Aerotech Mega Initiator #89541, Part 13, Prepping More Stickers

Here's the upper body wrap. 

The curves were cut with scissors. Notice I cut a little away from the orange arcs, just playing it safe on the clear border.

Cut the straight lines with a knife and straightedge.

 

In addition to lining up the top edge with the tube end,

you'll need to line up the wrap left side down the tube.

Use your aluminum angle to draw a light pencil line down the tube, as long as the left edge of the wrap.

Before peeling off the backing, do a dry fit.

When the lower arcs were lined up, I noticed one side of the wrap was a bit tall. I went back with a straightedge and cut a long sliver to even up both sides.

Next post we'll attach the roll wrap. It's easier than I thought it would be.

Aerotech Mega Initiator #89541, Part 12, Applying The Stickers

I know - I postponed some posts on this build. There are good reasons why. 

I'm not very experienced making epoxy fillets. Sure I've done them, but I'm not enough to show you a best method. 

Another reason - It's difficult to get an even, gloss paint finish on large rockets using store bought spray cans. If you've ever tried to get a good gloss on a 4" diameter model you know what I mean. You really need a spray gun and maybe an auto body spray booth! 

 I do have experience with stickers, this kit has peel and stick decor. But, there are some concerns. Some kit stickers are now printed at Aero tech and require different considerations. 

In the past I've wet the surface of the model and dipped the sticker in a dish of water. The water allows repositioning. It's rare when a sticker is perfectly positioned on the first try. 

I tried the water dip but it loosened the adhesive on the back of the sticker! Pulling up the sticker to reposition it lifted off the adhesive making the surface lumpy and unacceptable. 

Something different about these stickers - Using no water allowed for some lifting and repositioning! 

They still grab so be careful when initially setting them on the model surface.

You may have an older Aerotech kit, the stickers might work fine when dipped in water. 

TIP: Test using water on some of the blank scrap material between the print images.

   

It helps to dry position the fin stickers.

Don't peel off the backing yet!

Here is a roll of masking tape on the back of a fin panel.

The decal is dry positioned on the fin and the tape pressed to hold it in place.

With the sticker set on the fin - 

Use some small pieces of masking tape to "frame" the sticker centered on the fin.

Lift the sticker panel leaving the tape frame in place.

Peel off the backing and set the sticker on the fin using the masking tape frame to position the sticker.

Smooth out the sticker from the center to the outside edges.

With any luck the other fins should be centered (even white borders) and mirror each other.

Estes AMRAAM AIM-120 Downscale, Build, Part 9, Launch Lug & Conduit Gluing

It'll be hard to reach the root edges once the wide conduit/tunnel is glued on. There isn't much room for glue fillets.

I decided to lightly smooth the dried glue fillets with 400 grit wrapped around a Q-tip for cushioned sanding. Go easy, it is possible to sand a shallow groove in the balsa. You are just knocking down any roughness.

I applied two fine lines of wood glue so there wouldn't be much squeeze out when pressed in place.. 

The lugs were set down and positioned using long tweezers.

I won't be applying glue fillets to the launch lugs. Sometimes trying to fill the bubbles of dried glue isn't worth the time.

The narrow glue lines were positioned so there wouldn't be any visible glue when the lugs were pressed in place.

The conduit/tunnel was centered between two fins on the opposite side of the engine hook and launch lugs. The older Estes instructions showed the tunnel on the same side of the engine hook. I thought it would be more interesting in launch photos with the tunnel facing out.

Estes AMRAAM AIM-120 Downscale, Build, Part 8, Gluing On The Eight Fins

The lower fins are glued on with the trailing edges even with the end of the body tube.

Standard, 90 degree spacing with the engine hook centered between two fins. 

Sight across the bottom to be sure the opposing fins are in line.

The upper fins are 8.20" from the bottom of the model.

A wrap of masking tape was rolled around the tube to line up the trailing edge corners.

Be careful not to glue the masking tape to the fins or body tube.

Estes AMRAAM AIM-120 Downscale, Build, Part 7, Fin Grain Filling & Reuse Sandpaper TIP

STEP 1

On the left, a lower fin with a brushed on coat of thinned CWF.

On the right, another fin after sanding smooth with 400 grit. 90% of the grain is now filled.

STEP 2

Here's the front and rear fins after sanding down the Duplicolor  filler/primer that followed the CWF. The grain is 100% filled.

Balsa grain filling can be a simple two-step process. After spraying with color coats there shouldn't be any visible grain.

Saving Money!

TIPS: You don't have to throw away sandpaper when if gets loaded up with filler/primer.

Buy a soft brass brush, I got mine from Home Depot.

Brush off the gunk with the brush under running water. Use a circular brushing motion. 

Here's the same three pieces of 400 grit, 

ready to go again!

I wouldn't recommend wet sanding on balsa and Kraft body tubes. Both will absorb water and swell up.

Estes AMRAAM AIM-120 Downscale, Build, Part 6, Engine Mount Assembly & TIPS

Many kits have you glue 20/50 centering rings at 1/2" from each end of the engine mount tube. That doesn't really give enough flex for a spring steel engine hook.

The mount shown here is flipped over with the hook pointing up.

TIP: I've found the best position for the low, bottom ring to be 7/8" from the bottom of the engine tube. This allows enough flex to slide in a motor.

TIP: This is a brilliant way to lock in the Kevlar line comes from the older Semroc kits.

The Kevlar line gets a small overhand knot.

This is slipped under the upper bend of the engine hook.

In the picture, the upper centering ring has not been glued in place yet.

The upper centering ring is slid up and glued on slightly over the Kevlar loop.

The centering ring also locks the upper bend of the engine hook in place.

TIP: In all my new builds, I am incorporating heat shrink tubing over the Kevlar line for extra protection. The heat shrink tubing idea comes from Rick Randoll of New Way Rockets.

Estes AMRAAM AIM-120 Downscale, Build, Part 5, Making The Conduit

Here's a blow-up of the front of the tunnel.

The tunnel shape is flatter than I thought, not just a half circle.

Here's what I came up with, as close to the front taper as I could make it.

This is the back end and will be even with the end of the tube.

The small inset picture shows the cross section shape.