Kites
Gather notes and questions about our lifters here -- types, tuning, pros and cons
the ROKKER ; a new vented Rokkaku with good features of Roller
August 2020
in Kites
For KAP the search of stability and good confidence is pushing me to trials for vented ROKKAKU (after many nights dreaming about Nicolas Chorier's kite for KAP...)
a new solution that is much easier in sewing and assembly for this kind of kites is shown in : http://www.ipernity.com/doc/1148945/album/1280772
the ROKKER shows very good performances.. I'm very happy of this kind of kite
it offers a wider range of wind speed and a clear change of angle of incidence when the wind speed is increasing; the good performances of Roller, Dopero and several other kites have a positive influence on the lower sail (yellow in the proto kite)
SMAC from Italy
a new solution that is much easier in sewing and assembly for this kind of kites is shown in : http://www.ipernity.com/doc/1148945/album/1280772
the ROKKER shows very good performances.. I'm very happy of this kind of kite
it offers a wider range of wind speed and a clear change of angle of incidence when the wind speed is increasing; the good performances of Roller, Dopero and several other kites have a positive influence on the lower sail (yellow in the proto kite)
SMAC from Italy
Comments
ROKKER after two kites made and tested in different conditions looks to be quite interesting for KAP; main positive result is the wide wind speed range; the two proto ROKKERs are 1.65 m wide and near 2 m height
I have lifted ROKKER with 3 km/hour (0.83 m/s 1.9 mph) and it is quite effective on "pumping"; I had ROKKER in the sky together with only few PHANTOM DELTA UL...
I had two main occasions of flying in strong wind 50 to 60 km/hour (14 - 17 m/s 31- 37 mph), also with side sudden gusts... conditions where you would like to have in hands a PFK NIGHT HAWK... the ROKKER pulls strong but not as hard as a common ROK; the shape of ROKKER is not deformed as ROKs , it continues to fly well high and gives confidence to keep in safety a KAP RIG....
the ROKKER sounds to be a good chance in case that during KAP the wind conditions are getting worse in a short time
SMAC from Italy!
ROKKER image
So it can fly in winds from 3 to 60 km/hr and lift a rig? That sounds like the holy grail of KAP kites.
One kite for all conditions, say Beaufort force 1 to 6, sounds too good to be true!
It would be great to see some video of it performing in both light and strong winds.
Is it possible that a scaled down Rokker could out-perform the famous PFK in heavy winds?
Thanks for sharing your creation. I look forward to reading more as you get more experience flying it.
Hi montagdude and Ningaloo,
I was expecting a good result from ROKKER but I have been widely surprised myself.... quite over imagined (anyway I'm coming from other 4 trials on vented ROKs...)
sorry I do not have a video and in difficult conditions my attention is all to kite, not to social....
the sense of my words about ROKKER is quite different
1. in minimal wind speed ; it is already a beautiful possibility to have the kite in the sky; you cannot add any KAP RIG but in several conditions at ground level you have wind conditions poor and when you get higher the kite is reaching better conditions and maybe at 40 - 50 m height you can add the KAP RIG and make a good session
2. at very strong wind conditions; the ROKKER is NOT an alternative to PFK, no but in case that during fly or KAP the wind gets much worse you are at upper safety limits but you can get down your KAP RIG and kite still gives the feeling of stable flight at a good angle (doesn'g go down on trees, doesn't break a piece of frame...)
SMAC from Italy
I'm thinking I will try making a smallish one of these out of wood dowels and a plastic drop cloth. Not for KAP, but just for fun and experimenting. Do you have any design tips that you are willing to share after making a few prototypes?
Hi montagdude,
dimensions are: both horizontal spars 1.65 m
height : total 1.96 (0.42 + 1.12 + 0.42) m
upper and lower sail connected only in the middle and at both external ends
upper sail low edge : stiffened - reinforced - I used mylar
all edges are reinforced , all contour should be at low elastic deformation
bridle : classic 4 points ROKKAKU style
in my protos frame is for horizontal spars P4X CAMO SKYSHARK 2 + 2 ; for spine carbon tube 8 mm
SMAC from Italy
Thank you! I'll try to post some pictures if I build one.
Really interesting "all purpose" kite, Smac.
And, regarding your Ipernity page, nicely sewed.
What king of fabric (spi) to you use ?
Emmanuel
Thanks Emmanuel - photocerfvolant,
I use spi from a sailmaker... I cannot say exactly what source - specs...
always spi 30-40 grams/squaremeter - polyesther high tech specs
sometimes is Contender Dynacote or Maxicote but I cannot say in detail
SMAC from Italy
Thank you Sandro for the answer.
It's a relatively light spi fabric. Maybe why it fly since a little breeze.
Hi,
about weight... overall weight of kite complete ROKKER prototype1 blue-yellowfluo 330 grams ; ROKKER prototype 2 purple-yellow 390 grams... but proto 2 has overall performances better than proto 1 and weight is important OK but wait a moment....
SMAC from Italy
;o))))
The ROKKER family has today 4 kites, two equal size, a small guy just for fun and a ROKKERstorm based on the comment made by Kevin - Ningaloo october 2020
it was fully OUT from my programs and intentions but it was worth a proto kite and a test to see how crazy was the chance...
ROKKERstorm is reduced in size 1.3 x 1.6 meters
yesterday I had some good wind for a preliminary test; until my windmeter was functioning I have seen at ground level 38 km/h, than later the battery went down, I guess that wind was between 40 and gusts about 50 km/h; the kite flies well with some few tendency to acrobatics easy to compensate with just 0.5 - 1.0 m of line loosen and sudden clean recovery (later with a trial with increased bowing the "acrobatics" disappeared... in the test area the wind from NORTH arrives "dirty" passing over the town and some sudden side wind from EAST was disturbing...)
I added some video and several pictures in IPERNITY : http://www.ipernity.com/doc/1148945/album/1280772/@/page:3:9
Further test are needed in much severe conditions but results seem promising
the pull is keeping comfortable ... I had a KAP session, not in the the max speed conditions (KAP around 3pm, max speed was later about 4 pm - fly time from 2.30 to 5.0 pm)
SMAC from Italy
Nice! In your opinion, would one of these small ones be able to lift a rig? It looked pretty stable for how windy it was, especially considering it doesn't have a tail or drogue.
Hi montagdude,
yesterday with wind 15 to 20 km/h I was doing KAP with this ROKKERstorm and a RIG 370 grams (RICOH GR autokap with minipicavet)
pictures on my facebook https://www.facebook.com/sandro.macchi.5/
on a large range of wind is well suitable for KAP the standard ROKKER 1.65 x 2 m
SMAC from Italy
Hey Sandro.
I replied to your email before watching the videos on ipernity. The RokkerStorm performs well. The kites look beautifully crafted too.
The PFK has a rival!!
Hi Smac,
I'm new to this forum but I have been doing KAP and building kites since the eighties. Last year I made a slot above the lower spreader in a 2,5 meter Rokkaku kite that I built 30 years ago. I got the idea after reading about slotted aircraft wings. Slots in kites can improve aerodynamic performance. Triple Roloplans could be regarded as slotted wings. My slotted or vented Rok has a better flying angle in high winds. I suspect a slot above the upper spreader would increase performance even further.
Regards,
Cor
Hi Smac,
I have some pictures of my slotted Rok in 5-6 Bft. It clearly performs better in high wind after I added the slot above the lower spreader. This kite has some scars after 30 years of intensive use. I added a sleeve for the lower spreader.
Hi Cor,
always nice to see trials on vented ROKs
I'm now building a new ROKKERstorm for future trials
in low - near zero wind the standard ROKKER is also in a video just added in IPERNITY
http://www.ipernity.com/doc/1148945/50607784
ROKKER 3 http://www.ipernity.com/doc/1148945/50607782
SMAC from Italy
ROKKER storm (blue-white-red 1.3 x 1.6 m) and ROKKER storm 2 (grey 1.5 x 1.8 m) prototypes are now flying...
in IPERNITY - SMAC there are also some videos
http://www.ipernity.com/doc/1148945/album/1280772
there is surely a lot more to do in testing activity (grey was at maiden flight ; blue-white-red with changes at bridles and a preliminary setting...) but the ROKKERstorm performances are showing a very good stability even in fast changes of wind speed and direction
SMAC from Italy
So I had a bad day today with my Barn Door kite crashing into the water and taking the rig with it... basically, the wind speed picked up too much, and when that happens, this kite tends to get pulled down. That's happened plenty of times before, but I haven't had it actually cause a crash until today. This time it just kept going down until it ran out of sky to fly in. I was able to recover the kite and the rig, fortunately. I was actually lucky in that I forgot to turn on the camera (PowerShot S100), so I'm hoping that if I let it dry out for a few days before attempting to turn it on again, it may be okay. The rig was powered on, though, so my hopes for any of the components on it (servos, receiver, video transmitter, FPV camera) surviving are lower.
Anyway, I think this was the last straw to convince me to make a Rokkaku instead of continuing to use this Barn Door kite. Getting pulled down when the wind gusts close to Bft 4 is the main problem with it, but it also generally just moves around a lot. It would be fun to fly one without a rig, but my confidence in it as a KAP kite is not so great anymore.
I've never had a Rokkaku before, but from what I've read they are quite legendary for their stability while also having a decent wind range. I've seen a video of a 2m Rokkaku in Bft 4 winds, and while it flexed quite a lot, it still flew at a high angle and was quite steady. This makes me think it would be more suitable for KAP than the Barn Door kite. I'm wondering, though, do you think a Rokker is a better design? My Mini Dopero already handles the Bft 3-4 range well, so this would be mainly for light to gentle winds. But as I found out with the Barn Door kite, being able to stay in the air when it gusts a few mph higher is important. I know the vents should help with handling gusts, but will they increase the minimum wind speed for lifting? Another possible concern is my skill in making kites. Are there any tricky aspects of making the vents, or do you basically just make a partial seam between the upper and lower pieces of fabric and reinforce the edges with dacron?
A Rokkaku is our main camera lifter; a 2 by 1,6 m version accounts for more than 80 % of KAP sessions we do. It is perfect from 0-15 km/h (0-3 bft - 0 because sometimes it's zero at the ground level but it blows higher up, and a Rok can be pulled up there) and can be flown up to 25 km/h (4 bft) ... in stronger winds we use a large delta or a "royal 69" sled (and anything above 40 km/h is too exhausting to enjoy).
A Rokker seems very interesting - might make one to check it out - though an ordinary Rokkaku is always so glued to the sky that stability was never an issue :-)
Hi KAP_Iasa thanks
to montagdude : the ROKKER for KAP is best kite I know (I have several ROKs, DOPEROs and DELTAs) for stability and wind range
the construction has no special trick or hidden detail ; the two sails are joined only in middle and at external tips; the two sails have same width and are sewn flat one over the other; I recommend to use a solution so that the tension of lower sail and the bowing can be set as separate functions ; lower edge of upper-large sails needs a kind of stiffening... mylar...dacron
I suggest to use a quality of sail low stretch and to have all external contour reinforced with low-stretch
sorry, really sad for your Barn-Door kite and your RIG dropped in water
SMAC from Italy
Thanks, guys. I'm thinking I will build a 7 ft (2.1 m) Rokker. It would be a bit smaller than my Barn Door kite (2.9 sq meters instead of 3.8), but it seems like lots of people use 2 m Rokkakus in light winds, so hopefully it will still big enough for what I want to use it for. This size would make it a lot easier to manage than the Barn Door kite, since I could leave the horizontal spreaders in place and still fit it in my car. To make it extra light, I may splurge on some Icarex sailcloth instead of the Texlon ripstop nylon I used for the other ones. I can steal the P4X tubes from the Barn Door kite. It should be fun!
Sorry to hear about your accident montagdude. Did it just lose altitude or did it dive to one side as well? I have found that giving the kite line slack can help right the kite if it dives. If it loses altitude without diving you just have to wind in as fast as you can, but that can be difficult if the pull is too strong. You can't go wrong with the Rokkaku. A 7ft Rokker should be adequate for all your KAP needs. From my limited experience, the ROK has been my most reliable KAP kite. The only issue for me is that it can pull like an Bull when the winds get too strong.
kbunited, no issues with the wind pulling it down when it gets stronger? That's the main problem with the Barn Door kite. I think part of the problem is that with it being so big, the diagonal spars flex too much, which causes a lot of drag. But even my much smaller one does that, and I've seen videos of big Roks still flying at a high angle in pretty strong winds with the spars flexing severely, so I think it is partly a characteristic of the design too. Of course, vents should also help handle gusts.
I realized that I mistyped in an earlier post. I had said that it gets pulled down in gusts close to Bft 3, but I meant Bft 4. It handles Bft 3 just fine. I edited the other post to correct that.
Interesting, but I see your point. The design of the Rok lends itself to its high flight angle. Just be mindful that it can also lose some altitude in really strong winds. It happened to me on a few occasions, but it didn't drop too low. I guess really high winds affect most kites in a negative way.
Right, I think it will happen to any kite at a certain wind speed, if something doesn't break first. It probably has something to do with the shape too. With the barn door kite, when the wind gets strong, the bottom part has the most drastic bending and billowing. You can sort of see the effect in this picture, though at the time it was taken, it wasn't blowing strong enough to start pulling the kite down:
As the wind gets stronger, the bending and billowing causes the bottom part to start looking very narrow, reducing the effective area. Just thinking about that, decreasing the area on the bottom part will shift the center of pressure farther up, which would rotate the kite to an even higher angle of attack and exacerbate the problem. The Rokkaku shouldn't have that problem, at least not to the same extent, since it is symmetrical from top to bottom. At least, that seems to make sense now that I think about it.
Anyway, enough about my other kite, since this is the Rokker thread. Thanks for the advice everyone. I'll try to post some pictures and/or videos here when I get the Rokker done.