HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 29, 2011, 06:55 PM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
Discussion
Scratchbuilt vector kite: ultra slow flier

This is not a build log per se since I've already done the building. This is more a documentation of how I built the kite, particularly the vector unit. I'm trying to document this as detailed as possible so please comment on anything that is not clear or missing details from the build log.

Anyway, lets start with an introduction to the kite itself. Basic stats:

Aircraft
Wingspan: 1.54 m (60.6 inches)
Wing area: 6545 sq cm (1014.4 sq inches)
Weight: 159 g to 187 g depending on batteries (6.6 oz)
Wing loading: a ridiculous 285 g/sq m (0.9 oz/sq ft)

Hardware
Motor: Hobbyking 1404N-2290 9g 2290kv outrunner
Prop: GWS-DD-5043 (5 inches)
Battery: 750 mAH or 360 mAH 20C lipo
Servos: HXT500 5g micro servos
ESC: Hobbyking S Series 8-10A
RX: Hobbyking 2.4GHz 6 channel

Flight times are roughly 8-10 minutes with the 360 mAH battery or 20 minutes with the 750 mAH. You need to be very careful not to ever run out of batteries flying this thing because being a pure vector thrust machine you are basically using your prop to steer. Loss of power to the prop means total loss of control.

Oh, and sorry for the following bad video. Was holding the camera with my left hand while flying with my right
Scratchbuilt vector kite (1 min 48 sec)
slebetman is online now Find More Posts by slebetman
Last edited by slebetman; Feb 20, 2011 at 02:22 AM.
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 29, 2011, 07:26 PM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
OK, first lets start with the kite itself. The kite is a cheap RM6 (US $2) kite I got at the hardware store.

Before we even begin to modify the kite we need to find where the CG should be to make it fly like a plane (as opposed to flying like a kite). To find the CG we need to do a glide test. I knew my RC gear was going to be around 50 g to 70 g so I used an 88 g lead keel bulb from one of my RC sailboats as ballast for the glide test.

The CG for a perfect glide was found to be roughly 1/3 of the way or 33% down from the tip of the root chord. The Rogallo wing formed by the kite was very forgiving and can fly with the CG being anywhere from 25% to 33%. For powered flight I want the CG to be a little bit forward otherwise it would feel tail heavy.
slebetman is online now Find More Posts by slebetman
Reply With Quote
Old Jan 29, 2011, 07:29 PM
resU deretsigeR
PaulVi's Avatar
Dublin Ca
Joined Aug 2004
7,787 Posts
Nice all of my powered kites resulted in a very pitch sensitive un flyable kite.. I will be following along so i might be able to salvage some of what i have

More info on how it is attached to the kite and the basic power train layout will be nice
PaulVi is offline Find More Posts by PaulVi
Reply With Quote
Old Jan 29, 2011, 07:49 PM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
Once we know the position of the CG we can then position the RC gear. Two strips of velcro are glued on either side of the spine slightly forward from where I want the CG to be. This being a delta, a lot of the weight of the wing itself lie towards the tail. We need our hardware to balance that out. I used the location of where I taped the ballast during the glide test to figure out where to glue on the strips of velcro.

The strips were tacked on with double sided tape and then I ran superglue along the edges to strengthen the bond.

Parts of the kite that take a lot of punishment are reinforced with masking tape. I find masking tape to have the right balance of toughness and lightness. Using masking tape also allows you to remove old, worn out tape easily.

Finally, I extended the battens (the bits of framing at the side of the wings) using bamboo skewers. It flew OK without the extension but at high speeds the loose bit of cloth at the nose deformed and became a sort of pseudo canard. This caused the kite to fly at an increased AoA making it feel tail heavy (even though it really wasn't). Extending the battens improves high speed handling which is good if it suddenly becomes windy and you really need that extra bit of wind penetration.
slebetman is online now Find More Posts by slebetman
Reply With Quote
Old Jan 29, 2011, 07:55 PM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
Quote:
Originally Posted by PaulVi View Post
Nice all of my powered kites resulted in a very pitch sensitive un flyable kite.. I will be following along so i might be able to salvage some of what i have

More info on how it is attached to the kite and the basic power train layout will be nice
Yeah, when I initially added the radio gear at the intended CG the kite acted very tail heavy. I had to modify the vector unit to shift the CG forward (by shifting the motor forward) to get it flying stable.

Basically I started out with a rather tail heavy kite and trimmed it until it can fly straight without me touching the stick. To get the CG at 30-33% I basically had to install all the radio gear roughly 25% down from the tip of the nose.
slebetman is online now Find More Posts by slebetman
Reply With Quote
Old Jan 29, 2011, 08:16 PM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
OK, now onto the vector unit itself. First a general overview and introduction:
slebetman is online now Find More Posts by slebetman
Reply With Quote
Old Jan 29, 2011, 08:30 PM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
The whole vector unit is wood+superglue construction. Most of it is bits of leftover balsa I have lying around. The motor mounting block is harder wood, don't know what but it is used to make door frames. The rest are made from bamboo skewers.

My motor+prop was measured to produce 111 g static thrust. So to test the gimbal I suspended a 180 g pair of pliers from it and moved it around. Later I suspended a 490 g lead weight to see if I can upgrade to a larger motor.
slebetman is online now Find More Posts by slebetman
Reply With Quote
Old Jan 29, 2011, 08:47 PM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
Oh yeah, I'd be remiss if I didn't mention my inspiration. I originally stumbled across this idea from this thread:http://www.rcgroups.com/forums/showt...ht=vector+kite

Which led me to a bunch of youtube videos and then to other people building vector kites.
slebetman is online now Find More Posts by slebetman
Reply With Quote
Old Jan 29, 2011, 09:43 PM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
It is critical that the control linkage to the inside of the gimbal be as centered to the hinge axis as possible. Otherwise there will be a coupling between the movement of the outer frame of the gimbal and the inner frame. In this case the tilt linkage must be as vertically centered as possible.

Of course, because the servo arm moves in an arc it is not possible to fully center the linkage all the time but we can still minimize the distance. In my case the gimbal will tilt downwards a bit when panning left or right but it is manageable in flight.
slebetman is online now Find More Posts by slebetman
Reply With Quote
Old Jan 29, 2011, 10:59 PM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
Key load bearing joints are reinforced with cotton thread soaked with superglue. Funny how I found out which joints needed reinforcement: they're the ones which broke during test flights
slebetman is online now Find More Posts by slebetman
Reply With Quote
Old Jan 30, 2011, 12:21 AM
Storm Runner guy
Slider2732's Avatar
USA, OK, Muskogee
Joined Nov 2008
3,581 Posts
Lots of tips and a great write up...i'll be referencing this for some projects in the future
The kites look so graceful in the air and are so smooth flying. I'm sure these gimbals will find their way onto traditional flying wing foamies too.
Slider2732 is offline Find More Posts by Slider2732
Reply With Quote
Old Jan 30, 2011, 01:51 AM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
Quote:
Originally Posted by Slider2732 View Post
Lots of tips and a great write up...i'll be referencing this for some projects in the future
The kites look so graceful in the air and are so smooth flying. I'm sure these gimbals will find their way onto traditional flying wing foamies too.
Actually, being a foamy kind of guy, I originally planned to make a rogallo wing out of depron to test this thing. That was before I discovered that my hardware store sell cheap kites.
slebetman is online now Find More Posts by slebetman
Reply With Quote
Old Jan 30, 2011, 01:59 AM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,352 Posts
The control rods were originally just plain steel wire which is what I use for all my other RC stuff. But I found that they would be bent out of shape after each flight. So I needed a stiffer rod.

Not having any spare CF around I turned to bamboo skewers. The skewers are split in half and I used a triangle file to cut a groove in each half. They are then clamped around the steel wire and bonded with a touch of superglue.
slebetman is online now Find More Posts by slebetman
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Airfoil Selection for Slow Flier? ForeverFlying Modeling Science 31 Feb 06, 2011 05:05 PM
Discussion Slow flying RC KITE! JIMFRISKY Flying Wings 20 Jan 04, 2011 06:11 PM
Gallery 10 gram ULTRA slow flier w/Plantraco powah. arclite5 Scratchbuilt Indoor and Micro Models 13 Jul 11, 2006 03:52 PM