Fiberglass blades

[Make Cop]

What do you think about making blades like this?

http://www.warlock.com.au/10kwblades-abstract.htm

[Rob Beckers]

It's an interesting way to make blades!
For just a few blades it should work, for larger numbers a mold would be better. By the way, in DIY composite airplane construction it is common to shape things from rigid foam and then glass them. That could be used too for making fiberglass blades. The process would be more like shaping wooden blades and not involve steel or welding.

He's using carbon fiber cloth for the outer layer. I always thought that carbon fiber required vacuum bagging (or some other form of pressure) and high temperatures to cure the resin. Seems that's not correct?

-RoB-

[Peter Klaassen]

Those are nice looking blades. Would they be ok if there were large temperature changes? The contraction/ expansion rates for fibreglass vs. steel might cause a separation between the foam fibreglass and steel. A Canadian climate has a 60 degree temperature range, possibly more. I wonder if that could make a difference to the life of the blade.
Pete

[Rob Beckers]

For what it's worth (I'm no mechanical engineer): The epoxy-fiberglass blades we use on the 6kW Scirocco wind turbine have large hollow aluminum inserts at the blade roots. The inserts are the mounting flanges for the blades (Actually, large slewing rings, or bearings, bolt onto the blades since they are variable pitch). Aluminum has large thermal expansion/contraction, while fiberglass has almost none. Yet, this combination holds up just fine in temperatures of -35 ... +40C.

-RoB-

[Martin Gray]

I've been building a set of these blades. They have a steel spar, with metal profiles welded every 6". The profiles are NACA 4412.
Then they are filled with polyurethane foam insulation and sanded down to the profiles.

The next job will be fibreglassing with epoxy resin.

Here's a pic of what I have so far.

Martin.

[Rob Beckers]

Hi Martin,

Are you the one from the "warlock" page that was referenced above? The construction method you're using looks to be the same. Awesome blades! I believe that with a steel core they will be very, very strong, and those profile stations between foam make it easy to follow a precise blade profile. My only concern would be if moisture ever got in, and cause the steel to rust (so it swells and pops the fiberglass). Probably not likely with them being embedded in PU and fiberglass.

Please keep us posted!

-RoB-

[Martin Gray]

Hi Rob,
I did follow the construction methods from Warlock's site. In hind site, it's a whole lot more work than carving from wood. (especially with having a carpentry background) But the design looked intriguing.

Martin.