Author Topic: Blades  (Read 1242 times)

0 Members and 1 Guest are viewing this topic.

FishH2o

  • Newbie
  • *
  • Posts: 12
  • Country: us
Blades
« on: July 06, 2017, 07:52:18 AM »
Well, guys im very new to this so I wanted to say Hello and ask a couple questions. I originally started out wanting to make the otherpower 20ft turbine but i believe i bit off more then i can chew. I have one blank done that is 10ft long 13.5 inches at the widest and 6.5inches at the tip. Since i screwed up my measurements and didn't end up with the 18 inches they called for I thought heck no worries build the 17 foot.  So my question is will the .5 inch that im missing for the 17 foot turbine be that much of a difference?

FishH2o

  • Newbie
  • *
  • Posts: 12
  • Country: us
Re: Blades
« Reply #1 on: July 06, 2017, 10:42:56 AM »
Or can i still go with the 20 foot diameter and use it as 13 inches at the root and 6.5 at the tip??


SparWeb

  • SuperHero Member
  • ******
  • Posts: 3307
  • Country: ca
    • Wind Turbine Project Field Notes
Re: Blades
« Reply #2 on: July 09, 2017, 06:22:53 PM »
I guess you mean that you started with carving the blades and haven't been working on the matching alternator.  Good, at this point a change of plan won't hurt as much.

I don't have a copy of the 17ft or 20ft plans, so I don't know specific measurements to help you with.  I'll just speak in general:
Considering the strength of the blade root needed to withstand all the radial forces of a spinning blade, plus the bending it gets from the gyroscopic effect, I would not be keen to use a blade with 2/3 the root strength. 

If your goal was a 20-ft turbine then don't be afraid of re-working a few parts to make sure you've done them right, esp if it's just one blade.
Carving the blades is a lot of work but (to me) it's the most rewarding.  I actually made 4 blades every time I have carved a set, exactly so that I could screw up one, pick the 3 best.  Having a blade left over can also be handy as a "conversation piece".   :)
Switching to the 17foot plan isn't a bad strategy, either, but are you sure that's what you really want? 
No one believes the theory except the one who developed it.  Everyone believes the experiment except the one who ran it.

System spec: 135w BP multicrystalline panels, regulated by Xantrex C40, DIY 8ft diameter wind turbine, regulated by Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024

FishH2o

  • Newbie
  • *
  • Posts: 12
  • Country: us
Re: Blades
« Reply #3 on: July 10, 2017, 11:05:30 AM »
SparWeb,

Thank you for the reply but I decided not to go that route. I decided to go with the 10ft route since its well documented in the book and online. That will be plenty until we move top our property. Thats when I will need a 20ft.

SparWeb

  • SuperHero Member
  • ******
  • Posts: 3307
  • Country: ca
    • Wind Turbine Project Field Notes
Re: Blades
« Reply #4 on: July 10, 2017, 04:10:28 PM »
There ya go.  Sometimes you just gotta know when you were just too ambitious.
Looking forward to seeing progress (good and bad!)
No one believes the theory except the one who developed it.  Everyone believes the experiment except the one who ran it.

System spec: 135w BP multicrystalline panels, regulated by Xantrex C40, DIY 8ft diameter wind turbine, regulated by Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024

Boondocker

  • Full Member
  • ***
  • Posts: 190
Re: Blades
« Reply #5 on: July 10, 2017, 04:40:12 PM »
Also you will learn much flying a 10 rotor first. 
-     What are the real wind characteristics for the site
-      Is your tower adequate 

 boondocker

finnsawyer

  • Hero Member
  • *****
  • Posts: 1556
Re: Blades
« Reply #6 on: July 12, 2017, 11:15:39 PM »
     Your blade responds to the air flow past it {whatever that is} as an airfoil.  It also responds to the pressure drop {gradient} from front to back as a slab of wood.  That also creates lift {see those water pumpers, for instance}.  Its not clear which effect dominates.  Bottom line: Do not worry about the width near the root.  Do whatever you like.  Nobody knows what is happening anyway.  They just know some torque and power is produced. ;D