Estes Aries SST, #1927, Build, Part 7, Engine Shrouds

A comment by Naoto K. has proved true!

Those round leading and trailing edges cause the engine shrouds to overhang the balsa.

With the front of the shroud pulled back a little from the rounded edge, the rear of the cardstock overhangs the trailing edge.

I tried the fit of the shrouds over the middle rib.

The rib height is good, at 3/8" away from the root edge, it's just a hair off center.

I trimmed back the back side of the shroud to better fit at the rounded trailing edges.

The rounded wing trailing edge also required trimming back the middle rib.

There was some surface cracks at the sharp folds. The thicker the cardstock, the more likely the folds can start to break up.

I brushed on a thin coat of white glue, keeping the glue on the fold, not down the sides.

After the glue dries, some light sanding can smooth some of it out.

Estes Aries SST, #1927, Build, Part 6, Engine Shrouds

I wanted to make the shrouds out of something a little thicker than the regular 110 lb. cardstock. I had some thin posterboard for years, it's about time to use it! It's also shinier on one side - perfect!

The templates were printed on cardstock, the posterboard would be too thick to run through the printer. Shrouds were traced onto the the posterboard with a sharp pencil. Fold lines were added.

Emboss the folds before cutting out the shroud.

I always use a un-serrated butter knife tip and a metal straightedge. 

Gently coax the folds little by little to keep the the edge clean. I did get some slight breaking of the paper fibers. More on this in the next post.

The fold was worked in over my aluminum angle, rubbing the line with a burnisher.

The right and left engine shrouds, almost ready for assembly.

There will be some adjustments when fitting to the model.

Estes Sandpiper, Kit #1389, Part 10, Sanding The White Undercoats

After the first white undercoat,

fine sanding with 400 grit showed there was still some uneven fillets.

The inside fillets are a little hard to reach.

This one showed a bubble after sanding. More glue - 

This had to be the best fitting shroud I've ever done!

It was surprising, I didn't have a shroud tool, the one at payloadbay.com wasn't available. Those tools are now at jonrocket.com.

Smooth, with very little filling.

The 3D printed nose cone turned out very smooth!

Initially, there were very subtle ridges, but those sanded out. One shot of filler/primer and sanding got it ready for color.

Estes Sandpiper, Kit #1389, Part 9, Fillets Down The Long Launch Lug

Sometimes I don't bother with launch lug fillets, it's a pain dealing with the air bubbles when the glue dries.

To the left is the first glue fillet still wet, just smoothed with a finger. Let the glue totally dry.

Here's the same fillet, dried with air pockets. Another glue fillet will fill some of the open holes.

It'll take three or four fillets to fill and smooth the glue line.

After three fillets the inside fill is looks smooth. 

You can lightly sand the fillet to further smooth before paint.

This launch lug/tunnel reminds me of the old Estes Wac Corporal kit. The long lug on the Wac Corporal is concealed with balsa strip sides.

Estes Sandpiper, Kit #1389, Part 8, Gluing The Lug Shroud

The sides of the lug shroud spread out when the glue on the bottom dried. The sides needed to attach to the launch lug.

A line of glue was spread down the edge of a razor blade.

This was transferred and spread down the inside edge of the shroud.

A dowel was pressed against the side to form the shroud flat against the lug.

Hold the dowl in place until the glue starts to set up. Repeat on the other side.

Here's the finished shroud, straight and tight.

Estes Sandpiper, Kit #1389, Part 7, Gluing The Lug Shroud

The launch lug shroud is glued on, centered between the two wing fins.

The bottom end is even with the motor mount tube.

The fins are glued on, centered and perpendicular to the wings.

The glue on the shroud bottom shrank a bit and turned the sides out.

It'll take some patient pressure to get the sides adhered to the launch lug.

Estes Sandpiper, Kit #1389, Part 6, The Long Launch Lug

The launch lug is 9 1/2" long.

I slid it over a straightened coat hanger for support when I sanded down the CWF filler.

In the instructions is a full size drawing for the angle cut of the top of the lug.

The low end of the launch lug hangs over the tail cone. To connect the sides, a folded "shroud" glues to the tail cone and the sides of the launch lug.

Pre-fold the lines before cutting out the shroud. I'm using the tip of a non-serrated butter knife to emboss a fold line.

After embossing the fold lines, cut out the shroud.

Coax the lines gradually working up to sharp folds.

Estes Mini Arcas, #2441, Part 5, Tail Cone Fix

Next time you make a tail cone, try placing the glue inside the end, opposite the glue tab.

I decided to make a double layer "super shroud". This makes a much stronger piece.

For more detail, I wrote an article for the Apogee Peak Of Flight newsletter: CLICK HERE

Notice the lower step inside the cone in the right side pic.

Glue one cone inside other.

Let dry with a coupler inside (don't glue the coupler in) to maintain the round shape.

After all is dry,

Cut off the upper overhang using the ridge as a guide for a razor blade.

Sand the upper side square using a sanding block with 400 grit.

Estes Mini Arcas, #2441, Part 4, Tail Cone Fix - Gotcha!

After forming too many shrouds printed from the scanned kit tail cone,

I thought I'd try the provided kit shroud.

GOTCHA: The kit shroud fit like my scanned cardstock ones did - 

It fits the BT-5 but was small on the BT-20 top end.

So - off to payloadbay.com and their transitions tool.

Four more were printed and cut out.

Notice the picture on the left - 

Run a fingertip over the curved sides, you'll feel some very subtle raised areas. With 400 grit, sand and round them down. This removes the high spots and makes a better fit at the base of the BT-20.

Four cardstock tail cones were formed with a clean dowel in the heel of my left hand. Check the last post picture.

Estes Mini Arcas, #2441, Part 3, Tail Cone Problems

Cut the flat sides with a ruler and sharp knife. 

Cut the curves with scissors.

I make a smooth curve by rolling a dowel in an arc pressed against the soft heel of your hand. 

It take very little glue to join the ends.

With the printed edge lines lined up, I held the shroud closed using smooth faced tweezers.

 

Here's where I ran into problems.

The bottom fits the BT-5, but the wider end doesn't match the diameter of the BT-20!

I made another tail cone with a slightly wider top. 

It was still too small!

These two shown above aren't the kit supplied tail cone. The kit shroud was scanned and some extras were printed up on 110 lb. stock. There doesn't seem to be any difference in size between the kit shroud and what I printed. I was saving the kit tail cone for a final try. It's a bit thicker and has a smooth side.

Estes Mini Arcas, #2441, Part 2, Tail Cone

Any rocket kit that has a tail cone only includes one cardstock shroud. If you've ever formed a cardstock shroud, you know the fit might be iffy. 

I won't be taking any chances with a single shroud.

I drew a 1" reference line above the printed kit shroud. The tail cone was scanned, the 1"reference span was double checked in Corel Draw. The shrouds were printed on 110 lb. cardstock.

Will I really need eight tail cones? No.

But, I can make a few and use the best fitting shroud.

Estes Semi-Scale Saturn V, Kit #K-39, Part 19, The Structural Skirt

I had scanned and printed extras on 110 lb. stock. Good thing I did!

The structural skirt is small and difficult to cut out and form. It took three tries to get a decent piece.

The first try was cut out with scissors, that inside arc cut was too small. The next two skirts were cut using a new blade knife.

The larger outside arc was cut with scissors.

Any high points were rounded off with 400 grit on the block.

A sharped point dowel was used to form the skirt before gluing.

Using very little glue, the tab was held shut with smooth tweezers.

The skirt was slid down onto the top of the the tower.

The seam line was rotated over the one corner of the tower to be less noticeable.

I Wish Manufacturers Wouldn't Do This, Part 4 . . .

PRINTING ON SHROUDS - 

Some kit shrouds have printing on the outside, finished model surface.

The printed words "Outer Shroud" could bleed through the paint. Position that wording outside the shroud!

You don't run into this very often. The original Estes Mars Snooper was another kit with printing on shrouds.

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 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.