Kite-sailer.com 47751 Michigan Ave., Laguna Heights, Texas, Tel.: 956-943-5150

 Construction of kite control bar for kite-sailer

 

In kite surfing / kite boarding the steering bar allowes the surfer to control the motion / flight of the kite and connects the kite surfer to the kite. The bar is moved in an left/up and right / down motion ( or some call it boxing ) or opposite by the surfer to steer the kite left or right .
The inner lines ( break lines / flight lines / power lines)  are attached to the harness via chicken loop and by pushing the bar away from the surfer he can depower the kite. This setup would be tiering over time on our kite-sailer.

As such we need to change this setup to a more comfortable moition. Our kite control bar will direct the forces of the inner lines ( the power lines / break lines / flight lines)   to the hull via a 1:2 reduction with quick release. The outer lines ( steering lines / flying lines)  will be 90 degree redirected to the controller handle bar which has a left-forward / right-aft ( or opposite) motion to steer the kite actively from a sitting position on the kite-sailer.

Since the kite-sailer kite control bar will be used on a boat and its intention is to use it for extended periods of time, in a saltwater environment, all components used are marine grade stainless steel and can handle the loads of modern traction kites. Safe working load was set at excess of 500lb .
kit

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Kite control bar as used in kite boarding with complete safety features

The "Wind Window" and forces of the kite :


align="left"> I want to add this short explanation for all who are coming from boating / sailing to this site and are not familiar with the expression "wind window" and the forces behind it. Kite surfer are well familiar with the forces and master them to their benefit.

The "wind window" as seen on the right side is if you are standing with your back into the wind ( upwind ) and face away from the wind ( downwind) . The 3-dimensional area in front of you and within the reach of your kite - kind of limited by the length of the kite lines which are normally about 20 meter / 64 feet. Each section of the "wind window" has a different force on the kite , different acceleration of the kite and diffrent pull / lift characteristics. The upwind section of the "wind-window" or for sailor the circle of "Beam reach " has the lowest amount of force / lift / pull and the slowest motion of the kite. As you steer your kite into the center of the "wind window" or downwind / run the forces will increase drastically as well as the speed of the kite as it is moving through your wind window. To balance the motion and the forces of the kite through the "wind window" requires an open area in front of your kite to hull attachment point as well as a free space for the kite controller to maneuver the kite control lines, besides attention and quick reaction so you don't ditch your kite in the water.

As you actively steer your kite through the wind window you can make use of the diffrence between pulling forces and lifting forces to balance your hull with the motion of your kite.




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The power window and its forces on teh kite / kite boat Power relation of the wind window for kite boating

Connecting the kite to the hull


Most modern traction kites are 4 line kites - this results into 2 power lines at the kite and 2 steering lines. The power lines are more to the center / forward of the kite while the steering lines are aft / on the trailing edge of the kite. The power lines can be connected at the hull into one line - while the 2 steering lines need to stay independent from each other for control. Power lines need to be easy adjusted for setting the kite canopy angle for your convenience and in case of a emergency to be depowered - ( released) which results in a airfoil shape with 0 lift. You can accomplish this with a pulley on a line leading back to a cam cleat at the same location where you will steer the kite. Steering lines need to be able to adjust ( via a bar ) or any other means to pull or release. This will steer your kite and fly him through the power window in a controlled manner - The image on the right is from a Airrush one 4 line kite with only one bladder and steering lines well apart from the power lines - I believe for us a bit slower moving kite-boater this set up is better than the older C-shape kites where power lines and steering line attachemnt points are within 8 " I hope I could help you understand the basic setup for kite boating - if you have any question feel free to ask michael@4wings.com

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Traction kite line attachemnt points

May -

A new set of pulleys came in and they fit great - low weight / swivel head and ball bearings in our working load range -
This is the core of a long discussion we had when we tried to find the best suitable lines for the kite-sailer control bar.

For kite control lines you need lines with low diameter ( to hold drag low ) , low weight  and high "Tensile Strength"
On the control bar you will need high tensile strength but can be more flexible on the diameter.

Tensile strength is the load at which a new rope / line , tested under laboratory conditions, can be expected to break.
Safe working load of a rope / line is determined by dividing the minimum tensile strength by the safety factor .
Safety factors range from 5 to 12 for non critical uses. The safe working load is a guideline for rope/line in good condition.
With  age and use, the safe working load  of your  kite rope / line will get lower.
So lets get out of the theory and start to look at the Kite lines and control bar lines -

Currently common kite lines are "Dyneema SK75-12" or "Dyneema sk90"

Alternatively you can use :
"Spectra"which is used by some kite manufacturer   and  "Vectran"

"Spectra" and "Dyneema" are the same material Ultra-high-molecular-weight polyethylene , just different trade names and  the manufacturing process is different.

"Vectrans" are some form of liquid crystal polymer that have similar strength, but higher modulus and less creep. for more detail please see :
http://www.performancedesigns.com/hma.asp

If you are in the EU / Asia you might look into Liros lines : http://www.liros.com/start.aspx

Kevlar ( aramid) fibers are still as strong as spectra but higher in density.

You'll frequently see fibers compared with strength / weight as the ultimate value.
But this is not necessarily stronger, but stronger per unit weight as such you need to make the numbers till the end ....

Diameter and tensile strength of Dyneema SK75-12
Avg. Tensile strength for 1.8 mm - 920 lbs
Avg. Tensile strength for 2mm - 1000 lbs
Avg. Tensile strength for 3mm - 1920 lbs


For most user the kite lines provided by the kite manufacturer will be your best choice - as one of the main problem is to find a supplier who has the quality you need , the diameter you desire - in the colors you want at a price you can afford ...lol in a line diameter of 3 mm and up you will find a small amount of supplier - unfortunately that diameter is a bit to high - you will try to be in the 1.5 mm to 1.8mm ( approximately 1/16" )  diameter range of lines for your flying lines -
For your kite control bar the lines can be in the 3mm ( approx. 1/8" )  and 6 mm ( approx. 1/4") range as these lines are not all too much subject to  drag but quite some chaffing.
All the lines  should be eye spliced to hold the maximum breaking load throughout the entire line which is possible on the 6mm up lines but hard on anything below this diameter.
The only supplier we found who actually carried more than one color and diameter was :
http://www.milwaukeerigging.com/index.htm
But we hope that over time we will have more suppliers for you

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Kite control bar for kite powered boat like our kite-sailer KS32F under first land test side view

 

 

Kite control bar for kite boating , kite sailer

 

Kite control bar for kite sailer , kite boating, kite-powered water craft

April -

 

We get most of the components ready to go into the first test trial - test were performed at our dock with a 3.5 meter trainer kite to get the basic feel for the bar - even if the functions performed well - the pulleys were too  big and  the lines too heavy - guess I have to get the sailor out of me and rethink thin ...how thin ..?

 

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Kite-sailer control bar on test 1

March -

Kite-sailer kite control bar extended

 

 

 

 

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Kite control bar for kite powered boats

March -

Just out of the welding shop -

The basic components are a SS square bar with welded support for the cam cleat on top  which will serve as de-power system / de-power adjuster.

The fork swiveling snap shackle serves as emergency release and connects the handle bar to a lifting eye which is through-bolted the boat hull and secured with a 5/8 SS bolt

A pivot point for the handle bar is welded to the outer piston sleeve which will connect the outer ( steering ) lines.

 

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2012 kite-sailer.com

 Kite controller during construction , kite bar for kite powered crafts





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