Just because we had to know..

[TomW]

When I'm not spending my time disrupting the smooth flow of dissenting opinions here on OtherPower I actually do get in some wind power related testing and experimenting. Heres the latest unsuccessful skirmish using 4 inch cedar lap siding:

Thats 4 inch cedar lap siding mounted at 23 degrees to the hub with a bit of rounding on the leading edge. No taper and 3 feet per blade and about 6.5 feet total prop diameter.

While it spins in a very light breeze it is another blade setup that lacks top end for charging.

Once again this is actually my buddy Lanes thing. He had been looking at a Bergey 1KW mill [XL.1 I think] and he was curious about its apparent lack of twist. He tossed these on one of my old JerryBlade hubs to see if it worked at all. And, like I mentioned, they work at some level but have low and limited rpm.

Can anyone explain just how Bergey makes those blades work? I have never seen them myself yet but Lane says they have no twist and what looks to be a constant profile.

Cheers.

TomW

[troy]

Glad to know you haven't been entirely sucked into the vortex of board politics.

In a driven rotor (as opposed to a propeller) lack of twist will with make the rotor hard to start with a good top end, or poor at the top end with good starting characteristics.  Or they can split the difference and get so so starting with so so top end, and definitely not as good as a set of twisted blades.

Unless of course it's some variable pitch hub or one of those magic blades that are thin in just the right places so that as wind speed goes up, they deform into a better attitude.

Good luck and especially, keep having fun.

troy

[funkeytut42211]

Always love to see a experment. I think the big problem with this blade is the 23 degree angle more than anything. Jerrys blades are now something in the area of half that and they work really well. 23 degree is great for start up but have too much drag to go very fast.

[Norm]

   Do you suppose you could use a reinforcing metal strap the length of each blade about 3" wide and 3/16 thick or whatever it takes, where you could twist the strap enough where it would stay twisted at the proper angle when you screwed or bolted it to the wood siding? (Actually there are a few good woodworkers out there that know how to twist and bend wood like it were plastic!) I've always thought myself that it was a lot of work to just shape a prop, let alone put a twist in it as you go along, It wouldn't have to be so thick in the first place, if you could twist it afterwards.Norm.

[TomW]

Norm;

I looked into steam bending and it might be a way to go except for the little fact that softwoods do not accept steam bending according to my research.

Tests on some pine I had on hand show that for boards that thickness about a half hour in live steam softens them enough to get a nice twist. All well and good. However, after sitting awhile after they dry the boards straighten back to near the original shape.

I did not really expect these to actually work and it was just more "what if..?" stuff.

One day I need to just get something that works for my crazy wind situation. Here I think that means a VAWT and thats my current project to get a clone of the picoturbine crossflow Vawt working using a couple tape drive motors as top and bottom bearings.

Cheers.

TomW

[Norm]

 The wood has to be clamped in position and slightly overtwisted (trial and error to determine the correct amount, just like everything else in this crazy, but fun game!)then it has to remain clamped until dry, I suppose, to be truthful I'm just drawing a logical conclusion from what I've read no experience except from watching some of my plywood squares that I had get wet and seen them twist into all kinds of unwanted shapes! (:>)  Norm.