SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Feb 22, 2012, 12:55 AM
Registered User
Palo Alto, California, United States
Joined Jan 2003
1,055 Posts
I just finished building a second prototype of the electric V-Bat with a smaller duct and larger wing. Here is a video showing it hovering indoors in a confined area. It has a 6 ft span and weighs 12 lbs as flown in the video.

Steve

eV-Bat Hovering Indoors (0 min 52 sec)
mlbco is offline Find More Posts by mlbco
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 22, 2012, 04:36 AM
Registered User
Joined Jan 2010
26 Posts
Quote:
Originally Posted by mlbco View Post
I just finished building a second prototype of the electric V-Bat with a smaller duct and larger wing. Here is a video showing it hovering indoors in a confined area. It has a 6 ft span and weighs 12 lbs as flown in the video.

Steve

http://www.youtube.com/watch?v=d3myqHdEwjA
nice work,Steve
The new duct is shorter ,why do you make this adjustment, the weight or the drag?
zhaohongf22 is offline Find More Posts by zhaohongf22
Reply With Quote
Old Feb 22, 2012, 05:33 AM
DIY Mania from Taiwan
Taiwan
Joined Aug 2011
1,939 Posts
Very much impressed again,thanks for sharing
you must have spent a lot of efforts for the job
regards
Sam
samwei1950 is online now Find More Posts by samwei1950
Reply With Quote
Old Feb 23, 2012, 12:36 AM
Registered User
Palo Alto, CA, USA
Joined Nov 2000
1,019 Posts
That is pretty awesome Steve. Good job.

Kasra
kasra is offline Find More Posts by kasra
RCG Plus Member
Reply With Quote
Old Feb 24, 2012, 01:35 PM
Registered User
Joined Jan 2012
14 Posts
Steve,

I have a question for you: how much static thrust increase of your V-bat compared to open propeller same size? Why you decide to use symmetrical shape instead of optimized shape? how many channel radio you use?
zebra100 is offline Find More Posts by zebra100
Reply With Quote
Old Feb 24, 2012, 06:49 PM
Registered User
Palo Alto, California, United States
Joined Jan 2003
1,055 Posts
Quote:
Originally Posted by zebra100 View Post
Steve,

I have a question for you: how much static thrust increase of your V-bat compared to open propeller same size? Why you decide to use symmetrical shape instead of optimized shape? how many channel radio you use?
We are using a cut-down propeller in the duct so I don't have a direct comparison of the propulsion system for the propeller with versus without a duct. A well designed duct produces a given amount of thrust for less power than an exposed propeller and in our case the figure of merit (FOM) in hover is close to 90%. The FOM is the ratio of ideal power to the actual power, where the ideal power is defined as the minimum induced power required to produce a specified thrust in hover. 90% FOM is higher than most exposed rotor systems (typically 75%).

The duct cross section is not symmetrical, it is designed for both efficient hover and low drag in high speed flight. I tried to keep the duct as small as possible to minimize weight and drag, while still providing the function of a ducted fan and the aircraft's tail.

The radio is 4 channels set up like a helicopter's controls. There is an on-board computer with GPS, magnetometer, gyros, altimeter, airspeed, and accelerometers that provides attitude stability when hovering. Eventually, this computer will fly the V-Bat autonomously with no human control input. The duct has 8 servos and the ailerons have 2 servos, but there are only 4 controls (roll, pitch, yaw, throttle).

Steve
mlbco is offline Find More Posts by mlbco
Reply With Quote
Old Feb 24, 2012, 07:59 PM
Registered User
Joined Jan 2010
26 Posts
Can it fly autonomously in the transition between vertical and horizontal flight?
Kevin
zhaohongf22 is offline Find More Posts by zhaohongf22
Reply With Quote
Old Feb 24, 2012, 08:53 PM
Registered User
Palo Alto, California, United States
Joined Jan 2003
1,055 Posts
Quote:
Originally Posted by zhaohongf22 View Post
Can it fly autonomously in the transition between vertical and horizontal flight?
Kevin
The larger version can hover autonomously and both versions have been transitioned under manual control. We are finishing up the flight control for full autonomous flight now.

Steve
mlbco is offline Find More Posts by mlbco
Reply With Quote
Old Feb 24, 2012, 10:11 PM
Registered User
Joined Jan 2010
26 Posts
Will the transition be achieved by a stall-and-tumble maneuver or continuous ascent transition?

Kevin
zhaohongf22 is offline Find More Posts by zhaohongf22
Reply With Quote
Old Feb 25, 2012, 11:52 AM
Registered User
Joined Jan 2012
14 Posts
Thank you very much for the quick reply, Steve. I'm very impressed with the V-bat. How can you cut the blue foam curve so smooth for the shroud?
zebra100 is offline Find More Posts by zebra100
Reply With Quote
Old Feb 26, 2012, 11:30 AM
Registered User
Terry S's Avatar
Bridgwater, UK
Joined May 2003
673 Posts
Why the need for 8 control vanes? and the boxes round each one?

Thanks, Terry
Terry S is offline Find More Posts by Terry S
Reply With Quote
Old Mar 01, 2012, 12:14 AM
Registered User
Palo Alto, California, United States
Joined Jan 2003
1,055 Posts
The type of autonomous transition will depend on the amount of excess thrust available. UAVs typically operate with maximum fuel and payload and don't have anywhere near as much excess thrust as model airplanes. With less thrust available the transition will probably be a smooth ascent or descent.


The blue foam duct was cut using a custom set of cutting bits mounted in a milling machine. The foam was rotated on a special table while the mill cut the foam duct. The duct was cut in several stages using the appropriate bit.

The vanes in the duct and the extra attachments are needed to provide adequate control authority in the roll axis (i.e. axis along the fuselage). When there is wind the wings tend to roll the V-Bat so that the wing surface is perpendicular to the wind. Significant vane authority is required to minimize this in high winds.

Steve
mlbco is offline Find More Posts by mlbco
Reply With Quote
Old Mar 01, 2012, 12:24 AM
Registered User
Palo Alto, California, United States
Joined Jan 2003
1,055 Posts
Here are some photos of the duct construction showing the hollowed out foam duct and the underlying structure.

Steve
mlbco is offline Find More Posts by mlbco
Reply With Quote
Old Mar 01, 2012, 05:33 AM
Registered User
France
Joined Nov 2008
77 Posts
Quote:
Originally Posted by mlbco View Post

The vanes in the duct and the extra attachments are needed to provide adequate control authority in the roll axis (i.e. axis along the fuselage). When there is wind the wings tend to roll the V-Bat so that the wing surface is perpendicular to the wind. Significant vane authority is required to minimize this in high winds.

Steve
Hi Steve,

Do you have a roll mix input in each of the 8 vanes ?

Or would you explain ( just a bit, I don't want the code's formula ) the % mixing used in the 8 vanes, yaw, pitch, roll ?
lebrett is offline Find More Posts by lebrett
Reply With Quote
Old Mar 01, 2012, 08:27 PM
Registered User
Palo Alto, California, United States
Joined Jan 2003
1,055 Posts
Lebrett,

All the vanes move the same direction for roll control. For pitch and yaw it's just like rudder and elevator on an airplane except that the vanes at the 45 deg radial stations only move 0.707 as much as the primary vanes.

Steve
mlbco is offline Find More Posts by mlbco
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log Peter Rakes's DFW-C.V 2nd prototype BaZsiX Scale Kit/Scratch Built 32 Sep 10, 2011 06:28 PM
Discussion changing from 4.8 v to 6 v reciever bat mspaterick Fuel Warbirds 2 Apr 28, 2010 06:01 PM
is my V-bat a dud design? tazz Beginner Training Area (Aircraft-Electric) 3 Jun 08, 2002 03:01 PM
Anyone have the Thunder Tiger V-Bat Fast-Forward Electric Plane Talk 0 Apr 22, 2002 05:06 PM