Boss's 10 footer update (pics heavy)

[Boss]

Alrighty then
I did a rough sanding on the blades that Kevin Murphy made on a CNC router, They are pretty thin, I hope the wind doesn't tear them up right away.

Looking down from the tip, you can see the curve. Kevin says, he hopes this helps keep them off the tower

He has beautiful curves. Next time I will get him to leave more material to aid in finish sanding

These are very slender blades

Above the blade is up against the last set we made on the CNC machine

I've got the blade held next to one of the six foot blades from the last set


Very artistic, I hope they hold up

again such a lovely shape to work with

I like the Cedar wood, but it isn't nearly as hard or heavy as the douglas fir of the last set  Again this photo shows the curve

Stator clean up, sigh

A couple of the blades together

At the same time as I was sanding on the blades I used a pneumatic orbital sander on the stator to get it flatter. I got a bit carried away with the last finish coat of vinyl-ester resin

I am getting happier with the look and feel of the stator, but I have to say to the newbies, try and get it better to begin with, clean up takes way too long when we're sloppy 

I did the first trimming of the inside circle cutup for the hub with a crappy little auto body rasp. Then I figured out to use a rough sanding disk on a air tool

I don't remember what you call it but there it is the sanding tool

[SparWeb]

I still think they look like albatross wings!

Try to round out that inside corner in photo #8 and make it a smoother contour.  That sharp inside corner could be trouble.

Because of the compound sweep to the blades, I wonder about how they will flex and/or twist when at speed.  How thick are they?

[Boss]

Thanks for the input

They are crazy looking blades

Kind of like this

Notice how little the root is on ours. We wanted as much blade in the wind swept area as we could get.
We have no idea if they will work. Yes it is our guess too that some flexing will occur. Perhaps they'll act like the AirX blades and flutter so much as to slow the blades down, anyway they look very fast and light. Out where the second angle starts the blades are only an inch thick. When they break. that is the place they'll do it. Notice I said "when"

[SparWeb]

Thanks for the input
.....We have no idea if they will work. Yes it is our guess too that some flexing will occur. Perhaps they'll act like the AirX blades and flutter so much as to slow the blades down, anyway they look very fast and light. Out where the second angle starts the blades are only an inch thick. When they break. that is the place they'll do it. Notice I said "when"

Well, yeah, that's exactly what I'm worried about.   Blades that are relatively straight or simply tapered put all of the centrifugal load along a straight line that goes right through the hub.  Loads in that case are closely lined up and no funny flexing happens.  But yours have a lot of changes in direction, meaning the center of gravity of the tip section will make the tip want to line up better with the rest of the blade.  It's a big stress right at that elbow.  The elbow having the change in cross-section as it does, invites a fatigue failure. 

Wood is not largely vulnerable to fatigue, but it is possible to cause an existing split in the grain to "travel".  If there's any load that will open up such a split you can be sure that it will find its way to that elbow area.  It's outside my comfort zone.

Since you have access to a CNC, that elbow (and the corner near the root for that matter) could have been given a generous radius to smooth out the transition.

[Boss]

Well, yeah, that's exactly what I'm worried about.

I hate to see you or anyone worry. Life is too short. Think positive. You make good points, and you got me thinking, this is good. We're going out this morning to work on a WoodMizer bandsaw and try our luck quarter sawing some 100 year old Douglas Fir timbers for the next set of blades. I want to make three by threes this time, so Kevin has more thickness to play with the angle of attack on a broader base.

Meanwhile I have choices, trim the blades I have and stick them back in the wind, dedicate these cute Albatross blades to the wood flooring museum where the CNC machine is, because he is a pilot and likes the design a lot, or put them on our mill and let em rip. Hmmm

The last thing I want to do is worry

[SparWeb]

It tickled a nerve....  I have to ask "what could possibly go wrong?"  sometimes.

[Boss]

It tickled a nerve....  I have to ask "what could possibly go wrong?"  sometimes.

I know I get it, I'm very sensitive to  anything negative since my dad died. I had to tell my brother that he hurt my feelings again when I was showing him the asparagus we have started in our little greenhouse and he said, "you remember that we started hundreds of those and all but one or two died."   
I'm getting the "Why bother syndrome." Except that I can keep trying