Making small GRP Wind turbine blades

Though making the blades isn't CNC related, just the mould is, I thought I'd post this as I'm sure there will probably be people here who know more about using polyester resin / glass fibre than I do.

This is my first attempt at making anything with fiberglass, except a couple of stators for the wind turbine which is just a very simple casting, and some small sheets as a test for strength.

First I made these two moulds on my CNC router:

Attachment 3882
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Attachment 3886

The blades are 700mm long, tip speed ratio 7.
I've coated the mould in a random tin of furniture wax we had lying around but were never going to use. Not got any pictures of that.

To be continued...

This is the blade I made a few days ago, got my sister to help with laying up the resin/glass:

Attachment 3893

Attachment 3894

Attachment 3895

It went reasonably smoothly. The blade came out of the moulds easily, however it had collapsed a little in one area. I've since built that back up with more resin/glass and sanded it a bit, so now you can't tell. A bit of wax came off the mould with the blade so I'm currently waiting to get some more before I can make the next blade.

The blade itself seems strong, it doesn't bend much except near the tip. I might fill it with polyurethane foam just to make sure.

Oh and thanks to 'Chip' for giving me some resin - I used a little of it here since it said on the container that it did not require gel coat.

Now I've got to paint it - any ideas where to start with that? Some sort of primer then white paint I suppose. I think the spray paint used on cars would stick?

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Originally Posted by Jonathan

Now I've got to paint it - any ideas where to start with that? Some sort of primer then white paint I suppose. I think the spray paint used on cars would stick?

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If you have compressor and air gun you should use 2K primer (very easy to sand), then 2K gloss paint (high gloss and durability).

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Originally Posted by wiatroda

If you have compressor and air gun you should use 2K primer (very easy to sand), then 2K gloss paint (high gloss and durability).

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I do have an air compressor with the filter things on it for painting. Please could you link me to the paint and air gun you're thinking of? Where's the best place to get it?

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Originally Posted by Jonathan

Where's the best place to get it?

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I used to buy paints off ebay or from my local Jawel Paints paint shop in W-ton (they are on e-bay as well). Try to buy paint+activator deal. You will need 2K thinner as well. For a small width blade I would recommend touch-up spray gun for example: ( http://www.machinemart.co.uk/shop/pr...l-touch-up-gun or
http://cgi.ebay.co.uk/GRAVITY-FED-MI...item53e6c9bfe1 ). Remember this paint not only dries , but hardens as well so mix no more than you need and clean tools straight after painting (with 2K thinner).

2k paint is poisonous so make sure you use the right face mask and gloves as it can be absorbed though the skin.

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Originally Posted by h4ppy-chris

2k paint is poisonous so make sure you use the right face mask and gloves as it can be absorbed though the skin.

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That's why I had hesitated to reply to the above posts after reading up on it. Would just doing it in the garden be enough to stop the fumes getting me?

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Originally Posted by Jonathan

The blade itself seems strong, it doesn't bend much except near the tip. I might fill it with polyurethane foam just to make sure.

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If you do, make sure you put it back in the mould while it sets otherwise the resin may cause it to bulge.

Are you going to be making many of these? If so there's some ways you can make the process more efficient.

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Originally Posted by FatFreddie

If you do, make sure you put it back in the mould while it sets otherwise the resin may cause it to bulge.

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Yes I was going to do exactly that.

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Originally Posted by FatFreddie

Are you going to be making many of these? If so there's some ways you can make the process more efficient.

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I might be - depends how well these work. What are you thinking of? I guess I could use prepreg, but I'm not sure where to get that. Not really sure what else without adding significantly to the cost, other than using thicker cloth to reduce the number of layers.

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Originally Posted by Jonathan

I might be - depends how well these work. What are you thinking of? I guess I could use prepreg, but I'm not sure where to get that. Not really sure what else without adding significantly to the cost, other than using thicker cloth to reduce the number of layers.

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The easiest one is to put a good finish on the mould and use a gel coat, this should remove or at least minimise any finishing. You could also use an inflatable core to put the layup under pressure while it cures, this should improve the finish and the glass / resin ratio. Have a look at vacuum bagging on 't internet.

Prepreg is great if you've got an autoclave but not really necessary for this application - it's more for situations where you need precise control over the material and best possible weight / strength ratios.

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Originally Posted by Jonathan

That's why I had hesitated to reply to the above posts after reading up on it. Would just doing it in the garden be enough to stop the fumes getting me?

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yes thats ok mate but still use the correct mask and gloves.

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Originally Posted by h4ppy-chris

yes thats ok mate but still use the correct mask and gloves.

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Seems a lot of effort - Plasti-Kote (from B&Q etc) works well and isn't too toxic.

http://www.plasti-kote.co.uk/Product/pcode---4181

Can you still get 2pack?

There's been a big shift in the paint shop area away from most things toxic, towards water based synthetic paints.
Only exemption I can think of is the one for cellulose paint, but that's only meant to be for classic vehicle use.

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Originally Posted by FatFreddie

Seems a lot of effort - Plasti-Kote (from B&Q etc) works well and isn't too toxic.

http://www.plasti-kote.co.uk/Product/pcode---4181

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I've seen those paints in a few shops. I might go for that since though the method suggested above is better, however I intend to use a white gel coat for future blades which won't need that paint. I didn't use a gel coat for this blade due to cost.

Sadly I've not got an autoclave :heehee:

The blades work! Not that I ever doubted them :heehee:

The mass of the two blades when I made them was only 2 grams off - complete fluke that. The centre of mass however was quite a bit off. I spent a bit of time balancing them but they're by no means perfect. This caused huge vibrations.

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According to the frequency meter the rotor did over 800rpm at times - that means the tips of the blades were doing over 100mph! I need to be careful... next time I'm going to balance them properly and stiffen the tower up. Might have to use guy wires at full height.

I'll upload a video soon.

Here's the video of the blades working:

http://www.youtube.com/watch?v=FJ1yr...=youtube_gdata

As you can see I've not painted them yet. I intend to do so the next time I put the wind turbine up.

I just need to find somewhere to put my 3m diameter variable pitch wind turbine next...not got enough space at home.

Great job Jonathan. Are you going to attach to it some kind of generator? What power output do you expect ??

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Originally Posted by wiatroda

Great job Jonathan. Are you going to attach to it some kind of generator? What power output do you expect ??

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Thanks... It's already attached to a permanent magnet generator I made. I made the generator about 5 years ago, so I must admit it's not the best of designs! It does produce some power though - peak was 40W into a 12v lead acid battery in that video.

I do fancy to make a wind turbine some day (when I finish my 100's other projects) and generator from wheel hub something like http://www.otherpower.com/otherpower_wind.shtml
It seems like it's quite good generator thou

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Originally Posted by wiatroda

I do fancy to make a wind turbine some day (when I finish my 100's other projects) and generator from wheel hub something like http://www.otherpower.com/otherpower_wind.shtml
It seems like it's quite good generator thou

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The generator in my small wind turbine is based on this one:

http://www.otherpower.com/woodax.html

My bigger wind turbine is similar to the standard 'wheel hub' design. I machined the hub from 120mm steel bar and shaft from 80mm steel bar myself though to get higher accuracy for the magnet rotor disks and keep the weight down, this video shows it in the pictures at the end:

http://www.youtube.com/user/Jonbliss...27/R8eNm4cQzqI

Superb !!!
Waiting to see a turbine in action