vmax PSA

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watermelonman

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I know that W9 is famous for it, but vmax can definitely snuff out delay grains too. This past weekend we launched 11x K2045s in a drag race and 3 of them had no ejection. That is a fairly high ratio. Thankfully one had electronics for apogee but the other two came straight down.

Be safe and fly electronics!
 
I've seen (and had personal experience) with 3 VMax/no ejection events. I won't fly anything substantial anymore on a VMax without electronics. That said, a Blue Ninja on an E75 is really fun (but an F240 is a little too much).

David
 
Need more stats I think it is mostly 54s Ive flown 15+ 24-38mm no problems so far
 
Need more stats I think it is mostly 54s Ive flown 15+ 24-38mm no problems so far

Happened to me with an I800, which is kinda ironic, because I flew this motor only because I couldn't get a RDK-15 for the J350 I had originally planned. In the end, the altimeter recovered the rocket fine but I prefer motor backup for this rocket. This particular motor was already a couple years old, when I got it from a fellow flyer - so this might have had an influence.

On the other hand, a buddy of mine is quite fond of the H410 in his Jart, and the rocket has yet to suffer a failure.

Personally, I don't plan to fly a Vmax without a backup anytime soon, because this is not the first time that I hear about this issue.

Reinhard
 
I knew of 1; didn't hear that another came in ballistic. My RRC3 handled it great. 1304 fps in 1.7 seconds.

There were two black ones that got confused for each other, eventually we discovered that one of them was a lawn dart. Mine snuffed out the charge, but I had no idea until I was pulling the spent nozzle and closure to donate to Tony and he noticed the charge intact!
 
I know that W9 is famous for it, but vmax can definitely snuff out delay grains too. This past weekend we launched 11x K2045s in a drag race and 3 of them had no ejection. That is a fairly high ratio. Thankfully one had electronics for apogee but the other two came straight down.

Be safe and fly electronics!

I cannot believe that an RSO actually allowed a drag race with 11 VMAX motors.

My experience is that about 25 to 30% of the charges fail. I've seen it many times. I lost two rockets to this in the past, so I no longer fly them motor deploy. At launches I run, we first warn the flier, and if he wants to fly anyway, it's a heads-up launch with the rocket pointed away from the crowd. We begin to announce a ballistic recovery as soon as the smoke trail fails to appear.

I have previously brought up this issue with the Tripoli Board, with various board members over the years, with TMT, with TAP, with NAR and with CTI. I'm typically told that the problem is that since CAR certified the motors, it is up to them to take action - and they won't - and then Tripoli/NAR say they're powerless. Sad. And while I have many wonderful things to say about CTI, their proactive response to motor issues is not on the list.

I hope that the "word" on these motors is getting out. Please keep an eye out for new fliers that are not aware.

Jim
 
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Size issue? I've burned about a dozen F120Vmaxs in my DarkStar mini in the last year, never a failure.
 
I cannot believe that an RSO actually allowed a drag race with 11 VMAX motors.

If the safety guidelines are followed, including proper setbacks, there's nothing wrong with it. Of course, each RSO or club can apply more stringent rules.
All rockets were properly inspected prior to the race to ensure they would hold up to VMAX flight stresses.
 
If the safety guidelines are followed, including proper setbacks, there's nothing wrong with it. Of course, each RSO or club can apply more stringent rules.
All rockets were properly inspected prior to the race to ensure they would hold up to VMAX flight stresses.

So let's say there is a drag race with 11 rockets with electronic recovery, and just for fun, let's turn off the electronics on 3 of them. Is that OK?

Jim
 
If the safety guidelines are followed, including proper setbacks, there's nothing wrong with it. Of course, each RSO or club can apply more stringent rules.
All rockets were properly inspected prior to the race to ensure they would hold up to VMAX flight stresses.

Out of curiosity, how far where they from the spectators?
 
So let's say there is a drag race with 11 rockets with electronic recovery, and just for fun, let's turn off the electronics on 3 of them. Is that OK?

It is not OK to _knowingly_ conduct a drag race with 3 lawn darts, but this was not the case in the above mentioned launch. This is a bit similar to the infamous "as seen on tv" J1999 drag race. I don't think the RSO was aware of what would happen in this case either.

Reinhard
 
It would really be helpful if the fliers of three rockets would file MESS reports at motorcato.org.
So far, were 0 for 3.

John
 
I've personally flown lots of VMax motors. F through K. Never had the problem described here. Never seen the problem described here either. Strange that a half dozen people describe it as a regular occurrence...
That being said, 11 K2045s sounds awesome. I want to see video.
And what in the heck were they flying on that motor without electronic deployment anyway?
 
I've personally flown lots of VMax motors. F through K. Never had the problem described here. Never seen the problem described here either. Strange that a half dozen people describe it as a regular occurrence...
That being said, 11 K2045s sounds awesome. I want to see video.
And what in the heck were they flying on that motor without electronic deployment anyway?

It was the annual 1/4 scale Nike Smoke drag race. Here is a video of this year's race (not my video):
[video=youtube;eusbnYmUv-k]https://www.youtube.com/watch?v=eusbnYmUv-k[/video]
 
There were two black ones that got confused for each other, eventually we discovered that one of them was a lawn dart. Mine snuffed out the charge, but I had no idea until I was pulling the spent nozzle and closure to donate to Tony and he noticed the charge intact!

For it to "snuffed out" it would have to lit in the first place. I see no signs of any burning of the delay grain.

Tony

4.jpg

7.jpg
 
An 11 rocket drag race on VMax motors would be cool to see. Is there a video of the drag race?
 
I agree, the "V-max no ejection" is definitely a recurring issue. To all who have never experienced it, that's what this thread is all about. Let's keep it on track and get the word out to help others who may not be aware of the potential failure. We should try to keep this as it was intended, a PSA. Let's try not to have a discussion about how far the crowd was, or anything unrelated to the OP's original topic.
 
So, not 2,000 feet? ;)

its a a good warning about the charges. But it's been covered and someone mentioned safe distances. Was just curious if they followed their own advice.
 
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Love CTI, and love Vmax! But personally I have heard this reported before and if someone as experienced and level headed as Jim Jarvis "says proceed with caution" then I think it would be foolhardy to just dismiss his advice because you have not witnessed it. I plan on flying a Vmax this weekend at NYPOWER, but it will be with fully redundant electronics and the engine ejection BP removed.
 
For it to "snuffed out" it would have to lit in the first place. I see no signs of any burning of the delay grain.

Hah, true. I must have looked too fast or mistook the chunks on the O ring. Either way, no pop!
 
Tripoli Rocketry Association Safe Launch Practices – May 2016
II. Commercial Launches
F. When three or more rockets (at least one high power) are launched simultaneously, the minimum distance for all involved rockets shall be the lesser of:
1. Twice the complex distance for the total installed impulse. (refer to V. Distance Tables)
2. 2000 ft (610 M)
3. 1.5 times the highest altitude expected to be achieved by any of the rockets.
G. When more than one high power rocket is being launched simultaneously, a minimum of 10 ft (3M) shall exist between each rocket involved.

Common Name: K2045
Total impulse: 1407.6Ns
x 11
=15483.6ns
10,240.01 to 20,480 = N
Minimum Safe Distance Commercial Launch (Complex) = 1,500ft x 2 = 3,000ft

So in this case F.2 applies (2,000ft)
 
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For it to "snuffed out" it would have to lit in the first place. I see no signs of any burning of the delay grain.

Tony

It looks like the unburned delay wasn't drilled/adjusted. I'm sure it was left that way intentionally, but it makes me curious. I've launched many 38mm VMAX motors with no issues. I always adjust the delay, either to the minimum delay or the next shortest.

I wonder if the additional exposed surface area (or rough drilled vs. smooth un-drilled) helps it ignite and burn.

If that is the case, Maybe it's possible you just need a small nick in the grain to get it to light more reliably.
 
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