I cut some PVC blades today.

[DamonHD]

Well, my DIY skills don't even make the 'Damage It Yourself' rating, but I cut myself an extra set of blades from PVC 100mm tubing today for my tiny turbine, taking its blades to 6.  I think that it is spinning up in a slightly lower wind than before.

I've done this today because we have ~9mph winds forecast for tomorrow.

My hand-cut blades are about C- quality and one of them seems to stick back further than the others and is in danger of hitting the pole, so I've crudely put a bit of a forward bend in it.  Quite easy material to cut and work, which is why everyone uses it I guess!

Rgds

Damon

[ghurd]

Speaking for the "I have 100 pounds of PVC sawdust on the floor" guys...

As long as they are balanced, they'll work OK!

How rough is a badger's...?

G-

[DamonHD]

About as rough as my blades!

[feral air]

Never heard "Damage It Yourself" before - I'll have to remember that one. I did some C- work today too, go figure.

If nothing else, at least we're trying.

[Norm]

What do you mean by handcut blades?

...You used a hand saw? or a sabersaw?

I use a handsaw...sabersaw for the rounded ends.

Then to shape the edges, a utility knife, holding

it just right you scrape the edges.

You're right it is easy stuff to cut and work

with!

              ( :>) Norm

[DamonHD]

I cut it with a mixture of tenon saw, hacksaw and scissors, and smoothed it down with some fine sandpaper.

Rgds

Damon

[rippersoftware]

I just got done with a set of PVC blades from that 6" co-extruded stuff.  Has foam in the middle.  Nice and thick.

I use a back saw to cut along the line by angling the saw and leaving some stuff to finish up to.  I use a small rasp and a block plane.  The block plane lets me remove stuff quickly so I can make a sharp trailing edge.

Handtools work great if you have some time and patience.

RipperSoftware

[claude]

I'm a PVC fan as well, and I use an electric saw (the one with a pendular motion). I then use sandpaper to round the edges. My first was made using Gizmo's template available at http://www.thebackshed.com/Windmill/assemblyMini2.asp

Unfortunately it spins backwards. How do you all solve the problem of cutting the right shape and drilling the mounting holes so that it never happens? Are you using a hub to keep the PVC blade angled properly?

Claude

[Norm]

In the case of Gizmo's template if you want it to spin in the opposite direction, you would

just reverse the template...but in the case of using a stepper motor, direction of rotation

shouldn't matter anyway.

   For much larger ones I have use riding mower

blade spindle and used the blade hub for the

blade, it has one center bolt to hold the blade

and the hub onto the shaft, it also has 2

smaller bolts that hold the blade.

  Surely if this can handle something like 6hp.

spinning at couple-three thousand revs., it

should be able to handle a several hundred revs.?

           ( :>) Norm.

[rippersoftware]

I take the rough cut blade and hold the wide root end toward me and the narrow tip out and away from me.

If I want the blades to turn clockwise, then I label the right side of the blade with an L for leading edge and the left side of the blade with a T for trailing edge.

The holes would be drilled on the trailing edge side and then mounted on a hub at the zero, 120, and 240 degree lines on a hub.  Assumming 3 blades.

If your mill needs to spin counterclockwise, then the left side of the blade is the leading edge.

Thed leading edge gets rounded and the trailing edge gets flattened to a nice sharp edge.  Somewhere on www.TheBackShed.com is a really nice picture of PVC blades and their shape at various stages from root to tip.  All of the shaping is done on the back of the curve, what would be the outside of the pipe.

Wish I can find that picture.  Oh well.  The first couple sets takes abit of work, but then you start to see really what you want and after that it is pretty easy.  A block plane makes short order with the shaping and not saw dust.

RipperSoftware

[Capt Slog]

I'm using PVC blades too.

The last set I made, I drilled the mounting holes first and made them 2 inches longer than I needed them.  I put all the blanks together and then drilled a hole at the tip in the excess bit.  I could then fasten all the blade blanks together with these holes and cut them all at the same time.  This means that they have the same shape.

I then use the holes, root and tip, to fasten the blades to a piece of wood that I can hold in the vice.  This makes shaping the trailing edge much easier. When the blade are nearly finished, I cut the excess tips off.  

It isn't perfect though, because the blades can't fit into each other well as they all have the same radius, but it does help.

I also use the craftknife-blade-as-a-scraper technique mentioned above, and I found it gives a really good finish.

One thing I have noticed though, is that however carefully I make the blades to the same shape, they have different weights.  I think this is due to the pipe not being uniform thickness to start with.  I've ended up with 10g between the lightest to heaviest blades.

[ghurd]

Good point.

I used to try to make a set that was perfect. Something somewhere would go wrong.  Making a replacement never worked as well or as easy as I hoped.

Now I make like 10 blades at a time.  If one has the weight too far off, if a hole is drilled in the wrong spot, if whatever, there is an extra waiting to replace it.  Much better luck getting a matching set if they were all made at the same time.

G-

[pepa]

   a little trick i use for marking the cut on pvc pipe to make the blades alike is, to make one blade pattern of each size i use. the trick is to make the pattern a little larger than actual size when finished for a certain dia. pipe. by laying a scrap piece of pipe cut to the width you want on the outside of the pipe and marking both sides then measure the marks and you can figure the amount of extrs to add to the pattern to make it come out the size you want as a finished blade and it will be used to make replacement blades if needed. the actual blade will be smaller than the pattern, but varies with the size of the pipe. use the pattern for marking all the blades you need and they will all be the same. i use a belt sander with heavy grit belts to make the tapered edges and finish with light grit belts. hope this helps, pepa.

[wooferhound]

You do have the Inside of the Pipe Facing Into the wind don't you ?

[DamonHD]

Actually, my tiny turbine works better with the wind blowing from behind the turbine against the curve!

[pepa]

   the inside curve is the front, pepa.

[wooferhound]

I have to say that, your observation is incorrect . . .

[DamonHD]

Tell that to the blades!  B^>

(One reason it works better that way is that the blades still have a slight tendency to hit the mast because they are too bendy, and that doesn't happen with the breeze coming from behind!)

BTW, put up my spare tiny turbine today very close to the house to see how it would fare.  Have not put in full set of blades, nor full electronics yet.

Rgds

Damon