Blade calculator thingy

[nanotech]

I tried searching, and searching some more.  But my search abilities just don't seem to be good enough.....

Someone at one point had a neat little blade calculator program that allowed you to input the length of the blade and it would tell you the pitch at the root and tip for you.

Anyone remember that?  And if so, got a link to the proggy?

Pretty please?  

[richhagen]

There are a few out there.  Ed Lenze has one on his website at WWW.Windstuffnow.com I think he charges $5US for his, there are some basic ones for free on the web, but at the moment I am not turning one up.  There is also a very nice page written up by DANB on blade design on this very site as well, and of course, Hugh Piggot's books cover the subject in great detail, even explaining the formulas and theories that would enable one to generate there own.  Rich Hagen  

[Flux]

Yes and Hugh has the blade design spreadsheet.

http://www.scoraigwind.com/index.htm

Look for blade design spreadsheet

Flux

[DingBat]

http://www.alton-moore.net/wind_calculations.html

Is the proper url for Alton's Calculator.

-- DingBat

[willib]

and there is also one that uses feet and inches

http://www.warlock.com.au/wind.htm

third one down.

it is a very good one imho..

[David HK]

The interesting thing about Hugh Piggots blade design calculator is that if you fill in the basic parameters for one of the three prop designs listed in his magazine (2005 How to build a wind turbine) it does not generate the same data contained in his magazine.

I was playing with it a few hours ago and despite changing the parameters could not find the same dat as that published. Start at page 5 and enter data for a blade of 1.2 m (2.4 metres dia) and then compare the station widths with that shown on the screen and that published in the book on the same page.

Or have I made a mistake?

Dave HK

[David HK]

Just played with Alton's calculator and entered exactly the same parameters as I did for the Piggot calculator. The generated output data from Alton's calculations comes close to, but does not match Piggots.

Which one is to be believed?

Perhaps someone else could try and then let us know if my own observations are correct.

Dave HK

[richhagen]

They are all approximations.  Fortunately blades are rather forgiving things.  If you entered every possible variable, and obtained an exact answer, well, you can't, because no perfect model exists, but if you could, you would probably only obtain a slight improvement.  Adding 10% more to the blades length would probably give more power.  

Joke -

What's the difference between a good blade and a perfect blade?  Answer = 5%

- the good blade might have to be about 5% longer to get the same power.

Don't worry, I won't quit my day job.  Well not yet anyway.  

That is because the 5% longer blade sweeps 10 and a quarter percent more area which makes up for quite a bit of difference in efficiency in energy conversion.  

(I'm sure we could mess up a blade good enough to make the required difference in length bigger)

Rich

[Flux]

Dave

I have just tried the 2.4M blade tsr7 and there are small differences in the chord width of up to 3 mm , which is insignificant.

The largest change I noticed was that it predicted a drop at the tip of 1mm instead of 2 and this I am sure is due to the way the spreadsheet rounds up the numbers.

These things are just a guide, you will get different answers if you enter different values for the angle of attack and lift coefficient.

The things are also affected by the type of aerofoil you use, cambered aerofoils would need a different angle.

Flux

[David HK]

Richagen and Flux,

Thanks indeed for the comments. I simply ask the question because I like to pay attention to detail. If you miss out or lose the detail on many things in life especially engineering and such like, then much time and work can be lost.

I am sure your answers will provide useful guidance for those that take the time to read this thread and understand the contents in the future.

Regards,

Dave HK