# Wood Prep- wind turbine blades



## andyrose (Sep 20, 2011)

I am refinishing some Jacobs wind turbine blades from the 1940's for reuse in a 2.5 KW off grid system. I was told they are Sitka spruce, but they look like western red cedar to me. Stripping off some old silver paint and using a wire brush in spots. A bit of deep grain, divots, minor bruises. Want to bring out the natural color and not sure what is the best product. There are several types of deck stripper solutions, and various active ingredients. Ixatylic acid I think is one. After cleaning up I will use multiple layers of clearcoat epoxy with a clear tape (LE) on the leading edge. Anyone have experience with this?


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## Stick486 (Jan 4, 2013)

same stuff airplane props are done w/ which is generally an epoxy...

40's vintage prop???...
hope it's integrity is 1A and is featherable...


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## Cherryville Chuck (Sep 28, 2010)

There is no comparison between Sitka spruce and western red cedar. Although both are very low density woods red cedar is red or reddish brown for older or decadent old growth and spruce is white to slightly off white. Spruce has mostly no scent at all once it is really dry, red cedar always smells when you sand down into the grain a bit. I would be surprised if it is cedar. Cedar is extremely prone to separate along growth rings which is why it makes hand split shakes.

Oxalic acid is commonly used in cleaning up weathered wood. It won't strip old finishes off that well from my experience. Scraping and sanding are usaully the best options. I agree with the epoxy solution for the new finish but it may not stop the wood from changing color underneath if it's clear. The large commercial wind turbines either have a brake or the ability to change the blade pitch to neutral in case of extremely strong winds which is what I think Stick was alluding to.


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## Stick486 (Jan 4, 2013)

Cherryville Chuck said:


> The large commercial wind turbines either have a brake or the ability to change the blade pitch to neutral in case of extremely strong winds which is what I think Stick was alluding to.


I was...


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## andyrose (Sep 20, 2011)

Just looked at the three blades and it must be sitka spruce. There are some pretty good divots like 1/4 inch in spots so I will need several layers of epoxy or a wood filler first in those low spots? Also some of the wood grain striations are 1/8 inch deep. I am just wondering how to get a nice smooth finish across the entire surface, like an airplane prop. Guess just a lot of coats or mix it thicker of the first coat or two?


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## furboo (Oct 12, 2015)

Stick486 said:


> same stuff airplane props are done w/ which is generally an epoxy...
> 
> 40's vintage prop???...
> hope it's integrity is 1A and is featherable...


A featherable wood prop? I collect wood props...I need that one!


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## andyrose (Sep 20, 2011)

The Jacobs turbines came with two types o governors that act to twist the blade on a shaft parallel to the blade. The one methods uses three "flyballs" that as the speed increase would pull away from a main hub and simultaneously with a lever arm rotate a center gear that mess with partial gears on each of the three blades. This then rotates the blades out of the wind. The second design, that I have on the one I am working on has a large spring from the center of each blade that join together at the front shaft. As the blades flex in high wind they also rotate. The blades are 7 ft long, and the turbine at top speed is 225 RPM, which is relatively slow as small wind turbines go. IN addition to the clear coat I want to paint a red band around each blade, maybe 6 inches in from the end. As the blade spins, looking from a distance, a red circle shoiuld start to appear indicating rotation speed. With the output of the turbine, I will charge a 24 VDC battery bank (originally this is a 32 V system). Back in the day, 32 volt DC was the system of choice. In fact, I have a near new montgomery ward iron and box, a toaster and an electric drill all at 32 VDC. When the batteries are full, most of th time, the excess goes to a dump load, which is essentially heating got air or water. So I am getting heat from the wind, fun concept, and useful here in Wyoming!


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## Stick486 (Jan 4, 2013)

furboo said:


> A featherable wood prop? I collect wood props...I need that one!


when Andy finds out that he'll need a 3 blade prop 15-20' in dia to get the most from his generator his wood prop may become available...


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## furboo (Oct 12, 2015)

My wife would be thrilled with a 20' prop in the living room >


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## bcfunburst (Jan 14, 2012)

No matter how you treat your wood props; if you want an even colored finish, you will likely have to mix some sawdust with the epoxy when filling divots. THEN before you ad the finish coats, you will need to use a product called Wood Conditioner. You will get a much better even color finish if you follow instructions on the can.


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