krumly - 14-2-2011 at 09:16 AM
OK, the pics don't prove anything, but I got a FArc 1200 to launch and stay up for a minute on a front bridle in very shifty winds. Before I could
get the camera back out to take a pic of it sititing at zenith, it had drifted back in a big lull, tacoed, and I couldn't save it.
It is set up with Bridle Layout B (the right side of CAD drawing).
A few observations:
The front bridle let's you prop it up for a nice hot launch and allows pumping the leading edge to inflate. Low winds still made it resist inflation
through the front valves - had to wait for wind to pick up at intervals, and then work the leading edge.
Running the rears lines through the 'choke rings' may give better tip control, but this kite still steers like crap, and having the brakes led forward
makes it hard to work the tips around separately from the front when kite is on the ground. I need to try it with the rear lines free of the choke
rings.
It flies really far forward in the window with the front bridle. Pull was nothing at zenith, with wind about 10-12 mph. Having a pulley at the line
connecting the front bridle to the front tip y-line seems to work fine - the kite SEEMS to self regulate its AOA. But I'm not totally sure. When it
drifted back in the lulls, I couldn't save it working the front line. Almost like it the pulley wouldn't move far enough forward to move the tow
point back forward for lower AOA. But when the wind is that light, and the kite is drifting back, you have no apparent wind, so a salvage is pretty
tough in any case.
Having the ability to move the tow point so far forward means steering control is about non-existant. Rears become so loose, you can't effect any
steering. Any brilliant ideas on how to get some steering while still letting the kite fly at minimal AOA? Sort of the quandry with Arcs I've used -
build power through speed with the bar out, but lose steering.
PL has mentioned Arcs dual moded like this need a lot of pre-inflation, and he's right. The tendency is for the kite to horseshoe or even taco fold
if there isn't enough internal pressure to let it open and launch quickly.
Guess I need some more consistent winds sort this out, but the ultimate goal is to work back and get it to fly in lower and more inconsistent wind.
krumly
herc - 14-2-2011 at 12:45 PM
highly interesting!
though i personally would be much more interested how a bridled arc behaves in normal 4line mode on a bar.
does the bridle improve depower ? does it help launching an underinflated arc?
krumly - 14-2-2011 at 09:01 PM
Herc -
The kite is dual mode. It launches as a single line kite but is steered with the rear lines. Really much like any arc with autozenith. The front
lines Y up near the kite, but this really no different than the autozenith abilities on any other Arc - Y line or no, you don't have individual
control of the front lines.
The front bridle lets the kite fly way forward in the window. Arcs have reflexed foils - some reflex in the center of the kite, even more in the
tips. That's as near as I can tell from the Arcs I have, pulling the profiles out on the table. This means the center of pressure and tow point moves
forward as AOA is lowered. That's why they are autostable in pitch. My winds were really flukey, but the pull was finger tip - like a bow - with kite
at zenith and winds maybe 12-14 mph. then it would drop to nothing,a nd the kite drifted way back and I couldn't work a recovery.
The right hand pic shows the kite sitting up just before I pulled the front line to launch. The front bridle let me hold it in that position, and
pump the kite to pre-inflate just like you would any other valved or open front foil. Yes it helps control the kite if underinflated, but more
importantly it lets you pre-inflate it like a foil as opposed to the typical Arc inflation procedure. It still flies like crap if you try to launch
it underinflated - clapping and whatnot -but you have some chance of getting it sped up and saving the launch by keeping the kite center flatter and
at a lower AOA.
Regarding 4 line control, the steering still sucks. As Chris Krug intimated, The FArc doesn't do much when you haul on the rears if it's not tight
and moving. High aspect, underinflation, and low airspeed equals slugguish steering, and having the kite use up even more depower throw due to the
front bridle doesn't help get the rear lines engaged. Need to work on that.
krumly
herc - 15-2-2011 at 01:56 AM
ok, thanks for further explaining it. i really like the idea that the a minimal front bridle helps for launching (and improving depower).
how did you put the bridle lines to the kite? connected to the internal strap / braid ? how did you made it air-tight ?
hope for some videos and pictures sometimes! i am really interested in this stuff. reminds me of the bridled rein - arc project http://rein-arc.be/?page_id=4 .
purist might say: no, never bridles on an arc. i do not share that opinion. its the same as with tube kites. there are still purists, who prefer
classic C-Kites (for its "raw" power - or in other words lack of depower ;-) ) but most people today ride SLE hybrid / delta / bow tube kites for good
reasons.
Feyd - 15-2-2011 at 05:15 AM
Great description Krumly.
I'm still not convinced that the F-Arc is the best canidate for dual mode SLArc because of the very reasons you outlined. It seems to me that
SLArcing is tricky enough without the added hassle of dealing with a freak like an F-Arc.
I wanted to fly them for a while and see what they're like so I'd have a baseline to go off of. I doing so I fiound that I really like the F-Arcs but
it confirmed to me that SLArcin it and getting desired results is going to be a lot of work if not impossible.
BUT, if you can get the desired results, or even close on the F-Arc then doing it with something like a Venom will be cake!
I'm going to make the bridal for my 12m F-Arc. I got my bridal line yesterday and the attachment points are in place so even tho I think it's not the
best option I'm still interested to see how it goes.
herc - 15-2-2011 at 05:28 AM
very cool! you doing a bridling experiment also? looking forward to the results !
krumly - 15-2-2011 at 08:28 AM
Feyd-
What do you think about using a 2:1 pulley bar as on older Xbows and Slingy turbos? And long bar to boot? I may set one of mine up with a longer
depower line and just see if it gives me the depower throw + the ability to yard in the tips. Bar pessure will go up, of course. Maybe that 2:1
could be rigged at the wing tips? Sort of like VPC, but I don't think I want the front tow point moving back when I haul in the rears. Mmmm...
I got a Guerilla 1 13m to set up next. The cool thing is I have two of each kite, so I can keep one stock to compare to. Maybe if I get it working
a stack is next. All amusing, but it takes away from time on the skis. Temps in the 40's here - lake tops are turning to slush. Need to break out
the paddle jacket and pants!
krumly
krumly
zero gee - 15-2-2011 at 02:18 PM
Way back in the time of the S/F-arc's, use of big bars (~30") was more common for big kites (even on LEI's). Personally, I used a homemade 28" bar (no
pullies) with my 1120. I wasn't doing handle passes so it was not a big deal. The longer bar provided more leverage on the steering and barload.
Lighter, faster steering.