We have discussed the effect of VSR on upwind and downwind performance in a number of places. But there are so many forums now we don't know what we've discussed where. The fun bit is that cart speed as a multiple of wind speed goes toward infinity as VSR approaches 1.0 from either side. Downwind for VSR < 1 and upwind for VSR > 1. Of course the closer you set the VSR to 1.0 the lower your losses have to be if you want something more than a paper weight. Achieving more than 3X to 4X wind speed would be quite a challenge in the real world.

Hai,



that´s why i would have suggested VSR = 1, symmetrical foils and a pitch mechanism for a universal (DWFTTW and ATWFTTW) high performance craft. However i have learned enough about the Blackbird to just have my fingers crossed for Your DWFTTW attempts with the NALSA officials .
On fasterthanthewind.org i learn that the wind is a bit strong and the chain in the drive train broke above 50 mph in a 20 mph trailing wind.

Sea You: Klaus (c:E

Yup. I just got back from the big event. We had it above 50 twice (at least). We broke the chain once and threw it off the chain-wheel once. Both are easy fixes. There's a lot of data to review before we know our exact results. Ultimately, it's up to NALSA once all the data has been crunched.

WIRED posted an update on our project: http://www.wired.com/autopia/2010/07/do ... t/#respond

It sounds like they plan to publish another article when last weekend's record runs become official.

Congratulations and great job.

Clew In

Richard Jenkins (recent winner of the world land speed sailing record) just submitted a great entry to our blog: www.fasterthanthewind.org

We met Richard recently when he spoke at the St. Francis Yacht Club about his recent record (which was 10 years in the making). I had no idea he thought we were crackpots at the time. I give him huge points for flying down to El Mirage to see it for himself.

A low looping kite is very similar to a propeller. It seems that a buggy or ice cart should be able to go faster than the wind with aggressive and continuous kite loops. A small kite in high winds with high rpm loops seems like it would be most efficient. Is this possible?

Unfortunately no. A kiteboard can tack it's way downwind faster than the wind, but it can't go directly downwind faster than the wind - not even by looping the kite. There has to be a mechanism to harness the relative velocity between the air and water. When the kiteboard is going directly downwind it has no way to do this. It could (in theory) do it if it had a submerged turbine connected to a prop in the air.

Let me see if I have this right. The faster than the wind machine works because each prop blade is in a constant reach to the wind. Like a sailboat going 90 degrees to the wind, or close to it. A constantly looping kite is also in a constant reach and should be capable of exceeding the wind speed while going straight down wind for all of the same reasons as the Ride Like the Wind trike. A mechanism such as a drive train does not seem necessary to achieving the goal. Drive trains by nature reduce transmission efficiency.

If a kiteboarder can tack or broad reach his way down wind faster than the wind than a looping kite which is always tacking through the downwind power zone would be able to do the same- especially on land or ice.

One might think this, but it's not that simple. Consider the kiteboard tacking its way downwind. If you had no fins and didn't edge the board, you'd simply end up sliding directly downwind slower than the wind. This interaction with the water is critical. It provides the kinematic constraint which keeps the board on a path that makes the vectors work out (I can post them if you like). With our vehicle moving straight downwind, the wheels and transmission provide that very same kinematic constraint. If the vehicle moves forward one foot, the prop tip moves a foot to the right. That's the broad reach. If I removed the chain, nothing would cause the prop to spin (and thus follow the broad reach path we need). It would be the same as a kiteboard trying to go directly downwind faster than the wind.

Consider the kiteboard when it's going downwind at exactly wind speed. There's no wind over it at all. No way to even keep the kite flying in this case. Make sense?