Estes Time Warp Build, #7321, Part 11, Lower Fin Gluing

My plan was to spray the BT-5 cluster tubes - just the tight areas at the center.

Notice the centering rings and upper tubes between the rings has been masked off.

I ended up spraying more of the tube surface and the area where the main fins will be glued.

I sprayed the yellow fin tip (front and back) yellow before gluing the fins onto the model. On the left is the white undercoat, on the right is the yellow. 

Yellow paint was sprayed on the outside face and underneath into the fillet area.  

I tried to concentrated the yellow paint to just the inside areas between the tubes but the spray covered a wider area. 

The glue line (fin root edge contact area) was marked and the paint sanded off down to the tube.

Here's the gluing line sanded down to the white tube.

Keep the sanded area narrow so it will be covered by the width of the root edge.

The fins are a bit difficult to place, they want to fall off when gluing, like on the Gyroc and Orbital Transport. 

On the right, the fins are in place and filleted with white glue. 

Pre-painting will make masking the black easier and gives a consistent  yellow coverage. Those inside areas would be difficult to spray if all were glued together.

Estes Time Warp Build, #7321, Part 10, Upper Fin Gluing

The scratched fin glue line was slightly widened using the side of a diamond file.

Note the masking tape. That's the stop point so the scratch stops before the top of the root edge of the fin. 

The lower tape is the top of the launch lug glue line.

The glue fillets are done with white glue. The white glue dries clear, yellow glue would dry yellow.

The white glue also dries with a flat finish. To gloss it up, I applied some clear acrylic using a Q-tip. No masking here - 

The inside lip of the BT-55 got a wipe of super glue then light sanding with 400 grit.

The brown edge was "painted" gray with a second Q-tip.

Estes Time Warp Build, #7321, Part 9, Upper Fins

The upper fins were filled with CWF and sanded. Then, filler/primer and sanding with 400 grit. Two steps and the balsa grain is filled.

I'll be painting these upper fins off the model. This will save some masking. The upper fins won't break off as the lower fins take the stress on landing.

Estes got it right!

The fin marking guide and alignment drawing are on a separate page of the instructions. There is no printing on the reverse side. You don't have to cut up an instruction page - no build steps on the other side - 

The fin marking guide matched up perfectly.

I wouldn't normally glue fins on this way and wouldn't recommend it for the occasional builder. This will not give you the strongest glue joint. 

The BT-55 mid tube was already seam filled and painted dark gray.

A fin glue line was scraped using an aluminum angle and the tip of a diamond file. Be sure the scraped line is shorter than the top of the root edge length.

Estes Time Warp Build, #7321, Part 8, Scattered Steps

I'm always apprehensive about using pre-made parachute shroud lines.

These broke with a good tug!

I cut them off the chute and replaced them with #10 embroidery thread.

Plastic nose cones and adapters take longer to dry between paint coats.

I waited three days before spraying the yellow and the paint wrinkled!

Sand smooth, wait four days and spray again!

Here's the new Estes self-adhesive shock cord mount.

It's a simple knot, I left a loose tail for some extra insurance.

I'll be checking the adhesion of the mount after a few flights.

Older rocketeers might remember the problems with the Centuri self adhesive mounts - 

Initially claimed to be "permanent", they did loosen and pull loose over time. Later kits would include an addendum to the instructions reminding you to burnish the fastener between launches.

Granted - in 1971 we didn't have the 3M tape that is on the back of the new Estes shock cord mounts. Time will tell . . .  

Estes Time Warp Build, #7321, Part 7, Gluing & Filling The Fin Tips

The fin tips and fins had the balsa grain filled and sanded.

Filler/primer and sanding followed.

I used a small diamond file to slightly open up the slots to a friction fit over the fin tabs.

The fin tips are glued on.

There is now gaps around the fin tab joint.

This joint required additional filling,

first more CWF and sanding flat with a block.

The backs of the shield tips are masked and the flat face got a shot of filler/primer and sanding with 400 grit.

Once the fins are glued onto the BT-5 cluster tubes, 

Masking will be tight to separate the black and yellow paint on the inside of the "T" fin.

I sprayed some white undercoat on just the fin tip face and the underside joint.

Notice the root edge is masked off with a narrow strip of tape.

Estes Time Warp Build, #7321, Part 6, Fin Fitting & Fill

The tube seams were filled with CWF and sanded to surface.

The BT-55 had a definite seam, the heavy walled BT-50 was very tight.

After the fin tips were glued together, I tried a test fit on the main fin.

I wish the fin tabs (sticking into the smaller "shield" fin) were longer so you could sand them to surface after gluing them on. With the tabs slightly recessed there is more to fill.

Laser cutting burns through at a slight angle.

Look close at the right side of the root edges.

I sanded and evened the burned edges so they would glue on perpendicular to the body tube.

The fins have laser cut "slots" running parallel to the leading and trailing edges. I decided to leave them in and fill the slots with CWF.

Why leave them in?

The rough laser cut slots would be difficult to fill and sand. The visible edges would be rough. The design is interesting enough without the open slots.
 

Estes Time Warp Build, #7321, Part 5, Upper Centering Ring

Here's the upper laminated centering ring,

glued 1/2" from the bottom of the BT-5 tube cluster.

The instructions say to add glue fillets down and between the three tubes.

TIP: I wouldn't do this, it's a long, deep joint. When the glue dries you'll have bubbles and an uneven fillet.

I used a few drops of glue to fill the small center gap. This will block any ejection charge escape.

Years back we used "tissue/glue putty" to fill gaps like this. Tissue/glue putty is a mix of glue and tissue torn into very small pieces. It makes a strong gap filler.

This gap is small, if it were larger I'd make up some tissue/glue putty.

To read more about this gap filler: CLICK HERE 

This top and bottom glue fill also strengthens the mount.