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O3400 Min Diameter L3

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rocketace

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Someone please correct me if I am wrong. But I believe the featherweight GPS has a big caveat for 2 stage flights. The ground station can switch frequencies, however it can not track 2 frequencies at the same time. So basically you track the booster and after it lands, you switch the frequency to the sustainer to track it. Software updates could possibly fix this.
 

airforcetp1991

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My understanding is that yes you would have to switch channels to track the other tracker so it would not be truly simultaneous. My thinking is that if I launched monitoring tracker A and it died or shorted or failed for any reason I could switch to the channel for tracker B and still get telemetry as they would both be broadcasting. I have not done this so I could certainly be wrong.

-Tony
 

watheyak

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My understanding is that yes you would have to switch channels to track the other tracker so it would not be truly simultaneous. My thinking is that if I launched monitoring tracker A and it died or shorted or failed for any reason I could switch to the channel for tracker B and still get telemetry as they would both be broadcasting. I have not done this so I could certainly be wrong. -Tony
My understanding is that yes you would have to switch channels to track the other tracker so it would not be truly simultaneous. My thinking is that if I launched monitoring tracker A and it died or shorted or failed for any reason I could switch to the channel for tracker B and still get telemetry as they would both be broadcasting. I have not done this so I could certainly be wrong. -Tony
Or find a buddy with another base station to track the second tracker.

I’ll be there ;)
 

airforcetp1991

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Update to NC Avbay mounting idea. I am planning on an Aluminum Avbay lid as the base of the sled (shown in lime green) and to help with the rigidity of the mounting in the nosecone I think it would be helpful to use a thrust plate (98mm-75mm) epoxied to the inside of the NC. this will give the sled base a strong positive seat all the way around and help distribute the loading at Co2 activation. There will be 2x 6-32 screws that anchor the sled base to the thrust plate using the pre-drilled holes that are normally for a motor mount.

On a slightly different topic I plan to use a female eyenut for the shock cord attachment at the AvBay. I am not sure exactly how I want to secure it to avoid the possibility of it unscrewing during the descent in addition to the nut being tightened against the sled base. My 2 thoughts are

1) Allow the threaded rod to protrude into the eye of the nut just enough to drill a hole across the diameter of the rod and use a cotter pin.

2) Grind a small flat spot on the side of the eyenut and drill/tap a hole in the base next to that flat spot to allow a screw to press against the flat spot to resist the nut unscrewing.

Any BS flags or experience with similar solutions, or preferably better ones?

-Tony

Pic15.JPG
Pic16.JPG
 

OverTheTop

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Or find a buddy with another base station to track the second tracker.
I would suggest getting a buddy to track and locate your booster. It takes much of the stress off sustainer recovery. Get somebody else on camera duty as well.

Haha that works too... I'd hate to have a single overheated iPhone ruin a flight
Write down the landing coordinates provided by the tracking systems. I have seen both a laptop and a phone with the backup of the location data go flat in the field during recovery (not mine). Don't need a battery to keep numbers written on a piece of paper ;).
 

airforcetp1991

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I would suggest getting a buddy to track and locate your booster. It takes much of the stress off sustainer recovery. Get somebody else on camera duty as well.


Write down the landing coordinates provided by the tracking systems. I have seen both a laptop and a phone with the backup of the location data go flat in the field during recovery (not mine). Don't need a battery to keep numbers written on a piece of paper ;).
My design is a single stage so both trackers will be in the nosecone AvBay. I agree though that I would like to have as little to focus on as possible during that time and setup as well for that matter so dividing up roles makes a lot of sense. Hopefully someone has a highspeed camera...

Very good point. I have always screenshot them in case the app crashes but on a longer drive type recovery or a long hike that makes a lot of sense.

-Tony
 

UPscaler

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Twist and Tape is the ONLY way I fly!!
Nothing beats the looks I get when people find out I just electrical tape my batteries to my sleds and twist and tape my switch wires.

Braden
 

jd2cylman

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If they do, they definitely shouldn't. If you have to take it off the pad for whatever reason you've got live charges until you take the av bay apart.

Twin and tape, though, is great. Tape it to your switch band or just tape the wires together and let it go.

Braden
I twist and tuck on everything. The key is to tuck into another hole. Tape over the exposed wires to keep them from moving. But there are wires that you can get ahold of if needed.
As far as taping the wire ends on the outside, sure, if you’re not going close to Mach. Had that happen to me once. Pulled the tape off AND pulled the wires apart. That’s when I learned to tuck them back inside...
Luckily, the Strat had a brownout capacitor and still popped out the drogue.
 
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OverTheTop

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Twist and tuck may have its place (not really IMHO ;) ) but not above M3. Just asking for trouble having anything in the airstream at those velocities.
 
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jd2cylman

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Twist and tack may have its place (not really IMHO ;) ) but not above M3. Just asking for trouble having anything in the airstream at those velocities.
Sad part is I have a pair of Finger Tech switches somewhere in the house... 🤔
And that’s all I know about them.
 

UPscaler

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I twist and tuck on everything. The key is to tuck into another hole. Tape over the exposed wires to keep them from moving. But there are wires that you can get ahold of if needed.
As far as taping the wire ends on the outside, sure, if you’re not going close to Mach. Had that happen to me once. Pulled the tape off AND pulled the wires apart. That’s when I learned to tuck them back inside...
Luckily, the Strat had a brownout capacitor and still popped out the drogue.
Interesting, I've had several mach+ flights that I haven't had issues with.

Braden
 

cerving

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It's best to eliminate possible points of failure. Just because it's worked "so far" doesn't mean that it isn't going to fail in the future. All wiring should be secured so it can't move, any terminal block connections should be checked before every flight, and battery connectors should be taped or otherwise secured so they can't pull apart in flight. That goes for the wires inside the connectors, too... I've seen them pull out of some of the cheapo Chinese JST clones.

Twist and tape/tuck inherently fails the "secure everything" test... even if you tape the beejeebers out of it a supersonic flight could easily rip the tape right off of it.
 

Steve Shannon

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Just a friendly reminder that the design must be approved by your TAPs before construction begins.
It certainly appears that you are doing your homework and learning a lot, but understand that TAPs will also consider your experience and judgement. It’s entirely possible they might feel that you are extending your plans way beyond your actual experience. Personally, I prefer to see a person gain knowledge and experience simultaneously and in manageable increments that form a permanent foundation instead of trying a flight based on a large step of theoretical knowledge without corresponding flight experience, but there have been similar ambitious flights in the past.
No matter what, good luck!
 

plugger

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View attachment 460778

A tiny set screw that wasn't quite flush caused the charring and downstream surface imperfections.

Wires would certainly do the same or worse. Until they're melted off, anyway...
+1
I don't snip the heads of nylon shear pins for my flights. But flying to ~Mach 2.6 caused a nylon shear pin head to melt and smear downward.
 

FredA

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It’s entirely possible they might feel that you are extending your plans way beyond your actual experience.
Good Post Steve -- the questions asked here left me feeling this is too much of a reach for a cert flight.
 

airforcetp1991

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Just a friendly reminder that the design must be approved by your TAPs before construction begins.
It certainly appears that you are doing your homework and learning a lot, but understand that TAPs will also consider your experience and judgement. It’s entirely possible they might feel that you are extending your plans way beyond your actual experience. Personally, I prefer to see a person gain knowledge and experience simultaneously and in manageable increments that form a permanent foundation instead of trying a flight based on a large step of theoretical knowledge without corresponding flight experience, but there have been similar ambitious flights in the past.
No matter what, good luck!
Well said. While I have done the deployment testing and I do have a NC for prototyping purposes I certainly won't start building without TAP approval.

-Tony
 

airforcetp1991

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+1
I don't snip the heads of nylon shear pins for my flights. But flying to ~Mach 2.6 caused a nylon shear pin head to melt and smear downward.
I have not snipped them in the past either but it seems like it makes sense about Mach 2.5 ish and if it doesn't weaken them why not.

-Tony
 

Steve Shannon

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Well said. While I have done the deployment testing and I do have a NC for prototyping purposes I certainly won't start building without TAP approval.

-Tony
If I were your TAP, I would work with you to come up with a plan to test the different new concepts and techniques you are exploring. Less expensive proof of concept flights could improve success for your certification flight (as much as possible in Rocketry). It might also result in less stress for you and your TAPs :).
 

airforcetp1991

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Had some free time to mess around with Avbay mock ups, I like this layout the best I think. It keeps the antennas the furthest from the all thread and provides the best battery mounting options in my opinion.

Untitled Project 99.jpg
 

TonyL

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It is a good looking sled. If I had the room I would get the tracker antennas above the CO2 cartridges.
 

airforcetp1991

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It's beautiful. But looks really heavy.
True and that was (mostly) on purpose. The red vertical sled structure is 3D printed so that will be light and all the avionics and batteries are very light as well. The aluminum sled base is much lighter with all the holes machined in it and I figure the thrust ring will lose some weight as well as the diameter is reduced some. The Co2 systems are by are by far the heaviest component. Could I use BP, yes, but then I would have to add ballast in the nose to move the CG. All in all it should be under 2 pounds easily I hope. I know it is over built but if both of those Co2 systems fire near simultaneously there will be 400# of force that the sled base has to withstand and having the thrust ring epoxied in the NC will made that load a lot easier to distribute I think. There will definitely me more changes to come I'm sure of that.
 

airforcetp1991

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It is a good looking sled. If I had the room I would get the tracker antennas above the CO2 cartridges.
I would agree but there isn't much room at all left with the same diameter and making the sled longer would get the antennas closer to the all thread. On that note I talked with Adrian at FeatherWeight and he said they flew a rocket successfully to 134K' with the antenna 1 cm from the all thread. Given signal attenuation in the atmosphere is roughly proportional to 1/distance^2 I think that should give a large margin of safety for my signal reception.
 
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