Estes Semi-Scale Saturn V, Kit #K-39, Part 5, Cutting The Fin Slots

I used a new blade and my aluminum angle to cut the fin slots.

The masking tape wraps made it easier to see the start and stop points.

After the initial scoring the cuts were about half way through the tube walls.

I thought I was cutting on the lines. The slots ended up too wide. The fin root fit was too loose for me.

I got another BT-60 tube out of my spare parts.

This new tube needed seam filling with CWF then filler/primer.
 

Two of the four fin slots had a good fit around the clear fin material.

The other two slots were still too loose!

I had to get another length of tube, mark and cut the slots a third time!

Estes Semi-Scale Saturn V, Kit #K-39, Part 4, Marking The Fin Slots

The instructions have you glue in the engine mount then cut the fin slots. You are warned to "cut lightly" because the clear tube is underneath.

I decided to cut the slots before gluing in the engine mount. It takes some pressure to cut fin slots.

Here's how the kit marking guide fit the tube.

GOTCHA: The ends did not fully meet.

Notice the faint pencil lines above the cardstock mount. After marking for the fins, I rotate the guide 90 degrees to see if the four fin spacing is correct. That pencil line to the right is off by almost 1/8"!

I went to payloadbay.com and printed off a marking guide, four fins on a BT-60 tube. This was wrapped and the four fin positions marked.

The original kit marking guide was wrapped on again, and each individual fin was marked for the fairings. 

The kit guide had to be slightly rotated to each correct fin line to mark the A fairing locations.

Estes Semi-Scale Saturn V, Kit #K-39, Part 3, Engine Mount

Cutting the coupler a little oversize allows you to sand to fit.

On the left, one side of the coupler cut size is sanded on a block with 220 grit.

On the right, clear tape holds the ends together with a good, slip fit.

Here's the finished engine mount. 

The clear coupler is held in place between the upper two centering rings. There is no glue holding the clear coupler to the rings.

The kit didn't include and engine block, I added one.

Before cutting the fin slots, the tube seams were filled. 

These older tubes had very tight, almost invisible seams. It only took one good shot of filler/primer and sanding to fill them.

On the left, a paper towel is wrapped around a painting wand for a better fit inside the BT-60. On the right, an inside wrap of tape keeps out the filler/primer spray.

Launch! Orlando R.O.C.K., January 3, 2025

Some days are good, this wasn't the best!

My Estes TWIN FACTOR was launched with a A10-0t booster to an A3-4t sustainer.

As all my two stagers seem to fly - First stage is vertical, Second stage turns to 45 degrees! I got both stages back, there were some burn holes in the booster tube and the rear engine block was gone. 

This one is probably retired, the booster anyway.

The BT-50 based AMRAAM was my best launch of the day. 

I'm starting to use some of many Quest Q-jets B4-4s picked up over the past few years. 

I would guess 450 feet with a good walk to pick it up. My dog Dakota went with me to recover it.

Another Q-Jet B4-4 was used in my Quest X-15.

It wobbled during boost to 350' and drifted into the trees - Lost!

I had 17 previous launches on this one - 

My best launch shot of the day goes to Gary Dahlke's Extreme 12.

I believe it was a D12-0 to an A8-3. A smart choice considering the field size and the increasing winds.

Finish out the day with a bang! I usually have a MicroMaxx rocket ready.

This is the Rocketship Games HAWKEYE downscale.

It performed well, topping out at nearly 100'. I wish I had installed a streamer. I drew a bead on the landing area a found it after a few minutes.

Only four launched - 

The X-15 was lost and the Twin Factor booster is fried!

Not the best day, but they all can't be perfect.

Estes Semi-Scale Saturn V, Kit #K-39, Part 2, Engine Mount

About 3/16" of the inside of the motor mount tube got a wipe of CA glue applied with a Q-tip.

Never apply CA glue where a wood glue joint will go later. Wood glue needs to soak into the surface. CA glue seals the area where it is applied.

The instructions say to cut a 1/8" square notch in a centering ring.

I used my rotary punch to cut a half circle for engine hook movement relief.

The upper ring got a slight recess cut for a better fit over the engine hook.

Instead of cutting out a 1/8" slice from the clear oversize coupler, cut a single line. Use an aluminum angle (set inside) for a straight cut line.

Slide the coupler in the BT-60 and check the overlap. Mine was a little less than 1/8" wide. Mark and cut the second line a little oversize. Final fitting in the next post.

GOTCHA: When testing the fit of the clear coupler, I found it was cut uneven. One side was longer than the other by about 1/16". If used as supplied, the third upper ring would sit at an angle when butted up against the coupler top. The long side was sanded so all sides were the same length.

Estes Semi-Scale Saturn V, Kit #K-39, Part 1, Parts

All the parts:

The tubes are tight and strong, almost no seams! The longer, lower body is a BT-60, the upper tube is a BT-52.

The 1/12" diameter dowels are used to make the tunnels and ullage motors.

The printed wraps remind me of the old Estes Mercury Redstone capsule wrap.

The cardstock shrouds, fairings and tube marking guide.

The self adhesive "fins" are faded, almost gone!

These will have to be redrawn and printed.

Apparently, Estes didn't get an order of clear couplers that could slide into the BT-60 for fin attachment. The enclosed coupler is the same diameter as the BT-60.

The addendum instructions have you cut a strip out of the coupler and rejoin with clear tape!

Estes Semi-Scale Saturn V, Kit #K-39, Background

Let's start the New Year off right!

The "practical size" Estes semi-scale Saturn V was introduced in 1969 and available through 1979.

I had assembled this model in the early 1970s, remembering some confusion about the clear plastic fins. This might have been the first kit to incorporate thru-the-wall fins!

The catalog picture at the right doesn't mention or show clear fins.

The engine mount coupler was clear plastic. The root edge of the fins were adhered to the internal coupler through thin slots cut into the BT-60 main tube.

Small self-adhesive paper fins were stuck onto the the permanent clear fins. This was a smart work around considering the clear fins and fairings.

There were small half dowels adding tunnel, fairing and ullage motor details.

The build starts tomorrow!