Big wind day here too

[margusten]

Hi,

I've got Big wind day here too.

Amazingly 3m diametre windmill survived. Scrap blades from plywood and PVC mix.

2m diametre windmill didn't, has now only one blade instead of 3:

Furling didn't work. Too long tail probably.

PVC blades blend too much.

Fix was easy cause spare 4 blade was hanging on garage wall.

Tested at summer and working, but not so good as 3 blade.

Blades have some degree offset to avoid hitting the tower.

Also shortened a tail, not seen on this picture.

Let's see how this solution can survive next Big wind day.

BR,

Margus

[SparWeb]

Oof.  Strong winds bring big payoff and big risk, kind-of like the stock markets!

What are PVC blades subjected to when they furl?  If there is an oblique wind-flow over the prop disk, then they change angle of attack twice per revolution.  If the wind is strong enough to cause a flexing stress at the root of the blade, then they may have developed cracks that progressed through the chord until they snapped off.  Also, I'm not sure how stable the PVC blades are against fluttering, which might also be exacerbated in furling.  Try bending that one surviving blade a little, and see if any white spots appear where it's already been over-stressed.  That would tell you if thicker wall pipe is required.

Are you going to make new wood blades for the mill, or are you still going to use PVC?

[KurtJ]

Sorry to hear of you bad luck. just curious..how old were the blades / how long had they been flying? just wondering if there is any way to come up with a rule of thumb on what their life span is and when it is a really good idea to replace the due to increase risk of stress fractures.

[margusten]

Of couse I would like to carve wooden blades. I have even pieces of wood with a few knots collected. Unfortunately I had no time to carve, probably next summer.

PVC blades are much easyer to make. Now we know 1 metre long PVC blades can't survive big winds. These blades were more then 1 year old. Sun and cold can damage them. May be paint can help to survive longer.

My second windmill has 2 metre plywood blades base. Drawings find from this forum.

Too heawy and small wind hitting degree. Didn't work at all. Then added PVC blades and it start to work. Looks awful but working. PVC blades bend in big winds and this can wear them out. Lifetime 2 - 3 years I think.