New BT-20 Sized DECALS for Patreon Supporters!

I'm pretty excited about this one - 
These are generic roll patterns to be applied around standard BT-20 tubes. Below the roll patterns are many pieces of "spot" art to decorate your rockets.
Some of the roll patterns are based on the old Centuri sport model decals. You'd sometimes find one packed in the kit bag.

TIP: Home print decals are not a full opaque print like you'd find in an Estes kit. The Estes decals are printed "old school", by silk screen. Placing a home print black decal over gloss white paint will end up a very dark gray, not a full black. I have used doubled decals (setting a second print over the first) for best results. If you set a black ink jet decal over other colors (even yellow) it will look a more dense black.

Have you ever had a kit supplied roll pattern decal that didn't quite match up after you rolled it around the body tube?

All these patterns have been tested for size on a standard painted BT-20 tube. The picture on the left shows one test. See if you can find the two side edges of the decal wrap. (It's right in front!)
These decal drawings took a while to draw up. After the first print, I ended up going through two more decal sheets adjusting the widths through test fits. Each sheet got three coats of gloss clear acrylic. Between each new print, micro size adjustments were made for a (near) perfect fit!


If you are a Patreon member supporter, I can email this PDF to print your own decals!
Email me at oddlrockets@bellsouth.net and ask for the BT-20 Decal PDF.
More Decal PDFs are on the way in BT-50 and BT-55 sizes!

NOTE: These are home print decals for you to print at home. I don't print up custom decals or send them out through the mail.

Semroc Micro Mars Lander, KMX-02, Part 4, Main Nozzle Forming

This is the two leg alignment tool pieces.

To the left is the engine mount depth guide and the nozzle pieces.








The other side is a bit smoky but this doesn't effect the build.

The instructions say to glue the three nozzle rings to the motor mount tube. I thought it might be easier to shape the sides of the nozzle lamination off the tube.
TIP: The rings were stacked and three pieces glued together, but not yet glued to the tube. The tube was only used for alignment. After the glue on the rings dried, they were slid off the tube.



The burnt laser cut sides let you see how deep you are sanding. You might think you are done looking at the left, but try to sand off most all the brown which should remove the step lines.

Minimum Diameter Build Comments

From TRF, a post from Senior Space Cadet.

His statements are in italic, my responses follow.

"By minimum diameter rocket I mean a rocket with a body tube the same size as the motor, such as an 18mm body tube with an 18mm motor.

My first suggestion, if you are considering it is, don't.  Your mother raised you better than that.

I'm nearing completion of my first one and I wish I hadn't gone down this road."

"I never built one before because the normal way of keeping the motor from flying out the back, when the ejection charge goes off, is to tape it in.  Seemed like a poor solution.  Still does."

Friction fit was never 100% reliable. Before masking tape was used, the oldest Model Missiles instructions suggested using rubber bands wrapped around the motor. It's like anything else, you learn through experience the proper amount of wraps before you end up crimping the body tube when pushing in the motor.

"In designing the rocket, you need to leave room for the tape, so you have to move the fins forward."  

As mentioned above, you only need about 1/4" clearance for the tape wrap around the body tube and extended engine.

"Then you have to move the motor back so you have enough surface for the tape to grip onto.  This moves the CG back.

Because you are using a smaller body tube and nose cone, which weigh less, you either have to use a longer body tube or add weight to the nose cone, which negates most of the advantages of using a minimum diameter in the first place."

The body doesn't have to be that long - Look back at classic models like the Estes Sky Hook. That model does have long, trailing fins that can get in the way of removing a friction fit engine.

"Then there is the problem of anchoring the shock chord.  Some glue it on the outside of the body.  Some use the old method of using a folded up piece of paper, but now you don't have room to get your finger in the body tube."  

Estes style Tri-Fold shock cord mounts aren't good in models smaller than a BT-50 anyway. Too small a tube and the chute or streamer ejection can be blocked by a thick, folded mount.

"Well, maybe a child or small woman could.  I wear XL gloves.  My solution was to tie a big knot on the end of some Kevlar chord and glue it under an engine block.  Seems pretty secure, but Murphy will have the last say."

Kevlar tied around the engine block is probably the best way to go in a small diameter model.

"I took some short cuts and made some mistakes in designing my rocket.  The result is, I had to put a bag of concrete in the nose cone."

I was going to use streamers, but with the weight in the nose cone, I'm thinking I better use a parachute, which now means I probably have more weight in the nose cone than I need.

We've all made design mistakes in our first scratch builds. A "Bag of concrete?" Even the old Estes Wac Corporal used two nose weights coming out to about 1/4 oz. How much weight did you use?

"Other than all that, it's going to be brilliant.  They will be talking about my fins, in reverent tones, for years to come.  It will be a thing of near beauty.  Well, I'm pretty sure you won't gag. I might have photos in 24 hours, or less, or I might wait till launch day, which might be a while."

You've got the right attitude about it being "Brilliant". Looking forward to seeing the pictures.

Semroc Micro Mars Lander, KMX-02, Part 3, Nose Cone & Tube Prep

The nose cone is probably the cleanest 3D part I have seen in a kit. There is still some ridges but they are small. At the bottom shoulder ridge there are some "nubs".





Using a sanding block with 400 grit, the nubs are sanded smooth.

As mentioned above, there is some layer ridges. The outside surface of the nose cone was sanded a bit, the remaining ridges will be filled with some sanded paint undercoats.

The engine mount and stuffer tube ends were laser cut. The ends were a little uneven. The ends were squared up with a sanding block.

Semroc Micro Mars Lander, KMX-02, Part 2, Leg (Fin) Prep

The lander legs are cut clean on some 1/32" thick basswood.

Before removing the legs from the sheet, the strut holes were cleaned up using a small rat tail file. Just a light twist to smooth out the laser cut holes. I found out later this wasn't needed, so skip what I did here.

On the Semroc MMX Orbital Transport, I used only one coat of filler/primer. Those fins were basswood and I thought that would be adequate as there is very little grain to fill. I wish I had used two coats, there was still some grain showing through on the O.T. after painting.

The leg pieces were left on the sheet for spraying and sanding. I wouldn't normally leave them on the sheet for a filler coat, but these pieces are small and a little fragile. The picture on the left shows the lower right quarter of the sheet after sanding down the filler/primer with 400 grit. On the right is the center piece that glues between the leg support pieces - these are very small.
TIP: Keep all the small parts in a zip lock bag after they are removed from the laser cut sheet. These can be easily dropped and lost.

This shows the filler/primer left in the basswood grain after sanding.

Go light when sanding, I did break one of the thin upper areas when fitting the legs.

The edges do have some laser burn "chatter". Sand smooth but not enough to change the shape. Be very careful if you decide to sand around the thin upper rod near the "control cylinder".

Semroc Micro Mars Lander, KMX-02, Part 1, Parts

In the past I've built the full size Estes and Semroc Mars Lander (Sorry, not on this blog) and the Estes Mini Mars Lander: CLICK HERE.
Now things are going to get even smaller -
This looked like a challenge and I have plenty of MicroMaxx motors to fly it with.

Here's the front and back of the package.

The largest square white pieces are the Leg Alignment Tools, at the bottom of that piece is the engine mount depth gauge and the three nozzle laminate rings.

The parts of interest, clockwise from the upper left:
Printed card stock trim pieces.
Strut support pieces (laser cut thin card stock)
3D printed nose cone
Nozzle base disk (1/8" thick balsa)
Lander Legs (1/32" thick basswood)
Center - Antenna disks (basswood)

Other UFO Saucers

In addition to the Centuri Alien Encounter Flying Saucer,
here's more of the kitted Saucers!
I know there have been others, these are probably the better known LPR models.

Semroc JUPITER B
http://www.erockets.biz/semroc-flying-model-rocket-kit-jupiter-b-kn-06/

Art Applewhite FREEBIES!
http://www.artapplewhite.com/free/index.html

Quest RTF AREA 51: 1999 - OOP (Out Of Production)
http://archive.rocketreviews.com/reviews/all/quest_area_51_spev_ufo.shtml

Quest MMX FLYING SAUCER 1999 - OOP
http://archive.rocketreviews.com/reviews/all/oop_qst_mm_alien_ufo.shtml

Estes FLYING SAUCER  1985-1987 - #1947 OOP
Instructions:
https://estesrockets.com/wp-content/uploads/Instructions/001947_FLYING_SAUCER.pdf

Estes SNITCH 1998-2004, 2007-2008 - #1807 OOP
https://www.rocketreviews.com/estes-snitch-rtf-bob-hvarven-3095.html

FLISKITS TRIPLE THREAT - OOP
https://modelrocketbuilding.blogspot.com/search/label/Triple%20Threat



Fliskits FEORD X150 - OOP
http://modelrocketbuilding.blogspot.com/search/label/Pheord%20X150

Is it a Flying Saucer?
Estes QUINSTAR
https://estesrockets.com/product/007241-quinstar/

SPOOLS - Close to saucers!
SQUIRREL WORKS
http://squirrel-works.com/oddroc.html

Not a saucer, but has saucers on it - 
MPC MARTIAN PATROL - OOP
https://modelrocketbuilding.blogspot.com/search/label/Martian%20Patrol

In a comment Bernard Cawley reminded me of two more:
The Fliskits Frick-n-Frack a two-stage saucer. 
https://www.fliskits.com/WPRESS/product/frick-n-frack/
The three-stage 13mm motor FlisKits Trifecta: 
https://www.fliskits.com/WPRESS/product/trifecta/

Ed Mitton reminded me of another:
Estes INVADER!
http://spacemodeling.org/jimz/estes/k-19.pdf
Be careful with this one - they are known to loop and prang!

Centuri Flying Saucer #5325, Fix and Finished!

Remember the clear coat made the motor tube wrap a bit transparent? The brown tube underneath was showing through.

This was probably the weirdest mask I've ever done. The interior core tube was masked off with many pieces of masking tape. The tape wasn't pressed in place, I didn't want to tear or peel up the card stock.
The Main shroud was covered with cut copy paper.

I carefully aimed the gloss white paint to hit the center motor tube and C and L supports.
Finally, much better. Not perfect -  but better. I can sleep tonight.

It's already loaded with a C6-0 motor for a upcoming schoolyard launch.

A Comment and Answer From "Fill & Finish" Posts

Openroad commented:
I’ve had decent results with Rusto High Build Primer/Filler, #249279 version - the label looks like a riveted on plate - but the Duplicolor definitely sands easier. The extra solids in high build primer is a big help in getting things smooth. You use much finer sandpaper than I have the patience for, which is why your rockets look that much better than mine! Thanks for the step by step Chris, helpful stuff.

My response:
Hi Openroad,
Regarding sandpaper grits - The new (colored sheet, blue and purple) sandpapers are better than the old black sheets. The new stuff doesn't load up as quickly and will last longer. But, the new 400 grit seems rougher and can leave scratches that can show up after color coats are sprayed. I'm starting to final sand with 800 grit before spraying paint.

Centuri Flying Saucer #5325, Part 12, Glow In The Dark Dots

Here's a case of a single guy with too much time on his hands. I'm going to add the glow in the dark dot "lights". These were a special added feature of the Centuri kit.

From the instructions:
"SPACE GLOW DECALS" There are over 70 of these round dots, more than enough to decorate your model. One goes into every round embossed area on the main shroud and around the core tube. These dots, printed with a special ink are phosphorescent. This means they soak up available light and then glow in the dark."

Using a Michael's 40% off coupon I bought a can of Krylon "Glowz In The Dark" paint for $4.80.

Half of a peel and stick self adhesive page was sprayed with the glow paint.
A simple 1/4" punch was used to knock out many small dots.

TIP: If your dots aren't cutting clean, flip over the sheet and punch with the backing side facing up.

Place the dots using the tip of your knife blade and lightly burnish.






With my pantry door shut and the lights off - Here's the saucer with glowing dots. There is also some glow dots in the center core.
Rocket Nerd SUCCESS!
No . . . this wouldn't make the saucer more visible at a night launch.

Centuri Flying Saucer #5325, Part 11, Finished?

This was fun, and a good challenge getting everything to fit!

This smaller 75% size makes it more manageable and will get a better altitude with C6-0 and C5 engines.

The only thing different is the engine mount tube sticks out the top. I could have had it extend out the bottom, but it might be more stable with the engine weight forward.

As with all home print models, you do need to clear coat the water soluble printer inks. If the model lands on wet dewy grass, the home print inks will run.
When I sprayed the copy paper wrap around the engine mount tube - it turned a bit transparent! The brown tube was showing through the white wrap. The glued areas stayed white.

It wouldn't matter to some, but it bothered me. We'll fix it in an upcoming post.

Shroud Line Hole Punch TIP

When assembling parachutes, you are instructed to punch a hole through the reinforcement ring and the plastic chute material. A sharpened pencil is usually suggested. A pencil point can tear and stretch the parachute plastic.

I use the smallest punch on my rotary punch.
Notice there is some card stock underneath the plastic sheet to make an easier, clean punch.

TIP: Instead of punching the whole in the center of the disk, I set the hole to the outside edge. This puts the line strain against the reinforcement disk preventing stretching and tearing of the chute plastic.

Centuri Flying Saucer #5325, Part 10, Trim Pieces & L Brace Gluing

The fit of the minor shroud was very good. It covers the cogs on the inside of the large ring.

The three L braces also needed some trimming on the outside edge to fit between the core tube and engine mount tube.

It's difficult to get the l braces in place without making a glue mess - try gluing the outside edge first - then glue the root edge to the motor mount tube, explained below:

The outside edge of the L brace is glued to the interior ring first (one side) and allowed to dry. This makes a glue "hinge" to swing the root edge away from the motor tube pencil line.
On the left you can see the faint pencil gluing line. The picture on the right are some small glue dots. Notice the root edge of the L piece is turned away (hinged) from the glue. After the glue dots are applied to the pencil line, swing the L brace and slide it into the glue. Wipe off excess glue and glue fillet both sides of the joint later.

The bottom detail strips were placed using a glue stick.




These fit along the bottom edge of the core tube.
The hatch is centered in the gap between the cutouts. It was also too tall and needed trimming to fit.

Centuri Flying Saucer #5325, Part 9, Gluing It All Together

Instead of putting a line of glue down the outside edges of the C braces, I applied some small glue dots on the inside of the core tube using a sharpened dowel.

The outside of the C braces were turned into the glue dots and the excess wiped clean with a Q-tip.

Here's where we're at -
Now onto the large ring at the bottom.









The inside "cogs" were also too tight, against the core tube distorting the shape.

This took some tight trimming, cutting off slivers from each of the interior glue points.



With the large ring in place, the outside overhangs the main shroud a little under 1/16"
I glued and inch and taped on either side of the glue area trying to keep the overhang even all the way around.



With the ring glued all the way around, a fine fillet was applied and smoothed with a fingertip.

There were some uneven areas. These were evened up with 220 grit on a sanding block followed with 400 grit.

Centuri Flying Saucer #5325, Part 8, Oops! Re-Fit Again

Even after the first trim of the C braces, the fit was too tight, still  distorting the roundness of the core tube.

The side of the C braces had to be trimmed even more! I had enough disappointment for the night.





I waited a day or two before removing the card stock wire form retainers and then trimming the outside of the C braces again.

This made for about 1/16" total trimmed off with this second adjustment.





Here's how I fit the new retainer strips. The ends were cut on an angle to match up in the corner.
On the available PDF, the wire form retainers have been reduced to fit this smaller model. The PDF doesn't have all the shroud pieces, just the 75% reduced antennas and retainer stripes. The shroud prints are listed on YORF - CLICK HERE and look for post #21.







After the wires and retainers were in place, the outside edge was flattened with a burnisher.
Flattening the outside edge gave me a slightly wider gluing area.

Old Picture & Centering Ring

Going through a box, I came across these two relics.

On the left is a Estes 20/60 centering ring, probably from the mid 1970s, Die-cut from card stock, thinner than what you find in a kit today.

That's a Centuri Saturn 1B with a two engine cluster, probably B6-4s. The shot is blurry, but you can't expect much from a Kodak Instamatic camera. I was lucky to get anything!

Centuri Flying Saucer #5325, Part 7, First Fit of the C Braces

TIP: You can get a rounded leading and trailing edges on carded fins by applying a glue bead down the edge. Apply a fine line of glue, then run your finger down both sides of the fin to even out the glue bead. Let dry and sand lightly with 400 grit.

This glue bead will also strengthen and seal the edges of the fins.

I tried to slide the engine mount assembly into the center core. The fit was too tight!
With the addition of the wire thickness the span was now too wide! I trimmed off about 1/32" from the outside edge of the C brace.

I later learned this wasn't enough! You'll have to trim off almost 1/16" for the proper fit.
I'll continue with the build to show what happened - but be aware, on my build it required some extra fitting and time.

I made some "Wire Form Retainers" from 110 lb. card stock. These were just strips of card stock about 3/8" wide.

On the left it looks like a simple fold. The center is actually a double fold, to roll over the wire antenna positioned in the center.

I drew up some Wire Form Retainers along with an Antenna Template. This PDF is available to Patreon supporters. Email me at oddlrockets@bellsouth.net and ask for the Centuri Flying Saucer PDF.
Note: I do not have all the templates, just the 75% size antenna and the antenna retainers. All other PDFs for the main body parts are listed in the first Background Post: CLICK HERE


Here's how the antennas fit -
And the retainer strips over that. That angle joint at the upper right is cut and fitted.

When first gluing on the antennas (left picture), don't use much glue. They hold better when the glue is about half dry and tacky.

Centuri Flying Saucer #5325, Part 6, Engine Mount & Large Shroud Gluing

The engine hook is removed and the low end of the tube is set on the marking guide

Notice the brace gluing positions aren't all the way down the tube. I set the braces against the tube and only marked the gluing areas. I wasn't planning to paint anything and didn't want pencil lines on the finished model.

After the tube was marked the engine hook was set in the slot. A card stock strip was glued on to hold the hook. Center the retention strip in the open middle area of the C brace positions.









I was surprised how well the round core tube fit into the main shroud. A perfect fit!




The old instructions say to make a "glue point" in four locations around the joint. It is very tight, you can't just drop in glue.

I used a sharpened dowel to set a small drop of glue in the wedge joint. The dowel tip was used to spread the small glue drop evenly. You should keep the glue amounts under control. Too much and the card stock could end up distorted after the glue dries and shrinks.

Four drops of glue are set and spread out at 90 degree intervals. Let these dry, then come back and fill in the rest of the gaps. You should end up with a small, even glue fillet all the way around the circle joint.