Estes Apollo Little Joe II Build, Part 18, Nozzle Gluing

I used Plastruct Plastic Weld plastic solvent cement.
This was one of the plastic cements recommended in the TRF builds.

In a blog comment, Metalhead 1986 gave some sound advice:
"I'm sure you know, but if your readers are not familiar with these types of adhesives, they are meant to be used with the parts pressed together and the brush touched to the joint. Capillary action will draw the glue into the joint, dissolve the plastic, and complete the "gluing" when the plastic re-solidifies as one piece. The included brush is useless for all but the most basic jobs. Any fine work, like this, and the Tamiya 1/16 RC tanks I build, will require a more precise brush to get the solvent just where you want it. When I build my next LJII, this is what I will use.



I very lightly sanded the nozzle side with the holes to make it flatter. This takes down any flash off the sides and can actually give a cleaner glue joint.
You can't sand the pin side with the raised inside edges.

First I applied glue to the inside edges of the hole side piece. The two halves were pressed together.

After that I brushed more glue down the joint on the inside.




On the left is the nozzle after the glued dried. The seam joint is very tight.

400 grit was wrapped around a dowel and the seam sanded. On the right the seam is pretty much gone!

Estes Apollo Little Joe II Build, Part 17, Fin Support

Here's the final stick size - Your fit may be different. Cut a little large and fit to your model.
The overall length is 2 11/16" with the taper starting 1 5/16" from the end. The tapered end to the right fits into the fin cavity.




The instructions don't mention it but imply the rear centering ring is even with the end of the body tube.
On the actual Little Joe II the nozzle plate was slightly recessed. I could build up the inside so the rear centering ring is closer to the bottom of the tube but will probably leave it as is.
This picture was posted by John Pursley in the TRF build. 

I'll be following John Pursley's advice and make the nozzle plate and centering ring removable. Some flights have shown some melting of the plastic nozzles.

With the rear centering ring against the square fin supports it's a very strong assembly.

Again I can't take credit for using a fin reinforcement spar. The master modeler's at The Rocketry Forum - George Gassaway, James Duffy and John Pursley figured out the structural improvements.

The fins are probably fine without the stick reinforcement. I've read a few launch reports where a fin has been knocked loose from the corrugated wrap on a hard landing. Plastic to plastic bonds between the fin and the body are sometimes a problem.

Estes Apollo Little Joe II Build, Part 16, Fin Support

I used a new #11 blade in my X-Acto. You'll be cutting through the body tube and wrap plastic. My usual break-off blade knife wasn't used for these cuts.

Note the knife tip position set into the corners. I punched through all eight corners and then cut through the centers. This way the back of the knife worked like a "stop" and prevented me from cutting outside the square.


I cut a little inside the drawn square and then trimmed it to a friction fit of the stick.

After cutting one square I checked the fit of the fin position. All was good so the back edge was measured. Using the 3/16" square stick, the rear of the cut square was 9/32" from the back edge. The other three squares were marked and cut.

Note the engine mount was slid in to support the tube during the square cutting.

The inset shows some of the tube pushing in around the stick. I wanted a fairly tight fit around the support stick.
On the left is a pencil mark where the stick will be cut to glue to the engine mount tube. This will be cut slightly long and trimmed to fit.

Estes Apollo Little Joe II Build, Part 15, Fin Support

Well, I left out the post on the Fin Half Gluing. I've re-numbered the blog posts, scroll down to see a new post at #13. Everything should be in the correct order now.

The Little Joe II fins are surface glued on a vacu-form wrap, probably not the strongest joint. In post #229 of the TRF build, John Pursley showed an improved fin reinforcement. CLICK HERE

The first time he used a tapered wood dowel that went in the fin interior, through the body tube and glued to the side of the engine mount tube.
This revision used a square stick, Much stronger and the flat side lays against the right centering ring below it.
This allows the model to be flown without the nozzles if the lower ring and nozzle assembly is not glued in. Some flight reports have mentioned some melting of the plastic nozzles.The four square sticks will be very strong and also center the engine mount tube without the lower ring in place.

John Pursley used a 1/4" square stick, mine was 3/16". The length to start is 3" long. It'll be trimmed to fit later. Right now I'm just trying to get the taper to fit the inside of the fin.

The inside taper starts about 1 5/16" from the end.

Held up against a light you can see stick inside. It won't go all the way to to the outside edge. Don't press too hard or you could split the fin right down the glue line.

Fit the fin without the stick and you'll see the back edge is slightly above the end of the wrap. Take this into account when marking for the stick cut.

Rough up the wrap inside the fin guides with some 400 grit. A pencil won't write on the smooth plastic.
Press in the stick and set the fin on the body sideways. Trace the top and bottom of the stick with a pencil.

Estes Apollo Little Joe II Build, Part 14, Better Fin Fitting

This shows a dry fit of one of the fins. The fit against the corrugated wrap is good but could be better.

In the TRF builds, George Gassaway brought up a good point. On the inside edges of the fins are some raised circles. These are "ejector pads" from the molding process.

They bump into the tops of the raised guides on the corrugated wrap.
I carefully shaved them down. It's only necessary to remove the inside half of the circle.

Here's the improved fit. It's a minor point and probably not necessary but you will end up with a more contact on the gluing edges.

Estes Apollo Little Joe II Build, Part 13, Fin Halves Gluing

These new fins are very well molded. They fit very tight without glue and take a little effort to separate them!

When gluing these halves I only applied glue to the long, diagonal leading edge.







After the two sides were pressed together, glue was brushed over the outside joint seam. Again, go light.

Apply glue on seam side and squeeze the two halves together.

Additional glue was brushed on the inside.




On the left is the dried glue that was brushed on bottom side of a fin.

The inset picture shows the same fin surface after sanding smooth.
The joint seam is gone! I didn't need any seam filler at all.
The glue is a solvent and melds the glued edges together.

Estes Apollo Little Joe II Build, Part 12, Engine Mount

I sand the ends of the engine block rings flat. It will fit better against the upper bend of the engine hook.

I know - moot point.

The engine block is about 1" down inside the top of the tube. Apply a ring of glue using a Q-tip or dowel.

TIP: Slide the engine block in place using a 24mm engine casing. Sometimes engine blocks can go in at a slight angle. The casing will help keep it straight.







The top centering ring is glued in place. It is not even with the end of the tube, but about 1/16" down from the top edge. This allows better glue fillets on both sides. In this picture the top ring is down.
I'm not gluing the lower ring (with the nozzles) on the engine tube.






Here's the finished mount, the lower ring (closest with the nozzle holes) is not glued on yet.