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### Foil / LEI comparisos on snow, land, sea

Posted: Wed Jan 02, 2013 5:41 pm
Hi guys and happy new year

could someone give a list e.g. what size of foil kite you need when you use a 10 meter LEI?

### Re: FOIL / LEI comparisos on snow,land,sea

Posted: Wed Jan 02, 2013 6:06 pm
10 foil or 12 Arc.

### Re: FOIL / LEI comparisos on snow,land,sea

Posted: Wed Jan 02, 2013 6:07 pm
voodoospirit wrote:10 foil or 12 Arc.
so the difference is 2m in each size? e.g. 9m LEI = 7m foil ??

the foils "drag" more??

### Re: FOIL / LEI comparisos on snow,land,sea

Posted: Wed Jan 02, 2013 6:15 pm
voodoo was asking a question, not answering it. foil is a supported soft skin kite with an intricate bridle to support the foils draft, etc. arc is also a soft kite, but minimal or no bridles, so the curve of an arc looks more like a LEI.

that being said, you are correct in that a foil will be about 2-3m more powerful on average due to the open nature of the profile. It just grabs more wind per square meter.

hope this helps,

bob
www.kiteridersllc.com

### Re: Foil / LEI comparisos on snow, land, sea

Posted: Wed Jan 02, 2013 7:14 pm

10LEI = 10 foil = 12Arc more or less.
some foil will develops more power ( bow- high ratio) than a LEI, others less just like delta vs bow vs C-shape.

### Re: Foil / LEI comparisos on snow, land, sea

Posted: Wed Jan 02, 2013 8:07 pm
loosely yes. voodo is correct

but i'd call foil 1m or 2m smaller for the same power.

so lei 10m, foil 9m, arc 12m.

but in general an lei will have a bigger wind range.so you can use a bigger size for get the same or better bottom end and have the same or better top end.

Eg the 7m frenzy feels real good 25 -30 knots top end about 35. 8m catalyst feels the similar power but i can hold to 40 knots in the gusts, I can still get a little more top end out of the catalyst than i can the 6m access.

On the other side my 15m speed feels more powerfull than a 17m zephur. it definately has trucks more lift than the zep. I can get a better lower end on the speed on flat water. but on in lumpy swell, current, white wash and waves the faster speed of the zep means i can get a lower end on the zep in those conditions.

Foils tend to float alot better than leis. I trust the foils way more to land me super soft when i'm jumping above hard stuff.

### Re: Foil / LEI comparisos on snow, land, sea

Posted: Wed Jan 02, 2013 9:13 pm
closed cell foils have close to the same depower as LEI, open cell foils , not. Arcs have a huge top end, but lack in low end

### Re: Foil / LEI comparisos on snow, land, sea

Posted: Wed Jan 02, 2013 9:52 pm
Hi Nik. Thanks for asking. As requested, below is a list comparing ram airs (foils) and inflatables on land, water, and snow. Cheers, Pumpy.
Inflatables are vastly superior to ram airs. I've summarised the reasons for the superiority of inflatables:

LIFT TO DRAG RATIO (L/D)
Rams have HUGE drag ("D") compared to inflatables for 3 reasons:
a) Increased friction at the "boundary layer"; ie interface between air & kite, because of minute ripples in ram air kites.
b) Bridle drag.
c) Thickness. Ram lovers describe the diameter of inflatable leading edges as a liability. However, the thickness of ram airs is typically two to three times as great. Worse, much of the thickness is near the trailing edge, causing gross aerodynamic inefficiency. An inflatable trailing edge, in contrast, is thin and aerodynamically efficient.

MASS & INERTIA
Ram airs contain a huge mass of entrapped air; consequently inertia is HUGE. Large ram airs (eg Flysurfer 19m & 21m) contain ~5kg of air in their cells vs 0.5kg in the tube structure of inflatables (e.g. calculation: 21m2 x 0.2m x 1.2kg = 5.04kg). The huge inertia of ram air kites, sitting at the end of ~25m lines, causes a multitude of problems including poor acceleration, slow turning, difficulty kitelooping, and inferior dynamic power (the power generated with sinusoidal kite movement).

RIGIDITY, STABILITY, BRIDLE STRETCHING, & FOIL SHAPE
The semi-rigidity of inflatables improves consistency, stability, turning, handling, and aerodynamic profile. Ram airs are soft and floppy.

Birds, wasps, stunt kites, and planes are rigid. ALL high performance aircraft (eg hang-gliders vs paragliders) have rigid structures. Rigid hang gliders out-perform soft paragliders on all measures. Interestingly, the trend in paragliders is towards increased rigidity, e.g. stiff mylar reinforcements, plastic stiffeners in the leading edges and carbon fibre rods sewn into the ribs. These stiffening innovations have resulted in paragliders that are so successful in competition that old-style soft gliders are no longer competitive. Similarly, kite manufacturers are always looking for ways to make kites more internally rigid, eg by joining the struts firmly to the leading edge, adding fifth lines, and mini-bridles.

Semi rigidity enables inflatables to withstand gusty conditions better than ram airs. Ram airs deform, fold, collapse, and twist in gusty conditions. For stability problems in ram airs stemming from lack of internal rigidity, see: http://www.foilzone.com/phpbb3/viewtopi ... sc&start=0

Check-out this ram air kite loop http://vimeo.com/10799435 You'll notice the kite partially collapsing during the loop, leading to the rider being slammed into the water.

A major weakness of the soft structure of ram airs is a lack of tactile feedback. The kites are soft so the feedback is soft, sloppy, and imprecise. Rigid inflatables, in contrast, provide a wealth of nuanced feedback to the rider, eg kite position, speed of turn, and gradations of power delivery.

After several weeks of use, ram air bridles typically stretch and deform, further compromising aerodynamic performance:
Kamikuza wrote: Have you done a mixer test and checked your SPL length?
SPL = spare parts line = the bright yellow lines that go through the pulleys... they can shrink A LOT and bork up the handling..
joffaburger wrote:Moved to a foil kite 5 years ago (flysurfer pulse 10m)... I found after 6-9 months that the RAM started performing very poorly especially in gusty conditions I assume this was due to bridle stretching, I did manage to trim the bridle regularly to what I thought was intended spec however as already stated these are complicated bridles with many attachment points and I'm not sure if I did a perfect job! In the end I couldn't get the kite to feel anywhere near how it performed during the first 3 - 6 months of it's life. I think the kite and the bridles became quickly blown out...The kite was expensive and an attempt to resell the kite at half its purchase price failed...
TURNING & SLED EFFECT
The tips of inflatables act as rudders, enabling faster, more controlled turns. Also, they enable a "sled effect", leading to better stability and predictability. This "sled effect" is pronounced in C-kites and is noticeably poorer in bow kites and ram airs.

LUFF CURVE/DEPTH PROFILE
Luff curves vary extensively. Inflatables with flat luff curves sit forward in the window whereas inflatables with deeper luff curves sit further back in the window. Those from sailboarding backgrounds can appreciate the analogy: For more "bottom" end with a sail, you deepen the luff curve by releasing the outhaul. Fore more "high" end, you make the luff curve shallower by tightening the outhaul. Inflatable kites are deliberately engineered with different luff curves and this determines many performance differences, eg deeper luff curve kites are better for "wakestyle" because they sit deeper in the the wind window and generate more constant pull whereas shallower luff curve kites sit more forward in the window, jump higher, have lower bar pressure, and go upwind better.

The excessive drag and inertia of ram airs causes them to sit further back in the window compared to inflatables. Also, when ram airs move too close to the side of the window, they start collapsing and deforming. Hence, there is less scope for ram designers to modify the luff curve.

Because of the semi-rigid structure inherent to inflatables the luff curve and overall aerodynamic profile is much easier to standardise and maintain.

RELAUNCH
Ram airs can be VERY difficult to relaunch e.g.

It took a long time for the guy in the video to relaunch his Flysurfer and the kite almost bow-tied on two occasions. If only ONE wave had landed on it, he would have had to swim in, dragging his waterlogged kite with him.

Beginners find relaunching inflatables easy after a few sessions. For advanced beginners and above, relaunching should not even be considered in the equation because a) they won't be dropping the kite much anyway and b) Relaunching inflatables is EASY. Commonly, ram airs will not relaunch properly because of twisting, bridle tangles, or waterlogging. These aren't such big problems with inflatables. Check out these links about ram airs sinking or becoming un-relaunchable:
eg viewtopic.php?f=1&t=2346569
eg viewtopic.php?f=1&t=2358958&p=608890#p608890
eg viewtopic.php?t=2359156&p=617396
eg viewtopic.php?t=2358602&p=704984

SAFETY
Inflatables are safer than ram airs because:
a) Downwind launches are SCARY and can be dangerous. Eg viewtopic.php?f=1&t=2359529 . Because only a small bunch of slightly weird people use ram airs, there is confusion about their correct use, leading to potentially dangerous situations eg viewtopic.php?f=1&t=2360971
b) Because they lack rigidity, rams deform, twist, wineglass, and jellyfish in the middle of the power zone when they are downwind of obstacles or in gusty conditions. This is VERY dangerous. Ram airs can become uncontrollable in gusty conditions, endangering the rider and other beach users.
c) Surf conditions
While it is always a gamble if a kite gets caught by a wave, at it has a fighting chance if it is an inflatable. Ram airs can be EXTREMELY difficult to relaunch in the surf (see above - "Relaunch").

BRIDLE TANGLES & FAILURES
Bridle tangles and breakages are disturbingly common with ram airs. Check these threads http://www.foilzone.com/phpbb3/viewtopic.php?f=1&t=5437 and viewtopic.php?f=1&t=2354115&start=30
In particular:
schmoe wrote: A bridle tangle on flysurfer can mean that you do not go out... For me I had many lost hours where the wind is cranking because of the bridles. I rather inflate 5 tubes and know that the setup time is exactly 10 minutes, no more no less, than have setup time that is 70% 5 minutes and 30% an hour. And now with one pump, the setup time of a tube is less, so it is not an advantage of the foil anymore.
Ram air bridle tangles can be very dangerous. A lot of riders have reported how their ram airs caught seaweed in their bridles, causing their kites to wineglass and spin out of control. Breakages can be expensive (US \$500 plus). eg "Flysurfer Warrior Exploding" viewtopic.php?t=4612

PRE-INFLATING
Ram users struggle to pre-inflate in a lot of situations eg cross-offshore conditions and downwind of promontories. I once witnessed a Flysurfer ram lover trying to launch on the lee-side of a headland in cross-offshore conditions. A friend grabbed one tip while he grabbed the other tip while they ran up and down a narrow strip of beach, trying to pre-inflate, to no avail. He packed up and went home while the inflatable riders drift launched.

RESALE
Contrary to the propaganda of ram lovers, ram airs have inferior lifespans compared to inflatables. The initial cost of ram airs is ~ 2-3x that of inflatables and their relatively greater depreciation over 2-3 years means you LOSE a lot more \$. Also, a major determinant of lifespan is obsolescence. In 2-3 years, today's kites will be superseded and won't be worth much. In addition, bridled ram airs lose performance quickly because of bridle stretching (see "bridle stretching" above).

REPAIRS & COMPLEXITY
Ram airs are shockingly complex. They have over 1000 parts, many of which require regular tweaking e.g. viewtopic.php?f=1&t=2374470 Ram air repairs are a LOT more expensive eg viewtopic.php?t=4612 Trained PARACHUTE repairers are often needed for big rips. Bills >\$1000 are common, eg viewtopic.php?f=1&t=2348790 Ram air companies sometimes refuse to honour warranties, e.g. the case above where the kite was <1 year old.

COMPETITION
Ram lovers are all talk and no action when it comes to competitions. NO ram riders have ever made it into the top 20 on the PKRA http://www.prokitetour.com/ or placed in a SIGNIFICANT well-attended event. The top pro riders ALL choose inflatables because of superior aerodynamics. ALL world records and titles (hang-time, speed, freestyle, waves, height, course-racing) are held by inflatables.

LAND & SNOW
Inflatables are also superior on snow and land. More and more riders are recognising this:
viewtopic.php?t=2374293&p=735337
viewtopic.php?f=1&t=2355153
viewtopic.php?f=1&t=2367967&start=40

LIGHT WINDS
Ram airs are inferior light wind kites for the following reasons:
a) Excessive drag
(bridles, lack of internal rigidity, excessive friction at the "boundary layer", and trailing edge thickness), compromising the Lift/Drag ratio
b) VERY slow turning
c) Inertia. See above.
d) Bridle failures and tangling
e) Wind dropouts and gear failure
ALL kiters experiences a few gear failures (eg broken lines) and COMPLETE wind dropouts every year. Inflatables can be "sailed" (self-rescued) or swum to shore. If things are REALLY bad, the inflatable structure can support your weight, eg viewtopic.php?f=1&t=2368004

In contrast, ALL ram airs eventually become hopelessly waterlogged, un-relaunchable, and unable to support body weight.
eg viewtopic.php?f=1&t=2346569
eg viewtopic.php?f=1&t=2358958&p=608890#p608890
eg viewtopic.php?t=2359156&p=617396
eg viewtopic.php?t=2358602&p=704984

The following is an example of "diraklib's" experience with ram airs in wind dropouts:
diraklib wrote:"the SA-19 is huge and can whack you silly if you let it get down wind of you in a low wind launch. It is downright scary - be ready with the QR at all times if not up and riding!!! I can't say I agree with claims that you can ride the SA-19 in anything lower than a steady 8 knots. I made a personal choice to not ride the SA-19 any more. It went down twice in lulls and managed to bow-tie on the way down - there was no way to relaunch. I was not as lucky as others that self rescued. My kite was full of water by the time I dragged my very tired and frustrated a\$\$ to shore. It sounds simple, "wrap the lines around the bar, fold the kite in half, roll it up on your board and paddle in"... noooo... there are lines everywhere under water that wrap around your feet as you are trying to manipulate the kite. You just pray that a gust won't pop the kite up and slice of an appendage. The kite ... is just too scary when it goes down. My attitude now is - if my LEI won't fly, I shouldn't be on the water. Anyone interested in a slightly used SA2-19m??? Cheap???"
For the full epiphany, checkout viewtopic.php?f=1&t=2360979&start=40

The following is the experience of "pmaggie" with ram airs in wind dropouts:
pmaggie wrote:I rode foils only a few times, so these are really my two cents. The problem I experieced with foils in very light wind when they suddenly fall. In my home spot, in very light wind days, sometimes the wind really goes to zero for 1 minute or so. When this happen, both foils and inflatables suddenly fall. In this cases, my inflatable, since it's far heavier than a foil, fall directly into the water with no line tangling and I just have to wait for a gust to relaunch (when possible, that means about 7 knots for my Core 17). When a foil falls with no wind, being very light, it's common that its lines roll over it and became completely tangled. At that point, it's not that easy to relaunch.
The other big problem with foils in very light wind is when the wind completely stops. With an inflatable, you just get your kite and swim attached to your little floating boat. With a foil, you have 20 sqm of tissue to carry home with you!
For the full story, checkout: viewtopic.php?f=1&t=2376332

Here is the experience of "FredBGG" with a line failure:
FredBGG wrote:The other day I had a front line fail.
Wind was slightly off shore...
I really needed a tow to the beach.
I had the kite safely on the 5th line folded in half (flysurfer Foil)
I waved down two kiters.... both expert judging by their riding.
Both refused to help.
One even yelled if you can't relaunch it's your problem.
Anyway after a difficult ordeal in the surf and current I got back to the beach.
I had to rest a bit but my board was still out there.
The problem here isn't with the other kiters, it's with Fred's choice of kite. If Fred had an inflatable, he would have been able to "self-rescue" by grabbing the tips and "sailing" to shore. The other kiters refusing to help is understandable: Fred opted for less safe equipment. It's his problem and he shouldn't impose on others to make up for his equipment deficiencies. Also, towing a ram air to shore is like towing a sleeping bag full of water - difficult and dangerous.

f) 8 knot limit
Despite the lies of ram lovers, you won't really get going on any kite (ram air OR inflatable) unless the wind is over ~ 7-8 knots and won't really have fun until ~ 10 knots.

This video may prove the 7-8 knot low limit. Both kites - the 21m Flysurfer and the smaller (?17m) inflatable are FAILING TO STAY UPWIND and, by the look of the flag, there's about ? (hard to say) 8 knots of wind.

It's interesting to note that the ram air and the inflatable are both struggling IN SIMILAR CONDITIONS.

Ram lovers have been shown to lie repeatedly about their light wind capabilities:
eg "jumping 8m in 8 knots" viewtopic.php?f=1&t=6349
eg viewtopic.php?f=1&t=2350141&p=539227#p539227
eg
gmb13 wrote:My Speed 3 19 DL gives up under 5 knots... - Gunnar Biniasch
Wind moving at <7 knots (13km/h) simply cannot deliver enough power for ANY kite to perform; certainly NO KITE WILL PERFORM AT 5 KNOTS. Gunnar's exaggerations can be found at viewtopic.php?f=1&t=2361421

g) Objective Testing
A variety of kites were tested in a "Light Wind Showdown" in San Diego viewtopic.php?f=1&t=2319439&hilit=ram+a ... +san+diego . Despite the over-hyped claims from the U.S. Flysurfer rep, Ted Bautista, Flysurfer ram airs crashed and burned. The overall consensus was that ram air kites are ok in light wind, but turn VERY SLOWLY. The overall impression was that there are much better inflatables.

h ) BIG INFLATABLES are better than BIG FLYSURFERS in Light Winds

See this thread about the poor light wind properties of Flysurfer viewtopic.php?f=1&t=2349064 , in particular:
gobigkahuna wrote:I read all the same reports and reviews that everyone else here probably read and spent the "big bucks" for the S2-19, but to be honest was extremely disappointed and sold it…Flysurfers just plain suck in gusty, light winds…I had a hard time keeping the thing in the air much less getting enough power from it to go on the water… A couple months later I got an 07 Waroo 20m…and it is the best 20m I've ever flown. I am able to fly it in winds I would never have thought possible.
i) Peter Frank's opinion
Peter Frank, a well respected commentator on the sport, says 8-9 knots is the bare minimum viewtopic.php?f=1&t=2365531
Peter_Frank wrote:
Night_Thrasher wrote:What is the lowest wind condition I can go kitesurfing and what is the best kite brand and size for it?
It depends a lot on your weight, how low you can go.
If you are "average" around 80kg, the lowest you can go will be around 5m/s (10knots) with the right kite and board.
If you are REALLY experienced, you will be able to push the lower limit down to about 8-9 knots, but this is the absolute lowest wind possible to kitesurf in (holding ground/going upwind) with average weight IMO.
And talking about EXACTLY how "low you can go" is just pure bullshit - as you can not measure the windspeed at the kite, which is the only true value for this.
Sometimes you have a huge windgradient, sometimes a small one, and air temperature and height also influences.
But around 10knots is the limit for most kitesurfers, and just a small tad lower for the "extreme" ones
When you talk about windspeed - where is it measured then ?
At headheight, maybe around 2 meter above the water ?
Or at 10 meter height, which is our (Denmark) meterological standard height for wind measurements ?
There is a difference of typical 2 knots, so VERY important.
My point is - always take those claiming "this and that" as their minimum wind speed with a grain of salt
Peter
RACING
Ram airs are inferior race kites. They have not placed in recognised races for years. They tend to collapse on downwind runs and their inertia means they are too slow to turn and react.
viewtopic.php?f=1&t=2377938
plummet wrote: In light winds on lumpy seas with big surf i'm finding the speed to be very annoying. The chop and swell slows you down so you cant get speed to boost. the slow turning and completely non existant down wind ability is a real pain in the waves. also when you do ride a wave upwind the extra speed powers the kite up and tears you off the wave face.... grrrrr.
I've come to the conclusion that it really is a flat water or land kite.
jakemoore wrote:I am having mixed luck going downwind with speed 3 especially on the raceboard. When I lose line tension, I just fall right into the water, and it takes a minute to build it up again.
plummet wrote: Yes i also loop downwind. which is fine unless your on a wave and the wave is pushing you faster than the loop..... then its tack upwind or have an expensive pile of fabric get washing machined in the surf.
SUMMARY
Ram airs suck at racing.
Ram airs collapse and twist on downwind legs.
Ram airs suck in chop and waves - THEY ARE A FLAT WATER OR LAND KITE (if that).
Ram airs cause the rider to fall into the water on the downwind legs. Often you end up with an "expensive pile of fabric getting washing machined in the surf"!!!

GEEKS, WEIRDOES, & SOCIAL MISFITS
Inflatable riders tend to hang out and help each other; there's a high level of collegiality. Ram lovers tend to be regarded as outsiders and slightly weird. This is because ram lovers are a tiny minority on the beach, inflatable riders are unfamiliar with the special requirements of ram airs, and partly because, as a group, ram lovers DO tend to be weirdoes. One of the simple practical problems with being part of a weird minority is that it can be difficult to find people to help launch and land your kite, eg http://www.seabreeze.com.au/forums/Kite ... -on-beach/
joffaburger wrote:Moved to a foil kite 5 years ago (flysurfer pulse 10m). As far as RAM air kiters being weirdos I can honestly say that you find out who your real friends are on a kite beach when you switch to a RAM air kite! Many of the people who used to help me launch suddenly lost their hands as I flew LEI kites for 3 years before trying a RAM air I would have to say the guys on beach changed their attitude towards me rather than I became weirdo overnight!
I'm not sure why so many ram lovers are strange weirdoes… maybe their weirdness is self selecting, i.e. There must be some sort of psychological problem in the first place to deliberately choose inferior kites in the face of overwhelming evidence of the superiority of inflatables.

Kite propaganda.
And the lies.
Of ram airs ignore.

### Re: Foil / LEI comparisos on snow, land, sea

Posted: Thu Jan 03, 2013 12:44 am
I was just reading the last post about ram-airs. I do agree with you about a lot of the problems that ram- airs have, but if you are comparing paragliders to single skinned hang gliders then paragliders actually have a bit better L/D ratio which would translate into better upwind performance in the Kiteboarding arena. Double skinned hangliders, however do have a much better L/D ratio than paragliders. So maybe if they ever design a double surfaced inflatable kite then it probably would outperform a ram-air in upwind ability.

### Re: Foil / LEI comparisos on snow, land, sea

Posted: Thu Jan 03, 2013 3:25 am
Shawn K wrote:I was just reading the last post about ram-airs. I do agree with you about a lot of the problems that ram- airs have, but if you are comparing paragliders to single skinned hang gliders then paragliders actually have a bit better L/D ratio which would translate into better upwind performance in the Kiteboarding arena. Double skinned hangliders, however do have a much better L/D ratio than paragliders. So maybe if they ever design a double surfaced inflatable kite then it probably would outperform a ram-air in upwind ability.
Ignore that post - PMU is full of shit, frequently disproved, and more often than not just COMPLETELY WRONG. But he still puts up that copy'n'paste post anytime 'foil' is mentioned... because of autism.