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  #101  
Old 04-18-2018, 03:06 PM
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blackshire blackshire is offline
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Quote:
Originally Posted by BEC
Ah - D21T (Blue Thunder). Yes, they can make a small model just disappear in a whoosh. The D10 is White Lightning and I've had some frustration with getting them lit....but they are "expressive" and bright to watch when they go.

I'm hoping that the ejection charges in the Q-Jets are a little less toasty than those in the D10/D21 motors. They can really cook the inside of a model. I do intend to find out as soon as I can.
I never got a chance to compare ejection charges--looking up, I saw a very narrow, distant line of tracking smoke from that D21T, and the X-Flyer went so high I never saw its 'chute (or even heard the ejection charge go off--the model was just gone). I've read that composite motors' ejection charges can char the insides of models, and can even--via remaining "spinters"--keep burning even as the rocket descends under its parachute; hopefully the Quest motors won't have these undesirable characteristics.
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  #102  
Old 04-18-2018, 04:05 PM
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Shreadvector Shreadvector is offline
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Nope.

The ejection charge blows all at once and is finished. It can be much stronger than what you are used to.

The continued burning/roasting is the "Hibachi Effect" and is from the delay afterburn. It is like a road flare inside your rocket.

Google it.

https://www.google.com/search?q=hib...lient=firefox-b

https://apogeerockets.com/education...ewsletter28.pdf


https://www.youtube.com/watch?v=b-8gsP2xI2M
Play it slow and stop it several times near the end.

Quote:
Originally Posted by blackshire
I never got a chance to compare ejection charges--looking up, I saw a very narrow, distant line of tracking smoke from that D21T, and the X-Flyer went so high I never saw its 'chute (or even heard the ejection charge go off--the model was just gone). I've read that composite motors' ejection charges can char the insides of models, and can even--via remaining "spinters"--keep burning even as the rocket descends under its parachute; hopefully the Quest motors won't have these undesirable characteristics.
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  #103  
Old 04-18-2018, 04:16 PM
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BEC BEC is offline
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It's that "hibachi effect" to which I was referring. It's cooked the insides of several of my LPR models that I put D10s or D21s into.
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  #104  
Old 04-18-2018, 04:26 PM
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blackshire blackshire is offline
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Quote:
Originally Posted by Shreadvector
Nope.

The ejection charge blows all at once and is finished. It can be much stronger than what you are used to.

The continued burning/roasting is the "Hibachi Effect" and is from the delay afterburn. It is like a road flare inside your rocket.

Google it.

https://www.google.com/search?q=hib...lient=firefox-b

https://apogeerockets.com/education...ewsletter28.pdf


https://www.youtube.com/watch?v=b-8gsP2xI2M
Play it slow and stop it several times near the end.
*Shrugs* The distinction (except possibly for motor manufacturers, concerning reducing or eliminating the problem) is...indistinct; the effect is what matters to the hobbyist. Hopefully Quest has managed to eliminate it.
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http://www.lulu.com/product/cd/what...of-2%29/6126511
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  #105  
Old 04-18-2018, 05:55 PM
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Jerry Irvine Jerry Irvine is offline
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The hibachi effect is caused by drilling fixed length delays from the ejection side rather than the motor side.

Just Tech Jerry
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  #106  
Old 04-18-2018, 06:23 PM
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Quote:
Originally Posted by Jerry Irvine
The hibachi effect is caused by drilling fixed length delays from the ejection side rather than the motor side.

Yep. We always drilled ours and inserted the hole facing the propellant grains our EX motors.
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  #107  
Old 04-18-2018, 07:10 PM
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Well...if it's from drilling delays then what is going on with D10s and D21s? Whatever you choose to call the effect, they will burn a BT-20-based model through in one or two flights and bubble the paint on a BT-50-based model after one or two flights.

In any event, one hopes that the Q-Jets aren't quite so prone to burn the insides of the models they are used in as the Aerotech D10/D21 do.
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  #108  
Old 04-18-2018, 09:34 PM
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ghrocketman ghrocketman is offline
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Why would anyone use a D10 or D21 in anything BT-20 or 50 based rocket unless it is a fire-and-forget flight ? Not likely to get it back unless the field is huge.
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  #109  
Old 04-18-2018, 11:22 PM
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I haven't actually flown anything BT-20-based on a D10, but I have flown something (Estes Astrobeam) that had a Bt-20 stuffer tube. The second use of the D10 burned it through. It's too bad because the D10 was what that heavy thing really needed. O at least a C5-3. After that I built an original BT-60-based night flyer with a 24mm motor mount that is better lit and lighter than the Astrobeam.

I've also flown a Nova Payloader on a D10 several times. It goes to about 1700 feet on one (while carrying an AltimeterOne) and it's really quite a satisfying flight on a large enough field (and with a reefed 'chute). But the paint bubbled just above the motor mount after the second such flight and I didn't do it more than a couple more times. That particular model was retired after its 75th flight due in large part ot the body getting really soft there just above the motor mount. It would have retired sooner if there had been more D10 flights. I'd have to go back through the log books but I think there were three or maybe four over its active lifetime.

I get the opportunity to fly at a field big enough for such stuff several times a year.
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Last edited by BEC : 04-18-2018 at 11:51 PM.
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  #110  
Old 04-18-2018, 11:45 PM
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blackshire blackshire is offline
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If (hopefully not jinxing us here! :-) ) the Quest motors do still have the "historically hot" ejection charges, a possible fix could be to "paint" those prone-to-softening portions of the body tube (and/or stuffer tube) with something like a thin, wicking CA, epoxy, or polyurethane glue, or with polyester resin (it stinks until it cures, but it's as hard as stone once it does).
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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.
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