P.V.C - Fibre glass hybrid blades?

[gotwind2]

I am considering testing a set of three 4 Ft diameter P.V.C blades with a difference.

I wonder - if I resined some fibre glass matting over the front 'curved' section of the blade.i.e to make a flat tapering front face, as I have tried to illustrate below. If this would increase there efficiency - It would certainly make them stronger in my oppinion.

Thoughts always welcomed - I know wood is best, just experimenting.

[pepa]

it does help and it should keep the blades from flying apart if thet break and also makes them stiffer and protects against the sun. i have made blades to 10' (20'8" dia.) without any problems to date. i sew a sock to fit the blade and epoxy the material to the entire serface of the blade. hope this helps, pepa.

[gotwind2]

Thanks Pepa.

Yes that does help - I was considering using an old rubber inner tubes from a bike as a 'sock' to create the profile, you mentioned epoxy?

I was thinking of using fiberglass matting and polyester resin to encase the whole lot.

Would epoxy be better, and how expensive might it be - I am in the U.K

Thanks

Ben

[pepa]

sorry Ben, i do use fiberglass resen, pepa.

[RP]

I'd be worried about the tension of an innertube deforming the curve of the PVC.  

Another advantage of Pepa's sock method is it leaves room to glue a stiffening spar in there if you wanted to strengthen the blade or a least a "block" at the root to mount it with.  I suppose the fiberglass would protect the PVC from UV as well.

[alancorey]

What problems do differences in the thermal expansion coefficients cause in things like this?  I would think there'd be enough problems in something compact like an axial flux stator, but with something elongated like this it seems like it would bend as it heats and cools.

Just playing devil's advocate, and I used to do a little glassblowing where expansion was critical.  About the only thing that you could join to Pyrex-type glass was platinum, otherwise it would break when it cooled.  Plenty of things broke anyway.

  Alan

[thefinis]

Should not be a problem as the resin is a plastic and so is the pvc so the expansion rates would be close and both have a little give. Biggest problem is UV for both so paint is a good addition.

Finis

[gotwind2]

Thanks for the comments. Appreciated.

R.E: RP's comment

'I'd be worried about the tension of an inner tube deforming the curve of the PVC.'

Not really a problem with a 1/4" wall thickness imho.

My only experience with grp (glass reinforced plastic)was at school building a plywood skateboard deck, with a matted fibre glass coating it had amazing properties, flexed really well without cracking - I still ride it now 20 years on.

Might be worth considering for something R.E related

[luckeydog]

 I have been considering doing an overlay on PVC to stiffen it up

I would love to know if you try it to let us know how well it works.

I have a page describing some of the steps in doing a composite type blade

i think this method would work with PVC

http://www.coloradowindpower.com/page.php?5

[bob golding]

these people are cheap for fibreglass.

http://www.cfsnet.co.uk/

much cheaper than autoparts shops.

cheers

bob golding

[tecker]

 Pvc makes a great core the resin works on the pvc somewhat and you have to set the glass with a form holding the blde to retain it's shape.

[Mary B]

before putting the resin on how about filling the blade with spray in foam? Should stiffen it considerably but is light weight. Excess is easily trimmed off with a knife. could even run a spar part way down the blade if needed.