L3 – post-mortem analysis….

[Warren B. MusselmanModerator]

All my sympathies Sean… such a gorgeous project, such a nice Up part to the flight. All my best on your next try.

Warren

[Steve JensenParticipant]

Information like this is invaluable to me. It gives me insights to issues I am very foggy in understanding.

The pictures were amazing.

Sorry about your rocket. It was gorgeous.

[John A. WilkeParticipant]

Sean – how high was flight #1 vs. flight #2? did you go appreciably higher on the second boost?

The gremlins come out and play at mach 2+ and ~20K altitude… it took me a few swings at the plate to get efficient up there.

I’ve used this to over 40K MSL http://www.wimpyrockets.com/page16.html with clean recovery (and 62K MSL w/o clean recovery – but the charges worked)

[Warren B. MusselmanModerator]

With the experiences of folks like John Wilke and various sundry others I found on the web, the ONLY BP charges I do now are surgical tubing… Won’t even bother with anything else. My L3 deployed flawlessly.

W

[Douglas Krohn]

Sean,

The Raven data for your 1st flight showed 18K alt with the baro and 21K with the accel data.

After reading everyone’s ideas about the failure of the second flight I would think the idea that the fg coupler caused a binding issue is top of the list. The only problem I see with that is that you said the coupler seemed to slide into the airframe easily when you assembled it for the 2nd flight.

With the heat of the burn could have the all thread and harware have warped which caused the fg coupler to bind?

As you know my 3″ coupler has a similar design. Although my flight was successful I have to wonder how close I may have come to having the very same issue.

[John A. WilkeParticipant]

Guys, had the coupler been the only thing in the rocket, I think “binding” would be the prime suspect. The game-changer here is that Sean used the motor for the coupler, and the section of glass coupler was on top of that. I mis-read the setup earlier when I suggested the short coupler may have caused the binding.

I think with the motor as a coupler and the extension on top of that, there isn’t any real way that the coupler bound. I’ve flown that setup many, many times with success.

Unreleated note – Why would the accel and baro be so far apart? On a very corkscrewed flight you’d expect some variance – but Sean’s boosts were very straight. Even on a corkscrewy flight, you shouldn’t have a delta of several thousand feet…

[sserell]

Unfortunately we never pulled data off the other Raven for the first flight as the way it was mounted to the board required removal to access the data port, so we just figured we’d download it after the second flight – you can guess from the photo above that this proved to not be possible.

Also of interest is the Garmin DC-20 transmitted flight data from the second attempt to the handheld, allowing the data to be downloaded and get the altitude. What was interesting was data from the first flight was not on the handheld unit, or it was overwritten by the second flight.

For my L3 take 3 I’ve decided to rebuild the 98 goose, however I may change some of the design components, possibly doing a more traditional design using the ebay as the coupler and I am considering using a Zpard for the apogee separation. When you think about the physics of it seems like a much more reliable method of separation, however again it has its own separate issues as well. -Sean

[edwardModerator]

Sean,

Contact me about the Z-pard – I’ve got one made and the packing issues have vanished 🙂

Edward

[bryans]

care to post a picture of the Z-pard? Came up with very little on Google, other than edward himself at http://www.rocketryforumarchive.com/showthread.php?t=6715&page=3

BAsically a Z-pard is a small device that uses a metal piston to deploy the nosecone. You are using basically a 1/4″ tube and piston and use a tiny amount of BP. I saw it in ER and have been constructing one for my next rocket.

Edward

I’m having trouble visualizing…

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