[B]Flying Sub from voyage to the bottom of the sea[/B] - Page 2

shin · Nov 02, 2009, 09:36 AM

Sweet, awesome job
would love to see some video if able

AlbertChia · Nov 02, 2009, 10:56 AM

Hi Dave,

Thank you very much for the photos, can you give us the close up of the underside and the outlet directional control system. It would be nice to also give us the layout of your electronics inside the otters box.

By the look of it, your rudder control is by varaible speed from the two drive. Am I right?

Looking forward to getting more information from you.

Regards

Subdave · Nov 02, 2009, 01:46 PM

I will try and put together some basic info on my build.
Here is one early video I did while testing the roll axis.
It took a few tries to get the trimming correct.

Dave.

SilentHunter · Nov 02, 2009, 07:49 PM

Im really liking that, great job man

I have been dying to do something similar, but I have too much to do right now to start one... So your nozzles are 2D correct, just for pitch and roll? just the stock Graupner jet nozzles. Have you done the CG/MAC calc on it? Water is the same as air, just 3k or so more times as thick.

like it, nice logical layout too

AlbertChia · Nov 02, 2009, 08:06 PM

Hi Silent Hunter,

How do you do the Calculation on the CG/CP(What is this CP), do you have the formula?

SilentHunter · Nov 02, 2009, 08:20 PM

Hi,

Same as an airplane, in this case it would be like a mix of lifting body and flying wing. MAC is basically the point where all the lift occurs from flying through the water. So on an airplane wing, you want the MAC and CG (static weight balance) to be in the same point.

Let me check with my fluid dynamics master before I elaborate more...

Im sure i got my wires crossed, Im referring to MAC (mean aerodynamic center)

teryn1 · Nov 02, 2009, 10:54 PM

In the world of aircraft flying in the atmosphere:

CP = center of presssure. center of pressure is a location where the vehicle lift force is represented as a single force vector and the moment is zero. This point changes with flight condition (angle of attack, altitude and Mach number).

AC = Aerodynamic center is a point where the pitching moment is invariant with lift coefficient (angle of attack). The difference in magnitude between the AC and center of gravity (CG) determines the amount of pitch stability the aircraft has for a given vehicle geometry.

MAC = mean aerodynamic chord. is a chord length (calculated using equations) that is used to compare performance for different wing shapes.

SilentHunter · Nov 02, 2009, 11:54 PM

well there you have it

The same needs to be applied to balancing this "sub" because we want it to fly underwater like a plane in terms, not like a regular sub.

Subdave · Nov 03, 2009, 09:04 AM

The Graupner jet nozzles are 2D. Just turned 90 deg so the thrust is up and down not right and left.
I use the X-mixer in my radio on the pitch and roll but set up for rudder on the right stick. I use an external X-mixer on the two ESC's to control the throttle and rudder. I even have reverse although very slow. The water is ducted in through the open front windows and reversing the throttle pushes the water out the windows. I started with brushless motors but it was way to powerful and hard to control. The brushless ESC's did not really like the X-mixer either. I have two Mini-C 300 sized motors and two Micro Viper ESC's now. It still has good speed and not as hard to fly.
I was told to keep my weight close to the CG if I wanted to roll but it was so hard to control I ended up putting more foam out in the fins for stability.
She does not roll as good now but at least I can run.
It really helps to know how to fly well and I don't.

More later. Dave.

Nov 02, 2009, 07:49 PM	#19
SilentHunter under construction Join Date: Aug 2003 Location: Green valley AZ Posts: 998	Im really liking that, great job man I have been dying to do something similar, but I have too much to do right now to start one... So your nozzles are 2D correct, just for pitch and roll? just the stock Graupner jet nozzles. Have you done the CG/MAC calc on it? Water is the same as air, just 3k or so more times as thick. like it, nice logical layout too Last edited by SilentHunter; Nov 02, 2009 at 08:38 PM.

Nov 02, 2009, 08:20 PM	#21
SilentHunter under construction Join Date: Aug 2003 Location: Green valley AZ Posts: 998	Hi, Same as an airplane, in this case it would be like a mix of lifting body and flying wing. MAC is basically the point where all the lift occurs from flying through the water. So on an airplane wing, you want the MAC and CG (static weight balance) to be in the same point. Let me check with my fluid dynamics master before I elaborate more... Im sure i got my wires crossed, Im referring to MAC (mean aerodynamic center) Last edited by SilentHunter; Nov 02, 2009 at 08:38 PM.

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Nov 02, 2009, 09:36 AM	#16
shin Registered User Join Date: Sep 2006 Posts: 135	Sweet, awesome job would love to see some video if able

Nov 02, 2009, 10:56 AM	#17
AlbertChia Registered User Join Date: May 2009 Location: Singapore Posts: 20	Hi Dave, Thank you very much for the photos, can you give us the close up of the underside and the outlet directional control system. It would be nice to also give us the layout of your electronics inside the otters box. By the look of it, your rudder control is by varaible speed from the two drive. Am I right? Looking forward to getting more information from you. Regards

Nov 02, 2009, 01:46 PM	#18
Subdave Registered User Join Date: Mar 2005 Location: Rochester NY Posts: 108	I will try and put together some basic info on my build. Here is one early video I did while testing the roll axis. It took a few tries to get the trimming correct. Dave.

Nov 02, 2009, 08:06 PM	#20
AlbertChia Registered User Join Date: May 2009 Location: Singapore Posts: 20	Hi Silent Hunter, How do you do the Calculation on the CG/CP(What is this CP), do you have the formula?

Nov 02, 2009, 10:54 PM	#22
teryn1 Registered User Join Date: Aug 2004 Location: Green Valley, AZ Posts: 123	In the world of aircraft flying in the atmosphere: CP = center of presssure. center of pressure is a location where the vehicle lift force is represented as a single force vector and the moment is zero. This point changes with flight condition (angle of attack, altitude and Mach number). AC = Aerodynamic center is a point where the pitching moment is invariant with lift coefficient (angle of attack). The difference in magnitude between the AC and center of gravity (CG) determines the amount of pitch stability the aircraft has for a given vehicle geometry. MAC = mean aerodynamic chord. is a chord length (calculated using equations) that is used to compare performance for different wing shapes.

Nov 02, 2009, 11:54 PM	#23
SilentHunter under construction Join Date: Aug 2003 Location: Green valley AZ Posts: 998	well there you have it The same needs to be applied to balancing this "sub" because we want it to fly underwater like a plane in terms, not like a regular sub.

Nov 03, 2009, 09:04 AM	#24
Subdave Registered User Join Date: Mar 2005 Location: Rochester NY Posts: 108	The Graupner jet nozzles are 2D. Just turned 90 deg so the thrust is up and down not right and left. I use the X-mixer in my radio on the pitch and roll but set up for rudder on the right stick. I use an external X-mixer on the two ESC's to control the throttle and rudder. I even have reverse although very slow. The water is ducted in through the open front windows and reversing the throttle pushes the water out the windows. I started with brushless motors but it was way to powerful and hard to control. The brushless ESC's did not really like the X-mixer either. I have two Mini-C 300 sized motors and two Micro Viper ESC's now. It still has good speed and not as hard to fly. I was told to keep my weight close to the CG if I wanted to roll but it was so hard to control I ended up putting more foam out in the fins for stability. She does not roll as good now but at least I can run. It really helps to know how to fly well and I don't. More later. Dave.