Merged DDWFTTW in a “Real” Wind

[windgrins]

Question for Spork and JB

Guys,

Serious question: You've mentioned in various places that "The parameters of the craft (the prop-pitch and gearing) give us the theoretical max speed".

Does this mean that once the pitch is coarsened to the point of the distance covered by the prop = distance covered by the wheels, you have reached an absolute limit?

Near this point the limit velocity would appear to be then constrained by the prop tips going supersonic and the drag rising precipitously.

I could have this all confused!

Would you please elaborate on these issues as I'm just very interested.

Regards,

Windgrins

I'm just cutting it back to a smile to keep Dr. Keith Happy!

 

[ThinAirDesigns]

Does this mean that once the pitch is coarsened to the point of the distance covered by the prop = distance covered by the wheels, you have reached an absolute limit?

The theortical speed capability of the device (both upwind and down) moves towards infinity as the ratio of the pitch of the prop to the distance covered by the wheels approaches 1:1 from either direction.

Near this point the limit velocity would appear to be then constrained by the prop tips going supersonic and the drag rising precipitously.

Those certainly become the practical limiting factors. The curve gets steep very fast. We believe that 4x - 5x wind speed is doable with enough money.

JB

 

[windgrins]

Thanks JB

The theortical speed capability of the device (both upwind and down) moves towards infinity as the ratio of the pitch of the prop to the distance covered by the wheels approaches 1:1 from either direction.



Those certainly become the practical limiting factors. The curve gets steep very fast. We believe that 4x - 5x wind speed is doable with enough money.

JB

Thanks much JB (oops, I mean for Dr. K!)

 

[A.T.]

Serious question: You've mentioned in various places that "The parameters of the craft (the prop-pitch and gearing) give us the theoretical max speed".

Does this mean that once the pitch is coarsened to the point of the distance covered by the prop = distance covered by the wheels, you have reached an absolute limit?

When you adjust the parameters such that desired airspeed equals the ground speed (vehicle advance ratio = 1) the cart will be stalled.

Near this point the limit velocity would appear to be then constrained by the prop tips going supersonic and the drag rising precipitously.

Near this point the net thrust is very low, so any source of inefficiency stops you easily. The acceleration is also very low.

Check my diagram. It shows the theoretical max speed (no loses), realistic speed (with loses) and initial acceleration, as functions of the vehicle advance ratio.

 

[windgrins]

Thanks A.T.

When you adjust the parameters such that desired airspeed equals the ground speed (vehicle advance ratio = 1) the cart will be stalled.


Near this point the net thrust is very low, so any source of inefficiency stops you easily. The acceleration is also very low.

Check my diagram. It shows the theoretical max speed (no loses), realistic speed (with loses) and initial acceleration, as functions of the vehicle advance ratio.

[qimg]http://i54.tinypic.com/2gv0kew.png[/qimg]

Thanks A.T.

I will study that in detail. I can basically see what I'm after is in there. It's about time for bed for me so I'll go over that tomorrow when I'm fresh. I appreciate the post.

Regards,

WindGrins

 

[A.T.]

The Greenbird contender: http://lehighlandyacht.com/

Interesting stuff about how they want to optimze the tires for lateral loads:
http://lehighlandyacht.com/?page_id=75

 

[humber]

The theortical speed capability of the device (both upwind and down) moves towards infinity as the ratio of the pitch of the prop to the distance covered by the wheels approaches 1:1 from either direction.

"The theoretical minimum speed not only approaches that of Brownian motion, but the BB regularly achieves it"

 

[spork]

The Blackbird will be on display here tomorrow: http://sfbrightworks.org/opening/

I will be there to answer questions.

We've been asked to display it here on Sunday: http://www.miramarevents.com/dreammachines/

We passed on this one, but I might do it at the last minute if logistics permit.

RC

 

[Michael C]

Thanks to Dr. Keith, Modified, Michael and for the polite replies.

You thank us for the politeness of our replies but you don't give any indication of whether you understood the contents of those replies. We can only get further if you are prepared to continue a conversation.

You asked a question about why Blackbird doesn't go faster when at an angle to the wind. I asked you to consider the direction of thrust of a propeller (any propeller, not just the one on Blackbird) in relation to the plane of rotation of the blades of the propeller. I explained that your first reply didn't answer the question. Do you want to continue that conversation?

 

[ThinAirDesigns]

When MichaelC has been trying to educate you for near two years and you've run away every time, the ignorance is clearly willful.

I rest my case.
JB

 

[ThinAirDesigns]

It has been suggested by several in this very forum that spork and Humber might be the same person.

It should be noted that only one person on this thread has gone out and pretended to be humber (or been humber, depending on what definition is chosen). RCP (ReCursive Prophet) is this person.

He did this (posting as humber) in an attempt to fan the flames and keep the humber chaos alive when "humber" took an extended break a while back.

RCP throwing out conspiracies regarding the identity of humber is a real hoot when to keep his favorite show alive he'll actually go out and secretly post as humber.

Turns out as you can see -- RCP knows 'who humber is' better than anyone.

JB

 

[windgrins]

Thanks for this post, Mender

http://forums.sailinganarchy.com/in...faster than the wind and the mythbusters&st=0

Thanks for posting this Mender, some of the explanations are really good here. I hadn't seen this site before this.

It is interesting to note how many sailors on this forum don't have a clue how a sailboat works with reference to their sails and keels. That doesn't mean they are not good sailors but it does make one wonder how they get the best out of their boats in novel situations. There are lots of pilots like this too but at least they have to go through a relatively rigorous training requirement for the FAA.

Of Note: The space shuttle Endeavour on its final flight today at 3:47 PM EDST. It's been a fine ship!

ETA-It looks like launch is scrubbed for today for at least 72 hours due to a bad APU fuel line heater thermostat! Too bad!

Regards,

WindGrins

The formerly perky

 

[Dr. Keith]

Thanks much JB (oops, I mean for Dr. K!)

Thank you.

Getting a bit too perky, if you ask me.

 

[humber]

It should be noted that only one person on this thread has gone out and pretended to be humber (or been humber, depending on what definition is chosen). RCP (ReCursive Prophet) is this person.

He did this (posting as humber) in an attempt to fan the flames and keep the humber chaos alive when "humber" took an extended break a while back.

RCP throwing out conspiracies regarding the identity of humber is a real hoot when to keep his favorite show alive he'll actually go out and secretly post as humber.

Turns out as you can see -- RCP knows 'who humber is' better than anyone.

JB

Nothing, but nothing will save your "record".

 

[humber]

When MichaelC has been trying to educate you for near two years and you've run away every time, the ignorance is clearly willful.

I rest my case.
JB

I rest my case carpet bag.

 

[Dr. Keith]

(Did you see the one of spork palming a basketball after Humber said he had dainty hands? One of my favorites.) I've read everything on the hundreds of pages here, at RDF, and TR.

Well then, either you can't see the forest for the trees or your focusing more on the actors than the words of the play. I mean who gives a **** about spork palming a basketball in this discussion: you and humber. Think about that.

There's a lot you haven't seen though, Doc. Some of it might even make you wonder a bit about what's going on.

You know this sounds a bit like Trump talking about his investigators in Hawaii, right?

If you have evidence that something doesn't work then present it. Stop jaqing off.

You know who George Burdell is, right?

No, but 20 seconds later I know that it is an open joke. A prank known by a large community to be a prank. How is that relevant?

I can see possibilities for that crew with 2 very different plot lines. A well orchestrated hoax to show how gullible physicists can be

Well, not just physicists. I'd venture to say over 90% of the people with a scientific inclination who have taken the time to try to understand the project come away with a sense of respect for what they have done here. That the 10% who still don't grasp it are so unclear as to why it doesn't work speaks more of them than the project.

, or one of keeping a topic going by creating adversaries.

Kinda expensive to build a carbon fiber cart just to troll bait. Is that really what you think is going on here?

Note that neither spork or jb posted any of the links I requested to back up spork's claim about sites where there were 20 deniers against just them. Every discussion I've seen has been like here, where the vast majority agree with them.

Note that no coherent argument has ever been presented as to why this actually doesn't work. Note also that a working prototype has been tested and documented and I have not seen a single explanation for how that prototype could have achieved those speeds other than the one promoted by the "carteers." If humber is really on to something, or if you have some real reason why this cart can't work as advertised, why can't any of you express that in a clear way?

All I've seen in my limited time here is humber's fractal ignorance and your jaqing off. Way to represent the skeptical side of things.

And windgrins is a witch. She turned me into a newt.

 

[humber]

(Did you see the one of spork palming a basketball after Humber said he had dainty hands? One of my favorites.)

It was Christoph( Harold) who made the remark about the hands.
My favourite, apart from JB's car park tantrum, is "counter-rotation".

You know who George Burdell is, right? I can see possibilities for that crew with 2 very different plot lines. A well orchestrated hoax to show how gullible physicists can be, or one of keeping a topic going by creating adversaries.

Way too much credit there. RP. No hoax. They really believe in Leprechauns.

 

[humber]

No, but 20 seconds later I know that it is an open joke. A prank known by a large community to be a prank. How is that relevant?

Manipulation of identity.

 

[Dr. Keith]

[qimg]http://i54.tinypic.com/2gv0kew.png[/qimg]

A.T.: That is a lot to have in one shot and yet it lays out the realities of the situation so well. Thanks for putting this together.

RCP: This is what you present when you have a cogent argument. If you know what you are talking about then the graphics are far easier to develop.

Humber's lack of a cogent argument is based on two problems, only one of which is his communication skills.

 

[zooterkin]

Nothing, but nothing will save your "record".

I rest my case carpet bag.

Manipulation of identity.

Isn't there some data analysis you should be doing?