TheBackShed.com

Forum Index : Windmills : Shape of PVC blades?

Author

Message

mahela007

Newbie

Joined: 06/07/2008
Location: Sri Lanka
Posts: 29

Posted: 09:16am 28 Jul 2008

Copy link to clipboard

Print this post

Hi.. I made some PVC blades for my windmill. (Its still my first shot at making a working windmill.)
The blades seem to be fine when i look at them form the top. However when I look at them form the front.. that is from the side of the leading edge the last few centimeters of the blade seem to be tilted in the opposite direction to the rest of the blade. Is this ok? or should I try to bend it back? I hope the photographs will help you guys to see the problem.
http://www.flickr.com/photos/9937638@N02/

they are relatively high resolution so you can zoom in quite a bit

how come its not very windy where i live???

windlight
Guru

Joined: 03/03/2007
Location: Australia
Posts: 331

Posted: 07:20am 29 Jul 2008

Copy link to clipboard

Print this post

I trialed PVC blades once, and found they bend conciderably and can hit the tower, others have had sucess. The tips will take on their own shape when flying, I would not attempt to shape them.

allan

"I like this place and willingly could waste my time in it" - (Act II, Scene IV).

CraziestOzzy

Senior Member

Joined: 11/07/2008
Location: Australia
Posts: 135

Posted: 10:03am 29 Jul 2008

Copy link to clipboard

Print this post

I know very little about wind dynamics on a fan, but know that if you heat the pvc with a hot air gun (be careful!!!) you can bend it into any shape you want without weakening the relative strength of the pvc as opposed to cold bending it.
You can look into the pros and cons of an upwind or downwind blade/generator system if there is a reasonable chance the blades may flex too much and hit the tower.Some dimensions of your blade would help a guru on this matter advise you into the right direction...as that tip to me looks a bit narrow to what I have seen from others.
Cheers.Edited by CraziestOzzy 2008-07-30

http://cr4.globalspec.com/member?u=25757

http://www.instructables.com/member/OzzyRoo/

WooferHound

Newbie

Joined: 05/06/2007
Location: United States
Posts: 3

Posted: 01:40pm 29 Jul 2008

Copy link to clipboard

Print this post

When you mount the blades to the hub, just shim it up on one side so the whole blade twists to the correct angle

W o o f -={(
The wind in Alabama doesn't Blow , it Sucks . . .

Dodgeman

Newbie

Joined: 19/07/2008
Location: United States
Posts: 33

Posted: 02:00am 02 Aug 2008

Copy link to clipboard

Print this post

I'm no expert here but what I have done on mine is cut them off at the point where the reversal occurs on the blade, so as to have your leading edge and your trailing edge fairly even/level at the tip of the blade, like was said, It appears the tips of your blades may be a bit too narrow, so shortening slightly them wont hurt you too much. (possibly to about an inch or so to the right from your "leading edge arrow" in pic #2.

I have also decided not to cut the smaller mounting area at the "hub end" of the blade, I have had them break off in high wind, which landed me a set of shorter blades after cutting them off.

I think the strength is comprimised when "notched" for mounting to the hub and with the extra forward facing part of blade near the center not cut away, I havent noticed much (if any) difference in how it spins.

You can see the pics of my little backyard built pvc bladed mills in this thread - not very clear pics of the blades but they may help http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?T ID=1167&PN=1

If nothing else, I have learned that pvc blades are cheap and easily replaced, Also while building mine, I used a cheap hand plane to help create proper looking leading and trailing edges by shaving the edges down.

feix62k

Newbie

Joined: 30/07/2008
Location: Australia
Posts: 36

Posted: 01:51am 24 Aug 2008

Copy link to clipboard

Print this post

anbody got any links or pics of blades for the f and p windmill pvc or wood ,how do I get back to the fisher and pakel windmill design/plan site Ive lost the link thanks felix

dont the days seem lank and long when nothing gos right and everthing gos wrong

Print this page

To reply to this topic, you need to log in.