Misc. 10' Wind Turbine Questions

[arwenvaughan]

I am working on the 10 foot wind turbine in the Homebrew Wind Power book and have another set of questions. Some of these may be a bit detailed but I figure I should make sure to get things right so I can make the best turbine possible. Thanks in advance for any responses.

1. The book calls for 1 strand of #17 at 140 turns for the winding of the stator (48 volt). I am pretty sure we used 16 gauge wire and some other number of turns at the sustainable living fair workshop last year? I have both gauges of wire and was not sure which I should use. Have you guys found better numbers for this since publishing the book?
   
2. I'm going to be starting the stator soon and had a few questions. What kind of fiberglass mat/cloth (for the stator) do you tend to order from US Composites ... there are so many different kinds? Should I just order the cheapest stuff like the 4oz E glass? Or, is there a better weave, thickness, etc? Also, what thickness of fiberglass tape is best for connecting the copper windings (2 inch ok)?
   
3. I am using ATH and 1/4" chopped strand for filler. What ratios of these fillers would you recommend using on the stator and magnet rotors. The book does not really say exactly, but I bet you guys have some ideas on this.
   
4. Were do you get the plastic / pvc sheets that you used to build the stator mold? I was thinking of building one out of plastic as opposed to baltic birch plywood because it seems that it would be much better at releasing the mold. Is that something you can find in Denver or should I order it online?
   
5. Have you ever used non-wood blades. I am making one turbine for a friend in Texas and he thinks the humidity will destroy the cedar blades. What fiberglass blades would you recommend? Or, what would you do to protect the cedar blades in this type of environment?
   
   

P.S. There is a typo on page 135, second paragraph, third line. "There are are plenty of other ways...".

Thanks again for everything!!!

Arwen

[Todd a]

Wood blades should be fine.  If moister is a question then coat the blades with a good marine apoxy.

Likely they figured the thinner wire was plenty for a 10' turbine and figured they could get more turns instead with the slightly smaller wire (just a guess though).

Most of the time the filler is about a 50/50 mix, but a lot depends on how fine the glass and chop is and what the cosistancy of the resin is.

I'm not sure what the plastic is they are using, but it might be a pollystiryne that is used for lots of hobby stuff and comes in different thicknesses.  A local hobby shop carries sheets, but they are small ones like 8"x10" in white.  I know they also use clear sheets for vacume formed molds and would likely only need a heat gun or an oven to make.  These are used for those impossible to cut open packages at the store.

[scallywagard]

I just use a good grade of plywood for the stator mold and then use a car wax to greese it all up so that nothing sticks. It works great. A good idea is to greese the whole mold inside and out with the wax, then when it is tightened down and starts to run everywhere it can be easy to clean later.

              Good luck and work fast

                    Greg

[arwenvaughan]

Thanks Todd for the response. I think I will try the wood blades with just the lindseed oil and see what happens. I'll add the marine apoxy at the first signs of a problem. Also, I'll try 50/50 on the resin and filler. I think that is what we did at the workshop (I should have taken better notes).

Cheers,

[arwenvaughan]

Cool, thanks for the tip. I'll try the baltic birch plywood since it is cheap and see how it goes. I went ahead and ordered some release mold wax and spray from US Composites so I imagine that should work pretty good.

Cheers,

[ADMIN]

Thanks on the typo! 4 people editing, including 2 PhDs, and we all failed to catch it.

More below -- ADMIN

   1. The book calls for 1 strand of #17 at 140 turns for the winding of the stator (48 volt). I am pretty sure we used 16 gauge wire and some other number of turns at the sustainable living fair workshop last year? I have both gauges of wire and was not sure which I should use. Have you guys found better numbers for this since publishing the book?

Nope, we haven't changed anything (if we do change ANYTHING about the 10 footer, it'll be announced in our book's blog at http://www.homebrewwind.com  )-- just note the difference between the regular and heavy duty stators (and the different magnets). I can't remember, but I bet we didn't have  #17 for the seminar, and used the other wire with an adjustment to the # of turns and the air gap.

   2. I'm going to be starting the stator soon and had a few questions. What kind of fiberglass mat/cloth (for the stator) do you tend to order from US Composites ... there are so many different kinds? Should I just order the cheapest stuff like the 4oz E glass? Or, is there a better weave, thickness, etc?

No preference here...we often get it from the local auto parts store too.

2.1 Also, what thickness of fiberglass tape is best for connecting the copper windings (2 inch ok)?

We usually use strips of the same fiberglass mat used for the stator.

   3. I am using ATH and 1/4" chopped strand for filler. What ratios of these fillers would you recommend using on the stator and magnet rotors. The book does not really say exactly, but I bet you guys have some ideas on this.

50:50 of (total) fillers to resin (page 156)

   4. Were do you get the plastic / pvc sheets that you used to build the stator mold? I was thinking of building one out of plastic as opposed to baltic birch plywood because it seems that it would be much better at releasing the mold. Is that something you can find in Denver or should I order it online?

I THINK we got it at Fort Collins Plastics. Should be very easy to find in Denver.

   5. Have you ever used non-wood blades. I am making one turbine for a friend in Texas and he thinks the humidity will destroy the cedar blades. What fiberglass blades would you recommend? Or, what would you do to protect the cedar blades in this type of environment?

You could try top-notch, expensive  brand automotive primer and 2-part enamel on wood. Remember if you get paint cracks, the paint will do more harm than good. All the Chinese fiberglass blades we've seen have been REALLY rough and crude....sometimes amazingly bad. They also weigh 4 times what cedar blades do, so watch for bearing wear. And there are many stories about water penetration and failure of fiberglass...see "African Wind Power" (before ARE took over their blade warrenty)

Thanks for your patience -- I've been out of the office all week and hadn't checked the board until tonite (burning the midnight / weekend oil here).

DAN F

[imsmooth]

Go to my photo diary at http://www.mindchallenger.com/wind

There I take Cedar blades and coat them with two part epoxy.  They are very strong and durable.  After the coats with epoxy finish them with auto clear coat acrylic spray.  I am told you can get up to 10 years of UV protection with this.

[Todd a]

The only thing I do not really care for with the linseed oil is the fact that you are adding more maintenance.  They need to be coated about every 6-12 months.  A good marine epoxy, even a thin coat should last years and even though it does add a little more weight to the blades it is typically smoother.

[arwenvaughan]

Thanks Dan! That is everything I needed to know. I just ordered everything for the stator and rotors. I'll let you know how it goes.