Making small GRP Wind turbine blades

[Jonathan]

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:







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...

[Jonathan]

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







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?

[wiatroda]

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?

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

[Jonathan]

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

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?

[wiatroda]

Where's the best place to get it?

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).

[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.

[Jonathan]

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

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?

[FatFreddie]

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.

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.

[Jonathan]

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

Yes I was going to do exactly that.

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

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.

[FatFreddie]

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.

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.