8 seconds from ignition to liftoff, then crooked flight

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billdz

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Any thoughts on what may have happened with this flight:
[video=youtube_share;WrM8-G6wmLM]https://youtu.be/WrM8-G6wmLM[/video]
There were 8 seconds from ignition to liftoff. After liftoff, the rocket cocked westward, against the wind. Could the 2 events be related? This rocket has flown arrow straight on prior flights.
Thanks,
Bill

PS - The rocket was recovered safely, landed in an adjoining golf course. The pro said it just missed landing on the roof of the clubhouse.
 
Any thoughts on what may have happened with this flight:
[video=youtube_share;WrM8-G6wmLM]https://youtu.be/WrM8-G6wmLM[/video]
There were 8 seconds from ignition to liftoff. After liftoff, the rocket cocked westward, against the wind. Could the 2 events be related? This rocket has flown arrow straight on prior flights.
Thanks,
Bill

PS - The rocket was recovered safely, landed in an adjoining golf course. The pro said it just missed landing on the roof of the clubhouse.

Weathercocking is always exaggerated by tipping a rocket into the wind. We generally advise people not to tip a rocket into the wind for that reason.
Slow ignition can happen for various reasons, including poor connections to the igniter, low voltage on the battery, insufficient pyrogen on the igniter, placing the igniter too low in the rocket (chuffing), etc. The motor looked like it burned okay once it got started. I would just make sure the clips are clean and battery charged.
 
Slow smokies and overstable rockets in wind will do kick over like clockwork. I love smokies but only fly them in clam conditions.
 
The two previous posters have this right.

A couple questions- how fast was the wind?
How long, heavy, and diameter of the rocket?
 
Length 159cm, max diameter 5.8cm, weight with motor 2185g. Previously flown on G138 and H135. Wind was around 10mph, no stronger than during prior flights. On the video, it seems to start off nice and straight, then makes a distinct turn to the west at the 0:13 second mark.

On the delay after ignition, I'm guessing some issue with the igniter or its placement, as several other rockets launched from that same pad without issue.
 
I would suggest it is over stable. I would also tell you that the wind is almost always faster at altitude. If the wind was 10 mph on the deck, at a 1000-2000 feet it could be considerably higher.
 
The H112J is not a particularly thrusty motor to begin with. It's also heavy being it is a 3 grain 38mm motor.

However it is awesome in the right rocket. I once flew one in a 38mm saucer. It was one of the BIGGEST crowd pleasers that day.:wink:

Here it is. This was just before the motor fully pressurized.

Saucer - H112J.jpg
 
I had the same slow starts. Bugged me for 24 hours, then it dawned on me that I had only a 9v battery in the controller, and forgot to put in my 12v. I ordered a 14.8v lipo today that will become the standard.
 
Man, he's speaking metric but lives in Florida....wish i knew what he was saying :> I don't speak metric.....
the delay on ignition could also be if the ignitor isn't all the way up, or 'just one of those smokey things.....
it puts out less peak newtons then the G138 you flew it on..

Still, a nice flight
 
After liftoff, the rocket cocked westward, against the wind.

PS - The rocket was recovered safely, landed in an adjoining golf course. The pro said it just missed landing on the roof of the clubhouse.

This is not hard to diagnose. It appears to be simple weathercocking into the wind with an underpowered motor. Blackjacks are also known to be a more difficult propellant to ignite.

A quick check on Thrustcurve Motor Guide shows a very low lift off velocity of just 12 m/s from a 2m rail. This is well below the recommended best practice of 15 m/s. Add in the wind, or a gust of wind, and the resulting trajectory is no surprise. This was a poorly-conceived flight that did not safely stay in the launch area.

Hmm. An experienced flyer such as an L3 should know better.
 
Thanks all, I agree, needed a motor with more thrust. Simmed OK on Open Rocket with wind at 10mph, so the wind must have been stronger higher up. As for the slow ignition, it must have been the igniter.
 
Slow smokies and overstable rockets in wind will do kick over like clockwork. I love smokies but only fly them in clam conditions.

The conditions I prefer are chowder... or sometimes steamed (with butter)... You know any chance I can, I shell use a pun.
 
This is not hard to diagnose. It appears to be simple weathercocking into the wind with an underpowered motor. Blackjacks are also known to be a more difficult propellant to ignite.

A quick check on Thrustcurve Motor Guide shows a very low lift off velocity of just 12 m/s from a 2m rail. This is well below the recommended best practice of 15 m/s. Add in the wind, or a gust of wind, and the resulting trajectory is no surprise. This was a poorly-conceived flight that did not safely stay in the launch area.

Hmm. An experienced flyer such as an L3 should know better.

:rofl:
Thank you...
That needed said...
I keep thinking about a tree in a swamp for some reason...
Something about alligators even
...
Weathercocking is something that should have be learned during the journey to L1, not after L3. Pretty sure there were even questions about it on the L2 test, or at least in the study material. The Pro would've been thrilled had this been a 50lb beast, and the flyer walks up to recover while scratching his head not understanding what happened.
My apologies if I seem condescending or cynical. I'm but a lowly L2.
I'll dismiss myself and say no more.
 
Thanks all, I agree, needed a motor with more thrust. Simmed OK on Open Rocket with wind at 10mph, so the wind must have been stronger higher up. As for the slow ignition, it must have been the igniter.

Care to post your sim file?
 
The conditions I prefer are chowder... or sometimes steamed (with butter)... You know any chance I can, I shell use a pun.

I see what you did. Funny thing is I was more correct than I knew. You see, I haven't flown a smokie since I left New England so there!
 
What was your static stability margin? I've always exceeded the min RSO rail exit velocity by 55 percent on L-1 university scratch supersonic multistage competition rockets. We were using short arse 4ft rails too. The one with double the rail exit velocity didn't tilt. The one with lower rail exit velocity tilted 6 degrees at 15 mph crosswinds and we exceeded the mins. The masses and lengths were very similar. Booster stability was slight over 2 by a tenth or two, first try never done this before. Just an observations of flight behaviors similar weathervane. And these designs I did were less stable than most rocketry hpr store bought kits. Granted I'm an L0... I think the kits mostly like a bunch of overstability for a wide range of motors?!?!? Literally a Blackhawk 29 kit had 2.4 stability on an H118 out of the box.
 
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