I was 3 miles out from my anchor and the wind shuts OFF, completely when the sun sets. Seriously like someone flick a switch. The snow was about 1.5' deep with 8'' of slush underneath and I didn't bring my skins out with me so getting back was going to be a long hard process. My plan was to dump the kite and skis on one of the islands and hike back from island to island to avoid post holing in the snow/slush. Would add mileage but less fatigue. I could fly out and grab the kite/skis another day.

It was well below freezing so the slush snap freezes when it comes into contact with air above the snow. Adds 5lbs to each foot in a blink.

I was really, really motivated to get that kite in the air. :D

Kent or Chris -

You've both probably flown the F-arc 1200 more than any of the others on here. I have flown mine both umodded and with a SLarc-type front bridle using a 60 cm bar with about 15" throw and 10" strap adjustment. I saw Kent's throw length comments above and wondered if that refers to the 1200. What do you think the total throw range is for a 1200; i.e., as if you were not using a depower strap and had ape arms to run it through it's full range?

My sense is that the Farc with a small chord and high aspect ratio just doesn't have the ability to use all its potential depower range with the standard Arc bridle-less set-up. The front bridle let's me lower the angle of attack and depower the kite more than is possible without it. It still steers like a truck. I wonder if the only way to improve that would be to go to a long, old-school bar, maybe 70-80 cm; or try a pulley bar like on the older bows and SLE's and deal with the higher bar pressure.

krumly

I think I figured out why the F-arc opens up when flying. This weekend I noticed the kite opens up slightly when on the decent a of a jump. I after some research on aerodynamics I found the solution.

When you are falling, your decent is perpendicular to the true wind, createing apparent wind diagonally across the shoulder of the kite. Since the kite is in an arc shape, the curve of the kite slightly deflects the wind createing more lift in the shoulders than in the center, which causes the kite to change shape and and become more open. This can be applied to rideing horizontally also as you create apperent wind when you begin to move.

I will post some pictures tomarrow since this is really confuzing to understand.

Snake,

Here is what I thought when I first saw this post.

Assuming that the entire length of the kite has a profile like a wing (the top skin is longer than the bottom skin as the air travels over it), this would create lift throughout the length of the kite. As the speed of the air passing over the foil increases , it will create a force that is perpendicular to the skin at any place you measure it. It is easy to understand that the middle of the kite creates lift, but the same force that creates lift on the middle of the kite will also push the edges out. This force is counteracted by the strings. If you had really short strings, lets say 10m, the kite would not be able to flex out as much because the strings are trying to pull the kite closed. If you had really long strings, like 40m, the kite would not really notice the strings pulling it closed, but it would still never go straight because the middle of the kite is not supported by bridles. Since the ends of the kite are the only parts with a counter force, the kite will always be bowed.

Jason, your theory is close but not quite right. An arc will always fly in a near perfect semi-circle when it is stationary. When the wind speed increases, the lift everywhere on the kite increases, so the kites shape stays the same.

The reason the kite opens up when the apparent wind starts to develop is because there is another force acting on the shoulders of the kite. The apparent wind moves over shoulders diagonally at the angle of the lift to drag ratio. This causes the the curve of the arc shape to deflect some air, which, according to newtons 3rd law, causes the kite to react in an opposite direction, which is outwards. This causes there to be more lift in the wingtips, changing the shape of the kite to have more projected area.

My original observation in the first post is backed up by theory. I used a lift to drag ratio of 8 to do my calculations. This gave me an additional 3.55 degrees of deflection which increases the lift 35.5% in the shoulders. This in tern causes the kite to open up to a projected area of 12.8725m, not far off from my inital guess of 13m.

This picture shows how the extra lift is created. The air (black arrows) curves around the skin of the kite (blue arc), which pulls the wingtips outwards.


This picture shows the kite (orange box) from the side. The red arrow is the true wind, the blue arrow is the apparent wind, and the black arrow is the the wind created from forward movement. The blue line shows how the wind flows over the shoulder of the kite. The angle of the apparent wind is drawn much steeper than what it would be to help illustrate how the wind is flowing.

Snake,

Can you please let me know what calculation you used? What assumptions did you use? How did you model the kite?

Since I don't know the answers to those questions, I cannot comment on most of your post; however, I am mostly interested in hearing your explanation for "the lift everywhere on the kite increases, so the kites shape stays the same." My diagram shows that as the air moves faster over the foil, the forces acting perpendicular to the foil at any given section increase. This is what I theorize opens up the kite. There are other factors, but when someone is moving 40 mph in 20 mph winds, the apparent wind takes on a significant role in the shape of the kite. I do realize, however, that the force of lift at the center of the kite may very well be too great for the edges to deflect due to apparent wind alone, which is where your assumptions may complete the picture.

It would be interesting to hear a kite designer's input on this. I don't have any experience in that area.

-Jason

In the real world, an arc tends to compress a bit as the wind increases. They can "flair" if the wind suddenly drops. Gusts tend to cause the tips to come together while the kite elongates. The bulk of the wind pressure on the kite hits the "projected area", which causes the kite to slightly elongate in higher wind or apparent wind due to airspeed.

What Bob describes is what I see. It seems to be the visual manifestation of the gust response we feel--more wind reduces the projected area.

Philip

Bob explains what I have experienced. They stronger the wind the tighter my projected area. Opening in lulls. Clapping in crap.

There's not much worse to an Arc flyer than a case of the clap.

I have notices my Venom loses some area when the wind is strong. I am pretty sure this is from PL reduceing lift in the wing tips to gain speed. That is why chargers had the clapping problem. Old S-arcs F-arcs have the same profile through out which means eqaul lift through out. The S-arc has smaller tips than the center so it also has some list lift in the shoulders. That is why older Arcs are more stable and slower than the new Arcs. This also means that the angled wind makes the kite have more lift in the shoulders in than the center. F-arcs are the only kite I have ever seen this happen on and I think it is the only one that does this.

Jason, say the kite is above your head and the wind is 15mph. The kite will be in a semi-circle shape because in that shape the shoulder lift and the center lift are balanced. If the wind doubles to 30mph, the kite have 4x the pull. The pull will increase the same everywhere equaly on the kite so the shape wil be the same.

There might be some slight pressure on the wing tips for stabilization and autozenith but there isn't any significant lift coming from the sides of the kite. Something was pushed to the limit at the wingtips on the charger and so it had the tipclap issues in some conditions.

Quote:

Originally posted by Feyd It definately isn't a begginer kite. But in light winds it's a dream to fly. The 1200 is the sweet ......

Yesterday I had my first winter session (not counting surfing session just two weeks earlier, yes surfing in Ontario in January)
Wind was light 8-10 knts, 3"powder on top of 2" harder gritty stuff, "snowkite" Nobile board.
I had three choices to fly; Aurora 15m, JN Luis 10m and F-1200.
Wind was light maybe too light, but I remember one of the Feyd's posting regarding low wind performance of the F-arcs.
So decided to try the F-arc, middle zipper only, so only half inflated, got it filled with "Scorpion" technique; ie praying hard for it not to bowtie, a success, inflated fully.
I had it on a "navigator" copy 56cm bar with 28m lines and 45cm bar travel.
Boy..., this thing wants to go and wants to fast. Apparent wind wow...it felt like I was going twice or more the wind speed (no gps to verify)
Very stable, really quick turning, and upwind like no other.
I found it really likes to fly with almost no rear line tension, I was trimmed all the way in, so power management was in bottom 1/4 of the bar travel.

Long story short I was amazed how much fun I had flying it. If one can get past the occasional bowties and limited depower (~50%) it is a truly an amazing kite to fly. It does not show its age at all
Can't wait to try it on water next.......

Not to sound rude mdpminc, but how much do you weigh? And how would you say it compairs to your your phanny and your scorp?

Jeeeeeze Snake you NEVER ask a lady her weight. Not in public anyway

That's a great description of your session mdpminc. I'm glad you had a such a great time on the F-arc. Works very well with the Navigator bar's throw I think.

@ Krumly I suspect you are right about the limited depower of the F-Arc. At the time it was designed I don't know that they really put as much consideration into the depow as they do in "modern" kites. I think the focus was probably more on pushing the powered performance. WHich I think they did quite well.:roll:

The "holy grail" is to get a kite that has mad performance but can be depowered signifigantly when needed. There always seems to be a trade off IMO.

I've got mine set up so that it is slightly oversheeted and I rely on heavy stall as a means of power management and trimming to fine tune but I deal with the F-Arc like it's a fixed bridle using the brakes to slow it down when needed.

To me it generates power like a fixed bridle but still, like mdpminc say's it gets about 50 (maybe 40) percent depow when you need it. The longer bar throw is key to getting some depow out of her. A bar like an '04 or -07 PL won't work nearly as well w/o some modification IMO.

I've been thinking about how to get her to turn faster w/o having to muscle float turns. The pulley bar may be one route would try, the long 70cm bar is just a way for me to put my helmet to work as I always whack myself in the head with bars that long. I've been considering putting together a steering system similar to waht came on the Flexi, Sabre MK1. It had a crossover line than worked similar to a pulley bar. It seemed convoluted at the time but as I reflect it was actually pretty elegant.

After reading mdpminc's post I'm going to make an effort to get out on the F-Arcs today I think. :evil:

In answer to the question how does the F-Arc compare to a Phantom or Scorp I would say that the Scorp is an excellent teacher for handling skills that translate well to the F-Arc. FLying wise they aren't even close. The Phantom, tho sharing the same AR as the 1200 is so detuned and docile there's no real comparison. IMO.

Has anybody ever considered putting a VPC bridle on an Farc?

Quote:

Originally posted by Snake Not to sound rude mdpminc, but how much do you weigh? And how would you say it compairs to your your phanny and your scorp?

not to be rude :-) 207lbs naked, 230lbs in winter gear

Quote:

Originally posted by Feyd In answer to the question how does the F-Arc compare to a Phantom or Scorp I would say that the Scorp is an excellent teacher for handling skills that translate well to the F-Arc. FLying wise they aren't even close. The Phantom, tho sharing the same AR as the 1200 is so detuned and docile there's no real comparison. IMO.

As Feyd said.......and to add it takes same amount of muscle to get the P2-15m to turn fast as it did 1200.

Quote:

Originally posted by Bladerunner Has anybody ever considered putting a VPC bridle on an Farc?

I think "dog ears" would have to be removed to attach VPC, but could be worth to try it.
Anyone outhere with a 1600 that is collecting dust in their garage, I could dust it off for you and try the VPC thing on that :saint:

I'll leave 1200 as is, it just flies perfect the way it is.

I've been talking with some people about that and there is some thought that a VPC on such a hi AR wing may be more of a detriment than a benefit.

I'm with mdpminc, I was going to remove the dog ears on my 1200 in hopes of getting rid of flutter and gaining some of the performance that removing the ears is supposed to offer but damn the kite flies so nice I just don't want to mess with it.

The 1600 is so long and thin I think if you threw a VPC on it, you would have half the kite halfway through a turn before the other half even knew what was going on.

Unlike mdpminc, I won't fly it naked to get the extra performance out of it. :wee:

Quote:

Originally posted by Feyd ....... I was going to remove the dog ears on my 1200 in hopes of getting rid of flutter and gaining some of the performance that removing the ears is supposed to offer but damn the kite flies so nice I just don't want to mess with it..........

I was thinking to saw-in thin fiberglass battens (similar to what Waroo had on trailing edge) to stabilize the ears, maybe that would help, but I only observed the flutter during harder turns and none really during straight flight.

Quote:

Originally posted by Feyd I've been thinking about how to get her to turn faster w/o having to muscle float turns. The pulley bar may be one route would try, the long 70cm bar is just a way for me to put my helmet to work as I always whack myself in the head with bars that long. I've been considering putting together a steering system similar to waht came on the Flexi, Sabre MK1. It had a crossover line than worked similar to a pulley bar. It seemed convoluted at the time but as I reflect it was actually pretty elegant.

Feyd, I looked up the sabre and it has a normal depower bar. Is the crossover in the bridles? Pully bars work well for better depower and turning but at the cost of double the bar pressure and less direct feedback from the kite. I have an idea for a bar that would keep everything the same but speed up the turning. I'll mod my bar and try it out on my venom this weekend.:wee:

thinking out of the box, ULS System could be the answer to enforce control over the F-Arc:

http://vimeo.com/30119969

the idea is to remove the bar. a bar limits the massive action and depower range of your arms. a bar limits the left/right difference needed for steering. simple solution: get rid of this thing. control the kite "paraglider style" with brake handles for each arm. only drawback: no more single handed riding.



of course on normal length lines for the f-arc or other kites.

i will try the same system with my new sliding ring harness.

I was doing some more reasearch one the F-arc being I am getting some (thanks again kent!)and found some more interesting info. Peter lynn made an F-arc 2. It was marketed toward land use because of the high AR. Though the days of one color fabric and calling them "Arcs" was over so they came up with new name. The Phantom. It was interesting reading what was said about the prototype from a test rider. "I was disappointed with the bottom
end of the F2 16". That was in the first sentence. Reminds me of what Feyd said once, The Phantom is the F-arc with it's balls cut off. This seems to be the case from everything I have read. Prefomance and raw power was traded for relaunch and depower.

http://sports.groups.yahoo.com/group/arcusers/message/7423

http://www.powerkiteshop.com/news/peterlynnfarc.htm

On the ultra short line thing.

I see how this method gives you greater depower / turning etc. but I don't think you could jump worth a bean ? Glide, yes but how do you send it ? It would certainly be a safer way to kite but this is about the Farc , not the safer way to fly ! Something tells me that's not the Mod' that Snake is after! ;-)

I agree with Herc; remove the bar to get massive throw lengths/depower on the brake lines.

Here's a vid that shows this better than the one Herc used. He's probably too modest to use this one:
http://www.youtube.com/watch?v=LKDroQGIq7c

What about running a line from the handles to the chickenloop so you can let go?
What about making the handles attachable like Bobalooie's so you can fly single handed?

I was out the other day and got caught in high winds while flying an 11m Apex 4. It had gotten to the point where I exhausted the trim range and couldn't hold position at the edge of the window. I flew her to a wind shadow, landed and shortened my lines to 12m.

With 12m lines I shaved a lot of power off but it was still very capable of jumping. With the short lines she snaps a turn like plenty fast to jump with. Redirecting my tacks was a difficult to manage without getting lofted a little. The windspeed could have been a strong influence in that tho.

If the lines were much shorter, I think the kite would be getting choked out.

Very cool video there Herc.

I am going to try removing the bar ala Herc's set-up on my front-bridled FArc1200.

The kite will fly on a single front line with a Y divider and rears detached, for a bit. But steering input is non- existent with a bar, even a long bar with long throw and long trim strap. Seems to me a front bridle is the only way to get even more depower out of the kite - it moves the front line attachment points further forward. Having control of the rears with separate handles and lots of throw may be the only way to be able to get steering input.

krumly

We use to ride with what was called a "free bar" setup. Basically you take the center depower line out of the center of the bar and move the bar above the line. Then attach the bar to the center line with a small insignificant bungee or line (in case you accidentally drop the bar). This gives you control bar type control with unlimited depower (at least as long as your arms are), you can still ride one handed by moving your hand towards the center of the bar and you still maintain all the safety features.

@krumly: i am very interested in your results with steering the bridled F-Arc using free-brakes.

@windofchange: a free bar is for sure a very good idea ! i must try that out.

in the meantime, i have improved my setup using better grip - handles and some bungee cord to attach the break lines to the sides of the harness. btw, the handles are the wood grips from corkscrewers :-) anatomically perfect !
i have also added additional grip positions with two small aluminum tubes and two bottle caps.

here are some pictures:

https://picasaweb.google.com/111510368262264907350/19Marz201...