I posed a question waaaaay back a couple of weeks ago when I was a noob ;-) about lift vs pull and got some great responses. I know more now than
before I asked the question and that's the important thing to me anyways.
So here I am a few weeks later and still fascinated by this sport, passion, hobbie. I fly 'beginner' foils and rightly so but I wonder about the next
step. When I think of the 'step up' I think about a kite that has the potential to lift me and set me down gently... a floaty descent. The lift
(vertical) matters but so does the float.
So as I browse the different sites looking at the various kites and dreaming, I always find myself trying to guess if this kite or that kite has more
lift or pull or which one would be better/best for my next step up. I feel like I need a number or a factor or a rating of some kind. Wouldn't you
think there is some factor or combination of factors that I/we could use that would give an indication of the lift of a given kite?
For example, I gather that the Blade is the 'king of lift' as I read somewhere. Rather than just a qualitative statement, it seems that it would be
helpful information to also see a "Lift Factor" that would indicate that the Blade is king. If we know the A/R, and the area, and the shape, number of
cells, the profile, the lift/drag ratio, etc etc wouldn't you think that a "Lifty" rating could be calculated? Would you guys find this to be good
information or helpful?
And if you had a "Lift Factor" could you then have a "Floatability Component" so you could determine which ones will not only lift most but set you
down easier than the other?
Am I on the path to becoming a forum guru like so many others on this forum or am I headed to the psych ward at the local hospital??
:wee::singing::moon::roll:Kamikuza - 20-5-2009 at 11:30 PM
I'd be happy just knowing what a difference AR makes between the same kind of kites ... well for now
How much of lift/float is technique though?BeamerBob - 21-5-2009 at 04:03 AM
Donald, you are like me wanting to quantify things in order to be able to understand them. It really suffices to just go fly the things and your mind
assigns those numbers for you without actually giving them to you. The Blade, Crossfire and Bego (not meant to be in any particular order) are known
to have the most aggressive lifting tendencies. The differences in the amount of lift between the kites are minuscule in the big scheme of things.
There are tangible differences in the way each of these kites fly but those are just nuances that you pick up on after flying them. The common thread
between them is that they all are aggressive lifty kites. When I started that thread "Blade is king" it was more a reference to its design
proficiency. Yes it is lifty, but the kite I was referencing was a 6.5m Blade. That is a BIG fixed bridle kite from where I stand. Float generally
comes from the size of canopy the kite makes, IE. now that it lifted you off the ground, how big a parachute do you have to float down on. Even for
someone my weight, a 5m kite will both lift me and float me back down comfortably from about 12-14 mph. The 6.5m kite will do the same thing in less
wind and will float me down somewhat slower. You can't quantify this stuff because the wind will make every jump different. You can get 3-4 foot
jumps for an hour and then without doing anything different, have a gust hit right when you "pop" and you can go 2 or 3 times as high. I hope this
helps, but its cool if this only gives you more questions to be answered.
This is me spotting my landing. I had gone about 8 feet and was down to about 5-6 feet here. This is with a Crossfire I 5m in 15 mph winds. I
almost have the kite back overhead and therefore am about to need to redirect to finish the float down. action jackson - 21-5-2009 at 05:03 AM
Lift=Up.......... Float= Across ..................ajkitedemon - 21-5-2009 at 05:15 AM
This question one is getting into more complicated physics! I am not sure I am the best qualified to answer but I'll give it a shot, please expand or
make corrections as needed.
Lift is a product of the angle of attack of a kite or the pitch if that is easier to understand. Picture this the kite sitting at 12 and it is
completely parallel to the ground it would have a low angle of attack (AOA) This will produce a kite that is faster than than the same kite with a
high AOA it will have a wider wind window but will need more wind as well. The same kite rigged with a high AOA again picture the kite at 12 the tail
will be angled toward the ground and the nose up. This will require less wind to fly and will have increased lift and a smaller wind window.
Typically float is a product of kite size but not totally. Float is the continued lift produced by the kite. Some kites will continue to produce lift
which once off the ground is called float. This produces soft landings. Usually a product of size the canopy acts to slow you down but not always!
I have a very early Pansh Ace 5m it is the second most lifty kite I have flown (a F-one std9 takes that prize) My Ace is as I have discovered is an
odd one, and not quite the norm. It has a huge amount of lift a micro sizes wind window and is slower moving than my Best 17m. It has NO float. when
you get off the ground and swing under the kite it collapses on its self and falls. I keep it as I feel it is just too dangerous to use. I would never
sell it as I would hate to see somebody else get hurt. I have not cut it up as it reminds me of how expensive cheap can be. Before anybody jumps on me
I got it before the pansh web site went up so I think it is a early prototype and is VERY different from the last one I saw.
AR is a measure of the width against length simply put. Typically a long skinny kite will have less drag and fly faster. The faster a kite flys the
more power produced. AR is not AOA so a fast kite can be a lifty one or not.
I hope this helps somewhat.PHREERIDER - 21-5-2009 at 05:39 AM
aero force perpendicular to foil a function of foil speed
float is a decay rate after apex acceleration
best i can domgatc - 21-5-2009 at 06:26 AM
Lift = exhilaration
Float = fun
:Ange09:acampbell - 21-5-2009 at 06:51 AM
30 years ago I was active in the glider/ soaring community. Those aircraft could be equipped with the necessary instrumentation to produce complete
performance polars - charts depicting sink rate vs. airspeed to arrive at L/D performance with the flight envelope. Those things can achieve L/D
ratios of close to 60
I'm not sure you could measure this jumping within the confines of a static wind window where there are virtually no constants. I once saw a paper
somewhere that suggested we could arrive at L/D for the kite by plotting the airspeed of the kite through the window against the local true wind but
that would still be pretty squishy, I think.
Peter Lynn literature suggests that modern foils can achieve an L/D of about 6 at best, but when I pressed for the source, I was told it was
theoretical value arrived at through CAD software.
I once went as far as taking compass bearings of my wind sock and tire tracks but soon realized it was of little value without plots of buggy speed
and true wind velocity. It was easier to say "friggit" and go think about it more over a beer.
Or as Bobby indicates, just go fly...DonaldLL - 21-5-2009 at 08:56 AM
Bob, I didn't realize you had a post about the "Blade is King" I'll have to look that up. I was just referring to various comments I have read.
Most responses here are more along the lines of definitions and these do help me "get my head around" the concepts but in this case I was looking for
the technical response like that provided by Angus.
I might be beating this to death so I'll comment and then we can move on to other topics. I don't want to wear out my welcome! After I tought about
this some more I thought about this. On high end bicycles you are provided a drag coefficient which you compare to other drag coefficients and can
then have a rating and ranking of which bike has more/less drag... just the bike is factored in and no other components of drag. This coefficient can
be theoretically calculated but also be measured in a wind tunnel.
I know the same could be done for a kite but I guess there just isn't enough demand for this. You could have a lift coeeficient that was measured in a
wind tunnel that would say that at 15mph (or 12 or 18, whatever) with the kite parallel to the ground and perpendicular to the flow of the wind, where
this lift is actually calculated. The result would tell you, with all things being equal, which kites had more or less lift..... I think :puzzled:acampbell - 21-5-2009 at 09:11 AM
I know that Flexifoil has said they have done research in the Cambridge University wind tunnel but I'm guessing the data are proprietary.
Ted Dougherty of ProFoil fame had done some wind tunnel testing some time ago but I do not know what kinds of data were collected.
What we need is an engineering grad student with a kite looking for a thesis...BeamerBob - 21-5-2009 at 09:13 AM
Even if several mfrs did this, their test parameters couldn't be the same so comparisons would be of low value. The flight of the kite is so dynamic,
and then you add in the effect of tapping the brakes as a "power boost" on many kites and there is yet another pilot induced variable in addition to
the variability of wind speed, temperature, barometric pressure, angle of the kite relative to the ground etc. Some kites do their best work up at a
45 degree angle and yet others perform best right down next to the ground. You could come close by running 3 kites in 3 buggies on the same course
side by side for traction performance and switch kites between pilots after every run. In the end, you might only find that pilot "A" is better than
B and C no matter which kite he has. I'm afraid this is a very "seat of the pants" issue and not as simple to quantify as 0-60 times in a car or c/d
measurements of cars or bikes.BeamerBob - 21-5-2009 at 09:21 AM
Quote:
Originally posted by DonaldLL
Bob, I didn't realize you had a post about the "Blade is King" :puzzled:
Originally posted by acampbell
What we need is an engineering grad student with a kite looking for a thesis...
Had one, but he switched majors and started studying plovers. :wow:
Sorry.... that one was just too choice.
ATB,
SamDonaldLL - 21-5-2009 at 09:08 PM
Quote:
Even if several mfrs did this, their test parameters couldn't be the same
Why not? If you put a 5 different kites in a wind tunnel under controlled conditions with all things being equal and measure the vertical force
created by each kite, then you can rank the kites for lift from least to most. If you made the test parameters the same and took out all the variables
like 'tapping brakes' or other pilot induced effect, then you'd be testing just the lift of the kite. Back to the example of the bicycle drag
coefficient... or use the drag coefficient of a race car, indy car, whatever. Of course the end result of who wins the race has to do with air
pressure, temperature, humidity, tires, track conditions, driver, pit crew, etc., but you can still isolate a particular parameter in question.
That's the basis of how you can compare one factor to another. IMO.. the truth probably lies somewhere in between
I'm gonna go read your Blade is King thread... how did I miss that one??
Angus.... you're right! That would be an excellent thesis. I'm sure the student would have many volunteers to help with gathering the data.BeamerBob - 22-5-2009 at 04:32 AM
Ok, you're thinking we get all the major mfrs together for a little tea party at the wind tunnel. Most mfrs won't even recognize that the other
companies exist much less cooperate together for a comparison in which they might not come out on top. If you go on the premise that an independent
entity do the tests, then that would work and hopefully be objective. We just need a magazine with some staff to set it up and report the findings.
Even then you wouldn't get the complete picture of the potential performance created by a skilled pilot. You have to either have mock races where you
switch out kites every heat or just fly all the kites yourself in like conditions. That would be WAY more fun than reading an article on it. If you
read kite reviews, you can put together a mosaic of observed performance for various kites to help guide you in a purchase. You would likely be happy
with any of your top 2-3 choices though.Superdog - 22-5-2009 at 06:01 AM
Quote:
Originally posted by acampbell
What we need is an engineering grad student with a kite looking for a thesis...
i will bear that in mind if i get that far DonaldLL - 22-5-2009 at 06:23 AM
Quote:
Most mfrs won't even recognize that the other companies exist
Well Bob that may be true but what does this have to do with the fact that the lift porperties of any wing/foil can be quantified?
Of course, it would have to be an independent study otherwise it's called a commercial!
If Flexifoil and/or Ted D have done wind tunnel testing are they testing everything else EXCEPT lift?
If you measure the drag coefficient of any 2 vehicles for example and for A drag =.5 and for B drag =.6 then 2 pilots race against each other and B
beats A well then you conclude that it ain't just the drag coefficient that wins the race; but you can still conclude that A creates less drag.
I am sure this lift factor/coefficient exisits for wings, foils, sails. In the case of this sport it's just not published or it's not investigated
because there's no money in it. If power kiting or traction kite sports had the dollars in it that the America's Cup has, you'd see that lift factor
out to several significant digits... and yes, I know it also depends on the wind, the captain, the crew, etc... and the sail with the greatest lift
doesn't always win.
BTW, that was an excellent thread and post about the Blade IV... makes me want one but man I don't think I'm ready yet.Soylent - 22-5-2009 at 07:21 AM
Though the statistics would be useful, wouldn't it tell us what we already know? Thats why I love the forum. I can get most of the information/advice
I need here from those with years/decades of experience so I can make an informed decision. The only thing better is events such as NABX or when there
is a dozen kiters on the beach where I could get a true feel for a variety of kites...It also helps having Dagon and Dakitez nearby.kitejumper - 22-5-2009 at 08:04 AM
flying a kite in varied conditions helps me,rather than reading mostly meaningless statsUSA_Eli_A - 22-5-2009 at 08:48 AM
no you cannot quantify. unfortunately kiting is an art. so getting lift and float from your kite is an art as well. I love it when people ask me if
I can tell them exactly how, if you live inside the box, kiting might be the wrong sport for you.
I've watched a kite designer work his magical kite pooping program. Quickly realizing there are more important things in life like...ummm...flying
them, I went snowkiting.
I wouldn't concern yourself with numbers, again. Get your hands on as many kites as you can!!!DonaldLL - 22-5-2009 at 12:11 PM
Quote:
no you cannot quantify. unfortunately kiting is an art.
Oh, I agree, there is definitely an art to flying the kite... but again, this introduces the human factor. I am not talking about the human factor. I
am afraid that the design of the kite is based on engineering design and technical data. Next time you have the opportunity to talk to one of
the manufacturers ask them if they use a scientific methodology in the design of their kites, i.e. factors like lift, drag, A/R, etc.
Ok, so how about this, we agree to disagree and just be thankful that it's all about fun :wee:
In the meantime... it looks like I can see the blue sky for the first time in 4 days (no rain) and there's even a bit a movement in the trees. Please
know this, aside from this debate, coefficients and factors excluded, I am going to grab my kite and see if i can get some air time... and no I won't
be thinking about equations when the kite launches :wink2:
