Estes Cosmic Interceptor Build, Part 3, Prepping The Engine Vanes

Lightly sand the laser cut ash edges with 400 grit.

The pics show the before and after sanding.

The exposed edges (shown here marked with pencil) should be sealed. If not sealed, the paint will soak into the open fibers and the edges will be uneven.

A segment of tubing will glue over the edge without the pencil line. 

Run a narrow bead of glue down the side edges. 

With the side of your finger, even out the bead getting a rounded even coverage from side to side. Remove the glue from the sides of the vane, leaving only a rounded bead over the edge.

After the glue bead dries, lightly smooth with 400 grit.

Estes Cosmic Interceptor Build, Part 2, Centering Ring Fitting

Here's all the engine mount parts - 

The centering rings are on the laser cut cardstock sheet to the right side.

This build will involve some fine fitting of parts.

Save the excess cardstock,

at least the large pieces left over.

It'll come in handy for a future build.

The fit of the rings was so tight, they wouldn't slip over the engine tube!

Wrap some 220 around a finger to enlarge the hole until you get a friction fit.

 

Here's the fit I was looking for!

Micro-Maxx Estes Fat Boy, Part 2, Centering Ring Fit

Left side picture:

Two uneven, rough cut rings stacked for gang sanding to fit.

Right side picture:

A 1/4" diameter dowel was slipped in for strength while sanding the ring sides even

Sand, test fit and sand some more until you get a good friction fit in the BT-20 tube.

The finished mount with a MMX motor slipped inside to check the position of the engine block slid in from the top.

The finished mount will be glued in with the motor extended a little beyond the edge of the BT-20 tube.

Micro-Maxx Estes Fat Boy, Part 3, Centering Rings

I sure the small rings are available somewhere, I didn't have them. Why wait for an order. I'm cheap so I'll make a few.

A 1/4" punch was used to start the inside ring hole.

The hole was widened using a knife spin followed by a half round diamond file.

The fit was checked with the yellow engine tube I had.

Center the BT-20 tube over the cut just made and trace with a sharp pencil point.

Cut just inside the pencil line using scissors.

Final fitting in the next post -

Thinner, Lighter Centering Rings?

If you don't have .050" thin cardstock centering rings, You can lighten the engine mount a bit by "halving" 5/20 or 20/50 rings.

On the left is a 5/20 thick centering ring.

Start by drawing a pencil line around the outside of the ring.
 

Using a fine razor saw,

Carefully cut around the ring following the pencil line.

Clean up the rough sawn face using 220 grit on a block.

Here's a single ring, split in two.

Maybe not as light as flat white cardstock rings, but still a reduction of weight in the tail end of the rocket.

 

Estes Time Warp Build, #7321, Part 5, Upper Centering Ring

Here's the upper laminated centering ring,

glued 1/2" from the bottom of the BT-5 tube cluster.

The instructions say to add glue fillets down and between the three tubes.

TIP: I wouldn't do this, it's a long, deep joint. When the glue dries you'll have bubbles and an uneven fillet.

I used a few drops of glue to fill the small center gap. This will block any ejection charge escape.

Years back we used "tissue/glue putty" to fill gaps like this. Tissue/glue putty is a mix of glue and tissue torn into very small pieces. It makes a strong gap filler.

This gap is small, if it were larger I'd make up some tissue/glue putty.

To read more about this gap filler: CLICK HERE 

This top and bottom glue fill also strengthens the mount.

Estes Time Warp Build, #7321, Part 4, Centering Ring Laminates

The center triangle of the centering rings will probably break off. There's not much to hold it in the center.

I'll show how to block the hole (and the ejection charge) in the next post.

When laminating the two sets of two rings, 

use one of the BT-5 tubes to check the alignment.

Don't glue the tube to the rings (yet), use the tube to be sure all three holes are lined up.

The instructions suggest sliding the ring down from the top into a glue ring.

For a cleaner build and less visible glue -  

I slid the centering ring up from the bottom pushing the glue ring up. It's a cleaner visual outside joint on the finished model.. 

You don't have to use much glue, you can always add a glue fillet later.

Estes Semi-Scale Saturn V, Kit #K-39, Part 2, Engine Mount

About 3/16" of the inside of the motor mount tube got a wipe of CA glue applied with a Q-tip.

Never apply CA glue where a wood glue joint will go later. Wood glue needs to soak into the surface. CA glue seals the area where it is applied.

The instructions say to cut a 1/8" square notch in a centering ring.

I used my rotary punch to cut a half circle for engine hook movement relief.

The upper ring got a slight recess cut for a better fit over the engine hook.

Instead of cutting out a 1/8" slice from the clear oversize coupler, cut a single line. Use an aluminum angle (set inside) for a straight cut line.

Slide the coupler in the BT-60 and check the overlap. Mine was a little less than 1/8" wide. Mark and cut the second line a little oversize. Final fitting in the next post.

GOTCHA: When testing the fit of the clear coupler, I found it was cut uneven. One side was longer than the other by about 1/16". If used as supplied, the third upper ring would sit at an angle when butted up against the coupler top. The long side was sanded so all sides were the same length.

New Way Blade Runner, Part 2, Engine Mount

The 20/50 centering rings are laser cut from plywood.

I like to sand off the charring from the faces using 400 grit on a block. 

It's not necessary to do this, I want cleaner parts - especially when the surfaces can be seen on the finished model.

The motor mount tube is marked 1/2" from both ends for centering ring positions.

Slot the tube for the engine hook at 1/4" from the top and insert the upper bend of the hook.

The retainer ring ends up centered between the centering rings. Slide on, apply a ring of glue and into position. 

The fit of the rings was almost perfect! A hair tight.

For a smooth slide over the ends of the tube, a piece of 400 grit was wrapped around a finger and used to lightly "ream" the center hole.

Centuri Skylab Build, #KB-4, Part 13, Lower Tube Centering Rings

The instructions say to "snap" the rings into the tubes by pressing the tube onto the rings on a tabletop.

I rolled a dowel over over the joint to be sure the ring face was flush with the end of the tube.

Internal fillets were applied using a Q-tip taped onto a dowel.

Use small drops of glue on the Q-tip. The Q-tip is then used to smooth the glue and pick up the excess.

A light sanding follows to remove any dried glue and even up any roughness.

Centuri Skylab Build, #KB-4, Part 5, Making Centering Rings

The outside circle is cut with scissors.

The traced pencil line will be a bit large.

Stack the rings on the smaller tube and reduce the diameter with 220 grit on a block.

Again, sand and check the fit.

Here's a good fit in the 2" lower tube.

I used my rotary punch to make an engine  hook notch in the nozzle bell centering ring.

The inside wall of the 3D printed nozzle was thicker than the original kit vacu-formed part. The ring sat high, almost over the top.

The diameter was cut down with scissors.

After rounding the edge - 

The final fit of the nozzle ring is recessed.

Centuri Skylab Build, #KB-4, Part 4, D.I.Y. Centering Rings

TIP: One of the best centering ring materials is the left over mat board found at a frame shop. Ask the manager if they have any scraps, leftover pieces too small to be used in a frame.

If you're lucky they might give them to you for free! If not free, cheap anyway.

Trace around the diameter of the tubes. Trace the larger tube first, it's easier to center the smaller tube afterwards. 

It might take a few tries to get the smaller pencil ring centered.

With a new blade, cut the center out first. 

Cutting the center hole first is easier when you have more of the cardstock to hold onto.

That small circle in the center was on the mat board from an earlier build. I should have erased it for the picture.

Some 320 grit was rolled around my finger to enlarge the diameter..

Sand a bit, check the fit - repeat until you get a good friction fit.

When the hole is to size,

you might find a raised lip around the edge.

Leave the lip. It gives you a tighter fit and a wider gluing edge later on.

Centuri Skylab Build, #KB-4, Part 3, Making A Centering Tube

From the original instructions:

There is a side Kraft centering tube set over the engine tube and engine hook.

I don't have a 3/4" long centering tube, so we'll "make" one.

Three 20/50 centering rings will be used, stacked and glued end to end.

For tighter glue joints, sand the ends flat.

Slide the rings over a BT-20 tube and glue just the rings together, don't glue them to the tube yet. 

Sliding the rings over the tube is for a true, straight alignment. 

The first picture shows how little glue was used.

After the glue dries, slide the three glued rings off the tube.  

The diameter of the centering rings will be too small for a good fit in the BT-52 tube.

Using a glue stick, I wrapped some cardstock around the rings to build up the outside diameter. The ends were then sanded flat.

Here's a good fit in the BT-52 tube.

Don't glue the engine mount in place yet -

Quest Intruder Kit Bash, Part 5, Engine Mount & Kevlar

The Quest instructions use the engine block height to mark the slit cut line. 

Pencil mark and cut the 1/8" wide slot for the engine hook.

The instruction say to glue the two rings 1/2" from the top and bottom of the engine tube.

I don't think that offers enough flex of the engine hook when sliding in an engine.

I set the low centering ring 7/8" from the bottom.

Instead of 1/2" from the top of the tube - 

The upper ring was set over the upper bend of the engine hook, approximately 1/4 from the top of the tube.

I've pencil marked the ring to show how the ring is centered over the hook.

This strengthens the mount. 

The instructions have you tie a double overhand knot to secure the Kevlar under the upper ring. That thick knot might bulge the outer tube - not much room between the 20/50 rings and 1" diameter tube.

I rolled the Kevlar around the tube with the overhang tail twisted under the start of the line. The twisted Kevlar end is pushed into the glue fillet.

Quest Intruder Kit Bash, Part 4, Parts Prep & Centering Rings

The shoulder base was glued into the nose cone using Fabri-Tac glue.

This glue works great on simple plastic to plastic and plastic to body tube joints.

It is not recommended for delicate assemblies like a Mercury Redstone tower.

The Quest instructions offer a great TIP:.

For a better fit over the engine mount tube: Use the tapered nose cone to compress down the burrs and slightly widen the diameter of the centering rings

I'm replacing the thin yellow engine mount tube with an Odd'l Rockets heavy wall BT-20H. This will require a some  peeling of the inside layers of the centering rings to fit the  slightly wider diameter tube. 

It doesn't take much of a peel for a good sliding fit.

Odd'l Rockets BT-20H heavy wall tubes are only available through jonrocket.com. 

TIP: In the left pic: To prevent peeling, don't cut an engine hook recess slot on the diagonal inside seams. 

Right side pic: Start your notch on the other smooth side.

On the left: The engine hook notch is cut. I marked it with pencil to show up better in the picture.

On the opposite side of the engine hook notch, the upper ring gets a Kevlar notch made with a diamond file.