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  #11  
Old 04-04-2011, 08:56 PM
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Until now, I'd never even heard of the Krushnik Effect.

Are you making this up?
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  #12  
Old 04-04-2011, 10:26 PM
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Quote:
Originally Posted by rocketguy101
I have a build thread on my Centuri Saturn V here we discussed adhesives there. This model is similar to the current Estes Saturn V.

I noticed this thread on RP, the poster mentions some problems with the third stage reduction wrap not fitting the paper shroud correctly. I have not started building my 2157 yet, but I want to check that out.

ps: I tried flying w/ an F motor, and did get a little scorching on the bottom.


Great reading rocketguy, and beautiful Centuri Sat V!
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  #13  
Old 04-04-2011, 10:28 PM
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Quote:
Originally Posted by jeffyjeep
Until now, I'd never even heard of the Krushnik Effect.

Are you making this up?

chk pg 37 of the Nov 69 Model Rocketry (pg 39 of the pdf)
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  #14  
Old 04-04-2011, 10:30 PM
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Quote:
Originally Posted by cas2047
Great reading rocketguy, and beautiful Centuri Sat V!

Thanks! Keep us posted on your build, I am really curious as to how different the new Estes model is to the Centuri version.
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  #15  
Old 04-04-2011, 10:34 PM
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Quote:
Originally Posted by Randy
Go ahead and pull the mount back to the bottom and add a little weight to the capsule, plenty of room in there. Just keep the cg at 17.5" from the bottom of the bt and you're good to go.

Randy
www.vernarockets.com


Thanks Randy. I think if I recess it 2 1/4" it should eliminate any serious interior burning.

I built the Sat V kit 2001 a few years back and I set that one up with a trippe 24mm mount, also recessed to 2 1/4" and that one has flown with no interior burning so I think that's probably a good compromise placement. I've never launched that 2001 version with an RMS motor though...
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  #16  
Old 04-04-2011, 10:38 PM
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Quote:
Originally Posted by rocketguy101
Thanks! Keep us posted on your build, I am really curious as to how different the new Estes model is to the Centuri version.


Will do rocketguy!. I'm hoping to make some good progress on it this week, as long as I can pickup the adhesives I need.
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  #17  
Old 04-04-2011, 10:54 PM
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Quote:
Originally Posted by rocketguy101
I noticed this thread on RP, the poster mentions some problems with the third stage reduction wrap not fitting the paper shroud correctly. I have not started building my 2157 yet, but I want to check that out.


My son built his first run 2157 kit and had issues with the third stage wrap. He printed off a new paper shroud with the correct dimensions to match the wrap. The original Centuri kit had much thinner plastic wraps and the body tubes are just a hair different from Estes. That combination seems to have made a considerable difference.
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  #18  
Old 04-04-2011, 11:00 PM
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Quote:
Originally Posted by Earl
I seem to recall a very general rule of thumb on preventing the Krushnic effect by recessing the motor (i.e., specifically the exit plane of the nozzle) to NO MORE THAN one body diameter. In the case of the Saturn V, that'd be just about 4 inches, so a 3 and 3/8", it would seem by that general rule you'd be ok.

Anyone else confirm this general rule? You don't hear folk talk much about the ol' Krushnic effect anymore.


The Krushnic Effect is definitely real. I had an Estes Hercules that kicked the booster motor without kicking off the booster airframe. The A8-5 burnt out the booster motor tube, but the sustainer did not gain much altitude after staging. For this flight, the sustainer motor acted like a delay train, instead of taking the upper stage to the significantly higher altitude that it would have reached if everything had worked normally. I suspect that if I had used a B or C motor instead of an A8-5, the booster airframe (BT-50) might have been burnt away as well.
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Last edited by mwtoelle : 04-04-2011 at 11:05 PM. Reason: Added something
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  #19  
Old 04-05-2011, 07:53 AM
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[QUOTE=Earl]I seem to recall a very general rule of thumb on preventing the Krushnic effect by recessing the motor (i.e., specifically the exit plane of the nozzle) to NO MORE THAN one body diameter. In the case of the Saturn V, that'd be just about 4 inches, so a 3 and 3/8", it would seem by that general rule you'd be ok.

Sounds right.

>Anyone else confirm this general rule? You don't hear folk talk much about the ol' Krushnic effect anymore.

I think it's not talked about too much because 99% of the rockets being flown all have the engines at or below the bottom of the bt. I have only seen it happen once to another flyer who set his rocket about a half inch off the blast plate. It didn't go anywhere and burned about 75% of the rocket before it was extinguished.

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  #20  
Old 04-05-2011, 09:46 AM
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Quote:
Originally Posted by jeffyjeep
Until now, I'd never even heard of the Krushnik Effect.

Are you making this up?



The first time I heard that term used, I thought they were talking about the Russians pranging a satellite launcher...


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