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  #1  
Old 08-29-2017, 04:09 PM
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Default [WANTED] Estes ARCAS (K-26) Info

Working on a sim of the ARCAS, and I've got a conundrum... JimZ's scan of the instructions clearly states that the kit uses a JC-55C. The Estes 1971 catalog gives it as 1.3". OR's default gives it as 1.25", and Semroc says that a JC-55C is 1".

When it comes to this kit (the K-26) which spec is correct?

Also need to know more about the fins... Those shapes are pretty complex, and if I can get the length of the fin support pattern, I should be able to scale both fin shapes based on that.

Thanks!
Jim
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  #2  
Old 08-29-2017, 04:49 PM
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Comrade,

Note that the K-26 was a little short scale wise. The "correct" BT-55 length should be 20.24 inches as per Rockets of the World. The JT-55C I have is 1.25 inches, I have a later blue card version but it still has the balsa nose.
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Finishing: Excelsior/Semroc Scrambler; mini V-2
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  #3  
Old 08-29-2017, 04:54 PM
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Quote:
Originally Posted by MarkB.
Comrade,

Note that the K-26 was a little short scale wise. The "correct" BT-55 length should be 20.24 inches as per Rockets of the World. The JT-55C I have is 1.25 inches, I have a later blue card version but it still has the balsa nose.


Thanks for the reply!

You wouldn't happen to have the instructions for your version would you?
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Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.
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  #4  
Old 08-29-2017, 07:53 PM
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Let me look.
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Awaiting First Launch: Bunch of Stuff
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  #5  
Old 08-29-2017, 09:04 PM
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The Estes ARCAS kit was used to produce the original Cherokee-D -- I found these discussions about the nose:

http://modelrocketbuilding.blogspot...art-5-nose.html

http://www.rocketryforum.com/showth...okee-X-nosecone

I always thought is was a secant ogive but according to Carl in the TRF thread it wasn't quite that either...
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  #6  
Old 08-30-2017, 06:38 AM
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D'oh! I just realized something...

To scale a .pdf file when you are unsure of something's scale is to find out something about it that is a constant. In the file from JimZ's site the fin pattern is on the same document as the fin spacing guide. The ARCAS has 4 fins, and uses a BT-55. So, if that's the case... A BT-55 is 1.325" in diameter... Multiplied by Pi, gives us the circumference , divide that result by 4... and you get a result of how far the fins should be spaced (1.04065").

Downloading the image from the .pdf has them at 113 pixels apart

(104x100)/113 = 92.035

The image needs to be reduced by 92%...

And

I've got my fin pattern's dimensions. Sure there's a small margin of error due to rounding, but it's the best I can do.
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Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.
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  #7  
Old 08-30-2017, 08:44 AM
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You know . . . .

You could ask Randy to make a sheet of K-26 fins and mounts. Carl had the pattern on the machine. I know because I have one. Although its not presently on the eRockets site, it wouldn't hurt to ask. . . .
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Awaiting First Launch: Bunch of Stuff
Finishing: Excelsior/Semroc Scrambler; mini V-2
Repair/Rebuild: science fair rocket; rescue K-41
On the Bench: LTV Scout F; Sputnik; Voskhod
Dream Stage: Big R-7
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  #8  
Old 08-30-2017, 12:09 PM
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Quote:
Originally Posted by MarkB.
You know . . . .

You could ask Randy to make a sheet of K-26 fins and mounts. Carl had the pattern on the machine. I know because I have one. Although its not presently on the eRockets site, it wouldn't hurt to ask. . . .


Talked to Randy about the ARCAS today, and he told me that they have a BT-60 based one, and another. I'm just simming this up, and not really interested in a build... yet.
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Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.
Reply With Quote
  #9  
Old 08-30-2017, 05:25 PM
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Randy might be a little confused.

The Estes K-26 ARCAS is BT-55 as you've sim'ed.

Semroc had/has two ARCAS', the KS-8 built on Series 15 tubing for 18mm power and the KS-5 SLS for mid to Level 1 power on heavy-walled BT-70.

If you can find one, BMS made a Peter Alway-designed ARCAS on BT-50 that's fun to fly on 13mm power .

There are others, but these are the ones, I've built.
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NAR 79743
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SAM 062

Awaiting First Launch: Bunch of Stuff
Finishing: Excelsior/Semroc Scrambler; mini V-2
Repair/Rebuild: science fair rocket; rescue K-41
On the Bench: LTV Scout F; Sputnik; Voskhod
Dream Stage: Big R-7
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  #10  
Old 08-31-2017, 04:13 PM
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Quote:
Originally Posted by rocketguy101
The Estes ARCAS kit was used to produce the original Cherokee-D -- I found these discussions about the nose:

http://modelrocketbuilding.blogspot...art-5-nose.html

http://www.rocketryforum.com/showth...okee-X-nosecone

I always thought is was a secant ogive but according to Carl in the TRF thread it wasn't quite that either...


You know, I should have responded to this earlier... I'll chalk up the delay to being sick (food poisoning), and fatigue following a really bad weekend (I work weekends).

I honestly didn't know that the BNC/PNC-55AC was based on this design.

Thanks for the info!
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Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.
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