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.

Centuri Skylab Build, #KB-4, Part 14, Fitting The Shroud, Gluing The Fin Supports

The first dry fit of the shroud fit showed a gap.

Turns out the glue fillet on the tube and centering ring joint wouldn't allow the shroud to seat all the way down. The fillet was sanded and the centering ring hole slightly enlarged.

I got a better fit but one side was slightly high. The high side was sanded using a block.

Here's a better fit of the shroud on the lower body tube.

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

The solar panel (fin support) gluing area had the filler/primer scraped off for a better glue bond.

After placing on the tube, they were held down with rubber bands as the glue dried.

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 12, Kevlar & Engine Mount Gluing

If your Kevlar starts to fray or unravel, a drop of glue will hold the end tight for tying.

Tie a small loop knot. I added a heat shrink tube like in the New Way kits.   

My loop knot was almost too big, Keep it small so the bare Kevlar won't be exposed to the ejection charge.

The loop was passed under the upper bend of the engine hook. Carl at Semroc came up with this idea.

The 3D nozzle bell was slid up until the low bend of the hook was even with the end lip of the nozzle.
 

A line of wood glue was rolled around the outside of the tube. The centering ring was pressed in place. 

A Fabri-Tac fillet was added around the outside of the card to plastic  ring joint.

Centuri Skylab Build, #KB-4, Part 11, Long Warped Tunnel

The 3D printed long tunnel was warped!

I tried but couldn't get it straight.

A new tunnel was cut from 3/32" thick basswood.

I darkened the underside with pencil to better see the curve sanded to fit the BT-52 pilot tube.

Instead of wrapping sandpaper around the BT-52 tube, I wrapped 220 grit around an engine casing. 

TIP: When contour sanding - You can get a better fit using a smaller diameter tube or casing.  

What's left of the pencil lets you see how much has been sanded. The picture on the left shows a little more work is needed.

On the right is a good fit, probably as good as it'll get.

The lower 2" tube, shroud and upper tube were slid together for a shot of filler/primer, no glue yet.

In the picture, the upper tube was pushed up to show the unpainted gluing area.

Centuri Skylab Build, #KB-4, Part 10, Panel Supports

This is one of the few kits where pre-cut (die-cut) balsa needs to be recut. It makes me wonder if the die-cut razor blocks was made too long. Or, maybe the extra length was needed for strength when doing that center punch?

From the instructions:

You are told to cut off 1/8" off each side of the die-cut panel supports. Then bevel the ends to a 45 degree angle.

 

Later on, there has to be a 1/8" space between the top of the panel support and the bottom edge of the wrap.

On the left is an early dry fit of the wrap and top of the panel support.

In the inset picture is the beveled top.

California Trip, Part 2

I took second place at the Musical Saw festival.

The first place winner was a great player with a real flair.

I also won funniest saw joke and farthest traveled!  

That's my High School friend Ron, his mother taught me the accordion.

He's sitting on a redwood stump. The festival was held next to the Henry Crowell Redwoods state park. 

Build posts will resume on Thursday - tomorrow I travel back to Orlando.

California Trip, August 9 - 13, 2025

I might miss a few days of build posts - 

I'm off to California to compete in the International Festival Of The Musical Saw! 

In 2022 I won a saw competition held in Barberville, FL. That's me on the right, holding the saw.

This upcoming Saw Fest is held in the shade of the Redwoods at Roaring Camp in Felton, Ca. It's known as the big, original saw competition. Felton is close by to my hometown of Watsonville, CA. 

In nearby Santa Cruz is a statue of Tom Scribner, who played Saw on Pacific Avenue.

In the late 1970s, I entertained at Roaring Camp. Banjo, Guitar, Harmonica and Musial Saw serenaded guests in the BBQ area. 

We had many Japanese tourists brought in by the busload. They were fascinated by cowboys and would often request: "Play Bonanza! Play Bonanza!"

Centuri Skylab Build, #KB-4, Part 9, Small Balsa Hatch

There's a small die-cut disk on the balsa sheet.

I set the scan into Corel Draw and set the 1" span to a drawn 1" box.

That brought the disk to a 0.40" diameter. 

I didn't want to use balsa for the disk.

I found some 5/60 centering rings in the spare parts drawer.

The centers were punched out and glued together using a clothes pin clamp.

These are 1/2" diameter. 

I marked the .4" center diameter.

Chip cuts were made with an X-Acto.

This left a choppy edge.

220 grit on a block cleaned up and rounded the edges.

The edges should be sealed, the easiest was is with white glue.

Apply a bead of glue making sure it fully covers the side edge. Keep glue off the flat face. Let dry.

Sand smooth with 400 grit.

Centuri Skylab Build, #KB-4, Part 8, Drawing Up Decals

New decals were drawn up in Corel Draw. 

I probably could have used the decal scan from Jim Z's but I like a challenge. It also looked like the Centuri kit decals were on a sheet taller than 11". Home print decals are a standard 8 1/2" x 11" size.

The original kit had some sort of embossed thermal foil used in attic insulation.

I did a post about it in February of 2020: CLICK HERE

This time around:

The second decal grid sheet on the right side shows my attempt at the solar panel fin coverings. 

The 3" x 3" square fins will get a chrome Monokote skin followed by the blue grid water slide decal. Results were very good the first time this technique was tried: CLICK HERE

In the lower right of the solar panel decals are the fine ink lines used to finish the Mini Bomarc.

Centuri Skylab Build, #KB-4, Part 7, Fitting The "Super" Shroud

Mentioned in the previous post - 

Here's the smaller end showing the inside stepped shrouds.

This gives a better fit and adhesion area onto the smaller tube.

One of the previously made centering rings is glued into the doubled shroud. 

After the glue dries, the edge should be stiff enough to sand off, even with the face of the centering ring. 

The fit is good -

Even if the low end were a hair wider than the larger tube, the 3nd printed instrument wrap would cover any shroud lip.

In the next post:

Now that all the parts are almost ready, the actual build can start. 

Centuri Skylab Build, #KB-4, Part 6, Making A "Super" Shroud

Cardstock shrouds have always felt like the weakest part of a LPR build. You can make a stronger two layer "nested" or super shroud.

For a complete explanation of the technique, I wrote an article for the Apogee Peak Of Flight: CLICK HERE
 

Go to payloadbay.com and click on "Tools", then to "Transition Tool".

Enter your tube diameters and length of the transition.

I printed the transition on 110 lb. cardstock.

The unused lower half of the page is cut off and taped behind the printed transition. Two layers are cut out at the same time. 

Note the glue tab in the upper right, added it with a pencil line.

I don't pull the shroud under a straightedge or pull it over a table edge.

Form the shroud in the heel of your hand with a smooth dowel. Press the dowel in an arc matching the curve of the shroud. 

Your shroud should be formed until it can stand on its own.

I don't put glue on the outside glue tab,

the glue stick goes on the inside where the tab will touch.

This makes the glue area easier to handle and prevents any glue getting on the outside of the shroud.

Burnish the glue tab area over a dowel set on the inside.

Repeat with the second shroud.

Pick the best shroud to go on the outside.

 Apply glue to the outside of the central shroud and press the two together placing the seam joints on opposite sides. 

After drying you'll notice how much stronger a nested shroud is. It almost feels like sheet plastic.

Inside the smaller end  the tow shrouds are "stepped" making a better joint over the upper tube. 

Look at the bottom and you can see the inner shroud overhanging the outside shroud. This will be sanded off in the next post.

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.