PVC Gutter Blade Pics

[CG]

I have had these blades on test for about a year now and they have stood up to some high winds. For UK users the guttering is standard 112mm from B&Q and they cost less than 50 pence each.

The guttering is cut into half metre lengths and each length is then cut in half length ways. I designed the shape of the blades on an old Acorn computer using Draw. I then printed it out and stuck the drawing to the back of blade blank. I then cut out my first blade which was the profile. It was difficult getting the paper to stick to the PVC and I have not found a white pen to draw round the profile. It's then just a case of sandpapering the edges.

I haven't found an alternator to put the blades on, so I have used front wheel cycle hubs, with the blades on the front flange and weights on the back flange. On the rotor on the mast the weight is about 2.5lbs, I don't know what this would mean in electical output, but I am sure somebody can gives us an idea in watts.
The diametre swept is about 1.1 metres.

The mast is only about 7 foot high and is shelter by the house, garage and  hedges, but when the wind gets into certain dirctions, e.g. NW, the blades turn very fast in moderate winds. Since I have put root reinforcers on the blades I have never had a blade split.








These are the profiles with two blades below.










The blads on this rotor only have one root reinforcer on the back, but it cost so little in time and money to increase the thickness by 50% if you put another reinforcer on the front as well.

[Shadow]

Those are very nice looking blades!  Do they work well?..Start easy?

[CG]

I can't add much more about their effiency, the mast is very low, and while I am in a rural location with fields to the front of my property, the mast is quite sheltered. The blades have never been connected to a generator, so the only work they have done is turning the weights, which is not quite the same as a generator.

But they are quite easy to make, and if anybody has a small electric motor lying around doing nothing it would not take long to knock something together, I don't think it would be an entire waste of time. They certainly turn very fast and have stood up to some strong winds.

[Jon Miller]

Hi there I really like the idea of 'B&Q Blades' and think that these make a good use of a cheap material.  If you wouldnt mind could you send me a copy of the drawings that you used for making thoses blades?  Also what part of the UK do you live in i am down in kent near Folkstone?  Also could i have your email address as i would like to ask some more questions?

Again the blades look great.

.

[IntegEner]

Thin blades like this deserve more attention and emphasis because they refute all the "blades must be like aircraft wings" tomfoolery that has dogged wind energy. Trouble is that the sharp leading edges introduced thereby have a problem of their own and sometimes create a "braking" (flow separation) effect just when it isn't wanted. Somehow the benefits should be retained and it is hypothesized that adding some kind of radius of curvature to the leading edges might solve all these problems at once. Such a feature would also lend some necessary bending strength at the roots.

I really like the thinness. I'll bet his blades are quiet also or at least can be made quiet when loaded down.

I imagine "gutter" refers to PVC pipe of some wide diameter or other.

The Knucks

www.integener.com

[IntegEner]

I shouldn't say "tomfoolery". I should say "restrictive dogma" instead.

"Knucksosorry"

www.integener.com

[Shadow]

I would be interested in the plans for these as well. Can you email them?..Thanks

[CG]

I am not too hot on using this board, so I'll answer all the questions here if you all don't mind.

First, I do almost all of my web stuff on a computer in a public library, the post was made with the aid of my neighbour's digital camera, computer and knowledge of html postings and Windows software, I don't like to trouble him too often.

I will try and get my email address to whoever wants it, but expect communications to be a bit erratic, I have to cycle into town and if it's raining, well, that's a day missed.

There are no plans as such, just a drawing. But this drawing was done on a non PC compatable computer, an Acorn, so getting plans would mean printing it off and scanning it into a Windows machine. But, really this is not neccessary, as you will see if I explain why I made the blades.

The blade are made of what I said they where made of -  PVC guttering. Most people on the board want to make what I call large turbines, this it quite understandable as you get more bangs for bucks the larger you can make your wind turbine. So most plastic blades seem to be made from pipe which has a thicker wall. I am more interested in turbines about the size of a Rutland 913, because with me it's a hobby and not a neccessity, I am on mains electicity. The blades I have made are about the length of a Rutland, and I would not advise anybody to go much larger with this type of guttering.

All blades are a compromise between torque and tip speed, and depending on the average wind strength in your area one will win over the other. From what I have seen on the board, and I haven't seen it all, most people who use guttering do not seem to think of shaping it much - and until my blades are properly tested they may have a very good reason doing this. But if you have a wide gutter blade at the tip you will have high wind resistance against the leading edge and slow the blade down. If you shape it the camber of the gutter acts like twisting a carved wooden blade, until at the tip it is almost edge on to the direction it is travelling. And if you sand down the last three or four inches on the front it can be quite thin but with still a slight curve on the back.

I am not an engineer and my blades were not computer designed. They were computer drawn to a shape that I thought seem about right (I know I used the term designed in the posting, but that was because the software I used is called Draw and it may have got a bit confusing). What I am trying to say is that you all have a rough idea of the blade shape I arrived at, and you can adapt it to suit yourselves, I don't know the gutter size in the U.S.A., I tried to find it but without success, for all I know diffent states have different building regs., so it's best to just use a design that you have made youself, if I can do it anybody can, and I will always help if I can, just bear in mind that my response may sometimes be a litle slow.

I've only got 6 minutes to go before I am logged off and I will lose this posting, so I will post now as I think you all have enough to be getting on with. I really do hope some will try to make some blades of this type, I think the are great for beginners.

[IntegEner]

To Jon Miller (separate e-mail message also), Shadow, and even CG, there is some that can be said about exact dimensions rather than just approximations. "Guttering" must be roof rain gutters, something in round PVC I haven't seen. But large diameter PVC pipe is easy to find here and it can be cut down the middle lengthwise to obtain about the same thing, I imagine. The concept in airflow is just to change the direction of the apparent wind seen by the moving blades from the incident (or "attack" angle) to an angle of zero, that is, in the same direction as the flat plane of the rotor. The incident angle of the apparent wind is equal to the arctangent of the actual wind velocity divided by the velocity of the moving blade at a particular location along its length. At the center of the hub the blade has no forward motion and so this comes out to 90 degrees. The leading edge must accordingly point straight ahead and the blade must have its largest chord here, an entire one fourth of the way around the wall of the PVC pipe. At the blade tips (a decision must be made about some TSR for its operation, let's say for a small turbine a value of two might be well and good and, in fact, be exceptionally fast) then the arctangent of the inverse of two or one half is 26.5 degrees and the leading edge must point to a direction 26.5 degrees off the plane of the rotor toward the wind. This is a smaller chord equal to 26.5/360 or 7.4% of the way around the wall of the PVC pipe. Measured with a tape for an 8 inch diameter PVC pipe this comes to about one and 7/8 inches blade width. The values in between the root and the tip can be found in a similar way, taking the blade velocities at each point as a fraction of the TSR of 2.

There is more. This results in a trailing edge that "points" the deflected wind to an angle of zero, as mentioned above. It is also possible to deflect it to some other angle. Under a heavy load requiring lots of torque, it may help to have the trailing edge point the deflected wind to an angle that is slightly upwind. This is because there is lots of wind in between the blades that must be deflected as well and to deflect some of the wind more than necessary helps deflect all of it to a zero angle (essentially stopped in forward motion). Turning the rudder of a ship greater than the angle of the change in direction is needed to get the whole ship to change course. But this, again, requires a load being applied.

As mentioned earlier, this still doesn't solve the problem of the leading edge causing flow separation at incident flow angles outside of the designed angle at the designed TSR (two in this case). It seems to me that this can be fixed if someone wishes to just take some aluminum sheet metal of the same length as the blades and bend it to some diameter of curvature, say 3/8ths of an inch, and slipping it over the leading edges where it can be fastened by glue, perhaps. The leading edges are no longer as sharp but performance will normally improve anyway. Word of honor.

I can be of help in this matter because I have been doing some bending of aluminum sheet metal in such a way for other purposes. My website is www.integener.com and contact is welcomed.

"The Knucks" at www.integener.com

[CG]

I'm guessing the you are in the U.S., if you are it answers a question for me. When I was looking for data about PVC guttering in the States I couldn't find a thing, I just thought I was looking in the wrong places.

It's funny how we take things for granted, here in the UK nearly all guttering is PVC, it's light, durable, and makes pretty good blades for small wind turbines. If you go to www.screwfix.com (that's an online DIY store here, not an online brothel)you will be able to see what I am talking about.

I always wondered why PVC pipe was always being used. Guttering is only about 1mm thick so that prohibits its use on large blades, but it is very easy to work.

Perhaps the people at otherpower could import some and cut up some blanks. If they did some research into the best blade shape they could print it on the blanks, and all people would have to do is cut it out. There, that's another fortune made for them.

I'm afraid it will take me about a month to work out the points you have made in your comment, but I am sure you are right. I'm going to take another look at you web site and I only have 18 mins left on this computer, must go.

[IntegEner]

Keep some interest in this, since it has potential to become popular. On the IntegEner-W website look at the Home Links and Projects page and find the little graphic of the "Bent Air Law" showing the incident angle, alpha, of the apparent wind on the blade. This angle must be the same as the leading edge angle of the "guttering" blades. Not very complex. It naturally must vary up and down the blade length. We have ordered and are now assembling from kits small axial flux generators for our two wind devices. The thin blades have implications for improvements in wind energy in general.

AVC, Tehachapi, www.integener.com

[titch21163]

Hi i like the look of the blades would it be possable to email mw a drawing or mesurments please as this will be my first atempt at building a wind turbine but the wife is not so keen but like i said to her if she was in front of it there would be plenty of wind. ha ha many thanks titch21163.