1.7m yellow rokkaku - 20 sq ft

This scaled-down rokkaku is designed for KAP, fitting in between the 9ft Levitation Delta and the 28 sq ft 2.0m white rokkaku.

Like the 2.0m kite the size ratio is 5:4:3. This means 5 units high, 4 units wide and 3 units between the cross spars. The top and bottom triangles are 1 unit high and the bridle points are 1 unit out from the spine. For this kite 1 unit equals 34cm making it 170cm high, 136cm wide and 102cm between the spars.

Woven cloth has least stretch along the WARP fibres (down the length of the roll). The WEFT fibres (across the roll) may not be as straight or as strong, and the BIAS (at an angle to the fibres) gives the most stretch. Cut out your panels so that the WARP fibres are parallel to the outer edges of the kite. This is the reason 5 or 6 panels are used for the rokkaku.

Ripstop nylon from Emma Kites is 155cm wide which is wide enough to cut out the rectangular panel (forming main body) in a single piece with the warp threads aligned correctly. The top and bottom of the kite still need to be made from 4 right angled triangles.

I bought a 5m pre cut length for US$21 (free postage) and used less than half.  I did notice that the WEFT fibres run in quite a pronounced curve across the roll, maybe that is why it was so cheap. However the kite still flies perfectly.

Spars are 82.6cm Skyshark Camo P4X tubes from Kites and fun things. US$3.50 each with US$42 postage. To spread the freight cost I bought 20 of them with carbon fibre rod ferrules (3.75" x 0.24") and vinyl end caps (0.281"). That will be enough for another 3 kites or lots of breakages.

I did the seams a little differently this time for a neater finish. Virginia tells me the correct term is flat fell seam. Two panels are sewn together front to front along the marked sewing line (20mm in from the edge) then the panels are opened out and the 20mm seam folded over to the left or right. About 12mm of the underneath seam is trimmed off, then the top seam edge is folded over and under the trimmed edge then sewn down close to the folded edge. This gives a neat finish with no raw edges.
For the first time ever I also used the correct thread colour top and bottom for the entire kite.

I'll do some instructional videos on the sewing details soon. Stay tuned.

The patches, webbing pockets and velcro loops are all the same as the 2m white rokkaku as are the folded hem edge and bridle.

Here is an A4 size plan for the 1.7m kite. Feel free to download it for your own use.

Timelaspe of cutting out and sewing the 1.7m rokkaku. 4hrs in 80seconds

Here's the first flight in Bft 2

Here's a test flight in Bft 4+

Rokkaku pushed to the limit

Continuing on with rokkaku testing, here's a video in Bft 5 or up to 20kn. That's beyond the recommended wind range for this kite but I just had to see how it would behave.

Line pull was averaging 20lb and peaked at 25lb, which is unpleasant.

The Skyshark P4x spars flexed alarmingly but survived.

Rokkaku bridle and bow adjustments

Here are two videos showing the tuning adjustments used on a rokkaku kite.

If either of these adjustments are a long way off the kite will either pull like a donkey and not fly high, or swing around wildly from side to side, or fly forward then drop back repeatedly.

But within a small range of adjustment you can choose how high it flies or how hard it pulls.

Angle of attack or bridle height adjustment.

Spar bow adjustment

Making a 2m Rokkaku - bow tension and flight

Part 4 of 4

Spar bow lines
A rokkaku is a flat kite which means it has no inherent stability. Some bend in the spars is required. Adjustable tensioning lines bend the spars like an archer's bow.

In the sewing instructions I mentioned how to create an end loop in the pockets for the bow lines. This photo shows how the end loop works.

The lines are about 2.2m long, tied at one pocket, looped through the other pocket then back to a sliding clip.






I made the sliding clip from UPVC plastic which can be heated and bent into shape. A 30mm x 15mm piece is drilled with two holes, rounded off and heat bent with a slight curve.

The clip slides along the line and holds the bow under tension.






The amount of bow can be adjusted to change the flight characteristics of the kite.
More bow gives less pull, more stability and a lower line angle, better for stronger winds.
Less bow gives more pull and a higher line angle but will reduce stability. If the kite is wiggling side to side you need more bow.

Some folks say you must have more bow in the bottom spar than the top, others say they can be the same. Mine seems to fly well either way.

I tend to set up with 6 to 8" of bow in the bottom and a little less in the top.

Angle of attack
The final small loop in the bridle is used to adjust the flight angle. The prussic (prusik) hitch, or double larkshead hitch holds it in place under tension but can be loosened and moved under no tension.

With the loop at the centre point of the bridle the kite will pull like crazy and sit on the ground. Moving the loop up a long way, say 12", will make the kite go up a bit but tip over towards you.

This ideal bridle position is somewhere between these two extremes. Try placing the loop about 8" above centre and see how it flies.

If the kite flies but with not much pull and is luffing or tipping over at the top move it a bit lower.

If the kite is pulling hard and not rising far move the loop a little higher.

When it is in the correct spot the kite will climb up high and sit there with moderate pull on the line. You can now dictate exactly how much line pull you have by moving the loop up or down in small amounts. If you need more pull for lifting an SLR move it down a bit, and if you want less pull for easier flying move it up a bit.

The rest is up to you, go fly the kite and have fun.
I'll make a video showing different bridle positions and the resulting flight characteristics soon, maybe different spar bowing too.

Making a 2m Rokkaku - Spars and bridle

Part 3 of 4

Carbon tube spars
Wrapped carbon tubes seem to be the spar of choice for many Rokkaku flyers, they are certainly the lightest and quite stiff but a little expensive locally.

Kites and fun things have a great range of SkyShark tubes way cheaper than I can find in Australia. The P4X camo are US$3.50 each, an absolute bargain even with $42 shipping. I ordered 12 spars plus internal solid carbon ferrules and vinyl caps to fit.

The P4X spars are 0.297"OD, 0.244"ID, 32.5" length, or in modern units 7.5mm OD, 6.2mm ID, 82.6cm length. It's pretty much impossible to find full length spars so joining is essential. Most of the wrapped carbon tubes are made as arrow shafts, hence the standard 32.5" length.

It's best to avoid joins where spar and spine cross and at bridle attachment points so some nutting out is required to determine what lengths to cut.

The cross spars are roughly 160cm requiring a 3 piece design. 2 x 3/4 lengths with a 1/2 length in the middle. That left 4 x 1/4 cutoffs.

The spine is 200cm requiring a 4 piece design. To reuse some of the cutoffs  I used 2 x (1+1/4) lengths. The 1+1/4 being permanently glued with an internal ferrule so it's actually a 2 piece spine.

Ferrules are glued in using epoxy.

The next job is to carefully fit them to the kite, trimming the ends evenly until they are the right length. Take it slowly, you don't want to cut them too short. Then you can pop the vinyl caps on to cover the ragged ends.

Bridle
The final task is to make up the bridle. It consists of top and bottom Vs (black in the photo) joined by another V (red) with a short loop at it's apex (green).

For the top and bottom Vs take 3.6m of 200lb dacron line (making a 1.8m V), pass the ends through the kite bridle points and tie to the spars using a larks head hitch. Carefully find the centre of the V and tie a small loop. The line for the third V is about 2m long (making a 1m V) and is tied between the top and bottom bridle loops using a bowline knot.

The final short loop is made from about 30cm of line and attached by a prussic hitch to allow angle of flight adjustments. This hitch grips under tension but can be moved under no tension.

Initial placement should be about 8" higher than the middle. You might need to slide it higher or lower to tune the flight angle.

Here is my first flight of this wonderful kite.

and another compared to the Skydogs Pirate Rok

Next post will cover spar bow lines and kite angle of attack.

Making a 2m Rokkaku - Sewing

Part 2 of 4
Ripstop is very light and slippery which makes accurate sewing a little tricky. I pinned the panels together to sew the seams. Other kite makers use tape, glue or melting tools but pins worked for me.

Common sewing stitches used are straight and zigzag. Straight stitch has less stretch and is good for seams.  Adjust the stitch length to about 8 stitches per inch. It's essential to practice first on scrap cloth to ensure the tension is correct. Consult your manual or ask an expert to adjust the tension. I used zigzag on the corner patches because that seems to be what the experts do.

Panel seams

Pin the panels together face to face and sew along the 15mm seam line pulling the pins out before you run over them. Open out the panels, fold the seam over, and sew it down flat. The raw edges will be exposed but coated ripstop won't fray. For a really professional finish you can fold the top edge under before sewing down. Might try that next time.

Corner reinforcing patches

Corner reinforcing patches are cut like pieces of pie from a 150mm diameter circle of stiffer cloth. Once the panels are sewn together position the circle over the top corner, mark the angle and cut out the wedge. For the side corners you only need to fold the remaining part of the circle in half and cut along the fold.

Once all the panels are sewn together you can sew on the corner patches but first fold and make a crease all the way around the kite along the hem line. Now position the corner patches a few mm in from the hem line with pins and just sew around the curved edge.

Hem

Now for my favourite bit, the double folded hem. I like this bit because it's easier than seams and it finishes off the kite, apart from a few more patches. Fold the fabric edge over to the crease then fold again to form a 10mm hem. Sew down using straight stitch all the way around the kite. You can fold as you go.

Pockets

Side and top spar pockets are made from 100mm lengths of 25mm wide webbing with 35mm folded over folded over to form the pocket. When sewing down the side pockets you can form an end loop for the bridle lines by sewing across 10mm back from the fold.

The bottom spine pocket needs to be adjustable to tension the spine. Velcro and webbing are used to form a pocket and adjustable flap.

Bridle holes and spar crossing points and ties

Four 40mm square patches are sewn on 400mm out from the centre of the kite and in line with the upper and lower spars, and another in the centre of the spine. Beware, the centre of the kite is on the folded edge rather than the middle of the centre seam. 

To make holes for the bridle to pass through I melted holes in the patch using a heated piece of coat hanger wire. Other kite makers fit brass grommets as well.

At the spine and spar crossing points I used a 80mm x 40mm patch. Onto the patch goes an 80mm piece of webbing which has velcro pieces sewn on to hold the cross spar. A 15mm stitching gap is left in the middle of the webbing for the spine to slide through. That way the spine always sits between the spar and the cloth.

Velcro is sewn on to the centre spine patch to hold the spine.

Lots more close-up photos here

Here is a video of the process which will help make sense of these instructions.

Next post will cover spars and bridle

Making a 2m Rokkaku - Preparation

Part 1 of 4 
I have made kites all my life, but nothing as big or serious as this one, and have a fair bit of sewing experience. Between high school and uni I spent some time as a sailmaker's assistant and made my own sailboard sails. Wife Virginia encouraged me to use her precious Pfaff Tiptronic 2030 so I was almost set to go.

Great advice given by expert sewers is "new project, new needle". Respected kite maker  Gary Engvall recommends that a size 90 universal point needle is right for ripstop. So I bought a packet of size 90 universal points and 2 rolls of Gutermann polyester thread.

A Rokkaku kite is very simple being basically a flat hexagon with patches and pockets added and there are plenty of plans and How-to websites available.

I closely examined Rokkaku photos on Flickr. especially those by Cris Benton, Blue Kite Team, KAPPIX and Jones Airfoils and read through Gary Engvall's instructions many times.

I decided on a 5:4:3 size ratio and 2m high design. This means that the height is 200cm, width 160cm and main body 120cm high. This is a good size for a wide wind range similar to the Skydogs and Premier Rokkaku kites. It should have roughly twice the line pull of a ITW Levitation Delta making it perfect for lifting an SLR in Bft 3 and 4 and lighter rigs in almost any wind.

Now for sourcing the materials. Ripstop nylon varies greatly. Don't go to a normal material shop and buy their cheap ripstop, it's heavy, stretchy and only good for shower curtains, kite bags and tails.
For kites you need the stiff crackly stuff used for spinnakers. The most common weight seems to be 3/4oz. I used Emma Kites $6.00 ripstop. Although it's very light weight it worked really well. Might try ITW, Kitebuilder or a local sailmaker's spinnaker cloth next time.

You also need some stiffer reinforcing cloth for corner patches and other stress points. I had some cordura for my kite but dacron sailcloth is more often used. 1" wide webbing is also needed for corner pockets and spar loops.

Here is an A4 sized gif of my kite plan. Feel free to download and print it. Red seam allowances are not to scale.

It's important to cut out the panels with the long edges aligned along the warp or down the length of the piece of cloth. That way the finished kite will hold its shape better with less ugly stretch wrinkles. The warp has less stretch than the weft.

I made a template for the triangle panel which made marking out
much quicker.

Mark out the finished size of the panels on your ripstop in clear lines (to sew along later) then add the seam and hem allowances (for cutting out)

Next post will discuss sewing together the panels and adding reinforcing patches

Line-pull measurements

The amount of pull on the line dictates which KAP rig can be used. I have started recording line-pull using an electronic luggage scale ($9 on ebay) to help with kite selection.

I have found that line-pull of about 3 times the rig weight is enough to safely lift the rig. So I need 7lb pull to lift my 1.1kg SLR rig. (Apologies for the mixed units, must start measuring pull in kg!)

Here is a clever interactive lift/pull calculator from Kaper e-zine. Plug in rig weights and see line pull and angles.

Of course line angle also matters. Deltas can fly almost directly overhead. At times the delta and rig can be in perfect balance leaving next to no tension on the line in your hand and zero movement of the rig. Perfect for sharp KAP shots. It's a magical moment, hard to believe it's possible.

My intention is to build up data for each kite in a range of wind strengths.
It's early days but it seems with the 7ft Rokkaku line-pull in pounds is pretty close to wind strength in knots. For example I would expect line-pull of 7lb in a 7kn breeze.

Here are two video compilations of kites compared in Bft 4 and Bft 2.
I'll do Bft 3 and Bft 5 when the conditions permit. I have tried Bft 1-2 but the Rok was the only kite capable of staying up.

Three kites compared in Bft 2

Four kites compared in Bft 4

Eventually I'll put together videos and publish a line-pull table for each kite separately in the full range of wind strengths.

Beaufort Wind Scale
Bft 1     1-2kn          Calm - Not enough to fly. Go diving
Bft 2     3-6kn          Light breeze - Rok will fly, others maybe.
Bft 3     7-10kn        Nice breeze - All kites will fly. Need to match kite to rig.
Bft 4     11-15kn      Decent breeze - All kites will lift rigs easily. Upper range for the Rok.
Bft 5     16-20kn      Strong wind - Too much for the Rok and Levi
Bft 6     21-26kn      Howling - Only the PFK will survive.

Pirate Rokkaku

A new kite, very exciting.

Size comparison: PFK Nighthawk        9ft Levitation Delta                      7ft Pirate Rok

The rok almost didn't get delivered due to a couple of crucial typos in the shipping address. Luckily I knew in advance and retrieved it from the post office before it was returned to the sender.

This is a 7ft rokkaku made by SkyDog Kites and sold by Picture Pretty Kites. Cost US$99 with $40 delivery. I would have preferred a single colour kite but there wasn't much choice for this size and price.

First flight of the Pirate Rok in about 6kn

It is very well made from good quality ripstop and has fibreglass spars. More expensive roks have carbon fibre spars and so are a little lighter and stiffer. Fibreglass spars may extend the upper wind range being more flexible.

I'm hoping this kite will have more lifting power than my Levitation and PFK deltas and will lift the D80 in lighter winds.

First flight was in perfect light breeze and it behaved beautifully with very little movement. Line pull was 2 to 4lb and lifted the 300g Canon S100 manual rig with ease.

Tensioning of the upper and lower spars tunes the flight characteristics. In the video I tried 10" of curve in the lower and 8" in the upper, which is a good starting point. Flattening out the curves produced more side to side swaying.

Nikon D80 SLR manual rig

I recently upgraded to a Nikon D7000 for underwater photography so my original SLR, a Nikon D80, doesn't get much use these days. To reward the D80 for reliable long service and paying for itself many times over I thought it might like to go flying.

It's not the ideal KAP camera being quite heavy (672g body + 202g 18-55mm lens = 874g all up)
and it doesn't have an intervalometer but that didn't stop me. James Gentles makes a lovely little device called GentLED-AUTO which is an IR remote intervalometer weighing just 20g. I just happened to have one sitting around so it was time to give SLR KAP a try.

First step was to make a basic manual rig just to see if my kites could lift it.
I bent up some aluminium to make a rig similar to the vertical style Aurico autoKAP rig for the Canon S100. But this design, a single vertical support with an L bracket to mount the camera, was way too flexible for the heavier SLR. The spring like flexing would have had the camera bouncing up and down continuously.

Nikon D80 manual rig - 1090g

So I had to revert to the tried and tested double U style. This allows a light and stiff rig to be built using the minimum of material, but it means I needed to balance the camera in the bottom tray carefully following James Gentles guide, which I find much trickier than building the vertical style rig.

The bottom U tray needs to be wide enough, front to back, to accommodate the camera mounting bolt and the pivot holes on each side which are at the centre of gravity for the camera. With this camera/lens combo the centre of gravity is 24mm forward of the camera mount hole. The bottom U needed to be 40mm wide. The top U only needed to be 30mm wide to be stiff enough.




Amazingly the wind was perfect for a test fly on the day I made this rig. Sunny with a smooth onshore 12kn and the Levitation Delta had no problem lifting it all as shown in this video.

I was really pleased with the image quality compared to the Canon S100 partly because the heavier rig isn't blown around by the wind as much.

I have begun to realise that lighter rigs suffer from blow back resulting in angled horizons or more/less tilt than expected. I'll talk more about blow back soon.

Here are KAP shots using the D80

First you need a kite.

To lift a camera you need a big kite with lots of pull. It also needs to be a steady flier and there are a few designs renowned for their KAP-ability.

PFK Nighthawk
The Paul's Fishing Kite (PFK) Nighthawk delta is designed to fly in winds as strong as 30kn. Most other kites would be looping and crashing by then. It has large trailing edge flaps, strong flexible fibreglass spars and a hardwood spreader. The KAP community has adopted the PFK as the strong wind specialist, but it will also lift lighter rigs in normal wind strengths.
This is my favourite kite, it just wants to fly and keep on flying no matter how strong. Tail usually not required but may calm it down a bit in strong winds and reduce overflying.

Lifting range
480g RC rig in 12kn - 30kn+
270g GoPro rig in 6kn+
NZ$140 from Paul's Fishing Kites - New Zealand

ITW 9ft Levitation Delta
For lighter winds 5kn -17kn, this big delta from In-to-the-Wind is my choice and a favourite of many KAPers world wide. It has more pull than the PFK but also starts to fly to the side and do power loops in wind speeds above it's range.
Flies at a very high angle and even over-flies in light puffy wind and hot days. Adding a tail reduces overflying and gives steadier flight. I use a 3m long tube tail.

Lifting range
480g RC rig in 8kn - 17kn
270g GoPro rig in 5kn+
US$75 from Into the Wind - Boulder Colarado




PL Pilot 2m2

This 2.0 square metre parafoil is made in New Zealand by Peter Lynn Kites. Peter Lynn is famous for making some of the world's largest kites.
Parafoils have no spars and pack up into a small stuff bag. They have strong pull but fly at a lower line angle like 50º
Flies well without a tail but everyone else says they use one. May calm down side to side swaying.

Lifting range
480g RC rig in 10kn+
270g GoPro rig in 6kn+
NZ$96 from Peter Lynn Kites - New Zealand




Cody Box Kite
This was the first kite I bought for KAP and it was not all that suitable. Above about 16kn it flies out to one side and power loops. It has a narrower wind range than the above kites and take more assembly time but does have good pull. KAP range 8kn - 15kn
However it is an interesting kite in the sky and attracts attention. It flies well enough within its wind range.

A$79 from Kite Power - Geelong



UPDATES
18th Jan 2013: New kite added to the quiver.
Skydog 7ft Pirate Rokkaku

Feb 2013: Made a 2m white rokkaku

May 2013: Made a 1.7m yellow rokkaku

What is KAP?

Kite Aerial Photography

This what you get when you add a camera to a kite, maybe some radio controls or electronics and lots of shed tinkering time.

Images captured by kite give a rarely seen perspective, on a more intimate or human scale than traditional aircraft aerials.

There is a very active world wide online community of KAPers and some seriously clever inventors producing electronics, rig and camera control scripts and mechanical bits for KAP rigs.

Kites
Big stable kites are needed to lift the camera and rig. KAPers usually have a range of kites to cover different wind speeds and camera rig weights. More about that later.

Cameras
The lighter the better obviously. GoPro, Canon compacts and even small SLRs are popular. Mirrorless large sensor cameras are starting to feature too.

Canon compacts can also be enhanced via CHDK (Canon hackers development kit) and SDM (Stereo Data Makers) firmware changes. I'll write more about these later but basically some very clever programmers have written firmware enhancements which add functions such as intervalometers, RAW, HDR and bracketing.



KAP rigs

There are many different styles of camera rigs for kite aerial photography. Here are a few of the main types.

RC KAP - using radio control to operate pan and tilt and maybe shutter release.

Auto KAP - using pre-programmed electronics to replace the radio controls. AuRiCo (automatic rig control) is what I use. The rig performs a repeating sequence of tilts, pans and shutter releases by itself.

Manual KAP - where you set the camera orientation and shooting interval before launching. The kite needs to be brought down to make any camera changes.