Enerjet by Aerotech Strong Arm Build, Finished

All three Strong Arm builds posed in my patio.

Two are show builds with filled seams and more time spent on fillets.

On the right is a flight build, not as much build time involved. Body tube seams are visible and not as smooth a finish. 10 foot rule on this one.

I rarely use Rustoleum, but that was the best paint match for the tall gray stickers on the upper body.

Some graphics are large and look great overall.

Plenty of small labels too.

The low end fins. 

The fin locks feel very sturdy.

So far, this is a favorite of the mid-power builds I'm doing for Aerotech.

Enerjet by Aerotech Strong Arm Build, Part 24, Engine Retainer

The inside edge of the motor retainer should be roughed up for better epoxy adhesion.

I used the back side of my knife to scrape off the paint. Using the back of the blade will rough the surface and not dull the sharp side of the knife.

The fit of the ring is tight.

To make an easier slide in and seat, the edges of the motor tube were slightly rounded with some 320 grit sandpaper.

Here's the ring slid in until the motor tube butts up against the raised ring inside. 

After the epoxy dries, the cap can be screwed on. 

The trailing edges of the fins are longer than the retainer cap so the rocket can stand on it's fins.

Enerjet by Aerotech Strong Arm Build, Part 23, Final Stickers

I'm building three of the Strong Arm kits for Aerotech and wanted consistency in the models.

I made a template out of cardstock.

Trace around one of the fins.

With the backing still on, set the sticker on the cardstock in a good placement.

Draw around the sticker border and cut out the square.

This is another wet sticker placement.

Set the sticker on the fin, lay the template over the fin and check the sticker position.

Lift and replace until it is centered in the cut out "window".

These dots or screw stickers were included but there is no reference of the placement. I decided to leave them off the rocket.

Placing the stickers takes time!

I counted 66 stickers on each model!

Enerjet by Aerotech Strong Arm Build, Part 22, Small Stickers

There are a LOT of small stickers

Thin strips can slide while cutting using a metal ruler. Make the cuts carefully.

I'd recommend keeping the small stickers in zip lock bags. 

I was being careful and one fell off the workbench. I had to scour the floor to find it.

 

The RADOME stickers are spaced 90 degrees around the top of the tube.

I reused the placement guide to evenly place these stickers.

Enerjet by Aerotech Strong Arm Build, Part 21, Body Stripes

I wrapped a piece of cardstock around the body tube to use as an edge guide for the body wrap strips.

If you've ever tried to get a stripe to meet up after wrapping it around a body tube, you'll appreciate a cardstock guide.

For a cleaner look, start and finish the strip over the launch lugs.

I read these colored stripes designate if a missile is a dummy or armed. 

Tape the guide edge in place, 

Wet the body tube where the stripe will go,

Peel off the backing, dip the strip in some water and leave wet.

As I rolled the stripe around the the tube, I would dip my finger in some water and wipe it under the thin sticker.

Here's the lowest stripe.

Notice the overlap, again centered over the launch lug side. Hiding the overlap joint makes for better pictures on the launcher.

The longer yellow and black stripes go all the way around the tube.

The shorter red, gray and black stripes fit between the dorsal vanes.

These are a little tougher to place, you'll want all separate four segments in line.

For a guide, I placed strips of masking tape on all four sides. I could visually align the stickers against the masking tape strips. 

The red and gray strips are longer than needed. Set one end against a vane side, trim the overhang off the other side with a razor blade.

Enerjet by Aerotech Strong Arm Build, Part 20, Placing The Fin Stripes

Cut a strip of cardstock 15/16" tall.

Set the strip edge into the fin/tube root edge joint.

The strip side is set against the top edge of the cardstock. 

Notice the rear edge overhangs the trailing edge. 

While the front edge of the sticker matches the angle of the leading edge, the trailing doesn't quite match. 

Leave some overhang and it can be trimmed off after the set sticker dries.

Recess the from edge of the sticker very slightly.

No reason to let it overhang. You want good adhesion without rolling it over the leading edge.

Enerjet by Aerotech Strong Arm Build, Part 19, Placing The Roll Bar Stripes

Setting the vertical roll bar stickers straight with even spacing is difficult. 

How can you leave 17/32" space between them accurately?

      

Two vertical stripes have to be centered between the fins. Mark the center line first. 

Make a simple cardstock centering guide. 

Roll some cardstock around the tube, mark the end of the dorsal fins. Using a ruler, find the center and mark. Make light pencil center lines on the tube. 

Repeat and find the centers between all the dorsal fins.

Before placing any stickers - 

Use a clean knife blade to lift and handle the stickers.

Rub a line of water on the body tube where the sticker will go.

After peeling off the sticker backing, dip it in water and leave wet. The wet sticker allows you lift and reposition.

Notice the placement guide I printed out.

I drew pencil lines, 1/4" to each side of the print line to total 1/2", the width of the stickers.

The low end of the placement guide was slid down to the 6 1/2" top of the sticker position.

Set the top of the sticker between the pencil lines

Use the aluminum angle to line up the sides of the stickers. 

When done, you should be close to the recommended 17/32" spacing between the bars.

Enerjet by Aerotech Strong Arm Build, Part 18, Waiting For Paint To Dry and Planning Ahead

You may have noticed a slowing of posts - 

That's because I'm building three Strong Arm kits at the same time.

One is a flight version - no seam fills and less attention to details. These are sometimes referred to as: "They'll look good on the pad."

Duplicate builds slow things down, I can't repeat the same build posts three times.

Planning ahead,

You might assume this roll pattern sticker would just roll around the tube -

These will have to be cut apart and placed individually.

But, there is 17/32" space between each vertical bar. 

To make placement easier, I'll print a spacing guide. It'll be a fin marking guide from payloadbay.com

To get to the marking guide tools: 

CLICK HERE

Hit TOOLS and then FIN WRAP TOOL.

There are eight bars going around a 2.638" diameter tube.

Enerjet by Aerotech Strong Arm Build, Part 18, Overall Paint Coverage

The larger the rocket, the more difficult it is to get a good gloss coat of spray paint. The Strong Arm is big enough to be a painting challenge.

To get an idea how I spray models horizontally, 

I'll refer you to a previous post: CLICK HERE 

I'd recommend reading the post to understand the technique:

Enerjet by Aerotech Strong Arm Build, Part 17, Adapting A Painting Wand

I use painting wands to hold my rockets horizontally when spray painting.

The wand is a 1/2" dowel shoved into a used 18mm engine casing. 

This is too small a diameter to fit this larger rocket engine mount.

I wrapped some corrugated cardboard around the casing and closed it up with tape. To fit the 29mm diameter mount, the cardboard is just over a full wrap around the casing. This wider diameter gives a good friction fit. 

With the dowel wand slid into the mount,

Some masking tape is placed sticky side out inside the main body tube.

A rolled up paper towel is press into the area around the mount and up against the inside wall of the main tube.

Any open areas are covered with additional pieces of masking tape.

Now the rocket can be spray painted without getting any paint inside the low end.

Enerjet by Aerotech Strong Arm Build, Part 16, Setting The Lowest Centering Ring

I'm back from vacation, hoping to paint the lower body assemblies - but, it's been raining! So, onto other steps.

 

Check both sides of the centering ring, pick the smoothest side to be exposed out the bottom.

On one side, there was a chip. I marked this side with "X's". This side will be facing up, not seen. 

The low edge of the body tube is slightly "squared", out of a perfect round. The four fins are locked into the rings and pull in the body tube. 

It would be very difficult to "slide" the ring in with the tube slightly out of round. 

On the left, I sanded an angle into the edge to make the insertion easier.

Notice the laser charred edge has been sanded.

The center of the ring also got a taper to slide over the engine mount tube.

The ring is slid in and rests against the root edge tabs of the fins.

Here I've applied a wood glue fillet around the ring/tube joint.

Enerjet by Aerotech Strong Arm Build, Part 15, Nose Cone Re-Paint & White Paint

The nose cone color was picked to closely match the upper roll bar on the sticker sheet.

An earlier post showed bubbles as the nose cone paint dried. 

I usually don't use Rusto spray paint but this gray was the closest.  This time, the spray coat was even and glossy.

The rest of the body is painted a gloss white with no masking.

Here's the body after a light first coat. Sanding followed with 400 grit.

Enerjet by Aerotech Strong Arm Build, Part 14, Launch Lug Fit & Fillets

While the fit of the vane sides were pretty good, the edges could still use a fillet.

I used Titebond Quick and Thick with a smaller Elmer's glue bottle nozzle. 

TIP: On a long fillet like this, it's easier to glue and smooth about half of the length, then do the upper half. Too much excess glue can pool under your finger when smoothing out a long fillet. 

GOTCHA: The coupler end inside the upper slot prevents the front of the launch lug from fully seating.

I filed down the front half of the positioning tab to fit over the coupler.

Beacon Fabri-Tac was used to glue the launch lugs in position.

A piece of masking tape held it down while the glue sets up.

I'll be on vacation for the next five days, there may not be posts while I'm away.

Enerjet by Aerotech Strong Arm Build, Part 13, Gluing The Vanes

 

With the low end tip of the vane set at the tape wrap, 

the vane is pressed in place down the pencil line.

Hold the vanes in place with tape as the glue sets up.

Go back and check the alignment to be sure there wasn't any movement. Epoxy is slippery!

Check the edges for any glue that may have squeezed out.

You can pick it up with a Q-tip.

I'm building three of the Strong Arm kits, you might notice one build with no seam fill or filler primer.

On one build, I glued the vanes on using Fabri-Tac with good results. Fabri-tac takes a while to dry, the bond felt as strong as the epoxy joints.

I had a few vane tips that ended up raised.

In the top picture, you can see the open end.

Here, I've used a wood glue fillet to fill the gap.

Enerjet by Aerotech Strong Arm Build, Part 12, Setting The Vanes

The rear of the vanes are 2" from the front tip of the fins.

Instead of using the wrap around guide, I got out my aluminum angle.

It's pretty easy to draw a pencil line, extending from the front leading edge tip of the fins.

I made a 2" mark on the angle and transferred that onto the body.

For position consistency, 

I pencil marked an even wrap of masking tape.

The low end of the vane will be set just above the tape wrap. The picture shows a dry fit.

I tried using CA glue on the back of the vane to adhere it, but there wasn't enough surface contact for a good bond. I've got to use epoxy. It'll flow and fill some voids.

15 minute epoxy was spread on the underside of the vane using a Q-tip stick with the cotton end removed. 

To even out the epoxy bead and prevent squeeze out beyond the edges - 

I wiped off the sides with a folded paper towel. This evens out the bead over the entire length of the vane. 

The even center bead result is shown on the right.