Author Topic: Blades  (Read 3172 times)

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MelTx

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Blades
« on: June 14, 2005, 08:58:19 PM »


  I bought the book and carved 69,000 board ft. of lumber and the blades still wont turn.I can put three old scrap boards of different sizes on the rotor and they will at least turn. but not the ones I lovingly carve and sand & rub oil on for a week.There is something that is missing[dont say that].I must be turning them the wrong way or something.I know that a lot of pictures have been displayed and I tried to look at all of them.Would someone be so kind as to post some photos that show all sides of the blades, top and bottoms and ends......Thank you for your support.

                                                                MelTx
« Last Edit: June 14, 2005, 08:58:19 PM by (unknown) »

Norm

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Re: Blades
« Reply #1 on: June 14, 2005, 03:52:59 PM »
  Perhaps if you were to send a few photos of

your blades some one could tell you what you are doing wrong...ever really test them on the back of a pick-up at 35mph?

                  I think even cast iron works

fairly well at that speed...(tongue-in-cheek humor)

                     ( :>) Norm.

 Hey! know how you feel! Where I'm at.. beautiful

carved blades would work well with the deer antlers on the west wall...if I had the deer antlers...that is...LOL!  
« Last Edit: June 14, 2005, 03:52:59 PM by Norm »

MelTx

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Re: Blades
« Reply #2 on: June 14, 2005, 04:43:20 PM »


  No sir cant send any pics of my "blades"..they are no longer in this world.I said the magic Herculese chant and flung them into orbit around pluto,where they belong......I was a tool & die maker in real life...but these things are getting past me.If I saw one in person there is no doubt i could make one.There seems to be a wave but its hard to tell in the pic i saw the shadows play tricks. Thank you for your help.

                                                   MelTx
« Last Edit: June 14, 2005, 04:43:20 PM by MelTx »

richhagen

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Re: Blades
« Reply #3 on: June 14, 2005, 05:36:21 PM »
What data do you have on the blades that you carved.  Do you have any pictures?  69000 feet of board lumber?  sounds like a lot.






photo of a small blade set I made a while back






here is the airfoil on that one looking from the end


the twist was not ideal, but this was basically very similar to DANB's post here, just drastically scaled down.

http://www.otherpower.com/otherpower_wind_tips.html#blades

Hugh Piggot has a large amount of data on blade theory on his website.  Take a look at the blade theory pdf file.

http://www.scoraigwind.com/

Ed also has a section on blade design at

http://www.windstuffnow.com/





this is a plot I made and posted to my diary the other day using a program I wrote, which incorporates some of that theory for designing blades.  I havn't actually used it to build a working blade yet though.  The names of the curves correspond to the distance out from the center of the rotor.  this was for a TSR 7 blade carved from a 2 by 4 with a 26 inch blade, or radius.  


I don't know if the above will help you, but blades don't have to be perfect, they just loose a little performance the farther from ideal that they are, and since all designs contain compromises, an imperfection regarding the twist of the blade that hurts performance a high rotation speeds, might wind up helping with startup in low winds.


A simple mistake that I could see happening would be to reverse the airfoil profile on the blade.  such that the front of the airfoil was used as the trailing edge.


Anyway, post more info if you have it, and someone here can likely help.  Rich Hagen

« Last Edit: June 14, 2005, 05:36:21 PM by richhagen »
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richhagen

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Re: Blades
« Reply #4 on: June 14, 2005, 05:40:55 PM »
Meltx, send me your mailing address.  Rich
« Last Edit: June 14, 2005, 05:40:55 PM by richhagen »
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TomW

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Re: Blades
« Reply #5 on: June 14, 2005, 06:10:55 PM »


 69000 feet of board lumber?  sounds like a lot.


Well, every Texan I ever met had a tendency to "overstate" things.


T

« Last Edit: June 14, 2005, 06:10:55 PM by TomW »

RP

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Re: Blades
« Reply #6 on: June 14, 2005, 06:50:08 PM »
Just to add a little context to Richhagen's post above:  The graph of wing cross-section above is for when the wind is coming from the bottom of the chart and the blade is moving to the left.
« Last Edit: June 14, 2005, 06:50:08 PM by RP »

DanOpto

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Re: Blades
« Reply #7 on: June 14, 2005, 08:26:40 PM »
Here are some profiles and angles for an 8 foot blade.

A 70 inch blade would be very similar.

The profile is similar to the S822 blade that was designed for small wind generators.

(The labeling of the files says S222 but it should be S822

The design is supposed to stall in high winds, which helps limiting overspeed.

(Thats what I read. )


The blade is set up for a 2 by 12 piece of lumber with thickeners glued at the root.

Maximum width is 11 1/2 inches.

Blade shape below 26.3 inches would be mainly thick and rounded for strength and fastening to the hub.

The blade is made with the inner section limited to the width of the 11 1/2 inches

http://www.greatparrots.com/Windgenerator/S222_8_foot_26.3_inches_printable.pdf

http://www.greatparrots.com/Windgenerator/S222_8_foot_38.2_inches_printable.pdf

http://www.greatparrots.com/Windgenerator/S222_8_foot_44-7_inches_printable.pdf

http://www.greatparrots.com/Windgenerator/S222_8_foot_57_66%20inches.pdf

http://www.greatparrots.com/Windgenerator/S222_8_foot_tip.pdf


The airfoils have the 0 degree line passing through the center.

You can use that to align the blade to your work table.

Glue the pattern to some plywood.

Cut out the airfoil pattern with a band or jig saw..


If anyone uses this pattern, I would enjoy if you posted your results.


Thanks




http://wind.nrel.gov/designcodes/papers/NREL%20Airfoil%20Families%20for%20HAWTs.pdf
« Last Edit: June 14, 2005, 08:26:40 PM by DanOpto »

richhagen

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Re: Blades
« Reply #8 on: June 15, 2005, 12:50:10 AM »
Oh, good, because I had this picture of small pieces of wood the diameter of toothpicks, all bundled together to make a set of blades or two.  I was wondering if they were all laid end to end if they would even come close to that many feet.  Rich
« Last Edit: June 15, 2005, 12:50:10 AM by richhagen »
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phil b

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Re: Blades
« Reply #9 on: June 15, 2005, 07:12:01 AM »
Hi DanOpto, can you explain what the column headings in the design specifications chart mean? Also the "s" designation. I need an airfoil book for dummies. Thanks!
« Last Edit: June 15, 2005, 07:12:01 AM by phil b »
Phil

DanOpto

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Re: Blades design headings
« Reply #10 on: June 15, 2005, 09:01:33 PM »
I do not know the fine print on the headings.

I missed out on engineering a few years ago.

The most information I know is in the Pdf file that is linked at the bottom of the airfoil post.

It explains the development of the airfoil.

I believe the exact data to form the airfoil is patented, so there is not exact data available to reproduce the exact design.

Thankfully, they posted the picture which is good enough for me to make a similar shaped blade.

The S822 designation appears to be the numbering that the wind generator designers chose the list their series of wind generator blades.


Best wishes for your build

« Last Edit: June 15, 2005, 09:01:33 PM by DanOpto »

DanOpto

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Re: S822 information
« Reply #11 on: June 16, 2005, 06:13:26 AM »
http://www.nrel.gov/docs/fy05osti/36342.pdf

Here is another research paper on the S822 and 823 airfoils.

These include dimensions.


Also

http://wind.nrel.gov/amestest/BladeDesign.pdf

This is an interesting link on research on small blases.

« Last Edit: June 16, 2005, 06:13:26 AM by DanOpto »

ghurd

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Re: Blades
« Reply #12 on: June 16, 2005, 07:33:27 AM »
The 4 blade set in the photos spin like crazy.

G-
« Last Edit: June 16, 2005, 07:33:27 AM by ghurd »
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finnsawyer

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Re: Blades
« Reply #13 on: June 19, 2005, 09:10:10 AM »
Make sure the flat side of the blade faces the wind, and the curved (convex) side away from the wind.  You also need some angle of attack (the angle between the plane of the blade and the direction in which it moves). In other words make sure that the leading edge (the fatter edge) of the blade faces a few degrees into the wind.  This should give you the rotation you seek.
« Last Edit: June 19, 2005, 09:10:10 AM by finnsawyer »