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Discussion in 'The Watering Hole' started by bobkrech, May 26, 2016.
Would VMax be fast enough to use for an endburner of any size?
There were multiple reports here on TRF, well before the rule. Jim Jarvis' warning was the first one I remember. Even before that, I experienced it myself on an I800, so I did pay attention as soon as others wrote about it.
The J1799 was originally a J2135, then a J1999 which had a lot of catos in the desert heat so backed off some more to a J1799. Warp9 is definitely faster than VMax or SuperThunder. The advantage of VMax was CTI made it in small sizes like the E75 or F240. Aerotech had a lot of interesting motors back around the late 80s such as the D3, E6, F10, E110, G55, G300, 38mm IIRC G345, 54mm H340, etc
The J1799 is a 3 grain motor while the K2045 is a 4 grain motor. I've flown both. Warp 9 is .5 sec, SuperThunder is .7 sec, both in 54mm.
No, I just don’t like policy changes without notice that they are under consideration. Just like with the switches, it would have been very simple to announce to the membership “Hey folks we are getting a disturbing number of reports that X is happening. We are actively reviewing the situation and will likely take action soon”, Bonus points would be awarded if a partial list of possible outcomes was provided.
I’m a big fan of transparency in organizational leadership.
I totally agree with Al. At CATO, we flew a ton of VMax motors in small single deploy rockets. Seems like most people I flew with in the early days love the spank in a can and I had a decent stock of them as did most people I knew. Getting stuck with a stock of motors that can’t really be used for much other than simply dumb rockets kinda sucks especially when there wasn’t really an issue with the smaller motors (that I am aware of). I mostly flew VMax motors and never had an issue. I always felt that any issues was wit the larger 54’s and up, not the 24, 29 and 38’s. I carted with an H410 in an Onyx for heavens sake and it was spectacular. I’ll miss those days and I’m pretty sure Al will as well. After all, he was the one who taught me how to love the fast burns
Have you flown all of them?
I bet some armchair engineers think the N10000 and O3400 are rougher than the N5800.
Yes I have flown them all . I also have data that clearly shows the J1799 does not "kick" harder then a K2050 .
The N10,000 has more average thrust then a O3400 or the N5800 . So by your "armchair engineering standards" , yes the N10000 is "rougher" then the O3400 or N5800 . If you would like , thrustcurve.org is a wonderfull tool to actually see what motor "kicks harder".
But the N5800 burns 3x longer. That sustained force is what made it the rocket killer
(I agree with you about the Js/Ks though)
Transparency is crucial and I’ve tried to help that by being accessible and by answering questions, but directors, who are elected by the members, and committee chairs, who are approved by the directors, must sometimes make difficult decisions to protect the hobby, the association, and the membership as a whole. When a risk is identified, deferring those decisions exposes the association to additional liability. We can always revisit a decision. And we will make mistakes.
That is not what I was told, but I am not interested in getting into it publically.
I know all about thrustcurve.org, thanks. Care to explain why a K261 comes off the pad so much harder than a K250, when your data source and analysis disagree?
The K261 does not come off the pad as hard as a K250 , you are throwing stuff at a wall trying to see what sticks . The K261 has a slightly higher average thrust , but total impulse is far lower , and the peak thrust is lower . Next question ?
Guys, if you're just going to argue, please take it to PM's. Thanks.
I’ve heard (anecdotally, no insider information) only that CTI couldn’t replicate the problem on the test stand. I could believe that. Base drag may have been a factor. I really don’t know. Could it have been handled differently? Of course; everything can be in hindsight.
Steve, I give you credit for being as transparent as possible. As I noted, I would have been completely happy had the BOD simply alerted us there was a potential safety issue at hand and was under consideration. The board would have had the benefit of wide scale input from the community to, perhaps, make a better (or at least better informed) decision.
As far as I know, I can’t look somewhere and find supporting data for the VMAX decision and it has been years. What got my goat was a member of S&T telling me that I did not need to know why, the matter was not up for discussion, so just live with it.
I don’t know why a member of S&T would say that. There was nothing secret about the decision. We had multiple accounts, including reports here. We had to act.
Maybe less impulse motors could have been excluded. I don’t know. If CTI brought us the information saying the delay snuffing doesn’t happen in motors under some threshold, I fully believe we could resurrect the issue and make it more specific. I don’t think this is part of why CTI has discontinued VMax, but I’m not privy to those decisions.
This is really a moot point... just about every rocket that I've ever seen used with a VMax (or Warp 9) would run out of delay before it hit apogee anyway. I still have an H410 in my motor inventory... I'll put it up on my Mongoose 29mm someday. With and Eggtimer and an Eggfinder, of course...
Not moot at all. Short stubby draggy little rockets and Vmax motors are like peas and carrots. There is plenty of delay for them. I can't tell you how many F120 and G250's I have pumped through an Onyx. Match made in heaven. Heck, even the H410 delay had to be drilled.
No, I am not throwing stuff at a wall. The subtlety may be lost on someone looking to argue, but I carefully chose the original words to be subjective, specifically to avoid a pissing match. Epic fail there, i guess.
A few of us have a very good idea why the V-Max reloads are not being made any more. But the fact is CTI made that call and it's totally up to them.
I don't. Send me a PM with the info, won't disclose it publicly.
You got me there. I don't do short stubby rockets... although I'd love to get an 8" Gizmo.
For flyer's education purposes, would you explain your original point regarding the K261 and K250?
K250 has an incredible (nearly 200lb) spike right up front, but it is so short-lived that in practice it never seems to matter much, and behaves much like you would expect any 7 second white moonburner. think of snapping your leg real hard with a rubber band, big spike, but not going to move you off your chair an across the room.
The real point is that you cannot tell all about a flight from a simple 2D plot from the motor. weather matters, launch system matters, and of course the rocket matters
Regular gizmo and K2045 = one mile, leave the delay alone, perfect apogee deployment. (sigh)
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