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BarkyJ
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Posted: 09 June 2018 at 4:22pm | IP Logged Quote BarkyJ

Hi All,

So I have some questions.

In so many videos I am seeing on the net, PCV blades are cut with the leading edge being closest to the wind and away from the hub (they are mounted on the trailing edge being in line with the axis...), which seems opposite to drawings, and also how the GOE222 blades are mounted.

So I am confused.

Why is it that PCV blades seem to be mounted the opposite way to aerofoils?

Is it because that is the only way they can really be mounted?

This one for example, turns anticlockwise (ignore that fact), the leading edge is towards the wind, and the trailing edge is mounted onto the hub and in line with the axis.
https://www.youtube.com/watch?v=6ZTVeFh7-0Q



Compared to say the GOE222 blades which get mounts so the leading edge is also towards the wind, but the leading edge is in line with the axis, and the trailing edge is behind the mounting point on the hub.



Not wanting to get technical too much here as I am not schooled up in blades etc to a high level. Dad was over this afternoon and we were discussing the blades, as I started cutting my PCV blades out, and it just struck us as being 'interesting'.

We can only assume its due to the fact that PVC pipe blades need to be mounted and the only real way to do that is by mounting them on their trailing edge...

Edited by BarkyJ on 09 June 2018 at 4:25pm



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Warpspeed
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Posted: 10 June 2018 at 8:45am | IP Logged Quote Warpspeed

Don't know the answer to that, but it may be a reasonable argument for some scale model back to back testing.

Seriously, how about putting together a small wind tunnel ?
Some pretty basic instrumentation might tell you a lot.




Edited by Warpspeed on 10 June 2018 at 9:32am


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brucedownunder2
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Posted: 10 June 2018 at 9:44am | IP Logged Quote brucedownunder2





This is an old pic of my plastic blades . They were good ,I suppose I could say that ,not excellant ,but bloody strong as a battleship . made of 300mm chemical resistant plastic pipe -some fancy upvc or something that dosen,t break easily ???.
I think it was 12mm or maybe 16mm thick grey stuff .

Anyhow , they are fairly hard to carve ,have to use very sharp grinding tool discs and leather gloves ..

storm hit mine and one hit the tower ,smashing a piece off the tip ,she got out of balance then and broke off at the hub ,.

yours look as if they are carved the wrong way ,hard to tell from photgraphs.

mine were big buggers,a bit noisy,but turned the F&P very easy. the main bitch with F&P thick wire stators is the groaning noise they make getting up to speed and coming down from speed,,forever annoying for your neighbours.. thats a dual up there.

Bruce

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BarkyJ
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Posted: 10 June 2018 at 9:54pm | IP Logged Quote BarkyJ

Hi Bruce

Quote:
yours look as if they are carved the wrong way ,hard to tell from photgraphs.


I haven't posted any photos of mine yet, images above are examples off the net.

You don't happen to have a picture that's closer up do you? Very hard to see any detail, or even which way the blades are mounted. Forum scaling of imagines certainly doesn't help either.

I cut 3 blades out this weekend and started sculpting them today, so I would be very interested in seeing yours up closer if you have the images, before I get too far in.

The pipe I am using is 630mm diameter, 16mm thick wall PCV which is also grey, its mains stormwater pipe. Very strong and heavy stuff. Cuts nicely with a power plane and a jig saw with the right blade.

Ill posts some pics in the next post.
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BarkyJ
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Posted: 10 June 2018 at 10:00pm | IP Logged Quote BarkyJ

Very rough cuts at the moment.
Cut 3 blades out, but only started dressing 2 of them so far.





If you look at Glenn's build (http://www.thebackshed.com/Windmill/articles/GlennL.asp), his are also mounted the same way as described above, where they are bolted to the hub with the trailing edge, as opposed to the leading edge. Which is giving me the impression this is really the only way you can mount them.

So I would love to see photos of pipe blades being mounted.
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brucedownunder2
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Posted: 11 June 2018 at 7:18am | IP Logged Quote brucedownunder2



Barkley, yes, your blades will fit the bill ,just fine .

I cut mine sort of across the length of the pipe , hard to describe. sort of not straight along the pipe,but a little bit angled (length wise). your profile is just like mine , it should start early and in light breeze.
Beware ,the rotor will hum a bit ,depending on the rpm ,sort of disappears the faster it goes.

I'll search for any pic,s of my carving ,but I can,t remember taking any?.

Bruce

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BarkyJ
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Posted: 11 June 2018 at 7:57am | IP Logged Quote BarkyJ

Thanks Bruce

Yeah mine are not straight down the pipe either. It ended up being that the leading edge is somewhat straight down the pipe, but the trailing edge is at about a 3 degree angle, as that is what was intended to be mounted on as per all the other PVC builds I have seen. So this gives a little bit of twist.

Now I just need to shape them a bit more, and sort out the tips, and figure out the mounting.

If you don't have any pics of the carving, if you do at least have one of how they are mounted, that would be a big help.

Are yours mounted on the trailing edge like the other PVC builds, or are yours somehow mounted on the leading edge?

My nickname is 'Barky' too, play on my last name. No 'l' or 'e' in it ;) I won't hold it against you though, haha.

Thanks again.

James
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BarkyJ
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Posted: 11 June 2018 at 7:58am | IP Logged Quote BarkyJ

Oh, and it will be interesting to see if these rotors do hum or not.
I am using the copper 36 pole stators with black rotors, so essentially no cogging etc.
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kalidupakid
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Posted: 20 October 2018 at 3:25pm | IP Logged Quote kalidupakid

Hi All I have a F&P 36 pole unit, and was thinking about blades, from the few days on back shed I think I can use some 6 inch 40s water pipe I have, but I see that a lot of people on the web say to use 8 inch pipe, Im at an age when I cannot be bothered with complicated formula, I just want to give something a try,will 8 inch pipe make a vast difference, I was thinking about using something like a 2.4 meter mill. any information would be fantastic, Im thinking of running the F&P at 24 volts :- John
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brucedownunder2
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Posted: 20 October 2018 at 5:02pm | IP Logged Quote brucedownunder2

Hi John ,

Stick with what Barkley has described in the previous posts.. His look like the best I've seen ,apart from those goe222 blades that Phill sells.

I found a couple of problems with the plastic blades, they can distort ,sort of taking on a bend while carving them . One of mine had a bend in it ,I tried all sorts of straightening tricks, but she just kept her bend.

another thing is ,they might be a bit noisy with the f&P stators/Rotors as they pick up rpm and then when they come down off a high RPM,for some reason. that may upset your neighbour ,amazing how sound like this travels on a still night .

Mine hit the tower and smashed one blade ,so they are in want of re-carving now.

a good carving tool is the wood working carving tool ,from the wood carving people at around $60. very good ,but a bit dangerous, you use a 4 inch angle grinder and thick leather gloves.

have fun.

Bruce

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kalidupakid
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Posted: 20 October 2018 at 6:53pm | IP Logged Quote kalidupakid

Thanks Bruce. I live in a rural area so Ill call on some people who may have a bit of 12 inch pipe doing nothing but waiting for me :-John
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