blades from china magnet

[mike heckler]

I just purchased 110" diameter blades and hub from china magnet, through their ebay store.

Very thick at the tip area,, 3/4"

Hollow core.

Holes in hub drilled .060 further apart than holes in blades. Company says just re-drill the holes bigger in the hub and the screws will then fit.

Front (facing wind) side of blades convex, except for last 1/3 of trailing edge.

Company says 1000's built, 600 watts at 18 mph.

I will have to take the wind generator down, and put the home made wooden blades back on.

These things just start to turn at 13 mph.

The only thing nice about them is when you look at them from the front.

Their advertising is a lot more convincing than their performance.

3 days wasted, re-drilling, painting, assembling, lowering tower, installing blades,balancing them etc. etc.

Has any one else had any experience with these blades?

[windstuffnow]

  Hi Mike,

     I just did the same thing only with the smaller blades.   I purchased the 6.8ft blades to try out on my 500 watt turbine.   It's been up for 3 years now and I started hearing some mild grinding in low winds, figured I'd better replace the bearings.

    Anyway, It all went back in the air on Saturday just as the winds were picking up.  So far they match the performance of my hand carved blades in lower winds.   We havent had any winds above 20mph lately so I don't know how they do in higher winds.   In a 20mph wind its doing around 420 watts.  

     I'm a little leary of the fiberglass construction.   Even though I've painted them they usually don't stand up to UV for a long period of time.   We'll see...

     I was thinking of getting the larger blades for another project but if your having problems with start up I may rethink my plans.  Are you using a dual rotor or motor conversion?

.

[RogerAS]

WSN,

You wrote;

"   I'm a little leary of the fiberglass construction.   Even though I've painted them they usually don't stand up to UV for a long period of time.   We'll see..."

Have you experimented with the stuff they use in airplane modeling that heat sticks and streches? Goes by a couple names but is mylar lookin' stuff that shrink fits balsa frames n such. Would that maybe work as a UV blocker, or be too expensive? Seems to me it outta keep the majority of the UV blocked. If coated with another uv blocking layer of finish over that the blade (or other glass-like composite) should last much longer. Besides, that stuff comes in a rainbow of colors and some neat metallics too. One could sure make a flashy turbine!

Anyway, just a passing thought, and as always worth every electron!

:-)

[s4w2099]

I use the 8.5 ft version and I did had some trouble fitting them into the provided hub but I cant deny that they are performing very well in my particular case.

[mike heckler]

Dual rotor,, 3 blade wood 8'10&1/2 " max out 30amp star, 60 amp delta

Were your blades really thick at the tips, hollow, and convex on the wind side?

[windstuffnow]

Hi Mike,

   They have a mild concave at the root end, the tips are a bit thicker than I would usually make them but didn't seem like anything to be concerned with.  I didn't drill them for the bolts they sent, I used some 3/8" bolts that seemed to fit quite well through all.  I did machine the hub from a tapered fit to a straight shaft with a key slot.   Other than that it does 30 amps in a 20mph wind with the dual rotor.  Seems to fly in pretty low winds.   Overall it does about the same as the hand carved blades.  Almost doesn't seem worth carving them for that price.    

    I wonder what the differences are, do you have any pictures of your blades?  Maybe some root end shots and tip shots...

.

[s4w2099]

The difference that Ive noticed is that they are rather flat. For that reason they do need a little harder wind to start. But after they break they will speed very very fast.

[windstuffnow]

  I coated them with UV protectant and a surface coat.  Even then the glass will weaken over time when exposed to the elements.  The life span of a composite aircraft if left outside ( unhangered ) is about 5 years.   I've seen them come apart after some neglect of being left outside.  Not a pretty site... those type of aircraft kits demand an onboard balistic parachute with special frame attatchments.  Hopefully your not in the path of any part of the airframe that has shreaded in flight. Nasty stuff!

.

[Mary B]

I have a set of the 6'8" and just testing them on a screwdriver shaft they picked up a lot of speed in 6mph winds. Will see what happens under load when I finish the alternator.

[mike heckler]

Do you mean the surfaces are flat?

[s4w2099]

No, the pitch angles are very flat thus making it a bit harder to spin in lower winds. After it breaks loose its great though. I have the 8.5ft or 102" inches

[Mary B]

Suzlon is building huge fiberglass blades about 75 miles from me. 120 foot+. It is annoying at times that people jump on any suggestion other than wood for blades.

[wdyasq]

You have any idea how much time and money was spent on the engineering of the 'huge fiberglass blades' Suzlon is building? Any idea of the cost of a mold?

On 'homebuilt' mills one can simply over-engineer with brute force and ignorance. Once things get to a certain size, it may make sense to design and engineer composite blades. I can all but guarantee the engineering costs of a small set of blades will exceed what most posters here spend on tower, mill, batteries and a few gusts of wind.

"It is annoying at times that people jump on any suggestion other than wood for blades."

It is also annoying to see posting of 'how to do' things by folks who have no experience and little or no education in the discipline they are recommending folks spend money on.

Ron