Estes Saturn 1B, #7251 Build, Part 8, Adhering Low Wrap

The 3M 77 adhesive will hold the wrap down, but the joint seams can lift.

I squeezed a drop of medium CA glue onto some scrap cardboard. A toothpick was dipped into the CA glue and transferred, directed down the seam edge. 

Immediately (before the CA glue can set up) a burnisher was pressed down the seam to seat the edges.

The butt joint seam is sanded with 400 grit wrapped around a soft cotton Q-tip. This gives you cushioned sanding.

A fin will be glued over and cover most of the seam. Pay attention to the low end of the seam which you can see on the finished model.

With the wrap lined up with the top of the body tube, there might be a little overhand on the back.

This was trimmed off with a sharp knife, then sanded flush with a sanding block. 

Build time:

Adhere Low Wrap: 20 minutes

Total build time so far: 6 hours, 5 minutes

Estes Saturn 1B, #7251 Build, Part 7, Fitting Low Wrap

The instructions say to trim off the bottom of the lower, narrower wrap to 1/32" below the corrugations.

The top picture is the before - I've marked the 1/32" cut with pencil lines.

Below is after the cut. Use a straightedge and a new, sharp knife blade. 

The ends are trimmed to 3/16" from the start of the corrugations. I left mine long before marking the butt joint with pencil.

The first cuts are long, a slight overlap still exists. 

I'd rather sand the edges to size with a sanding block until the ends meet up.

The wrap is flipped over and taped down to a piece of scrap cardboard for a spray of "77" adhesive. In the picture, under the wrap - Roll tape into a small loop, sticky side out.

I prefer the 3M 77 spray. It allows for lifts and repositioning before a more permanent bond sets in. Chances are very good you will need to lift the wrap and try a second time to get it to match up at the joint ends.

EDIT: Before using any adhesive (Spray adhesive or Super Glues (CA glue) on a vacu-form wrap, check to be sure it is compatible. Save some of the border scraps and test first!  

Build time:

Fit Low Wrap: 20 minutes

Total build time so far: 5 hours, 45 minutes

Estes Saturn 1B, #7251 Build, Part 6, Fuel Body Tubes Primer/Filler

I did dry fit the fuel tubes in scalloped tank shroud.

This is one of the best new parts in the kit! A very good fit.

The eight fuel tubes needed a shot of Duplicolor Filler/Primer after the CWF was sanded to surface.

I had to shoot all these side by side then turn the tubes and hit the backside that didn't get covered by the first shot of filler/primer

If you do it right, this two step fill (CWF then filler/primer) should fill the body tube seams.

The filler/primer is lightly sanded with 220 grit, then smoothed with 400 grit.

TIP: Notice my left hand index finger in the end of the tube. This acts as a "bumper" and protects you from rolling over and sanding the tube end round. 

On the left is a fuel tube sprayed with filler/primer.

On the right is another tube after sanding off the bulk of the gray filler/primer.

Build time:

Spray & sand tubes - 1 hour, 20 minutes 

Total build time so far: 4 hours, 55 minutes

New, Improved Estes Starters?

Estes sent me some of the new Uupcoming "more energetic" starter (igniters) to test.

I brought some of the new Starters to the L.A.S.E.R. group launch on October 18. One pair (two igniters joined by the paper tab) was handled out to club members.

The L.A.S.E.R. group doesn't have a large club launcher, but uses individual Estes Electron Beam 6 volt controllers. We didn't have much luck with the new starters. It could have been weak batteries. One of the controllers gave us problems throughout the day.

I decided to do a home test using my Electron Beam controller with new batteries and three different kinds of Estes igniters - the older black, the current clear tip and the upcoming dark gray tip.

Below are three of six tests. The first three were tried before these were recorded. I had similar results on the earlier tests. 

   

This is an animated GIF of the older black tip igniters.

The black tip on this igniter wasn't very large.

This is one of the currently available clear tip starters.

The clear tip took a little longer to glow. 

A small flame and not as large as the older black tip igniters.

The new dark gray tipped "G2" igniter.

While not as "sparky" as the original black tip igniter, the flame ball looks to be a little larger. 

Estes Saturn 1B, #7251 Build, Part 5, Engine Mount Finish & Fin Prep

TIP: If you place the centering rings as shown in the instructions, you might add a drop of glue over the top of the engine hook bend slit. This is an "old school" thing, seen on instructions in the 1970s. 

The finished engine mount.

The new fins are molded of hard plastic, a great improvement over the old Centuri style vacu-formed fins. 

Notice the leading edge tip on the upper left hand side of the picture. TIP: Be careful around that tip - It is very sharp and can stick your fingertips.

There are some subtle mold seams on the outside edges of the fins.

I did sand and smooth off the lines with some 400 grit on a block.

Build time:

Fin Seam Prep - 35 minutes

Total build time so far: 3 hours, 35 minutes

Revisions to the F-18 Hornet Prototype

Trying to design a stable model rocket from a jet will present some compromises.

The two jet engines extend beyond the back end. The front of the intakes are a partial circle. The back of the tubes are full circle and notched to overlap the end of the main body. 

Four tries (and 40" of scrapped BT-5) gave me a workable design. These tubes might also help stabilize the model.

On the next prototype the engine hook will be on the top side, away from the BT-5 tubes.

You might notice the underside of the BT-50H is rough. I've cut off four intake tries and had to sand off some glue.

The decal draws are turning out very well!

Estes Saturn 1B, #7251 Build, Part 4, Engine Mount

There will be some posted steps that might seem out of order from the instruction sheet sequence. I tend to prep some parts before they come up in the assembly steps.  

Here's all the engine mount parts.

Pretty standard, at the top is an 1" orange spacer if you use the D12-3 engine.

You are directed to make a slit for the top bend of the engine hook at 3 3/8" from the bottom of the tube.

Note the engine block will end up recessed 1/16" from the top of the tube if the slit and top bend of the hook are at the 3 3/8" mark.

There were turned in burrs on the inside edge of the centering rings. These were lightly sanded for a smoother slide over the engine mount tube.

TIP: The instructions don't mention it, but I prefer to glue the top centering ring just over the top of the engine hook.

Here you can see the recessed engine block glued in and resting on the top bend of the engine hook.. 

Under my drawn pencil "box" is a recess cut into the inside of the ring.

Gluing the ring over the engine hook can prevent the hook from tearing the engine tube and loosening up.

Normally I'd glue the top ring overlapping the engine hook and tube slit, but these builds were glued up per the instructions.

Build time:

Engine Mt. Assembly - 30 minutes

Total build time so far: 3 hours