Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > The Doctor is In! > Ask the Doctor
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 07-02-2012, 01:37 PM
Psank Psank is offline
Junior Rocketeer
 
Join Date: Apr 2012
Posts: 2
Default Booster question

I am building my first booster rocket with my daughter, and have a simple questions. How tight or loose should the booster section be to the main rocket? We are building a SEMROC Shrike and the booster stage seems pretty tight.

The engine hook on the main rocket needs to slide inside the engine tube of the booster, that makes a pretty tight fit. Is this okay or do I need to somehow loosen the connection?

any help would be great!!

thanks
Phil
Reply With Quote
  #2  
Old 07-02-2012, 01:43 PM
stefanj stefanj is offline
Master Modeler
 
Join Date: Mar 2005
Location: Hillsboro, OR
Posts: 2,847
Default

I think you've got a construction problem. The upper-stage motor hook should not enter the booster stage motor mount tube.

The "classic" Estes multi-stage motor mounting technique didn't use motor hooks at all, because the motors were taped together.

Later, the "pop and go" method was introduced. The motors were not taped together, and there was a small gap between the top of the booster motor and the nozzle of the sustainer. Sometimes vent holes are put in the booster to vent gas.

Without knowing exactly how you put the model together I'm not sure how to correct things.
__________________
NAR #27085 - Oregon Rocketry - SAM
Reply With Quote
  #3  
Old 07-02-2012, 06:03 PM
scsager's Avatar
scsager scsager is offline
Mid Power Wannabe
 
Join Date: Jul 2010
Location: Wisconsin
Posts: 59
Default

The instructions call for two hooks, one ea. for the booster and sustainer.

http://www.semroc.com/Documents/pdf/Shrike.pdf

Steps 7,8, 9, 13 and step 21 establish the correct dimentions. Could you have made a mistake?
__________________
- Scott, NAR 91621
Woosh #558
Reply With Quote
  #4  
Old 12-15-2012, 01:27 PM
Leo's Avatar
Leo Leo is offline
German Model Rocket Builder
 
Join Date: Sep 2005
Location: Germany
Posts: 1,313
Default

Quote:
Originally Posted by Psank
I am building my first booster rocket with my daughter, and have a simple questions. How tight or loose should the booster section be to the main rocket? We are building a SEMROC Shrike and the booster stage seems pretty tight.

The engine hook on the main rocket needs to slide inside the engine tube of the booster, that makes a pretty tight fit. Is this okay or do I need to somehow loosen the connection?

any help would be great!!

thanks
Phil


I've just finished the booster and the upper stage. The situation is exactly as you describe. Don't worry about the tight fit tho. The booster will separate.

Did you finish your Shrike and if so have you flown it yet?
__________________
Leo

My rocket fleet and more @ Leo's Leisure Site and on YouTube - My latest project: ALTDuino
Reply With Quote
  #5  
Old 12-15-2012, 02:24 PM
tbzep's Avatar
tbzep tbzep is offline
Dazed and Confused
 
Join Date: Mar 2005
Location: TN
Posts: 11,610
Default

Quote:
Originally Posted by Leo
I've just finished the booster and the upper stage. The situation is exactly as you describe. Don't worry about the tight fit tho. The booster will separate.

Did you finish your Shrike and if so have you flown it yet?


"Pretty tight" is ok. Anything more than "pretty tight" will result in the stages not separating and the sustainer firing through the booster....roasting the interstage area in the process.
__________________
I love sanding.
Reply With Quote
  #6  
Old 12-15-2012, 03:01 PM
mwtoelle's Avatar
mwtoelle mwtoelle is offline
Flying since 1977
 
Join Date: Oct 2010
Location: Middle TN
Posts: 452
Default

Quote:
Originally Posted by tbzep
"Pretty tight" is ok. Anything more than "pretty tight" will result in the stages not separating and the sustainer firing through the booster....roasting the interstage area in the process.

And if it is too loose, the pressure generated by the blow-through of the booster motor separates the booster without igniting the upper stage, usually resulting in the sustainer lawndarting.
__________________
'Til next time,

Mike Toelle

NAR 31692 L1

SAM 0373
Reply With Quote
  #7  
Old 12-15-2012, 03:22 PM
Leo's Avatar
Leo Leo is offline
German Model Rocket Builder
 
Join Date: Sep 2005
Location: Germany
Posts: 1,313
Default

Quote:
Originally Posted by mwtoelle
And if it is too loose, the pressure generated by the blow-through of the booster motor separates the booster without igniting the upper stage, usually resulting in the sustainer lawndarting.


Except when using the Shrike as dual deploy which I will be doing. It's a perfect rocket for the task
__________________
Leo

My rocket fleet and more @ Leo's Leisure Site and on YouTube - My latest project: ALTDuino
Reply With Quote
  #8  
Old 12-15-2012, 09:32 PM
jharding58's Avatar
jharding58 jharding58 is offline
Master Modeler
 
Join Date: Apr 2007
Location: Kennesaw, GA
Posts: 1,936
Default

You have built the Shrike per the instructions in which the booster coupler extends about 1/2 inch above thebooster BT, and the sustainer motor tube is flush with the bottom of the BT. This places the sustainer hook about 1/4 inch into the booster. The best recommendation I can offer is that the booster should be able to turn on the sustainer with a little twisting pressure. Not loose, and surely not tight enough to stick. If it is too tight, lightly sand around the coupler. If it becomes too loose, lightly dampen the coupler prior to a flight.

Nice model. Enjoy your flights.
__________________
Gravity is a harsh mistress
SAM 002
NAR 91005
"The complexity of living is eminently favored to the simplicity of not."
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 06:41 AM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe © 1998-2024