Where do you place your Mobius shroud?

The Rocketry Forum

Help Support The Rocketry Forum:

dhkaiser

Well-Known Member
Joined
Nov 27, 2014
Messages
413
Reaction score
8
I am getting ready to mount a couple Mobius shrouds on my 3 and 4" Mac Performance rockets. Where do you mount yours? At the CG? Or someplace else? Other than moving the CG rearwards any down side of placing it between the forward and center CR's?
 

timbucktoo

Well-Known Member
Staff member
TRF Supporter
Global Mod
Joined
Jun 13, 2014
Messages
8,775
Reaction score
1,566
Location
Cocoa Beach
Are these DD rockets? I like to mount mine on the payload well forward of the CG. You can see apogee event. But as a rule of thumb, anywhere at or forward of the CG would be fine.
 

Buckeye

Well-Known Member
Joined
Sep 6, 2009
Messages
2,832
Reaction score
607
I am in favor of any location that does not induce roll, which I have yet to figure out. I like to think my fins are pretty darn straight, yet my video footage spins like a nausea-inducing carnival ride. So far, I have put my camera up high on the payload. Next time, I will try lower on the booster, as you suggest. This would be a good NARAM R&D project.
 

dhkaiser

Well-Known Member
Joined
Nov 27, 2014
Messages
413
Reaction score
8
Are these DD rockets? I like to mount mine on the payload well forward of the CG. You can see apogee event. But as a rule of thumb, anywhere at or forward of the CG would be fine.
One DD, one SD. I like your idea of above the booster to record separation. In the past I have taped 808 x2 on LPR's, one up and one pointed down.
 

StanO

Well-Known Member
TRF Supporter
Joined
Dec 6, 2010
Messages
141
Reaction score
6
L3 Appogee Eject.jpgI flew my rocket on L2 motors and the rocket went straight up. For my L3 cert flight I mounted the camera above the booster on the same rocket as I wanted to see deployment. Rocket did the hula for me . Now I know why. I hadn't considered the camera shroud as the cause.
 

Dave A

Lifetime Supporter
TRF Lifetime Supporter
Joined
Jan 22, 2013
Messages
1,190
Reaction score
155
I mount mine about midways on my payload so I can see the apogee event.
I plan to add one between the fins, looking up to see it from another angle.

I had a question about roll, too.
I make jigs to set my fins and they are as close to correct as can be.
-9" Patriot, 70lbs, video showed it only rolled 200 deg all the way to apogee. Winds were calm on the last flight of the day.
-6" IRIS and 6" Ult Endeavor, spun like mad (bordering dizziness), winds were wicked at certain altitudes.

Is roll made worse with heavy crosswinds during ascent?
 

DavieRockets

Well-Known Member
Joined
Mar 31, 2011
Messages
483
Reaction score
10
I mount my shrouds between two fins. But first i install the camera and tape it in position and make a recording while holding the booster horizontal and panning. I note the position audibly on the video saying "3 inches forward of base" for instance, using a numer of mounting positions. On playback I can choose the most pleasing view, eliminating too much fin in the frame. I have learned that eliminating all the fin view puts the camera so far aft that the bright glow of exhast plume washes out the video until burnout. Camera induced roll seems to be minimal on most flights.
 

timbucktoo

Well-Known Member
Staff member
TRF Supporter
Global Mod
Joined
Jun 13, 2014
Messages
8,775
Reaction score
1,566
Location
Cocoa Beach
Is roll made worse with heavy crosswinds during ascent?
I just launched a rocket yesterday with 15-20 MPH winds. Camera taped to payload with gaffers tape. Still reviewing video but on boost, it rolled maybe maybe 180 degress and then on coast it rolled in the opposite direction about the same amount.
 

Buckeye

Well-Known Member
Joined
Sep 6, 2009
Messages
2,832
Reaction score
607
Camera induced roll seems to be minimal on most flights.
Well, I'd like to know the secret. I taped or shrouded a #16 camera on 3 rockets: 2.2", 2.6", and 4". All were mounted on the payload tube. All had 3 fins. All had many rotations, with the 2.2" being the worst of the bunch (the camera was nearly size of a fin, so I am not surprised.) I have a couple theories to reduce roll with a camera shroud that I will test out in the future:

  • Put the camera on the booster, around the CP
  • Use 4 fin rockets
  • User large fin, overstable rockets
  • Use large diameter rockets
  • Use low thrust motors
 

timbucktoo

Well-Known Member
Staff member
TRF Supporter
Global Mod
Joined
Jun 13, 2014
Messages
8,775
Reaction score
1,566
Location
Cocoa Beach
Here is my video from yesterday. Mobius taped to payoad of 3" rocket, 3 fins. No spin!

[video=youtube;IfXrUKcsdyQ]https://www.youtube.com/watch?v=IfXrUKcsdyQ[/video]
 

Buckeye

Well-Known Member
Joined
Sep 6, 2009
Messages
2,832
Reaction score
607
Show off. :)

What is your cp and cg relationship?
 

timbucktoo

Well-Known Member
Staff member
TRF Supporter
Global Mod
Joined
Jun 13, 2014
Messages
8,775
Reaction score
1,566
Location
Cocoa Beach
thanks!

With that motor, Stability of 2.54 calibers.
CG = 60.048"
CP = 67.943"

I am really not sure if it's the camera causing spin. I see rockets with no cameras spin like crazy off the pad. Another guy I fly with has actually put tape on the trailing edges of fins on 1 side only to counter the spin and has worked remarkedly well but it was a trial & error process.
 

Buckeye

Well-Known Member
Joined
Sep 6, 2009
Messages
2,832
Reaction score
607
Here is my video from yesterday. Mobius taped to payoad of 3" rocket, 3 fins. No spin!

[video=youtube;IfXrUKcsdyQ]https://www.youtube.com/watch?v=IfXrUKcsdyQ[/video]
Nice video. Dashware? Where did you find that rolling altitude gauge on the right? I don't see that one in Dashware.
 

noffie79

Well-Known Member
Joined
Jul 25, 2015
Messages
1,340
Reaction score
13
I have a Mobius that I use with a shroud from Additive Aerospace. I have it mounted forward of the CG. There's some spin, about two revolutions per mile. Not sure if that's caused by the camera/shroud or not. Here's my flight from Saturday with my Wildman Demon.
https://youtu.be/K9n4SjV_m-s
 

timbucktoo

Well-Known Member
Staff member
TRF Supporter
Global Mod
Joined
Jun 13, 2014
Messages
8,775
Reaction score
1,566
Location
Cocoa Beach
Nice video. Dashware? Where did you find that rolling altitude gauge on the right? I don't see that one in Dashware.
Yes, Dashware. Down toward bottom of Gage Toolbox you should see it, UAV Tape Altitude.
 

Buckeye

Well-Known Member
Joined
Sep 6, 2009
Messages
2,832
Reaction score
607
Yes, Dashware. Down toward bottom of Gage Toolbox you should see it, UAV Tape Altitude.
Ah, I see it now. Thanks.

I'll post my spinny video soon. Not as eye-pleasing as the ones from you guys.

Another thought. My camera attempts have all been on fairly lightweight cardboard rockets with plastic cones. Maybe I need some heavy fiberglass birds to resist the roll a little better.
 

noffie79

Well-Known Member
Joined
Jul 25, 2015
Messages
1,340
Reaction score
13
Ah, I see it now. Thanks.

I'll post my spinny video soon. Not as eye-pleasing as the ones from you guys.

Another thought. My camera attempts have all been on fairly lightweight cardboard rockets with plastic cones. Maybe I need some heavy fiberglass birds to resist the roll a little better.
I think you can still get great video on a cardboard and plastic rocket. Here's one from onboard my Estes PSII Ventris. This one doesn't have a shroud. Just taped on with masking and electrical tape. And no specific placement. Anywhere in front of CG is all I make sure of.
https://youtu.be/S4tMZNhKVFY
 

Buckeye

Well-Known Member
Joined
Sep 6, 2009
Messages
2,832
Reaction score
607
Oh sure. You guys with your fancy-shmancy, non-spinning, perfect videos. Harumph! :wink:

Here is a link to a draft video. This is the worst one in my collection. Hold your stomach, it spins like crazy. Rocket is a LOC Vulcanite (2.2") on H170. #16 720p camera taped to the payload section. GPS data on the left, altimeter data on the right:

https://youtu.be/CTxky7F6UKE

Maybe my fins are not as straight as I think they are, though I use a 120 deg jig. This flight was angled a couple degrees down range (North), wind is about 10 mph from the West.
 
Top