65MPH takes it's toll

[Marck]

Last night we had 65MPH winds come through, Here's what I woke to this morning.

So my vanes made from 3" PVC lasted about 6 months.

Guess I'll have to decide how I am going to make new ones. PVC, Wood... not sure yet, Suggestions welcome

[coldspot]

WOW, Bummer!

Do you think that they hit the tower?

[phil b]

Good straight grained wood seems to be preferred for blades here.

I have lost 3 sets of wooden blades to high winds myself. The 4th set were also carved from wood. Then, I put 3 layers of very thin fiberglass cloth on the blades afterwards. Fiberglassing the blades adds a lot more work, but I think now it's worth it. So far, they have lasted through numerious episodes of 65+ mph winds. This morning I saw 48 mph with gusts. No problems. Some of the files are in my diary. Hope this helps.

Phil

[RobC]

A good furling system will protect you from wind speeds much higher than that and its not that hard to do. It's the only thing that saves my system from self destructing. RobC

[hvirtane]

I think that the main

problem was the furling system.

You also might try

to make the blades

of wood.

If you want to make them a very

easy way, you might try an

unusual method, I've developed

with my friends. Please see

my recent diary:

http://www.fieldlines.com/story/2005/12/29/205319/65

- Hannu

[IntegEner]

The alternative suggested here that also applies to making your blades lengthier is to use the engineering technique of truss design for strength against the strong bending moments. It is a wonder that many more such blades and even those made of wood don't break at their roots trying to stop fearsome winds. Trusses, as in bridge trusses, means a doubled framework. See below:





If you try it with doubled PVC blades connected together like this with some bracing somehow between them, make up a second set for us here. You might try 4 inch but 3 inch would be OK as well. We have a nice 15 foot tall wooden tower waiting for some wind device or other to be placed on it. The winds here are also quite strong on occasion.

Anthony Chessick

IntegEner-W

www.integener.com

[IntegEner]

As a postscript, that appears to be three turbines mounted on one tower! Good work. The above comment also applies to the question of PVC pipe blades stalling when loaded down. If doubled as suggested and offset an inch on the leading edges of the pair - the rear blade ahead of the front blade - the wind is less likely to lose the Coanda Effect and stall as the channel between the blades captures it for deflection even when it might otherwise separate and uselessly head straight downwind. Others have mentioned the issue of stalling caused by the alternator load.

Anthony C.

www.integener.com

[Amptramp]

Howdy Marck,

PVC is a great way to make rotor blades rapidly. they are good for medium term testing, but their lifespan is very limited.

My own experience, in this very windy area, is that these blades will last from 4 to 10 months.

I tried strengthening them by stacking 2 more levels of blade material behind the rotor. The finished product looked very much like the leaf springs of a car. In addition, I added a diagonal brace that went from the rear of the 3/4 inch rotor hub to a point that was 70% of the blade's length from the hub's periphery.

This extended the lifespan of the rotor to 18 months.

Eventually the 1.8 metre rotor began failing again. As the tips would 'flutter' at high speeds, they were prone to breakage.

The worst failure mode could be seen at the roots of the blades where cracks would form.

Given time, these would proceed across the blade's width and cause spectacular failures during storms.

My 'record' so far for 'blade hurling', is 210 metres. Not bad eh?

Sometimes, it can take a while to find all the pieces    .

To bring things up to date, I replaced these ill fated blades with Aluminium ones. They are 2 years old now, and functioning perfectly.

They have survived storms that have torn roofs off houses, so I have high hopes for these   .

Hope this helps.

Cheers,

Steve  Mc Amptramp.