Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > Work Bench > Scale & Sport Scale Rocketry
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #11  
Old 08-02-2010, 07:14 PM
rocketguy101's Avatar
rocketguy101 rocketguy101 is offline
frustrated aero
 
Join Date: Sep 2006
Location: Duncan, OK
Posts: 754
Default

Quote:
Originally Posted by blackshire
David, if I could ask your indulgence just one more time, how long is the Centuri MX-774's ST-8 body tube? The written-up documentation page that accompanies the plans on JimZ's web site gives the length (the author's guess) as 4.5 inches.

Many thanks in advance for your help!

I measure 4.5" on the nose. I am measuring from the edge of the boattail to the front edge of the tube. The boattail is 1.25" long.

It is a short tube---makes packing the recovery system challenging!
__________________
David Stribling
NAR 18402 SR
But it is rocket science!
Get yer Barrowmans here
Reply With Quote
  #12  
Old 08-02-2010, 08:16 PM
blackshire's Avatar
blackshire blackshire is offline
Master Modeler
 
Join Date: Jan 2009
Location: Fairbanks, Alaska
Posts: 5,875
Default

Quote:
Originally Posted by rocketguy101
I measure 4.5" on the nose. I am measuring from the edge of the boattail to the front edge of the tube. The boattail is 1.25" long.

It is a short tube---makes packing the recovery system challenging!
Thank you, David! That would be "crowded" for a 'chute. :-) Since Semroc lists that tube length as 5.5", I wonder if Centuri may have changed the length sometime during the MX-774 kit's time in production? I vaguely recall reading somewhere (maybe in one of Peter Alway's books or articles) that the full-scale MX-774 was built in two different lengths.
__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR
Reply With Quote
  #13  
Old 08-02-2010, 08:49 PM
rocketguy101's Avatar
rocketguy101 rocketguy101 is offline
frustrated aero
 
Join Date: Sep 2006
Location: Duncan, OK
Posts: 754
Default

Quote:
Originally Posted by blackshire
Thank you, David! That would be "crowded" for a 'chute. :-) Since Semroc lists that tube length as 5.5", I wonder if Centuri may have changed the length sometime during the MX-774 kit's time in production? I vaguely recall reading somewhere (maybe in one of Peter Alway's books or articles) that the full-scale MX-774 was built in two different lengths.

Yes, in ROTW, the third flight incorportated a 34" long instrument compartment, which at 1/33 scale, would be about 1" long.

The MX-774 has a rounded (ogive?) boattail that starts above the fins. Centuri changed this to a straight body with a conical (straight) boattail.

BTW the G. Harry Stine drawings available from NASM (link above somewhere) are excellent with interesting details (antennas, vents, etc).
__________________
David Stribling
NAR 18402 SR
But it is rocket science!
Get yer Barrowmans here
Reply With Quote
  #14  
Old 08-02-2010, 09:34 PM
blackshire's Avatar
blackshire blackshire is offline
Master Modeler
 
Join Date: Jan 2009
Location: Fairbanks, Alaska
Posts: 5,875
Default

Quote:
Originally Posted by rocketguy101
Yes, in ROTW, the third flight incorportated a 34" long instrument compartment, which at 1/33 scale, would be about 1" long.
Ah yes, that's what it was! (I didn't think they would have built two MX-774 main airframe "marks" in the eventual production batch [out of the 10 rockets planned] of just 3 vehicles.)
Quote:
Originally Posted by rocketguy101
The MX-774 has a rounded (ogive?) boattail that starts above the fins. Centuri changed this to a straight body with a conical (straight) boattail.
Good--I *wasn't* "seeing things" in the photos of the full-scale rockets--that rear curved taper *was* really there! :-)
Quote:
Originally Posted by rocketguy101
BTW the G. Harry Stine drawings available from NASM (link above somewhere) are excellent with interesting details (antennas, vents, etc).
As for myself, I'll stick with the Centuri kit (but I thank you for pointing that out for the more ambitious scale modellers among us). I had gotten away from scale model rockets for a number of years because I contracted "accuracy fever"--if a model wasn't within a hair of perfect (in terms of available scale documentation as well as actual construction) I couldn't build it, and as a result I built very few scale model rockets. :-) By enjoying the "just to Centuri (or Estes) standards" scale kits such as the MX-774, I can enjoy scale model rocketry again without risking another bout of "accuracy fever."
__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR
Reply With Quote
  #15  
Old 08-02-2010, 09:38 PM
blackshire's Avatar
blackshire blackshire is offline
Master Modeler
 
Join Date: Jan 2009
Location: Fairbanks, Alaska
Posts: 5,875
Default

By the way, here's the catalog "fleet group photo" showing the MX-774 in the 1972 Centuri Catalog: http://www.ninfinger.org/rockets/no...a/72cen024.html .
__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR
Reply With Quote
  #16  
Old 08-05-2010, 07:24 PM
dwmzmm's Avatar
dwmzmm dwmzmm is offline
Master Modeler
 
Join Date: Apr 2005
Location: Katy, TX
Posts: 2,303
Default

Great thread!! I have the Centuri kit too, and it does fly very high, even on a Quest A6-4 engine. I've been planning on building a larger scale MX-774 so as to incorporate a cluster of four engines like the real one. Thanks for all the links!
__________________
Dave, NAR # 21853 SR.
Section Advisor
Old Rocketeers # 724
Reply With Quote
  #17  
Old 08-05-2010, 08:16 PM
rocketguy101's Avatar
rocketguy101 rocketguy101 is offline
frustrated aero
 
Join Date: Sep 2006
Location: Duncan, OK
Posts: 754
Default

Quote:
Originally Posted by dwmzmm
Great thread!! I have the Centuri kit too, and it does fly very high, even on a Quest A6-4 engine. I've been planning on building a larger scale MX-774 so as to incorporate a cluster of four engines like the real one. Thanks for all the links!

Dave, what is your tube length? I am curious to see if Centuri did change it during the production run.
__________________
David Stribling
NAR 18402 SR
But it is rocket science!
Get yer Barrowmans here
Reply With Quote
  #18  
Old 08-05-2010, 08:30 PM
dwmzmm's Avatar
dwmzmm dwmzmm is offline
Master Modeler
 
Join Date: Apr 2005
Location: Katy, TX
Posts: 2,303
Default

Quote:
Originally Posted by rocketguy101
Dave, what is your tube length? I am curious to see if Centuri did change it during the production run.


David, I think it's 4.5" too. The particular kit I had has the plastic red nosecone instead of the balsa. I didn't like the plastic one, as the tip is rounded instead of sharply pointed. I've only flown it once (at NSL-2004) as I was surprised as to how high it flew on a Quest A6-4.
__________________
Dave, NAR # 21853 SR.
Section Advisor
Old Rocketeers # 724
Reply With Quote
  #19  
Old 08-06-2010, 02:07 AM
blackshire's Avatar
blackshire blackshire is offline
Master Modeler
 
Join Date: Jan 2009
Location: Fairbanks, Alaska
Posts: 5,875
Default

Quote:
Originally Posted by dwmzmm
David, I think it's 4.5" too. The particular kit I had has the plastic red nosecone instead of the balsa. I didn't like the plastic one, as the tip is rounded instead of sharply pointed. I've only flown it once (at NSL-2004) as I was surprised as to how high it flew on a Quest A6-4.
Dave, does your MX-774 have a blow-molded PNC-89 nose cone, or is it injection-molded? Centuri switched to a blow-molded version of the PNC-89 in the MX-774 kit during the company's later years (see: http://www.postwarv2.com/mx774/flyi...turi_mx774.html ). If this was the case with your MX-774, then the 4.5" long body tube remained constant from the early production runs of the kit to the later ones.
__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR

Last edited by blackshire : 08-06-2010 at 03:43 AM. Reason: This ol' hoss done forgot somethin'.
Reply With Quote
  #20  
Old 08-06-2010, 02:45 AM
blackshire's Avatar
blackshire blackshire is offline
Master Modeler
 
Join Date: Jan 2009
Location: Fairbanks, Alaska
Posts: 5,875
Default

Quote:
Originally Posted by dwmzmm
From Reply #16: Great thread!! I have the Centuri kit too, and it does fly very high, even on a Quest A6-4 engine. -SNIP-
and...
Quote:
Originally Posted by dwmzmm
From Reply #18: -SNIP- I've only flown it once (at NSL-2004) as I was surprised as to how high it flew on a Quest A6-4.
Dave, the MX-774 also flies well on 13 mm mini motors (using a friction-fitted motor adapter mount, of course). The "Recommended Engines" chart in the 1979 Centuri catalog (see: http://www.ninfinger.org/rockets/no...a/79cen062.html ) lists the 1/2A4-3M and A4-4M Centuri mini motors for the MX-774. The recommended maximum rocket lift-off weights (including motors) for these motors are 2 ounces and 2.5 ounces, respectively (see: http://www.ninfinger.org/rockets/no...a/79cen042.html ) The Estes near-equivalents of these motors are the 1/2A3-2T and A3-4T (both have a 2 ounce maximum lift-off weight, see: http://www.ninfinger.org/rockets/ca...74/74est54.html ). The A10-3T should also work well in the MX-774.
__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR

Last edited by blackshire : 08-06-2010 at 02:47 AM. Reason: This ol' hoss done forgot somethin'.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



All times are GMT -5. The time now is 09:52 AM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe 1998-2019