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Author: Subject: CrossFire II 6.5
Quantum




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[*] posted on 10-18-2008 at 09:57 AM
CrossFire II 6.5


The quality of this kite build and materials is very high. Edge protecting dacron strips, quality silicon coated ripstop, and reinforced bridle attachments all demonstrate HQ's commitment to quality. The bridle is made with sewn and sleeved spectra lines and are nicely color coded. The DTS system makes this "fixed bridle" kite flexible for lift or speed. I can't say enough good about the materials and workmanship.

That said, this kite flew horrible out of the bag. I started in modest winds, 5-8 MPH and had a very difficult time getting this kite in the air. Frankly I was very surprised since there was enough wind to fly the 3.0m Beamer, so when I switched to the higher surface area, I was expecting no problems and some fun great pull!

The behavior was more like a drogue chute than a lifting foil. To get the kite in the air, I had to drop the break lines 2 knots back (looser) than the manual's recommendation. Given quality of the foil, I guessed this must be a bridle and angle of attack problem. The DTS system allows an AOA change so rather than pack it in for the night, I decided to play around with it.

Moving the DTS up from the "beginner" setting to the "advanced" setting helped a lot. With that change, effectively decreasing the AoA, the kite flew much better. Launch wasn't anywhere near as much of a problem, and the CrossFire flew much better. It was very sloppy in the corners with a tendency for the tips to roll up at the window's edge, but it was flyable and had some decent pull and lift.

I flew this kite on this setting for a while, but I still felt that the AoA was too high for balanced flying. Far too much kite speed was required to keep the tips expanded and the kite stable. I was used to being able to hover my Rev anywhere in the window and I had expectations of a more stable flying kite with the Crossfire.

So, taking a hard look at the DTS and the manual, I decided that the DTS settings were off and needed to be changed to lower the AoA some more. I found by adding a knot to the DTS adjustment line, it shortened the leading edge line reducing the AoA. Now with the extra knot, the kite flew better. Much less speed was needed to keep its shape and there was better performance in the corners. I was fairly happy with this solution and continued to fly this way to get my skills up with the larger foil.

I finally got around to searching the net and this forum to see if there were any known issues with the Crossfire II bridles. I found there were some bridle problems with the early CF II. The serial # on my CF is #004 and DOM is 08-01-05, so I guess that qualifies as early. The details in the thread below helped sort things out.


bridle discussion

I really wish the manual would have had better engineering drawings for the bridle & DTS layout. All the manual had was a schematic - no measurements at all. Measurements would have saved a lot of guess work. After finding out that the basic setting should have all 3 DTS knots even, I change by bridle settings again. I'll post the pictures of my solution. I ended up adding 2 knots to the settings line an that really stabilized the flight behavior.

Quantum

The picture shows the factory settings. I'll put some better rez pictures on the net if there is interest.

crossfire_initial_dts_low.jpg - 17kB
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Quantum




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[*] posted on 10-18-2008 at 10:09 AM


The picture in the initial post is the way I got the kite from the factory. You can see that the AoA was much higher if the ABC lines (top/leading edge to bottom/trailing edge) are set this way. At this AoA, the kites lift vector is tilted too far back.

By adding two knots and moving the original two, I was able to align the three bridle points when the DTS is set on the base setting. I believe this is how the foil is designed to operate.

crossfire_finished_dts_med.jpg - 41kB
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Quantum




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[*] posted on 10-18-2008 at 10:21 AM


With the changes shown, I'm very pleased with how the kite flies. I'm still gaining experience with static flying this kite, but with now on the less lift setting, there is less of a tip roll up problem at the corners.

By the way, the top knot - isn't really flyable, but with this setup, the three lower knots give a pretty good range. The 'lifty' setting is still the lowest knot.

I find that the 2nd or 3rd work best for the winds I have here. With the 3rd knot the kite is a bit faster and still gives good power.

Cheers,

Q
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SCREWYFITS


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[*] posted on 10-18-2008 at 06:15 PM


Wow Q,

I'll start by saying that I'm assuming that you are new to foil kiteing, sorry if I'm incorrect...

You seem to understand the whole concept of the way these kites work for the, what seems to be small experience you have with foils (again sorry if I'm incorrect)... It's great to have someone new come into the sport and get his hands dirty and play around with the kites to figure out better options...

It seems you've made all the right adjustments, I've played with the early and late models and they both need adjustment in my opinion, just the early more so, as you've experienced... I agree a very fun kite once corrected...

Great choice's by the way...

Also welcome to the forum...

Screwy...




Naish, Helix 9m / ARX 11.5m
Flexifoil, Blade IV 6.5 Blade VIP 8.5
Peter Lynn Twister II 7.7m, Viper 2.6m x2, 3.9m x2, 5.3m, 6.8m, Reactor II 4.4m
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Flysurfer Titan 9.5m, Speed 10m
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"I wanted to change the world. But I have found that the only thing one can be sure of changing is oneself" -Aldous Huxley
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Quantum




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[*] posted on 10-19-2008 at 06:23 AM


Thanks for the feedback Screwy, yes I'm a new to foil kites other than my Snapshot which is not in the same league as the tractions. Also, I'm genetically predisposed to tinker and get dirty. Over the years I've flown a lot of different things (stunt kites, rc-aircraft, sailplanes, small aircraft, hang-gliders) - that practical experience helps a lot. You can just feel what's wrong sometimes.

I also have a couple of degrees in aero-engineering which helps with the theory. I studied controls and feedback systems mostly, but I've spent time in the wind tunnels back in school. As I've been learning about traction kites, I'm finding some interesting physics and challenging design issues. I'd love to see the manufactures technical data. The engineering geek in me want the L/D numbers and drag polars for the foils. I figure they must have this data to select optimal bridle points for the kites intended use.

Kite shape is a total mystery to me. My gut tells me there is some hard math behind the trade-offs, for example, between a foil's inlet size and locations, foil stability, and the kite's total drag. I'd expect similar trade-offs with camber, AR, and projected AR. Good design is really selecting which trade offs to make and that is hard. Hats off to the guys who make choices well.
Q
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furbowski


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[*] posted on 10-19-2008 at 08:02 AM


I've pitched quite a few the BIII to folks who see me flying on the beach and seem seriously curious, so it is a shame to see the CFII is not up to the same standard.

I got a CF 3.2 a little while back and I've learned that it inflates a bit slow, takes a bit of flying to get all the cells tight and then it's like BANG! it powers up with a yank like getting snatched by a gust.

I put it on a bar for a guy on the beach who was getting bored with his little BEST kitesurf trainer, just tied up the brake bridle a bit and transferred the powers to the 30m lines on the trainer, and it was so bad at inflating (it wanted to fold the trailing edge downwind just below the D lines) he couldn't launch it by himself, i had to be kite monkey and still he had to pump it halfway up to the zenith. But once it was powered up he grinning nonstop through his first scuds and hard body drags!

Q, thanks for the quick discussion of trade-offs above, it made me appreciate (tho def not understand) what kind of thinking must have gone into the CF's design. It's interesting to hear about your background... I reckon you'll be dropping a few good posts here as you progress!

I had to play (tinker) with my ace quite a bit when I first, it was good fun!

I'm pretty much a rookie myself, but welcome to the forum...

cheers,

furbo




fixed bridles, flying static, been two years now... ??? folks must be wondering....

sting 1.7, dp power 2.5, crossfire 3.2, ace 5, blade iv 6.5, ace 8, ace 12...

also a couple of arcs, 12 syn and 12 phanny, but i\'m not yet up to speed on them.

(13.11.09)
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acampbell


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[*] posted on 10-19-2008 at 09:43 AM


Quantum,
From your picture(s), it appears that you have one of the first few Crossfire II's that slipped through with some incorrect bridle knot placements in the DTS. HQ publeshed the equivilent of an FAA AD (Airworthiness Diretcive), and I am surprised that your dealer did not notify you.

The giveaway is the fact that in your first picture, the knots at the top of the DTS where the bridles attach are not lined up.

To your credit, your modification puts the knots right where they should be according to HQ's bulliten, with the top knots lined up evenly. FWIW, HQ has you move the knots rather than add one more.

Odd thing is is that when I first flew my un-corrected CF II 6.5m, it flew fine on the high lift setting but not well on the low-lift buggy setting.

I notice that all Rev pilots show great skills with foils right off the block, but I would not compare a Rev's behavior in the window to a foil.

If you want, drop me a note to angus "at" coastalwindsports.com and I will send you the HQ bulliten.




Angus Campbell
Coastal Wind Sports
...where life is better when it blows!
Golden Isles Region, Georgia, USA
912-577-3920 new number

Flying on the beaches of Jekyll Island
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adambweird




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[*] posted on 11-6-2016 at 08:14 AM


I just did this on my 5m Crossfire II after flying it for half the summer as it came from the factory (at least I think, lol, got it used in like new shape). Its behaviour matched what ive read in this post and what Ive been able to dig up in other posts here and in various other forums archives. Hopefully ill have some wind to test out the changes after the i watch the Browns lose to the Cowboys ( hopefully not, but it is the Browns, lol).

Edit: Kite came off the ground MUCH better and flew with a lil work in maybe 2 mph wind. Overall flight was better too with less tip curl near the edges of the window and it seemed to fully inflate faster as well. Wish id have done this mod earlier in the summer, lol. Was a good bit of relaxation after watching the Browns get pounded, lol.




HQ: Symphony Beach 1.3, 2.2.4, Crossfire II 5m, Apex II 5m
Flysurfer: Outlaw 10m
Peter Lynn: Pepper II 3m, Venom II 13M
Born: NS3 4m
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