Date: Fri, 12 May 1995 14:07:51 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: Kitesailing I've only just gotten access to the 'net, and I'm running in 10 different directions. I'm still wading through ALL the rec.kite archives. I'm looking for kitesailing folk, particularly those interested in high speed sailing or willing to help and/or critique speedsailing issues. First, a little background, since I'm new here. I'm a speed sailor first, a kite flyer second. Since 1978, I've designed and built high speed sailboats pulled by kites. From 1978-84, I designed for Keith Stewart of Melbury Osmond, Dorset. We built three 30' proas and several smaller boats and pulled them all over the south of England with a series of kites he invented and tried to market (I'll post more about Keith, if asked). After Keith went out of business, I moved to Flexifoils and have designed and built exclusively for those kites in California since 1986. I've built proas, planing catamarans, water skis and hydrofoils. My top speeds to date are a little over 30kts, though I'm looking for far higher--the world record is close to 50kts. I already know Cory Roessler, Giles Durand, Lee Sedgwick and the Legainoux brothers, though not what they've been doing lately, except Cory. I briefly published the "Kitesailing International" newsletter in 1988-89. I'm not a buggier, but a "wet" water purist. My interest is speed, pure and simple. Of course this means I want to talk about controls, efficiency, drag reduction (especially in the flying lines), hull configurations and efficiencies, and anything else that interests you. My kites of choice are Flexifoils; I've got hundreds of flying hours with them in big stacks over 10 years. I've read the "flexifoil" compendium of rec.kite posts in the rec.kite archives (posts only through 11/93 or so) and would love to compare/contrast Flexis to other power kites with *anybody* who'll post back to me. In addition, can anybody post, either here or to my e-mail address (daveculp@bdt.com) additional articles, e-mail addresses, home pages, or other resources; on or off the net, kite related or not, which might help? Thanks! Dave Culp daveculp@bdt.com = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 15 May 1995 11:17:45 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Kitesailing daveculp@bdt.com (Dave Culp) writes: >In addition, can anybody post, either here or to my e-mail address >(daveculp@bdt.com) additional articles, e-mail addresses, home pages, or >other resources; on or off the net, kite related or not, which might >help? Thanks! You should: 1) Read "Buggies Boats & Peels" By Peter Lynn. Available at www.kfs.org or hawaii. 2) Fly Peels. Whether you choose them or not, there is a *big* hole in your experience without them. 3) Get a set of Lynn Dead-man hangles. Learn how to use them with boat-hooks. 4) Forget about proas. There are 2 fundamental flaws: - You can't control it to keep it in the water against the range of pull generated by a kite. (At least, not without control systems that make fly-by-wire look easy...) - You get better lift to drag from the water than you do from the air - it is simply more efficient to use the water to keep you afloat! 5) Try a Lynn Kite sailer and kite surfer. Note however, that portability is part of the spec... 6) Join AYRS and visit Weymouth for the Speedweek... That's all I can think of for now... Andrew -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this->| Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome/index.html = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 18 May 1995 16:03:31 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: re: Kitesailing >1) Read "Buggies Boats & Peels" By Peter Lynn. Available at www.kfs.org > or hawaii. >2) Fly Peels. Whether you choose them or not, there is a *big* hole in > your experience without them. >3) Get a set of Lynn Dead-man hangles. Learn how to use them with boat-hooks. >4) Forget about proas. There are 2 fundamental flaws: > - You can't control it to keep it in the water against the range of pull > generated by a kite. (At least, not without control systems that make > fly-by-wire look easy...) > - You get better lift to drag from the water than you do from the air - it > is simply more efficient to use the water to keep you afloat! >5) Try a Lynn Kite sailer and kite surfer. Note however, that portability is > part of the spec... >6) Join AYRS and visit Weymouth for the Speedweek... 1) Read it; great work, but woefully incomplete on anything but Lynn-designed buggys and kites 2) Would love to. Am told by *serious* aerodynamicists who have flown them that efficiency doesn't rival Flexis; plus absolute speed too slow for serious speed sailing work. Anybody in SF Bay area who can show me differently? (Maybe a trial flight??) 3) Like the idea of deadman releases. Serious speedsailing requires line tensions >3-400 lbs--too much for human body. 4) I suspect you're confusing proas (half-trimarans) with hydrofoils (boats that fly on underwater wings). I agree with you, re: hydrofoils. Fellow named Greg Ketterman makes them with mechanical, active surface sensing controls which could handle the pull variation, but they're fragile. On proas, I've gotten air a time or two, but it's more a matter of control, and of knowing the beast... I've spent many hours at boat speeds above 25 kts, and in real winds above 30kts, and kept "stuck" to water. 5) Can someone please post specs (maybe send me a picture or drawing??) Please also e-mail me, my local server dumps this newsgroup every 72 hours, and I sometimes cannot log-on that frequently. 6) Been there. '78 (took second), '80,'86,'87 (took a second and a first), &'88 (assisted Cory Roeseler take first) Each time sailed in boats powered by kites. I've been a member of AYRS (Amateur Yacht Research Society) since 1978. Does anybody know AYRS members who are on-line? Can you publish (or at least e-mail to me) their e-addresses? Thanks a bunch! Dave Culp daveculp@bdt.com = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 18 May 1995 20:40:10 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Kitesailing daveculp@bdt.com (Dave Culp) writes: >[lote of "Been there, done that..." deleted, I just *knew* this guy was more than the usual "gee... wouldn't it be goot to tie a kite to a boat"] >>2) Fly Peels. Whether you choose them or not, there is a *big* hole in >> your experience without them. >2) Would love to. Am told by *serious* aerodynamicists who have flown them >that efficiency doesn't rival Flexis; plus absolute speed too slow for >serious speed sailing work. Anybody in SF Bay area who can show me >differently? (Maybe a trial flight??) Agreed. Flexies have a better lift-to-drag than just about any other kite. Also the top absolute speed on the planet. This will, no-doubt, earn them the top straight-line speed record for buggies and boats. The Peels address more real-world issues like being able to deliver useable power acreoss the entire window for better all-round performance. >3) Like the idea of deadman releases. Serious speedsailing requires line >tensions >3-400 lbs--too much for human body. Agreed. If I recall correctly, they can handle 2000kg (limited by how much kevlar you can stuff through the hole) :-) >4) I suspect you're confusing proas (half-trimarans) with hydrofoils >(boats that fly on underwater wings). I agree with you, re: hydrofoils. >Fellow named Greg Ketterman makes them with mechanical, active surface >sensing controls which could handle the pull variation, but they're >fragile. On proas, I've gotten air a time or two, but it's more a matter >of control, and of knowing the beast... I've spent many hours at boat >speeds above 25 kts, and in real winds above 30kts, and kept "stuck" to >water. I withdraw my statement. Please tell us more about your working proa. Start from a clean sheet of paper... >5) Can someone please post specs (maybe send me a picture or drawing??) >Please also e-mail me, my local server dumps this newsgroup every 72 >hours, and I sometimes cannot log-on that frequently. >6) Been there. '78 (took second), '80,'86,'87 (took a second and a first), >&'88 (assisted Cory Roeseler take first) Each time sailed in boats powered >by kites. > >I've been a member of AYRS (Amateur Yacht Research Society) since 1978. >Does anybody know AYRS members who are on-line? Can you publish (or at >least e-mail to me) their e-addresses? > >Thanks a bunch! > >Dave Culp >daveculp@bdt.com >5) Can someone please post specs (maybe send me a picture or drawing??) Nop - would you mind if I scan the pictures from SKII? (are you reading this Nop?) >I've been a member of AYRS (Amateur Yacht Research Society) since 1978. >Does anybody know AYRS members who are on-line? Can you publish (or at >least e-mail to me) their e-addresses? Simon Fishwick (AYRS newsletter): 100341.3637@compuserve.com -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this->| Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome/index.html = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sat, 20 May 1995 18:20:30 -1000 From: ahclem0013@aol.com (AhClem0013) Message-Id: <3pmf2e$g9f@newsbf02.news.aol.com> Organization: America Online, Inc. (1-800-827-6364) Subject: Re: Kitesailing Hey Dave, welcome to rec.kites, nice to have someone with your experience with us. I was wondering tho, if you like speed, and you like wind, why haven't you tried buggy's? There are some wonderful places near you that Andrew and i both know, you can get going pretty fast. Buggy's of course, are nothing more than sailing on land, and speed is something i crave. My choice of kites is peel and i have passed stacks of flexi's with them so they are not slow. There are a number of places where you can go in southern California to go very fast. Check it out. aoxmoxoa dean jordan = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 21 May 1995 13:52:18 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: Re: Kitesailing dean jordan writes: > if you like speed, and you like wind, why > haven't you tried buggy's? There are some wonderful places near you that > Andrew and i both know, you can get going pretty fast. Buggy's of course, > are nothing more than sailing on land, and speed is something i crave. A good idea, but if I just want speed, I can hop into my Oldsmobile and zip around the freeways; for a real thrill, I can open the sunroof... Sorry, I'm not knocking buggying. It's great fun and I use it to test control systems. But for me, the problem is, well, it's that almost everyone CAN do it. Sailing on water is ridiculously easy. Sailing fast, I mean *really* fast, in any kind of sailboat, is sublimely difficult. The forces and resistances are not fully understood. Adding kites to the mix just gives it that extra spice... Think sailing is a science? Just ask Dennis Connors, the only American ever to lose the America's Cup, and the only human to lose twice. More money is spent in this venue, just trying to understand and command basic sailing science, than some countries' gross national product. Consider this; the 3 fastest sailboats on the planet, at *50* miles per hour, are all within 20f each other in speed. Yet, each is FUNDAMENTALLY different from the others. They are orders of magnitude different in size, they use totally different sail systems, and totally diffeent hull support schemes. And Cory Roeseler, on kite powered water skis, thinks he can beat all 3. And I believe him! Kites give a sailboat several mega-advantages (and seveal disadvantages as well), which may, and may not let them break world sailing records. Yeah, kitesailing is more trouble, but I think the thrills are worth it. Dave Culp = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 21 May 1995 20:09:31 -1000 From: andrew@tug.com (Superuser) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Kitesailing ahclem0013@aol.com (AhClem0013) writes: >My choice of kites is peel and i have passed stacks of flexi's with them so >they are not slow. Both you and I know that Peels generaly waltz all over everything else (*) in track and play, but note that Dave is after maximum top speed and nothing else. All the rules change: - Acceleration doesn't matter any more. Dave will happily take a 10-mile run-up to build up the speed if it means that he'll have the optimum configuration when he gets there. - Lift-to-drag is of vital importance. Flexies have about the best L/D going. The Peel profile is a compromise to provide better edge-pull, to avoid luffing etc. Those 100 bridle-lines cost drag! - Absolute speed. You can't go faster than the kite. Flexies are the fastest kite on the planet. - Course. Generally when you pass another buggier, you are both going in the same direction. Dave will carefuly tune his direction for maximum speed. Note that he'll probably use the smallest kite that he can manage to get moving with... Andrew -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this->| Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome/index.html = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 22 May 1995 13:42:31 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: Re: Kitesailing > Both you and I know that Peels generaly waltz all over everything else (*) in > track and play, but note that Dave is after maximum top speed and nothing else. > All the rules change: > - Acceleration doesn't matter any more. Dave will happily take a 10-mile > run-up to build up the speed if it means that he'll have the optimum > configuration when he gets there. > - Lift-to-drag is of vital importance. Flexies have about the best L/D going. > The Peel profile is a compromise to provide better edge-pull, to avoid > luffing etc. Those 100 bridle-lines cost drag! > - Absolute speed. You can't go faster than the kite. Flexies are the fastest > kite on the planet. > - Course. Generally when you pass another buggier, you are both going in > the same direction. Dave will carefuly tune his direction for maximum > speed. > > Note that he'll probably use the smallest kite that he can manage to get moving > with... I just don't understand where the notion that Flexis can't accelerate a vehicle comes from. I routinely get up to full speed within 20-30 FEET of where I start. Often the acceleration pulls the boat out from under me! The Flexis, on launch, pull mightily of course. On course change, I bring them overhead, (which dumps their power and doesn't overturn the boat) and then dive them down, or over onto their new tack; LOTS of power. Don't you guys remember that kite jumping (not that I condone it) BEGAN with Flexifoils? (Jon Waters then started using parachutes, and waxed everybody...) And, yes, I do want "the smallest kite" but that usually works out to be every bit I can manage statically, and a damn site more than I can manage in a full power dive. I wish I were a competitive buggier. Or at least had seen enough buggying to know whether a skilled Flexi flyer (skilled at flying one for speed and power, I mean) could really make a buggy fly. Cory Roeseler would debate you on "fast enough" kites. He argues that he's DONE 50 mph with his Kiteski kite (16'Banshee). I dunno... More later when I can sit down and write Dave Culp = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 23 May 1995 07:45:25 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: Re: Kitesailing In article , andrew@tug.com (Andrew Beattie) wrote: > I withdraw my statement. Please tell us more about your working proa. > Start from a clean sheet of paper... A tall order, but I'm game. Please forgive the long post... Kites have 3 main advantages over conventional sails for boats. Two of these aren't fully realized with buggy-type hand held kites, nor with Peels. The first is the fact that winds above the ground are both smoother and flow at higher velocities than at the surface. Wind at 75 ft altitude may be blowing as much as 25arder than at 10 ft. Since energy derived from wind varies as the square of its velocity, up to 70more energy is available at altitude. The second has to do with relative velocity of the boat and kite. With conventional sailboats, and with most "static" kites, the rig does not move, relative to the hull. This is obvious with conventional boats (the rig is bolted on!), with Peels and others, I'm referring to the idea of "fixing" the kite's position in the sky. A big advantage comes when you move the kite. If a kite is flown in a figure 8, or zig-zag course, it is working in MUCH higher velocity air, and thus can generate MUCH more power, per unit area, than conventional sails or "static" kites. For instance, if a dynamic kite moves at a velocity twice that of the boat, the wind energy available to it will be 4 times that available with static kites. All things being equal (of course, things never are), such a boat would need only 25as much sail area. This is the reason that Flexifoil powered boats *always* fly in a figure 8 or zig-zag pattern. Flexis like to fly at about 3-3.5 times the wind speed. If they're kept in this regime, they pull very hard *always*. Since even the fastest boats sail at 1.5-2.5 times the wind speed, the kites are always zig-zagged. A slower kite should also be zig zagged at its fastest speed, only settling down to a "static" pattern as the boat (or buggy) attains the same speed as the kite's fastest. (Flexifoils, and other kites, lose power in turns. The trick is to make snap turns, with long straights between the turns -- actually the REAL trick is to keep a good rhythm going, without too much surging and slacking) OK so far? The third advantage is anti-heeling. This is easy to grasp, but seems to go against some established buggy safety rules. It requires tying the kite to the boat (or buggy). ALWAYS USE A DEADMAN RELEASE! Not a "quick pull and it's untied" release, but a **DEADMAN** release. If you depart the vehicle, so do the kites. Anything less is suicide (and maybe aggravated assault...). Any sailing vehicle has a center of lateral pressure (CLP). This is that point, say along the rail, where pulling the boat sideways results in the the boat *going* sideways, not skittering forward or back. Predictably, if you move the attachment point forward or back from the CLP, the boat will, after turning slightly, move either forward or back. CLP is not a one or two dimensional concept, but a point in space. Thus it has a position athwartships, usually on the centerline of the boat, and a position vertically, usually some distance below the surface of the water. By definition, if a boat's hull is symmetrical and its keel or daggerboard is vertical, the sideforce generated by its underbody acts through its CLP and is parallel to the water's surface. In a conventional boat, the force generated by the sails is also parallel to the water's surface, but at some distance above that surface. It is these opposing but offset forces which causes a sailboat to tip, or heel, and also which causes it to move at all. For several thousand years it was thought that you needed the one (heeling) to get the other (forward drive). We're going to change all that. With kites, the driving (traction) force is, of course, along the kite lines. This is not parallel to the water surface. If one takes the kite attachment point and lowers it, say to the deck, the heeling moment is reduced. If one raises it, say to the flyer's arms and hands, the heeling moment is increased (perhaps the reader has experienced this). If the attachment point is both lowered and moved out towards the leeward (downwind) rail, the kites' "line of force" can be made to coincide with the boat's underwater CLP and there will be no overturning moment -- the boat will not heel. If there is no heel, there needs be no ballast, no excessive beam (width), no "hiking out" of the sailor -- no limits to the amount of power the boat can carry. Of course, in real life, kites aren't "sky hooks" with constant line angles and pull. As the kite flies higher and lower, the geometry of kite "line of force" and CLP changes, and the boat will heel. (Interestingly, it often heels to windward, as the kite goes too high and the "line of force" crosses below the boat's CLP.) This effect can either be designed for and dealt with, or minimized, for instance by having the kite line attached very close to the boat's actual CLP. One could lead the kite line underwater and attach it to the boat's daggerboard. One could even build a man-carrying kite with a line down to a small "underwater kite." (It's been done.) Another approach - mine - is to build a proa -- that's a boat with one long hull and one short one. It's symmetrical longitudinally and thus is able to sail in either direction. The pilot sits on the larger hull and the daggerboard is under him. The kite is attached to the short hull, near the center and down near the outside waterline. The pilot sits "sideways," facing the short hull and the kites. From the pilot's perspective, the boats always sails "left" or "right," not forward and back. The short hull is always downwind, the long one always upwind. Under sail, the short hull is sometimes in the water, and sometimes flying in the air. Sometimes I am sitting upright and sometimes I am laying on my back (the large hull is designed for this). The boat doesn't fly out of the water (usually, usually...) since the daggerboard is always at right angles to the kite lines' pull and sometimes pulls somewhat downwards. In all my proas to date, I use no rudder. I take the kite attachment point to a longitudinal track on the outside of the short hull. Running the attachment point along this track gives me forward, stop and backwards; the distance along the track gives me the actual angle of the boat's heading, always relative to the kite's position in the sky (this may have been a patentable concept, and works particularly well with "static" kites. It's been much published and thus now is in the public domain) "Fine" steering, like around other boats, consists of steering the kites and the boat follows -- pretty hairy with Flexifoils and I'm not recommending it for everyone. Let's just say nobody got hurt... A better system would be 2 daggerboards (2 rudders?), one near each end of the boat. These would be geared together and counter-rotating. The kite would attach at a fixed point on the leeward rail. Only a very small amount of rotation of the daggerboards results in large shifts of the boat's CLP, with the same steering effect. (This is also, I think, patentable. I publish it here for the first time and bequeath it to the public domain -- I hate patents, they stifle development -- just please, if you use the scheme, don't claim to have invented it.) So there, you pretty much have it. Kitesailing-in-a-box. I moved away from proas for outright speed when I determined that sailing much above 30 kts requires a planing hull (like a speedboat or water ski). Not, though, before building a proa which could plane in either direction and entering it at Weymouth Speedweek I next built a planing catamaran (wild control problems, but VERY fast) and am now working on a monohull (planing dinghy). I keep coming back to proas, though. They're simple to build, foolproof to operate. And *much* faster than your friends' Hobbiecat. I would love to design a new proa for somebody, if anyone's serious about it. Not, alas, for free, but I'm remarkably cheap... All for now, Dave Culp = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 23 May 1995 10:34:48 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Kitesailing daveculp@bdt.com (Dave Culp) writes: >I just don't understand where the notion that Flexis can't accelerate a >vehicle comes from. I routinely get up to full speed within 20-30 FEET of >where I start. Often the acceleration pulls the boat out from under me! Hmmm... Maybe I implied that, but it weasn't what I was intending to drive at... (note: I said earlier something to the effect that flexies have the potential to be the best power source for out-right speed, which is Dave's target. I still stand by that...) The big difference between a Peel an a Flexi (or flexi-stack) is the way in which the power is delivered. Even a big flexi-stack delivers very little useful pull at the edge of the window, but as you fly it through the window, it will accellerate very quickly to provide massive pull in the middle. There's nothing like a bunch of flexies for pulling you clean out of the buggy... Things only realy start cooking when you are going fast enough that instead of sweeping the kite through the sky to generate apparent wind, the movement of the vehicle (and therefore kite) is generating plenty of apparent wind by it'sself. Everything sort of settles into a steady state, with the kite in a fixed position against the sky, with things getting faster and faster... until you can't pull hard enough to make the kite go any faster. In this maxed-out position, the kite way be at the edge of it's avaiable window (because of the apparent wind, the window whifts to your rear as you go faster...), but the apparent wind available to it is similar to that which gives it such a kick when it is the middle of the window in stationary flying. Thus at maximum speed, you are handling maximum power. Where this is all leading is that you want something small enough that you can handle it's maximum power. While Flexi's have the best L/D and highest top speed, (so at the end of the day you won't be able to beat them), The Peel is compromised to provide *much* more power at the edge, and a wider circle of power in the middle. This means that with a Peel, you can make decent progress from a standing start, just by hanging the kite at the edge of the window and steering up-wind of it enough to provide tension on the lines, just letting the kite fall further and further back as you get faster Cand faster (in fact, the kite just hangs at the edge of the apparent-wind window as this falls further behind you). This is a fruitless excercise with flexies... I seem to be rambling. Let me try to pull it together. To hit max speed, you want a small kite. At low speed, this will only provide decent power in the power-band in the middle of the window. For the flexi, this is a small area, for a Peel, it's a big area. Therefore a Peel small enough to be the right size at the max will do a better job of getting you up to that speed in the first place. But there is an important distinction I've been glossing over... Most of my experience (and all of my max-out experience) has been on land, where you have a severe limit to the amount of power that you can handle. On the water, you have *much* more bite against the kite. Maybe on the water, *all* of what I've been saying is a waste of time. *sigh* Andrew -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this->| Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome/index.html = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Wed, 24 May 1995 09:47:57 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Kitesailing daveculp@bdt.com (Dave Culp) writes: >(thanks for a good post...) > >Kites have 3 main advantages over conventional sails for boats. > >The first is the fact that winds above the ground are (better) > >The second has to do with relative velocity of the boat and kite. Here you imply that this may give top speed (your main concern), but for the rest of us, we can have fun because we can hit max power at zero speed. Breaking records is impressive, but acceleration is fun! Although I've never managed in the water anything like the sharp decelerate, turn and accelerate that I've done on land... >OK so far? The third advantage is anti-heeling. Agreed. Big win! BTW: I want a dead-man release that allows me to fly a *loop* of line. >A better system would be 2 daggerboards (2 rudders?), one near each end of >the boat. These would be geared together and counter-rotating. Funny that, I've been toying with much the same idea, I was thinking of a plaining cat with 4 rudders... For me, Kite sailing has another big attraction: The simple fact that it is sailing using a *kite* for power, but then, maybe I'm a little odd... Andrew -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this->| Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome/index.html = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Wed, 24 May 1995 12:29:40 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: Re: Kitesailing In article , andrew@tug.com (Andrew Beattie) wrote: > daveculp@bdt.com (Dave Culp) writes: > >I just don't understand where the notion that Flexis can't accelerate a > >vehicle comes from. I routinely get up to full speed within 20-30 FEET of > >where I start. Often the acceleration pulls the boat out from under me! > > Hmmm... Maybe I implied that, but it weasn't what I was intending to > drive at... Actually, you were quoting Peter Lynn, I expect. He says it specifically, I believe you did also, and I hear it everywhere I go, so one of you must be widely read... ;-) > The big difference between a Peel an a Flexi (or flexi-stack) is the > way in which the power is delivered. Even a big flexi-stack > delivers very little useful pull at the edge of the window I disagree. I guess I'm going to have to hook up with Cory Jensen in Monterey and do some team flying with Flexis against peels; I just don't believe what I hear, and am left thinking that you guys aren't flying your Flexis to their best advantage. > Things only realy start cooking when you are going fast enough that > instead of sweeping the kite through the sky to generate apparent wind, > the movement of the vehicle (and therefore kite) is generating plenty > of apparent wind by it'sself. Everything sort of settles into a > steady state, with the kite in a fixed position against the sky, with > things getting faster and faster... Here's where things start getting wonky. I agree with you in theory, and it is certainly true of any other kite, and it certainly FEELS right when sailing Flexis, but... Unless you are sailing/buggying at THREE TIMES the windspeed, the flexi isn't sailing at its potential. It has hit its real edge, where indeed pull drops off. What is NOT obvious is that once you settle into this steady state, you can STILL zig zag the kite! (It WANTS to fly at 3-3.5 times windspeed; anything less and its power drops off) It won't drop back, it just delivers more power, giving you a bit more speed... then a bit more... and so on. This is the real trick of power flying; as long as you can handle more power (forever with the proas), keep those kites flapping. If you're over-powered, just hold them steady, at their edge, and you spill off a bit (or a lot) of power >Where this is all leading is that > you want something small enough that you can handle it's maximum power. Agreed. This is a very real problem in high speed sailing. Not only don't you want the power at high speed, you also don't want the drag of the oversized rig. At really high speed, drag is the culprit. The less drag, the higher the Velocity (sub) boat/Velocity (sub) windspeed ratio you can achieve, and the higher top speed. (Understand that all speedsailing is done at boatspeeds higher than the windspeed. There's always a limit of what kind of waves a boat can handle; thus the boat able to sail the highest percentage of windspeed will sail the outright fastest) (as an aside, someone asked whether the proas can handle anything other than flat water. I often practice in an area which generates 2-3 ft waves -- really vicious short stuff. You can sail in it, but not at record speeds. In any chop at all, though, I can sail faster than my support boat dares power through...) > The Peel is compromised to > provide *much* more power at the edge, and a wider circle of power in the > middle. > with flexies... I worry about the inability of depowering big peels in big winds. If, as you say, peels are capable of the pulls I get with Flexis, *I'D* be afraid of them! With flexis, I always know I can fly them out of their window, and quiet them down...> >Let me try to pull it together. To hit max > speed, you want a small kite. At low speed, this will only provide > decent power in the power-band in the middle of the window. For the > flexi, this is a small area, for a Peel, it's a big area. Therefore > a Peel small enough to be the right size at the max will do a better > job of getting you up to that speed in the first place. Your first couple of statements are dead on. But, once again, I disagree with your "therefore." I contend that I can get more power from, and less power from a given size stack of flexis than with the requisite peel, on either end of the speed spectrum. I can fly them faster when going slow (and thus get more power/unit area -- by far -- than the peel). I can then de-power them, by flying the edge/zig-zag trick mentioned above, at high speed, and end up with the lesser, manageable power I want. Actually, to date, I can't sail more than about 1.75 times the windspeed, so I'm always calling for more power, unless something goes wrong... I'm not sure I can defend my position without first-hand peel experience, tho, so I'll wait until I have it. >Maybe on > the water, *all* of what I've been saying is a waste of time. Nah, I don't think so. There's a lot of carry-over. I expect to learn more >From you than to teach TO you ;-) Dave Culp = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 25 May 1995 06:30:37 -1000 From: travell@comics.enet.dec.com (I want to Go Fly a Kite!) Message-Id: <9505251530.AA03499@vbormc.vbo.dec.com> Organization: Harvard University Office of Information Technology Subject: Re: Kitesailing Andrew Beattie writes... > For me, Kite sailing has another big attraction: The simple fact that > it is sailing using a *kite* for power, but then, maybe I'm a little odd... Only a `little' odd ?? :-) If it is a problem at all, the only `problem' with Andrew is that he has more enthusiasm in him than the combined total of any three other people I know! More power to his kite.... John Travell. Solent Kite Flyers is a NEW Kite club based around Southampton, UK, Contact me by Email "travell@comics.enet.dec.com" for further info. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Wed, 24 May 1995 15:45:48 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: Re: Kitesailing >From Andrew: > Here you imply that this may give top speed (your main concern), but > for the rest of us, we can have fun because we can hit max power at > zero speed. Breaking records is impressive, but acceleration is fun! > Although I've never managed in the water anything like the sharp > decelerate, turn and accelerate that I've done on land... Yes, yes. With the proas, it's a simple matter to reverse the kites, do a screaming low pass, let the track slam over and you're off (or at least, the boat is) in the other direction. I have *never* experienced faster decel- or acceleration. Not even on a motorcycle. I suspect the G force exceeds 1.0 > For me, Kite sailing has another big attraction: The simple fact that > it is sailing using a *kite* for power, but then, maybe I'm a little odd... Just between you, me, and 30 million netsurfers... that's the reason I started, and that's the reason I've persisted. Go scare yourself! Dave = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 25 May 1995 09:51:29 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Kitesailing daveculp@bdt.com (Dave Culp) writes: >andrew@tug.com writes: >> daveculp@bdt.com (Dave Culp) writes: >> >I just don't understand where the notion that Flexis can't accelerate a >> >vehicle comes from. >> Hmmm... Maybe I implied that, but it weasn't what I was intending to >> drive at... >Actually, you were quoting Peter Lynn Hmmm... I've personaly seen Peter Lynn *severely* over-accelerated by flexies >> The big difference between a Peel an a Flexi (or flexi-stack) is the >> way in which the power is delivered. Even a big flexi-stack >> delivers very little useful pull at the edge of the window > >I disagree. I guess I'm going to have to hook up with Cory Jensen in >Monterey and do some team flying with Flexis against peels; Yeah. That's the attitude. Talk is cheap. We need to settle this properly. It's time to take a step outside... :-) Corey isn't a Peel flier, but he should be able to point you to a good one... BTW, a little background you should know about me: I started with 10' flexies and put in a fair amount of time on my stack of 6 of them before I moved to Peels. I sold the flexies when I realised that I wasn't flying them at all... >I worry about the inability of depowering big peels in big winds. If, as >you say, peels are capable of the pulls I get with Flexis, *I'D* be afraid >of them! With flexis, I always know I can fly them out of their window, >and quiet them down...> Yep. I often fly bigger kites than those around me, on land, I'll move smaller if it's too big for me to hold my ground. At sea, I'll handle more than that (if someone would kindly help hold me near the boat as I get in...) Doing a 300' body-surf as you cope with the launch is kinda fun... >Your first couple of statements are dead on. But, once again, I disagree >with your "therefore." Again we need to get onto the water. Your arguments are sensible, but I think that we are both at a disadvantage to see this to a decent conclusion without side-by-side experience. - I need to get experience on *water* with Flexies (particularly in strong wind on long lines) - You need to get experience with Peels (and there is a lot to learn about handling a Peel...) Where in the world are you? (I'm about 1 hour West of London...) Andrew -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this->| Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome/index.html Spam-posters brain required for research. $5/lb guaranteed by return post. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Fri, 26 May 1995 07:13:24 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: Re: Kitesailing In article , andrew@tug.com (Andrew Beattie) wrote: > Where in the world are you? (I'm about 1 hour West of London...) > > Andrew > -- I'm about half an hour East of San Francisco. That makes us almost neighbors, doesn't it? (I think about 5800 statute miles, via great circle route...) I've flown quite a bit in England, though. 1978 near Gravesend and near Swindon. 1978 and 1980 at Melbury Osmond, Dorset and at Weymouth. And of course all those times at Weymouth. Have you ever flown with Andrew Jones, co-inventor of Flexifoils? He lives in Newmarket, near Cambridge. Andrew's not a kite fanatic, but as you might expect, he knows a *lot* about Flexis. I've got his address and phone # here somewhere, but I'd have to check with him before posting it. Dave Culp daveculp@bdt.com = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Fri, 26 May 1995 13:03:30 -1000 From: nop@euronet.nl (Nop_Velthuizen) Message-Id: Organization: Euronet Internet Subject: Re: Kitesailing >Have you ever flown with Andrew Jones, co-inventor of Flexifoils? He lives >in Newmarket, near Cambridge. Andrew's not a kite fanatic, but as you >might expect, he knows a *lot* about Flexis. I've got his address and >phone # here somewhere, but I'd have to check with him before posting it. Considering some comparison in kite-boat-speed it is interesting to know that there is a yearly kite-boat regatta on the mediteranian-sea near Rome (Italy). The last two years ALL boats are the Peter-Lynn Trimaran type but there is more variation in kites. Mainly Peels, I flew my Sputnik last year, and the Flexifoil company (Joost Meierink, Andrew Jones does not normally come to these events)) fly's Pro-Speed 6+ Flexis. In all the matches that were held there was not a single time that a Flexifoil powered boat could keep up with a Peel/Sputnik powered boat. I think Flexifoil performance would greatly improve if the larger wingspan kites like 8ft ot 10 ft where used but up to now they have not which is a pitty. Larger Flexi's would require more control input so the arms of most kite-flyers would be too short. I have the same problem with the 10 mtr Sputnik but solved it by using a loop type control system combined with a harnass. It is even possible to hold a steady course with the line just in one hand! The same system should be fine for large flexi's. Don't worry mr Beattie, it does incorporate a Dead-Man release as well !! So it is safe to use!! The release system is still in prototype stage but should be available soon (next month I hope) MAZZEL NOP = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sat, 27 May 1995 12:45:59 -1000 From: nop@euronet.nl (Nop_Velthuizen) Message-Id: Organization: Euronet Internet Subject: Re: Kitesailing >Yes, Yes, Yes! We *need* a dead-man release for loop flying. You *must* >bring some of these to Fano. Please write my name on one of them... I am sorry, don't have time to be there. >I have pestered Peter to manufacture such a device in the past, but whilst >he agrees, he didn't actualy make one... It is a little difficult to show >you a detailed design in Ascii, but here is the general outline of what I >have in mind... >>>Here I cut a very complicated explanation.<<< No Andrew, luckely it is much simpler than that. Keep you posted, MAZZEL NOP = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sat, 27 May 1995 00:39:20 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Kitesailing nop@euronet.nl (Nop_Velthuizen) writes: >It is even possible to hold a steady course with the line just in >one hand! The same system should be fine for large flexi's. Don't worry mr >Beattie, it does incorporate a Dead-Man release as well !! So it is safe to >use!! Yes, Yes, Yes! We *need* a dead-man release for loop flying. You *must* bring some of these to Fano. Please write my name on one of them... I have pestered Peter to manufacture such a device in the past, but whilst he agrees, he didn't actualy make one... It is a little difficult to show you a detailed design in Ascii, but here is the general outline of what I have in mind... Consider a bar, which is strong enough to withstand the pull of the kite. One side of the bar is fixed to the boat by a hinge, to allow it to swing. The other end of the bar is held by a device similar to bicycle brake calliper. The line-loop is passed under the bar, which is held firm provided that the brake is applied. This allows the dead-man release (which would be a bicycle brake lever in the first prototype...) to be completely remote from the line. Note that the dead-man release (or would you prefer "death detector"?) can be switched from hand to hand as convenient. Further improvements would include: careful design (perhaps also spring-loading) of the bar mechanism, so that it can be set up simply by pushing the rope against the bar (as easily as attatching a rope to a carabinier) Redisign of the death-detector, so that it is small and fits comfortably in your hand. It would be nice if you could grip it wetween your teeth when your hands were full... Andrew -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this->| Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome/index.html Spam-posters brain required for research. $5/lb guaranteed by return post. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 28 May 1995 09:47:13 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: Re: Kitesailing In article , nop@euronet.nl (Nop_Velthuizen) wrote: > I think Flexifoil performance would greatly improve if the larger wingspan > kites like 8ft ot 10 ft where used but up to now they have not which is a > pitty. > > Larger Flexi's would require more control input so the arms of most > kite-flyers would be too short. I have the same problem with the 10 mtr > Sputnik but solved it by using a loop type control system combined with a > harnass. It is even possible to hold a steady course with the line just in > one hand! The same system should be fine for large flexi's. Don't worry mr > Beattie, it does incorporate a Dead-Man release as well !! So it is safe to > use!! > I have never used 6' flexis. My "standard" rig is 5-8 10' flexis. I fly them from a 4.5' control bar. I have tried up to 9 12' (special order) flexis in a stack (light winds!), and more commonly 3-4 12' flexis, but I find that 12 footers won't accept stack geometry very well (the kites in the stack "hunt", no matter what the stack spacing.) Also, the 12 ers won't turn as fast as 10 ers (even with very long control bars and thus large line differentials), so average power is very much less than with equivalent area in 10 ft kites. Since Flexis must always be zig-zagged when sailed for max power, loop-type control systems, or one handed flying aren't practical, except for very short (<2 seconds) time periods. I'm nearly finished with "Stunt Kites II" (received Friday nite). Fantastic book! Will comment more soon. Dave = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 28 May 1995 23:08:37 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Kitesailing I was surprised by some of your comments. Could I ask you to elaborate? (Dave Culp) writes: >I have never used 6' flexis. My "standard" rig is 5-8 10' flexis. I fly >them from a 4.5' control bar. I am surprised that you are using a control bar on a boat, I would have thought that it would be unwieldy. Please tell us more about your setup: What line-length? Is the control-bar attatched to the boat through a dead-man (I assume so...) Is the bar connected at the middle? (nasty breaking force?) The ends? (more difficult to turn?) What is the bar made of? (I guess it's nicer if it's lighter...$$$) On the proa, are you steering with your hands or feet? Does the dead-man release the bar (so it flies off to hit someone else?) Or does it release the line (so that it recoils to hit you?) >I find that 12 footers won't accept stack geometry very well (the kites in >the stack "hunt" What spacing do you use on your stack? I ended up with 4' (for my 6 10's), but found that by far the biggest factor was skill - sure it pulls like a truck, but it's sensitive like a baby...). >Since Flexis must always be zig-zagged when sailed for max power, >loop-type control systems, or one handed flying aren't practical, except >for very short (<2 seconds) time periods. Why? I want to use a loop, so that I can control a kite which regularly requires more control input than I can easily provide (I can do 32 inches with ease. I can do 56 by hooking the line under my arm, crucifix position (difficult in a vehicle, because you must step towards the kite to extend your arm away from the kite, provides 59. Have you considered using a steering multiplier? Here is a summary from a discussion between myself and Peter Ulfheden: Peter's proposal was: > K K K = Line to kite > | | A,B,C = Pulleys > | | e,f = One line running in pulley A > &Q Q& a,b = One line running in pulley B > |\ /| c,d = One line running in pulley C > | \ / | & = Knot > | \ / | H = To handles > | e\ /f | > | \ A / | > | \O/ | > |a | d| > | & | > | / \ | > | b/ \c | > | / \ | > |B / \ C| > \O/ \O/ > | | > | | > | | > H H When you provide a steering differential between H-H, the effect is multiplied (more inches difference) at K-K. Peter was very excited, but unfortunately, I had to show him the catch: > K K > |g h| > | | > & & > |\ /| > | \ / | > | \ / | > \ e\ /f | > \ \ A / | > \ \O/ | > b\ |a d| > \O& | > | \ | > | \c | > | \ | > H \ C| > B \O/ > | > | > | > DH > >Let's say that we've got 4kg pull on handle D and 0kg pull on handle B >(we're trying to pull as hard to the right as we can). Because C is a >free-running pully, the tension in line c and line d must be equal. c >is 2kg and d is 2kg. The pull on B is Zero, so b hangs slack. The pull >on a is all of c, plus half of the zero pull on B, so the tension in >a is also 2kg. The pull on A is split 50/50 between e and f, 1kg each. > >The total tension on g is e(1kg) + b(zero) = 1Kg >The total tension on h is f(1kg) + d(2kg) = 3kg > >This isn't just a limitation of Peter's implementation. It can be proven >mathematically that you can't beat it. You can't get better than this >without a *compressive* member in the system to push the "slack" side >forward. You reach the 75turning faster but you can't get past it >and believe me, you want the full 100to get a Peel out of a tip-stand. Flexies are, however, different to Peels. You are currently satisfied with 4.5' of difference. I'm pretty sure that you are not going for a 0/100 0ifference in pull on the lines. It is possible that a steering multiplier will have a practical application with flexies... Andrew -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this->| Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome/index.html Spam-posters brain required for research. $5/lb guaranteed by return post. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 30 May 1995 15:42:11 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: Re: Kitesailing In article , andrew@tug.com (Andrew Beattie) wrote: > I am surprised that you are using a control bar on a boat, I would have thought > that it would be unwieldy. Please tell us more about your setup: I use a system identical to Nop's "Power Steering" in Stunt Kites II, with the main pully attached to the boat (wherein I get anti-heeling). For those without SKII, get it! (Great book, Nop! A million thanks!) No, really, it's just the top half of Andrew's "multiplier" (How do you draw so well in ASCII?), in his last post, with pulley "A" being attached to the boat and lines "a" and "d" leading to the pilot. (By the way, Andrew, your multiplier will work if you attach pully "A" to the boat.) My flying lines are 150 ft long, plus about 15 ft for the "power stering" set-up, plus the kite train itself--I never attach kites directly to the main lines). I think they are 25 ft too long. I often use a dead-man release (at pully "A" in Andrew's drawing). When it goes, it takes everything, the pulley (quite large) and the bar. With this set-up, the bar can be quite light. I use aluminum tubing, but it can be a piect of 1.25" softwood dowell, even balsa ;-). The final control lines never have more than 50-75 pounds tension on them. I must admit that I often fly without deadman, but I always fly with a support boat to warn off leeward spectators and I never intentionally fly upwoind of *anything*. Since Flexis need cionstant attention to fly at all, I feel comfortable knowing they'll self-crash within a couple of seconds of my exiting the boat. (I know that Flexis can "helicopter," but it's hard to do, and it always progresses downwards; the only time I ever did it, the kites hit the water within 5 seconds and the boat only went ~75 ft.) I have has several unintentional dead-man releases and decided that the above is generally acceptable (plus the crew nearly mutineed--they *do not* like to re-launch stacks of wet kites.) I use a bar for several reasons; mostly to get that extra differential. The 10'ers only need 18-24 inches of differential for most flying, but in light winds, or to stop that "suicide dive," I want more differential (Flexis don't mind such "horsing around'" they just turn faster). Heck, in light winds, sometimes I'll reel the lines in hand over hand (with gloves)--I'll do *anything* to keep those buggers aloft and out of the water! The second reason I like bars is that I have to do things around the boat (I steer with my feet). I can hold the bar with one hand at times, and sometimes I can use the bar itself to reach that loose fitting... Everything done on a one-man Flexi powered boat, including looking ahead for the course, must be done in 1-2 second snatches, between turns of the kite stack (I'd really *like* to try peels... but the Flexis are so darn fast...) Others (Jacob's Ladder) claim that 2 crew is a minimum; it's certainly easier. > > >I find that 12 footers won't accept stack geometry very well (the kites in > >the stack "hunt" > What spacing do you use on your stack? I ended up with 4' (for my 6 10's), > but found that by far the biggest factor was skill - sure it pulls like a > truck, but it's sensitive like a baby...). I use 5-6 foot spacing. 6' seems to work best with the 10 footers, but 5' should give a better stack (though not in my expeience). When I go as short as 4', the stack loses power--the kites are robbing each other's wind. I'm very picky about my stack's flying geometry. I try for perfection--only the bottom kite visible to the flyer--at all times. I'm careful to use near identical kites (contiguous serial numbers if possible, certainly all purchased at the same time and in the same color--different colors, let alone graphics, have different stretch characteristics) I also want near identical spars, with all tip sections the same purchase, and the same color (color doesn't matter here; just means better likelihood that they were all from the same batch) Tip sections, but not carbon centers, go "soft" with age. The fibers actually delaminate--sometimes you can see "meat hooks" off the sides when flexed on the bench. I'm careful to "crown" the tips, then I tape them to the center section with diagonal layers of reinforced tape to prevent them rotating. I fly the kites singly when new in order to fiddle with the spar length. When it's right, I put permanent stops on the spar (not the factory rubber grommets), and then code the spar to the kite so I'll use the same each time. When a stack is "right," it is suprisingly insensitive to poor flying--sometimes the topmost kite will hunt a little, but it comes back to lock wuickly. There is a caveat: if the stack is allowed to go out of "lock" (Flexi flyers know what "locking" means--when the kites transit >From near-straight-spar "floating" flight to fully hooped "locked" flight--this is an important issue to Flexis flight aerodynamics--the s-profile isn't the only reason, by far, that the kite flys without a bridle--but I digress...), the shole stack hunts, sometimes violently, and can invert or hourglass a kite, or even break spars. I'll do this if I have to (to de-power the stack), or accidentaly (when flying beyond the kitees' window), but I try *hard* to avoid it. None of this works with the 12 ft kites. I've tried spacing from 4-12 ft to no avail. I can't get them to lock-up together. I once say Andrew Jones get a 2-stack with about 5 ft connectors, to fly near perfectly, but both Andrew and Ray eventually advised me that they couldn't do it predictably. The pull of a Flexi stack drops by about half if the kites are hunting. Cory Roeseler, in his record setting kiteskiing work, both at the Columbia River Gorge, and at Weymouth in 1987-89 was using stacks of 12'ers and was losing a tremendous amount of power through this problem. I've never had any problems flying with a bar from a boat. I've used from 4.5' up to 7' bars and no particular problems. Typically you can "cheat" and pull near the end you're trying to bring in if you need more power, and nearer the center (or even from the far end) if you want more differential in the lines. With Andrew's multiplier, you always get 1:2 multiplier, plus it's much harder to pull--actually more than twice as hard due to friction at the pulleys. Since the pulley "A" (andrew's drawiong) is fixed to the boat, and I can lean forward and back, I can easily get the whole differential available in the bar--and then some. I really *like* flying with a bar--I use it all the time on land too, unless I'm flying in a crowd. I think if I flew a lot on land, in crowds, I'd rig some kind of double dead-man like Peter Lynn's, and still fly with a bar. As a postscript, I have tried using a steering multiplier, just like Andrew's but with pully "A" fixed, in order to fly the kites with my feet, leaving hands free to run the boat. It's just too wierd. Feets gots lots of power, but no "feel" for the kites! > Why? I want to use a loop, so that I can control a kite which regularly > requires more control input than I can easily provide (I can do 32 inches > with ease. I can do 56 by hooking the line under my arm, crucifix position > (difficult in a vehicle, because you must step towards the kite to extend > your arm away from the kite, provides 59. > Work on the dead-man issue, and try a bar. You may be surprised. Strong winds, Dave = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Wed, 31 May 1995 11:06:13 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Kitesailing daveculp@bdt.com (Dave Culp) writes: >(By the way, Andrew, >your multiplier will work if you attach pully "A" to the boat.) Please don't call it "Andrew's Multiplier". Here's my view on the history of it... Once, quite some time ago, it dawned on me that a pulley system might be capable of multiplying steering effect. I puzzled and puzzled trying to work it out, but couldn't quite make it. I was sure it was possible, but I just couldn't get my brain round it... It kept me awake for ages that night... At about 2:00am, I phoned NZ and had a chat with Peter Lynn. as is typical of my conversations with Peter, he said "yes, of course, I've got 20 different schemes for doing that, here's an easy solution (as per the previous diagram), but here's the problem... (as per the previous description)". I kept quiet about it until Peter Ulfheden proposed the very same scheme to rec.kites about a year ago... If anything has my name to it, it is the act of sliding during the launch of the kite... If the length of the slide is equal to the length of the kite-line, then you've just done a "Full Andrew". If the length of the slide is less, then you need a bigger kite :-) Something I've been thinking about... On the proa, without a rudder (using the kite for steering), do you: 1) Make decent progress up-wind? 2) Weave the boat in time to the kite? (I steer downwind during the power and upwind to pull the kite through the turn) 3) Have decent control (or is it basically forward/reverse and you go wherever the kite wants to take you...) Andrew -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this->| Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome/index.html Spam-posters brain required for research. $5/lb guaranteed by return post. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 1 Jun 1995 08:35:06 -1000 From: daveculp@bdt.com (Dave Culp) Message-Id: Organization: Beckemeyer Development, Oakland CA Subject: Re: Kitesailing In article , andrew@tug.com (Andrew Beattie) wrote: > Something I've been thinking about... On the proa, without a rudder (using the > kite for steering), do you: > > 1) Make decent progress up-wind? > 2) Weave the boat in time to the kite? (I steer downwind during the power > and upwind to pull the kite through the turn) > 3) Have decent control (or is it basically forward/reverse and you go wherever > the kite wants to take you...) Yes, upwind courses are as good (or better, since the boat is always balanced and there's no drag from the rudder) as any other scheme. Yes, I do weave the boat as you suggest. Actualy, I've gotten away from rudderless boats; they're dangerous in crowded waters. I have found, though, that weaving is still the best way to go, if using Flexis and zig-zag flying (BTW; I hate that term; prefer "dynamic sheeting," versus "static sheeting" where the kite lines are "set" and left alone). When the kites dive, they're more powerful, the boat goes faster, apparanet wind shifts forward, and you want to turn downwind. On the kite upturn, not only is the kite moving a bit "backwards (the vertical figure 8, or zig-zag pattern isn't perfectly vertical, but "leans" back at the top), but the force is lesser, the boat slows, apparant wind comes back and you must turn upwind--this isn't mandatory, but it is 1) fastest, and 2) will bring the average course closer to the wind for windward work. You can have very fine control, if you're willing to move the kite attachment point all the time. For high speed runs, I just set it up for optimal course, then try to push the kites at their optimum and go for it. My system has slow response; Flexis have very quick; so I just fly the kites off their optimal course to effect quick or emergency turns. I don't advocate this for casual flying, or flying with slower kites. ("wherever the kite wants to take you" Indeed! *I* control my kites, they do not control me! ;-) Dave = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =