Sirius Saturn V - Build Thread

[Quaranta]

Preparing for Main Body Assembly:

Components laid out in approximate relative position.

6" Body Tube
Motor Mount Assembly
3.9" Body Tube
Forward 6:3.9" Centering Ring

The plywood ring shown aft (with 5 predrilled holes) is the Bulkhead Plate used to mount the (5) F-1 Engine Nozzles for display. This is obviously removable. I included it in the photo as I need to use it to position the motor mount assembly. Addition of the AeroPack MRS requires the MMT to be slid forward a fraction of an inch in order for the Bulkhead Plate/F-1 Display Cluster to fit without modification. This in turn will require shortening of the 3.9" tube a fraction to stay to scale.

Careful measuring ahead...

 

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MMT Assembly Test Fit / Measurement:

The pencil line inside the aft end of the 6" body tube marks the nominal rear position of the Aft Centering Ring. Addition of the AeroPack MRS results in the Aft Centering Ring being moved forward 27/32".

(this does not mean I trim the 3.9" Body Tube by that amount, as the Aft Centering Ring was also moved forward on the 38mm engine tube. More careful measuring ahead...)

I plan on Fiberglassing the exposed inner surface of the 6" Body Tube and Aft Centering Ring for reinforcement

 

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3.9" Body Tube marked 10.9" back from leading edge. This reference line needs to align with the forward edge of the 6" Body Tube.

 

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Test Fitting For Measurement:

MMT Assembly placed in 6" Body Tube in preparation of fitting the 3.9" Tube. The 3.9 " Body Tube is then mated.

 

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MMT Assembly and 3.9" Body Tube slid aft to final position:

We can see the reference line is "too far forward" (as we knew it would be)

 

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Tube marked to allow measurement of length of discrepancy. It's 1/2" too far forward.

 

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Base of 3.9" tube marked at 1/2" and the cut to shorten tube.

Now ready for permanent assembly.

 

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Epoxy MMT Assembly to 3.9" Body Tube:

I used 30 min epoxy to allow a little working time and used the 6" Body Tube as an alignment jig.

Once set,... I removed the MMT/3.9" Body Tube and added an epoxy fillet at the joint between the forward centering ring and the 3.9" Body Tube. The 3.9" Body Tube serves as the ejection chamber for 'chute deployment, so I wanted to insure a good ejection charge seal.

 

[JAL3]

Can you tell us the size of the launch lug?

Since it is internal, how long of a rod can it accommodate? My guess is that your motor will really have to have some kick to get it moving fast enough before leaving the rod. Are slow liftoffs possible?

I am really enjoying this thread. Thanks for posting.

 

[troj]

Tube marked to allow measurement of length of discrepancy. It's 1/2" too far forward.

So you do partial assembly, then have to measure to get the final length and finally, cut to length?

Scratching head on this one....

-Kevin

 

[Quaranta]

Can you tell us the size of the launch lug?

Since it is internal, how long of a rod can it accommodate? My guess is that your motor will really have to have some kick to get it moving fast enough before leaving the rod. Are slow liftoffs possible?

I am really enjoying this thread. Thanks for posting.

The internal launch lug is a brass tube 14" long by slightly larger than 1/2" ID (17/32" vs 35/64" ID). The launch rod will pass internally until it hits the forward centering ring (at the S-II/S-IVB transition). Results in approx 37 1/4" of launch rod length.

Instructions call for a 1/2" launch rod x 48" length.

The recommended motor is an I-284.

 

[Quaranta]

So you do partial assembly, then have to measure to get the final length and finally, cut to length?

Scratching head on this one....

-Kevin

This is because I chose to add the AeroPack Motor Retention System and wanted the F-1 Nozzle display cluster to fit in place w/o mods.

The nominal design calls for the engine tube to end flush at the rear centering ring. Adding the AeroPack MRS results in the engine tube extending behind the Rear Centering ring (so the MRS has something to attach to), and then the extra length of the MRS H/W adding some length to the entire MMT assembly.

Since I want the F1 display cluster to fit,... the MMT assembly gets pushed further forward in the 6" body tube. I could have slid the forward centering ring on the MMT assembly rearwards to account for the shift, but chose to shorten the 3.9" tube instead.

A lot of trouble for the AeroPack MRS I suppose... But I like the way they look. very clean and "engineered".

Did I explain that clearly?

 

[troj]

Did I explain that clearly?

Yup! Makes complete sense -- thanks!

-Kevin

 

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The Main Body Assembly as been epoxied. Some photos...

The "down the pipe" shot shows the parachute bulkhead, and the cable shock for harness.

 

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A few shots of the the business end.

Since the Aft Centering Ring is relatively far forward, I'm going to reinforce the aft end with fiberglass.

 

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Two Astronauts...

 

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To reinforce the hind end I'm going to use:

(1) 2 layers of 2 oz glass over the rear centering ring with the fiberglass cloth extending up (down) the flange. The flange section of cloth will be radially cut. This will provide 2 layers of glass covering the Aft CR and extending contiguously up (down) the flange.
(2) 1 layer of 6 oz cloth around the flange only.
(3) West Syst Epoxy Resin

Here's the template for the CR glass sheets. The 6 oz flange layer will essentially be a 1.25" strip approx 19" long (2*pi*R for a 6" Diam)

 

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Fiberglass cloth prepared.

Will need to tape up the launch lug,... and the AeroPack MRS. Then I can lay the resin.

 

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2 layers of 2 oz cloth laid in position.

The MRS has been taped. The launch lug is sealed with a cork stopper. I ran a bead of 5 min epoxy around the cork to seal it and prevent the thinner west epoxy running down the lug if the seal wasn't perfect.

 

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West 205 epoxy resin / slow hardener applied.

I applied a coat of resin with a brush and mixing/fillet stick to the 2 layers of 2 oz cloth, and got it seated properly. Then I immediately added the 6 oz cloth to the 1.125 inch exposed flange ( inner surface of the 6" body tube). Only a bit more resin was required after using 2 mixing sticks to squeegee it against the tube wall.

Pics taken with resin wet. I let the resin sit for 30 min. When just starting to cure, removed the MRS masking tape.

I'll drill / sand the cork out after the resin cures.

 

[gdjsky01]

With the added thickness of the FG you will have to sand down the display bulkhead, no? There does not seem much between the edge and the F1 mounting holes.

 

[Quaranta]

With the added thickness of the FG you will have to sand down the display bulkhead, no? There does not seem much between the edge and the F1 mounting holes.

Yes. I'm guessing I added about 3/32". Once the glass cures I'll test the bulkhead. 100% sure it'll need sanding. I'm hoping I can leave the F1 nozzle mounting holes as is. I may have to sand the pin where the nozzles penetrate the bulkhead. Worst case I'll re-drill them inboard a fraction.

I'm building this as a flying model,... so I'm less concerned about the display cluster. But while thinking it through,... I'm pretty confident that I won't have to do anything beyond a bit of sanding (I am planning to add 4 sections of dowel to serve as struts between the bulkhead and the Aft Centering Ring.)

 

[Quaranta]

Jeff,

I pulled out the display cluster parts this AM. The F-1 Nozzle mounting pins will need a bit of trimming to match the reduced diameter of the bulkhead ring, but the engines have a large flat surface to serve as the attach point to the bulkhead,... so I'll be able to get away with only sanding the bulked ring and the trimming F-1 nozzle pins.

Simon

Here are the display cluster components...

 

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Detail photos of the F-1 Nozzle.

 

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F-1 Engine Assembled.

 

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Fiberglassed aft end of the 6" Body Tube sanded flush. Cork plug removed from launch lug.

 

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Turns out, the fiberglass added about 1/16" all around, except where I overlapped the 6 oz cloth for 3/4 inch. Here it's about 3/32" thick. To sand the F-1 Display Custer Bulkhead, I dew 2 concentric circles... 1 at 1/16" to mark my "sand to" line. And an inner concentric line just to give my eye a reference line.

To rough sand circles... I use a pin in a piece of wood to create a rotation axial. I have a bench top disk/belt sander where with the exact axial size, a perfect circle can be made easily,... but since this bulkhead is hidden inside the base of the rocket, and since the FG isn't a perfect circle it was easier to use the hand sander.

 

[gdjsky01]

Nicely played sir! :clap:
- Jeff

 

[Quaranta]

Nicely played sir! :clap:
- Jeff

Thanks. Luckily, I had thought about it ahead of time.

 

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Body tube marked in 5 locations for application of body wraps.