Recent content by yoavraz

A more direct answer: A "regular" sailboat is totally dependent on the relative wind. Theoretically it can go almost directly to the wind (close to 0 degrees) and still have forward-force from sail-lift overcoming drag, and have it in motion. However this force drops dramatically when...

I have a web page that can give you some insight about this question. It deals with approximating sailboat speed at given wind, including upwind and VMG. See http://yoavraz.googlepages.com/sailingboatspeedvs.windspeed BTW, I have found that the discussion mentioned here about...

Mender, I have to retract on one central point: From the vehicle point of view a treadmill at 10mph is exactly the same as back wind of 10mph. Indeed when the vehicle on the treadmill is stationary, the relative wind is 0. Same with outdoor at 10. Energy and momentum transfers as well as forces...

The prop creates the wind. Not the wind turns the prop. Critical difference. On treadmill - yes. Plenty of energy transfer. Outdoor - No. Past wind speed energy and speed in vehicle are lost until vehicle is below wind speed, and then speed increases again, may pass wind speed again, and so...

Again: When the vehicle is stationary, in a room with stationary air, no air moves around the vehicle, no wind is felt by the vehicle, no force of wind is applied to the vehicle, and no wind energy is transferred to the vehicle. The vehicle gets its energy from the turning wheels, that are...

Forget external. Real wind only by the propeller. You can call any imaginary object "wind," but it exists only if air really flows. With the treadmill DWFTTW is an empty name.

Forget about the wind. The only place you have a (external) wind in a DWFTTW on a treadmill is in the name DWFTTW (the W's)... I thought we have cleared this. Thus you have nothing to defend here. It boils down to a little energy from the treadmill that transforms in a quite sophisticated way...

That is great, and actually I can now see how when having the initial momentum, with inertia an effective DWFTTW can sustain enough thrust to maintain it moving. No wind exists when the vehicle is stationary relatively to room. (Of course, the propeller makes wind backwards, but no external...

kjgilkgihghi

Very simple: If the AIR DOES NOT MOVE, there is NO WIND! Look up definitions of "wind"

Thanks for video and info. See also the following treadmill DWFTTW video: http://uk.youtube.com/watch?v=dgHBDESd38M&feature=related that I picked in a search. First of all, a substantial difference exists between a sailboat and a DWFTTW. I was completely in sailboats, and the headline "sailing...

OOOPS. I knew there was a disconnect, but until now I have not realized we are talking about different experiments. I understand you have previous context. I apparently was thinking about a different forum from the one that was mentioned (I see this subject is popular...). At least we agree...

Putting guides, rails is an excellent idea, but even then I do not believe you can well control wind direction in an open treadmill at +-10 degrees (not even thinking of +-1/2)... I challenge you to put your good engineering to work, measure direction accurately (close-around and downwind the...

No, no, no. The test is fine, and the vehicles are great. I'm saying only one thing again and again: The wind is not exactly 180 in the tests! It is < 180 (maybe by little; or > 180 turning little to the other side) ! Then well engineered vehicles with good lift and low drag at < 180 can make...

I'm sorry, I misread your text and misunderstood your scenario. What I said was an answer to a different scenario and incorrect regarding yours. If we continue your scenario, air speed drops until it cannot overcome the wheels' friction with the treadmill, the wheels stop rolling (with air...