Power Kite Forum

LEI vs Foil, race times

sarahmaria - 17-5-2006 at 03:58 PM

At the risk of revealing of how little I know, can someone please help me out and explain the basic differences between the types kites and their structures. I realize that foils are considered more powerful, but I don't know why - and don't know if this comes at the expense of less durability during crashes or less controlability, etc.

Also, it is easy to find various recommendations for strong or powerful kites, but it would be really helpful for some research I am conducting to get some numbers attached to these. Does anyone know if any kite races post times along with what type of kite was used to get that time? I am most interested in reach during straight stretches, rather than complete courses, but would be very very happy to find any data.

Thank you so much!

awindofchange - 17-5-2006 at 06:30 PM

It would be very difficult to answer all of your questions in one simple post but I will do what I can and hopefully others will add in (or correct me) where they can.

First the term foils is fairly vaugue, as far as foils go there are several different designs. Peter Lynn and Flysurfer both make water relaunchable foils that are very similar to LEI's in shape, they are considered foils but are very different than land based bridled foils in terms of power output per size and quite similar to LEI's in power output per size. What I am assuming you are referring to is bridled open celled ram-air foils as compared to C-shaped LEI style kites.

The main difference between LEI's and open celled ram-air foils (we'll refer these to ram-air's for simplicity) is a small thing called projected area. Ram-air's are fairly flat in the wind, making nearly the entire kite capable of producing power - hence the projected area of the kite is usually the same as the actual size of the kite. C-shaped kites (LEI's, Peter Lynn ARC's, etc... referred to as LEI's) are as the name says, C-shaped and only the center of the kite catches the wind and produces power, therefore their projected area is much smaller than the actual size of the kite (ok ok...there are a lot of technical details as to how much of the kite is the actual projected area and how much of it produced power but I am trying to keep this as simple as possible). As an example, a standard low aspect ratio LEI kite may have a flat area size of 14 meters but the projected area is only about 7-8 meters. A ram-air may have a flat area size of 8 meters and its projected area is also 8 meters...the two kites will produce about the same amount of power in the same winds (again, this is simplicity and there are a ton of technical things that are left out).

The next thing that needs to be taken into consideration when it comes to power output on a kite is the actual design of the kite itself. A high aspect ratio kite will generally produce more power output than a low aspect ratio kite of the same size. The increase in power usually comes at the expense of stability. Kites can also be designed with certain performance gains as well. Some kites will have a tremendous amount of lift designed into the kite (most surf kites, Ozone Frenzy/Access, Blades, etc... just to name a couple). Other kites will be designed with very little lift but capable of tremendous speeds (Ozone Razor/Yakuza, JoJo RM, etc... again, just to name a few).

Durability in kites is built in at the manufacturing level, although no kite is completely indestructable (well, the beetle may be the only exception) some designs are more durable than others. Ozone and Flexifoil (as well as some other manufacturers) make some extremly high quality kites that can take a huge amount of abuse and still continue to perform, other manufacturers (which I will advoid naming for obvious flaming reasons) don't have the quality in the construction and can be destroyed with a couple or even one good ground slamming. This is true for all makes and styles of power kites (LEI and Ram-Air foils).

Controllability - Nearly all quad line kites will have the optimum amount of control and other than the actual kite design, the control isn't much better or worse from one quad line kite to another (LEI and Ram-Air foils included). Most all surf kites as well as most snow specific designed kites are designed to fly off of a control bar. These kites have built in depowerability and the control bar allows you to utilize it in the easiest and safest way. Ram-air foils are normally flown off of handles and in nearly all instances, handles will give you the ultimate in control and is much better for control than a control bar (I did say nearly all instances, there are of course a couple of exceptions).

Now I dont currently know of any posted kite races that have the speeds and the equipment used listed along with the winners. I am sure that the information is available somewhere, hopefully someone here will be able to post a link to some or will have that info for us. I think that would be some really neat information to see what people are using. Normally the high aspect race kites will give you the fastest speeds - but LUK would probably be able to smoke me using a Little Devil even if I was giving it my all on a Yakuza lol. Unfortunatly the kite doesn't make the racer, its the racer that makes the kite!

Anyways, hope this gets you going in the right direction and that it gives you a basic idea as to what the different types of kites are and why they perform the way they do.

Scoopy - 21-5-2006 at 07:09 PM

Hey Sara, read my newbie guide. There is lots of information there about this.

Scoop