Its how we modified those blades to give more power and less noise. We did loose some low wind power, but gained a lot more at higher wind speeds.
http://www.thebackshed.com/Windmill/articles/ChineseBlades.asp
I never want to modify a set of fibreglass blades again though, I've discovered I'm alergic to fibreglass fibres, come out in a rash. Get itchy just thinking about the stuff!
Glenn
I suspect that if these are two half shells stuck together, bringing the TE to a knife edge may remove most of the bond strength from the TE so it may have to be some sort of compromise.
Flux[ Parent ]
It is not the length of the trailing edge I have radiused, the blade tip. In face the blade airfoil profile is the best part of the whole thing. They looked as if they had just been parted off from a long lenth, the tips were square and rough. So I puy a small radius about 5mm just on the edges of the tips. The appearance of the blade is a press moulding, they are solid and very dense where two mouldings would have a void and on all the blades both ends are the same, solid and you can see where the fibres have been cut through.
As for epoxy, I worked in the marine industry for over ten years, and it is only some of the later epoxy resins that are impervious to water. (and it's a pig to spray) Most GRP hulls are made from Sprayed chopped strand mat and polyester. The bigger huls have woven roving and tri axial reinforcing.
Hope this clears up a few points.
Brian. [ Parent ]
Having the tip knife-edged throws the tip vortex farther out. Equivalently, the high pressure air on the windward side of the blade would like to run around the tip and fill in the low pressure area behind it - depowering both sides of the last few inches of the blade. If the tip is rounded it can do this. If it is knife-edged the air running off the front side ends up flying outward. By the time it gets turned around the blade has moved on. So the end of the blade is depowered less with a sharp edge.[ Parent ]
