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Author Topic: sport kite roll bars  (Read 1494 times)
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OZKITE_PILOT
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« on: December 29, 2018, 06:53 PM »

gday all
hope you had a great xmas!!
just wandering what the idea of " roll bars" is on a stunt kite ?
you don't seem to see many on different stunt kite manufactures!
thanks
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midibot
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« Reply #1 on: December 30, 2018, 02:42 PM »

Don't seem to see roll bars (rollbars) being used on current offerings as much. My Benson Deep Space has them factory, as does the French Connection and French Kiss; JoE Talon.

I also have an R-Sky NFX that has them (possibly custom or an add-on, not sure).

I saw an article on kite clique going back 10 years or so about retro-fitting them to an Exile.

Most of the kites I have listed go back at least 10 years, so....?

(I probably missed quite a few.)

Have noticed that the roll bar affected my Berkeley hop/Sleeping beauty launch, till I tried popping the nose up a bit first.

.

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« Reply #2 on: December 30, 2018, 03:11 PM »


Only Benson and Sportkitedesign kites come with rollbars AFAIK

They are a Benson (& Wardley) invention that came with the Deep Space design.

The probably can be retro-fitted to most any modern design to reasonably good effect.

-Frazer
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Lee S
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« Reply #3 on: December 30, 2018, 03:27 PM »

Both Jest of Eve kites, Trident and Talon, came with them, I believe they were credited to Benson as a design. Worked well on those kites. As also stated, the French Connection also came with them, as well as a strange brace across the sail, to prevent wing distortion during roll up. I don't recall that working very well on that kite. As a feature, I always felt that roll bars were too much additional weight for a 6 ft kite, but carried well on an 8 ft wing.
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OZKITE_PILOT
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« Reply #4 on: December 30, 2018, 06:00 PM »

would the roll bars create much drag on the kite ?
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Frazer
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« Reply #5 on: December 30, 2018, 06:55 PM »

Both Jest of Eve kites, Trident and Talon, came with them, I believe they were credited to Benson as a design. Worked well on those kites. As also stated, the French Connection also came with them, as well as a strange brace across the sail, to prevent wing distortion during roll up. I don't recall that working very well on that kite. As a feature, I always felt that roll bars were too much additional weight for a 6 ft kite, but carried well on an 8 ft wing.
Yes, all true, but those kites are no longer available, and the less said about the woeful French Connection the better.

The were on AirOeurve (pile on everybody) kites too ... and Atelier released the Transfer XT.z, with very ill-conceived (yet still derivative) "rings".

-Frazer
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Frazer
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« Reply #6 on: December 30, 2018, 06:58 PM »

would the roll bars create much drag on the kite ?
I shouldn't think so, we're only talking about a couple of pieces of narrow gauge fiberglass or latterly carbon fiber.

-Frazer
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DD
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« Reply #7 on: December 30, 2018, 07:15 PM »

Not much weight, it doesn't hurt the ul. I have deepspaces and talons with them. Not really sure they help all that much on keeping the kite from deforming.
My understanding was that Mark from jest of Eve that made the talons got some kind of "approval" from Tim Benson.
The Dodd's French connection had them as well but they weren't as nicely made as the the others, the rod  quality wasnt the best and they were a tad short. The roll up additional bars were new on the FC but also weren't the best either.
The sail pattern for the FC was the result of a contest that Dodd held here.
I had an early FC. The overall quality and assembly wasn't great and was designed, I think, to be a poor man's Benson. The one I had also was prone to having a stretchy bridle. I waited to get mine "signed" by Dodd.  I passed mine along. I know they made an ul version as well and I believe a second version of both.
Overall rollbars catch lines from yo-yo, even if your not super precise and  make for interesting tricks while rolled up and even "sideways" yo-yos.
 
« Last Edit: December 30, 2018, 07:17 PM by DD » Logged

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« Reply #8 on: December 31, 2018, 04:02 PM »

would the roll bars create much drag on the kite ?
  Theoretically they should create no drag at all.  They sit in a wind void created by the sail so any drag would be based on the weight which is negligible.
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« Reply #9 on: December 31, 2018, 04:13 PM »

Not much weight, it doesn't hurt the ul. I have deepspaces and talons with them. Not really sure they help all that much on keeping the kite from deforming.
My understanding was that Mark from jest of Eve that made the talons got some kind of "approval" from Tim Benson.
The Dodd's French connection had them as well but they weren't as nicely made as the the others, the rod  quality wasnt the best and they were a tad short. The roll up additional bars were new on the FC but also weren't the best either.
The sail pattern for the FC was the result of a contest that Dodd held here.
I had an early FC. The overall quality and assembly wasn't great and was designed, I think, to be a poor man's Benson. The one I had also was prone to having a stretchy bridle. I waited to get mine "signed" by Dodd.  I passed mine along. I know they made an ul version as well and I believe a second version of both.
Overall rollbars catch lines from yo-yo, even if your not super precise and  make for interesting tricks while rolled up and even "sideways" yo-yos.
 
The FC was a flop for many reasons and it wasn't the design that was the big issue.  Not the greatest design but it was a capable kite killed by choice of materials IMO.  I had one that only lasted a couple months before the sail stretched so bad it was un flyable but thats a problem with just about any NTK kite with a nylon sail be it a diode or whatever.  The nylon they went to was really bad.  Loose weave, poor coating and really stretchy (think garment nylon stretchy if not worse).  I've gotten better cloth taking fabric from Joanns and spraying it with Varathane brand poly urethane.
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DD
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« Reply #10 on: December 31, 2018, 10:18 PM »

Not much weight, it doesn't hurt the ul. I have deepspaces and talons with them. Not really sure they help all that much on keeping the kite from deforming.
My understanding was that Mark from jest of Eve that made the talons got some kind of "approval" from Tim Benson.
The Dodd's French connection had them as well but they weren't as nicely made as the the others, the rod  quality wasnt the best and they were a tad short. The roll up additional bars were new on the FC but also weren't the best either.
The sail pattern for the FC was the result of a contest that Dodd held here.
I had an early FC. The overall quality and assembly wasn't great and was designed, I think, to be a poor man's Benson. The one I had also was prone to having a stretchy bridle. I waited to get mine "signed" by Dodd.  I passed mine along. I know they made an ul version as well and I believe a second version of both.
Overall rollbars catch lines from yo-yo, even if your not super precise and  make for interesting tricks while rolled up and even "sideways" yo-yos.
 
The FC was a flop for many reasons and it wasn't the design that was the big issue.  Not the greatest design but it was a capable kite killed by choice of materials IMO.  I had one that only lasted a couple months before the sail stretched so bad it was un flyable but thats a problem with just about any NTK kite with a nylon sail be it a diode or whatever.  The nylon they went to was really bad.  Loose weave, poor coating and really stretchy (think garment nylon stretchy if not worse).  I've gotten better cloth taking fabric from Joanns and spraying it with Varathane brand poly urethane.


Accurate assessment in my opinion. Guess I expected more
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« Reply #11 on: January 01, 2019, 12:52 AM »

Theoretically they should create no drag at all.  They sit in a wind void created by the sail so any drag would be based on the weight which is negligible.

Huh?  Huh   In nearly all cases roll bars sit on rear of the kite, which is the upper surface of the airfoil.  This isn't a wind void at all!


Having said that, they produce very little drag - certainly not enough to outweigh their benefit on kites where they work well.

They can adversely affect kites that were not designed with them in mind, but that have them retro-fitted.  They retro-fit well on the early model Benson Gemini, but the weight of them alter the balance of a Minigem quite badly.

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Kevin Sanders

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« Reply #12 on: January 01, 2019, 01:08 AM »


...

I had an early FC. The overall quality and assembly wasn't great and was designed, I think, to be a poor man's Benson...
 
...

The FC was a flop for many reasons and it wasn't the design that was the big issue.  Not the greatest design but it was a capable kite killed by choice of materials IMO...


Not so much a poor man's Benson, as a poor man's R-Sky.

Not the greatest design?  The sail shape was (I'll be very kind and say "almost") identical to a 1st edition Nirvana - the graphic hid this.  The frame was exactly the same.  The standoffs were in a slightly different location, and the bridle was a basic 3-point, whereas Nirvanas came with a variety  Cheesy  The T-piece was a lump of aluminium, which put weight in a less than ideal location.

The materials used on the sail were not good quality - as others have said.  The kite never flew very well and looked shabby after very little use.

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Kevin Sanders

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« Reply #13 on: January 01, 2019, 01:24 AM »

Theoretically they should create no drag at all.  They sit in a wind void created by the sail so any drag would be based on the weight which is negligible.

Huh?  Huh   In nearly all cases roll bars sit on rear of the kite, which is the upper surface of the airfoil.  This isn't a wind void at all!


Having said that, they produce very little drag - certainly not enough to outweigh their benefit on kites where they work well.

They can adversely affect kites that were not designed with them in mind, but that have them retro-fitted.  They retro-fit well on the early model Benson Gemini, but the weight of them alter the balance of a Minigem quite badly.


 The area behind the sail on a kite has almost no pressure due to the fact that the wind is redirected along the face of a kite.  If you have ever flown a stack with the link lines too short or through the wake of another kite at close range you would understand what void I'm talking about.  Easiest demonstration I can think of is to put a wind meter behind a kite and move it back until you get a wind measurement.  That distance gets shorter with forward movement but elongates off the tail end similar to the wake of a boat.  The low pressure area should theoretically mitigate any drag roll bars create.  There was a video of Mark Reed doing a wind tunnel test years ago where he had short ribbons attached to the back of the sail and you could see some of the ribbons laying flat with little to no movement.
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« Reply #14 on: January 01, 2019, 03:40 PM »

 The area behind the sail on a kite has almost no pressure due to the fact that the wind is redirected along the face of a kite.  


You are confusing pressure and wind speed.  A sport kite pulls away from the flyer because of it's airfoil properties, not because of Newtonian force against the "front" of the sail.
Yes, there is lower pressure at the rear of the kite, just as there is lower pressure above the top surface of an aircraft wing when compared to pressure below the wing.  But to claim there is "almost no pressure" is wrong.

If you have ever flown a stack with the link lines too short or through the wake of another kite at close range you would understand what void I'm talking about.



No, that's because of turbulence, not a "wind void".  Watch any of the many videos that explain how wings really work e.g. http://youtu.be/UqBmdZ-BNig and you might understand what I'm talking about.

There was a video of Mark Reed doing a wind tunnel test years ago where he had short ribbons attached to the back of the sail and you could see some of the ribbons laying flat with little to no movement.


Little to no movement of the ribbons merely indicates smooth airflow in that region.
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Kevin Sanders

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