk (with line attached) is stuck to the parachute.









You can cut the excess line off with scissors or knife.
I usually use a small wire cutter. It leaves a clean cut with no frayed edges.

Centuri Astro 1, Build, Part 6, Fin Primer and Decals

The 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 want, but a wrap around decal never seems to match up on the first try.
It is easy to go back into the drawing and shorten up the width of the wrap.

On the left is the orange and black roll pattern from the 1969 catalog.
On the right is the black pattern from the 1972 catalog.

The black stripes were meant for the fin root edges. The orange stripes run down the body between the fins on the 1969 catalog model.

Here's a comparison picture, taken a little farther on in the build.

This shows the size comparison between the Centuri Astro I and the Estes Alpha.
The Astro I is a much taller, more elegant model. The ST-10 tubing is around the same diameter as a BT-50 but the tubes walls are thicker. The longer body tube on the Astro I makes for a more stable model and some extra room for parachute and wadding.
As a first time build, I'd prefer the Centuri design over the Estes Alpha.

Centuri Astro 1, Build, Part 5, Basics - Rounding Fin Sides

Once 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 sandpaper and not using a block.
There is nothing wrong with the finished shape, the rocket will fly just fine. This post could help you keep those corners sharp and rakish.

As I've said before, this is how I do it. Everyone has their own techniques that work great for them.




Initially I knock the edges with a sanding block. This is a well worn piece of 220 grit on my Great Planes Easy Sander Block.
The block helps keep the sides straight and square.
Simply rolling sandpaper over your fingertips works but doesn't keep the sanded edges square and flat.

You don't have to get a complete "half round" fin edge using just the first passes of the sanding block. Just knock off the corners. Use light pressure.

Come back with the finer grade 400 grit, now with the sandpaper rolled over your (cushioned) fingertips. Hold the fin edge under a bright light to see if there are any sharp edges remaining. Sand lightly with the 400 grit.
Go easy on the corners, keep them sharp.
It's better to take off a little at a time instead of taking off too much balsa that you can't replace.





The Astro I has a round trailing fin tip. On a rounded surface use sandpaper over your fingertips.

Centuri Astro 1, Build, Part 4, Nose Cone and Fin Prep

Take 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 is going in straight. If you catch a crooked insertion early you can correct it before turning it in all the way.

TIP: The nose cone is a over 5" long and very pointy. In past experience, pointed balsa nose cones seem to get hit and blunted.
I'm building two kits as once.
The nose cone on the left is the before, on the right is the second cone rounded off. The later Centuri Astro I kits had plastic nose cones with rounded tips.

TIP: The balsa fin stock was slightly different between the two kits.
To match the density and grain the fins were grouped and marked on the root edges.

With this unusual fin shape it's easy to round the root edges by mistake. That was a problem with the Asto I fins. Many first time builders glued them on wrong, looking more like the Estes Alpha. I found myself almost rounding the wrong (leading) edges.
Marking the root edge tips made me stop, reposition and sand the correct sides.

Centuri Astro 1, Build, Part 3, Engine Mount

Here'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 finished engine mount, pretty standard.