From aluminum tube to blades.

[Yianie123.]

Does anyone have any experience making large aluminum blades from an aluminum thin wall pipe?  Please share your experiences and photos.  Thank you..

[dnix71]

Aluminum will stress fracture. Even aircraft aluminum alloyed with magnesium has definite flex lifecycle. Laminated wood is more difficult to fabricate but with proper care will last years and can be shaped easily.

What length blades do you want to make and what is the power output of the mill? What is the climate [freezing/snow/gale winds?].

[Yianie123.]

I live 50 miles east of Chicago, in the snow belt.  I am looking at an 8ft diameter find turbine.

[MattM]

You can always experiment although it's more than likely not to survive long if it's thin enough to flex.  The fatigue basically comes from the mechanical stresses.  The failure point from my experience with sheet metal would point to the attachment point.  Tubes are generally extruded so that material tends to be more stiff and can be brittle.  Ymmv

[Yianie123.]

I am looking at using 8 inch diameter aluminum tube, 1/8 inch thick, approximatly 42 inch long.

[dnix71]

Aluminum expands and contracts a lot with temperature changes, that's one of the reasons it is not used for inside wiring. Buried pipe isn't subject to temperature extremes and aluminum has good corrosion resistance.

If you were going to cast a blade of aluminum, Mercalloy 368 would be the choice. Low iron for stress fracture resistance and no need to anodize.

There are titanium-aluminum alloys available in tube form for making race cars, off-road vehicles and moto-cross bike frames.

https://www.irvansmith.com/scart/5712-aluminum-truss-bar-titanium-series-p-1281.html  Not very expensive. You aren't going to drill into or hammer that flat without some effort, though.

[kitestrings]

you might also check to see what phillm has done on the Back Shed.  He's been doing AL blades for quite some time.  Personally I'm not a big fan of AL blades, but might be okay for something this size.  ~ks