Centuri Skylab Build, #KB-4, Finished

This build was more detailed than I thought it would be.

The 3D parts are heavier than the original vacu-forms pieces. 

The Centuri catalog says the weight is 3.4 oz. This build weighs 4.1 oz.

A B6-2 and C6-3 were the recommended motors. I'll launch mine with a C5-3 Super C.

That black turbine exhaust tube reminds me of the exhaust tube on the old Estes Thor Agena B.

The solar panel fins came out very well. They aren't textured but still look okay.

The docking collars are larger and dish shaped. The catalog picture was probably a prototype. The prototype had docking collars that looked like two short lengths of launch lug.

Decals, decals and more decals.

The original kit nose cone was smooth, but I like the raised line ridges on the 3D print.

Centuri Skylab Build, #KB-4, Part 27, Recovery Sling

Horizontal recovery is recommended. 

This would protect the thin vacu-form nozzles at the tail end. This 3D printed nozzle is thicker walled, much stronger than the original kit part.

On my Odd'l Rockets F-104 kit I recommend horizontal recovery similar to what is shown here. The multi piece "T" tail can crack on a hard landing.

Use knots that won't "slide"

I used a simple overhand knot to join both the 12" shock cord to the 12" of string. (Left side of the above drawing.)

The string is #10 cotton embroidery thread. #10 cotton thread is very strong and a bit stretchy.

The lower string to the upper shock cord was joined with interlocking loop knots. (Center inverted "V" in the above drawing.)

The low end of the long string (right side in the drawing) is tied around the large nozzle. 

Tie the knot so that string extension doesn't hit the black exhaust lug or any other pieces that could tangle up at ejection.

Centuri Skylab Build, #KB-4, Part 26, More Details

The Centuri catalog picture shows a prototype build. There is a chrome band around the engine pods. The docking collars are smaller. Some of the decals are different than what came in the kit.

Look close at the detailed vacu-form band. There are some of the raised areas painted black.

The 3D parts included two of the wraps. One was joined to slide over the larger tube. The other was flat, meant to be rolled around and glued to the tube.  

I didn't use the flat one on the model. I used it to practice the black markings like in the catalog picture.

Using the side (not the tip) of a Sharpie, the highest points of the print got some black details. 

This gives an idea of how much black was used.

Just enough - 

Centuri Skylab Build, #KB-4, Part 25, New Turbine Exhaust Tube

After lots of handling during the build, the exhaust tube broke loose.

There wasn't much glue holding it against the motor mount tube.

(The picture on the left shows the first black tube.) 

I cut a new one and filled the seam with CWF. It was sprayed black off the model.

For a better, wider glue bond against the inside motor tube - 

The side of the lug was pushed in to flatten and widen the gluing surface. It took a little coaxing with a fingernail to put a curve in the flattened side.

The lug was sprayed black off the model. The inside end was masked off for better glue adhesion.

Wood glue was used to set the lug against the tube on the inside.

I wadded up a paper towel to put pressure on the lug and position it at the right angle.

After the inside glue dried,

CA glue was applied with a toothpick leaving a hard, clear fillet.

TIP: Cut off just the very tip off the toothpick and round the new end with sandpaper. The wider, round tip will hold more glue for the transfer onto the model.

This second try had a cleaner color separation with it being painted black before gluing into the rear centering ring hole.

Centuri Skylab Build, #KB-4, Part 24, Decals!

I drew up the decals from the scans at Jim Zs. These were sized for the slightly larger diameter Centuri ST-7 tubes.

Shown on the left - 

The second lined wrap decal was cut a bit shorter to fit the BT-20 tube.

When cutting a decal like this,

Round out the clear areas instead of cutting into the corners.

A sharp inside corner could end up tearing.


 

This louvered hatch decal goes over the nose cone.

The 3D print has a raised line.

Smooth and work the decal into the ridge with a wet Q-tip.

Here's the finished nose cone.

Those small camera focus targets are always difficult to set on straight.

Centuri Skylab Build, #KB-4, Part 23, Fin Face Decals

I had to trim the solar panel decals after trying a dry fit on the square fins.

Cuts were made on all four sides almost to the vertical and horizontal lines.

These transferred easily. Wet the entire flat surface before applying the large decal. Centering took a moment or two.

The final look was better than I hoped.

While this doesn't have the raised texture of the original kit stickers, it still gives the right impression.

Centuri Skylab Build, #KB-4, Part 22, Chrome Fin Faces

With the backing still on - 

Fold the chrome trim piece in half so the crease will roll over the leading edge.

Peel off the backing and set the fold over the rounded forward edge.

Don't adhere the entire piece, but pull down on the leading edge pinching between your thumb and index finger.

After the leading is good, then smooth the rest of the skin from top to bottom.

Over time, the chrome cover might lift.

Here's what happened to the Phoenix Bird sticker. I don't think I got a good tight fit over the leading edge.

The piece was cut to the width of the fin but cut a little long to overhand the trailing edge. 

After the skin is burnished, the overhang is carefully trimmed off with a new single edge razor blade.

Here's one of the good fins.

There are some dust specks that make raised areas on the others.

I hope the solar panel decals will camouflage the spots.

TIP: Chrome Monokote Trim material can be hard to find. I got my self-adhesive chrome sheeting from Balsa Machining Service.

Centuri Skylab Build, #KB-4, Part 21, Black Trim Paint

Suggested in the instructions: 

The long launch lugs on the outside edge of the solar panel fins are painted red or black. I chose black.

The mask lines don't have to be sharp, the paint edge will be defined by the chrome overlap. 

The exhaust tube (shorter launch lug) is also painted black.

This would be a tough mask so I outlined the tube with a ultra fine point Sharpie.

The rest of the lug was "painted" with a wider point Sharpie. You can't always get a good coverage with the Sharpie. Don't try to cover larger areas with a felt tip pen.

Centuri Skylab Build, #KB-4, Part 20, White Trim

I couldn't find 1/16" wide pinstriping tape at the auto supply stores.

I could find it online, but I didn't want to wait.

Michael's craft store had peel and stick vinyl in small rolls.

On the left is a closeup of the pod nose cone. You could smooth it out with sandpaper, but I like the extra detail.

The main nose cone picture shows the tie down lug. Whoever did the 3D work made it very strong.

The pods are centered when glued onto the smaller support fins. 

The glue line was scraped and the centers marked for easier placement.

The instructions show 1/16" wide tape strips added for extra details.

On the long upper body tube I'll wait until after the decals are applied. 

It would be difficult to apply decals over the raised tape lines.

Centuri Skylab Build, #KB-4, Part 19, Paint & White Trim?

The larger main nozzle and pod nozzles are painted silver off the model.

Mask off the coupler areas on all three.

The remainder of the model is painted gloss white.

I haven't glued on the engine pods yet. I figured it would be easier to sand between coats without the pods in the way.

Red 1/16" wide pinstriping tape was supplied in the kit. 

The instructions have you lay down the red tape for texture and detail lines. Then - paint the model white. 

I'd be concerned the red tape would show as pink through under the white paint. I'll paint the model white then add the white pinstriping lines. 

The remainder of the red tape lines is set down after the white paint is dry.

Centuri Skylab Build, #KB-4, Part 18, Docking Collars

The docking collars are set into holes drilled into the body tube.

Start with smaller diameter drills and work up to the 1/4" diameter needed.

I simply finger twisted the drill working it into the body tube.

Don't worry about the rough edges.

Push them to the center - 

Round out the holes and push the rough fibers into the hole with a sharpened dowel.

Set the dowel in the hole and twist.

Don't enlarge the hole beyond that 1/4" diameter. Check the fit of the docking collar and try for a friction fit.

The docking collars were glued in the holes using Fabri-Tac.

This is turning out to be a very detailed model.

Centuri Skylab Build, #KB-4, Part 17, The Shroud Tunnel

The shroud seam was scraped and sanded to lower the tab area.

TIP: Plan ahead where the shroud seam will be. You should consider where and how the tall UNITED STATES decal will be placed. I tried to follow the instruction illustrations but with where my shroud seam is, the decals won't end up like the face card picture.

Line up the shroud seam, in line with one of the large, square fins.

The instructions are vague regarding the shroud seam. The instructions do say to cover the shroud seam with a wood tunnel. 

It's a little tricky getting the angled tunnel joint to match up.

 

I'd recommend using a sanding block to keep the tunnel end tapers consistent.

After a few tries, the tunnel joint is about as close as I could get.

I'll still add some CWF filler to the joint crack.

Centuri Skylab Build, #KB-4, Part 16, Oops! Gluing On The Wrap

The 3D wrap was a bit large and slid loose on the 2" tube. I decided to cut out a sliver for a tighter fit.

3D plastic is brittle! When I tried to score the cut line the piece cracked.

The second break was down the cut score line. I set that piece aside. I'm not really concerned as the launch lug will cover any seam.

The wrap was glued on using Fabri-Tac glue. Fabri-Tac contains acetone and works well with plastic to Kraft tube joints.

The Fabri-Tac gives you a little working time, it's fairly slow to dry.

Tape was used to hold the wrap tight as the glue set up.

That broken off piece was glued and slid into place.

There was a gap towards the top. No big deal, the launch lug will cover it.

Centuri Skylab Build, #KB-4, Part 15, Skinning The Fins & Fin Gluing

As it turns out, the fins are too thin for a friction fit in the support slots.  I'll need to laminate some cardstock to increase the thickness.

The mat board fins had the leading edge rounded for a smoother "fold-over" of the cardstock skin.

The 110 lb. cardstock was cut oversize.

The outside layer will be "butterflied" with the fold rolling over the leading edge. Score and pre-fold the leading edge.

I used a glue stick to adhere the skin.

Set the folded edge first over the rounded leading edge.

After skinning the two fins - 

The 3" long launch lug tubes are glued to the outside edge of the fins.

The two square solar panel fins and smaller pod supports are glued on.