7.5m Wind Genny Anyone?

[jimovonz]

I have got my hands on three x 3.6m (11'10") blades from a helicopter. These blades have exceeded their rated hours but are otherwise in perfect order. They have a symetrical aerofoil, constant chord width of 175mm (just under 7"), weigh just under 10Kg (22 pounds) each and the pitch varies approx 15 degrees from root to tip. These were the smallest main rotor blades I could get. Also available were tail rotors at up to 1.2m long each but with rather large chord width, along with much larger main rotors up to 24ft each (48ft diameter!). The warehouse was full of the things!

The engineer I spoke to said that it should be straight forward to cut the blades down in length and that doing so would not compromise the structural integrity.

Anyone have any comments on how successful a wind genny based on these blades might be?

Blade Full Length:

Blade attachment:

Tip Prifile:

Twist:

[nothing to lose]

I don't know how well those will work for a gennie, but I want a set or two!

How much were they, and where would I look for some?

I am sure they could be useable, either as is or modified some.

[jimovonz]

They cost me nothing more than an hours drive to go and pick them up! I have a friend whos family owns and operates a buisiness based in Rotorua, New Zealand. They have over 30 in their fleet. Certain components have a limited life due to fatigue and are usually thrown away when they expire as it is illegal to use them beyond. I figure that the maximum hour rating attached to these components is calculated such that when a component expires, there is something less than 1:1000 chance that it will fail in normal use (I can't imagine 1 in 1000 helicopters falling out of the sky!). These particular rotor blades under 'normal' use are driven by a 1200hp turbine and frequently reach a tip speed just below the speed of sound. This is the equivalent of a 7.5m wind turbine doing 800+ rpm in a sustained 90mph wind! (and incidentially, producing a something similar to 1200hp) I think that cut down some, in use as a wind turbine with a reasonable furling system, these blades have some life left in them yet!

[Dan M]

I've been looking around a lot for "timed out" main rotor blades.

Everyone I've spoken to politely says NO #@%#@%$ WAY,  Even after I explain that I am experimenting with wind power, NOT attempting to make a home-brew flying machine.

I think the secret is having a friend in the business who isn't worried about the liability.

If you're looking at helicopter repair facilities don't bother with Enstrom.  Their blades don't "time out".  Useability for Enstrom blades is strictly based on condition.

Good Luck,

-Dan M

[hvirtane]

I think that they will

work quite well as they are.

Several possibilities are

coming into my mind.

You might even make a darrieus of

them, because they are very

strong things. You could

put them skewed so that you

could take an advantage

of the twisted blades.

(Please see my recent post

of a VAWT idea.)

You might also cover

the blades partly

with for example

polyurethane and some

kind of plastic cloth

to make the airfoils

asymmetric.

You can also use

them as they

are with a VAWT.

As they are very strong

you might use them

as they are instead of

cutting them shorter.

Here the thumb rule

among the old guys with

big wind turbines is that

the rotor axle thickness

should be at least 1/100

the diameter of the wind rotor.

So for a 7,5 m diameter wind

rotor your rotor axle should be

at least 7,5 cm thick.

- Hannu

[hvirtane]

I wrote:

You can also use

them as they

are with a VAWT.

I'm sorry for a mistake,

I meant:

You can also use

them as they

are with a HAWT.

- Hannu

[jimovonz]

Hmmm... Keep them whole.... An easy 5kW in a 20mph wind... I like the sound of that!

Would take a whole lot of magnet to make 5kW at 150 rpm - better start saving up!

[nothing to lose]

So, how much to ship a set of 4 to MO. USA ??

Good luck! I think they'll fly

[domwild]

I have been told there is a previous post on this forum of a Siberian mill using chopper blades but I have never searched for it myself.

dominic

[Virgis]

Hi,

let You look my posting "Abiggest homebrewed wind turbine in Lithuania" posted 2004.08.09. I hope You will find an answer to Your question.

Regards

Virgis

[TomW]

Virgis;

I tracked down the link to that story its over here:

http://www.fieldlines.com/story/2004/8/9/44346/84677

Cheers.

TomW