A post from Hornet Driver on The Rocketry Forum:
". . . I gotta tell ya, I've never had a multistage rocket--no matter what type it is--track straight up . They always kick over at least a little when staging and the more you stage the more the problem. I'm personally convinced that it's caused by the sudden KICK when the upper stage lights off. I've gotten away from staging for the most part since my stuff always ends up in the next county over." --- H
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My response:
I've had the same results with two-stagers.
Boost is fine but when the upper engine kicks in it'll veer off at an angle. I don't think it had anything to do with the wind.
That one inch (or less) of a coupler to guide the upper stage doesn't seem to help much.
I avoid flying staged models. I do like clusters, though.
Hans "Chris" Michielssen
Old/New NAR # 19086 SR
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Response from John Boren of Estes:
We've flown well over a thousand two stage models here at Estes over the past few years and I've found by having the booster fit super loose into the upper stage is the key to the upper stage not veering off course at stage separation. In fact the booster on our E2X lines of models will fall off if let go: They are that loose.
John Boren
Thanks John! So that was my problem all along?
Up until now I've never read that a booster coupler should be "super loose".
I'm putting together a Long Tom right now. Right out of the bag, the red coupler was very tight. I've sanded it for a better slip fit, I guess I'll have to take it down even more! In the past I've tried for a slip fit on a staging coupler. Not too tight, not too loose.
This is probably why I fitted couplers this way -
Looking back at the 1970 Estes Technical Manual: CLICK HERE
"Rockets using large diameter tubes (BT-50 and BT-60) require somewhat different methods but the same principles of tight coupling and straight line separation must be followed. The recommended coupling method for large diameter tubes is illustrated in figure 4."
That same copy is used in the original Estes TR-2 on Multi-Staging. To see the Technical Reports: CLICK HERE
I'm putting together a Long Tom right now. Right out of the bag, the red coupler was very tight. I've sanded it for a better slip fit, I guess I'll have to take it down even more! In the past I've tried for a slip fit on a staging coupler. Not too tight, not too loose.
Looking back at the 1970 Estes Technical Manual: CLICK HERE
"Rockets using large diameter tubes (BT-50 and BT-60) require somewhat different methods but the same principles of tight coupling and straight line separation must be followed. The recommended coupling method for large diameter tubes is illustrated in figure 4."
That same copy is used in the original Estes TR-2 on Multi-Staging. To see the Technical Reports: CLICK HERE
Thanks for the post Chris. I have not had any real trouble staging yet, but I will try this on my just completed Super Chief II and see how it goes.
ReplyDeleteI'm going to have to try that. I've had mixed luck with two-stagers, but I find that after that, the coupler gets much tighter, due to soot, and I have to sand inside the aft end of the booster airframe. But they're pretty tight to begin with.
ReplyDeleteThat's interesting. I'll implement that on my Super Nova clone build, and if it works will retrofit all my staged models. Makes sense though: If the coupler doesn't bind on one area at separation then it should go out straight.
ReplyDeleteBTW I have a question about recovery protection methods, should I e-mail you? Not sure what should/should not be posted in comments anymore. Cheers,
BAR Geezer
Hi BAR,
DeleteDon't worry about making comments, it's the harsh criticism that bothers me! Feel free to email me at: oddlrockets@bellsouth.net