New Way Lunar Jumper Build, Part 9, Launch Lug & White Undercoats

After all these years, I'm not doing glue fillets on either side of the launch lug. Too many bubbles and too much time sanding the fillet smooth. 

I know, a smooth glue fillet is less drag. But, I'm a sport flier, not that concerned with a few extra feet of altitude.

I apply a fine line of glue and even it straight with my fingers. Pinch your thumb and index finger into a "V" and run it down the glue line making a narrow, straight line.

A balsa spacer is supplied to set the the lug height.

The upper ring tube is sprayed off the model. 

It's difficult to get paint inside the assembly if the ring is glued on now.

Here the ring is set on a painting wand to a wrap of tape, sticky side out.

Hold the tube areas under a bright, reflective light to se the glue fillet lines that might need sanding.

After fine sanding with 400 grit, 

The glue fillet high spots have been taken down. Most all of the rocket body has been lightly sanded, just dulling the gloss white.

New Way Lunar Jumper Build, Part 8, Tube Fins

While the tubes were still separate,

The edges got a wipe of CA glue. 

Sanding with 400 grit followed.

Using my aluminum angle, 

A pencil line was drawn down all the six tubes.

A glue line was applied down the lower half of the BT-5s,

Pres into the BT-20 tubes lining up the pencil lines.

Here's how the tubes look from the rear, the bottoms are flush.

Apply a line of glue down the pencil lines running down both tubes.

Press into the outside edges of each fin.

Visually center on the pencil line.

New Way Lunar Jumper Build, Part 7, Tube Marking

The fin marking guide matched up!

Mark the three fin lines and extend them the entire length of the tube.

On the body tube, the root edge gluing line was scraped for better adhesion.

The small upper fins are glued in place.

The masking tape wrap helps line up the leading edges.

The short tube was slid over the upper rib fins, no glue yet. 

This applied pressure to hold the small fins in place as the glue dried.

I thought the upper tube would completely cover the outside edge so it wasn't filled and sealed earlier. There was bare balsa below. I applied some CWF and sanded.

The dowel joint got some CWF to fill the gap.

The first coat shrank a bit. After sanding a second application of CWF totally filled the joint.

New Way Lunar Jumper Build, Part 6, Bags & Dowels

After losing a few parts over the years,

I keep like kit parts in small zip-lock jewelry bags.

Fins, launch lug and dowels in one, all the tube details in the other.

You could put the dowels in a drill and spin them against sandpaper to round the upper end. But, you run the risk of scaring the dowel sides in the drill chuck.

I spin the dowel ends against 200 grit on a sanding block. It's not difficult, just takes a few minutes.

The dowels are glued into the notch on the outside edges of the fins. Pressing the two against the flat sanding block insures the dowel is glued on straight.

I thought these fins were a little thick for 3/32" balsa stock, but they are the same thickness as the dowel diameter.

New Way Lunar Jumper Build, Part 5, Balsa Fin Filling

There are three extra small forward fins. 

Only three are needed for the build.

After filling with CWF and sanding to surface - 

The outside edges of the fins were masked with a strip of tape for the filler/primer sprays.

All the fins and tubes were taped down to scrap cardboard for the filler/primer spraying.

After drying, the pieces were lifted and flipped over to spray the other side.

The long BT-50 main airframe tube was sprayed with filler/primer.

The paper towel stuffed in the end blocks any paint from getting inside the tube.
 

The same tube after sanding with 400 grit. You can see the gray primer left in the seam filling what was left from the earlier CWF pass.

I do a two step fill - 

1. Brush on one coat of thinned Carpenter's Wood Filler, let dry and sand to surface. 

The surfaces are not yet sealed. CWF is water based.

2. A fairly heavy spray of filler/primer. Let dry and sand to surface using 400 grit. The filler/primer soaks in a bit and helps seal the surfaces.

You should now be ready for color coats.

New Way Lunar Jumper Build, Part 4, Balsa Fin Prepping

After removing from the laser cut balsa sheet,

here's the fin tips with the fins set side by side. The trailing edges are even.

Cut off the uneven front end square with a razor blade.

All laser cut fins are a "wedge" cut. The bottom surface cuts are wider than the top as the laser light is diffused while burning thru the balsa.

I always square up the fin edges holding the sanding block at a 90 degree angle to the flat face of the fins.

Here the sanding and squaring up is about half done. You're finished when the ash is sanded down and the lighter balsa shows across the edge. 

The fin leading and trailing edges are not rounded.

The trailing edge is cut in a round arc.

To sand it, wrap some 400 grit around an engine casing or whatever form you have that is round. I'm using a glue stick casing.

New Way Lunar Jumper Build, Part 3, Engine Mount & Shock Cords

The engine mount assembly is standard. A slip over coupler holds down the middle of the engine hook.

Here, the Kevlar line is tied beneath the upper plywood centering ring.

There isn't much space between the outer BT-50 and BT-20 engine mount tube. A larger square knot could bulge out the BT-50 tube wall.

I used an overhand knot, but rolled the Kevlar over and under the wrap 4 times. This still allows the wrap to be pulled tight and keeps the line close to the engine tube.

The wrap is set into the wet glue centering ring fillet. The loose tail is cut off and also set into the glue fillet.

The picture to the right shows the heat shrink tube slip down to the top of the ring, protecting the Kevlar line. 

The short shrink wrap is slid over the tied knot joining the elastic and Kevlar line.

Near the elastic, be careful with your heat gun - 

TIP: Using the low setting on my heat gun, the elastic started to melt!

I had to cut off the old knot and re-tie the elastic and Kevlar. I might tie an additional piece of elastic to the shorter line joined to the Kevlar.

The second time, I kept more distance between the heat gun and the heat shrink tube.

Second try was good! (Maybe that's why two pieces of tubing were included.)