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-   -   Thor - Agena B (K-28) (http://www.oldrocketforum.com/showthread.php?t=3369)

dwmzmm 05-26-2008 12:15 PM

Thor - Agena B (K-28)
 
I've started the build of my clone of the Estes K-28 Thor - Agena B model, but have a question: What is the correct size of the paper shroud that makes the engine nozzle?

I happen to still have my Estes Tube Adapters kit (TA-1) I got long, long ago, and it has
various sizes of paper shroud possibilities. I was thinking of using the Tapered Shrouds
BT-20/BT-55, but it may be too big. The plans I printed off of JimZ's site doesn't specify.

Any and all help will be appreciated. BTW, about 99% of the parts used to build this model
comes from SEMROC.

Rocketking 05-26-2008 01:20 PM

Re: Thor-Agena Nozzle Shroud
 
Since the CR's used for the Nozzle are 2050's, I would use the 2055 shroud and 'trim back' the shroud by about an 1/8" from the BT55 edge. While it is just an estimate, unless I can lay my hands on a 'plan-pack' (I DO have quite a few, but I don't remember seeing K-28 along the way...), I can't tie it down any closer than that.

Give it a shot. If it costs you a shroud, let me know & I'll send you one. Us so-called 'smart guys' would photo-copy the pattern and cut up the copy. Voice of experience here.

Good luck with your build. Show us what you've got along the way, even if you have to borrow a camera & download cable to do it. It's good for 'Bragging Rights'.

dwmzmm 05-26-2008 01:42 PM

Quote:
Originally Posted by Rocketking
Since the CR's used for the Nozzle are 2050's, I would use the 2055 shroud and 'trim back' the shroud by about an 1/8" from the BT55 edge. While it is just an estimate, unless I can lay my hands on a 'plan-pack' (I DO have quite a few, but I don't remember seeing K-28 along the way...), I can't tie it down any closer than that.

Give it a shot. If it costs you a shroud, let me know & I'll send you one. Us so-called 'smart guys' would photo-copy the pattern and cut up the copy. Voice of experience here.

Good luck with your build. Show us what you've got along the way, even if you have to borrow a camera & download cable to do it. It's good for 'Bragging Rights'.


Thanks, Glen. I was thinking along the same line, but trimming the length by about 1/4".
Judging from the way the nozzle looks in some of the illustrations in the instructions, it's difficult to gauge how long the nozzle is suppose to be.

But thanks about the offer on the shrouds; the TA-1 kit has three of them and I've only used
just one. I'm going to scan and make copies of the others so I'll have the patterns permanently.

More shortly.....

dwmzmm 05-26-2008 02:28 PM

A Few Pics for Starters
 
4 Attachment(s)
A few pics documenting the start of my build. Note in the fourth pic you'll see some leftover plastic tree I'll probably use (if possible) for the two venier nozzles of the Thor - Agena B
detailing.

rocketguy101 05-26-2008 02:35 PM

Dave, FWIW Rockets of the World show the engine bell large diameter on a Thor-Agena A is 47.02 inches. The bell length is 56 inches. The Thor body dia is 96.0 inches. You could scale one accordingly.

dwmzmm 05-26-2008 04:54 PM

Update: More Pics
 
4 Attachment(s)
I was able to determine how much to remove from the nozzle bell to get the correct size;
the Estes' kit specifications states the K-28 kit is 17" long. Putting the nose cone, BT-52,
6052 balsa adapter, BT-60 and the engine mount "dry" (without gluing), and then measuring, 5/16" of the nozzle shroud needed removal. Was able to remove that part of
the shroud without too much difficulty.

Now the build is moving along pretty good. Got the systems tunnel formed and sanded.

Pics of what I've done so far below. More to come as the build progresses.

dwmzmm 05-26-2008 10:26 PM

1 Attachment(s)
Got the systems tunnels on the main body section/adapter and Agena stage. This is working out to be a really fun build!

Will call it quits for the day and resume tomorrow evening.

kurtschachner 05-27-2008 11:40 AM

The kit came with an "SP-28 Pattern Sheet", which had the nozzle template on it. Whether it was accurate or not is unknown. However, I do have a copy of that sheet but it is too late for your build. When I get home tonight I will post a PDF of it anyway and maybe you can compare it to what you eventually used. I know that sheet is missing from JimZ's site.

What are you planning on doing for the fin unit? When I built mine I had a machinist friend make up a mandrel (steel) for me, I then used that to heat form a polycarbonate fin ring. That mandrel is gathering dust in my basement, let me know if you'd like to borrow it. I'll try and post a picture of my fin unit as well as the pattern sheet.

P.S. There aren't very many pictures of S/N 298 but here is a site about the Thor-Agena:

http://www.skyrocket.de/space/doc_lau/thor_agena.htm

dwmzmm 05-27-2008 12:25 PM

Quote:
Originally Posted by kurtschachner
The kit came with an "SP-28 Pattern Sheet", which had the nozzle template on it. Whether it was accurate or not is unknown. However, I do have a copy of that sheet but it is too late for your build. When I get home tonight I will post a PDF of it anyway and maybe you can compare it to what you eventually used. I know that sheet is missing from JimZ's site.

What are you planning on doing for the fin unit? When I built mine I had a machinist friend make up a mandrel (steel) for me, I then used that to heat form a polycarbonate fin ring. That mandrel is gathering dust in my basement, let me know if you'd like to borrow it. I'll try and post a picture of my fin unit as well as the pattern sheet.

P.S. There aren't very many pictures of S/N 298 but here is a site about the Thor-Agena:

http://www.skyrocket.de/space/doc_lau/thor_agena.htm



Thanks, Kurt. We may need to go ahead and post a pattern scan anyway as I'm sure Scott
would like to have it as well.

I have some leftover clear tubing & sheet material from previous projects (Gemini Titan - II
and K-36 Saturn - V) that should be adequate for the Thor - Agena B. I am curious about your mandrel and how it works. Could you elaborate futher?

Also, I've seen the site of the Thor - Agena's you posted (saved all those pics to my hard
drive, too). One question I have is why the Estes version has the nose section painted
black and most pictures I've seen of the real ones look more aluminum or silver.

More later....

kurtschachner 05-27-2008 01:21 PM

I tried making the fin unit like the Estes instructions said (what kind of plastic was that? I used cellulose acetate butyrate) but to little success. The problem was how "springy" the sheet was and how it wanted to pull apart at the joint. Plus, I didn't like the step-up the lap joint caused.

I ended up using sheet polycarbonate (0.020" for the ring, 0.040" for the fins). The mandrel I had made up is the size of BT-60 (I also have one for BT-70). I wrapped the polycarbonate sheet around the mandrel and secured it in place with some shim stock and hose clamps. I heated this assembly in a regular oven to about 300 degrees (above the glass transition temperature) and then let it cool. Once cooled you end up with a nice, round stress-free ring. Too high of a temperature and the appearance becomes mottled (you've melted it) and too low causes it to want to straighten out again.

I then solvent-bonded the ring together using a 10% solution of polycarbonate in methylene chloride - but you can use a commercial polycarbonate adhesive. Lastly I attached the fins to the ring using the same solvent solution. One advantage to polycarbonate is that it's very strong and flexible.


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