Using 3D PLA mobius camera shroud on Mach 1.4 flight

I know there is a recent thread asking about camera shroud options for "Supersonic" flights, however I have a specific scenario.

3" filament wound fiber glass airframe, Landru's 3d PLA mobious shroud @ Mach 1.4. Mounted using 4-40 316 machine screw with stainless self clinching nuts. The holes 3D printed into the shroud don't leave much thickness to work with and unfortunately not much space for a washer to spread the load, but there are 4 mounting points.

Survive or not? Ideally I would like to hear from those of you who have actually done this yourself or witnessed it first hand, vs. all of the theoretical numbers and opinions.

I have two flights with my 3" Darkstar on an L935 and Sharon also has one. Although the Stratologger data is a little shaky, sims indicate over 1300 fps which is around 1.25 mach. We both fly the mobius shroud on those rockets. I will tell you something that doesn't work, electrical tape on a keychain camera:

Yeah, there was a camera there before the flight....

I also had a mobius on my L3 cert flight, but it only went about .9 mach with an M1297.

https://youtu.be/VoshDtQLNys

I haven't put the shroud on my 3" carbon fiber Mongoose 75, it's the only rocket that goes faster, and that's NOT gonna happen for obvious reasons...

Use the green Hard to stick to surfaces masking tape from 3M.
https://www.amazon.com/dp/B00004Z4AY/?tag=skimlinks_replacement-20

JD

Wayco said:

I have two flights with my 3" Darkstar on an L935 and Sharon also has one. Although the Stratologger data is a little shaky, sims indicate over 1300 fps which is around 1.25 mach. We both fly the mobius shroud on those rockets. I will tell you something that doesn't work, electrical tape on a keychain camera:

Yeah, there was a camera there before the flight....

I also had a mobius on my L3 cert flight, but it only went about .9 mach with an M1297.

https://youtu.be/VoshDtQLNys

I haven't put the shroud on my 3" carbon fiber Mongoose 75, it's the only rocket that goes faster, and that's NOT gonna happen for obvious reasons...

Click to expand...

Wayco said:

I have two flights with my 3" Darkstar on an L935 and Sharon also has one. Although the Stratologger data is a little shaky, sims indicate over 1300 fps which is around 1.25 mach. We both fly the mobius shroud on those rockets.

Click to expand...

Actually the rocket in question is a 3" Darkstar so that makes me feel more confident. I am wanting to use the camera on the Darkstar with the new Loki L-1040, which OR assumes Mach 1.36. How did you secure the shroud to the airframe?

Wayco said:

I will tell you something that doesn't work, electrical tape on a keychain camera: Yeah, there was a camera there before the flight....

Click to expand...

Too funny I was looking at the picture before I read your post and was thinking, hmm I don't see a camera there.

Wayco said:

I also had a mobius on my L3 cert flight, but it only went about .9 mach with an M1297. https://youtu.be/VoshDtQLNys

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I remember watching that video when you posted it, awesome flight.

Wayco said:

I haven't put the shroud on my 3" carbon fiber Mongoose 75, it's the only rocket that goes faster, and that's NOT gonna happen for obvious reasons...

Click to expand...

I hear you, as much as I would love to get some video of a MD launch, having something hanging off the side of the airframe kind of defeats the purpose of MD...that is if you're a MD purest.

mpitfield said:

Actually the rocket in question is a 3" Darkstar so that makes me feel more confident. I am wanting to use the camera on the Darkstar with the new Loki L-1040, which OR assumes Mach 1.36. How did you secure the shroud to the airframe?

Too funny I was looking at the picture before I read your post and was thinking, hmm I don't see a camera there.

I remember watching that video when you posted it, awesome flight.

I hear you, as much as I would love to get some video of a MD launch, having something hanging off the side of the airframe kind of defeats the purpose of MD...that is if you're a MD purest.

Click to expand...

I had to go into the rocket room to check, drag out my Blackstar and measure. I'm about an inch short of having enough room to put that motor in mine. I suppose you built yours to accommodate it? Must be flying it drogue-less, with a tiny shock cord. Probably a good thing an L1040 doesn't fit in mine, or I would be spending about $500 today....
I definitely want to see that video!
My shroud is attached using the screws it came with. Drilled out 7/64 holes and screwed the provided screws in, also drilled out the hole for the screw that attaches the lid, it won't go all the way in if you don't. Never considered it blowing off. I really don't think you have anything to worry about there, but that's just my opinion.
I also went back and checked, my Extreme has also flown on an M1780, and it was a slightly faster flight than my cert flight.

The only total failure I am aware of is a 3" minimum diameter flying on an AT M1550R. He doesn't know exactly how fast but it was around M2. He never said whether it melted or tore off.

Also, one warped on an O motor flight as well, but I'm guessing it was too close to the motor and was damaged by heat soak post flight.

If you are concerned about the web thickness on the shroud, consider using some 3M VHB tape as an additive mount. I use just the tape and not had one fall off yet.

The VHB 3m tape is very good stuff. It's a two sided foam that can buy in Auto parts stores in the paint section. Most often used for automotive trim. I havent used it om my camera mount yet but use it for attaching rear sponsons on RC Race boats that go 75 mph with water beating off of them with no problems" I'd be careful using it on a painted rocket unless you keep it there permanent. Might take the paint with it if you pry it off.

Wayco said:

I had to go into the rocket room to check, drag out my Blackstar and measure. I'm about an inch short of having enough room to put that motor in mine. I suppose you built yours to accommodate it? Must be flying it drogue-less, with a tiny shock cord. Probably a good thing an L1040 doesn't fit in mine, or I would be spending about $500 today....
I definitely want to see that video!
My shroud is attached using the screws it came with. Drilled out 7/64 holes and screwed the provided screws in, also drilled out the hole for the screw that attaches the lid, it won't go all the way in if you don't. Never considered it blowing off. I really don't think you have anything to worry about there, but that's just my opinion.
I also went back and checked, my Extreme has also flown on an M1780, and it was a slightly faster flight than my cert flight.

Click to expand...

Below is a pic of my Dark Star in it's current condition, marked for drilling holes, and the 54/2800 case with the extended bulkhead. It is the original 3" dual deploy limited run, the one with the aluminum tip nosecone. However I purchased the new lighter nosecone with the phenolic tip, which is what is on the rocket now. There is a piece of blue tape just below the double ring of blue tape, which indicates where the bottom of the AV bay is. So as you can see I have about 6-7" of room for the drogue and harness, which is a Onebadhawk Kevlar 25' 3 loop 11/32 harness. The threaded rod sticking out the of the top of the extended bulkhead on the motor is an adapter I had made to go from 1/4-20 on the bulkhead to the MD aeropack 5/16-18 thread, which I am using in another build so it will be removed for this rocket. The retainer I am using on this rocket is the GLR slimline tailcone retainer, which just fits the outside snap-ring on the Loki case.

OR has it simulating to 15K @ Mach 1.36 but I take that with a grain of salt, so we will see what we get. It will have dual trackers and dual altimeters so between them 3 different sources for recording the flight statistics.

View attachment 261383

Wayco said:

I also had a mobius on my L3 cert flight, but it only went about .9 mach with an M1297. [/FONT][/SIZE]

https://youtu.be/VoshDtQLNys

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Nice. Apogee altitude?

Winston said:

Nice. Apogee altitude?

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Flew to 13,124 ft. and was recovered in a millet field 1.5 miles away using an Eggfinder, Android phone with the "Rocket Tracker" app.

Here's the build thread:

https://www.rocketryforum.com/showthread.php?66950-Wayco%92s-Dark-Star-Extreme

My mistake on that motor, I thought it fit in the 54/4000 casing. You have plenty of room in that rocket.
I agree on the OR sim, most of mine sim faster than they go. Did you add the shroud to the simulated rocket?

Wayco said:

Did you add the shroud to the simulated rocket?

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I tired to as best as I could using OR so far, I have not tried in RS.

I first tried to add it as a really thick fin but it only allows the fin thickness of I recall less than .5 and the width is just shy of an inch. I even tried to import .jpeg image when I was setting it up as a fin then I was going to stack one fin beside another until I achieved the thickness but I could not import the profile. I ended up adding is a launch lug that is sold but still round. but it is at least the correct width and length. However with this method I could not simulate the forward aerodynamic angle of the shroud.

So if you or anyone else has any ideas on how to simulate this in OR or RS I would live to hear them.

How about modelling it as a very large launch button?

The fin calculations most likely assume attached flow around the trailing edge, so are probably not ideal for accuracy when modelling a blunt base protrusion.

High Mach for very long leads to melted plastic shrouds. Derrick Deville I believe demonstrated that on a flight one time. Momentary exposure for a few seconds shouldn't be a problem. Kurt

I just realized I replied into a very old thread. My apologies everyone.

I'm also interested in this - what do folk think, for a rocket where you don't mind a permanent attachment, about putting a layer of glass or carbon over the shroud to smooth the airflow a bit and protect it from some of the heat.

Zebedee said:

I'm also interested in this - what do folk think, for a rocket where you don't mind a permanent attachment, about putting a layer of glass or carbon over the shroud to smooth the airflow a bit and protect it from some of the heat.

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The Mobius has a feature for ext power and a setting to record when powered - Lens can be removed and a extension cable is available. Will do mine with a mini shroud for the lens only.. and use a external switch.

Kenny