L3 4 Inch Black Brandt Scratch Build *Success*

flynfrog said:

Rocketry Warehouse





Fins are intermediate modulus 3k PW with a prototype nanocomposite resin system we were working on for composite tooling It has a low very low CTE and and is very hard. I think 12 plies but its been a year since a laid them up. I will need 3 layers of t2t of 3kPW a side to get out of flutter territory

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Did you have someone who could run a flutter sim for you? I've often wondered because of the limited parameters that are in FinSim as to whether or not it's of any use if one just guesses as to the strength of their building materials.
If you've already decided on t2t for the given material, you seemed to have all your ducks in a row. Kurt

ksaves2 said:

Ditch the D-bag and be a Burrito Boy for the main chute. Get the L3 and then go with the D-bags.....................Unless of course you've flown with a lot of D-bags and already got the deployments down pat.

I've had a chute hang in a D-bag so I'm 1 for 2. The failure was due to a "downsized" pilot chute on the bag and my "success" was sort of a Hail Mary. I used to pooh-pooh the B2 Rocketry technique of putting the nosecone on the D-bag with its own smaller chute and using the mass of the nosecone to yank the D-bag off the chute. Nosecone/D-bag comes down on its own chute and the heavier sustainer comes down on its own larger chute. I'm thinking theirs is a better idea now.

If one uses too large a drogue and too small of a pilot chute on the D-bag (for a conventional DD) the rocket might not be "falling" fast enough for a "too small" pilot chute on the D-bag to pull the bag off the main.
That was my failure. The rocket streamered in nicely with the main still stuffed in the bag and landed in soft dirt but no damage. It was a LOC cardboard tubed rocket too. No reinforcement so that was a lucky break.

Go simple if that's what your TAPs recommend. Kurt

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D-Bags are the most reliable way to unfurl your chute. I was a loadmaster in the USAF and spent lots of time in the rigging shop. If your D-bag setup doesn't work then it's rigged wrong. With that being said. In rocketry space is always an issue, D-bagging is not always possible. So when there is no bag I tend just keep in mind the logical order of procession and of course ground testing.

BayouRat said:

D-Bags are the most reliable way to unfurl your chute. I was a loadmaster in the USAF and spent lots of time in the rigging shop. If your D-bag setup doesn't work then it's rigged wrong. With that being said. In rocketry space is always an issue, D-bagging is not always possible. So when there is no bag I tend just keep in mind the logical order of procession and of course ground testing.

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Welllllll, I trial packed it and it took just a little shake for it to fall out. When put in a three inch rocket it packed tightly but an adequate charge was used. A video camera caught the chute stuck in the bag with the 36" pilot out. The chute lines were extended but the chute stayed in the bag. When I used a 48" pilot, it
worked. So yes you are right it was a wrong situation. It was a standard DD with the upper bay and the only difference was a D-bag attached to the main chute. The free-fall dynamics didn't come into place for that flight. I've seen chutes appear to streamer like there was a reefing ring in place except there wasn't. Rocket gets lower and the chute opens fully. Can't explain what happened there either.

I packed the chute in the D-bag the night before so it wasn't sitting too long.

Sooooooooo, Like I said, if one has had plenty experience with D-bags go for it on a certification attempt. If not, a cert attempt is not the time to be doing it for the first time. (Except perhaps with the 2 part noscone/bag/chute and
sustainer/large main. Would have to be certain one recovers both parts though. Kurt

I am behind on updating the forum I am planning on no bag I've used the burrito method in every one o f my rockets and will be sticking with that.

ksaves2 said:

Did you have someone who could run a flutter sim for you? I've often wondered because of the limited parameters that are in FinSim as to whether or not it's of any use if one just guesses as to the strength of their building materials.
If you've already decided on t2t for the given material, you seemed to have all your ducks in a row. Kurt

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I have been using fin sim. The T300 listed should be conservative for my laminate. Add some plies on top to make sure.

flynfrog said:

I have been using fin sim. The T300 listed should be conservative for my laminate. Add some plies on top to make sure.

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Welllll....... Seems you have your bases covered then. Whit (BayouRat) is much more experienced than I and since he mentioned adding the piles and you planned on doing it anyways, sounds like you're on the path to pull it off.
Kurt

The D-bag situation is definitely something you want to avoid on a cert flight if you haven't done it before. I was very close to missing my L3 cert because I borrowed my TAPS d-bag and it didn't work quite a well as expected. My next flight was a complete change. The pilot was attached to the nose cone and pulled the d-bag off the main. The pilot was sized to drop the nose cone at 10 - 12 ft/sec. The main dropped everything else at about 17 ft/sec. I use 75 ft of 150 lb Dacron line that was z-folded and taped from the inside of the d-bag to the top of the main. It worked perfectly. The pilot pulled the d-bag off the main, the main opened and the Dacron line kept the nose cone/d-bag and the rest of the rocket together.

Got My T2T done.





Qa approved

[YOUTUBE]6DrX_WySdEA[/YOUTUBE]

[YOUTUBE]omd3H18g1Kw[/YOUTUBE]

Deployment test.

Av Bay

One Day I swear I'll build a rocket with enough room that the av bay isn't a pain in the ass today is not that day.

Well the rocket launched today but not a cert flight.

Went up on an L875 Dark Matter. I wired the charges backwards so it dumped the main apogee Doh.

I did have some weird stuff going on with my Ravens ill post when I get a sec.

[youtube]3ENPxXVlDoM[/youtube]

It was still a nice flight.

Joe

Yeah,,
That does look like a nice flight Frog...
It sure was a seriously cool motor...

Teddy

Here is the raven data file. The altitude based on acceleration makes no sense to me. I have used both of these ravens in separate rockets and they worked fine. It was rather lucky I fired the main at apogee because neither altimeter tried to fire the Main charges. Any thoughts?

View attachment black brandt atl1 L875.FIPa View attachment black brandt atl2 L875.FIPa

Jmhepworth said:

It was still a nice flight.

Joe

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onebadhawk said:

Yeah,,
That does look like a nice flight Frog...
It sure was a seriously cool motor...

Teddy

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Thanks guys. If anything I feel much better about a L3 attempt now. With the M motor it only sims 2k feet higher and slightly faster. Just need to sort out this altimeter issue and make some labels on my av bay. I may change to a D bag for my L3 but I want to have a look sewn into my chute first.

flynfrog said:

Here is the raven data file. The altitude based on acceleration makes no sense to me. I have used both of these ravens in separate rockets and they worked fine. It was rather lucky I fired the main at apogee because neither altimeter tried to fire the Main charges. Any thoughts?

View attachment 269001 View attachment 269002

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On both flights your rocket was horizontal or nearly so for several seconds at apogee. That is apparent on the barometer channel and would explain the higher reading on the accelerometer one the first data file. The second data file accelerometer base calculate altitude value is garbage.

Bob

So let me get this straight. You had the charges wired backwards. Apogee circuits were connected to the main parachute charges on both altimeters? Main circuits were connected to the drogue charges with staggered altitude settings right?

Soooooo, one of the apogee charges was successful at getting out the main chute. Did the other apogee charge (for the main chute) fire at some time? Now, did you have the aft end upper bay shear pinned to the sustainer or not? If you did have it shear pinned, the main chute may have deployed at apogee with the sustainer attached intact to your main chute bay. On the way down, the Main (now drogue) charges superfluously blew the sustainer from the upper bay? If that had happened, you might have witnessed that at low level.

Now if you didn't have the sustainer shear pinned, the force of the main coming out could have separated everything at apogee and everything would be dangling under the main chute as you'd expect to see after the rocket descended to whatever main deployment altitude you would have set. Again, if you had a visual of the rocket coming in, you might see the charges blowing confetti out the sustainer end as it passed the "Main" deployment altitude.

In the end, I see a very nice picture (Thank Heavens!!) of your rocket on the ground like it had a nominal flight. My final question is did you have live charges in the rocket after it landed? When you say that neither altimeter tried to fire the "main" charges. You mean that both of the Main circuits that were attached to the apogee charges failed to fire and you had live charges in or facing the sustainer after landing?
If that was the case, I'd say your sustainer wasn't pinned, the main chute deployment shook the rocket apart and there is an issue with the Main charge deployment circuit.

Unless.................... There is some logic in the Raven somewhere that if it detects such a slow rate of descent it inhibits the firing of any remaining charges no matter what? :confused2:
If that's the case, I'd check the main firing circuits manually on both Ravens with bare ematches through the setup program and ask Adrian about it.

Four live charges going up and two live charges found at recovery? Kurt

Kurt, All sections were pinned, The charge wiring was switch apogee circuits to main chutes and vis versa. My back up charge was big enough it would shear all of the shear pins in the rocket to get the main out. So the apogee charges (hooked to main chute) went off. When the rocket was recovered it had two unfired charges wired to main circuits (facing the drogue chute).




Bob,
I see now after adjusting the scale it looks right I think. Just seems weird it would keep climbing ravens usually stop calculating once it tails off.

flynfrog said:

Kurt, All sections were pinned, The charge wiring was switch apogee circuits to main chutes and vis versa. My back up charge was big enough it would shear all of the shear pins in the rocket to get the main out. So the apogee charges (hooked to main chute) went off. When the rocket was recovered it had two unfired charges wired to main circuits (facing the drogue chute).




Bob,
I see now after adjusting the scale it looks right I think. Just seems weird it would keep climbing ravens usually stop calculating once it tails off.

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O.K., That makes perfectly good sense then. The main charges had more than enough omphhhh!!! to take it apart completely shearpins
and all.

The question is why didn't the main circuits fire (wired to the drogue charges) as the rocket descended through your main deployment altitude? That's the enigma I would want to settle before depending on the units for a certification attempt. Any ideas yet?

If all the charges had fired as expected, I'd just kick myself,:bangpan: say darn and make sure I'd get the wiring "right" for the L3 attempt. As it stands, I'd be in a "fear, uncertainty and doubt" mode lacking an explanation.

As I mentioned before, I'd check with Adrian or if someone has an idea why the Ravens would behave in that fashion pipe up. Kurt

Tried to send an email to Adrian but it got kicked said his box is full. :/

flynfrog said:

Tried to send an email to Adrian but it got kicked said his box is full. :/

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I am in a hotel room on the way home from Aeronaut with no access to FIP.

Did the voltage drop when it was "supposed" to fire?

no it didnt. Its like it never hit the logic to fire the mains. Maybe because it was falling so slow? I had it on a 96 inch chute.

So apogee charges fired but no main? What were your settings for main deployment?

raven defaults. I think it might have something to do with how it calculated velocity from the accelerometer to trigger Velocity < vel1

flynfrog said:

raven defaults. I think it might have something to do with how it calculated velocity from the accelerometer to trigger Velocity < vel1

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Can you post screenshots of your configuration screens?

Jim

Assuming your Raven #1 was apogee/main and your Raven #2 was 3rd and 4th .....

Looks like the Raven #1 apogee charge is what fired and deployed the chute (correctly, but a little late due to accelerometer error). However, it doesn't look like the 3rd channel fired at barometric apogee?? Don't know why. Was the second apogee charge burned?

The "main" channels didn't fire due to accumulating velocity (per my email) with V<Vel1 going false before the your main altitude.

Jim

In the parameter selection section of the chart. Select the different pyro voltages and you should be able to see what charge fired when by the voltage drop. You may be able to tell if you had a G induced physical main deployment and not an electronic one. That's what I suspect happen.

Both charges were fired on the Apogee circuits.

Per Jims email since the main fired first the accelerometer never turned over to face down. This caused the raven to think it was still accelerating and never made the criteria for the main deploy.

Had I wired the charges correctly the drogue would have turned the altimeters over and should have worked as intended.